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[flashtwo]

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!

[kno3]

Pictures?

[Bunkerbarge]

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.

[Circlip]

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. 

  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.

[flashtwo]

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.

[flashtwo]

Here's the controller photos.

Ian

[flashtwo]

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.

[Bunkerbarge]

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.

[logoman]

lovely to see it again, please keep us updated with the progress.

[mogogear]

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!!

[BarryM]

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

[SteamboatPhil]

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

[Bunkerbarge]

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.

[mogogear]

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 ........

[flashtwo]

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.

[dreadnought72]

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

[flashtwo]

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.

[BarryM]

"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

[steamboatmodel]

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

[nick_75au]

Hi Ian,
Very impressive work, I am interested in your feed pumps, any more detail on these please.
regards
Nick

[flashtwo]

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.

[flashtwo]

Here's the one with the coin before it was spent on sticky sweets!

Ian

[nick_75au]

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

[flashtwo]

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

[nick_75au]

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

[flashtwo]

Hi Nick,

That's quite correct!

Ian

[flashtwo]

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.

[SteamboatPhil]

I look forward to seeing it this weekend Ian
Phil

[kiwimodeller]

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.

[flashtwo]

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.

[flashtwo]

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.

[kiwimodeller]

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.

[flashtwo]

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.

[SteamboatPhil]

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 

[logoman]

congratulations Ian.
wish i had been there,