Model Boat Mayhem

Dry Dock / Shipyard: Builds & Questions => Steam R&D: => Topic started by: flashtwo on March 05, 2009, 08:58:36 PM

Title: Flash steam plant control.
Post by: flashtwo on March 05, 2009, 08:58:36 PM
Hi,
I've opened this new thread in response to the interest shown (by Proteus and Bunkerbarge et al.) in my flash steam control system, elements of which I have described in other threads.

In 2006 I had some vague idea about building a boiler which didn't fall foul of the Pressure vessel regs. and insurance. I visited the 2006 Warwick Model Exhibition and luckily found Steamboat Phil with his display of flash steam boats, old and new. With Phil's good natured encouragement, off I set to build a "controlled" flash boiler that could sedately power a Windermere launch at a few knots, but not to break any high speed records.

It took two hours to wind the 15 foot x 1/4" copper pipe into a volume about 3" dia. 9" long boiler. That was the easy part. The rest of the story revolves around learning to program PIC controllers, building the Stuart D10 from castings, building the electric pumps and servo-controlled gas valve.

There were many conflicting ideas on how to control a flash boiler - do you control the steam pressure by the pumps or by the gas valve? The PIC controllers were ideally suited for experimenting with the different methods, because, once the controller board was built, the different control methods could be downloaded without having to resort to the soldering iron or lathe.

I've got the stage where I can go from cold (2degC) to engine running at 200RPM in three minutes  using 8 grams of butane/propane, tick-over at 200RPM lightly loaded at 6.5psi, using 1.2grams/min and run at 300RPM heavily loaded at 38psi using 4.5grams/min.

The only control signal I transmit is the engine speed demand signal (the boat will have separate channels for valve gear, drains and rudder control) and the PIC based controller monitors the boiler outlet steam temperature and pressure, gas cylinder pressure and the economiser outlet temperature. The controller then calcualtes the feed water requirement and gas valve servo position.

The speed regulation is purely done on feed water and gas supply, since there is no throttle / regulator between the boiler and the engine. If I set the demand RPM to 400 then the pumps gradually increase the feed flow and the gas valve opens to maintain the steam temperature - the speed then increases and hovers around 385 to 415 RPM.

That's the potted story to start the thread.

Ian

oh, and by the way, surprisingly, you don't bother controlling the steam pressure!
Title: Re: Flash steam plant control.
Post by: kno3 on March 05, 2009, 10:36:55 PM
Pictures?
Title: Re: Flash steam plant control.
Post by: Bunkerbarge on March 06, 2009, 12:22:24 AM
Now that sounds like an interesting process Ian.  By the sound of it the unit works on similar lines to what we used to have on cargo ships as a stand by boiler, which was known as a "Stones" vapour boiler.

You basically pumped water at very high pressure around a coil which formed the furnace into which the burner fired it's flame.  You could raise steam from cold in about two minutes and the units were completely automated.  I remember the water pump needed to be a high pressure pump and they were basically a ceramic piston pump of the same type as is still used nowadays in high presure water washing units.

They were great when they were working OK but if anything went wrong they tended to fail in spectacular fashion!!

Looking forward to some pictures if possible.
Title: Re: Flash steam plant control.
Post by: Circlip on March 06, 2009, 01:50:36 PM
The early "How to" types of model boiler relied on the pump delivering water through a clack with a by-pass to limit the amount and the clack being sealed by the back pressure of "Flashed" steam due to it hitting really "Warm" tubes.  O0

  The "Safety" of this operation as opposed to the more normal Kettle types is that in the event of a failure in the Flash system there is no water flying about and the pressure is released instantly.

   Regards   another Ian.
Title: Re: Flash steam plant control.
Post by: flashtwo on March 06, 2009, 09:11:11 PM
Hi,

Here are a number of photos. they show the boiler with the casing removed and the controller with its developement display unit. The display unit is not installed on the boat and the steam plant can run without it.

I'll shoot some better pics outside in the daylight, since the soot covered boiler tubes seem to absorb all the light!

The complexity of the traditional mechanical controls resides within the software, which is difficult to show as you can quite imagine. A simple line count of the source code is in the region of 20,000 lines, which includes commentary lines and some spacing.

Regarding the term "coil boiler" - the first time I heard the term was at the Ally Pally in January, when a visitor mentioned that he used to work for a comapany that made them.

Ian.
Title: Re: Flash steam plant control.
Post by: flashtwo on March 06, 2009, 09:12:27 PM
Here's the controller photos.

Ian
Title: Re: Flash steam plant control.
Post by: flashtwo on March 08, 2009, 09:24:04 AM
Hi,

I've come to grips with a photoshop package and I have produced some better pictures.

Displayed are:
a)  The gas valve with its servo and the gas cylinder pressure transmitter,
b)  The boiler, economiser, oil separator and D10 engine.
c)  The inside of the boiler casing showing the insulation and expanded metal mesh.

Ian.
Title: Re: Flash steam plant control.
Post by: Bunkerbarge on March 08, 2009, 05:41:40 PM
That's a pretty impressive piece of engineering there.  Very interesting to see you developing such a project and, as you say, translating all the old mechanical processes, which were notoriously unreliable in real life, into software.
Title: Re: Flash steam plant control.
Post by: logoman on March 08, 2009, 09:07:06 PM
lovely to see it again, please keep us updated with the progress.
Title: Re: Flash steam plant control.
Post by: mogogear on March 12, 2009, 12:48:57 AM
As my inexperience with flash steam systems will be obvious...In your system .. is this a closed system that recaptures the "spent " exhaust steam and it's condensate replenishes the "coil" boiler? --Well- I guess it can't since it would contain traces of lubrication oil.

I was thinking of a system similar to refrigeration --except heating to expand-- then power through the engine- then condensate back into liquid form... and start the cycle over again...a weak mind on my part!!

Great engineering job!!
Title: Re: Flash steam plant control.
Post by: BarryM on March 12, 2009, 10:00:07 AM
Mogogear,

You're describing a closed feed system as is common in full-size steam plant  but is seldom practical in model format.

Regards

Barry M
Title: Re: Flash steam plant control.
Post by: SteamboatPhil on March 12, 2009, 10:16:01 AM
Ian's plant is a total loss system, as BaryM has said a closed system in mode form is next to impossible to do and make efficient.
l
Title: Re: Flash steam plant control.
Post by: Bunkerbarge on March 12, 2009, 10:23:16 AM
That's about it Barry.  Modern steam plant be it main propulsion or auxilliary systems always recover and recondense the steam.  Water consumption would be unbelieveable if you didn't and you couldn't make enough feed water to keep up with it!!

To translate this to a model boat though you would have to be considering a condenser unit and all it's associated auxilliaries and controls, not to mention seperating the lube oil system from the steam system.  As the model is never more than about ten minutes from the bank it is a lot easier to simply use the feed water and allow it to exhaust.  Having a feed tank on board can extend the duration to well over an hour, which is beyond most lubricator and seperator tank capacities so most modellers can comfortably work around this and put up with a total loss system.
Title: Re: Flash steam plant control.
Post by: mogogear on March 13, 2009, 05:32:41 AM
Ok.....So Ian... could you pin-point the inlet for water to your tubed boiler? Is it that small solenoid directly in front of boiler ?   I am very well schooled now that you will need a constant flow of water from some where to supply your Coiled volcano ........
Title: Re: Flash steam plant control.
Post by: flashtwo on March 13, 2009, 09:35:19 AM
Hi,

The feed supply will come directly from the lake, through a settler tank to allow any grit to settle out, into a common suction manifold from whence the two electric pumps draw their supply. The pumps have their own non-return valves and deliver to a common boiler supply manifold. One of the pumps is for standby duty.

The route through the boiler is up through the economiser in the stack (the vertical coil where it can pickup to 74degC of temperature), down to a thermocouple pocket,where the economiser outlet temperature is measured, and then into the steam generating tube. The steam exits via a manifold, which houses a safety valve (rarely ever used since the software shuts the gas valve well before high temperatures or pressures are reached), boiler outlet pressure and temperature tapping points and finally the engine steam supply port.

I'm not concerned about mineral build-up in the boiler, since it is continuous "blow-down" with fresh water pumped through the entire single tubed system.

The small silver "solenoid" in front of the boiler is, in fact, the boiler outlet pressure transmitter (Tx) - the long copper tube is to entrain cold condensate to stop the transmitter over-heating. The Tx is ranged 0 to 10Bar and sends an electrical signal to the controller, where it is used for high pressure shut-down and calculating the steam saturation temperature (Tsat ) for the given steam pressure. The Tsat is the actual set point to which the gas valve controls the steam temperature.

I've just finished making the 4.5 inch prop and just about to fit the valve gear and drain valve servos.

Ian.

Title: Re: Flash steam plant control.
Post by: dreadnought72 on March 14, 2009, 11:44:05 AM
I'm extremely impressed - and not least by the use of microprocessors to do the hard work. I'm planning to use a couple of these in my (electric) build, and wouldn't mind hearing more about the programming you've done with them...to my mind, they offer the opportunity to allow for onboard functions and control that'd be difficult to achieve otherwise, and I hope non-programming modellers wouldn't be put off learning another skill, or by the idea of writing programs. (Far easier than programming the VCR, I think!)

Andy
Title: Re: Flash steam plant control.
Post by: flashtwo on March 14, 2009, 12:49:17 PM
Hi Andy,

Thanks for your interest in the software side of the project, since that is the major difference between it and the conventional model boat steam plant.

As I said above, the biggest advantage of using the micro-controllers is in being able to build a common controller board and then program it for whatever application you need without major wiring rebuilds.

My starting point was the Velleman programming board from Maplins (part N61CG), which connects to the COMM port of your PC - make sure you have a COMMs port since the programmer is not a USB version. If you only have a USB connection there are other USB type programmers available.

Once you have the programming board, you then write the software code on microsoft Notebook, compile it using  MPASM, Microchip's Universal Assembler, which you can download for free from the internet and then physically download the program onto the chip using Velleman's PICprogrammer (I think thats from the disc that comes with the board).

The board has all the essentials to start programming - little push button switches and LEDs - and also some starter programs for demonstration, which you can modify and test yourself. All my programs have descended from the demo programs. One note of caution- always manage your software by ensuring you use a version sequential numbering system (V1, V2 etc.), note the major changes between versions and the date (this can all be written at the start of the code) and KEEP backups on DISCs. Never change a working version, always make a new version and change that.

You can see the dichotomy here - what starts out as a model boat forum topic rapidly descends into "computerspeak", but, for some modellers, the technology offers solutions to some awkward control problems, plus the opportunity of some innovative "on-board" action.
As an example, for an RNLI fundrasing event last year, I programmed the PIC controller on my RAF Crash Tender to send slow morse code on its search light with the message "Grace Darling"  and offered a prize for decoding it (damm -  I'll have to change the message now!).

The Administrator may have a view on this venturing off into another realm of technology far removed from what is essentially the manual craft of modelling boats.

Thanks again for your interest and I'm quite happy to answer any questions.

Ian.


Title: Re: Flash steam plant control.
Post by: BarryM on March 14, 2009, 01:11:30 PM
"The Administrator may have a view on this venturing off into another realm of technology far removed from what is essentially the manual craft of modelling boats."

I hope not; this is all about model control and that is as pertinent as planking a hull.

Keep going,

Barry M
Title: Re: Flash steam plant control.
Post by: steamboatmodel on March 14, 2009, 03:21:42 PM
Ian stated "
My starting point was the Velleman programming board from Maplins (part N61CG), which connects to the COMM port of your PC - make sure you have a COMMs port since the programmer is not a USB version. If you only have a USB connection there are other USB type programmers available."
I have one of Microchips PICkit 2 units which uses USB
http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1406&dDocName=en023805
so far I have only played around with the demo programs on it and haven't developed anything else.
Regards,
Gerald
Title: Re: Flash steam plant control.
Post by: nick_75au on March 15, 2009, 09:38:40 AM
Hi Ian,
Very impressive work, I am interested in your feed pumps, any more detail on these please.
regards
Nick
Title: Re: Flash steam plant control.
Post by: flashtwo on March 15, 2009, 04:00:46 PM
Hi Nick,

Here is a close up of the "duty" pump, the "standby" pump being a mirror image and located on the other side of the engine.

The first photo shows the main pump body with a 50p coin in front (no Aussie coins I'm afraid!) with the 1/4inch (6.35mm) ram going to the right. The crank is connect via a 100:1 gear box to the electric motor. On the crank arm is a small 2mm rare-earth magnet which is detected by the Hall effect chip located on the bearing block (see 2nd photo for detail).

The Hall effect chip sends a once-per-rev pulse to the micro-controller PIC where the software program converts the signal into cc/min feed flow, knowing the effective pump displacement. The feed flow signal then goes to the feed pump control PIC, which completes the control loop by controlling the feed pump's electric motor via an ESC.

The whole reason for doing this is to make the feed flow independant of the boiler pressure - if the boiler pressure goes up then the pump pumps harder (not faster) to maintain the desired flow.

Hope this is the detail that you wanted.

Ian.
Title: Re: Flash steam plant control.
Post by: flashtwo on March 15, 2009, 04:04:38 PM
Here's the one with the coin before it was spent on sticky sweets!

Ian
Title: Re: Flash steam plant control.
Post by: nick_75au on March 16, 2009, 10:29:12 AM
Hi Ian
Thats was exactly what I was looking for, I inferred from the first group of photos that it was a gear type pump, obviously not :-)
I don't quite understand this statement?

"if the boiler pressure goes up then the pump pumps harder (not faster) to maintain the desired flow."

you don't increase speed of motor at all? or is that tied to the rpm desired perameter, is there a servo operated bypass that varies the output of the pump? am I getting two things confused?

RPM desired tied to cc per minute I guess?

Nick
Title: Re: Flash steam plant control.
Post by: flashtwo on March 16, 2009, 02:48:20 PM
Hi Nick,

The pump pumping harder not faster has the analogy of driving a car from the level then up a hill. You can maintain the exact same speed (i.e. pumps strokes/min) ,if, when you start to climb the hill, you put your foot on the throttle and the engine's power output increases, but not it revs ( assuming you stay in the same gear).

With the electric motor, the electrical current increases, creating a greater magnetic force in the coils, which ultimately opposes the boiler pressure.

The steam engine speed depends on the steam production, which depends on the feed water flow. Obviously, if the engine is required to work harder (and not faster!) the steam pressure has to go up, which according to the steam tables, gives you less volume of steam to play with and results in more feed water having to be supplied.

The other control loop, which looks after the engine speed, is the one that measures the engine speed (the same method as measuring the pump RPM), compares it with the desired speed (transmitted from the shore) and works out if there is a discrepancy in the feed water being pumped. If the engine is running slow, then the feed water demand is increased and the pump speeds up - more steam is then created to speed up the engine, and vice-versa.

The is no by-pass valve or throttle valve in the system - only a gas valve and pump non-return (clack) valves.

The pump's  effective measured displacement is 87%  of that calculated from the ram diameter and stroke - measured against a nominal boiler pressure of 2 Bar.

Ian
Title: Re: Flash steam plant control.
Post by: nick_75au on March 17, 2009, 05:34:14 AM
I thought that's what you meant, couldn't get my head around it.
 I think I understand it now. Pump speed determines engine speed. at steady state rpm the control loop measures pump rpm and attempts to maintain fixed rpm, Slowing (increased pressure) increases and speeding up (reduced pressure) decreases the speed command to the ESC, in effect only changing the current draw of the pump.
Am I correct?
Nick
Title: Re: Flash steam plant control.
Post by: flashtwo on March 17, 2009, 03:06:46 PM
Hi Nick,

That's quite correct!

Ian
Title: Re: Flash steam plant control.
Post by: flashtwo on May 21, 2009, 10:09:08 PM
Hi,

Just a quick message to say the test vessel, with its flash steam plant and computer controls, is due for its maiden voyage at the Modelboat Mayhem meeting this weekend.

Over the last few weeks I've been tuning the control system for the best and most stable response, and the flexibility of the control method has enabled a few carefully crafted software mods to be implemented.

So, with sturdy software manual close at hand, the day of judement has arrived (gulp!).

I hope to be there early Saturday morning, so be prepared for something totally different!

A big thankyou,  once again, to SteamboatPhil  for his encouragement at the 2006 Warwick Model Boat Exhibition, its only taken 2 and 1/2 years but its been worth it.

Next project? I think I saw a suggestion somewhere on this forum for a steam powered Bluebird K7 - hmmmm........

Ian G.
Title: Re: Flash steam plant control.
Post by: SteamboatPhil on May 21, 2009, 11:04:14 PM
I look forward to seeing it this weekend Ian
Phil
Title: Re: Flash steam plant control.
Post by: kiwimodeller on May 22, 2009, 12:28:35 PM
And dont forget you have to post the results no matter what the outcome! Even experiments that do not go quite as planned are still a good learning.
Title: Re: Flash steam plant control.
Post by: flashtwo on May 22, 2009, 02:35:40 PM
Hi Ian

I suspect I might learn a lot tomorrow - its fun and I musn't take it too seriously (despite the all the hard graff!) and I hope it raises a few chuckles and laughs.

As regards posting the results, it might make such a large impact (about crater size!) the other (surviving) Mayhemers may report back anyway.

It has been suggested that I name the boat "Flash-Bang-Wallop"; it has been named, but not that!

Well, I'm  off to load the car now - I hope I don't forget anything vital!

Ian G.
Title: Re: Flash steam plant control.
Post by: flashtwo on May 25, 2009, 08:12:43 PM
Hi,

Well the maiden voyage of the computer controlled test vessel (now named the "VITAL BYTE" not "Flash, Bang, Wallop" - Phil) was a great success.

With engine oiled and the lead ballast loaded, the boat was lowered into the Wicksteed pond and the boat prepared for steaming up. The pumps were primed, steam system filled right through to the engine exhaust (its a flash system remember) and the raise steam sequence initialised on the computer system.

By this time a small crowd had developed and it was bit of a task answering all the questions as well  as remembering how to start the sytem.

The steam started to issue from the exhausts, I closed the drain valves, set the steaming rate  (both via the radio), and watched the pressure rise on the servo driven indicator. On going above 50kPa (sorry 7psi), I set the valve gear to forward and the prop started churning the water. Having ensured that the revs were stable, I gave the Vital Byte a push and off she went just like a kid on its first day at school (you're on your own now!).

I had planned for every version of failure, but not success - the craft just chugged off around the lake under complete control (the first, to my knowledge, of a remotely controlled flash steam model in the world , although corrections will be welcome!). I gradually increased the engine revs setting on the transmitter and the Vital Byte responded quiet well considering its displacement of 32kg (5 stone, 70lbs) and very primitive hull shape.

I'm afraid the sedate (compared with the high speed models) did not attract much attention and lacked totally the theatre and action of SteamBoatPhil's flash steam boats (including the  foot high flames!).

The only problem I had was that, on ocassions, the engine didn't go into reverse on the first call and it took sometimes a couple of thows of the valve gear to achieve reverse - going forward was successful every time (obviously the mechanical engineer's problem and not the software guy's!).

Vital Byte chugged around for ages, only coming back to shore to have the oil separator emptied and off around the pond again. At no time did the boat stop because of high temperatures. etc. It maintained a steady speed and wasn't affected by any gas cylinder cooling. I noticed from the gas cylinder pressure display, that, although the pressure dropped under hard running, the pressure soon recovered when taken back to a slower speed.

I measured the gas consumption for the day by weighing the cylinder before and after - it was 333grams, which was 72% of the original 460 grams in the cylinder.

A lot more interrest was shown when the boat was ashore when fellow Mayhemers could see the computer controls (the full spectrum of remarks were made!) - Dave from Action Electronics initially described me as a Geek on first seeing the control system, but then, kindly, after I had described the system, changed this to SuperGeek!

With confidence (and because the car was already loaded up), I took the Vital Byte to my more local lake (30ft deep) the next day. I had trouble starting since the new gas cylinder pressure was 3.4bar (the cylinder had been in the car under the hot sun) , which was far higher than the control system had to adjust for in tests. The gas valve sensitivity is automatically changed by the software with respect to the gas supply pressure and had effectively shut itself down due to the high pressure (a software mod coming up I see). To get around the problem I manually (via the computer) opened the gas valve for a brief period and the gas pressure dropped enough for the auto system to take charge and steam was raised as normal.

Again off went Vital Byte around the lake (giving way to sail where necessary) and a good mornings steaming was achieved using 228 grams of gas (50%).

Well, I shall now start adjusting the controls to enhance the performance and subsequently make a new computer (1/4 of the orignal size) now I know what is required for COMPUTER CONTROLLED FLASH STEAM BOILERS!

Ian.
Title: Re: Flash steam plant control.
Post by: kiwimodeller on May 26, 2009, 11:40:26 AM
CONGRATULATIONS! Extremely well done but unfortunately not the first. There was an article in Model Boats, August 2005 by George Thomson about his r/c boat called OOYAH (the noise you make when you forget how hot some of the bits get!) which he eventually developed to do about 30mph under control although not computer controlled. This is the article that first got me keen to do something one day. Now will you please :-
A) write a book or at least a magazine article so we dummies can read it all through several times slowly
B) Package up and market the neccessary "plug and play" computerised control box with instructions on how to do it all.
I for one know my limitations and reading instructions and following them is something I can do!
Keep up the good work, I am sure the flawless performance was its own reward. Cheers, Ian.
Title: Re: Flash steam plant control.
Post by: flashtwo on May 26, 2009, 07:03:51 PM
Hi Ian V,

Alright, alright  - the first radio and computer controlled flash steam model boat in the world (hows that); a bit like defining the first passenger train in the world.

Thats sounds interesting about George Thomson's boat OOYAH, I must track down a copy of the article.

Could you describe his method - it would very interesting to compare the two methods and we might come up with something even better (and simpler!).

I have been asked to write an article for "Engineering in Miniature" magazine, but wonder if it would address the right audience, plus the long delay between submission and publication by which time the Mark XII version would have been developed!. Perhaps the "Model Boats" magazine would be better since they have already published flash steam articles  - any ideas?

Regarding a "plug and play" version - well until the maiden voyage, I thought it was going to require a lot of skill in operating it, but not so, and also I can see some simplification is possible with the hardware by going for serial instead of parallel communication between the computer and the display unit (which is not needed on the boat anyway).

Did you see my posting regarding your pitch/throttle control problem?

All the best and thanks for your interest.

Ian G.


Title: Re: Flash steam plant control.
Post by: SteamboatPhil on May 26, 2009, 08:25:35 PM
Hi Ian
Crongratulations once again, it was good to see it finaly go (and I missed taking a few pics, still this Sunday)
I would stick with the artical for EIM as a first hit and then maybe go onto MB. george's boat used a single cylinder uniflow exhust engine (much favoured by the the tethered hydro lot) with a flash steam coil and engine driven pumps (fuel and water) with vaporizing petrol blowlamps. 2 channel radio (steering and basic throttle)
However the first radio flash steam boat used the Alan Rayman designed high speed engine (the same as I have in Paprika which I was running at Wicksteed) which was about 10 years ago, however it only had steering.
So in a nut shell, yes you are the first to do a complete radio (and computer) controlled flash steam boat  :-))

Unless of course someone out there knows different  ;)
Title: Re: Flash steam plant control.
Post by: logoman on May 27, 2009, 12:37:05 AM
congratulations Ian.
wish i had been there,
Title: Re: Flash steam plant control.
Post by: kiwimodeller on May 27, 2009, 12:10:53 PM
Ian, Yours may not be the first R/C Flash Steamer but it shore as heck is by far the most sophisticated and controllable. If you cannot find the article about Ooyah send me a P M with your address. I do not have the facility to scan and email it easily but would be happy to copy it and send it by snail mail. Cheers, Ian V.
Title: Re: Flash steam plant control.
Post by: Martin [Admin] on May 27, 2009, 06:33:49 PM
Here she is seen at Wicksteed over the Mayhem weekend...
Title: Re: Flash steam plant control.
Post by: flashtwo on June 01, 2009, 02:22:04 PM
Hi,

Thankyou Martin for posting the maiden voyage photos of the "Vital Byte", it is very much appreciated.

Yesterday "Vital Byte" made first steam on the Blackheath Pond, which, in flash steam circles, is a famous for it association with flash steam experimenting over several generations.

Having overcome the pond access problem of its inclined sides (SteamboatPhil gave me some welly - i.e. he lent me a spare pair), Vital Byte was steamed up (no problem this time with too high a gas cylinder pressure) and off it went around the pond.

I experimented with various superheat (software) settings and got up to a good speed. Again a lot of interest was shown at the pond side by Blackheath Club members and the public.

I had the honour of demonstrating the boat and its control system to Alan Rayman, the co-author of "Experimental Flash Steam". He said, considering the basic hull shape, that the performance was quite adequate for its displacement of 70lbs (32kg), I think the consensus was that I should now build a proper hull to get an even better performance. Alan also suggested doubling the size of the displacement oil lubricator, considering the long runs that I was doing, or even fit a mechanical lubricator.

Total gas consumption this time, including start-up, was 111grams (I must start timing the runs). I'm getting two good days out with one 460gram cylinder and that works out to about £2-60 per day for the gas.

One software change I'm going to make is to give the servo driven indicator on the "bridge" the ability to display boiler pressure or gas cylinder pressure. I can then use it as a fuel gauge to get the most out of each cylinder without ending up with lots of partially emptied ones, i.e. if i see the gas pressure dropping well below 100kPa (14psi) I will then think about bringing the boat back to shore.

Ian.
Title: Re: Flash steam plant control.
Post by: gondolier88 on June 01, 2009, 05:44:38 PM
Hi Ian,

Whats stopping this tech' being applied to full size flash steam plants- the auto software I mean- not so much the RC  :-))

Greg
Title: Re: Flash steam plant control.
Post by: flashtwo on June 01, 2009, 11:30:03 PM
Hi Greg,

That's food for thought.

If the full size boat was gas fired and had an electric feed pump, then perhaps a higher torque gas servo and a higher rated ESC for the pump motor would be the main changes. A thermocouple would have to be installed to measure the steam temperature and a pressure transmitter for the boiler pressure. There would be no real difference in price between a full size or model boat control system.

If there is only an engine driven mechanical pump, then some means would be required to measure and control the feed flow by leaking off excessive feed. If the firing is with solid fuel then electric fans / air dampers would have to be employed to control the heat input, though the control would be quite sluggish compared with gas/oil burners.

The control system is designed to be tuned for different rates of heating, i.e. larger burners and more boiler mass.

I'm afraid that most traditional mechanical control systems for flash boilers were at their limit - they could not be easily modified for the best performance nor tuned for the best response.

With the software based system, there are lots of "features" like over-firing protection on start-up, high temperature and high pressure shut down of the gas valve, acceleration modes and also the ability to see whats going on regarding pressures, temperatures, feed flow and engine speed to mention just a few.

I suppose it depends on the boat owner - does he/she want to experiment or stick with the traditional methods and will it make the running easier.

The model boat is perhaps a useful tool for developing a system for a full size boat - modelling in the true sense of the word.

I'd be interested in any further thoughts you may have.

All the best,

Ian.

Title: Re: Flash steam plant control.
Post by: flashtwo on June 03, 2009, 06:31:01 PM
Greetings All.......

I've just installed the latest software so that the boat times itself and displays the run time in minutes (saves me remembering to start/stop timing).

The computer now also records and displays the following data:-

a) Maximum engine RPM attained.
b) Maximum feed flow.
c) Maximum boiler pressure
d) Maximum steam temperature.
e) Maximum economiser outlet temperature.
f)  Maximum gas cylinder pressure....
g) ...... and Minimum gas cylinder pressure.
h) Total and Run engine revolutions (not RPM).
i)  Total and Run pumping strokes.

The servo driven mechanical pointer can now be selected to display the boiler pressure for start-up conditions and then gas cylinder pressure for cruising, so acting as a fuel gauge.

Now I know why its called software - its so flexible!

Must get the Vital Byte back on the pond to see if the latast software works.

Ian.

Title: Re: Flash steam plant control.
Post by: flashtwo on June 08, 2009, 09:59:58 PM
Hi,

Vital Byte's skipper screws it up!

Vital Byte's latest voyage was down at Dover at the weekend (not in the Channel but at Kearsney Abbey!). The Model Boat Association Dover had its annual open day on Sunday and the oportunity was taken to do some test runs and play around with the control settings.

Questions were naturally asked about boiler certificates etc., but it was soon understood that none were required for a flash boiler.

The first run was going fine for the first 15 minutes, until Richard from the Maidstone Cygnets MBC made the remark that the response was very impressive - that was the death knell!   Vital Byte was going at Warp Speed 9, when it became apparent that steering was not what it had once been - "She's not answering the helm Cap'n" cried out an imaginary Scotty from the engine room!

As we were literally heading to the rocks something had to be done fast - luckily the engine went into reverse, VB slowed down and Alan Poole, of the Dover MBA, quickly organised a rescue mission. With the use of other members boats, VB was nudged to the shore. Thanks all round.

A quick examination revealed that the servo to rudder adaptor had become loose ( all that showing off of the response!); with a quick application of the screw driver, VB was soon back out on the pond, but without the skipper throwing the rudder all over the place.

VB did two long runs - one of 31 another of 44 minutes, the timing being done by VB itself. The new software features worked (except for total revs for some reason) and maximum and minimun parameters were logged. Gas consumption was 4.0g/min for the first run and 4.5 for the second run.

I did alter the feed water controller for the second run a bit too much and VB stalled out in the middle of the pond and became stationary - another rescue mission was offered by club members, but this became a test of its automatic recovery mode of operation (the Mars Rovers have nothing on this babe!). After a few minutes a wisp of steam was seen to rise and slowly VB came back to life.

I managed to capture some valuble data and will also now incorporate an average RPM reading. The maximum RPM achieved was 570 although I'm aiming for 800 which is what I obtained from Malcolm Beak's equations.

At the moment I'm trying to understand where the limitations are - gas nozzle size? gas consumption? heating area? etc.

Thanks once more to Dover MBA for their help and interest.

Ian.

p.s. One secret development I've not mentioned is the Carbon Capture environmental feature of the boiler. This was secretly photographed by Alan Poole of Dover MBA and I have obtained an exclusive  copy for Mayhemers! The green carbon capture spheres (CCSs) are collected from the pond after the experimental runs! (see attached photograph).
Title: Re: Flash steam plant control.
Post by: flashtwo on July 05, 2009, 10:10:42 PM
Hi Mayhemers,

Just an update on the latest voyages of the Vital Byte.

VB has had a few mechanical and software problems over the last two weekends on the Cygnets Model boat Club venue at Mote Park, Maidstone.

VB had a run of 18 minutes to use up gas in a partly used cylinder and achieved 588RPM max with a gas consumption of 4.3g/min and then, with a fresh cylinder, a 53 minute run at 593RPM max and 3.7g/min consumption. Unfortunately the "A" pump motor blew its fuse and I had to swop over to "B" pump between the two runs.

Inspecting the pump later, I found that the ram was tight because the pump body had become slightly misaligned. With the help of a piece of SteamboatPhil's kindly supplied shim, the body was realigned and was tested OK.

The software recording the engine revolutions (and average RPM) was not working and was found to be due to part of the calculation taking place during the speed probe pulse. The calculation was moved in the software to occur after the pulse and the data is now being recorded properly.

Previously, at Kearsney Abbey, I had been monitoring the ambient temperature of the bow compartment where the gas cylinder is located with a max/min thermometer. Well, as reported elsewhere on this forum, the thermometer melted and it contents disappeared! Therefore, I have made a ventilation hole and an aluminium shield directing the heat away from the cylinder area.

The ongoing problems of putting the engine into reverse were traced to the drive-end "B" cylinder valve timing and also the "A" piston bottoming out, causing stiffness at bottom dead centre.

Having sorted all of the above problems, VB had another outing to Mote Park last Sunday - and what a disaster it was!

I spent the best part of an hour chatting to people about the boat and its computer before I attempted to put her on the water. The pump jammed again and the computer overheated due to the sun shining through its clear plastic cover (it was acting like a greenhouse) whilst it was on the shore. No voyage on that outing.

This time it was found that the pump was fine but the commutator end of its electric motor had become loose and resulted in loss of output. The gas control chip had failed on the steam temperature input of all things. A new motor and gear box was fitted and tested and a new PIC chip fitted and downloaded with the control program.

A fan was fitted to the computer housing for use on very hot days (you can tell this developed in the winter!) and the pump control software was modified to automatically switch to the standby feed pump within 6 seconds of the main pump failing and also a gas valve shut instruction was added if both pumps failed.

Today VB managed a decent run at last. She moved effortlessly between forward and reverse, maximum bow compartment temp was 28degC instead of 50plus and the pumps worked ok. Max RPM was 580 and average was 334. The engine was ticking over at about 50kPa (8psi).

On the water at the same time was the Cygnets 50th anniversary build of HMS Kent, type 23 destroyer. She was having a shake-down cruise before her epic voyage between Tonbridge and Allington Locks, via Maidstone, on the River Medway next Saturday 11th July ( visit http://www.cygnetsmbc.com/ for details of the day). The 12 foot model just cut through the water like a knife through butter, a magnificent achievement.

Vital Byte will be exhibited at the Guildford Steam Rally on the 18th/19th July, I hope to see some Mayhemers there.

Ian.

Below - the latest VB photo.

Title: Re: Flash steam plant control.
Post by: SteamboatPhil on July 05, 2009, 10:36:20 PM
Great stuff Ian, oh the joys of flash steam. I have just re-done the fuel pump on my flash steamer, plus a new flame tube (I'm using vapourising petrol not gas like Ian)
Got a few good runs in today (in fact I won the steering event), also picked up a lot of weed. Keep going Ian (then I can pinch your data)   :-)) :-))
Title: Re: Flash steam plant control.
Post by: flashtwo on July 23, 2009, 10:47:16 AM
Hi,

VB made it to the Guildford Steam Rally in one piece and was set up outside the marquee (it allowed room for four other smaller boats to be inside!) on it very own display stand. This was a bonus since it reduced the amount of carrying to and from the demo pool, though not such when it rained!

The demo pool was just deep enough for display, though, and being only 20x20 feet square, it presented a fine opportunity for learning to manoeuvre in confined waters. Full use was made of the reversing gear, now that it is reliable. About six demo runs were made over the weekend.

Although the pool size prevented maximum performance, it did allow the visitors closer inspection of the engine and its control system display, whilst in operation and also the method of raising steam quickly with the flash boiler compared with the more conventional plant.

With VB on static display, the boiler heatshield and control compartment covers were removed to allow the flash coil and computer to be viewed. Again the visitor response was as varied as their own experience. Some appreciated the boiler simplicity and just walked away on seeing the computer,  whereas others were very knowledgable on control theory and others on the use of PIC controllers.

It was an excellent oportunity to compare the flash boiler technology and it computer controls with a conventional steam plant on display in the marquee. The plant was to power a 82lb displacement tug also using a Stuart  D10 and running with a 4.25 inch prop. This was very close to the VB arrangement although there was no comparison in the hull design!

Chris the owner, and Guildford Club member, kindly took me through his design and build documentation book that he had on display. It was a very profesional comprehensive engineering document with all the materials lists and stress calculations and every thing you would want to know on how to construct the conventional boiler.

Both of us had used Malcolm Beak's calculation method, but the only trouble was that Chris had used imperial and I metric units, so making comparisons difficult (a certain  American Mars probe comes to mind!).

Chris described his boiler construction method and the difficulties that he had overcome. I came to the conclusion that I had transferred the effort of making steam from a boiler making to a software exercise. The flash boiler coil only took a couple of hours to wind and had two silver soldered connections,  but the control system  took many, many hours of work -  the complete opposite of the conventional approach. Chris's tug and marine plant have been built to a very high standard and he hopes to demonstrate it at next years rally.

A few Mayhemers turned up. Logoman with Logowife and Logokids were there, plus a few that that had seen the plant at the Ally Pally in January before VB was built. Their interest was very much appreciated.

Many thanks to Bryan Finch of the Guildford Club, who organised the boating section and greatly assisted me in carrying the VB back and forth to the demo pool. He has encouraged me to build a lighter boat!

VB will be at the "Boats on the Mote" Cygnets Club open day at Mote Park, Maidstone this coming Sunday. I shall be carry out a few experiments with VB.

Ian.






Title: Re: Flash steam plant control.
Post by: gondolier88 on July 23, 2009, 11:06:15 AM
Hi flashtwo,

Good to hear the different responses of people to the controls- your a pioneer in the model boat world mate! :-)) 8)

Just need a hull to match your electrickery now....!!!!! O0

Greg
Title: Re: Flash steam plant control.
Post by: Dave_Sohlstrom on July 26, 2009, 12:02:34 AM
Ian

I have been watching your progress from my side of the pond. Very interesting. Would it be possable to fit one of your computers to a conventional water tube marine model boiler at 100 psi and about 400 SQ In heating surface. boiler will be running a long stroke engine on a model stern wheel tug. search Steam Tug Portland.

Dave
Title: Re: Flash steam plant control.
Post by: gondolier88 on July 26, 2009, 01:10:34 PM
Hi Dave,

Good to have you here mate. What are you wanting to be controlled by the computer? Do you want a crewless engineroom or secondary emergency control?

Greg
Title: Re: Flash steam plant control.
Post by: flashtwo on July 26, 2009, 05:24:17 PM
Hi Dave,

Thank you very much for your interest.

The conventional boiler is best to suited to a method of water level control, which would use an electric pump to top up the boiler when necessary. The level can be detected in various ways - optical through the level sight glass or via a resistance / capacitance probe within the boiler shell.

The flash boiler requires a different system where the electric pumps maintain a desired flow independant of the boiler pressure.

Also, the conventional boiler needs to control its steam pressure at a constant value by adjusting the fuel supply e.g. via a servo controlled gas valve. Normally this is achieved in a model by measuring the steam temperature with a thermistor, since steam saturation temperature is directly related to pressure. The thermistor, being a resistance device, would then be part of a voltage bridge circuit which would ultimately control a relay that operates the electric pump.

The flash boiler doesn't bother to control pressure, just steam temperature - aha! I hear you say, isn't this the same as the conventional where the pressure is the same as the temperature - well, no - if the steam pipe was open ended, for example, the gas valve would open to maximum trying to raise pressure, but would just overheat the steam (perhaps to 400degC or more) and stress the engine and piston seals.

My computer could be reprogrammed to control a conventional boiler, but it would a bit of an overkill.

I hope this not teaching grandmother to suck eggs, but the flash control is totally different from conventional boiler controls.

Let me know if you require any additional info and I will try and comply.

Ian.

Title: Re: Flash steam plant control.
Post by: Dave_Sohlstrom on July 31, 2009, 02:11:12 AM
Greg

Sorry for delay. Changes at work will put me out of work 15 months earlier than planed. We are crunching numbers now and it looks like we can make it the 8 months till I'm 62.
The Stern Wheeler I am looking to model is the Steam Tug Portland. She was retired from active ship handleing duties in1981. She is still aflot and they steam her a couple of times a year. Last year going up the Columbia river for a race she lost steering and damaged her rudders and paddle wheel. I was able to get a lot of pics while she was in dry dock. She is 210' LOA and 42' wide. The model at 3/8"=1' will be close to 7 ' LOA and nearly 16" wide. Engine will be 3/4" bore and 3 3/8" stroke. Will be full RC control and have an 8' barge with extra fuel and water for her to push around. I have not been able to find qualified marine engineers in 1/32 scale that will work for free so I will have to put automated controls on the boiler so I do not run out of water or steam in the middle of the pond.

Ian

Thanks for the reply. I will be researching how to best control water level and pressure. I expect the boiler to be a fast steamer with the number of water tubes it will have compared to the water volume that it will have.
 
I will continue to keep an eye on your project and will probably ask more questions.


Dave
Title: Re: Flash steam plant control.
Post by: gondolier88 on July 31, 2009, 07:34:41 AM
Hi Dave,

Great project, I hope you see it through to the end. Have you got a pic to show us?

At that size you would have enough room to have mechanical control- ie. a feed pump acting off the engine through a bypass controlled by a water sensor on the water gauge with an auto boiler pressure gas regulator controlling the burner.

Greg
Title: Re: Flash steam plant control.
Post by: kiwimodeller on July 31, 2009, 11:21:12 AM
Dave, sounds like a great project, don't forget that we expect a fully illustrated ongoing post as you do the build, just so we have the pleasure of nitpicking any little mistakes you make. Just kidding! :} But we would all like to see the build. I take it from your description of the engines that you are going to build them as direct acting on the paddlewheel shaft? I am hoping to do the same when I build a model of a New Zealand sternwheeler but it will not be at such a large scale. I am looking at 1:24 and two cylinders of about 3/8" bore and 2" stroke. I am hoping somebody else has or will sort out all the problems before I get started. Cheers, Ian V
Title: Re: Flash steam plant control.
Post by: gondolier88 on July 31, 2009, 10:42:10 PM
Hi Ian,

I am looking at 1:24 and two cylinders of about 3/8" bore and 2" stroke.

Very strange cylinder  size- any reason for this in particular? You'd be lucky to get any workable rev's off that- I know sternwheelers don't need a lot of rev's anyway- but I have a feeling that would be excessively slow.

Greg
Title: Re: Flash steam plant control.
Post by: Dave_Sohlstrom on August 01, 2009, 03:01:31 AM
I have to agree with Greg. You are building at 1/2"=1' at 1:24. That would make the real engine 9" bore by 4' stroke seems small for that scale. Portland full size engine is 26" bore and 9' stroke. How long is the full size vessel you are modeling. Portland is 210 feet long, she is a big tug.

Dave
Title: Re: Flash steam plant control.
Post by: kiwimodeller on August 01, 2009, 01:00:30 PM
The original was just over 100ft so not large by American sternwheeler standards. I am not yet sure of the original bore and stroke, still waiting on the plans but the idea of the long stroke was to give good torque and sufficient leverage at the wheelshaft by having the big end a reasonable distance from the centre of the shaft. I read somewhere that small bore long stroke steam engines were slow revving but produced good torque and were still economical on steam as the long stroke utilised all the expansive properties of the steam. Theory of course is not always right and I am ready to change my ideas, in fact it would be easier to have a shorter stroke engine, but would I get away with that without having any sort of gear reduction between the engine and the shaft? I am always happy to blame someone else's ideas when things dont work! :embarrassed: {-)
Title: Re: Flash steam plant control.
Post by: Dave_Sohlstrom on August 01, 2009, 06:56:03 PM
Ian

Do you have the name of the vessel you are going to model. It may be possable to find information on line.

Dave
Title: Re: Flash steam plant control.
Post by: gondolier88 on August 01, 2009, 11:30:09 PM
You wouldn't need anywhere near the torque required fullsize- remember torque is a square and weight is cubed- go for a shorter stroke- easier to steam, easier to start, and should you need it on the pond- a burst of speed.

Also you could always utilise commercially available stationary mill engine cylinders.

Just a thought.

Greg
Title: Re: Flash steam plant control.
Post by: kiwimodeller on August 02, 2009, 11:43:21 AM
Dave, the vessel is called Manuwai, a Whanganui River (New Zealand) sternwheeler built in kitset form by Yarrows. Model plans are in the process of being drawn up. When I said I did not have the original engine dimensions I meant they have not arrived to me yet but I know they are available and will arrive, there is considerable information about her available.
Greg, I agree it would be much easier to use a shorter stroke and utilise commercial cylinders from someone like John at The Steam Chest who has a great range of engine casting kits that I have been eyeing up and I will do so as long as I can be convinced that they will have enough grunt. We had the discussion at a club day today and the older members are definitely of the opinion that small bore, long stroke engines operating on fairly high pressure and using all the expansive power of high pressure steam will do the job best. Other members, like you are saying that the greater power of more piston area will be more responsive and that I will not need high pressure. It seems quite possible that both would work, the first with high pressure but using a lower volume of steam, the second option using lower pressure but needing a fairly big boiler to make a high volume of steam. It may well be that I need to suck it and see, fortunately it will be a few months before I finish present projects and get on to this one so I have time to read up and canvas opinions on forums like this. Thanks for the input from both of you. Cheers, Ian.
Title: Re: Flash steam plant control.
Post by: kiwi on August 02, 2009, 08:37:39 PM
Hi Ian,
Just for the record
ps Manuwai had a locomotive type boiler rated at 160 lb. (at 140ib propelled the boat at 11.5 knots max speed ), built by Yarrows of London.
And mounted near the bow, consuming 6.5cwt coal per hour from two 3ton coal bunkers either side of the boiler.
Two engines at stern, horizontal with 10.5" bore and 30" stroke, with stephensons link fitted. Operated by telegraph from the bridge. Main steam pipes ran along the underside of the upper deck.
These drove a stern wheel of 10ft dia x 11'-9" width fitted with 10 floats of 9" wide English Elm.
Hull was of galvanised Seimens' mild steel, divide into 7 watertight compartments, each with its ejection pump. On the foredeck was a small double cylinder steam winch for hauling up rapids.

Drawings progressing well, and a friend in the trade is looking at making a fibre-glass hull if your interested, in the size your considering.
kiwi
Title: Re: Flash steam plant control.
Post by: kiwimodeller on August 03, 2009, 12:10:09 PM
Harry, you are as usual a lifesaver and tell that man that I will give my first born son (I've been trying to get rid of him for 30 years) for a glass hull in the right scale  ;) :} Perhaps you could ask him nicely to increase the depth of the hull to give a little extra displacement to carry heavier (in scale proportions) boilers etc? I have already put aside a nice 9" by 4" boiler which looks the part to try first and am gathering parts and info. Todays effort was to go through my collection of 1940's/50's Model Ships and Powerboats and Voila! I found an Edgar Westbury treatise which discusses engines for different applications and says, in part, "the exception being engines for paddle steamers which, if connected directly to the wheel shaft need to be of small bore and long stroke. Shorter stroke engines need a bevel gear or other reduction to work satisfactorily when driving paddle wheels which rotate slowly". I knew I got the idea of long stroke engines somewhere and this was probably where. Cheers, Ian.
Title: Re: Flash steam plant control.
Post by: flashtwo on October 18, 2009, 04:25:15 PM
Hi all Mayhemers,

At last Vital Byte is back on the water (after sorting out new kitchen/university etc).

Since its last run at Ramsgate, it was apparent that no further software mods were going to improve the performance, so I reconsidered the boiler coil surface area.

In my original calculations I had estimated the surface area of the fire/copper interface rather than the copper/water interface the values being 138 and 84 sq.inches respectively. Obviously the 84 sq.inches was much to small for the D10 engine, so I've rewound and experimented with a number of coils.

The original was 5 metres of 1/4inch O.D. 18 swg copper and I have wound three additional coils  of 7 metres of 1/4inch 20 swg (142 sq.inches approx), 9 metres of 3/16inch 22 swg (149 sq.inches), and finally 15 metres of 3/16inch 22swg (240 sq.inches), experimenting with each of the coils in V.B. on the test pond (hasn't the price of copper gone up!).

I managed to get all 15 metres of the 3/16inch into the original boiler casing by winding the coil into three layers. It took an hour and three quarters to wind the coil (including a joint to connect the 10 and 5 metres sections together), turn two adaptors on the lathe and fit it in the boat.

The other change to V.B. is the use of a five inch prop, with the proper blade twist, kindly on loan from Malcolm Beak.

Today I steamed V.B. down at Mote Park, Maidstone and she performed extremely well with the 15 metre coil, showing a very powerful bow wave. The hull wave crested at the bow, midway and stern.

She had two runs of 28 and 38 minutes, RPM peaked at 610 and averaged 394. On both the runs the gas consumption was 4grams/minute. The acceleration was very good.

The gas cylinder pressure was monitored. It started of at 2.5bar, which obviously gave the best performance, and was still perfoming well when the gas supply was down to 0.6bar.

Well, I've run out of ideas now to improve what is now a very satisfactory performance, other than putting the plant into a proper hull.

On to the next project - a steam jet powered boat?

Ian


Title: Re: Flash steam plant control.
Post by: kiwimodeller on October 19, 2009, 10:40:34 AM
A steam turbine pulling 35,000 revs would sound good! cheers, Ian 2
Title: Re: Flash steam plant control.
Post by: gondolier88 on October 19, 2009, 06:56:08 PM
Hi Ian(s),

Turbine very interesting suggestion- have you seen the Tesla Turbine- kind of a percussive turbine using flat discs- but the 10inch(?) model produced around 30HP- imagine if you could use ultra-thin blue steel discs around 1.5inch Dia. running around 30,000RPM- drive through a half reduction gearbox to give useable and powerful engine.

Also- as you obviously like an experiment- have you seen the Brotan-Defner loco type boiler? Basically an efficient 3 drum watertube boiler forms the firebox, the top drum ,however, is joined to the top of a sloping barrelled conventional locomotive firetube boiler- having a tubeplate at either end though. This mean that at the point of the most heat- the firebox- you have extremely efficient heat transfer- massive surface area, low water content, fantastic water circulation- then the firetubed barrel uses the cooler gasses at a slower speed- extracting the useful heat left. The bottom drums of the watertube boiler are both connected to the barrel by extension tubes curving upto the bottom of the barrel giving increased water circulation.

Steam is taken off the top of the barrel slope or the top drum of the firebox- the thing is the variables with this boiler are numerous- tube diameter, number of tubes, length of tubes on the water tube side- barrel diameter, firetube length, firetube diameter barrel length- also a superheater of the Schmidt type could be fitted (the same type as fitted to the last types of BR express steam locos).

Basically a really developable boiler, could be made super heat efficient and also an interesting engineering project, something to thimk about.

Wikipedia and Google bring up results if you search Brotan boiler and Brotan-Defner boiler.

Greg
Title: Re: Flash steam plant control.
Post by: flashtwo on October 20, 2009, 09:10:04 AM
Thanks for your ideas guys - they're much appreciated.

I was actually thinking of building on my flash steam boiler experience and having a zero reving "engine", i.e. a pure jet with no moving parts apart from the feed water pump.

The ultimate aim is a steam powered Bluebird K7 (but with better high speed stability!) - wishful thinking perhaps, but I might learn something new on the way.

I've just started on the feed pump and I shall be using the boiler coils from the Vital Byte experiments.

The Vital Byte will still be in the frame though, since I want to reduce the computer size and extend the endurance. Currently VB is run time limited by the engine exhaust oil trap filling up and the displacement lubricator becoming empty. At a gas consumption of 4grams/minute, the 460grams in the gas cylinder, fuel supply is not a limit for extended running.

One question I have for those with conventional boilers is that when the water level drops in the boiler, does the heating surface area between the copper and water reduce thus affecting the performance of the boiler and engine and is it noticable?

Ian
Title: Re: Flash steam plant control.
Post by: kiwimodeller on October 20, 2009, 10:36:15 AM
Ian, the theory seems to be that with the common types of comercially made boilers available a vertical boiler is more affected by loss of heating area in contact with the water as the level drops than is a horizontal one. A horizontal single flue boiler with cross tubes in the flue would have to be down pretty low before there was a noticeable amount of the heating surface area not in contact with water. In my limited experience other factors such as the drop in gas pressure due to the drop in gas cylinder temperature have far more noticeable effect on the performance of commercial model boiler setups. Cheers, Ian V.
Title: Re: Flash steam plant control.
Post by: gondolier88 on October 20, 2009, 05:35:11 PM
Hi Flashtwo,

Steam powered K7 isn't too much of a far-fetched idea- in 2007(?) a flash steam powered hydroplane was entered into the Coniston Water Speed Trials- however although it had worked really well on experimental runs, on the day it failed to perform.

Greg
Title: Re: Flash steam plant control.
Post by: SteamboatPhil on October 22, 2009, 01:49:11 PM
The full size flash steam hydroplane will be returning to Coniston this year to have another bash at the record. I gather that John has ironed out all the bugs he had in 07.
I will keep you up to date on his progress.
Title: Re: Flash steam plant control.
Post by: flashtwo on October 26, 2009, 06:37:55 PM
Phil,
Has the Coniston flash steam hydroplane got a website - I'm intrigued. Regarding Vital Byte, I've got the feeling, since now I've 45 foot of tubing, that the traditional flash steam boiler really over-fires the boiler to achieve red hot coils and true flashing off of the steam rather than a boiling off. Do you calculate steam production in the traditional way of surface area of the copper/water interface or is it more a matter of burning as much fuel as possible? The point is my plant seems to be so tame (though still very effective) compared with the performance of your straight runners and the tethered variety or are they completely different animals.


Last Saturday, I remade the D10's slide valve push rods, since the originals had too much vertical play in them for accurate valve timing. On Sunday at Mote Park, the test run was a total failure due to the slide valves themselves not seating, consequently letting by all the steam. (club member Richard was there again, strangely coincident with major problems with VB!)

I discovered that, although the vertical slack had been eliminated, there was not enough clearance between the slide valves and the adjusting nuts, causing them to bind. By use of a fine file, enough clearance was made, timing reset and the slide valve seating was tested by applying suction to the respective exhaust port.

VB was run in the test tank and peaked at 642RPM and averaged 465RPM over an 11 minute run. Ready now for another run on the lake.

With regard to hull speed, I understand that is achieved when there is an equal  bow and a stern wave with a dip halfway along the waterline. If there is a wave halfway along the waterline does that mean it is going at half hull speed, or is it an indication of an efficient mode of running?

Ian G.
Title: Re: Flash steam plant control.
Post by: gondolier88 on October 26, 2009, 07:21:46 PM
Hi Ian G,

Wow you are getting into hull design as well as experimental steam eh!!!

Ok, a steam hull should always have the most efficient hull design possible. Indications of efficiency are-

- Little or no 'hull wave'- the bigger the wave the more the water is being pushed out of the way as opposed to being 'run over'.
- Bow lift- means displacement is in the right area- if the bow cuts in and down the displacement is dragging and needs more power.
- Stern stays bouyant at hull speed- the more it sinks the more wake is made and this just wastes power.

These go for displacement hulls only of course.

These are the two most efficient hulls in the SBA...currently ;)!

1- Arlette- 31ft single chine plywood with loco boiler and single cylinder thornycroft engine 3 3/4" x 5"(?)
2- Oberon- 29ft strip plank cedar hull, 3-drum LIFU boiler with 2 1/2" + 5" x 4" LIFU compound.

In the pics they are both running at full speed- this is Arlette- 16mph and Oberon- 14mph- both engines run around 600-700 rpm- do the maths with the engine's power and you can see how efficient these boats are.

Greg
Title: Re: Flash steam plant control.
Post by: kno3 on October 26, 2009, 09:17:05 PM
Where are the pics?
Title: Re: Flash steam plant control.
Post by: gondolier88 on October 26, 2009, 10:15:16 PM
Ahem...

Thanks Kno3

Title: Re: Flash steam plant control.
Post by: flashtwo on November 05, 2009, 08:53:30 AM
Hi Mayhemers,
Warning: this post contains computer speak!

Whilst waiting for some fine weather to test Vital Byte, I've started on the new control computer (designated the AE35 unit) which, hopefully, will be about a third of the size of the original and will fit into a smaller range of boats.

I'm also taking the oportunity to strip out a lot of redundant code and give the data displays a better layout. The AE35 will be using serial communication between the chips in place of parallel comms and the dedicated analogue and digital signals.

The test board for learning how to use serial comms is working and I'm now migrating the RPM software into the PIC chips for testing.

Previously I was using 40-pin PICs for measuring the pumps and engine RPM and have now replaced them with 18-pin PICs, thus saving a lot of room. Also, one of the original 40-pin PICs was totally redundant.

When using parallel comms, the Veroboard had 15  tracks dedicated for communication - using serial has reduced this to just four, thus another space saving measure.

Hopefull, Vital Byte will be testing its new "brain" (the AE35) before Christmas.

Meanwhile, back in the machine shop (shed!), the feed pump for the steam jet engine is nearly complete and the boiler casing will be started on soon.

I'm up at the Warwick International Model Boat show on Sunday, flitting between the Maidstone Cygnets stand ( with the 13ft HMS Kent)  and Blackheath's stand chatting with Phil Abbott about --- flash steam - what else!

I hope to see some Mayhemers there.

All the best

Ian G.
Title: Re: Flash steam plant control.
Post by: steamboatmodel on November 05, 2009, 12:57:35 PM
Hi Ian,
Re "The test board for learning how to use serial comms is working and I'm now migrating the RPM software into the PIC chips for testing. "
What is RPM software? Assembly, Basic and C I have played around with, but RPM is now to me. Also what chips are you using?
Regards,
Gerald.
Title: Re: Flash steam plant control.
Post by: flashtwo on November 05, 2009, 03:40:26 PM
Sorry Gerald,

I should have said the RPM (revs per minute) code that was used on the original computer control system. It is written in the Microchip PIC assembler.

The main workhorse of the board is the 16F877. I have one for display purposes and another for the actual control of the feed water flow and steam temperature. I've replaced three other 877s with 16F819s, to save space, and I have one 16F628 as a clock for timing the pump and engine RPM (it eliminates a large interrupt burden).

The chips are now linked with serial communications whereas before the RPM values were sent as voltage signals and other data as a simple digital signal.

Ian G.
Title: Re: Flash steam plant control.
Post by: steamboatmodel on November 06, 2009, 12:00:54 AM
Now things are clearer. I have one of Microchips PIC kit 2 programmers and a couple of there development boards which I intend to play around with. I have been waiting untill I get another computer that I can put in the shop to do the experimentation on as soldering and breadboards don't go down too well in the living room where this computer is. Until then I have been doing some studying and reading on the PICs.
Regards,
Gerald.
Title: Re: Flash steam plant control.
Post by: Fargo on November 06, 2009, 12:25:47 PM
Gooday all :-)

I'm a newcomer here, and absolutely hooked on the concept of flashboiler systems because I've never liked or trusted conventional boilers. I'd like to develop a flashsteam sytem that could eventually push my 12' aluminium "tinnie" along at a nice sedate pace, instead of the outboard which it currently endures.

Unfortunately I've not been able to find much information on such basics as coil configurations, types of burners (petrol, propane), or suitable engines, so I guess I''ll be asking plenty of questions. Can anyone suggest a very basic type of steam engine to use as an initial testbed? Something that has no reversing or throttling, and that can be built from stock materials preferrably? Am envisioning something on the order of 2 cylinders of about 30mm bore, to be fed by up to 20 metres of 1/4" copper tubing fired by a petrol or propane burner.

It's my belief that such systems can finally be made to operate safely and reliably, given the currrent abilities of microcontrollers available today.
Or am I just a dreamer??

I'm a retired Black Arts (electrical/electronic) guru, and self-taught machinist. Having built many different kinds of engines, I'm finally hoping to tackle the big one, flashsteam.

Regards all,
George Z


Title: Re: Flash steam plant control.
Post by: flashtwo on November 06, 2009, 04:36:01 PM
Hi George and welcome to the Mayhemers,

I've come the conclusion that whats traditionally regarded as model boat flash boilers are in fact heavily overfired causing the pipes to glow red hot and resulting in very high steam temperatures and pressures - the water really does flash off uncontrollably into steam. They use a tremendously lot of fuel for very short runs.

The system that I have developed is much more sedate and I think I should use the term "Monotube boiler", i.e. a single tube boiler, where the water is turned into steam in a controlled fashion, much more fuel economic and capable of extended running.

As I have said before, to obtain full control, the water pump flow must be independant of the boiler pressure, but settable for for different desired engine speeds. To this effect I have, for the model, used electric water pumps but, with a bit of inginuity, a purely mechanical version might be developed.

Regarding a full size version, you would have to start with the expected steam consumption of your engine and calculate the boiler copper/water surface area and from that the coil length depending on its diameter. One would also have to estimate fuel consumption and then the size of burner required.

My model boat has to look after itself out on the lake with me only transmitting the required feed flow and the onboard computer monitoring the boiler and making the necessary control changes. If you are on board it would more relaxing to have similar automatic controls giving constant attention to the boiler needs.

The boiler has a fast response to load changes and there is no throttle valve between the boiler and engine, speed control is purely done by altering the feed flow.

One of my other ongoing projects is marine propulsion with no engine at all!

There are other Mayhamers who are much more knowledgable than me regarding "full size" engines, perhaps they may wish to comment. With a controlled flash boiler, a conventional steam engine is acceptable.

In conclusion, what you are suggesting is entirely possible.

all the best

Ian G.
Title: Re: Flash steam plant control.
Post by: Fargo on November 11, 2009, 07:26:33 AM
Thank you for your input Ian.
A superfast model is not what I'm aiming for, but as I said, a sedate but reliable propulsion system. I'm currently doing my sums and trying to source components, but having a devil of a time trying to track down suitable temperature sensors at a reasonable price. Hoping to use thermistors rather than thermocouples.
Cheers,
George Z
Title: Re: Flash steam plant control.
Post by: flashtwo on November 25, 2009, 09:39:49 AM
Hi George,

Your choice of thermocouples (t/cs) has made me consider them as an alternative.

I last used thermistors many years ago and, although they were cheap and sensitive, were not very consistant in their accuracy. I see that their technology has now moved on and they are now better than thermocouples.

The only thing I'm concerned about is their temperature range, I've seen figures for -100 to +130C, but do they go above the higher figure?

I was really brought up using thermocouples and know their foibles. I've been using 1.5mm diameter type K t/cs, which are a good size to bend around the boiler and be fitted into the steam /water flow in the pipework.  I connect the t/cs to the AD597AH i.c. made by Analogue Devices, which linearizes the signal, applies the necessary cold junction compensation and gives a 0 to 5V linear output for a range of 0 to 350C - it can higher if the supply volts are higher.

I connect the 0-5V signal to my PIC based control system, but it could drive an analogue or digital voltmeter.


Ian G.
Title: Re: Flash steam plant control.
Post by: flashtwo on November 25, 2009, 10:12:27 AM
Hi Mayhemers,

Vital Byte has been out on the lake a couple of times recently in colder weather with the ambient at 11C.

As expected the gas cylinder has started to get cold and its pressure drops under hard running conditions. Despite this, the boat is still performaing well with the gas valve opening automatically to compensate for the lower available gas pressure.

There is a limit though and I can end up pumping too much water into the coil and end up with very wet steam. This occurs when the gas valve is fully open, due to the lower gas pressure, and no more heat is available. This can be solved by limiting the feed flow if the gas valve is approaching it maximum open position. I can either do this automatically in software or use  VB's "bridge" indicator to show gas valve position so I can check visually from the shore before applying more feed.

Last Sunday, I accidently left the computer display unit at home and had to start and run VB "blind". It worked ok (as designed), but I wasn't able to collect any running data as I would normally do. It does mean that,  perhaps on a smaller model, the display unit is not necessary to be permanently on board.

The forward/reversing on the engine is very reliable now, since remaking the valve rods and re-timing the engine.

At the Warwick International Boat Show, I visited the Prop-shop stand and discovered that they make a 5inch prop specifically for the Stuart D10 engine (I wish they had a proper web-site). I've ordered one and will be able to return the one lent to me  by Malcolm Beak.

Vital Byte will be on the Blackheath Stand at the London Model Engineers Exhibtion at Alexandra Palace in January. She should have, by then, her new smaller control AE-35 computer fitted. The development of the AE-35 is going well with the RPM and display code working. The serial communication between the chips is proved and it just leaves the control code to be installed, modified and tested.

Ian G.
Title: Re: Flash steam plant control.
Post by: Fargo on November 25, 2009, 01:55:00 PM
Hi Ian,

I've given the thermistor idea away for the very reason you mentioned ie. too low a max. temp., and bought myself a K thermocouple with a ring tongue which Ive bolted to a copper flag which will eventually be brazed to the boiler tubing. I'm hoping the thermal response will not be too slow doing it this way, but it seems to me to be the most convenient way of mounting it.

I'm currently using a 741 op amp as an amplifier, but getting the correct signal to the PIC will no doubt be messy. I'll probably end up copying your idea of the AD597AH.

Managed to get an absolutely beautiful little pressure transducer from a bloke in Norfolk, and "Experimental Flash Steam" is on its way from the US, so the project is gradually gaining momentum!

From your photos it seems that you feed your gas unregulated to the burner. I've tried this on some hot air engines years ago, and had so much trouble that I gave the idea away. The combination of liquid gas and ultrafine jets was just too unmanageable.

I'm hoping to fire my boiler using propane regulated to 5 to 20 PSI and a burner of my own design similar to the one I use in my casting furnace. It fires horizontally, and produces a tangential swirl of flame which is great for the furnace, but I have doubts about how efficient such a burner configuration would be firing directly into a tube coil horizontally. Obviously it works, as evidenced by VB, but why is your boiler horizontal? Wouldn't the burner be more effective pointing straight up into a totally vertical tube coil? Daresay I'll get more answers when the book arrives ...

At least I shouldn't have the same gas problems as you fellas have up there at the North Pole, it's quite often 37 Deg C here downunder! But even in the dead of winter, my casting furnace burner puts out about 45,000 BTU/hr without freezing the bottle valve. It pushes the gas through a 0.9mm dia. orifice at 18 PSI.

Just finished the pattern for the cylinder of my engine today, and will probably pour it next week. More news then I hope.
Cheers,
George Z

Title: Re: Flash steam plant control.
Post by: Circlip on November 25, 2009, 02:19:53 PM
Cos of the various inputs to the control system Ian G is it not possible to put a Temp sensor on the gas tank and allow a system of bleed heat to the tank for cold weather ops??

  Regards  Ian.
Title: Re: Flash steam plant control.
Post by: flashtwo on November 25, 2009, 04:47:27 PM
Hi George,

Thanks for the info regarding thermistors - they would certainly be useful at the lower temperatures.

Regarding using the old 741 op amp - you would be able to amplify the feeble thermocouple signal but it would be difficult to compensate for the ambient temperature.

With your ambient at 37C, you would be developing a signal roughly equivalent to 63C, whereas with my ambient at 11C it would be equivlent to 89C. So you can see that a stable reference temperature is needed to make sense of the thermocouple signal.

The AD597AH most likely uses an internal thermistor to measure its own temperature, which it then adds to that received from the t/c and thus compensate for changes in ambient (to be pedandic, it should measure the internal temperature, convert it to the equivalent mV from the t/c, add it to the mV from the t/c and then convert it into temperature according to the t/c tables and referenced to 0degC - it is surprising that even some professional outfits don't do that).

The 0 to 5v output from the AD597AH connects very nicely with the PIC input and is represented internally 0 to 1023 (two bytes required).

Regarding the boiler attitude, I chose horizontal because of the lower centre of gravity. With the coil being bendable in any direction, you could have it horizontal and vertical in the same case or even as a toroidal shape.

I do regulate the gas flow to the burner. If the steam temperature goes up the PIC controller gradually closes the servo controlled gas valve and vice-versa. A new cylinder starts off at about 2.4bar (excuse the language) and I normally bring the boat in when it drops to 1bar, although I have run down to 0.6bar under these cold conditions knowing that is plenty of gas in the cylinder.

Alan Rayman, one of the "Experimental Flash Steam" authors, has seen VB going through its paces - it was an honour for him to be there.

I thought I was going back to basics, but to make your own patterns and castings thats well out of my league.

All the best
Ian G.
Title: Re: Flash steam plant control.
Post by: flashtwo on November 25, 2009, 05:23:36 PM
Hi Circlip,

In the early days (two years ago), I did  have a steam loop in a water bath containing the gas cylinder with a manually controlled steam valve. It worked fine, but in considering a automatic system, it started to get complicated in designing a "fail-safe" system that could cope with a stuck open steam valve.

I now follow the MPBA rules in not having any direct heating of the gas cylinder - I would rather put up with a reduction in performance in the winter than have a potential bomb on the water.

I was thinking of having some heating (as opposed to cooling) fins on the gas cylinder. This would be a passive system that would scavenge any ambient heat that was above the cylinder temperature and warm up the cylinder - a bit like a heat-pump. I've done some rough calculations regarding surface area etc.  With 20 fins of 50mm width and 105mm length (= cylinder height), I would get a five-fold increase in the cylinder external surface area. It will take up more room on the boat, but I think it will be worth trying.

But, saying that,  any ideas would be most welcome.

Ian G.
Title: Re: Flash steam plant control.
Post by: Fargo on November 26, 2009, 01:36:25 AM
Hi Ian,

thanks for the advice regarding coil config. and AD chip. I'm not an expert on thermocouples but apparently I should be able to achieve ambient compensation by using alumel termination lugs at the circuit board (for type K), which is what I've done. This is suposed to subtract the ambient mV from the measured mV. But more on this later.

I'm also in the throes of learning to program in MPASM, and obviously facing several large learning curves altogether. But it sure is interesting and a hell of a lot of fun.

Congratulations on your successes with VB, and like the other blokes, I'll be following with interest your next project.
Cheers, Georg Z
Title: Re: Flash steam plant control.
Post by: benjaml1 on November 29, 2009, 10:31:45 PM
Thermocouples:
As long as the cold junctions are isothermal ( + and - are at the same temperature) it doesn't matter what connection material is used as long as the final measured cold junction is compensated. However, for optimum design accuracy they should be of the same material as the conductor.

Check out the www.omegaengineering.com (http://www.omegaengineering.com) for some excellent technical assistance....
Title: Re: Flash steam plant control.
Post by: Fargo on December 04, 2009, 08:53:47 AM
Thanks  for the reference benjaml1,
but I've opted for using an IC, which will take care of things like cold junction compensation and linearity, and simply give me an analog or digital output to feed straight into my microcontroller chip. Meanwhile back to the drawing board and machineshop.
Cheers, George Z
Title: Re: Flash steam plant control.
Post by: benjaml1 on December 04, 2009, 12:09:25 PM
This maybe of interest......

(http://i18.photobucket.com/albums/b136/benjaml1/sc3.jpg)
Title: Re: Flash steam plant control.
Post by: Fargo on December 05, 2009, 08:40:41 AM
The engine I'm building for my test rig also uses an aluminium cylinder and a brass piston. It's a unaflow design with a spool valve. It'll be interesting to see how this combination of metals works out in practice.
The cylinder is already cast and partly machined,but the brass bits still need to be cast, and that's another story again ...........
Fargo
Title: Re: Flash steam plant control.
Post by: benjaml1 on December 05, 2009, 11:27:00 AM
Upon reading, numbers like 3000 psi & 18000 rpm stick out, engines don't last long under these conditions. Building an engine with survivability would not be a problem in this day of modern metallurgy. Pay special attention to the spool valve, stainless steel would be a minimum requirement unless "unobtainiums" are available. Stellite comes to mind....
Title: Re: Flash steam plant control.
Post by: flashtwo on December 05, 2009, 02:56:29 PM
Hi,

The whole point about the flash steam control system that I have developed is that is avoids the very high pressures and temperature that the traditional flash steam vessels operate under.

The Vital Byte runs very well at 30psi and normal saturation steam temperatures (plus a little bit of superheat), it is controllable, fuel efficient and uses normal engines.

Ian G.
Title: Re: Flash steam plant control.
Post by: Fargo on December 06, 2009, 03:57:52 AM
The engine I'm planning on using for my monotube test rig is a scaled up version of  #48 "Elmers Engines" on jon-toms.com website. Its actually a horizontal "mill" type engine which is relatively quick and easy to build and by no means an exotic, meant for high performance.

Up till now I've been fairly isolated regarding the modelling scene (25 years out in the bush), and consequently have very little experience with steam whatsoever, apart from building one small 2 cylinder vertical open column type with rotary valving, which runs beautifully. But having caught the "microcontroller" bug, I needed a simple, appropriately sized load to apply to my proposed boiler system, and the above engine seemed ideally suited.

I'm attempting to emulate Ian's project complete with low-stress parameters, with the ultimate goal of working it up into a
'lifesize" system suitable for a one-man canoe or fishing dinghy. Eventually I'd like to investigate the possibility of coupling a monotube system to a Tesla turbine ..........

Cheers,
George  Z
Title: Re: Flash steam plant control.
Post by: kiwimodeller on December 06, 2009, 09:13:33 AM
This maybe of interest......

(http://i18.photobucket.com/albums/b136/benjaml1/sc3.jpg)
Hi Benjaml1, can you please take a look at an earlier posting of mine and see if the engine in the picture you have posted looks anything like the engine in my posting? The thread was http://www.modelboatmayhem.co.uk/forum/index.php?topic=18582.msg196432#msg196432
I also spotted a similar engine on Ebay except that it had different valve gear but I missed out on it. If the article you have is about a similar engine I would appreciate a copy of the article either by email or personal message. Thanks, Ian V.
Title: Re: Flash steam plant control.
Post by: benjaml1 on December 06, 2009, 12:01:33 PM
Lots of info here & here....

http://www.onthewire.co.uk/hhistory.htm (http://www.onthewire.co.uk/hhistory.htm)

http://www.usfreeads.com/2048234-cls.html (http://www.usfreeads.com/2048234-cls.html)

There's also a high speed aluminium twin cylinder engine on E-Bay.co ( USA E-bay.)

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=230408339037&ssPageName=ADME:X:AAQ:US:1123 (http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=230408339037&ssPageName=ADME:X:AAQ:US:1123)


Title: Re: Flash steam plant control.
Post by: kiwimodeller on December 07, 2009, 10:47:19 AM
Great, thanks for the links. The motor on Ebay looks just like the one I have. I have ordered a copy of the Ebook and bookmarked the On the Wire pages. Thanks for your help. Regards, Ian.
Title: Re: Flash steam plant control.
Post by: flashtwo on January 20, 2010, 01:49:22 PM
Hi,

Just a quick note to say that "Vital Byte" will be on the Blackheath Model Power Boat Club stand (with many thanks to Steamboat Phil) at the "London Model Engineering Exhibition" this weekend.

Vital Byte will have the new AE-35 control computer installed.

The exhibition is at Alexandra Palace from Friday 22nd to Sunday 24th January - opens at 10am.

Looking forward to seeing a good number of "Mayhemers" there.

Ian.

Title: Re: Flash steam plant control.
Post by: flashtwo on June 27, 2010, 01:27:16 PM
Hi,

Well, as you can see from the "Steam Jet Engine" thread, "Vital Byte" has been on the back burner for a few months, but it is now being put through its paces in the test tank to flush out the expected software bugs.

V.B. now has a new controller (the AE-35 unit), a professional 5inch prop (Propshop) and  a 200 sq.inch monotube coil.

Having sorted out a few software bugs, I had trouble with some erratic behaviour akin to that caused by steam induced static electricity that I had in the very early days. Well, all effort was made to earth everything down, but the problems persisted. I finally traced it down to the servos that, when making large movements, were causing the supply volts to drop on the controller. The offending servos were moved to an existing servo power board that is supplied directly from the battery, thus stopping the interference on the AE-35.

Having finally got the controller sorted out, I then concentrated on the overall performance of the boiler and engine. I had noticed a lot of soot on the boiler coil indicative of poor combustion, also, when running with the gas valve open above 50%, there was the sound of an unstable burner.

With the experience gained on steam nozzles with the steam jet engine, I've just made and tested ( the sort of thing one does on the hottest day of the year) a Induced Draught nozzle that tees-off some steam from the coil just before the boiler exit. The steam is directed up the stack and greatly improves the draught resulting in a great increase  in boiler pressure and engine RPM. The engine speed has now increased from about 480RPM to higher than 700RPM (ahead and astern!), I say higher because the RPM code is currently limited to 700, but will be changed in the near future.

The substantial increase in RPM has been achieved inspite of using some steam for the Induced Draught nozzle and the beauty of the system is the higher the steam pressure the more draught is created.

As you can imagine 700RPM with a 5inch prop there is a lot of water sloshing around.

I suppose this method of induced draught can also be applied to those Mayhemers with conventional boilers.

Ian.
Title: Re: Flash steam plant control.
Post by: steamboatmodel on June 27, 2010, 10:43:02 PM
Hi Ian,
"I suppose this method of induced draught can also be applied to those Mayhemers with conventional boilers."
I think the train guys refer to this as a blast pipe, Blower, Petticoat or something like that.
Regards,
Gerald.
Title: Re: Flash steam plant control.
Post by: gondolier88 on June 28, 2010, 12:12:17 AM
Hi Flashtwo,

Yay, engineering I can relate to again!!! :-))

The way you have increased the draft is an elegant but inefficient way of doing it- you will be using excess steam, water and gas by using steam to induce a forced draft.

A better way to do it, especially at the speeds you have on your shaft, is to run a short layshaft next to the propshaft, just some 25mm conduit or similar, this would have the layshaft through it centrally, the layshaft would end in a small diameter (22mm-ish) three bladed coarse prop, this would then have a slight venturi down to 16-18mm pipe which would then 'T' into the funnel.

This is the way full size boats that ran on the edge of what reciprocating steam did, it uses far less energy than using steam does, and it's speed controlled, not pressure controlled.

The sooting could also be from when you first fire up and the pipe is cold- chilling a flame can also cause incomplete combustion, even if the fuel/air mix is correct.

Greg
Title: Re: Flash steam plant control.
Post by: flashtwo on June 28, 2010, 09:49:08 AM
Gerald,
I did consider using the engine exhaust steam with a blast pipe in the traditional way, until I witnessed a model steam tug at our local club.

As the tug chugged across the pond it left a trail of oil spots on the water and, as you know, they spread out to a size almost unrelated to the quantity.

It is not the sort of thing to explain to the local water bailif / enviromental officer ( he who walks around with a noise meter ensuring the i.c. boats are within the limits!).

Obviously it was the engine lub oil being chucked out the stack, so I decided to use the steam directly from the boiler - oil free.


Greg,
Thanks for the compliment. Yes, it was simple solution and was relatively easy to make and install especially for a monotube boiler where you just tee-in to the line. For a conventional boiler you would have to tee-in to the external steam line or put yet another tapping point on the boiler shell.

To keep the steam consumption low, I used a 0.7mm nozzle, which is far less than the steam ports on the engine itself. I made the nozzle inter-changable just in case the small one didn't work - it worked, so I didn't bother making a larger nozzle.

An intriging bit about the mechanically driven fan - was there any provision for when the engine was in reverse or didn't it matter for short periods and, also, are there any examples that one can visit?

 That's a good point about the sooting. I shall have to give the coil a good clean and see how things progress with the increased draught.

Ian
Title: Re: Flash steam plant control.
Post by: gondolier88 on June 28, 2010, 11:21:11 AM
Hi Ian,

I see your point about the nozzle, your consumption will be low, howevr it will still contribute, I'm sure with your skills you can probably time to the second how much shorter your runs are %)

The fan draft system was widely used on both high speed steam boats and most Navy and Merchant Navy boats. Some had dedicated 'fan engines', usually by Mumford's, even the small 50' picket boats had dedicated air tight boiler rooms and fan engines.

The prototype nearest to what your acheiving is probably the Thornycroft designed, Simpson & Strickland built 'Rose en Soliel', or 'Satanella', can't remember who built those two.

A few boats left with forced draft;

ST Canning- electric fan
SL Osborne- engine driven fan
SS Sheildhall- engine driven fan

Greg
Title: Re: Flash steam plant control.
Post by: flashtwo on June 28, 2010, 06:43:15 PM
Hi,

Talk about 2 revs ahead and 1 rev astern.

I just been testing the monotube boiler with its new steam Induced Draught (ID) gizmo and have run into a new problem.

The plant performs superbly at high steaming conditions, but when I run with a low feed flow to enable lower RPM the boiler now starts "hunting", i.e. the boiler pressure and temperature swing increasingly up and down until the high temperature trip shuts it down.

This happens quite slowly and I never had it before the ID nozzle was fitted. I suppose as the pressure builds up, more air is drawn into the boiler improving the combustion, which causes the pressure to increase even more. Then the engine accelerates, dropping the steam pressure and reducing the combustion. The engine slows down, then the pressure builds up thus repeating the cycle.

I've tweeked the gas valve controller to counter-act the swing. It has reduced the amplitude so the high temperature trip doesn't occur, but now the gas valve servo is having to work a bit harder.

Comparing Vital Byte's boiler to the steam jet boat's, it is obvious that VB's is too restricted on the air intake around the burner. Perhaps if I open up the intake fully then the swinging will stop.

Ian.
Title: Re: Flash steam plant control.
Post by: benjaml1 on June 28, 2010, 10:38:28 PM
Are you using 3 term ( PID) control or a reactive algorithm ?
Title: Re: Flash steam plant control.
Post by: flashtwo on June 28, 2010, 11:44:48 PM
Hi Benjamin,

I'm just using P & I (no D) coded in software.

I did set the temperature controller settings to minimum sensitivity and, even with the gas valve not changing its position and the feed flow constant, the swing would start.

This does imply that the feedback  mechanism is within the boiler design (i.e. with the ID nozzle fitted) and not in the control loops.

Giving my age away perhaps, what's the "reactive algorithm" that you mention? - sounds interesting.

Ian
Title: Re: Flash steam plant control.
Post by: benjaml1 on June 29, 2010, 10:10:37 AM
PID ( three term control) will work well as long as the required control band/range ( high & low feed) characteristics are reasonably linear.... If not, you will need two PID loops one for low range & one for high. This is called ( by Honeywell) reactive tuning. There are other programs out there which rely on "history", which memorise finite input parameters & set the control parameters for that situation after pumping them into a huge data bank. They are extremely expensive "Brainwave" being one...

My suggestion would be to search for programs that include "D" in the PID loop, failing that 2 PID loops as it would seem the control parameters are not linear across the full range....

This says it better than I can....

http://team358.org/files/programming/PIDControlTheory_rev3.pdf (http://team358.org/files/programming/PIDControlTheory_rev3.pdf)
Title: Re: Flash steam plant control.
Post by: steamboatmodel on June 29, 2010, 03:10:17 PM
I studied PID loops back when I did building maintenance, never thought I would have to think about it for model boiler control. I wonder if my notes from 35 years back are still relative.
Regards,
Gerald.
Title: Re: Flash steam plant control.
Post by: flashtwo on June 29, 2010, 03:42:18 PM
Hi,

Benjamin, you obviously have a control background - Honeywell Avionics?

I understand now, it is what I knew as adaptive control where the control terms varied according to the load of the system.

The other I knew as matrix control, where a data matrix held all the data throughout the control range and updated it under varying plant conditions.

I've never really used derivative (anticipation) control, because it amplified noise on the signal and could cause erratic control. I much preferred feed forward, which is what I use between the feed flow control loop and the temperature control loop; when the feed is increased the temperature set point is raised in anticipation of the temperature dropping and vice-versa.

I was thinking of varying the temperature control loop control terms relative to the gas valve opening value; it would be a simple linear relationship rather than an additional PID loop.

Gerald,

Yes, exactly the same principles are involved. You measure the thing you are trying to control, compare it with a desired value and then adjust an actuator which controls the thing you are measuring. It doesn't matter whether its the H&V of a building or a missile control system.

Apologies to all other Mayhemers who haven't a clue what what we are talikng about.


Ian
Title: Re: Flash steam plant control.
Post by: gondolier88 on June 29, 2010, 05:53:15 PM
Apologies to all other Mayhemers who haven't a clue what what we are talikng about.


Ian

Thanks!!! :o

Give me springs and diaphragms any day!

Just joking, I for one, and I'm very sure I'm not alone here, respect your take on what is a most versatile and dynamic part of model engineering/mosel boating, and you never know what else these control systems may one day manage...

Greg
Title: Re: Flash steam plant control.
Post by: benjaml1 on June 29, 2010, 06:15:11 PM
Thanks!!! :o

Give me springs and diaphragms any day! Greg

Interestingly enough PID control systems were made/functioned using springs/bellows/restrictor & levers in the good ole pneumatic days...Well before micro processors & are still in use all around the world...  :-))
Title: Re: Flash steam plant control.
Post by: gondolier88 on June 29, 2010, 08:35:09 PM
Ahh, i'm stuck in the good ole days, I don't feel so bad now :-))

Greg
Title: Re: Flash steam plant control.
Post by: benjaml1 on June 29, 2010, 11:02:46 PM
I have been offered a position with the nuclear energy peeps, not based on my neuvo technical intellect but my archaic knowledge of so say redundant pneumatic control systems...  :-))

Tried retirement & found that boring, 61 years old & going back to work...EH! I love a challenge    :-)

May be able to buy more steam goodies now...  ok2

Title: Re: Flash steam plant control.
Post by: gondolier88 on June 29, 2010, 11:36:22 PM
I see, so our 21st century powerstations recognise that steam should be mechanical not electric, but us model boaters think better, Mayhem to a 'T'! {-)

Greg
Title: Re: Flash steam plant control.
Post by: benjaml1 on June 30, 2010, 08:53:47 AM
I see, so our 21st century powerstations recognise that steam should be mechanical not electric, but us model boaters think better, Mayhem to a 'T'! {-)

Greg


 {-)  :-))
Title: Re: Flash steam plant control.
Post by: flashtwo on June 30, 2010, 09:30:20 AM
Hi,

Wasn't it annoying when you found that tiny hole drilled in the flapper caused by the fine rust particles in the compressed air - it always used creep up unexpectantly.

Honestly, the old pneumatic systems were superb in a hostile environment of heat, humidity and dust and IF the compressed air was maintained to good quality they would last for years unattended, but the slightest bit of damp air and the compressed airlines would rust internally and you would be on the downhill path.

I started my career in a small power station that had no electronics at all, not even thermionic valves - it was purely hydraulic and pneumatic and, if you talked about using electronics, the old guard thought you were from another planet!

Saying that, despite all the computing power, the last link in the chain is still the hydraulic/pneumatic actuator though increasingly being replaced by electric actuators.

Can you imagine one of the old Taylor controllers on a model boat! No.

All the best

Ian.
Title: Re: Flash steam plant control.
Post by: flashtwo on July 08, 2010, 08:26:02 AM
Hi,

Just to let you know that "Vital Byte" will be displayed and demonstrated at the Guildford Model Engineering Society steam rally this weekend, 10th & 11th July, 2010.

This V.B. will have its new control system and other modifications in operation.

See http://www.gmes.org.uk/find.htm for details of the Society's location.

Hope to see a few Mayhemers there as usual.

Ian.
Title: Re: Flash steam plant control.
Post by: flashtwo on July 11, 2010, 08:20:44 PM
Hi flashsteamers,

New failure mode!!!!@~###

Yesterday and today at the Guildford Steam Rally, Vital Byte was put through its paces, but only for about 10-15 minutes.

Yesterday V.B. experienced a heavy clunking sound after about 10 minutes of near silent running. The sound seem to come from the prop shaft rather than the engine, but finally the power train seized and the boat was hauled out of the water.

I removed the cylinder covers and, although one piston needed tightening slightly, there was no apparent engine problem. I then found the prop shaft shear pin had fallen out after over a years service. I replaced then pin but found that the shaft seized at certain positions, but, if I lent on the stern, it would free up. I concluded that the very hot sun ( it was 31degC!) had caused the hull to warp during it's open air display.

Today I ensured that the shaft would turn whilst it was on diasplay and everything was ok. Then after several hours it was time for a pool demo and again after about 10 minutes of perfect running the shaft seized again!

What a puzzle.

Suspecting the pool water temperature, I put my max/min thermometer (its amazing what useful junk one carries) in the pool and recorded 27degC! The only thing I could think of was that I have some reiinforcing aluminium strip under the stern that was expanding and causing the hull to "hog", thus causing mis-alignment of the engine to prop shaft coupling. Normally, I run V.B. in the local lake where the temperature is quite low thus avoiding this problem.

Solution: open up the gap on the dog-tooth coupling to increase its tolerance.

There was another chap there with a tug powered by a D10 engine and his loc-tighted prop became loose on the prop shaft - whether this was to do with water temperature, I don't know.

Ian.
Title: Re: Flash steam plant control.
Post by: flashtwo on July 15, 2010, 12:42:08 PM
Hi,

Here is a photo showing the fully tested and working AE-35 controller now being used on Vital Byte. With it is last years somewhat larger prototype and a 4inch piece of 7/8th brass for scale.

The AE-35 has basically the same functionality as the prototype, but uses smaller PICs for the pumps and engine RPM processing. The display processing and control functions are each in their dedicated 16F877s PICs and the PICs talk to each other via a serial link that enables a lot more data sharing.

The AE-35 still has the capability of being re-programmed and has had it's software code tidied up and simplified in parts. Having a dedicated display PIC gives a more reliable response to the push buttons located on the operator's control console.

Ian.
Title: Re: Flash steam plant control.
Post by: benjaml1 on July 16, 2010, 11:52:48 AM
Impressive....  :-))
Title: Re: Flash steam plant control.
Post by: flashtwo on July 17, 2010, 09:15:31 AM
Thanks Benjamin...

No sooner was the AE-35 unit in V.B. then it was out for another software mod.

With the old system I could have the desired steam temperature set by the steam pressure, via an equation, to give the steam saturation temperature appropriate to the prevailing pressure. It did, however, suffer from instability if the steam demand suddenly changed causing the pressure to change and consequently the desired steam temperature.

The latest mod links the desired steam temperature with the desired feed flow (set by the radio transmitter). As the desired feed flow increases, it is anticipated by the controller that the steam and pressure will increase with an appropriate increase in saturation temperature. If the heat input isn't increased accordingly, then wet steam conditions would be experienced.

The new mod addresses this problem by adding a proportion of the feed demand value as an offset on the manually set desired steam temperature. Since the feed demand is a constant, though manually adjustable, the system is stable in its operation.

Next project a computer controlled flash steam calliope? Then I could really start playing some tunes on it!

Ian.
Title: Re: Flash steam plant control.
Post by: benjaml1 on July 17, 2010, 11:12:36 AM
It amazes me the level of technology that has found it's way into steam model building. I'm still in the stone age.... :embarrassed:
Title: Re: Flash steam plant control.
Post by: steamboatmodel on July 17, 2010, 06:10:19 PM
It looks impressive. I haven't used a 16F877 PIC yet, I am still working out the basics (in assembly and C ) with a PIC 2 starter Kit with the 16F690 pic. I also have a 16F627, 16F628 to play with once I get them down I will then advance to a 16F886 28pin pic and then the 16F887 44pin pic. So far I have done the "Hello World" bit and got the leds to flash without letting any magic smoke out, my next step is to do servo positioning and reading RC signals.
Regards,
Gerald.
PS It was much easier learning things forty years ago when I was in my twenties. Then I would write notes and remember things without having to look at the notes, now I not only have to write the notes, I have to remember where I put the notes and the right glasses to read them.
Title: Re: Flash steam plant control.
Post by: flashtwo on July 19, 2010, 08:07:39 PM
Hi,

Vital Byte produced her best performance yet at the Blackheath Club meeting on Sunday.

The meeting was really for the straight runners, but Steamboat Phil encouraged me to get V.B. out on the water before the competition started.

Before launching, V.B. had the honour of being inspected by Alan Rayman one of the authors of "Experimental Flash Steam" - I hope he approves of the modern technology!

Several of the members were proud owners of Alan's boilers and engines, some being 30 years old or more.

All the changes made to V.B. over the last six months came to fruition - a good quick start and then she was off with her new prop, new computer and new boiler coil.  I gradually pushed her up through the power range, by remotely increasing the feed, to a very good speed and fine hull waves. She did many full power change-overs from ahead to astern and back with the engine accelerating to 730RPM during the change (maximum recording is working ok now);  not bad for a 72lb displacement hull shaped like a box. The average RPM for the run was 480.

A couple of mid-pond shut-downs were made and she auto-restarted on both occasions. Three point turns - no problem.

A second successful run was made in the afternoon, though with one minor problem of the feed inlet plastic pipe coming adrift and causing her to ship water; I had inadvertently dislodged the pipe when installing the lead ballast. Despite the minor hic-cup, Steamboat Phil and his son took a video for one of Phil's talks on flash steam.

One remaining problem - I've now got to build a proper boat!

Ian
Title: Re: Flash steam plant control.
Post by: SteamboatPhil on July 19, 2010, 11:37:10 PM
A good day was had by all at Blackheath on Sunday, with Vital Byte steaming around most of the day.

Here is Vital Byte in action  :-))
Title: Re: Flash steam plant control.
Post by: flashtwo on July 20, 2010, 09:53:09 AM
Thanks very much Phill for the photo - its always a bit difficult to operate the transmitter and take photos at the same time.

Its very interesting to see the hull wave, it seems to be one complete wavelength, which may indicate that the boat is travelling at hull speed.

I've got very limited knowledge in that area, so I would be very appreciative of any comments regarding hull speed waveform from Mayhemers with that experience.

Ian.
Title: Re: Flash steam plant control.
Post by: SteamboatPhil on July 20, 2010, 11:40:23 AM
Here you Ian a slightly better bow shot  :-))
Title: Re: Flash steam plant control.
Post by: flashtwo on July 20, 2010, 12:08:10 PM
Thanks Phil, that's much better.

It looks like one trough behind the bow followed by one crest before the prop, i.e. one wave length.

For those not familiar with the boat, there is a large overhang above the water after the prop (see earlier posts at last year's Guildford Show), which gives the appearance of a much longer hull.

Now, is the hull speed indicated by one wave length or one half wave length?

Ian
Title: Re: Flash steam plant control.
Post by: flashtwo on August 21, 2010, 02:42:45 PM
Hi,

I’ve just fitted an oil/water separator and combined feed heater on Vital Byte and tested it with further improved results.

The separator is a vertical brass cylinder 1.75inch diameter by 8.5inch height. Within the cylinder, I've fitted a copper coil 5/32 by 100 inch which gives approx. 50sq.inch of heating area (steam exhaust side).

The exhaust steam /oil enters near the top and condenses on the exposed section of the coil. The drain is located at the bottom and exits above the water-line, the exit height determining the water level in the separation tank. The coil carrying the boiler feed water enters near the cylinder top, passes through the exhaust steam section then into the hot water on top of which lays the separated engine oil.

One problem with the previous exhaust steam collection arrangement was having to manually pump the water/oil out every 20 minutes of running time - with the new arrangement the boat will only be brought in to top up the displacement lubricator having dumped excess (oil free) water overboard.

The unit has been operated on the test pond with the drain water  free from oil and the feed water temperature rising to about 70degC before entering the economiser coil located in the stack.

The economiser outlet temperature is now about 147degC which indicates steam production since it is above the saturation temperature.

The efficiency has improved a lot since the gas valve is only having to open to 48% instead of 100% to achieve an average RPM of 612 over a 18 minute period.

I shall try and take some gas consumption readings on the lake tomorrow.

One thing I’ve got to understand now, is that the inlet temperature to the main boiler coil is 147degC, whereas the boiler outlet steam temperature is 131degC!


Here's a couple of photos.

Ian.
Title: Re: Flash steam plant control.
Post by: flashtwo on November 24, 2010, 10:30:19 AM
Hi Mayhemers,

Vital Byte has been performing very well over the past few months with the oil separator / feed heater preventing oil from poluting the lake.

Since there is now no condenstate tank to empty every 20 minutes, extended runs of 40 minutes without returning to shore are a regular feature.

With a view to building a “proper” boat, I’ve started construction of a vertical boiler to match the scale of an Edwardian Steam Launch that I have the plans of.

 The new vertical boiler is unusual (like everything else in this project!), in that the boiler coil extends up through the furnace and into the 2 inch diameter stack. In this way it will have 200sq.inches of copper-to-water surface area plus the 50sq.inches in the feed heater gives a total of 250 sq.inches.

The water will enter the coil at the top of the stack and steam will exit the coil at the connector located at the bottom of the furnace – how different is that!

To ease the removal of the boiler, connections have been kept to a minimum. The safety valve (not legally required) and the pressure and temperture tapping points have been removed to their own manifold separate from the boiler. The only connections left are the feed inlet, steam outlet, pilot gas and main burner gas – no sight glass or level measurement is required.

The first photo (DVD for scale) shows the skeleton of the boiler prior to attaching the coil and heat shield. The second photo shows the steam outlet to manifold arrangement.

The vertical boiler is in fact the same height of the current horizontal boiler.

After initial trials it is planed to encase the boiler in the traditional wood and brass banding.

Ian.
Title: Re: Flash steam plant control.
Post by: steamboatmodel on November 24, 2010, 03:50:26 PM
Hi Ian,
You say "The water will enter the coil at the top of the stack and steam will exit the coil at the connector located at the bottom of the furnace – how different is that!"
Would not the steam rise to the top of the coil?
Regards,
Gerald.

Title: Re: Flash steam plant control.
Post by: flashtwo on November 24, 2010, 05:29:08 PM
Hi Gerald,

That's a very good point and well worth the experiment.

One thing with the monutube or flash boiler is that the feed water is continuously pumped in under pressure, which has to be slightly higher than the steam pressure to maintain flow, so hopefully that should discourage the steam from rising to the top.

Another feature is the effective tube gradient.  As you can imagine the tube sprials down from the top over a vertical distance of 405mm. The tube length is in the order of  12 metres and so the effective gradient is about 1 in 30 and as you might have experienced with a steam or air lock in a long pipe they can be difficult to shift by natural circulation.

The reason for pumping water in at the top is to maintain the highest temperature difference between the combustion gases and the water/steam in order to maximise heat transfer.. The coldest part of the boiler is at the top, so that is where the cold feed enters, and the hotest part is near the burner where the steam exits. The water/ steam spirals down from the cold to the hot end.
 
Anyway that's the theory - we'll find out what happens in practice!

Cheers

Ian
Title: Re: Flash steam plant control.
Post by: ooyah/2 on November 24, 2010, 07:56:20 PM
Hi Ian,
I would have no fear of air locks, your coil is wound in spirals with no sharp corners.
Your coil is similar in construction to my flash steamer with the water going to the cold end and my coil is lying horizontal but in yours with it being vertical the pressure created by the pump and the heat generated will turn any air bubbles into steam along with the air already in the coil.
Any condensate in your cylinders will be shoved out as soon as the valve is opened to the steam.

I am puzzled as to what the large dia tube going up into the funnel is, have you considered making your coil wider to fit into the shell case and then reducing up into the funnel, you could then use a ring burner or a large ceramic one, just a thought.
I look forward to hearing your results, the mechanical ones not the electronic ones !!!

George.
Title: Re: Flash steam plant control.
Post by: gondolier88 on November 24, 2010, 09:30:08 PM
Hi Ian,

I have to say your idea re. the feed arrangement, though based on sound theory, isn't based on practice, as I'm sure your aware.

The reason the cold water is injected at the base is to make ful use of natural convection- the steam engineers bedfellow, our hobby wouldn't exist without it.

I would suggest you think carefully about your coil arrangement- if you are looking to make the most heating surface in the space available then why not use a 'twin' coil arrangement- an inner and outer coil?

The outer, say 5/16", tube would be a coil of a fairly flat gradient, taking the cold feed from it's base where it would flash and rise to what I would propose is a stainless 'header', which would the connect to an inner steeper coil of say 1/4" tube that takes the now very dry steam back down through the products of combustion, through the flames and the I would really suggest that you again make use of convection and take the steam outlet back up, through the center and have the outlet at the top of the boiler.

This would make a very compact heating exchanger, but very high heating surface and very dry, very hot steam!

The full size monotube boilers I've seen all use this method, along with every twin coil heat exchanger I've come across.

I very much look forward to seeing this launch make progress- what plans are you using- have you found some original Georgian ones or is it one of Selway Fisher's?

Greg
Title: Re: Flash steam plant control.
Post by: kno3 on November 24, 2010, 10:18:24 PM
This is a really interesting project and I am thinking about building such a coil boiler too. Do you hink it could work on a much smaller scale? In a size of about 10 cm length and 7 cm diameter?
Title: Re: Flash steam plant control.
Post by: flashtwo on November 24, 2010, 11:45:40 PM
Hello George,

The centre 15mm copper tube serves two purposes -

1) The feed water connector is located at the bottom diametrically opposite the steam outlet connector and the feed will be directed through a 4mm pipe up inside the 15mm copper pipe to the top of the stack  from whence it spirals back down. Taking this route means it doesn't interfere with the return pipe spriraling down.

2) The gap between the spiral layers needs to be maintained for good heat circulation, so the 15mm pipe will be drilled to accept 1/8th inch copper pipe sections to act as spacers. The lowest spacers are stainless steel (for strength) rod inserted through copper pipe, which will support the weight of the coil.

When I start the system, I always flood feed right through to the cylinders and, since I have not throttle valve between the boiler and engine, as the steam is raise the feed is blown out of the cylinders (I toggle the reversing gear) and the engine warms up with the boiler, i.e. there is no sudden shock of high temperature steam.

I can see what you mean by having a ceramic burner. The design could be changed so the 15mm pipe terminates higher up and leaves room for a ceramic burner.

Are ceramic burners rated by their gas through put? - I've been aiming for 7 grams/min, though I'm getting very performance at 4 grams/min.

I shall post photos as the construction progresses.


Best regards

Ian.
Title: Re: Flash steam plant control.
Post by: ooyah/2 on November 25, 2010, 12:18:12 AM
Hi Ian,
Gotcha, as the coil is vertical with the heat being put into it the coils could start to slip down and prevent the heat circulating between the coils, so you St/St rods keep them apart, good idea.
Not sure about the gas consumption with ceramic burners but any that I have made work very well on a No5 jet, here is a pic of one with a No6 jet below a vertical multitube boiler 4.5" dia x 6" between end plates.
I have never been very concerned with the gas consumption as I refill the camping gas cans with Butane fro a 4.5kg bottle, this of course is used in my steam tug not the flash steamer, it has three burners with .025" jets pressure fed from the engine and uses about 3/4 pint of fuel per 4 mins.

Are you going to computerise the boat as the previous one?

George.
(http://s1.postimage.org/1hbqe3h38/Vertical_boiler_1.jpg) (http://postimage.org/image/1hbqe3h38/)

(http://s1.postimage.org/1hc1yuwjo/Vertical_boiler_3.jpg) (http://postimage.org/image/1hc1yuwjo/)

(http://s1.postimage.org/1hc8l0ais/Vertical_boiler_5.jpg) (http://postimage.org/image/1hc8l0ais/)

(http://s1.postimage.org/1hcbw2zic/Vertical_boiler_6.jpg) (http://postimage.org/image/1hcbw2zic/)
Title: Re: Flash steam plant control.
Post by: SteamboatPhil on November 25, 2010, 09:29:21 AM
Nice job Ian, can we have than on the stand at Ally Pally as well ?   :-))
Title: Re: Flash steam plant control.
Post by: flashtwo on November 25, 2010, 09:32:52 AM
Hi Greg,

The lower part of the coil will be constructed in three layers and the part in the stack will be a single layer in contact with the brass tube. The three layer section is wound with a 3.5mm (on average!) gap between the 22 spirals and with the vertical separation maintained with sections of 1/8th inch copper tube. I have a spread sheet that I can input the heating area required, tube size, gap size etc.,  and it calculates the overall dimensions of the boiler - so I can play around with the numbers to get the boiler shape that I require.

On my steam jet engine project (see the other thread) I used a 5 layered coil and I did achieve steam temperatures in excess of 720degC - yes the silver solder did melt!

I think with the horizontally coiled flash boilers, that I’ve been using, couldn't have had much natural circulation, since any density variation causing circulation must have been cancelled out along the length. In a normal boiler, as you know,  the circulation occurs between the lower headers and the drum and requires lots of relatively large diameter tubes. With the monotube flash boiler with a small diameter tube the flow relies on continuous feed pumping to maintain flow through the narrow tube. Anyway, its all part of experimental fun, which, if it is successful, could be applied to larger vessels – all part of modelling I suppose.

I have been wary of using any “header” in the system, since it might constitute being a pressure vessel, which is what I’m trying to avoid with all the testing etc.

Yes, I’ve got the Selway Fisher Edwardian 30 foot launch plans and their detailed booklet on strip planking techniques. I’m aiming to use the 5 inch prop that’s currently installed in Vital Byte. The boat is planned to be of  75 inch length  and the boiler is scaled to fit. I’ve never tried strip-planking before, so its back to the bottom of the learning curve!

Ian
Title: Re: Flash steam plant control.
Post by: flashtwo on November 25, 2010, 09:35:43 AM
Hi Kno3,

I can’t see any reason why smaller versions couldn’t be made. The required copper-to-water (not combustion gases-to copper) surface area needs to be converted into tube length knowing the tube diameter and wall thickness. The are many ways of coiling the tube:-

1)   Single layer results in a long boiler
2)   Multilayer results in a short boiler
3)   Layering the coils by starting at one end on the inner coil over a former then returning the opposite direction over another former (i.e. a strong plastic tube that slides over the inner coil) and repeating this for the number of layers required. The only problem with this arrangement is that you end up with several very hot spots each time the coil approaches the burner.
4)   Making the layers by spiralling out from the centre to the rim, thus making a spiral “disk”, then moving up to the next disk and spiral in from the rim to the centre and repeat until the number of disks is achieved. This takes a bit more skill, but it means that the coil gradually moves from the cold end to the hot end without the hot spots of the method 3) above.
5)   Figure of 8 is used a lot by the traditional flash steam tethered boat fraternity.


Ian
Title: Re: Flash steam plant control.
Post by: flashtwo on November 25, 2010, 09:36:45 AM
Hi George,

I’m only using copper covered stainless steel supports at the bottom and the rest are copper tube spacers. I’m trying to avoid contact of steel against the copper boiler tube to avoid corrosion.

Blimey! that’s a lot of fuel you’re using on your flash boiler it must go like a rocket. On my steam jet engine I’ve been using 25 grams/min of gas and I thought that was a lot.

Yes, this will also be computerised. The computer based controller will simply unplug from Vital Byte and plug into the new model, though I might have to tweak some of the control settings (via the keyboard) for the new boiler depending on how it raises steam in comparison with the current horizontal boiler.

Thanks for the photos. The stack is a little bit smaller diameter than mine, eh! What device is the V10 driving – is it a generator?

Ian.
Title: Re: Flash steam plant control.
Post by: flashtwo on November 25, 2010, 09:48:33 AM
Hi Phil,

Yep, it will only be installed in Vital Byte for test purposes come Ally Pally - no sleak mahogany steam launch as yet I'm afraid.

I'm still working on the steam jet boat, though the vertical boiler is the priority at the moment, and I hope to have that at Ally Pally as well, if you can find some extra table space; I've an idea about converting it into a turbo-steam jet that drives the boat's propellor, if the direct water drive doesn't come up with the goodies.

I'll be seeing you at the Model Enigineering Exhibtion Sandown in December - I've not been there before.


All the best
Ian
Title: Re: Flash steam plant control.
Post by: ooyah/2 on November 25, 2010, 11:43:58 AM
Hi Ian,
Yes my flash steamer can go !!!!!

If you recall I posted some info http://www.modelboatmayhem.co.uk/forum/index.php?topic=24568.0 on my flash steamer OOYAH with some pics of the new engine build. At the time I didn't know how to post pics of the boat in action so here are some.

(http://s3.postimage.org/1h5cj3ydg/OOYAH_at_speed.jpg) (http://postimage.org/image/1h5cj3ydg/)

(http://s3.postimage.org/1h5mgc1c4/OOYAH_2.jpg) (http://postimage.org/image/1h5mgc1c4/)

(http://s3.postimage.org/1h5t2hfb8/Ooyah_2_1.jpg) (http://postimage.org/image/1h5t2hfb8/)

(http://s3.postimage.org/1h5wdk4as/Ooyah_2_2.jpg) (http://postimage.org/image/1h5wdk4as/)

The speeds of OOYAH in these pics are unknown but 40 mph + isn't far off.
If you look at the wake on the last pic you will see that it takes a hard left and then a hard right followed by a hard left back on course.
This was caused by a radio glich and through that experience I have retired the boat at present as it's becoming a bit dangerous, I keep thinking WHAT IF it shot out of the pond and hit somebody.

The 10V is linked to a reversing gear box which although worked great on the bench once in the boat I couldn't rely on it with the 10V not being self starting it was a pain to get the waders on to rescue it.
I tried extending the shaft on the gearbox to link a geared motor to turn the slip eccentric over when the engine stopped, again not 100% so a D10 will be machined up this winter for the tug.

(http://s3.postimage.org/1h8qwvmx0/G_Box_drive_1.jpg) (http://postimage.org/image/1h8qwvmx0/)

Keep up the experimentation even if the end result don't work, it only makes one more determined to make it work.
George.
Title: Re: Flash steam plant control.
Post by: ooyah/2 on November 25, 2010, 11:52:28 AM
Ian,
I forgot to say that to attain these speeds with a steamer you need A LOT OF FUEL  & A LOT OF HEAT and the nerves to hold on to it.
George.
Title: Re: Flash steam plant control.
Post by: Patternmaker on November 25, 2010, 04:04:14 PM
Thats very impressive George, I had no idea that you could attain those sort of speeds with steam.

Mick
Title: Re: Flash steam plant control.
Post by: ooyah/2 on November 25, 2010, 04:52:40 PM
Hi Mick,
If you think my boat is fast have a look at this http://www.youtube.com/watch?v=hVN8iHfQl3s this is the engine that I copied, Bob's hydro is the world record holder at 120 mph, possibly faster since this video clip was made.
George
Title: Re: Flash steam plant control.
Post by: gondolier88 on November 25, 2010, 05:25:35 PM
I knew someone used a proper monotube full size- you might be interested;

www.steamboat.org.uk/register/html/tani0866.htm (http://www.steamboat.org.uk/register/html/tani0866.htm)

The edwardian 30 is a lovely launch, I prefer the plumb stem to the clipper full size, but it's all personal preferance.

Greg
Title: Re: Flash steam plant control.
Post by: rathikrishna on December 01, 2010, 09:37:59 AM
Good evenig, Sir, can we use any EPROM ics for this purpose..?  its amazing work indeed, and i am willing to make a simple one..will you add some good videos here..?  its a request..
Title: Re: Flash steam plant control.
Post by: flashtwo on December 02, 2010, 06:44:50 PM
Hi Rathikrishna,

I'm currently using Microchip's 16F877 and 16F819 PIC micro-controllers. These particular ICs contain digital inputs and outputs, analogue inputs, program memory and EEPROM data memory. All of the input and output channels are required to interface with the radio-receiver output, servos, temperature probes and pressure sensors.

Ordinary EEPROMs would, most likely, only contain programming or data memory with no input or output capability.

Ian.
Title: Re: Flash steam plant control.
Post by: flashtwo on December 02, 2010, 07:20:46 PM
Hi Mayhemers,

The vertical boiler is progressing with the coil wound and fitted in the main furnace and stack.

The winding started with a single 10 metre length of 5/32 inch, which went well for the first part, but got mildly out of alignment further along. At the base of the stack a joint was made with another 3.3 metres of the same diameter to give me the 200 sq.inch of area. The 3.3 metre was single layer coiled and fitted in the stack (just!).

I managed to fit some copper spacers in the lower section, but realised that pushing the spacers in for the entire height would exceed the height available; oh well, I shall to design some special former to help in the future.

The boiler was temporarily fitted into the boat with feed and steam pipework connections made. The feed pump was ran to pressurise the system and check for leaks. One leaking joint was repaired and the cold hydraulic test past.

The boiler has been removed and had a stainless mesh fitted a short gap from the coils, then 3mm insulation and finally thick tin-foil was wired into place.

When the 2 inches of ice has melted on my test tank, and the 15 inches of snow has been cleared, I shall attempt to make steam and have an engine run.


The attached photos show the supports (copper tube covered stainless) to prevent the coil collapsing into the combustion chamber (please excuse the rather ragged hole , its been tidied up since), the copper coil and the attempted spacers.




Ian
Title: Re: Flash steam plant control.
Post by: rathikrishna on December 04, 2010, 02:01:10 PM
Sir..sure you are one too informative...and too sad that you are living far to me...oh..oh...any how i am trying with some ideas, with eprom, but in my country i can only get some PIC controlers for this purpose...any how its amazing that your posts...ah...i need a detailed study about your postings, but its too hard to come here in internet cafe 30 kms from my home...but at any instance i will crawl through your postings and will study some thing to me as i started my steam stuff from put put boat...so god may bless you..and video...?  any hope...with great respect..Rathi
Title: Re: Flash steam plant control.
Post by: gondolier88 on December 04, 2010, 06:06:06 PM
It's easy to forget how lucky we are in our country sometimes- I think I must echo a lot of members thoughts when I say you are a credit to the hobby Rathi.

Keep it up!

Greg
Title: Re: Flash steam plant control.
Post by: rathikrishna on December 05, 2010, 06:25:22 AM
Good morning..and Sir..yes sure..all you are much fortunate...if you have any idea to do..all needed stuffs with you, as i buy 1 kg sugar from my nearest shop...but here if i want o do anything...must start from scratch...yes its more satisfying...but i do not have any ample muscle power to do big things...and fun..people always make fun on me as mad, as i wander through all junkyards and scrapyards to collect some usefull stuffs...and i always wonder while reading many posts here in MBMH , as each and every one is far beyond imagination and rate of work...what for more.. now we are submerged a stuff like these...now i am in my workshop to make a coiled engine by seeing that video in youtube yesterday...and i have a detailed study of this stuff ,because its too amazing and sure work of a lifetime...ahhh....
Title: Re: Flash steam plant control.
Post by: ooyah/2 on December 05, 2010, 06:56:06 PM
Hi Ian,
Just having another look at your coil, you seam to have more tube in this one than the old coil.
At 13.5 m (43 ft) is quite a length of coil. how does the new one at 250 sq" heating surface compare with the old one and if it's greater are you trying for more steam ?
Do you think that the coil being as tightly coiled you will get convected heat up through the coil with so little spacing and the plumbers type burner that you are using.
In my early experiments with a st/st coil wound as per Benson& Raymand   Experimental Flash Steam with the outer coil wound around the inner which left very little space between the coils I found that I couldn't get enough heat through the coil which was about 22 ft long and using a roaring type burner pressure fed from the engine and it had a .018 " jet I just couldn't get the boat to perform.
I then cut out the inner coil and rewound the outer coil and welded it to the inner giving a straight through coil which instantly produced a 20 mph boat.
My empirical deduction was that the flame was now getting all around the coil producing more heat.
My new coil is 32ft long wound around a tapered mandrel and with the three burners produces volumes of High pressure High temp flash steam, there is at least 1/4" space between the coils

Now I know that this isn't what you are trying to achieve but don't you think that with a shorter coil and more space between the coils and using a ring burner that you would get a better performance from your coil and still retaining the O/All  dimensions of your boiler.

Ian I hope that you don't think that I am trying to tell you what to do, it's just some thoughts from my early experiments.

Another thing I found was that I opened up the exhaust outlet and again when the gases were allowed a bigger escape rout achieved a better burn.
The exhaust outlet on the pic is the old one before I made the outlet much bigger.
Regards
George.
 
(http://s4.postimage.org/2p6616otg/006_coil_2.jpg) (http://postimage.org/image/2p6616otg/)

(http://s4.postimage.org/2p7gc8en8/Flashboiler_1.jpg) (http://postimage.org/image/2p7gc8en8/)
Title: Re: Flash steam plant control.
Post by: flashtwo on December 05, 2010, 08:15:05 PM
Hi George,

I really appreciate your experience in the matter of coil "density".

I agree with you that there may not be enough circulation of the combustion gases and the combustion chamber may get pressurised, such that we have blow-back of the flame - I'll find out during the tests. I'll order some more copper tube and use half the length (I would loose 75sq.in.) for additional tests, - it all adds to the empirical database!

As the boiler is more of a monotube rather than a high performance flash, I might (hope!) get away with a more gentle application of heat - did you ever estimate the combustion exhaust temperature of your flash boiler; with my horizontal boiler it was about 220degC, but it came down to 170degC with the economiser fitted.

On the horizontal boiler, I started with a 1 inch dia. stack and couldn't maintain combustion for any length of time, but when I increased the stack to 2 inch dia. every thing settled down with the increased ventilation. I started with 84 sq. in. and gradually increased the area to 200, principally because I met a chap at the Guildford Show who had 164 sq.in. conventional boiler steaming his D10. I did find that this made a great difference in performance.

The 250 is the sum of the 200 in the boiler plus 50 in the feed heater.

The external boiler dimensions are to the scale that I need for the Edwardian steam launch I'm planning to build, so that part of it is effectively fixed.

So, that's my starting point with the vertical boiler and I will "unwind" the coil as necessary.

With my steam jet engine the coil was wound even tighter than this vertical boiler, I used all the steam output through a nozzle and blower, which that drew a tremendous combustion gas flow through the coils - it did melt the brass components though!

I did try using a blower on the horizontal boiler - it did increase the performance, but caused the steam temperature to cycle.

As with the horizontal boiler, I can see myself winding many more coils (I ought to unwind some of the old ones!).

Thanks for your interest George and sorry to hear about your shattered part of the D10.

Ian.
Title: Re: Flash steam plant control.
Post by: ooyah/2 on December 06, 2010, 09:13:28 PM
Hi Ian,
I have been thinking about your Monotube today, I have had plenty of time as we had 8" of snow dumped on us in 3 hrs this morning and that's on top of the 18" we already had and it's too cold for the workshop.
Unfortunately you are in an area similar to myself when I started out on my experiments, you to a certain extent are doing what very few have done before you so you plow a lonely furrow.
I can only comment as before that I think that your coil is too tightly wound but as you have already made it why not experiment further and see what happens, so I will watch with anticipation to see how you get on before I start.
You mention that you have melted s/solder joints, in my early experiments with copper tube I tried to keep any joints away from direct heat and wound stripe of ceramic wool  boiler cladding ( kaowool ) around the joint and then bound it with strips of .015 " stainless steel ( peddle bins are .015" )

If I hadn't been committed and started to build the D10 I could have been tempted to make a low pressure coil to power a 10V as I am quite sure that very high pressure and high temp steam would ruin a slide valve engine, in fact if I was to whack the flash steam from my present set up into a slide valve engine it would melt the valve before the pressure seized the engine.

Regarding Temperatures, I was never really concerned about that, I was more intent in getting the plant to run and as there was nobody up here doing this sort of thing I plowed my lonely furrow with the help of telephone calls to Bob Kirtley.
I can tell you that when the engine fired on the bench and I let it run for about 1-min looking through the burner tubes the St/St coil was white hot 2" from the front  and at the exhaust end the tail of the coil in the cold end (L.O.L ) was bright red with about 12 ' of flame shooting up so it wasn't a thing to be trifled with and as I didn't like to run it off load out of the water 1 min was enough, needless to say all of this was done outside of the workshop.
I think I mentioned that I have retired the boat at present as it's going too fast and with some times a radio glich it's very dangerous.

I am intrigued with your Steam Jet experiments, I wonder if a high pressure Flash set up would work. Keep up the experiments.

George.
Title: Re: Flash steam plant control.
Post by: SteamboatPhil on December 07, 2010, 11:46:40 AM
Hi Ian & George

I also had trouble with combustion on my plant, and had wrapped the s/s liner to tight around the coil, although the plant ran, it was no great steamer. Redoing the inner wrapper masde a huge difference, and then I played with the exhust outlet (its now huge) and I'm now getting a resonable performance (its a V4 straight runner with piston valves)
With regard to high pressure on a slide valve engine, this should not be to much of a problem (as long as you are not going to compete with Bob (Kirtley) and his Hydroplane.
I am building a flash steam (radio this time) boat  with a slide valve engine (ala Mr Rayman's High speed engine) but using electric driven pumps (ala Ian), so not sure how it will all come together, but watch this space...........
Title: Re: Flash steam plant control.
Post by: ooyah/2 on December 07, 2010, 09:51:12 PM
Hi Phil,
This is what happened to me in my very early experiments, I made the coil and casing as A.Rs design in Exp.flash steam and found the it didn't work.
The double coil was too tight in the casing and the exhaust escape was too small, so as the pic that you already have I changed the coil to a straight one with plenty of space between and around the coil which gave great improvement, I also changed the burner to a tapered cone as R.Ks and this gave further improvement.

You said some time ago that you were going to try and achieve 40 mph from a double acting slide valve engine.
The engine that you are intending to use I don't think that this is possible, I say this as I have in the past made one of A.Rs engines and it seized under high pressure/ temp's.
If you lap the piston to the bore the tolerances are too tight and the valve wares tremendously under pressure which caused the engine seizure, this was with the boiler designed by A.R. working at 150 psi also with the shaft at 1/4 " dia with a groove for oiling the big end in my opinion is it's liable to sheer under the torque required for 40 mph.
It was after my experiments with this set up that I contacted R.K. and with his help and his drawings I made the 3/4 bore poppet valve engine with the twin burners which I eventually achieved 25 mph, but had to rebuild every 6 months.
The latest engine is a copy of R.Ks but only 1.125" bore ( R.Ks is 1.187 " bore ) with three burners same length of coil and the valve is made from a Cummins engine exhaust valve and with this set up have achieved 40 mph. and the engine peaking at between 10,000-- 15,000 rpm. the pumps are geared 6/1 from the engine all as my posting on the flash steam OOYAH.

40 mph is a bit of a handful on radio and very dangerous and plenty of space is required. In all off my early researches  90% of the old flash steam racing exponents used piston valve engines once they were dealing with flash steam as they found that double acting slide valve engines  couldn't produce the power.
Now Phil I am not  suggesting that you abandon your build, we can only learn by what others in the flash steam brigade do, there's not many about, it's only my opinion based on what I have already done, I hope you prove me wrong so I shall watch this space.
You will have to have some very fast electric pumps to feed the burners and boiler.

Regards
George.


Title: Re: Flash steam plant control.
Post by: Circlip on December 08, 2010, 11:01:59 AM
Good to note that the spirit of experimentation is still alive and well and carried on by those who know what they're doing. That's not to say we all have to start somewhere so we shouldn't dampen the spirit of discovery, but, there's a difference between progressive tests and the "I've just designed" brigade who have naff all experience of even the Basic principles of steam operation from a safety point of view.

  Given the depth of knowledge exhibited by the present posters,(and that's a compliment), I did flinch at the thought of a "Free Running High speed flasher" though and have to agree with George (WHAT, a Yorkshireman agreeing with a Scot??????) in Phil's case. In the case of a "Glitch" it IS a free runner.

  Given that the worst case scenario is to mix Water, Electricity and a Woman, (Washing Machine) the second must be to mix High pressure steam and electronics to an untethered fast mover? Yes, the gas turbine people have done it on both toy aircraft and boats but even a toy glider has been responsible for at least two fatalities to my knowledge. Strange how the "Go faster cos I can" brigade don't have a little forethough on non "Organised" events when the uneducated bystander thinks "Oh, I've a pot of spare money, I'LL have a bash at that", and YES it does happen in ALL paths of the toy hobbies.

  Bricks on a string will always look impressive (strong string hopefully) and the present speed runs shown look good, but note how they hide BEHIND a cage when they've let go.

  Regards  Ian.
Title: Re: Flash steam plant control.
Post by: flashtwo on December 09, 2010, 12:28:55 PM
Hi,

Thanks for the compliment Circlip, we all appreciate it.

I've just had the first steaming trial with the new vertical boiler, just one leaky connector going to the engine, but otherwise ok.

I had the prop spinning in air up to about 350RPM with the steam pressure at about 6psi; I won't be able to run it properly until its in the water.

A few figures were obtained though: the boiler feed inlet temperature from the feed heater was 93degC and the steam outlet was 109degC. The stack exhaust temperature was 96degC showing that most of the heat was being transfered to the water from the combustion gases.

There was no burner blowback, but saying that, the gas cylinder pressure was down at 7psi, due to the very cold weather, whereas, during the summer it is at 35psi.

The boiler case insulation needs to be increased as the outside was quite hot.

I've brought the gas cylinders indoors to warm up overnight and then I'll do some more test runs.

Ian.
Title: Re: Flash steam plant control.
Post by: gondolier88 on December 09, 2010, 04:19:03 PM
A few figures were obtained though: the boiler feed inlet temperature from the feed heater was 93degC and the steam outlet was 109degC. The stack exhaust temperature was 96degC showing that most of the heat was being transfered to the water from the combustion gases.
...Ian.

That IS impressive, well done!
Title: Re: Flash steam plant control.
Post by: SteamboatPhil on December 10, 2010, 08:06:24 AM
Oooh, thanks George, it seems I might be heading down the wrong track, did not realise you had tried it (I should have guessed) there's me thinking I had come up with something new, should have known there is nothing new. I will have to start a bit of a re-think, and maybe go for just a nice performance (say around 20mph). As you rightly say Circlip could be a bit hairy (me and radio----hummm then add HP steam)....so back to the drawing board and a little re-think.
Right just off to the M E exhibition where I shall be showing my stuff.......
Title: Re: Flash steam plant control.
Post by: ooyah/2 on December 10, 2010, 09:03:28 PM
Circlip,

THE END OF THE WORLD IS NIGH !!!!!!!!!  (WHAT, a Yorkshireman agreeing with a Scot??????)
Soon put a stop to that ,look out for Flying Haggis they will be fired from the border, by steam cannon, Bradford ain't that far.

Ian , you are so right , when this thing OOYAH went it's own merry little way with me twiddling the sticks like mad and now't happening is quite a frightening thing and as I have said it's mothballed at present until I consider what to do with it.
George.
Title: Re: Flash steam plant control.
Post by: SteamboatPhil on December 11, 2010, 11:19:33 PM
It has got me thinking to George, having spent my life with boats going straight over 100yds, and radio control being still a dark art...........

Oh circlip I'm slowing down.......... :((

Back to going straight-----but fast  O0
Title: Re: Flash steam plant control.
Post by: flashtwo on December 12, 2010, 10:41:17 AM
Hi,

Did some more tests on the vertical boiler yesterday with a warm gas cylinder with about 22psi gas pressure.

Not surprisingly, there was some flame blowback with the gas valve fully open, but it does heat up much quicker than the previous horizontal boiler.

When the gas cylinder cooled down, I noticed that the engine revs responded very quickly to an increase in gas flow when I warmed the gas cylinder with my hands; this is very promising, since it will improve the acceleration / deceleration of the boat.

I've ordered some more lengths of 5/32inch copper tube and will wind a smaller area coil of about 120 sq.in in place of the current 200 in order to reduce the flame blowback.  As the feed inlet temperature is so high (96degC), I may not need such a large area anyway.

Ian
Title: Re: Flash steam plant control.
Post by: Circlip on December 12, 2010, 11:34:22 AM
Quote
,look out for Flying Haggis they will be fired from the border

  Re-hulled Ooyah to look like one George??

Quote
it's mothballed at present until I consider what to do with it.
George.

 Psss, wana buy a Mamod??????

 Don't let me harden your damper Phil, just be aware. Many will say that the "New" 2.4Gigglies is far less subject to interference, probably so but then we found out about sunspot activity and the dreaded CB brigade on the Moggy cycle bands. We all know that we have an unrestricted right to play with our waterbourne Exocets with impunity don't we?? Have you got any grandkids that could become damaged by someone elses "Right of passage"?

  Regards  Ian.
Title: Re: Flash steam plant control.
Post by: TurboTyne on January 14, 2011, 09:36:46 AM
Hello Flashtwo

It was through searching of the internet  for information about the control of monotube boilers, that I discovered the ModelBoat Mayhem forum - because of your posts  about Vital Byte.  Now I have joined, I wonder if I can ask your advice about a few aspects of your very impressive project since I hope to attempt to follow your lead and make my own controlled boiler.

Could you please give some details of the motors that you used to drive the feed pumps and where they came from? Also, did you consider using stepper motors for this? I know little about this sort of thing but I gather they can be easily controlled from PIC microcontrollers.  I am wondering if a stepper would have any advantages or disadvantages for driving the pump compared to a simple DC motor?

Thanks

Mike
Title: Re: Flash steam plant control.
Post by: flashtwo on January 15, 2011, 05:22:52 PM
Hi Mike,

The most important aspect of flash boiler control is to maintain feed flow independently of the boiler pressure. Another feed requirement is to be able to set the feed to anywhere between zero and say 100cc/min, since this governs the rate of steam production and eventually the boat's speed.

The stepper motors are usually used for positional duties, e.g. telescope directional mounts, robotics, interfacing with hydraulic systems etc., and as you say these work very well with PICs. The required motor torque would have to calculated from the pump's ram diameter, operating crank length and the expected boiler pressure (and then double it!). Of course, if you have a ready supply of suitable stepper motors and interface I.C.s, there's no reason why they can't be used for pumping. One advantage of the stepper motor over an ordinary electric motor, is that it follows the pulse frequency of the PIC (as long as it doesn't pole-slip) and wouldn't need additional devices for measuring the pump speed and hence feed flow. You would have to weigh up the economics of which motor to use.

For pumping duties, I've been using an ordinary motor with a gearbox and a range of pressures and flows can be achieved by different combinations of gearbox and motor. A PIC can produce the necessary 1 to 2ms pulse to an ESC, which then powers the motor. It does however require a pickup (Hall effect device) to monitor the shaft speed and another PIC to convert the shaft pulses into RPM/feed flow in order that the PIC can amend the 1 to 2ms pulse if the flow is incorrect.

I've obtained my motor/gearboxes from http://www.mfacomodrills.com/ and are currently using a 385 motor with 100:1 gearbox driving a 1 inch stroke (1/2" crank), 1/4" ram. With this setup, I can achieve a flow of 75cc/min of up to 100psi with a 12volt motor supply. The actual required feed flow is set at the transmitter much as you would set the throttle (the flash boiler supplies steam directly to the engine and as such doesn't have a regulator / throttle).

The actual pump is of my own design and uses 3/16th ball valves, which are both accessable from above for cleaning without having to disturb any pipework. Since the boiler is using lake water (via a filter), I needed access to the valves for debris inspection, although any trouble is usually from the ram grease getting onto the ball valve

If you can build a controllable pump, then you are well on the way to controlling a flash boiler.

Ian.
Title: Re: Flash steam plant control.
Post by: TurboTyne on January 16, 2011, 07:22:11 PM
Hi Ian

Thanks a lot for your very helpful reply.  I shall stick with your tried and tested use of a standard DC motor, especially now I’ve seen what is available at "mfacomodrills.com". My previous searching had failed to reveal any company selling anywhere near such a good selection of motors as theirs.

Can I please pester you with another question? This time it’s about the pressure sensors/transmitters that you used.  Can you please let me know the type(s) and from where you bought them. I have seen some quite pricey units at Farnell and have been wondering about trying to utilise parts from Maplin digital tyre pressure gauges. (They retail at just £3.99 and are rated for zero to 150psi apparently with a 1 psi resolution).

Thanks again

Mike
Title: Re: Flash steam plant control.
Post by: flashtwo on January 17, 2011, 11:53:01 AM
Hi Mike,

I've been using what might be regarded as expensive (£85) pressure transmiters from RS Components, part no 455 4624. These are for the range 0 to 10 Bar (approx 0-150psi) and give a 4 to 20mA output, which can be put through a suitably scaled ammeter and/or into the analogue input of a PIC.

The advantage of using a transmitter is that the data, once "inside" the PIC, it can be used for control and also indication, either on a LCD and/or, as on "Vital Byte", a servo driven indicator that can easily be seen from the shore.

Frankly, I only tried using the pressure for control during the early experiments and now only use it for start-up and monitoring from the shore, in which case a 2 inch diameter (tyre pump gauge?),  traditional pressure gauge would suffice. The signal is also used to shut the gas valve if the pressure exceeds 60psi, but this has rarely been used in practice.

I see the Maplin’s digital gauge (A12JR) is +/-1psi accurate, which is more than adequate for our application for start-up and monitoring purposes, though it would be a bit small to see from the shore.

Whichever pressure device you use, you should ensure that a "swan-neck" (u-tube) is placed between the steam manifold and the gauge, so that a slug of cold water condenses and prevents the steam from over-heating the gauge/transmitter.

I also use a pressure transmitter to monitor the fuel gas cylinder pressure. This signal again is fed into the PIC where it is used as a form of fuel-gauge (a switch is used to change-over from the servo indicating steam pressure to that of indicating gas pressure); this is very useful for extended runs (an hour) and you want to keep an eye on the available fuel supply. The gas pressure is also used to trim the steam temperature control loop so that, when a fresh cylinder is installed and the gas pressure is high, the gas valve doesn’t open too vigorously. This is a bit of icing on the cake regarding temperature control and I think you could initially get away without using it. A conventional 2 inch gauge (0 to 60 psi) indicating gas pressure would be very useful to have (no “swan-neck” required).

A couple of old foot pumps would be a good source of useful size gauges. Polly Model Engineering do a range of gauges and also Technobots on http://www.technobotsonline.com/pneumatics/pressure-gauges.html. do a very reasonably priced range of gauges.

Since the “flash boiler” is not legally considered a pressure vessel, it doesn’t require a pressure gauge nor a safety valve, since the amount of “stored energy” is so low.

Ian.
Title: Re: Flash steam plant control.
Post by: gondolier88 on January 17, 2011, 07:57:58 PM
I suppose with a flash boiler the use of a digital thermometer is out of the question a the boiler temperature would be far higher than the steam temperature?

Greg
Title: Re: Flash steam plant control.
Post by: flashtwo on January 17, 2011, 09:13:21 PM
Hi Greg,

Are you suggesting measuring the steam temperature and inferring the pressure from the steam saturation table?

Ian
Title: Re: Flash steam plant control.
Post by: gondolier88 on January 17, 2011, 09:28:20 PM
Hi Ian,

Yes, that's exactly what I was thinking, of course Temp./Press. being directly correlating- a question once given me- if ever I was in the situation where every pressure gauge on a ship was wrong and you had no means of getting an accurate pressure reading what would you do- answer use an accurate thermometer and test the temperature of the steam take off, checking it off on the steam table.

This might work at the steam take-off on a flash boiler, but I would think the coil would be too hot to give any kind of realistic reading of the steam temp.? Not knowing enough about electrics I would possibly suggest high tem. thermistors? (think I may have mentioned this before?)

Greg
Title: Re: Flash steam plant control.
Post by: flashtwo on January 17, 2011, 11:55:55 PM
Hi Greg,

As long as you haven't got any superheat, i.e. measuring the steam temperature at the drum, then you could use the temperature, as with the old Cheddar ABC system that used a thermistor.

With the flash boiler (no drum) it is very easy, in fact desirable, to generate superheated steam and I've obtained 710degC with my steam jet boat; obviously for the conventional engine a only few degrees is desirable for dry steaming. Therefore, you can't use the temperature as a pressure substitute. In power stations, to obtain a representative drum steam temperature, the pressure is actually measured and converted to temperature.

You're right about using the temperature as a substitute under certain conditions. I do find the steam saturation table very useful during experimenting, since a lot of the time it is handy to correlate the pressure and temperature measurements.

I've understand that thermistors, although now very accurate, are only suitable up to about 135degC, therefore thermocouples are used, which are suitable to above 1000 degC.

Ian
Title: Re: Flash steam plant control.
Post by: gondolier88 on January 18, 2011, 07:42:49 AM
Hi Ian,

Of course, a higher reading in temperature due to superheat would definitely give a false pressure reading.

I think that the point about the thermistors is something you have told us before, forgive my bad memory. I'll have to check 135deg. off on my steam tables- im not reading steam tables while having breakfast, have to draw the line somewhere! I was thinking about using a thermistor on the boiler I'm constructing at the moment.

The thermocouples that you mention, is there anything 'special' about them or are they mechanical ones, like the ones old gas valves for flame failure sensing, or are they now an electrical 'sensor' that has replaced them?

Greg
Title: Re: Flash steam plant control.
Post by: TurboTyne on January 18, 2011, 08:08:04 AM
Hi Ian

Thanks very much for the second lot of information and advice.

Actually I was wondering about trying to dismantle the Maplin pressure gauge so as to make use of the electrical output from the sensor that must be in there. Perhaps the whole thing will be so integrated that it is not possible, but at that price it seems worth a try – especially in view of the info summarised at end of this message.

Yes, the Farnell pressure transducer prices range from £50 up to £500, which fits with the £85 price ticket of your sensors. Over the years I have accumulated quite a collection of mechanical gauges and I was seeking an electrical output for pressure mainly because, in an early post about Vital Byte you said that the pressure data was used to decide the steam saturation temperature and I had assumed that was on a real-time basis. Is that the case? If so, do you use the pressure output in that role in addition to its forming a safety back-up?   

From your advice, I now see that I should concentrate initially on setting up a controlled feed pump and a servo-actuated gas valve that is controlled by a thermocouple via a PIC device.  Hmmmm - if I get that far, I shall be well pleased and may then feel more confident that an investment in a decent pressure sensor is worthwhile.

I became a little side-tracked on trying to find information on components in cheap tyre pressure gauges. This led me to a fascinating document describing in detail the really sophisticated design logic behind what looks very much like my simple Halfords digital pressure gauge. This describes how a sensor chip is connected via an op-amp to a PIC 16F873. The microcontroller employs cunning logic to optimise the pressure data before it is displayed.  In case you or anyone else is interested, this URL should take you to the document :  http://www.ece.msstate.edu/courses/design/ece4512/2003_fall/air_pressure/Design.pdf
Also, the following link gives a data sheet for the sensor integrated circuit that is referred to.  http://www.cdiweb.com/datasheets/icsensors/1451.pdf
Just for completeness, the following link shows a report by someone who utilised electronic components in a tyre pressure gauge (to control a pool filtration system).  http://misterhouse.wikispaces.com/1-Wire+Pressure+Gauge

I guess there must be something extra in a sensor from RS or Farnell that costs over £80, but maybe it will be interesting to see if these cheap sensors prove useful.
Regards
Mike
Title: Re: Flash steam plant control.
Post by: flashtwo on January 18, 2011, 10:15:50 AM
Hi Mike,

That's some very interesting and useful research that you have done there.

Regarding the Maplin gauge, I think that if you can get to the op-amp output that goes to the PIC (assuming its not encased with epoxy), then just a pair of wires to your PIC would do the trick - as you say at the price its well worth the experiment.

When I was using the pressure signal for the sat. temp., I eventually noticed it was causing instability when I was operating the valve gear on the engine, i.e.  the pressure would fluctuate, changing the sat. temp. value, which eventually caused the gas valve to vary unnecessary. Keeping the pressure out of the control loop kept things stable; another nail in the coffin for needing a pressure signal.

Regarding the safety back-up of shutting the gas valve when the pressure gets too high(>60psi), I think the pressure signal has some value here since it prevents lifting the safety valve which is perhaps set at 100psi - safety valves don't always reseat very well after lifting and you end up with a irritating leak.

I did originally include software filtering for an erratic pressure signal, but removed it when I discovered the problem was with steam-induced static electricity.

Have you looked the PICAXE website. They sell systems which can be written in PBasic and they already have a suite of code for doing the maths. They don't handle negative numbers for some reason and have had problems with jittering servos, although I daresay that there are work-arounds. There is a very large user base.

I think a very useful start would be to couple an LCD to the PIC. This allows you "see" what is going on in the PIC and is extremely useful for diagnosing problems.

I see from the data sheets that the sensor's expected media is a dry, non-corrosive gas, so you might need to consider the effects of water on the device.

I suppose what you are paying for with the professional sensors, is that they come ready calibrated, have a guarateed spec. especially regard to temperature stability which is normally the killer for the cheaper instruments. And not to be overlooked is the substantial mechanical case and connector that it is packaged in and its suitability for  a range of media including water.

Anyway, I would certainly experiment with the Maplins gauge, it might benifit a lot of people looking for a less expensive solution - I might try one out of  interest.

Ian
Title: Re: Flash steam plant control.
Post by: TurboTyne on January 18, 2011, 07:08:13 PM
Hi Ian

Thanks for explaining more about the pressure problems. 

Although I shall not be bothering about pressure detection for a while, whilst in town this morning I picked up one of the Maplin pressure gauges since I was curious to have a look inside. Easy to open up (2 small screws) and this revealed what seems to be a rather different sensor to the one mentioned in the previous message. As I suspected might be the case, this one looks to be of much poorer quality - but for just £3.99 one can’t expect too much. Before you buy one of these you might want to have a look at the attached photos which show it’s insides. Maybe a more expensive gauge, such as the Halford one would be a better investment but I think you have spotted the potential big limitations of these devices in that they are rated for dry non-corrosive gases (and may not show reliable data as temperature varies). Also, I wonder how impervious they are to gases. For example, if used to continuously monitor butane gas pressure, might the gas seep slowly through the sensor? I wonder if filling them with an inert liquid such as silicone fluid might provide a way to transmit the pressure whilst protecting them from water etc. When (if) I get that far, I’ll think invest in a professional device.

Hopefully the attached photos are fairly self-explanatory. Have you any idea what the large metallic disc could be for?  At first I assumed it was some type of battery, but upon removing the circuit board the actual battery was revealed mounted on it’s under-side – see one of the photos. Removing the sensor revealed it to be some small circuits on a small disc of plastic which was itself clamped against a silicone rubber ring to seal between it and the outer casing.  The small block attached to the rear of the board seems to be a type of multii-turn potentiometer (for calibration?) but I can see no signs of anything looking like a microcontroller. The only device hiding under the LCD  looked like a round flattened black blob about 8 mm diameter attached to the circuit board.
Regards
Mike
Title: Re: Flash steam plant control.
Post by: flashtwo on January 18, 2011, 07:51:21 PM
Hi Mike,

Thanks for the close up images of the device.

That large metallic disk looks like a piezo-electric "speaker" perhaps used to give a warning bleep when taking a reading; any info in the instruction leaflet?. They are very useful for making a vibration detector (in conjunction with an oscilloscope) for use on the steam engine. They give out about a 2 volt signal and can show things like piston slap and general engine noise. With a reference pulse (RPM detector) they are very accurate in showing timing information, if not absolute vibration levels.

Anyway back to pressure measurement...

I bet that under that black blob will be a surface mount device with no useful information about what type of chip it is (bitter experience!) . It may be just an op amp and the LCD may be a simple self contained voltmeter.

The small circuits on the disk of plastic may be the actual strain gauges as described in one of articles that you found and, as the disk distorts under pressure, give a varying electrical output.

The silicon oil is a good idea; I've seen that done in industry with glycol pots being used between steam lines and distant pressure gauges to prevent line freezing in the winter. Silicon oil is pretty inert stuff and I've seen it used in electro-pneumatic converters to keep moisture out of the electrics side.

Personally, to start with, I think a couple of those Technobot 50mm pressure gauges will be of great service and, as things get more sophisticated, invest in the more expensive transmitter.

Ian.
Title: Re: Flash steam plant control.
Post by: flashtwo on January 18, 2011, 07:55:56 PM
Hi all Mayhemers,

Just a quick note to say that "Vital Byte", with its experiimental horizontal and vertical boilers, will be on its annual pilgrimage to the Ally Pally London Model Engineering Exhibition this coming Friday, Saturday and Sunday.

It will be on the Blackheath Club stand at the kind invitation of SteamboatPhil.

Hope to see some of you there.

Ian.
Title: Re: Flash steam plant control.
Post by: TurboTyne on January 19, 2011, 08:29:39 AM
Hi Ian

You're spot on regarding the metal disc. The pressure gauge makes a short high pitched buzz each time one presses its button - but I had not even questioned where the noise comes from. Very interesting to hear about the possibility of using this as a mechanical sensor.
Pressing the button turns the unit on and then further pressing cycles the display between psi, bar and kpa. The instructions are very limited but they do state the gauge is accurate to +/- 1 psi over temp range of -20 to + 40 deg C.

I was a bit surprised when, upon removing the 3 screws holding its cover, the LCD fell away from the board. There is a flat-sided rubbery strip which is pressed between a row of contacts on the board and a row of contacts on the LCD. This strip seems to contain within it conductive paths that link the upper and lower surfaces. Is this type of flexible connection very common?

One last thing - thanks for the pointer to Picaxe. I'd not heard of this product range and it looks interesting. However, since father Christmas brought me a Pickit 3 programmer/debugger, initially I shall see how I get on with this.  Maybe I'll post something if/when I make some tangible progress.

Mike
Title: Re: Flash steam plant control.
Post by: flashtwo on February 03, 2011, 07:42:34 PM
Good news Mayhemers,

The article (7000 words plus photo's), describing "Vital Byte's" control system,  has been accepted for publication by the magazine "Engineering in Miniature", though the date has to be confirmed.

This is an imaginative move by the publishers, since it strays a long way from their traditional engineering articles, and introduces readers to a different way of doing things with steam. (Perhaps the magazine should be subtitled "Software Engineering in Miniature!).

I hope it will give a more succinct description of the system, than can be gained from all the Mayhem posts, which have shown, over the last year or two, how the system was developed.

"Vital Byte's" vertical boiler is still being developed, as well as, the steam jet engine, the Calliope, and an electric pump controller for Steamboat Phil. - no excuse for being bored!

Ian.
Title: Re: Flash steam plant control.
Post by: TurboTyne on February 04, 2011, 05:14:34 PM
Hi Ian

That's excellent!  Once you are informed, I hope you will let us know the issue(s?) it is to appear in - because I definitely plan to buy a copy.

Regards

Mike
Title: Re: Flash steam plant control.
Post by: flashtwo on February 17, 2011, 01:48:06 PM
Hi Mayhemers,

I just completed and tested the feed pump controller that I've designed and constructed for SteamBoat Phil, so that he can continue with his flash steam boiler with the electric pump.

The black box contains, as usual, a PIC that encompasses some of the code that is in "Vital Byte's" controller. The device converts the shaft pulses into an RPM value, compares it with the RPM setting and adjusts the PWM signal going to the ESC that is connected to the electric pump. The Hall effect shaft probe then sends the shaft pulse back to the controller.

The control is in the form of Proportional and Integral Action and, as such, can be tuned to give a fast or slow pump response. Because the pump speed is controlled, the feed flow is independent of the boiler pressure.

The red LED illuminates on every shaft revolution and the green LED illuminates when the speed is within 10 RPM of the setting. The ESC setting switch has three positions:-
normal running, 1ms PWM and 2ms PWM outputs. The PWM settings allow the ESC to be range set  when required.

I haven't fitted a scale yet, but it is ranged for 0 to 200 RPM. I've tested it on "Vital Byte's" pump and it performed as designed.

Ian
Title: Re: Flash steam plant control.
Post by: SteamboatPhil on February 17, 2011, 09:40:23 PM
Oh we are getting close now......Mayhem will be the maiden voyge (with any luck)
Right back to getting it off the bench and into the boat  %%
Title: Re: Flash steam plant control.
Post by: logoman on February 17, 2011, 10:33:08 PM
I'm lost with the acronyms, I know RPM, but lost with the others.

btw, this is very close to what we were talking about a couple of years ago...brilliant work Ian!
Title: Re: Flash steam plant control.
Post by: flashtwo on February 17, 2011, 11:03:32 PM
Sorry Miles,

PIC - Peripheral Interface Controller was its very original name, but it now refers to the micro-controllers that Microchip manufactures. The PICs are very useful computers that have digital and analogue interfaces to the "real" world.

PWM - Pulse Width Modulation. This is the most common signal standard that Radio Control servos use. The signal is a pulse (that repeats every 20ms), which varies between 1ms and 2ms in duration, and in doing so turns the servo's mechanical shaft through 90 degrees.

ESC - Electronic Speed Controller. This is the electronic module that receives the PWM, in place of a servo, and controls the current going to the electric motor. Its title is a bit of a misnomer, since it doesn't control the actual speed if the motor's mechanical load is changed (that is why I've had to build a proper speed controller).

LED - Light Emitting Diode - but I bet you knew that.

Yes, you're right, this how the "Vital Byte"'s controller started out, but then grew like Topsy!

TTFN
Ian
Title: Re: Flash steam plant control.
Post by: flashtwo on March 10, 2011, 01:13:32 PM
Hi,

I've just experimented with fan assisted combustion on the vertical boiler, since, despite changing the surface area, I was getting far less performance than with the original horizontal boiler. I had noticed a lot of soot build-up in the boiler, which, as you know, is indicative of poor combustion.

I duck-taped a small 1.5inch computer fan to a length of brass tube and directed it at the furnace air inlet and the D10 RPM increased from 370 to 520RPM and vice-versa, if I removed the fan; the higher revs being comparable with the horizontal boiler. So it seems that my problems had been with combustion and not surface area all along.

The fan is 12v, 160mA and just blows a gentle draught - I wonder what i would get with a larger fan?

I will now build a proper "windbox" and perhaps control the fan with the computer (oh no, not more software!).

I could have built a larger boiler, but I'm trying to keep within the boiler size limits of the planned Edwardian steam launch.

Ian
Title: Re: Flash steam plant control.
Post by: logoman on March 10, 2011, 10:16:35 PM

I will now build a proper "windbox" and perhaps control the fan with the computer (oh no, not more software!).

Ian

I get the feeling that this was inevitable!  :-)) what next?
(https://sites.google.com/site/jorgensensteamsite2/valve-gear-computer-programming/Spreadsheet-01.jpg)
Title: Re: Flash steam plant control.
Post by: flashtwo on March 22, 2011, 10:33:13 AM
OK Mayhemers,

This is what I mean by a software "mod", totally meaningless to non-nerds! What follows is the extra software for the electric fan speed to track the opening of the gas valve, but also to run at a minimum setting when the gas valve is fully shut. I did try running without the software with the fan on fully, but the pilot light kept getting blown out and the excess air would most likely cool the boiler. Every thing after a semi-colon is a comment describing the action.

      ; FAN CONTROL
FAN_CONTROL
               ; A duty value 64535 to 63535 for the Force Draught Fan ESC is derived from the
               ; Gas Valve position display value GV_POS, which has the range 0 to 1000.
               ; FAN duty = 64535 - GV_POS.
               ; It is done this way to ensure a 1ms pulse is obtained independently of the Gas Valve
               ; closed signal, which could vary according to the manually adjusted Gas Valve closed setting.

               ; FAN duty = 64535d - GV_POS.


               ; Set FAN to 64585d, FC49h. Default 1ms value. It should be 64535d, but the duty
               ; was 50us too long.
      CALL   BANK_0_P2
      MOVLW   H'FC'      
      MOVWF   FAN_H
      MOVLW   H'49'
      MOVWF   FAN_L


      CALL   BANK_2_P2      
      MOVF   GV_POS_H,W   ; Pass GV_POS_H into temporary register to avoid corrupting it.
      MOVWF   SUB_TEMP_H

      MOVF   GV_POS_L,W   ; Pass GV_POS_L into W before subtraction the value from FAN_L.
      CALL   BANK_0_P2
      SUBWF   FAN_L,1      ; Subtract the value from FAN_L   
      BTFSS   STATUS,C   ; Check for carry-over.
      GOTO   FAN_A
      GOTO   FAN_B

FAN_A      CALL   BANK_2_P2   
      INCF   SUB_TEMP_H,1   ; Increment the next lower column (in arithmetic terms).

FAN_B   
      CALL   BANK_2_P2
      MOVF   SUB_TEMP_H,W   ; Pass GV_POS_H into W before subtraction the value from FAN_H.    
      CALL   BANK_0_P2
      SUBWF   FAN_H,1      ; Subtract the value of GV_POS_H from FAN_H   


               ; A manually amended speed offset is now subtracted from FAN
               ; in order to run the Fan even when the Gas Valve is fully shut.
               ; This offset can be used to ensure that sufficent air is supplied for combustion.


      CALL   BANK_2_P2      
      MOVF   FAN_OFFSET_H,W   ; Pass FAN_OFFSET_H into temporary register to avoid corrupting it.
      MOVWF   SUB_TEMP_H

      MOVF   FAN_OFFSET_L,W   ; Pass FAN_OFFSET_L into W before subtraction the value from FAN_L.
      CALL   BANK_0_P2
      SUBWF   FAN_L,1      ; Subtract the value from FAN_L   
      BTFSS   STATUS,C     ; Check for carry-over.
      GOTO   FAN_OFF_A
      GOTO   FAN_OFF_B

FAN_OFF_A   CALL   BANK_2_P2   
      INCF   SUB_TEMP_H,1   ; Increment the next lower column (in arithmetic terms).

FAN_OFF_B   CALL   BANK_2_P2
      MOVF   SUB_TEMP_H,W   ; Pass FAN_OFFSET_H into W before subtraction the value from FAN_H.    
      CALL   BANK_0_P2
      SUBWF   FAN_H,1      ; Subtract the value of FAN_OFFSET_H from FAN_H



               ; DUTY_4 is the interrupt FAN duty version. This is in order to present to the interrupt
               ; a single source of DUTY rather than picking up a value of FAN part of the way through the
               ; calculation; this avoids erractic servo movement.

               ; On start-up the ESC is allowed 3s to initialise at the 1ms PWM setting.
      CALL   BANK_2_P2   ; Test the ESC initialising flag.
      BTFSS   C_FLAGS_2,6
      GOTO   FAN_NORMAL
      
               ; Set the DUTY to 64535d, FC17h. FC17h amended to FC4Dh,
               ; because pulse length on 'scope was 1054us and not 1000.
      CALL   BANK_3_P2
      MOVLW   H'FC'
      MOVWF   DUTY_4_H
      MOVLW   H'4D'
      MOVWF   DUTY_4_L
      GOTO   END_FAN_CONTROL

FAN_NORMAL   CALL   BANK_0_P2
      MOVF   FAN_H,W   
      CALL   BANK_3_P2
      MOVWF   DUTY_4_H

      CALL   BANK_0_P2
      MOVF   FAN_L,W
      CALL   BANK_3_P2
      MOVWF   DUTY_4_L


               ; DUTY_4 is now available to control the Fan speed directly proportional
               ; to the Gas Valve opening - more gas, more air.

END_FAN_CONTROL

Title: Re: Flash steam plant control.
Post by: flashtwo on March 22, 2011, 10:47:07 AM
Hi,

Back to the proper engineering ---

I've experimented with the fan arrangement and have found the most effective way for maximum combustion is to direct the fan output through the primary air intake of the burner where the fuel gas is initially mixed with the air. I have done away with the "bell" mouth of the traditional burner, which is there to cause turbulance and air-fuel mixing before combustion. No secondary air is involved.

The thing to be aware of is that the combustion temperature is now above the melting point of silver solder (the pilot light pipe popped out of its soldered connection!) even though the ordinary butane/propane gas is being used.

The engine responds immediately to any change to the gas input, since the flame is directed at the last section of the vertical flash coil and the steam temperature control is very good.

I hope the attached diagram can help to describe it a bit better.

Ian
Title: Re: Flash steam plant control.
Post by: ooyah/2 on March 22, 2011, 04:49:49 PM
Hi Ian,
That's a good idea inducing more air into the burner, must try it on my tug with the new D10

My Flash Steamer works on that principle of the more air the more revs.
My burners 3- off have the jets 1.5" clear of the venturi nozle  and the flame tube is 1" dia tapering out to 1.5" so the faster the boat goes it forces more air into the coil casing and gives a great burn
Don't ask me about temps as it's not advisable to sart the plant and let it run long enough on the bench to get some figures
(http://s2.postimage.org/2xv57yx9g/Flame_tubes_welded.jpg) (http://postimage.org/image/2xv57yx9g/)

(http://s2.postimage.org/2xxo6j0f8/Complete_case_and_burners.jpg) (http://postimage.org/image/2xxo6j0f8/)

Of course all that shiny Stainles steel is now burned black.
George.


































Title: Re: Flash steam plant control.
Post by: flashtwo on March 28, 2011, 09:57:52 AM
Hi George,

I have found that adding the fan not only improves the performance substantially, but also has eliminated the build up of soot within the boiler, so keeping the heating surfaces clear and iimproving the conduction.

I dismantled the vertical boiler at the weekend and found not a trace of soot on the fresh glass cloth insulation that is in direct contact with the whole of the combustion chamber, whereas previously whole sections were covered in soot.

I am just rebuilding the lower section of the boiler in order to accomodate the newly redesigned burner and its associated fan - with luck I should be out testing on the lake this weekend.

Ian.
Title: Re: Flash steam plant control.
Post by: ooyah/2 on March 28, 2011, 07:21:05 PM
Hi Ian,
Thank's for the info, I am at present without a test boiler,I have to cobble up a length of pipe and connect it to my tug boiler to get test steam.
I have nearly completed a Stuart Steam boiler feed pump, the one listed under steam so when it's completed I intend to experiment with a Mono tube boiler possibly with a small header tank and a ring burner  all fitted into a bean can as an outer shell.
I will need to make a speed controller for the pump and as I am Electrically ignorant I will get some of the lads in the club to help out.

I shall keep you informed when I get going.

George.
Title: Re: Flash steam plant control.
Post by: flashtwo on April 09, 2011, 03:40:58 PM
Hi,
This week I've been developing the new vertical boiler and, after some disappointing tests, have had a very successful run today.

The new lower part of the boiler was more enclosed than the original and relied on all of its air flowing through the fan – but this lead to a number of problems. First the pilot light kept going out and then, once the main flame was established, it operated with a fluttering noise, something between a cat purring loudly and the ominous sound of a V1!

I surmised that something akin to a pulse jet cycle was occurring with the combustion taking place explosively, the exhaust going through the boiler, followed by fresh air blown in by the fan, which then started the next cycle.

To try and break this cycle, I cut out two 12mm vertical slots either side of the burner to allow secondary air into the combustion chamber, which did the trick. The pilot flame (now with electronic ignition) stayed alight and the main flame burnt without the fluttering, although it was louder on full throttle than previously.

I had the Stuart D10 engine ticking over at 188RPM with minimum feed water, going up to 580RPM with maximum feed of 74cc/min with the gas valve at only 67% open (fresh cylinder feeding liquid). The feed inlet temperature rose to 98degC and the steam pressure was at 165kPa (24psi).

Removing the fan from the burner reduced the RPM to 290 from 580.

One new problem was that the gas outlet temperature was above 90degC when going full throttle, which required the application of a wet sponge on the pipe in order not to overheat the servo-controlled gas valve.

Early on in the tests, I had a failure of the main pump speed probe, but the software spotted this by shutting down the main and handing control over to the standby pump – a handy feature if out on the lake.

The attached photographs show the main components of the new combustion chamber – a) the burner assembly with the liquid to gas heater coil and pilot light take-off, b) the burner with the electronic ignition electrode, and c) the vertical boiler assembled, but without its outer cladding and without the two slots (the electrode has some temporary tape for strain relief on the cable).

I now need to tidy up the construction to make it more presentable on the planned Edwardian steam launch, a bit of cosmetic cladding I suppose.

Ian
Title: Re: Flash steam plant control.
Post by: flashtwo on June 02, 2011, 01:43:49 PM
Hi Mayhemers,

Well, "Vital Byte" made it to Wicksteed last weekend and had some very good runs on the pond despite the high winds.

The vertical boiler described above was not used primarily because the fan and burner arrangement was giving too much blowback into the hull. Instead a new design was built around the copper coil from the original horizontal boiler, which increased the surface area from 150 to 240 sq.inches.

A new design for the burner was produced, which was very much in the form of a smoker's pipe with a scroll of stainless steel mesh inserted into the bowl. This gave a very quiet and steady burn without the flame travelling along the mixing tube. A fuel heater was coiled around the bowl and the liquid was sufficiently boiled off to gas before it went to the nozzle via the control valve.

The runs on the pond were very successful, running rings (and figures of eight!) around SteamboatPhil and Stavros as they demonstrated Phil's newly acquired fine steam tug (a big vote of thanks to them for the successful weekend).

The engine was making a consistant 520RPM, peaking at 730RPM by judicious use of the valve gear by notching down a tad and waiting for the pressure to build up to above 45psi and then swinging the gear to fully open - this was impressive coming out of the "corner" causing V.B to leap forward.

I had a very good chat with Ken (Daniels?) from the MPBA - he is an ex-combustion engineer and has given me some excellent ideas to try out regarding the burner set up.

I will try the new burner with the previously described boiler and see if it will stop the blow-back problem.

Ian.

Title: Re: Flash steam plant control.
Post by: Xtian29 on June 09, 2011, 06:56:37 PM

Ian,

I have been reading with interest your efforts with your Flash steam control system, and have read the thread from cover to cover.You must have got your boy scout perseverance badge at some time in the past!

I fully intend to do something similar, but perhaps using the "Picaxe" chips as they are marketed as being so easy to use that even school children can get to grips with them. All I can say is school children must have improved a tad since my day, as I am struggling a bit, even though I have written a simple programme to run a temperature controller, and it actually worked!!

As my addition to the madness generally found all over this forum, I am building a D10 and have not wrecked it so far, and I am building a very very lightweight "whitehall" which has nice fair lines, and while it is a bit bigger than the average model boat (10 ft, and 200lbs displacement with me and a steam plant in it) I am hoping to get it chuffing along at 3 or 4 knots with either the D10 or something slightly bigger.

Here is a picture of the boat. It is built using green oak strips covered in "aerolene" (aircraft Dacron fabric) and weighs in at 20 lbs.

I am going to fit a 5" prop for starters, but am bound to have to experiment with sizes. See PM on this!

 
(http://s1.postimage.org/vbp8s7ic/whitehalljr_400.jpg) (http://postimage.org/image/vbp8s7ic/)
Title: Re: Flash steam plant control.
Post by: Xtian29 on June 14, 2011, 08:58:26 PM
Hi all,

A novice here, so please bear with me until you actually decide I am actually talking utter c%*p! Then put me straight.............

While I realise that there is going to be a published article some time soon on many of the aspects of this control system, I was wondering if the article or subsequent posts are going to contain full information on the program itself? Also, from dealings with similarly complex picaxe projects, once the circuits are finalised it is very simple nowadays to get proper printed circuits knocked up in China for not a lot! If interested I can find out more and quantities involved from the guy who knows....it is in the realms of a few quid each and 20 to 30 boards, I think....much better than Vero board and crossed fingers....The car guy just flogs the boards at about cost to anyone interested in building his projects, which gets more peeps making the systems than if they had to breadboard the whole thing, and so gives the projects legs!

My electronics quandary is that although I am slightly familiar with the programming of the "picaxe"chips ( a simple style of basic) I know nowt about the language the pic chips that this system uses speak!  All of the bespoke systems designed for the car I own, (by other cleverer peeps than me, like advanced battery management, IMA control and even cruise functions) have been done using picaxe programming, so do I learn both programming systems, or  write a picaxe programme to do the same job!!!  Is there anyone on here familiar with both systems that can point out their shortfalls and strengths.

Regarding the coils for the monotube, and following on from some coil making I have done for parts of my brewery, why are you guys monotube coils so untidy  :o  and also, why are they kept so helical and in the vicinity of the outer edges of the furnace containing tube rather than making them criss cross the furnaces entire area so they disturb the airflow and help to turbulate it without overly blocking the airflow? As a newbie to this, I am assuming that all this has already been tried and passed over as useless, but as we are not trying for max power with massive blowtorch style burners like the hydroplanes I was watching at Kingsbury water park last Sunday, but a distinctly more docile set up, I am still thinking it may be up for discussion. I will post some pictures soon of the kind of coil setups I am talking about so you can shoot me down in flames.....

I to am trying to power a D10 and I was thinking of carrying out some simple tests using one, or perhaps two of those simple gas hobs that cost next to nothing in the camping shops. They have a docile flame about 100 mm dia and should take a vertical tube about 100 mm dia or 210 by 100 oval and however tall.........Or do I still need massively more flame than that, putting it up closer to the blowtorch style burners and the melting silver solder? Has anyone experimented with these?    
Title: Re: Flash steam plant control.
Post by: flashtwo on July 04, 2011, 06:33:35 PM
Hi All Mayhemers,

I've been busy improving the vertical monotube boiler by reducing its height by 100mm and improving the gas burner system.

The original height was deemed a bit unstable, as Mayhemers may have witnessed at "windy" Wicksteed last May, and the shorter version is closer to the scale of the “proper” boat that I intend to construct.  

The original coil for the vertical boiler was taken from the successful horizontal boiler and had rather long tails to the coil and, since I wanted that coil to be refitted in the horizontal boiler, I wound a coil without the long tails and managed to maintain the 250 sq.inch copper to water surface area.

The liquid fuel is taken from the inverted gas cylinder, passed through a fuel pre-heater that is wound around the burner cup and then through a “cooling trough” that limits the temperature of the gas before it arrives at the servo gas control valve.

Due to the throttling effect of the gas passing through the valve, the outlet pipe was frosting up on occasions. If the liquid fuel goes through the nozzle, it pools and then flares, causing poor steam temperature control. The gas control valve outlet pipe was subsequently redirected through the so-called “cooling trough” to warm up the gas before it exits the nozzle.

Having sorted out the fuel gas temperature, the steam plant now performs very well across its power range – from a tickover of about 230RPM to a about 520RPM forward and 580RPM reverse. The 5 inch prop gives a fair bit of thrust at those higher revs!

Am I right to think that doubling the RPM quadruples the power output for a boat?

Today I’ve been adjusting the engine timing to give better forward revs.

I must admit that the poor old Stuart D10 has had a bit of a thrashing (over the last few years)such that a couple of parts of the reversing linkage have been replaced due to excess clearance.

I will be at the Guildford Model Engineering Society rally this coming weekend (9th/10th July) and look forward to seeing some of the Mayhem crowd there. Vital Byte will be there with its new boiler of course.

Ian.
Title: Re: Flash steam plant control.
Post by: Xtian29 on July 05, 2011, 01:17:28 PM
Hi Ian,
Do you have any idea when the magazine article is going to hot the shelves?

I have just wound a coil to start my experimentations, and because it was to hand and it suits me, and will provide new data, I have wound 25 ft of 3/16 od copper tube into a series of spiral layers. This gives a very compact coil that has an outer dia of 100 mm on each spiral and 7 individual layers. There is about 5 mm air gap between the spirals, and the same (or a bit more if you wish) between each layer. The lower spiral layer winds inward to it's centre on a horizontal plane and then twists vertically to the next layer and spirals outwards, back to the 100 mm periphery, then repeat...As far as the hot gasses are concerned,  this winding style distributes the coils evenly throughout the capacity of 125 mm stainless tube that surrounds it, so I am hoping the hot air flow is not restricted. I am now making a water pump using the 1" stroke crank assembly found in a Range Rover air suspension compressor. The 12v drive motor is too big, but will do for static experiments.

I intend trying a gentle 2.2 kw gas burner that spreads it's burn equaly over a 110 mm diameter for starters. Do you think I should go for a longer tube, bigger tube, or bigger burner at this stage, or shall we just wait and see what happens!

For when circuitry is finalised, Chinese printed circuit boards work out at abou £100 for 20, or a fiver each. More on that later if you intend publishing your programming info so Vital Byte gets to have competition. Flog this as a complete control system to the big guys with real boats and you have yourself a retirement plan, but it may involve a trailer tent and cheap camp sites!

I cannot post pictures of the coils at the moment, but will when I get back off bolls in sunny Yorkshire!
Title: Re: Flash steam plant control.
Post by: flashtwo on August 08, 2011, 09:48:57 AM
Hi Mayhemers,

Vital Byte (VB) had a successful display at the Guildford Steam Rally, despite the relatively small size of the demo pool of 20 by 20 feet.

All the attributes of the monotube boiler were demonstrated: quick steam raising from cold, good response to changing feed water flow (hence speed), ability to stop in mid-pond and restart from minimum pressure, and good response to engine change of direction (used a lot in the small pool!).

It was more of a demonstration of the boats manoeuvring ability than speed performance. VB was rammed by the Prinze Eugen, but she smartly bounced off  from VB’s 72lb displacement – Hood’s revenge I commented.

Silverbrewer and his mate came all the way down from Birmingham and brought with him his plastic propeller that was based on a brass one, which he had laser scanned into a computer system. The prop image was “edited” and then 3-D printed in a nylon-like plastic. It had a very slightly grainy finish but would be a totally serviceable item to fit on a model boat – I was very impressed.

Silverbrewer also brought his monotube coil that he has wound and also a selection of wire model coils with which he has been exploring the different ways of winding copper pipe – an excellent enthusiastic start and I wish him well.

Chris Putt was displaying his excellent 70lb displacement “Englishman” steam tug, which was powered, like Vital Byte, with the Stuart D10, but had a conventional boiler. Chris had not only built the engine from castings, but had designed and built his own boiler. Previous years Chris had shown me his design documentation for the boiler, including the stress calculations and sequence of build – a daunting task, but a valuable comparison with the absolute simple method of the design and construction of a monotube boiler. At the moment his D10 engine is a bit “stiff”, but once the newness has worn off, I think the tug will perform well.

Ian.
Title: Re: Flash steam plant control.
Post by: flashtwo on August 08, 2011, 10:40:38 AM
Hi Mayhemers,

Yesterday Vital Byte (VB) was successfully steamed at the Southend Model Boat Club at Southchurch Park.

There was a slight hic-cup in the preparation of the boat last week when, in conversation with Alan Noble regarding his and Phil’s 4 metre HMS Daring outing to Southend, he mentioned that the Southchurch Pond was topped up with sea water (and also, it turned out, with road drainage). Well, as you may appreciate, VB has always pumped in its boiler feed water from the fresh water ponds and using sea water was definitely a big no-no.

Initially I was just going to take VB and show it a static model, but I was cajoled into modifying VB with it own on-board fresh water supply. So I fitted a 1 litre drinks bottle, calculated to give me 20 to 30 minutes of steaming, and blanked-off the feed water intakes. With a quick run in my test tank to prove it would run, off I went to Southend.

Unlike the Guildford show, I was able to get VB up to a useful rate of knots with a good bow wave, centre crest and stern wave, plus plenty of manoeuvring in the floating “harbour”. Keeping an eye on on-board water supply, VB had five runs of about 20 minutes each making full use of the size of the pond. VB’s five foot length looked tiny up against the 4 metres of HMS Daring – the displacement comparison was 35kg against Daring’s 250kg!

I had a temporary problem with direction control, which I couldn’t tell if it was caused by the gusty wind or the rudder not responding – the water was so opaque that I couldn’t see the rudder movement. On bringing VB back to shore, I found the rudder servo connector needed wiggling to solve the problem.

It was handy, in a way, to have the on-board feed supply, since I could see if the boiler was filling up on the initial start and the pumps were functioning correctly. I did manage to top up the supply whilst the steam plant was still running.

VB is now “salt-water” capable!

Having proved that the new vertical monotube boiler arrangement is satisfactory, I’m going to change the gas cooling trough to a cooling pipe fed from the pond, which will save me topping up the trough every time I put the boat in the water.

VB will be steaming again at the Herne Bay Festival Regatta run by the Heron Model Boat Club on the 21st August 2011.

My thanks to Terry Moffet and everyone at the Southend Club for arranging such a good day.

Ian.
Title: Re: Flash steam plant control.
Post by: Xtian29 on August 08, 2011, 08:38:22 PM
Well,  I think nothing short of a full "Reverse osmosis" plant is needed here! It goes without saying that it would be completely autonomous, and would only be fitted to end the irksome task of visually monitoring the feed water supply level, and also I suppose because you can.....:o

I thoroughly enjoyed the visit down south. I passed through some old haunts like Bracknell, Broadmoor! and Camberley on the way to Guildford. I wish I had brought a list of the imperial reamers and taps and dies that my Stuart D10 build is going to need. Never mind, I got a brand spanking new 1" NPT tap for £8 off one of the stalls for my brewery ( It is a USA pipe thread, required for the 4.5kW heater elements)

I am building a water pump, and have hopefully conned my "secret sponsors"  into obtaining an electric motor with a 100/1 gearbox from RS

I forgot to "feel" VB while it was at full throttle to get a sense of the vibrations it generated, although it seems from the lack of 360 degree ripples, that it is not a problem, but I will be actually be sitting in my boat, so I don't want to develop "whitearse" from the dreaded vibrations :o

Is there any heads up on the publication date of your article? I emailed the mag for a date, but got no answer. Hopeless!

By a strange coincidence, and totally unconnected with my powers of persuasion, my "sponsors" have just started using picaxe chips to build up all the R&D circuitry we need for "mood lighting" drive motor control for "electric spoilers" etc. We have now got the £60 software to directly test the circuitry in a virtual circuit and also generate the PCB layout ready to be sent off for PCB manufacture. We were using dedicated little micro controllers at about £90 each, but the electronics boffin is well pleased now I have pointed out the error of his ways, and set him on the path of picaxes. This means we will soon have an in house picaxe boffin who can help me write some sort of control program, something which I feel is well beyond the wit of ordinary man, namely me.

Looking forward to all progress

Rog, AKA "Silverbrewer"
Title: Re: Flash steam plant control.
Post by: flashtwo on August 09, 2011, 06:51:04 PM
Hi Rog,

I read somewhere that the PICAxe project boards software didn't handle negative numbers and that their standard code for driving servos caused glitches every now and then. Things may have changed, but its something to consider when using them.

Any vibrations on the D10 are mainly caused by the pistons hitting TDC or BDC, something to be eliminated by careful machining of the piston rod to the correct length ( I have built up a selection of them!) and allowing for any up-down slack on the main bearings.

I did make a vibration head out of a musical Christmas card piezo sounder, mounting it on a magnetic base and displaying the signal on a 'scope along with the shaft pulse signal. By using a protractor, I could determine exactly where on the cycle the peak vibration occured.

I'll try and find out about the possible publication date.

Ian

Title: Re: Flash steam plant control.
Post by: Subculture on August 09, 2011, 07:27:05 PM
You can use the 'pulse out' command for servo control instead of the 'servo' command on Picaxe. it works just as well, but has no glitching issues (which I belive only affected some of the lower spec Picaxe microcontrollers, now superceded).
Title: Re: Flash steam plant control.
Post by: flashtwo on August 10, 2011, 09:04:38 AM
Thanks Subculture for clarifying the glitching problem on the PICAxe boards.

Ian.
Title: Re: Flash steam plant control.
Post by: Xtian29 on August 10, 2011, 05:13:59 PM
To counteract the Picaxe chip negative number thing, I believe you tell it to treat a number somewhere centrally placed within it's count range as zero. I do not have a manual handy, but they count from zero up to let's say 255, and if you add one more to the max number it can cope with it cycles round to zero.

So making it treat 127 as zero gives you zero, with >127 indicating a positive result and <127 indicating a negative result, within the constraints of it's max counting ability.

I assume there is no reason why the arbitrary zero point cannot be set to a lower point if there is not much expectation of large negative numbers and a larger positive range is required, like you would need if you were to be mad enough to make a jet steam engine that melted things for instance  :}
Title: Re: Flash steam plant control.
Post by: flashtwo on August 10, 2011, 11:35:20 PM
Hi Rog,

Yes, you're right. You can use the most signifcant bit (bit 7) as the polarity indicator - if it is zero then the bits 0 to 6 represent a positive number and conversely, if set to 1 then the other bits represent a negative number. You can use this with any number of bytes representing a single variable, with the most significant bit in the most significant byte defining the polarity. It is this method that is used in my code written in assembly language.

Although I have never used the PICAxe boards, I thought it may have been the supplied suite of higher level functions ( + - * / ), that had the negative number problem - I'm most likely wrong and it would be good to knock this one on the head.

Regarding the steam jet engine - I'm just starting on the new experimental version now that Vital Byte's vertical boiler is working satisfactory.

Ian.
Title: Re: Flash steam plant control.
Post by: Xtian29 on August 21, 2011, 04:12:05 PM
I have got myself an electric motor with a 100:1 gearbox for initial testing (RS 417-9661) which is exactly the same as the one in Vital Byte. Do you have two fitted because you thought redundancy on the pump would make sense, or have you actually had problems in the past that made two pumps a necessity? If so, and just for interest, which part gave the problems, the motor or the valve balls? Do the pumps have individual water inlets to cover for blockage at the inlet? I will get another pump motor later ...

I am doctoring a pump drawing I have, ( from Ray Hasbrouck No 8 engine plans) I am doing it half size, and in metric, which equates to 1" stroke x 1/4" bore and I will fit a 6 mm to 6mm drive coupling from RS. (748-320) Your Oldham style couplings were of your own making weren't they? Hopefully 6mm drive shafts will suffice as I wish to keep the weight down.

I have found a bearing supplier ( pt&bearings ) who supply "our" sizes of bearings at prices ranging from dirt cheap (for "cheap skateboard" kind of stuff,) to reasonably priced SKF quality. This is where I will source the bearings for whatever I make unless you guys know of somewhere better.....http://stores.ebay.co.uk/PT-AND-BEARINGS

Went to Smiths today to look at the engineering magazines, and found none! So either there is an upsurge in interest, or they aren't stocking them any more!  :o  
Title: Re: Flash steam plant control.
Post by: flashtwo on August 22, 2011, 10:20:01 PM
Hi Rog,

The prime reason for the two pumps was redundancy, but they are useful for:-

a) Boiler filling - the computer is instructed to run both pumps at full power just to speed up the initial filling of the boiler and engine.

b) Extra capacity - so that when the first ("A") pump is at full power the second ("B") can start delivering extra feed. The feed controller output is scaled 0 to 200% with      the "A" pump covering the 0 to 100% and the "B" 100 to 200% range. This was useful during the experimenting phase.

c) If there are any pond side problems, I can make the "B" pump the primary and the "A" pump the secondary.

d) The computer always monitors the speed probe pulses from the pumps and if the primary pump stops turning, the computer automatically switches to the standby pump within 6 seconds. This has happened once on the lake and I didn't notice until the boat returned to shore.


The problems that I have had are:-

a) Ram grease contaminating the outlet ball valve seat and preventing a good seal. This has been the most common problem, so that now I just use a drop of steam oil on the ram.
 
b) The brass seat becoming uneven for some reason and letting by. I re-seated it by using a sacrificial ball and tapping it with a small hammer. This has only happened once.

c) A motor bearing wearing out causing the motor to stick. I replaced the motor.

The pumps share an output from the water filter which has separate intakes on either side of the hull.

You must ensure that you have actual feed water flowing through to the engine outlet before igniting the boiler otherwise you will get slugs of very high temperature steam hitting the engine.

I did design the pumps so that both the inlet and outlet valves were accessable from above in anticipation of lake debris getting past the filter. A lot of pumps have to have their pipework disconnected to gain valve access whereas with my design the pipework stays connected.

I'm pleased that you are progressing, I'll be very interested to know how you get on.

Ian.
Title: Re: Flash steam plant control.
Post by: steamboatmodel on August 23, 2011, 01:42:57 PM
Hi Ian,
"I did design the pumps so that both the inlet and outlet valves were accessable from above in anticipation of lake debris getting past the filter. A lot of pumps have to have their pipework disconnected to gain valve access whereas with my design the pipework stays connected."
Could you post some on this design?
Regards,
Gerald.

Title: Re: Flash steam plant control.
Post by: Xtian29 on August 23, 2011, 06:42:06 PM
The pump design I am working to also has the valves accessible from the top without disconnecting pipes. Also, if the pipes are undone, the entire pump head is removable from the cylinder for quick replacement of the entire valve block. It has butyl "O" rings and a small oil cup for the piston Your pumps looked to be very compact, so I would also like to see drawings if they exist, especially your micro-Oldham couplings

If I make the pump as an exact half size copy I will get a 3/8"bore X 1" stroke. Do you think two pumps this slightly larger size will make sense given that my boat may need a bigger engine than the D10 at some point, and also perhaps a bigger boiler.   How often do find you need to run both pumps in unison during running, or was that used only during the early experimental phase? Does your software change which pump is the "master" so each pump sees the same number of hours use, just like the pilots had to do with the twin turbine engines in the Fairey "Gannet"?

A half size Ray Hasbrouck  No 8 engine would give a double acting .937"bore x 1" stroke V twin. I obviously cannot give any details of the drawings out as it would infringe the terms of purchase, but suffice to say, anyone half interested in engines would thoughroghly enjoy the 7 large sheets of impeccable drawings, which also come with a couple of colour photographs and full instructions. Should cost about $30, but check the net. Worth every penny.  I was so impressed I bought all his other plans just for the read.....

It is my intention to use standard brake pipe flared ends and joiners to connect the pipe in the monotube, and I was also going to make the ports of my pump and any other parts follow the designs found in a standard metric automotive brake system, IE the female sockets found in brake callipers. Is there any reason that this is a bad idea, as I am not familiar with either the imperial steam pipe fittings that model makers use, or their metric equivalents if they exist. All the cold water side could be plumbed in the plastic pipe and tiny brass olive seal system (SMC) cars use on their air suspension systems. Probably simpler to make and buy, plus a bit lighter! I will investigate.....

The fact you knackered a set of motor bearings vindicates the use of a decent set of support bearings for the pump rather than simply fixing a crank disk to the output shaft of the gearbox, which crossed my mind.

Any news on the publishing date yet? I'm going to have to pop down south to read your original "scribbles" at this rate!!  :}
Title: Re: Flash steam plant control.
Post by: Xtian29 on August 29, 2011, 07:05:53 PM
I have been looking for some way of having a mechanically driven water pump that is adjustable for flow, so I can use your control system but not have the need for powerful batteries.

I have just seen a pump in the book by K N Harris .... "Model stationary and marine steam engines" "second edition" fitted to a paddlewheel engine that may just fit the bill. It is on page 73, and further detailed on page 76. It could have it's stroke controlled via a servo.

http://www.fastonline.org/CD3WD_40/JF/424/19-423.pdf

It has a tiny air accumulator in the system to take out the hydraulic pulses that may exist in such things and it seems very compact, but my main interest is in the fact that I could prime the system mechanically or electrically,get the engine working and then switch over to  the engine driven pump.
Title: Re: Flash steam plant control.
Post by: flashtwo on August 30, 2011, 06:06:43 PM
Hi,


No news on the publication date as yet.

My software is designed for a flow from a mechanical pump if I ever fit one. The engine speed would be used to calculated the feed from the mechanical pump and, as the mechanical pump's output increased, the electric pump would slow down or even stop automatically and vice-versa.

I still think an electric pump is very useful for starting and also caters for when the engine is required to accelerate and decelerate or even stop mid-lake under radio control. I suppose if your boat is manned you will be able to have additional controls like pump bypass.

Whats a micro-Oldham?

The motor bearing failure was actually at the non-drive end near the commutator. The pump has a ball-bearing block that absorbs all the trans-axial force of the ram so that the motor and its gearbox are just affected by the rotative forces. If you go back to the original post of this thread, you will see photos of the pumps.

Regarding matching the pump size to the engine size can be a bit of an experiment. I did note that the effective flow of my pumps under pressure, was about 86% of that expected from the calculations suppossibly caused by the valves not seating immediately and passing. Based on my experience, I'm getting 500RPM at 20psi with the D10 with a flow of about 75cc/min (using the 86% correction mentioned above) - this could be a good starting point.

Currently I don't require both pumps to run to achieve the 500RPM objective. If the pump battery is low in volts and the main pump can't maintain the flow, the second pump will come in automatically to compensate, but this is only if I've forgotten to charge the batteries.

On an earlier software version the computer actually logged the total number of strokes per pump per run and per season, with the intention of some "preventive" maintainance in replacing the ram "o"-ring and ball valves and, like you suggest, running the pumps evenly - this was getting a bit daft I thought. From an industry point of view though, one thing you don't want is your standby bit of plant to wear out the same time as the main plant. I've known some instances when some plant has only logged 20% running time and then had an overhaul, principly because you haven't the resources to overhaul every item at the same time. Different for aircraft I suppose!

Regarding the pipes being used. The flared pipes would be easier than using the pipe nipples and silver soldering them on. Beware that even this small pump of mine can deliver 300psi or more!


The drawings that I have done myself won't scan very well since the lines are very fine.

I have however produced a set of typed sequential instructions that I use in the workshop, since I have built a number of the pumps for experimenting with. I'm afraid the measurements are in metric and imperial, since the metal stock is in imperial and the workshop lathe and milling machine are in metric. The instructions are three pages long and may be more suitable as a personal message than in the open forum.

With this type of pump it is very easy to get air trapped inside so causing the pump to fail. To get around this problem stainless steel blanks are fitted just above the ball valves to take up the volume that the air would have used. The blanks can also be machined to limit the lift of the ball valves. The ball valves make a seal directly with the brass body without the need of "o"-rings.

The batteries are oversized for the job they do. I could use much smaller ones for a days steaming, but the larger batteries are also used as ballast.

Ian
Title: Re: Flash steam plant control.
Post by: Xtian29 on August 30, 2011, 07:09:29 PM
Hi Ian,

The drive couplings you have on your pumps are called "Oldham" couplings, unless I am mistaken, and you have made rather small and neat ones compared to the ones I can see are commercially available at RS. hence "micro Oldham"

I would gladly receive sequential instructions in a PM  :} It keeps me away from the telly....
Title: Re: Flash steam plant control.
Post by: Xtian29 on November 25, 2011, 05:58:14 PM
I was wondering if there is any update on the magazine article?

At the moment, I am tarting about with the peristaltic pumps I have designed and built for my brewery, and their performance leads me to wonder if they could be used as boiler feed pumps?

The tube I use in my brewery pumps is 15mm ID 3 mm wall soft silicone, and it would be a good idea to test what sort of pressures can be developed if the tube size is drastically reduced to say 1 or 2 mm ID, using the stuff that is used as model aircraft fuel line. The limit will be the burst pressure of the tube....

 I would not be at all surprised if the pressure these simple pumps can produce is quite high, and given that there are no pistons to lubricate, or valves to get blocked, and they are self priming, it may be worth investigating, but if they were indeed a viable option , surely someone would have done it by now!! Has anyone seen mention anywhere of such tests?

While building the brewery and making beer remains the highest priority, I will try to do some testing on a little pump sometime soon to see what pressure they will pump to!

Rog.
Title: Re: Flash steam plant control.
Post by: Xtian29 on December 21, 2011, 04:51:06 PM
It seems the magazine article will be in the February edition of engineering in miniature magazine. The Jan edition is out now, so start looking in a few weeks.
Title: Re: Flash steam plant control.
Post by: derekwarner on December 21, 2011, 08:15:02 PM
This will be interesting Silverbrewer & it is good to see you have your priorities sorted  {-)

I tinkered with a minature peristaltic pumps 20 years ago....the burst pressure of the DUBRO silicone hose was never an issue....BUT keeing the tube attached to the pump ferrules was......

Even with DUBRO hose clamps........@ 15>20 PSI the slippery silicone tubing displaced it self off the ferrule....attempeted brass ferrules with sharper serations & they simply cut the tube ....

Keep us posted as the concept is great O0.....Derek
Title: Re: Flash steam plant control.
Post by: Xtian29 on December 31, 2011, 07:10:53 PM
It looks like the magazine article will be in the February edition of Engineering in miniature. The Jan. edition is out now, so mid Jan I suppose before it hits the shelves. I've ordered mine!!
Title: Re: Flash steam plant control.
Post by: flashtwo on January 08, 2012, 11:53:04 AM
Hi,

"Vital Byte" and "Vital Thrust" will be exhibited at the annual London Model Engineering Exhibtion 20th to the 22nd January, Ally Pally. They will be on Stand S, "A Team Boatyard" alongside the 14ft HMS Daring and other large "items".

Looking forward to having a good old chin-wag.

Ian.
Title: Re: Flash steam plant control.
Post by: flashtwo on January 13, 2012, 08:59:36 PM
Hi Mayhemers,

I've been investigating a problem that developed towards the end of September last year, but didn't have time to sort out.

Under hard steaming conditions with the gas valve fully open, Vital Byte was issuing flames from the top of the stack and the performance was deteriorating.

It was obvious that there was not enough combustion air to burn off all the fuel in within the boiler and I found that the stainless steel mesh scroll (see 2nd June 2011 posting) had developed deposits caused by combustion within its structure. Blowing through the mesh indicated a lot of flow resistance. I've replaced the scoll with a single layer mesh fixed across the top of the burner "bowl" and the combustion has much improved and you don't get that incomplete combustion smell either.

Today, I've been running under cold conditions of 5degC ambient and, despite using liquid fuel from the gas cylinder, found the performance was not up to scratch. With a 5degC cold full gas cylinder I found the gas pressure was at 2bar, but heating a full cylinder in warm water at 25degC the gas pressure went up to 4 bar and the performance was much better. Because the gas cylinder is inverted, the gas doesn't evaporate in the cylinder and hence the cylinder maintains its warmth much longer.

Roll on summer!

Ian.
Title: Re: Flash steam plant control.
Post by: ooyah/2 on January 14, 2012, 11:52:17 AM
Ian,
I experienced the same problem early on in my flash steam project.
I wanted to burn L.P.G  originally so I set up a roaring type burner and a copper gas tank with the burner firing into an A.A. Rayman design boiler.
The burner had a .025" jet and brass vaporiser coil on the end.
Before setting it up with the boiler I tested it just as a burner on the bench, heated the coil with a plumbers blow lamp, as I was burning liquid, coil getting a bit red, opened the liquid valve and away the burner went.
Great I thought it's burning well, after a few minutes all hell broke loose as the liquid came shooting out of the burner like a flame thrower and set the inside of the garage door on fire, quickly shut down the valve and  it was fortunate that it was a flash fire so no damage done, C.O. 2 extinguisher now installed at bench.

When installed in the test boiler it worked well but was inclined to flame and then would go into the cycle of cooling and losing pressure due to the size of the jet and the amount of liquid being drawn from the tank, heating the tank with a gentle application of the plumbers blow lamp increased the flame strength.
The burner seamed to work better when firing into the boiler space, possibly get more air sucked in, with the occasional flame out from the boiler exhaust.

Eventually I deduced that to get the power from the L.P.G. I would need a massive tank to supply the burner and stop it freezing, went on to paraffin.

Where does all this lead to your problem.
The out side temp of the tank is one, looking at your burner , is the tube too thick to allow it to glow hot and vaporize the liquid?
I found that the outside shell works better at .025" thk.

Do you still have so much tubing in your coil which could be preventing combustion ?
I found that the more space around the coil and the coils spaced about 1/4" apart was about correct, but then my aim was for power that your coil can't produce.

No doubt you will solve the problem when it gets a bit warmer.

Here is a pic of the experimental burner and A.A.Rayman boiler, burner is now fired by pressurized paraffin, this was an early experiment before my final  
triple burner.

Hope this helps.

(http://s18.postimage.org/4xpk8icr9/Scott_Boiler_Engine_1.jpg) (http://postimage.org/image/4xpk8icr9/)

(http://s16.postimage.org/sw0640ykh/Scott_Boiler_Engine_6.jpg) (http://postimage.org/image/sw0640ykh/)
Title: Re: Flash steam plant control.
Post by: flashtwo on January 24, 2012, 11:21:52 AM
Hi Mayhemers,

I know one shouldn't advertise, but "Vital Byte" has left me a personal message (something about a certain magazine article I assume):-

Ian
Title: Re: Flash steam plant control.
Post by: flashtwo on January 24, 2012, 12:03:09 PM
Hi Mayhemers,

I’ve investigated the reduced performance a bit more and have noted that, with the gas control valve fully open, the burner noise was much less than expected and the outlet pipe from the gas control valve was frosting up badly. This indicated a partial blockage in the gas valve causing a throttling effect which made the assembly act like a refrigerator.

Sure enough, on dismantling the valve it was blocked. I cleaned it out and normal service was resumed.

At the London Model Engineering Exhibition last weekend, where “Vital Byte” was on display, I discussed this problem with a couple of visitors. One chap had had a similar problem with his gas fired steam loco and found that a waxy substance from the gas cylinder had caused the blockage. He had fitted a “coffee paper” filter (the cigarette filter he tried caused problems with its fibres)  and this stopped the valves blocking. With the gas cylinder inverted perhaps this encourages deposits to be expelled from the cylinder.

Another good tip from the same guy (16mm gauge loco enthusiast) was regarding the burner mesh. He is using a nichrome mesh instead of stainless, since it degrades far less with the heat. He makes his own mesh from wire using a pin board.

Another visitor had built his own manned steam canoe incorporating a monotube boiler. He thought my system was a bit complicated, but I did remind him that I wasn’t onboard to adjust things unlike himself.

Anyway, there was lots of interest in “Vital Byte” with very much welcomed advice from visitors and other exhibitors alike.

My favourite exhibit was Jack Snary’s (and expert grandson) “Royal Spithead Review” with it hundreds of miniature ships detailing naval history from Ancient Egyptian times up to the present.

For the next part of the project, I will be rebuilding the timing linkages on the D10 engine, since they are very worn and sloppy.

Ian
Title: Re: Flash steam plant control.
Post by: TurboTyne on January 24, 2012, 12:39:47 PM
Hi Ian

I've just read your excellent article in EiM. I think it is very interesting and I look forward to the next part. The trouble you take to explain the principles of computerised control to the wider audience reminds me how much I have learnt since I last pestered you with questions - which was over a year ago now. Before I saw your blog about Vital Byte I had not heard of PIC devices at all. Your advice was not wasted because, since then I've learnt a lot about PIC programming. So far I have constructed a gas burner and a needle-type gas valve operated by a stepper motor which is controlled by a PIC. This PIC receives instructions from the master temperature monitoring PIC via the I2C bus. The latter master PIC also sends data to a display PIC and to a serial EEPROM which can be removed and (I hope) have it's data read into a PC via a cheap USB-I2C interface that I've bought. So I am getting near to having a temperature controlled gas valve - but a lot more work will be needed before I know if all this effort will give a workable boiler control system.  It's been great fun learning all this - thankyou for showing me the light.

Regards,  Mike
Title: Re: Flash steam plant control.
Post by: flashtwo on January 24, 2012, 02:24:33 PM
Hi Mike,

I think its great that you've made such progress - I shall be asking for your advice very soon, especially about I2C.

How do the stepper motors compare with the ordinary radio control servos - do you have to set a mechanical starting point of reference, or have they developed since I last used them many years ago?

Have you used anything like picAXE boards?

Will you be using your burner with a conventional boiler or a monotube?

Thanks you your EiM comment - any feedback will be appreicated.

Ian.
Title: Re: Flash steam plant control.
Post by: TurboTyne on January 24, 2012, 08:11:07 PM
Hi Ian

Always happy to chat but I doubt I could add much to your knowledge.
I have never used (or even seen) a radio control servo. My lack of familiarity with them is one reason I chose to go down the route I have. My hobby activities have been in model engineering etc and I felt inclined to have a go at making a valve from scratch. Also, I've long wanted to have a go at trying to use a stepper motor - for something or other, mainly so I'd properly understand how they function. This was undoubtedly not the most efficient way forward to make a boiler control system and for that I should have followed more closely what you have done with servos etc. My efforts have taken much time and the valve is not exactly compact. The stepper (taken from an old ink-jet printer) does, as you say, lack any points of reference. I've attached a couple of photos which show the arrangement  I came up with. Movement is by a screw which drives a block attached to a lever. The 40 tpi thread and the 5:1 lever combine to give a very fine adjustment of the valve rod such that about 10 turns, each with 48 steps, are needed to fully open the valve. The limits to movement of the screw-block are by the optical sensors - the black blocks with a central slot. As I'm sure you recognise, the thin metal sheet attached to the screw-block goes into the gap in the sensor and blocks the light beam. I am new to all this and was amazed at the accuracy of these particular devices. I estimate the electrical output goes from full on to full off with just 2 or 3 thou movement of the block. Of course the sensors connect to pins on the PIC (16F818). The programme includes a few lines of code which ensure that, when the direction of the motor is reversed, a few extra steps to the movement are inserted so as to take up the slack in the mechanism.

No, I did not use the picAXE items - I just ordered PIC chips from Farnell. Another thing thats amazed me is the amount of free stuff they provide. I use their free MP LAB IDE programme for all my programming in conjunction with a Pickit3 programmer.
 
RE: the boiler. I shall initially be messing about with a monotube boiler coil that I actually wound over 40 years ago - but never used. I had dreams of making a flash-steam hydroplane, but now I am aiming for something more sedate - but definitely monotube.

Mike

(http://s12.postimage.org/5b5ptox95/IMG_2963r.jpg) (http://postimage.org/image/5b5ptox95/)

(http://s11.postimage.org/grqdgbwi7/IMG_2970.jpg) (http://postimage.org/image/grqdgbwi7/)
Title: Re: Flash steam plant control.
Post by: Xtian29 on February 28, 2012, 07:30:38 PM
The second and final part of the article is in the March issue of Engineering in miniature, and is on the shelves now.....Don't miss it!
Title: Re: Flash steam plant control.
Post by: flashtwo on March 02, 2012, 09:02:32 PM
Hi Mike,

Thanks for sharing the gas valve photos. I've just replaced my gas valve servo (£7 type) with a more expensive all metal gear and spline type (£!), because the plastic spline of the original servo was getting chewed up with the clamping grub screws.

I used to set the closed position mechanically by loosening the grub screws and rotating the gas valve shaft. Now I can set it accurately by setting  values on the display screen, which nominally set the fully open position to 1000us (PWM) and fully shut to 2000us. If the gas valve hasn’t fully shut then I can increase the 2000us value to say 2100us and the servo travels a bit more to shut the valve – the controller remembers this position even when powered off.

I’ve been carrying out some pump flow tests today, since I thought the “A” pump wasn’t performing well. I replaced the steam pipe between the boiler outlet manifold and the engine with one containing a flow control valve with the outlet going to a laboratory 500ml measuring cylinder.

I measured the pump flow over a three minute period with and without constrained flow  - the constrained flow made the pump work against a pressure of about 50 to 200kPa (7 to 30psi).

I found that the displayed flows (“A” &”B” pumps) were reading about 7% lower than that recorded by the measuring cylinder. This can be corrected by amending the pump capacity in the controller.

I’ve recently rebuilt the timing linkages of the D10 engine, since the wear on the original quadrants was making accurate timing impossible. New quadrant bronze castings were obtained  from Stuarts. This time I made a jig to fit on the milling machine’s rotary table, which enabled me to mill the quadrants to the exact radius without resorting to tiresome filing. I also found that I had limited the travel of one of the quadrants when I had originally built the engine 4 years ago – I repinned the linkage to the correct position.

I also tightened up the eccentric straps to reduced the slack.

With both the above overhauls completed, the valve timing setting was greatly improved.

With the above sorted out, I gave Vital Byte a run in the test pool with very good results.

From a low last July of 380RPM (max) with flames leaping out of the stack and very hot boiler casing  -  to a performance today of 590 - 620RPM (peaking at 710RPM) with no flames leaping out the stack – in fact I could place my hand over the stack, on the stack and on the casing without it being unduly hot, indicating a very efficient boiler.

The flaming problem, as discussed in earlier posts, was caused by the mesh in the burner bowl corroding up and limiting the airflow into the boiler.

Ian.
Title: Re: Flash steam plant control.
Post by: flashtwo on March 10, 2012, 01:27:39 PM
Hi Mayhemers,

Here’s a series of photographs show the latest development of “Vital Byte”.

The first couple show the jig made for milling the timing quadrants (octants?) more accurately and quicker than by filing. The dimensions ensure that the exact radius is kept around the piece and a 4mm end miller cuts the correct dimensions.

In the other photographs the new compact water filled gas heat exchanger is shown with the reconstructed burner and the vertical boiler.

From the burner photograph you can see that the liquid fuel enters a the union furthest away, does 3 ½ turns around the burner in 1/8th copper pipe and gas exits at the tee-piece where some is tapped off back to the three pilot lights spread around the burner, which also heats the liquid fuel evaporation coils.

Above the burner is some 1.8mm pitch stainless mesh, which is surviving better than the scroll of mesh originally in the burner bowl. The mesh ensures that the flame doesn’t propagate to the nozzle.

In the previous setup, the exit gas pipe lay in an open trough of water to cool the gas before it entered the servo gas valve, which had an “o”-ring seal and a lead soft seat, both of which I didn’t want to overheat.

The gas exiting the gas valve, when heavily throttled, can come out freezing, so that pipe was put through the same trough to warm up before going to the burner nozzle.

The trough had to be filled with water before running the boat, so a replacement design was installed, which was connected to the incoming feed water from the lake. This design would automatically fill when the boat was floated with the vertical silicon tube indicating that it was full.

With this arrangement, the problems of cold weather operation are eliminated with no gas evaporation taking place in the upside-down cylinder and also all the fuel is used from the cylinder. One has to be aware of any fuel residues blocking the gas valve, so I allow a full flow blast of gas through the valve before reshutting the valve, and allowing the gas to disperse before igniting the pilot lights.

Looking forward to Wickers, and special thanks to the Wickstead Model Boat Club and Martin for all their efforts.

Ian.
Title: Re: Flash steam plant control.
Post by: flashtwo on March 23, 2012, 12:21:16 PM
Hi Mayhemers,

Subsequent to the feed pump tests, I've made some additions to the Display menu (see photograph) and software.

I can now update the pumps' capacity in mm^3 to give a more accurate display, and can also swop over which is the Master Pump without having to swop the ESC and shaft pickup connectors on the interface board.

From the menu I can choose whether the "A" or "B" pump will the Master with the other acting as Stand-by.

"Vital Byte" is getting ready for Wickers - hopefully with a fresh coat of paint!

Ian

Title: Re: Flash steam plant control.
Post by: essex2visuvesi on March 23, 2012, 12:45:24 PM
We must all bow down before the almighty B pump!

(http://www.myemoticons.com/images/emotions/awad/bow-down-together.gif)

It is written that it shall be master






Sorry slow afternoon in the office  :embarrassed:
Title: Re: Flash steam plant control.
Post by: flashtwo on March 29, 2012, 09:48:00 AM
Well the "Almighty B pump" wasn't to be bowed down to!

The non-return valves needed to be re-seated, since they were letting by (see "simple feed flow indicator" thread).

Over the last year I have had problems with the gas control valve blocking up causing a much reduced performance of the boiler. I had been lead to believe that using the gas cylinders upside down would allow waxy deposits from the cylinder to pass through the system and eventually blocking the valve. Well, I've dismantled the valve several times and poked a fine wire through to open up the valve and, although I couldn't see any waxy deposit, the valve did clear.

After only one or two runs the valve would block again. This time I opened up an empty gas cylinder to find the "fabled" waxy deposit only to discover the inside of the cylinder was totally clean with not a hint of the "wax".

The actual valve seat is made of lead with a small needle size hole. This soft valve seat, I suspected, had been deformed, over time, by the valve plug and being repeatably partially closed again after I had cleared it with a fine wire. This time I drilled out the hole to 1mm dia. and so far the blockage has not re-occurred and the performance is the best for ages. I think the recently fitted high torque servo may have contributed  to this deformation of the seat.

Another reduction in performance was caused by a sliver of silver solder that had travelled down the gas pipe to the nozzle causing throttling and frosting up at the nozzle. If ever you see frosting up it seems to indicate a partial blockage.

The gas cooler arrangement has been changed with the feed flow being drawn through the cooler as the gas was getting too hot at the valve. I think I will have to reduce the length of the evaporator pipe around the burner as it is heating the gas too much.

Ian
Title: Re: Flash steam plant control.
Post by: flashtwo on April 14, 2012, 10:55:12 PM
Hi Mayhemers,

Having solved a few things that were restricting the power output (engine timing and fuel gas obstructions), I've been experimenting with some of the control system settings.

From previous posts and the magazine article, you may know that the steam temperature desired value is offset by the feed demand, i.e. the higher the feed demand the higher the target steam temperature.

Well today I've run the plant with both pumps running at full speed (170cc/min indicated), with a steam temperature at 145degC (controlled!) and achieved a remarkable 720RPM running (not peak) and steam pressure at 300kPa (45psi). You can imagine that, with the 5 inch prop, the water was quite turbulent especially slamming into astern then ahead.

Normally I've been running with a single pump and getting 530 or so RPM with a gas consumption of about 4.5grams/min, which would be more than adequate for the model boat. I think 720RPM would be showing off! Perhaps the boiler is now oversized at 250sq.inches for the engine.

By the way, are there any questions from those who have read the magazine article (its gone rather quiet)?

Ian
Title: Re: Flash steam plant control.
Post by: HS93 (RIP) on April 15, 2012, 12:47:37 AM
the Post has been going on for some time so is there any chance of a run down of what the system now does in the finished state as I think from day one it has changed so much and it would be nice to know what is possable with steam in the modern world, thanks forthe informative Post.

Peter
Title: Re: Flash steam plant control.
Post by: flashtwo on April 15, 2012, 02:26:03 PM
Here is a breakdown of the current situation:-

Engine: Stuart D10 double cylinder, double acting, ¾” bore by ¾” stroke, driving the
             Propshop’s 5 inch prop designed for the D10.

Boiler: Vertical Monotube, 50foot of 3/16 inch copper brake pipe wound in three
             layers.
Boiler dimensions: diameter 108mm, Height 270mm plus 190mm stack.

Electric pumps (2 off): Feed rate 85cc/min each. Filtered Pond water is used.

Fuel: Butane/Propane in liquid form with evaporator on burner.
         The heated gas is attemperated by a cooler fed with incoming feed water.

Burner: Jet 0.7mm dia., mixing tube ¾” dia., 100mm long, Stainless bowl 1¼ “ dia. with 1.2mm pitch mesh to prevent flashback to the jet..

Fuel consumption 4.5g/min at 530RPM.

Currently achieving 720RPM at 170cc/min feed and 45psi, 145degC steam conditions.

The exhaust steam is directed to an oil separator / feed heater (dia.50mm, height 225mm plus 108mm high vent pipe). The oil free water is dumped overboard.

Control system:
PIC based microcontrollers monitoring the feed pumps’ strokes per minute, steam temperature and pressure and the gas cylinder pressure.

The demanded feed flow is set at the radio transmitter and the controller, via ESCs, ensures that the pumps maintain the flow independent of the boiler pressure.

The steam temperature has a manual setting that is amended by the demanded feed flow, such that, as the feed is increased, the desired temperature is raised, which in turn causes an increased firing rate via a servo gas valve, raising more steam and an increase in speed
–   put simply more water in, more steam out and the faster the boat goes.

The controller has a start up mode such that the boiler is warmed up at a optimum rate to the boiling point without over firing and causing excessively high temperatures. Being a monotube boiler, it takes only a few minutes to raise pressure.

There are a few safety features: high temperature shutdown of the gas valve, high pressure shutdown of the gas valve and pumps, pump failure detection and standby pump cut-in. The boat automatically restarts itself if any of the above occurs.

Current problem: the stainless steel burner mesh crumbles away after about 5 hours running and is to be replaced by a ni-chrome mesh once I’ve woven it!

Was it worth it? The initial objective was to build a simple cheap boiler that didn’t require insurance or annual testing. Well the boiler is certainly cheap at £60 (£20 copper brake pipe, £20 toilet brush holder boiler casing, £10 brass stack, £10 sundries) perhaps a tenth of the price of a conventional boiler. Certainly it is very simple to make with only two silver soldered connections, plus one joining the two 25 ft lengths of copper. Not being a pressure vessel it is exempt from the test and insurance requirements.

At the project start, the best method of controlling the monotube boiler was a matter of debate and using a programmable system enabled many ideas to be explored without massive amounts of rebuilding mechanical and/or electronic controls. One thing you don’t have to worry about is the boiler water level!

So we have a boiler that is cheap, quick to start and runs as long as the fuel lasts (100minutes or more).

The controller hardware bits came to about £70 and took around a week to solder together, although it is transferable between models or even a full size boat.

The software is a totally a different kettle of fish, with thousands of lines of code, but, since completed, can be downloaded to the raw controller in minutes.

It took 2 years of experimenting (including pump and boat construction) to arrive at a practical solution with “Vital Byte” having it maiden voyage at Wicksteed in May 2009.

Where to now? I’ve got Selway Fisher plans of a 30ft steam launch and I’m just scaling them for the 5 inch prop; that determines that I build a 75inch launch to install the existing system in.

Now that I’ve broken the back of the problem, it would nice to know that other enthusiasts will take up the challenge and build a similar (perhaps better) monotube boiler system.


Ian

 


Title: Re: Flash steam plant control.
Post by: dreadnought72 on April 15, 2012, 02:55:10 PM
Ian, I'm very impressed with the set-up - but could you explain more about this line (maybe it lost something in your post):

Quote
There are a few safety features: high temperature shutdown of the gas valve, high pressure shutdown of the gas valve and pumps, pump failure detection and standby pump cut-in. The boat automatically restarts itself if any of the above occurs.

Is that the right thing to do? If a fault is detected, do you want it to restart with the fault not fixed?

Andy
Title: Re: Flash steam plant control.
Post by: flashtwo on April 16, 2012, 05:34:20 PM
Sorry for the confusion Andy,

During development and use, I adjust the response of the control loops so that they respond either sluggishly or lively to changes in feed flow command. If the controls are too lively then, on occasions, the steam temperature can get out of control and the system shuts down to protect the engine. The boat then sits on the pond and waits for things to cool down before it restarts itself and I can bring it back to shore. If it keeps happening, I then "detune" the temperature control loop to ensure only gradual temperature changes.

Actually discussing this has usefully reminded me (and duly entered in the boat's log) to put back the function of setting both pumps to full speed in case the gas valve jams in the open position; I commented it out of the software last week when I was doing some experimenting - a fateful mistake!

It was very amusing, when "Vital Byte" was steaming down at the Dover Model Boat Club's pond and it did shut down due to high temperature. The lads there were very keen to send out their electric tugs on a rescue mission, but I told them that the boat was in "auto-recovery" mode and would return (fingers crossed), which it did to their amazement (and mine!).

The high steam pressure shut down (which has never occurred) is there in case the prop fouls up with debris and stops turning.

I suppose the priority is to return to shore.

Thanks for your compliments and interest.

Ian.

Title: Re: Flash steam plant control.
Post by: flashtwo on April 17, 2012, 04:40:58 PM
Here are couple of photographs showing the crumbling stainless steel burner mesh and the weaving loom for making a ni-chrome mesh.

The weaving loom has two brass guides each with 60x 0.5mm grooves at 1.2mm pitch, mounted in a steel frame. I did consider drilling 120 0.5mm holes in a brass plate, but then thought the better of it.

The warp is wound around the guides. The two "tangs" are for mounting firmly in a vice as the weft is woven through the warp.

Once the ni-chrome is woven, it will be placed on a former and bent into a slightly domed shape in order to slide into the burner cup.

I can see this is going to try my patience!

Ian.
Title: Re: Flash steam plant control.
Post by: boneash on April 17, 2012, 05:08:05 PM
Quote
I did consider drilling 120 0.5mm holes in a brass plate, but then thought the better of it.

Oh come on now a milling machine, you have, and a Pic, 3 motors and a CAD package......

or  a xyz package off Ebay.....
Title: Re: Flash steam plant control.
Post by: flashtwo on April 17, 2012, 06:40:13 PM
ouch!

I don't want to wear out the milling machine, you might want to use it one day!
Title: Re: Flash steam plant control.
Post by: Mad_Mike on April 17, 2012, 09:37:01 PM
I dont know much bout steam but would these work?

http://www.ebay.co.uk/itm/PIPE-BOWL-GAUZE-SCREEN-METAL-RIMMED-STEEL-5-X-20MM-/170751019951?pt=UK_Collectables_Tobacciana_Smoking_LE&hash=item27c18dcbaf
Title: Re: Flash steam plant control.
Post by: HS93 (RIP) on April 18, 2012, 07:31:50 AM
how about  Bruce steam models they do some stainless steel for spark arestors will that work

Peter

Peter
Title: Re: Flash steam plant control.
Post by: flashtwo on April 18, 2012, 01:57:20 PM
Hi,

Thanks Mike for that suggestion - never knew they existed. My burner bowl is about 32mm diameter, so I'll have to make my own. I'm now thinking of a use for the pipe bowl filters.

Peter -  the stainless steel ones work fine until they oxidise due to the burner flame sitting just above it, especially at low gas flows. The ni-chrome wire, which is normally used for electric fires, should not oxidise and last much longer - I'll keep you posted with its performance.

In the mean time, I've found a new method of weaving called the "Scotty" method that enables you to finish before you've started - many an enterprise use it apparently, even up to warp speed 9! (yawn!)

Ian
Title: Re: Flash steam plant control.
Post by: flashtwo on April 22, 2012, 06:16:14 PM
Hi Mayhemers,

Now that I'm using both pumps to achieve "ramming" speeds (700RPM), the previous control philosophy to having one pump purely as the standby has changed somewhat.

I've made some software changes so that, if either pump stops reciprocating or there is a high steam temperature trip (possibly caused by a feed pump problem), the Feed demand is automatically halved. This ensures that the boiler feed requirement can be handled by one pump.

Another change is to now allow 10 seconds for the pumps to re-establish flow, after a trip, before the gas valve starts to open.

The steam temperature target, which is a function of the feed demand, has been further refined by allowing the equation parameters (offset and slope) to be set at the display and command unit whilst the boiler is running. (For the mathematical it is the old "y = mx + c" equation and I can now adjust m and c whilst running). This will allow fine tuning to take place.

....and not a soldering iron in sight!


Ian
Title: Re: Flash steam plant control.
Post by: flashtwo on April 24, 2012, 07:56:43 PM
Just to give Mayhemers a flavour of what is going on, here is a small part of the code that has just been modified for the new method of running with two pumps (without the use of the soldering iron!...)


TEST_A_RUNNING   
      BTFSC   C_FLAGS_6,1   ; (BTFSC) Times up! Is the "A" Pump running?
      GOTO   ENB_GAS_VALVE   ; Yes, the "A" Pump is running, therefore enable the gas valve to open.

      BSF   C_FLAGS_1,7   ; The "A" Pump is not running, therefore set the "B" Pump as Control Master.
      BSF   C_FLAGS_1,3   ; Set because one of the pumps is unavailable and the target T4_DV must be lowered.
      BSF   C_FLAGS_3,0   ; Set the "A" pump failed flag.

      MOVLW   D'100'      ; Set the pump established counter to 10seconds (100d) to allow the pump to start turning.
      MOVWF   PUMP_COUNT
      GOTO   DIS_GAS_VV              ; Disable gas valve from opening.

Ian
Title: Re: Flash steam plant control.
Post by: steamboatmodel on April 27, 2012, 01:32:12 AM
Ian 30 years ago I mite have understood it better, but I can sort of follow it through. When I my round tuit I am going to have to sit down and do more than glance at embedded C.
Regards,
Gerald.
Title: Re: Flash steam plant control.
Post by: flashtwo on May 04, 2012, 05:02:08 PM
Hi Mayhemers,

Since the gas control valve was drilled out to prevent it getting blocked, the valve characteristic improved such that the performance increased dramatically as previously reported.

With the increase gas valve response came a problem of overfiring when starting up resulting in high steam temperature trips. Apparently the rate of heating the boiler on start-up had less to do with my software controlling the heat input and more to do with the gas valve itself previously limiting the heat rate. The original code would set a target temperature value, wait for the actual steam temperature to catch up and then increase the target temperature to a new value.

To get around this problem a proper piece of software code was installed that enables the target temperature to be ramped up at a set rate. Although the code waits for the temperature to catch up, it won’t increase the target until a timer has expired. The start-up time, from ambient to boiling, can now be set  from anytime between 1 minute and 16 minutes.

Having now sorted out these remaining problems, “Vital Byte” has just had a pre-Wickers run down at Herne Bay with SWMBO taking a few photographs; she apologises for the stern shot since the boat was going “too fast”! Quite a strong hull wave was present.

“Vital Byte” performed without fault throughout her power range (100 to 600RPM) and could be stopped and restarted in the middle of the pond with ease. Going astern – no problem. Gas consumption 5g/min.

She (“Vital Byte” not SWMBO) is now going into dry dock for a repaint and final preparation before Wickers.

I suppose I’ll have to build the proper boat now that the controls are fully functioning!

Ian
Title: Re: Flash steam plant control.
Post by: steamboatmodel on May 06, 2012, 12:56:36 AM
Looks great.
"Having now sorted out these remaining problems, “Vital Byte” has just had a pre-Wickers run down at Herne Bay with SWMBO taking a few photographs; she apologises for the stern shot since the boat was going “too fast”! Quite a strong hull wave was present."
It looks like a classic case of here she comes there she goes and by the time the brain gets the message to the hand she is gone.
Regards,
Gerald.

Title: Re: Flash steam plant control.
Post by: Panoramix on May 17, 2012, 02:34:08 PM
Thanks Phil, that's much better.

It looks like one trough behind the bow followed by one crest before the prop, i.e. one wave length.

For those not familiar with the boat, there is a large overhang above the water after the prop (see earlier posts at last year's Guildford Show), which gives the appearance of a much longer hull.

Now, is the hull speed indicated by one wave length or one half wave length?

Ian

I was in admiration when I've read this and seen all the work and couldn't resist registering!

 I don't think that anybody has answered the question and although it is an old one you might be interested in the graph below:
(http://www.heliciel.com/images_didacticiels/froude%20resistance%20specifique%20types%20navires.png)

So basically to be at hull speed you need to have the crest of the first wave following the bow wave lined up with the stern (4th sketch from the left for Fn=0.4). I think that in your case there is still some speed to be gained before reaching hull speed. The distance between crests is proportional to the square of the boat speed, so roughly you are looking at 40% extra speed. If there is enough torque on the shaft a propeller with 40-50% more pitch would yield this.
Title: Re: Flash steam plant control.
Post by: flashtwo on August 13, 2012, 07:34:06 PM
Thanks Panoramix for the diagram - "Vital Byte" still appears to be somewhat short of achieving "hull speed", although its square hull section may be offering a lot of resistance.

I renewed the piston 'o'-rings last week (since the performance wasn’t up to scratch) before steaming her at yesterday at the Model Boat Association Dover annual meeting at Kearsney Abbey.

The weather was hot (first outing this year when it hasn't poured with rain!) and the gas cylinder pressure was up at 5bar (75psi) due to boat inboard temperature being at 40degC. On a cooler day the pressure is about 3bar.

The high gas pressure caused a significant amount of steam to be raised purely on the pilot flames causing the engine to tick along at 300RPM. What with the high gas pressure and new 'o'-rings, the boat's performance was the best ever with an average of 480 RPM for the first half-hour run and an average of 532 RPM for the second half-hour run. Previously the averages were in the region of 380 RPM. Maximum RPMs were off-scale >800RPM (RPM is scaled 0-800 in the software).

The hull wave still consisted of the bow, mid and stern components, but greatly enhanced with a very deep dip just before the stern wave – any deeper and I think the prop would be affected.

“Vital Byte”  gave a very powerful performance and no flames out of the stack this time! Fuel consumption was 4.3g/min – excellent considering the thrashing it was given – this would give about 1 hour 45 minutes per 460g gas cylinder and perhaps 3 hours just on tick-over.

In the mean time the building jig for “Vital Byte II” has been completed with the keel under construction.

Ian
Title: Re: Flash steam plant control.
Post by: TurboTyne on September 21, 2012, 01:41:19 PM
Hi Ian

It's a while since I've looked at this thread. For some reason not known to me, I stopped getting notifications of new postings so I'd assumed there were no new messages.



Now that I've broken the back of the problem, it would nice to know that other enthusiasts will take up the challenge and build a similar (perhaps better) monotube boiler system.



I just wanted to say, in response to your comment quoted above, that there is at least one person who has been inspired by your work, namely yours truly. I am still plugging away at my PIC-controlled boiler. Following your advice, I bought the 100rpm motor and then designed and built a PIC-based speed controller, using the application notes from Microchip. A PIC16F1827 measures the time to complete each revolution of the motor shaft via a Hall-effect sensor as per your VitalByte. It then calculates the speed as rpm and compares to the target rpm. It then uses a PID  feedback control routine to adjust the pulse width modulation output from the PIC.  Actually I had to turn off the D component to avoid speed cycling high/low – again similar to your notes on gas control. This output (at  PWM freq of 10KHz and a 400 step resolution) is sent to the motor via a MOSFET and MOSFET driver.  The target and actual pump speeds are communicated via the I2C bus to a PIC which drives the LCD  display and another which allows input of target speed and values of PID constants etc.   This seems to work O.K as far as I can tell at present. Eventually I plan that the pump control PIC will communicate with the Master PIC that measures temperature and controls the gas valve.  The gas control/temp part is already built and functioning. I'm currently nearing completion of a twin-cylinder feed pump (but only one of them for the present) that is coupled to the motor. So I am looking forward to connecting pump to boiler tube and burner control to see if I have anything approaching a working system.

Regards,  Mike
Title: Re: Flash steam plant control.
Post by: flashtwo on October 04, 2012, 02:46:46 PM
Hi Mike,

Marvellous!  Its great to know that you are making very good progress and also for using the I2C bus for the comms link , which is much more versatile than the serial comms that I use (although that was an improvement on the parallel comms that I had originally used!).

I would be interested in a block diagram showing the “architecture” of your control system. I placed all my master comms, control and servo drivers all in one 16F877 PIC, which put a bit of a strain on getting the software modules in the correct timing sequence, especially the comms code which had to be carried out without any interrupts enabled.

Have you had to put the interrupt handler at the very top of the code memory (005H?) so that interrupts can be handled from any memory page.

Its interesting the you experimented with the D part of the PID and came to the same conclusion. I never actually wrote any “D” code, since from experience in industry it was never very good – I found that feed forward control was very useful.

Have you seen my article in “Engineering in Miniature” magazine (Feb/ March 2012), which gives an overview of the monotube boiler control system?

Sorry I’ve not responded earlier, but, as you may see on the “Edwardian Steam Launch build” thread, that I’ve been a bit busy.

Photo shows VB at Herne Bay in August, chugging along with 10psi on the clock.

Ian.
Title: Re: Flash steam plant control.
Post by: TurboTyne on October 05, 2012, 08:19:16 AM
Hi Ian

" the I2C bus for the comms link , which is much more versatile than the serial comms that I use"
What serial bus do you use then? It took me ages to get the I2C to work. There was always the uncertainty of knowing whether the problems were in the master or slave PIC etc. Oh what joy when one PIC at last spoke to the other.

"I would be interested in a block diagram showing the “architecture” of your control system".

O/K., as it happens I was just preparing such a summary because I need to refresh my memory on this side of things, having just spent a couple of PIC-free months designing and building the pump.  Here it is. Each of the boards shown here has been built (3 are on veroboard but 2 are still on the breadboard) and all have communicated with 1 or more other boards, but as yet I have not interconnected them all in pattern shown in this diagram. This should be relatively straightforward (famous last words)  simply by changing the I2C addresses and ensuring the data sequences for TX and RX are correct.

"Have you had to put the interrupt handler at the very top of the code memory (005H?) so that interrupts can be handled from any memory page."

Actually I have not used interrupts at all. I have managed to steer clear of this complexity - it's been enough of a battle for me to cope with all the many other aspects of these devices  - I'm still amazed at what gets packed into a cheap device and at the number of pages in their data sheets.

" I found that feed forward control was very useful".

By this, are you referring to when you adjust the gas burner for an impending change in pump speed? I have not incorporated this sort of thing at present - something for the future if I ever get my system to function well enough in the first place.

"Have you seen my article in “Engineering in Miniature” magazine (Feb/ March 2012), which gives an overview of the monotube boiler control system?"

Yes I bought these issues as soon as they appeared - very interesting indeed.

"Sorry I’ve not responded earlier, but, as you may see on the “Edwardian Steam Launch build” thread, that I’ve been a bit busy."

Yes, I've seen that - and I'm very impressed with that hull. My gas valve and feed pump are rather bulky and may need redesign before putting into a boat. My main concern at present is to get the boiler control working. I was not sure what pump cylinder diameter to use and was afraid that too large a diameter would overload the motor. So I've made it with 1/4" diam. rams but the pump is designed so it should be relatively simple to replace the cylinders and rams for a different diameter if needed whilst retaining all the valve blocks, cylinder supports, crank etc.

Regards,  Mike

Title: Re: Flash steam plant control.
Post by: TurboTyne on October 05, 2012, 06:09:51 PM
Hi Ian

Can I please ask your advice on an aspect of wiring my control system?
I am about to make up some cable bundles with 9-way D-type connectors and also box up the boards. However, I'm worried I may run into problems with interference on the I2C bus from the high frequency switching of a couple of amps in the pump motor supply.
Power is supplied by two 6V rechargeable batteries which are connected as follows:.
The 12V from both batteries in series is sent to the feed-pump via a MOSFET that chops the signal to give the PWM control.
The same 12V also goes to a voltage regulator to supply 5V to just the electronic circuits.
(Also, 6V from one of the batteries goes to the 4 transistors which power the gas valve stepper motor). 

It would be convenient to run the power wires and the I2C bus wires in the same bundle. Do you think it likely that the serial bus would pick up electromagnetic interference from the 12V power wires over the lengths of wires typical in a model (i.e. up to a couple of feet).
Also, however,  the 5V regulated and the 12 V unregulated circuits share a common negative and I am wondering if there would be no sense in bundling the 5V and 12V wires separately anyway since the pulsed high current will still flow through the common negative and maybe could influence the 5V supply in some other way. So far things seem to be OK but ????
Do you have any experience of interference and do you think it is something I should be worrying about? Should I use a separate battery for the 5v regulated supply or am I worrying over nothing?
Thanks for any advice. 
Regards  Mike
Title: Re: Flash steam plant control.
Post by: flashtwo on October 05, 2012, 07:50:56 PM
Hi Mike,

The SPI is the “Serial Peripheral Interface” which doesn’t use a data / address bus like the I2C. It has separate data in and out pins and four slave address pins. I found SPI easier to understand and implement from scratch than I2C.

I did build a specific experimental board populated with  several PICs and LED bar indicators just to test the code – I also employed a PICO PC ‘scope in order to examine the actual waveforms being generated on the various pins, which helped enormously in detecting whether it was the Slave or Master controller that was not performing to spec. I know what you mean when the PICs start talking to each other.

I think with the SPI, you have much better control of the timing of events especially in the “real time” environment of control, i.e. you don’t have to wait for the bus to be free and you are not mixing data and addresses. Saying that, I2C can address many more PICs than SPI. You can search on Google for all the different pros and cons regarding SPI v. I2C.

Regarding Interrupts – my Master Control PIC has lots of conflicting jobs to do – it receives the feed demand PWM input pulse from the radio receiver (an interrupt), the internal Timer roll-over for servo and ESC PWM outputs (an interrupt) and  Serial Data buffer full (an interrupt).

Feed forward – yes, as you say its for adjusting the gas valve in anticipation of a steam temperature change due to a change in feed water flow.

Thanks for your “feedback” on the magazine article – I’m glad that it is of some use and will hopefully save you and other experimentalists some time.

Regarding the pump sizing – I’ve basically stayed with the ¼ inch by 1 inch stroke and just tried different sized motors and gear boxes. On my experimental steam jet boat I had a 915 (?) motor with a 29:1 gearbox. On “Vital Byte” I now run both pumps at once for high speed.

I shall have to take a break for now, but I shall read with relish the rest of your post later.

All the best

Ian.
Title: Re: Flash steam plant control.
Post by: flashtwo on October 06, 2012, 04:52:57 PM
Hi Mike,

The block diagram is a very good overview of your system – I must do one for mine someday.

I see that you have gone down the “distributed control” route with individual PICs, whereas with mine the slave PICs just supply the data and the main controller does all the work. The problem with my setup was that I was pushing the Master PIC to its limit regarding available registers, time and page space. This is the good thing about people like yourself, by not slavishly following my solution better ideas are produced – still, I have the option of changing the code and using (stealing?) your idea.

I did produce a dedicated pump controller for Steamboat Phil (see 17/2/2011 on this thread), since he just wanted to set a certain feed flow for his flash steam straight runners.

The second thermocouple is very useful for measuring other temperatures, e.g. boiler exhaust, ambient, feed inlet and so on.

I see that you are measuring the ambient and then doing the cold junction compensation in software – you might find the thermocouple amp AD595 of  interest, since it does the linearisation and compensation all in one package.

I remember that your gas valve servo has limit switches to prevent “integral wind-up”, but how do you handle it with the feed pump speed PID. 

Which LCD display are you using (the bigger the better for my eyes!)

Regarding interference –

I would keep any components that take a high current on a separate “power bus” fed from the battery directly (via a fuse!) and ensure that no high currents are taken from the supply at the PIC board. I had a problem high torque servos (even those controlling the rudder and engine reversing linkage) dragging the volts down momentarily. I ensured all servos (though not the ESCs) were powered from their own bus with only the white signal wire coming from the PICs.

Ensure that electric motors have their own earth (-ve) connection back to the battery and that all other negatives go back to a common terminal and then to the battery using thick wire in both cases. This is to eliminate high return currents lifting the volts above zero.

For those interference spikes that don’t even show up on the ‘scope, put 1500pF capacitors  between the +5v and 0v at a couple of locations on the board.

Once I had a motor whose insulation was a bit suspect and this caused spikes on the earthing system  - I changed the motor.

I do use screened signal wire on the long runs to the servos and pressure sensors – which reminds me, are you using the type K (green/white) cable for you thermocouple connections.

And, finally ensure that unused pins on the PICs are set as outputs and/or tied to 0volts, otherwise some of them have a nasty habit of causing rests or interrupts.

I have had a board failure caused by the Sun’s heat shining through the clear cover of the controller box – I had been chatting for an hour at the lakeside, but it is a reminder to ensure to keep things cool.

I have the same battery and regulator setup as you – make sure the regulator stays cool once it is mounted inside the boat though.

I hope this is helpful – I’m sure I will think of some thing else to add.

Good “bug” hunting as they say.

Ian.
Title: Re: Flash steam plant control.
Post by: TurboTyne on October 07, 2012, 09:01:35 AM
Hi Ian

Thanks very much for your replies and especially for the advice about avoiding interference. I shall incorporate all those points in my design.


"I see that you have gone down the “distributed control” route with individual PICs, ...."

I like the sound of calling my set up a “distributed control” system. I had not fully realised it was so different to Vital Byte. Your blog describing the use of a serial bus led me to read up about this concept and that led to I2C. In reality, I did not set out by designing the whole system – it just seemed to evolve in that direction after I had initially constructed the PIC board for controlling the gas valve. Also, I think the way I ended up controlling the gas valve may be placing more demands upon the PIC, so cramming all into one device would have been particularly difficult.

"I see that you are measuring the ambient and then doing the cold junction compensation in software – you might find the thermocouple amp AD595 of  interest, since it does the linearisation and compensation all in one package."

Following your earlier posts, I was going to use this device and it would probably have saved me a lot of time. As with all aspects of this project, after reading your notes on Vital Byte, I downloaded relevant Microchip application notes and went from there. Doing things my long-winded way did mean I learn more about what is going on.


"I remember that your gas valve servo has limit switches to prevent “integral wind-up”, but how do you handle it with the feed pump speed PID."

I am probably misunderstanding your question here, so I apologise that the following “essay” is so long.
If the term “servo” always means  a specific type of device that converts a PWM input to a motor-driven positional output, then I am not using servos. (I’m not being deliberately pedantic here, it’s just that I am ignorant of how these terms are commonly used).
 
In my gas valve mechanism a stepper motor turns a threaded rod and this moves a sliding block along its guides. The sliding block is connected by a lever to the end of a rod which is thus moved in the same direction as the threaded block but to a smaller extent. The end of this rod enters the body of the gas valve through an O-ring seal. The very end of the rod is tapered and forms the needle of the needle valve. It enters a hole inside the valve body through which the gas has to pass. Thus the needle is pushed or pulled in/out of the hole unlike a normal valve where the shaft of the needle is threaded and is moved by rotating it.  Unlike a servo-controlled valve, the system has no way of knowing the position of the mechanism so the sensors at each end of travel of the screwed block are essential to stop the motor turning too far so the block jams up on the end of the threaded rod.  The valve can be fully closed or opened by sending a coded message to the PIC which then turns the stepper motor until the end of travel is reached. The result of PID analysis is sent as the number of steps to open / close the valve. Because of the fine thread and the effect of the lever, it takes several hundred steps to fully open the valve.

With the pump motor, there is no separate ESC unit. The pulse width modulated power output is generated by the PIC device itself using one of its CCP modules which is based on the system clock (4 MHz). The CCP PWM output is set to a frequency of 10 KHz. (i.e. each cycle lasts 100 usecs). This means that the ON time of a single PWM cycle can vary from 0 up to 100 usecs in 400 steps of 0.25 usecs. This seemed to me to be a good enough resolution. I would be interested to know if this is how other people and Vital Byte controls electric motors.
I think I read that for the VitalByte feed-pumps, you send a PWM output to an ESC (??).  If so, do you use a commercial ESC?

The result of the PID analysis of motor speed increases or decreases the ON time of the PWM output  but the software limits this to values between zero (stop) and 400 (max speed).

One complicating factor was that,  with the PIC running at 4 MHz, I found that the timers run too fast to allow measurement of the time of rotation of the pump. So the time between successive pulses from the Hall effect sensor are measured using TMR2 running under an external 32.768 KHz crystal.   Did you find the same thing or do you accomplish the pump speed measurement in a different way?


"Which LCD display are you using (the bigger the better for my eyes!)"

My eyes seem to demand the use of "reading" glasses for more and more tasks these days. My LCD display has characters 5 mm high and has 4 rows x 16 characters. This was one of the cheaper models at Farnell (£9.34 each) and works fine, except I wish I had gone for a display with more characters per line. I may add another PIC (with a different I2C address) connected to a second display so I can send different data to each display. I think this may prove more versatile (and cheaper) than buying one big new LCD.

This is the device I use:        http://uk.farnell.com/jsp/search/productdetail.jsp?sku=2063248&CMP=i-bf9f-00001000

But I'll not be adding another LCD until I've made more progress as there is a VERY long way for me to go before I have anything near a functioning system.

Regards  Mike

Title: Re: Flash steam plant control.
Post by: Panoramix on October 10, 2012, 04:27:00 PM
Thanks Panoramix for the diagram - "Vital Byte" still appears to be somewhat short of achieving "hull speed", although its square hull section may be offering a lot of resistance.


I am just reading your answer now and I am glad that the info was useful to you. And yes a square hull is not ideal to reach hull speed.
Title: Re: Flash steam plant control.
Post by: flashtwo on October 18, 2012, 06:15:15 PM
Hi Mike,

The “integral wind-up” that I describe, is the situation when the controlling device (i.e. a valve) can’t eliminate the error and the Integral Action output of the controller keeps ramping , since its rate is governed by the error.

The controller may have some internal limit like the supply rail voltage for an analogue controller (+/- 15volts) or a numerical limit in a digital controller, say the two-byte limits of zero and 65535 (which may roll-over to zero!). When the error changes polarity, the integral output will start ramping in the opposite direction, but, if it has previously reached an out of range value, it may take a long time to return to the actuator control range. This integral wind-up lag will make control impossible.

In my case, the PWM servo and ESC operate over the range 1000 to 2000us (1 to 2ms), therefore the controller output is limited zero to 1000 (the 1000 PWM offset is added on ). When the controller output reaches the zero or 1000 limit, the Integral Action  calculation is by-passed and the integrated error value is “frozen” at the limit so that, when the error changes polarity, the integrated value comes immediately back into the control range. This is all done internally without resorting to external limits. For the gas valve I can dynamically adjust, at the Display Unit,  the 2000us (nominal closed) limit anywhere between 1500 and 2300us and observe that the gas valve physically shuts the flame off.

For the pumps I am using a commercial ESC (Robbe) which can handle the standard PWM signal of 1 to 2ms. What will you do in your system, when for example the battery volts start to decline and the motor can’t maintain the desired pumping rate and the error is not eliminated? Will the PID still keep integrating the error, although there is no hope that the feed will get to the desired flow?

That’s funny, I had exactly the same problem as you in measuring the RPMs. From the control board’s common 4MHz clock pulse, one small PIC derives two separate timing pulses (2000us & 200us) for the PICs measuring the RPMs of the pump (0-200RPM)  and engine (0-800RPM) respectively.

I divide my display data into a number of chapters and pages. The chapters represent a particular control function i.e. temperature, feed etc. and the pages represent measured and desired values, PI settings etc appropriate to that chapter. On my display console, each chapter has its own push button and then I can scroll down the pages in the chapter using the up/down buttons. You can therefore navigate around a lot of data using only one LCD.

I hope my explanations are understandable. I think if you refer to the magazine article you may get a better idea with my analogy of controlling the water level in a pond.

All the best

Ian.
Title: Re: Flash steam plant control.
Post by: flashtwo on October 18, 2012, 06:20:18 PM
Good job I kept a copy of the above long reply, seeing as it went missing off of Mayhem when I posted it last week!

Ian.
Title: Re: Flash steam plant control.
Post by: TurboTyne on October 19, 2012, 08:09:52 AM
Hi Ian

Thanks for the explanations. This reply is delayed because I first wanted to re-read your article. It is a long time since I initially read it and I clearly forgot a few things. It is interesting that now I have made more progress on my own system, I am better grasping the significance of more details mentioned in the article.  Also, I’ve had a bad week in regard to problems encountered upon returning to the electronic controls for my pump after a few months spent designing and building the mechanics.

Regarding the topic of integral wind-up, this is dealt with in different ways in my valve and pump control situations. The pump control is PWM and, as in your system, I limit the range of values permitted for the relevant control variable. (Presently 0 to 400). For the gas valve, the integral wind-up effect is mechanical rather than electronic since continued creeping of the stepper motor moves the valve. In this case movement is limited by the optical positional sensors. These are very accurate and their position can be easily adjusted. So I hope that adjusting their positions will enable the needle in the valve to be stopped from moving beyond its useful range. My PID sub-routine is based on a Microchip application note (AN964 Software PID Control of an Inverted Pendulum Using the PIC16F684). 

With regard to your point about how to cope with a failing battery, I must confess that I had not thought that far ahead. As just mentioned, the present software/hardware arrangements will hopefully stop integral wind-up but I guess it would be useful for a boat to signal to the operator that the battery is getting low so it can be brought to the bank asap. Might it be useful to use a spare A to D channel on a PIC to monitor battery voltage? If V drops below a certain level then the pump rate could be reduced to a modest speed. I can't remember if you have already discussed this in this extensive blog.

I like your semaphore system to communicate from boat to operator. Did you ever consider using 2-way radio? I have never dabbled with radio control so I have no idea if this is even feasible.

Some of the problems I have just been battling with were caused by errors or omissions in my notes. But one significant issue has cropped up.  I am now concerned that the PIC-generated 10 KHz PWM output will not have adequate resolution. It has a pulse width varying over a range of 0 to 400 and I had assumed that I would be able to control the motor speed over at least the range 150 to 400 since the motor runs fine down to below 3.3 V when using a standard DC power supply. I had assumed that a PW of 200/400 (i.e. 50% PW) would be equivalent to running the 12V motor at 6V  (i.e. 50% voltage). However,  it seems that 50% PW is much less powerful than 50% voltage.  I hope this is a recognised phenomenon and not something I’m doing wrongly. I wonder if it might be linked to induction effects in the motor windings. Whatever the explanation, it seems I shall only have effective control over a smaller range of  values. Before abandoning my present  approach and buying a commercial ESC I am going to try increasing the number of PW steps from 400 to 1600 by increasing the PIC Fosc frequency from 4MHz to 16 MHz.

One further question, if I may. Do you get a lot of noise from the motor-gearboxes on the pumps? I would guess that a boat containing my pump motor would be much noisier than expected for a steam boat.

Regards

Mike


Title: Re: Flash steam plant control.
Post by: flashtwo on November 03, 2012, 01:57:57 PM
Hi Mike,

Sorry again for the delay – I’ve been making lots of dust on the launch build!

Right –

I’m using the motors with epicyclic 100:1 gear boxes from MFA/COMO and I don’t find them unusually noisy and besides, as the boat pulls away from the shore, the engine and motor noises die away quite quickly.

Regarding the semaphore – several people have suggested that I should transmit the boiler pressure, temperature etc. back to the shore, but my intention was to make the boat’s plant control fairly autonomous with me outside the loop apart from boat speed and direction. I see that these data links are discussed on one of the other threads and that the model aircraft guys use them a lot.

Once the boat is off, I use the semaphore just as a fuel gauge (gas cylinder pressure) to know if  I need to return to shore. Sometimes it is set to indicate steam pressure, as when I set the reversing linkage to neutral, build up some pressure, then set to ahead and accelerate the boat just to show off!

I also considered making my own ESC, but found difficulty in sourcing the “H”-bridge chips at a reasonable price and besides it needed the additional voltage rails to effectively switch off the MOSFETs completely – if my memory serves me correctly. I thought that I couldn’t better the commercially available ESCs and that my time would better be spent developing the boiler controls that aren’t available commercially. By all means carry on with the ESC design – it will be an interesting part of the project and satisfying when you get it working and you will become the expert and advise other people.

I’m intrigued with your stepper motor control PID analysis – do you track the gas valve position by keeping a tally of the number of +/- pulses sent, e.g. say it takes 2000 pulses for 100% travel, do your limit switches reset the pulse count to zero when the valve is closed and to 2000, say, for when the valve is fully open?

In the distant past, I had problems with an industrial steam temperature control system that used stepper motor controlled valves. The valves had positional feedback potentiometers to the control system, but separate limit switches for the anti-windup. It was that long ago that I built a simulator on the old BBC Micro computer and even plotted the valve position on the screen. I emulated all the analogue control modules in the real system, but the simulator kept showing the control valves would bounce off their limits in ever reducing amounts. In frustration I went to the plant control desk and had a chat with the operator who clearly demonstrated the same problem had existed in real life for years, but had never reported it. The original control system design was wrong in that the limit switches were “shorting out” the error, which the control system interpreted as a change in direction and therefore opened the control valve instead of closing it, thus causing the on-going bad steam temperature control.



It was that experience (plus a instrument mechanic who had got suicidal rewiring the control loops to my latest “solution”) that encouraged me to start using PLCs for control.

All the best

Ian
Title: Re: Flash steam plant control.
Post by: SteamboatPhil on November 03, 2012, 11:06:58 PM
I would just like to add my little bit, that thanks to Ian (who's data I have benn stealing.....well actullay he gave me a few bits electronic wise that is) my radio controlled flash steam boat has moved ahead in leaps and bounds (remember I am a straight running steam type person) with luck my demo plant will be at Ally Pally in the new year.. :-))
Title: Re: Flash steam plant control.
Post by: TurboTyne on November 05, 2012, 05:14:23 PM
Hi Ian

Thanks for the replies. My motor has the cheaper spur-gears – rather than epicyclic. So now I’m wondering if the spurs are noisier. If I get a system working then I can think about upgrading.

Hearing your reasoning behind your decision to buy the ESCs makes me think I am the “fool rushing in where wise men fear to tread”. No doubt a commercial ESC will contain sophistications of which I am not even aware but I thought that if I could get the PIC to work as the heart of an ESC then it would comprise an intelligent unit directly controlled via I2C. I have not needed anything complicated like an H-bridge because it is a DC motor with no reverse - so a simple MOSFET transistor does the trick.  I have just increased the clock speed on this PIC to 16 MHz so the pulse width over which power is sent to the motor (via MOSFET driver/MOSFET) can be varied from 0 to 1023 x 0.06 usec steps, with a pulse repetition frequency of ca 16 KHz. So that seems to match the dynamic range of 1,000 x 1 usec steps you send to your ESC.

This PIC ESC seems to work fine  BUT  I find that when the speed of the 100 rpm motor drops much below  22 rpm (pulse width = 750/1023) it stalls. I don’t know if this is as to be expected for this type of motor and I would be very interested to hear if your pump can operate at speeds much less than 22 rpm using the Robbe ESC. If so, then I guess the Robbe unit is doing something special that my method is lacking.

Regarding control of the gas valve stepper motor, my approach is nowhere near as sophisticated as you seem to be thinking. Your tale about experience with the steam temperature control valves makes me wonder if I am over-looking something crucial in my system. If you spot any problems with the following plan, I’d greatly appreciate it if you would let me know.   As I understand it, the problem with tracking the position purely by counting pulses (i.e. no position sensor) is that it requires the system to calibrate itself on power up by moving to a known start position. Also, I think that any error or missed steps would accumulate over time so a periodic recalibration would be advisable. My current (but as yet untested) plan for the gas valve control is as follows.   The PID analysis generates a number (+ve or -ve) that indicates the number of steps the valve motor should move. The system does not need to know where the valve is but just if it should open or close the valve at all and, if so, by how much. If the set temperature cannot be achieved then the worst case is that the valve opens fully. It would then activate the full-open sensor. This tells the PIC not to turn the motor any further in that direction and it could also be used to trigger other responses to the situation - but I’ve not planned that far ahead.  If it is required to fully close or fully open the valve, then a suitable command tells the PIC to turn the motor in the appropriate direction until the appropriate sensor is activated to stop further movement.

I don’t understand why the steam valve you mentioned needed potentiometer position sensors?  It sounds as if the system needed to set the valves to specific positions rather than just open or close the valve a bit more. The bit more / bit less approach is also the way my pump speed control works – but in that case it is the pulse width value that is adjusted up or down according to the PID analysis result. This is basically as described for the PID-based control system in Microchip AN964.

So were you able to correct the valve control system that you so carefully analysed on the BBC?  I too have fond memories of programming a BBC computer at work.  Back then the BBC was one of the best small computers available for laboratories to use. Now, of course, a PIC costing just a few pence is equally powerful as a BBC.

I’d never heard of a “PLC” until you mentioned it in your last message. So I looked it up and discovered yet another whole new field of technology that I’d been unaware of. (It was through your blog that I first learnt of microcontrollers!!).

Best regards
Mike
 
Title: Re: Flash steam plant control.
Post by: flashtwo on November 19, 2012, 08:02:46 PM
Hi Mike,
 
You’re quite right about not using an H-bridge – I was making it too complicated for the application of a single direction motor.
 
I can measure down to 0.5RPM, although for an immediate response to a control change, the pump’s minimum strokes per minute (SPM) is set at 14, which through the 100:1 gearbox gives a motor minimum of 1400RPM. I can run at a slower SPM, but with a greater chance of stalling then overspeeding as the error suddenly builds up and results in instability. Unlike a conventional boiler, where the pump is operating against the established boiler pressure, the monotube boiler that is at minimum feed flow is also at minimum pressure and so the pump is less likely to stall.
 
Does your Proportional part of the PID analysis generate a fixed number of pulses such that, for example,  a 10% error will cause a total 100 pulses to be sent and a 20% error will send 200 pulses such that the actuator will only move a fixed (though proportional) amount and then stop? And does the Integral analysis result in a continuous run of pulses the frequency (or rate) of which  depending on the size of the error? If so, the integrating “memory” of the system is within the actuator and so stopping the pulses will stop any integrating wind-up (you’ll have to excuse me here – I’m dragging the depths of MY memory). With my system the integrating memory is within the software and so required to be “informed” when the actuator reaches it limits otherwise the integrating “memory” increases in value.
 
I think I myself could do with some integrating memory!
 
The steam valve (actually desuperheater spray water valves) used the potentiometer to feedback the valve position to the central control room for manual control. Originally, the auto control system didn’t use the positional feedback, since it relied on the limit switches. Since there were 16 valves and 64 limit switches to be accurately maintained, the system was unreliable and so I redesigned the system to just use the potentiometers as feedback and even then didn’t have to rely on 100% accuracy. Yes, the system did work and was still working 10 years (running 15 years non-stop) after I took early retirement. It has only recently been replaced after the installation of a completely “soft” control room, but even then it has been emulated in the replacement system.
 
I have one complaint – I’m having to think back a long way and its making my brain hurt!
Ian
Title: Re: Flash steam plant control.
Post by: TurboTyne on November 23, 2012, 10:43:22 PM
Hi Ian

Thanks very much for the info on the performance of your speed controller / motor. From this it seems clear that the Robbe unit is definitely doing something better than my homemade effort – which, of course,  is not surprising. Actually, I have recently made a modification to the circuit and my unit now does better than before. I can now run the pump, pumping water into a boiler at 50psi, down to 15 rpm. When pumping against no pressure it will go down to about 13 rpm before it stalls. (Before the modification the motor stalled below 22 rpm, even with no pump connected).   The control between 15 and 100 rpm is excellent so I am happy with this outcome for the time being and I'm hopeful that it will enable me to proceed with getting a working system. However, I've become a little hooked on this ESC topic now and I am curious to see if I can improve it further. I had read that a moderately high pulse repetition frequency (around 20 KHz) generally gives the best control so I have been using 15 KHz. However, I have just seen that one type of commercial model boat speed control controller  (Electronize Type FR30 HX) uses a variable pulse rate (from 2000 down to 10 Hz !!) and the description says that low pulse rate gives better results at low speeds. With a PIC-based ESC it will be very easy to investigate this directly by changing the pulse rate with all other things kept the same. Also I'm looking forward to investigating the waveforms in the circuit using a cheap oscilloscope that I've just obtained. I am wondering about writing a summary of all this and posting it in a new thread -  although I doubt it will be of interest to many others (if any at all).

Out of curiosity, do you have any idea if there are many people who are into using PIC devices in model boats etc or are microcontroller hobbyists mainly robot builders ?

Yes, your summary of how my system works (or is hoped to work) is correct. The PID software calculates a proportional term, an integral term and a differential term (currently set to zero). These are added together. Then, depending on whether the resulting number is  positive or negative, the valve motor is told to open or close the valve. If the number is negative, it is converted to a positive number. Then the original or the converted positive number is sent to the valve control PIC which moves the motor by that number of steps – or until the limit of movement is reached. When the proportional part is zero, the integral will continue causing a movement. Providing the movement limit is set so as not to be beyond the point where further valve movement makes no difference to the gas flow rate, then there should be no wind-up.

Sorry the question about past activities made your brain hurt. Yes, I too would appreciate having an upgrade to my memory chips. 

Regards,  Mike
Title: Re: Flash steam plant control.
Post by: steamboatmodel on November 27, 2012, 06:42:45 PM
My Brain is hurting too, but it is a good hurt as it is causing me to think and remember things I once partially understood. Please continue there may not be many others posting on it but I think that others may be like me and letting it mull around in our heads trying to figure it out.
Regards,
Gerald.
Title: Re: Flash steam plant control.
Post by: TurboTyne on December 15, 2012, 07:46:08 AM
Thanks for the encouragement Gerald.

So as not to encroach further about this diversion on Ian's thread I've just started a new topic called "ESCs and pulse rates" in the section "DC motors (Brushed) and speed controllers".

Regards,  Mike
Title: Re: Flash steam plant control.
Post by: flashtwo on March 10, 2013, 04:34:22 PM
Hi,
 
I was doing some research for my Edwardian Steam Launch build, when I came upon this webpage http://www.machine-history.com/Herreshoff%20Manufacturing%20Company%201800s (http://www.machine-history.com/Herreshoff%20Manufacturing%20Company%201800s) about an 1880s American company that was manufacturing full size launches with monotube or "safety coil" boilers. It is interesting that the feed water entered at the boiler top and steam exited at the bottom, just like "Vital Byte"; nothing is new!
 
It has a separator to allow superheated steam production, which is what Gondolier88 (Greg) and I have been discussing in his recent "Gas burner jet" thread.
 
I wonder what happened to the Herreshoff design.
 
More experimentation coming up!
 
Ian.
 
 
Title: Re: Flash steam plant control.
Post by: flashtwo on March 10, 2013, 05:15:20 PM
Further research regarding the Herreshoff "safety coil" design.
 
1) It was expensive to manufacture due to the tapered boiler tube employed in its design.
2) Water treatment was primitive, such that all boilers of that era scaled up. Conventional straight tube boilers could be cleaned, but the coil boiler had to be expensively replaced; the early ones used sea water as bolier feed.
3) Ironically, Mr Herreshoff himself lost his steam engineers licence having screwed down a safety valve on a conventional boiler and causing the death of the operator (Mr H was attempting to increase the speed of a steam yacht).
 
Food for thought though.
 
Ian.
 
 
Title: Re: Flash steam plant control.
Post by: silverbrewer on October 11, 2013, 04:39:40 PM
This is a test to see if this post is going to be credited to me (silverbrewer) or to Xtian29.
The previous posts of mine on this subject have had the headings changed to Xtain 29 since page 9.


I am looking at all of this, but it is getting a bit beyond my comprehension limits!!!
Title: Re: Flash steam plant control.
Post by: Tug-Kenny on October 11, 2013, 05:11:41 PM

Not to worry.  A lot of folks posts were credited to different people as the system crashed.

We'll see what we can do.

Ken


Title: Re: Flash steam plant control.
Post by: Martin [Admin] on October 12, 2013, 04:22:47 PM
Just had a look, can't really retrospectively change the post without screwing up all of Xtian29 posts, it's an 'all or nothing thing'...
Title: Re: Flash steam plant control.
Post by: silverbrewer on October 12, 2013, 04:57:44 PM
Thanks for checking it out, but it is no biggie! As long as xtan is not confused. I only had about 20 posts on here, so going back to newbie status is of no concern.
Title: Re: Flash steam plant control.
Post by: silverbrewer on February 16, 2015, 08:59:58 PM
How are things progressing? There seems to be a lull in posts. Let's hope no news is good news.
Are you thinking of selling these systems in any sort of format?
Could you come up with some sort of thrust figure for your boat next time you have it at full tilt?
Title: Re: Flash steam plant control.
Post by: flashtwo on February 17, 2015, 08:14:01 AM
Hi Silverbrewer,

No things didn't stop. The monotube boiler system was developed to a point where it could be transferred from the experimental boat into a "proper" model launch. The actual software until recently (see the XBee thread below) hasn't been changed for a couple of years.

Look at the Edwardian Steam Launch build thread http://www.modelboatmayhem.co.uk/forum/index.php/topic,37563.25.html
and videos
https://www.youtube.com/watch?v=2HV4s9MjfaQ
and
https://www.youtube.com/watch?v=Az_U-Qeb3fY

I will be doing some superheater experiments when the weather warms up, but in the meantime (during the cold weather),  I've been developing the electronics for the launch, see XBee thread

http://www.modelboatmayhem.co.uk/forum/index.php/topic,48575.25.html

and I've also started on a voice command system for the launch, see

http://www.modelboatmayhem.co.uk/forum/index.php/topic,50087.0.html

I'm afraid that, apart from Mayhem member Turbo-Tyne and a couple of others, the field of interest in steam AND computer control is quite narrow. For most steam buffs the traditional boiler satisfies their interest and the learning curve of computer control is too steep. The completed control system could certainly be used by others without too much training - it just requires an overall understanding of what its trying to achieve without delving into how the software works. I could produce another system since it is all documented.

Weren't you building a steam powered kayak using a Stuart D10 engine - how have you progressed?

Thanks for your continued interest.

Ian
Title: Re: Flash steam plant control.
Post by: Jerry C on February 17, 2015, 10:39:54 AM
Hi, I've been watching all your posts with an interest in both flash steam/mono tube boilers AND the computer control side. From the Master FG certificate syllabus I understand(but may have forgotten a bit due to lack of use) about aspects of control of systems (proportional/integral et al) as it applies to pneumatic control systems. All totally theoretical though.
Computers now, with a view to actual programming and code is a complete mistery  to me.
I have a certain amount of Aspergers Syndrome in that if I determine a need for a certain knowledge I am able to learn it quickly and easily and (up til now), retain it for ever. Without an interest/need I block it out completely. It's hard to describe.
My education, (I'm 65), did not envisage computer use to my future, so there are NO foundations to build on or prior knowledge to call on so although I have read, and attempted to study and understand, it has I'm sorry to say appeared as fluent bollox to me. (Nothing personal the problem is all mine).
The need is now there but I can't do this myself. Also, the "standard" educator won't hack it with me. I need a special kind. I had two of these at school. One guided me to O level physics in one term and the other to Additional maths in the same time at 14.
So I will continue to follow your threads and when the time comes maybe I'll manage to get enough out of it to control my own steam plant.
Keep posting and thanks.
Jerry.
Title: Re: Flash steam plant control.
Post by: flashtwo on March 29, 2015, 03:13:38 PM
Hi Mayhemers,

With the boating season starting, I’m going to carryout some experiments (again!) on the Flash Boiler system.

This winter I’ve been building a Superheater boiler to run in tandem with the existing Saturated Steam boiler.

A problem with the single boiler is that it can go unstable when attempting to run with anything more than a few degrees of superheat. The transistion point of water turning into steam, somewhere along the length of the monotube, can suddenly move towards the cold end of the boiler, thus, exposing a lot of area to the burner flame.
 
This extra heating area gives too much superheat and the system control automatically shuts off the gas to lower the temperature.

By using a tandem boiler with its own dedicated burner, the transition point can‘t go beyond the inlet to the boiler, thus limiting the exposed heating area (that's the theory anyway!).

The Superheater boiler has about 10% of the heating area of the Saturated Steam boiler, since once the latent heat of evaporation has been supplied, it takes little heat to raise the steam temperature.

The photograph show the design is a small version of the main boiler.

Ian
Title: Re: Flash steam plant control.
Post by: TurboTyne on March 29, 2015, 08:26:30 PM
Hi Ian

That idea for a superheat boiler is very interesting.  So is that similar to the situation in full-sized boilers where they have a control of the superheat by changing the direction of the furnace gases to control whether or not they pass over the superheater tubes? I gather they also have systems to spray water in to the steam to reduce temperature but from what you've mentioned in past posts I think you might have direct experience of these types of controls??

How do you plan to control this burner compared to the main buner? Will it respond to steam temperature and the main one to steam pressure? I have a down-loaded text book on boiler control systems for power stations. It says pressure control gives a much faster response and is usually the main control, with temperature as a secondary input. I recall you found temperature control worked best for Vital Byte but with my boiler I certainly find the response to temperature is very slow. I have a pressure sensor I want to try it at some point - after finishing what I'm doing and setting up those Xbees.

Regards

Mike
Title: Re: Flash steam plant control.
Post by: flashtwo on March 30, 2015, 01:43:25 PM
Hi Mike,

Well, so far, I've drilled and tapped the engine steam inlet manifold and fitted an additional thermocouple. The control system has always had a spare thermocouple input for experimental purposes, so I'll be able to look at the superheated steam temperature with the new telemetry (thanks to you) system.

The first boiler's burner should be controlled on pressure, as you say, because this is directly related to the saturated steam temperature. Likewise, using the existing boilers outlet temperature should give an equivalent signal for pressure and, because of thermal lag, a less "noisy" signal. So, if I want a higher pressure I should increase the saturation temperature demand setting. At the moment the saturated demand is a function of the feed water flow - more water -higher temperature demand  - higher pressure.

The second burner should control the superheater temperature. Initially I'm going to use just manual control for the superheater burner.

This idea of a separate superheater boiler is from a system that the U.S. Navy had on warships in the Second World War. The forward and reverse turbines required different steam conditions, such that the reverse turbine couldn't handle the superheated conditions used normally for forward propulsion.

When manoeuvring in harbour, they couldn't afford the time to reduce steam temperature in the normal way of knocking out the oil burners and altering the furnace gas flow/ sprays.

By using a separate superheater burner they could quickly change the steam temperature for forward/reverse and still maintain control.

Although the U.S. Navy system wasn't a monotube boiler and had a boiler drum, I thought it would worth experimenting with on the steam launch's monotube system.

It is good to be back with the metal bashing after spending most of the winter tinkering with the software for the telemetry and Voice Command systems for the launch (all due to your question about XBEEs!).

Ian
Title: Re: Flash steam plant control.
Post by: flashtwo on March 30, 2015, 06:28:06 PM
That was ironic - connected up the spare thermocouple to the AE-35 controller and found I had a constant 195degC reading.

Traced the problem to a bad ground connection on the thermocouple amplifier - all that bouncing around taking the launch to the Ally Pally exhibition in January caused the bad joint (that's my excuse anyway!)

At least it wasn't the telemetry system!

All ok now.

Ian

Title: Re: Flash steam plant control.
Post by: TurboTyne on March 30, 2015, 08:26:58 PM
Was that one of those problems that takes ages to trace or did you track it down quickly?

Actually I wanted to ask about the US navy and reverse turbines. Do you know in which ships that method with the superheat burners was used? Was it in ships using very high steam temperatures (e.g. above 750 degC)? I have read that in British ships using such high temperature steam special precautions were necessary when using the reverse turbines but I have not seen what these precautions were.

Thanks  Mike
Title: Re: Flash steam plant control.
Post by: flashtwo on March 30, 2015, 10:15:21 PM
Hi Mike,

I was lucky that there were two identical thermocouple amps  (AD595) on the board, so I could compare working with not working.

I tried shorting the input to the amps, but the suspect one stayed at 1.9 volts output. I changed the IC with a spare - no improvement. Checked the supply at the IC pins and the 5 volts was spot on, but the ground was at +1 volt. Checked the ground "daisy-chain" wiring and found a bad connection between the good IC and the suspect one. It was best to put a new ground wire in rather than re-solder the existing one.

With the new ground wire, the ground volts at the suspect IC was practically zero and the system now gave the correct temperature. It was the first fault in the controller in the five years since it was built - I hope its not a forerunner of future problems.

The U.S. Navy Fletcher Class ( http://en.wikipedia.org/wiki/Fletcher-class_destroyer ) used separate superheater boilers, which are exhaustively described here .... http://archive.hnsa.org/doc/destroyer/steam/sec06.htm.

If you look on page 58, Section (c) there it is described when not to use the superheat boiler, plus all the bell signals from engineering to the boiler room - it makes you appreciate the automation that we have now.

I hate to think of these poor boiler operators having to respond to the directives from engineering and remembering, under battle conditions, which valve and sequence to operate - any mistake and you could wreak the superheaters and be a sitting duck to any passing Jap sub or Kamikazi - I suppose that was the "job" incentive scheme!

The only precaution regarding high temperature steam, that I can think of, is that of maintaining steam flow through all the superheater tubes to prevent them failing under high temperature. The other problem is with the turbines - too high a temperature and rapid temperature change, you risk expansion and blade rubbing - too low a temperature and you risk water carryover and blade damage.

I've never had experience of reversing turbines apart from seeing the "tiny" one on HMS Achilles many years ago. You could see it only had a couple of stages from its length.


All the best

Ian






Title: Re: Flash steam plant control.
Post by: TurboTyne on March 31, 2015, 06:58:56 AM
Hi Ian

That sounds like a very efficient piece of detective work.

Thanks very much for the links, especially to the HNSA-destroyer site.  I did not know about that and I think I'll be spending quite some time looking through the huge amount of info available there.  I had a look at the Fletcher boiler and engine pages and see what you mean about the engineers and stokers needing to keep their wits very much about them to avoid ruining the plant. Presumably the thought of all that super-heated steam that might escape and cause them serious harm must have been another incentive to keep their minds focused - even without the enemy.

I hope you'll be posting updates about how your dual boiler system works.

Regards
Mike
Title: Re: Flash steam plant control.
Post by: flashtwo on April 04, 2015, 01:02:35 PM
Hi Mike,

Just been rummaging through an old box of memorabilia and found a blade tip cut from a 500MW turbine at Kingsnorth Power Station in 1974.

The blade, from the very last stage of the Low Pressure Turbine, was removed because of vibration problems that lead to blade shedding and considerable damage to the condenser tubes. Normally, the blade tips are constrained by the use of traditional stout wire bands, but these were replaced with properly engineered arch bands, which attached each blade to its neighbour.

The blade tips are of Stellite and show what damage water droplets can do when the tip is travelling at 1200MPH.

The new superheater boiler has been installed in the launch, though I've still have to complete the gas pipework. The boiler can be easily removed and the launch run with just the saturated boiler. The old adage is that you can never achieve superheat in the presence of water.

I've found an interesting web page discussing superheated and saturated steam ( http://www.systhermique.com/steam-condensate/services/troubleshooting/superheated-steam/ ). Obviously, with a piston engine you still need a bit of superheat to stop condensation in the pipework and engine when the steam expands.

With just saturated steam, as you can see from the article, the heat conduction is very high compared with superheated steam.

As soon as condensation takes place in the engine cylinder the pressure just falls away, so, delaying the condensation maintains the steam pressure to the end of the power stroke.

Tomorrow and Monday, I'm displaying at the Chatham Historic dockyard, Festival of Steam and Transport.

Ian
Title: Re: Flash steam plant control.
Post by: TurboTyne on April 07, 2015, 07:39:06 AM
Hi Ian

Very interesting to see the photos of the damaged blade tip. Were the turbines at Kingsnorth made by Parsons?

Several years ago I was shown around the Parsons works by the then works manager - that was before they were taken over by Siemens and most of the huge factory buildings demolished. I remember he showed me some L.P. blades that had been eroded by water droplets and were to be repaired. I've been interested in steam turbines for quite a while. My electronically controlled monotube boiler is currently connected to a turbine that I built many years ago. This turbine is rubbish for power output but I hope the next one will be more efficient.  I plan to equip it with electronic speed measurement and overspeed protection. It is straightforward to plan all that now I have learnt a bit about microcontrollers - thanks to being inspired by your posts.

Your superheat boiler looks very neat.  How many degrees of superheat are you aiming for?

Regards   Mike
Title: Re: Flash steam plant control.
Post by: Stoneflash on May 18, 2015, 10:08:59 PM
Hello all. I’m new to this forum but have steam experience through my previous ownership of an Edwardian Stanley steam car. I’m looking at a smaller scale but no less interesting hobby and thinking about how I would go about it. The Stanley by the way ran at 600psi with a vertical fire tube boiler, a vaporising burner fuelled with 50/50 petrol/diesel and a vaporising pilot burner on petrol. The main burner put out 500,000 Btu/hour, burning 18 litres per hour! It would do 70mph if the driver were brave enough. The pilot was identical to the silent burning diffused flame burner proposed by ET Westbury and shown on p69 of Benson and Rayman "Experimental flash Steam".

This thread is really interesting to me as a monotube gets us away from the bugbear of boiler tests etc of which I have undergone enough - but one thing which hits me from the last few posts on superheat is how much superheat can the current crop of smallish steam engines cope with? Many of them appear to have bronze cylinders and pistons - the French Antón and Typhoon, or the TRV1A, or the Martin Baylis which has hard anodised alloy cylinders, rather than cast iron. I realise these engines run at about 30-45psi so superheat is not inevitable or even very hot, but if it does happen do they cook? Should they be confined to ordinary boilers?

I’m interested in building an 1880’s torpedo boat model, the original of which was 62 feet long but extremely low built. 1 inch to 1 foot would be about the right size for an RC model but the depth of the hull and low deckhouse height means that a D10 would be too tall (as well as too powerful). While a Stuart Sun would fit, they are not self starting or reversing so I’m looking at some of the new alternatives mentioned above, most of which are about 100mm tall. Hence my question.

My main interest is in the burner and steam generator control (although I know nothing of electronics) so would in the first place go for a ready built engine to get the hang of things.

Cheerio
another Mike
Title: Re: Flash steam plant control.
Post by: TurboTyne on May 22, 2015, 04:36:12 PM
 Hi Mike and welcome to the forum.
I cannot help with your question about tolerance of superheat by those engines except to comment that with a monotube boiler and an electronically controlled burner you could  (in theory) protect the engine from excessively hot steam anyway.  Also, I wanted to say that I’m glad you mentioned the E.T. Westbury burner since I had passed it by before and now I’ve gone back for another look I realise it is an interesting design. You said it looks like the pilot on your car’s boiler so I am just wondering - what was your main burner like? I have a copy of an article published in Model Engineer in 1932 that describes a Thorne boiler. This had a vaporising type burner where the vapour came out through many small perforated discs across the floor of the fire-box. That boiler was also fitted in a Stanley car. Was that a different system to your one?
Interesting choice of boat.  I am working towards building a WW1 destroyer and even with that, it seems it will be a challenge to keep the steam plant to be low enough in the hull. Have you decided upon a specific boat?  I have drawings of the torpedo boat No. 80. This was larger than the one you mentioned since its length is stated as 135 ft and beam 14 ft. I wonder if the hull might be better proportioned. The drawings are of the actual boat rather than a model and include 11 cross-sections. They show engines, boiler, bunks etc.  If you want a scan please contact me via a personal message since I should not post them on the forum.
Regards
 
Mike
 
Title: Re: Flash steam plant control.
Post by: Jerry C on May 22, 2015, 04:59:00 PM
TVR engine build instructions specify 35psi max and no drier/superheat.
Jerry.
Title: Re: Flash steam plant control.
Post by: Stoneflash on May 22, 2015, 09:22:19 PM
Hi Mike and welcome to the forum.
I cannot help with your question about tolerance of superheat by those engines except to comment that with a monotube boiler and an electronically controlled burner you could  (in theory) protect the engine from excessively hot steam anyway.  Also, I wanted to say that I’m glad you mentioned the E.T. Westbury burner since I had passed it by before and now I’ve gone back for another look I realise it is an interesting design. You said it looks like the pilot on your car’s boiler so I am just wondering - what was your main burner like? I have a copy of an article published in Model Engineer in 1932 that describes a Thorne boiler. This had a vaporising type burner where the vapour came out through many small perforated discs across the floor of the fire-box. That boiler was also fitted in a Stanley car. Was that a different system to your one?
 
Mike

Here are some pictures of the last version of the pilot I made to burn unleaded petrol at about 25psi. The biggest problem with the pilot on the Stanley is that it is right at the front of the car in a gale of cold air which makes it almost impossible to stop petrol from condensing before it gets into the mixing chamber of the pilot. Many people use hexane to solve that problem but I felt that was too flammable to keep around the shed so made a special pilot of which the jet was well into the hotter area of the burner casing. It worked very well. The main burner has a pair of venturi air intakes, again facing the front of the car, with jets fed by a 6ft length vaporiser over the fire which, when plied with vaporised 50/50 petrol diesel induce air into the venturis, and then via a mixing chamber beneath the main burner plate which is of cast iron with 7000 holes drilled so that the flame is more like a gas fire than a blowlamp. The main fuel is at 140psi and is controlled by a diaphragm/spring "steam automatic" which regulates the fire at the working pressure of 600 psi. One of the pictures shows the underside of the fire tube boiler, 23" diameter by 14 inches high with 750 1/2 inch copper fire tubes, swaged at either end with an inserted steel ferrule. The second, upper coil seen in the burner picture is the superheater 12 feet of 1/2 inch bore stainless steel right in the heat of the fire. It could burn 4 gallons per hour at full chat, although it averaged about 12mpg on the road and would go about 1.25 miles to a gallon of water.
Sorry to bore you with this car stuff - I'll now have to shrink my pictures to fit the forum and then come back to the boat in another post.

Cheerio
Another Mike
Title: Re: Flash steam plant control.
Post by: Stoneflash on May 22, 2015, 10:07:45 PM
Last picture of Stanley boiler follows. This shows the superheater and the underside of the fire tube boiler - big stuff eh!! :-)
Title: Re: Flash steam plant control.
Post by: Stoneflash on May 22, 2015, 10:30:24 PM

Interesting choice of boat.  I am working towards building a WW1 destroyer and even with that, it seems it will be a challenge to keep the steam plant to be low enough in the hull. Have you decided upon a specific boat?  I have drawings of the torpedo boat No. 80. This was larger than the one you mentioned since its length is stated as 135 ft and beam 14 ft. I wonder if the hull might be better proportioned. The drawings are of the actual boat rather than a model and include 11 cross-sections. They show engines, boiler, bunks etc.  If you want a scan please contact me via a personal message since I should not post them on the forum.
Regards
 
Mike

Choice of boat - which is not final (!) is because I just like the look of the Thorneycroft built Defender 2nd Class torpedo boat. I believe they were not much of a success in practice and one can imagine suffering a few sinkings in use as that ram bow looks very likely to cause a dive dive dive emergency - perhaps I should include a deployable  airbag! On another thread in the Warships area there are pictures of parts of Defender and all of her engine which have survived in New Zealand and the model pictured below is at Greenwhich. As I said in my first post I'm an experimenter rather than a scale modeller so it makes sense to pick something with not too much detail so I can concentrate on the side that I'm more familiar with.

Thanks Mike for you offer of a sight of the plans but I think I will probably seek the proper plan if it exists. I've yet to penetrate the NMM plans section but I imagine there will be something there. I'd appreciate being pointed in the right direction of anyone has such a plan.

Re superheat -much as I thought.

Cheerio
Another Mike
Title: Re: Flash steam plant control.
Post by: TurboTyne on May 24, 2015, 08:32:53 AM
Hi Mike

I obtained plans and other documents for the destroyer that I plan to build from the NMM. The search function on their website gives an idea of what is available but after looking there I would send a message to them explaining what you are looking for.  The chaps in the plans section are very helpful and knowledgeable. They told me that the web-search is limited, can be misleading and does not always give a complete list of what they have.

By the way, if you plan for a paraffin burner the following thread might possibly give you food for thought. A much simpler pump and motor would probably be fine and avoiding the more usual pressurised paraffin (or gas) tanks should mean it is possible to store the fuel in a lightweight tank in the very bottom of the hull thereby helping to increase stability.
http://www.modelboatmayhem.co.uk/forum/index.php/topic,47453.0.html (http://www.modelboatmayhem.co.uk/forum/index.php/topic,47453.0.html)

Regards  Mike
Title: Re: Flash steam plant control.
Post by: Stoneflash on May 24, 2015, 11:10:30 AM
Thanks for the link to the paraffin burner. I'd already decided to use paraffin, having read about all the fun with cooling of gas cylinders and in any case having plenty of experience with the petrol fired pilot light of my Stanley. I'll add some thoughts to the  paraffin thread later.

I must say all this electronics speak is a bit beyond me at the moment having spent some hours going through this thread in detail but maybe an old dog can learn new tricks so maybe later on?

Cheerio
another Mike
Title: Re: Flash steam plant control.
Post by: TurboTyne on May 24, 2015, 02:12:06 PM
Well this old dog learnt the new tricks of electronics thanks to being inspired by the present thread of Ian (Flashtwo).

The following thread might also be of interest - it is by another chap who was learning the ropes regarding microcontrollers.
http://www.modelboatmayhem.co.uk/forum/index.php/topic,48245.0.html

But I suspect you could get a system working under manual control based upon standard DC motors driving water and fuel pumps and standard speed control modules without any electronic control - at least initially. I wonder if Ian would agree with this ??

Reagrds  Mike
Title: Re: Flash steam plant control.
Post by: fredgraham on January 04, 2016, 07:42:09 PM
Hi Mike (TurboTyne)

My name is Fred Graham ( long time no post) and I am wondering if you are the guy who visited me to have a look round my workshop after having visited Paddy Freeman's regatta. I believe you were/are a member of Saltwell Park model boat club. If so please advise me as I am interested in your correspondence with Ian of Vital Byte (VB) renown.

I gather from the posts about VB that you have been attempting/succeeding in making a version of this vessel yourself and I was interested in finding out more about the project.

Please contact me somehow, I am not sure what the protocol for making contact is but I live in the Low fell area of Gateshead.

Al the best even if I have mixed you up with someone else, Fred Graham
Title: Re: Flash steam plant control.
Post by: TurboTyne on January 05, 2016, 08:28:45 AM
Hi Fred

I'm afraid I am not the chap you are thinking of, but no matter. At present my electronically controlled steam plant is just that - no boat in sight yet. But the boiler, fuel and water pumps and steam temperature sensor are all working - at least they were last time I tried them. It is currently attached to a very crude steam turbine. For some time now I have been applying the microcontroller knowledge (that I acquired as a result of Ian's posts about Vital Byte) to building a tool for cutting steam turbine blades in the hope (dream) of building a turbine I can use to power a model destroyer.

Anyway, I'll send you a PM.

Rregards   Mike
Title: Re: Flash steam plant control.
Post by: ballastanksian on January 05, 2016, 10:01:03 PM
Ooh O0 there was an interesting article in Mod Boats last month about model turbines. It looked at the history and products (no longer available sadly) for turbines finished off by a piece about a gorgeous all metal model of the Warspite with two turbines!!!!

Do please keep us informed about your developments and work on this subject Mike.
Title: Re: Flash steam plant control.
Post by: TurboTyne on January 06, 2016, 08:41:25 AM
Thanks Ballastanksian - that Mod Boats issue sounds very interesting and I shall try to get hold of a copy.

Regards  Mike