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Author Topic: Flash steam plant control.  (Read 93716 times)

TurboTyne

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Re: Flash steam plant control.
« Reply #175 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
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flashtwo

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Re: Flash steam plant control.
« Reply #176 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.
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flashtwo

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Re: Flash steam plant control.
« Reply #177 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.
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TurboTyne

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Re: Flash steam plant control.
« Reply #178 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
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flashtwo

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Re: Flash steam plant control.
« Reply #179 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.
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TurboTyne

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Re: Flash steam plant control.
« Reply #180 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
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flashtwo

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Re: Flash steam plant control.
« Reply #181 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
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SteamboatPhil

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Re: Flash steam plant control.
« Reply #182 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  %%
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logoman

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Re: Flash steam plant control.
« Reply #183 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!
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flashtwo

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Re: Flash steam plant control.
« Reply #184 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
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flashtwo

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Re: Flash steam plant control.
« Reply #185 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
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logoman

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Re: Flash steam plant control.
« Reply #186 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?
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flashtwo

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Re: Flash steam plant control.
« Reply #187 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

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flashtwo

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Re: Flash steam plant control.
« Reply #188 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
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ooyah/2

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Re: Flash steam plant control.
« Reply #189 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




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


































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flashtwo

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Re: Flash steam plant control.
« Reply #190 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.
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ooyah/2

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Re: Flash steam plant control.
« Reply #191 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.
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flashtwo

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Re: Flash steam plant control.
« Reply #192 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
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flashtwo

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Re: Flash steam plant control.
« Reply #193 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.

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Xtian29

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Re: Flash steam plant control.
« Reply #194 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!

 

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Xtian29

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Re: Flash steam plant control.
« Reply #195 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?    
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flashtwo

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Re: Flash steam plant control.
« Reply #196 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.
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Xtian29

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Re: Flash steam plant control.
« Reply #197 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!
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flashtwo

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Re: Flash steam plant control.
« Reply #198 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.
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flashtwo

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Re: Flash steam plant control.
« Reply #199 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.
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