# Flash Steam  or Monotube boilers



## doubletop (Jun 19, 2010)

There's been a number of references to this subject on my "Scotch Boiler" topic. It needs a topic of its own.

As a start here's Bob Kirtlys 100mph plus steam driven hydroplane. Apparently he has/(had) the record at 120mph!!!


http://www.youtube.com/watch?v=srq_pC4v5wo


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## Blogwitch (Jun 19, 2010)

Isn't it wonderful what you can get up to with a bit of heat and water, plus of course, a little bit of engineering as well.

John


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## bearcar1 (Jun 19, 2010)

Now where's the fun in all that? 100MPH in a circle, and tethered no less. A monkey could drive that thing. Now then, unhook that bad boy and lets see what that old geezer can do with it. :big:

BC1
JIM


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## fcheslop (Jun 19, 2010)

You re not wrong John (Bogs) 120 MPH for an A class hydroplane its absolutely brilliant just shows what can still be done by individuals experimenting.Mr Kirtly wrote an article for the model engineer in the late 80s or early 90s I think it was about the time that I dabbled in flash steam but I couldn't compete at this level and some times you have to know when to quit.There used to be a good small book on flash steam but the dementia's kicking in at the moment.


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## Blogwitch (Jun 19, 2010)

BC,



> Now where's the fun in all that? 100MPH in a circle, and tethered no less. A monkey could drive that thing. Now then, unhook that bad boy and lets see what that old geezer can do with it.



Any deranged idiot can get a blown V8 from an auto supermarket and make something go fast, in a straight line. That is why in the UK we don't buy large American cars, we need our cars to be able to steer around corners and sharp bends.

This chappie has most probably spent most of his modelling life developing that small engine and flash boiler, a tiny tweek here, a little twang there, with an eventual culmination where he took the world steam powered record.

In the model engineering world, this is equivalent to all your land and water speed records and all your dragster records as well. The only difference is, he has most probably only spent a few hundred bucks to get to that high position rather than bottomless pockets that everything I mentioned above would require.

This is model engine designing and making beyond your wildest dreams. 

So please don't belittle it just because it has to be tethered to control all the power that is being produced.


Fcheslop,

I am not completely ignorant of model boat issues, for the last fifty years, I was an avid model boat and steam engine designer and maker, but nothing that I have done could compare to what he has achieved. That is true dedication.


Bogs


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## HS93 (Jun 19, 2010)

as bogs said a work of art, all built and re built so many times to get the max out of it, much better than a wood plynth and glass jar over it.

peter


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## SAM in LA (Jun 19, 2010)

What a hobby.

That boat just screams as it goes around.

 th_confused0052 th_confused0052

SAM


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## bearcar1 (Jun 19, 2010)

If my Grandmother had wheels she'd have been a wagon too. I was making a joke about the craft having to be tethered. I do appreciate all of the I'm sure hard work and hours that went into the power plant and hull designs. I just found it amusing in my American way of sick humor to see such an apparent work of art going balls out to nowhere is all. I apologize to anyone that decided to take offense at my remarks. I have owned two MGBs, one while I was a teenager and one that I drive now, and both of them for just the very things that have been mentioned, that and NOT having deep pockets. :bow:

BC1
Jim


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## zeeprogrammer (Jun 19, 2010)

Thanks for the pics peter. I was wondering what they looked like up close.
Awesome!


(I knew what you meant Jim.)


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## Blogwitch (Jun 19, 2010)

Sorry for flying off a bit there Jim, but I am a great believer in dedication and personal achievement against the odds. 

Even a lowly hand hacked wobbler deserves praise, purely because it starts as one person's dreams, and is then taken to the end, no matter what the setbacks.

People very rarely get to see the trials, tribulations and heartache that a project like that takes. Just imagine spending say six months development time and making, only to find it didn't work like it should have, so start again down a different route. That is called dedication to your hobby.


John


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## fcheslop (Jun 19, 2010)

John I certainly did not imply that you were ignorant of model steam boat design and Know that is not the case.


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## Blogwitch (Jun 19, 2010)

F,

It seems like all apologies today. 

It wasn't meant to infer anything, but if it did offend, I am sorry.

John


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## fcheslop (Jun 19, 2010)

No apologise needed John.ALL THE BEST


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## doubletop (Jun 19, 2010)

What have I started here guys?

From the site http://www.flysteam.co.uk/hydro.htm


> _This branch of boat modelling is unique to the UK, it demands more from the builder/designer than any other form of model making I am aware of, which may account for the fact that its exponents are few and far between. It will be a very sad day if we lose it. These boats are the extreme of small steam engine performance where as mentioned earlier Bob Kirtleys PiscesII turns out 385 BHP per litre of cylinder capacity, 5 HP from 13 cc. This is a formidable performance and anyone can be forgiven for disbelieving the accuracy of this statement; consider the facts. There are two classes of Hydro. in this category, class A, up to 9lbs weight, 15cc IC engine or steam; and class B, up to 16 lbs weight, 30cc IC engine or steam. Notice that apart from the fact that the steamers are allowed to weigh a bit more than the IC engined boats they compete on equal terms and their speeds are very close. In class B Bob Kirtleys boat is making 120 mph (200 kph) and the IC boats are at about 130 mph (235 kph). Now the 30cc racing two stroke engine turns out about 5, some say 7 BHP so it must be true that Bob's Steamer is making about the same BHP but it is of only 13 cc displacement which works out at *385 BHP per litre*. I have been asked by persons corresponding through this web site; how is this level of power achieved? "From a blooming steam engine," as one man once colourfully put it! _



This guys has a flash steam plant in an aeroplane!!! Take the time to look over his site he has some really interesting stuff

The two books are "Flash Steam" Edgar Westbury circa 1949 and "Experimental Flash Steam" By J H Benson and A A Rayman 1973. I've read the first that got me here and am looking out for the second.

Pete


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## fcheslop (Jun 19, 2010)

Thanks for the Link Pete,a very interesting site and it was the A A Raymon book I was thinking about


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## Gemhund (Jun 20, 2010)

Okay, that is a most amazing vid and steam motor I have ever seen..
Not being the sharpest tool in the shed, can anybody point me to how does a steam engine get that kind of revolution? How does a burner heat water up to that temperature ( I assume) and give that kind of power?
I understand the flash concept i.e high heat, but how is it done? 
Oxy/hydrogen maybe ?
Wide eyed, Hans


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## doubletop (Jun 21, 2010)

Hans

Although this guy is into flying steam engines (yes flying) and not boats he has a pretty good explanation on this link. http://www.flysteam.co.uk/hydro.htm

Basically instead if heating a tankful of water until it boils off, as in a conventional boiler, these engines us small gauge stainless steel tube,in this case heated until red hot, and water is pumped through it. Theb water instantly "flashes to high pressure steam and goes straight into the engine. As well as driving a propeller, the engine has a pump attached which sucks more water from the lake and through a filter into the hot tubes and off you go until the burner runs out of gas (either UK 'gas' or US 'gas').

Hey; I've only read the book and seen the film fcheslop has been there and done that and had his boat to 70mph.

Pete


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## Blogwitch (Jun 21, 2010)

This is a pic from Model Boat Mayhem, and it clearly shows, these boats don't sit in the water, but on it.

It does in fact prop ride, that is most probably only the bottom half of the propellor, one blade, in the water (more efficient) and the front sponsons only touch occasionally to give stability. All that is achieved by years of trial and error, and a little luck at times.

Bogs


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## fcheslop (Jun 21, 2010)

Hi Hans,I don't know what is in Mr Kirtleys hydro plane.But the last one I built had a flash boiler wound in a Figure of 8 about if memory serves me right 10mm dia stainless tubing and I think I used about 12meters but not sure it was nearly 25 years ago it had two blow lamps and two feed pumps and was driven by a uniflow engine .The problems I couldn't over come was that the plant started oscillating as if some one was slamming a throttle open and shut and I couldn't find the cause you have to remember at these revs even the feed pumps valves start to oscillate and even though I had kept the lift on the pumps to a few thou the problem persisted I'm now pretty certain that I was encountering reverse flow in the boiler.In the end I had taken the project as far as my skills allowed and knew that I would never be able to reach the level of skill and commitment of Mr Kirtly who I believe is having another go at the record and if so wish him the best of luck.What originally got me interested in flash steam and I suppose steam boating was an elderly gentleman who sailed a straight runner on South Shields Marine Park this plant was flash steam and had seen a lot of use over the years and I often wonder what became of it.This gentleman helped me immensely by passing on a little of his knowledge by being approachable and willing to talk to a young man on my rare Sunday morning visits.Thanks


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## fcheslop (Jun 21, 2010)

Sorry I did not answer your question my burners used petrol and were of the vaporising type fed from a pressurised tank I used to use a bicycle pump to start and maybe that's whats going on at the start of the video clip.Its important to remember that this speed has been achieved through a lot of hard work and persistence by this gentleman on the development of the steam plant and hull.The books Pete listed earlier are a starting point but sorry to say I don't know how far the hobby has developed in the last 25 years.Just looked at MY HOBBY STORE and they list a set of drawings for Pisces2 drawing number M72 Shows the engine and boiler and some info on the hull.Thanks


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## doubletop (Jul 4, 2010)

To continue this thread a bit further I had been in touch with the guy who did "Vital Byte" that has a flash steam plant controlled by pic micro controllers that can be found on the Model Boat Mayhem site. I had asked if I could re-post some of his pics here but no reply so you'll have to go over there. However, I did this diagram.







Basically there are two control loops one with an R/C input of speed demand which controls an electric pump pumping water through the flash boiler and the other with which measures steam temp as an input which controls gas flow and hence burner rate. Request for more speed results in more water being pumped, steam temp drops, burner gas flow increases steam temp is maintained and more steam produced, so engine runs faster. 

So the only input is speed demand and the rest is controlled by the micro controllers. The guy has a lot of other instrumentation built in as part of his evolutionarily development but he is in the process of rationalizing that down the minimum necessary.

I should say this is not a 'screamer' as shown in the video in the first post but a means of taming this sort of boiler for general use.

These flash boilers have intrigued me and I had my eye on doing one with a figure of 8 of tube as I'd seen an example in the KN Harris book. I also see that fsheslop's boiler was figure of 8. In fact I'd already done the drawing and worked out the surface area when the Vital Byte guy confirmed that my guesstimates matched his design.

And by way of making it real, I've already made the water pump and had it running under PIC micro control






This is all going to happen in very slow time as I have the other boiler to finish first. And a conundrum 'is it a bird, or is it a plane.........?" "Is this a boiler or is it software and programming thread?"



Pete


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## fcheslop (Jul 4, 2010)

Just a few questions, do you use a PID prog in the pic not been very well up on programming them is there a basic prog available.What temp do you expect at the boiler, are you using a thermo couple or a thermistor for temp measurement?and Hall sensors for engine and pump rpm this is starting to get very interesting not from the point of building a high speed plant but as a simple monotube plant .The pump design could you use a scotch crank to simplify.Just ideas no criticism intended just starting to think out aloud .


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## doubletop (Jul 5, 2010)

Sorry I'm not sure what you mean by a PID. The PIC micro is by Microchip http://www.microchip.com/  there are numerous devices in their catalogue the key thing is choosing the right one for the job. Which is primarily based on the type of I/O you want to do, simple digital I/O, serial ports, A to D converters, pulse width modulation, counters, timers, etc etc the options are nearly endless. 

Programming can be done with C compilers, Basic or Assembler. There are probably more but I've always used assembler, that's probably a bit geeky but you have absolute control of the code you produce. Microchip provide a full range of development tools and demo kits. The programming is done on a PC but you need to be able to get the code from the PC to the device. I've build a number of programmers but recently purchased a basic development kit http://www.microchipdirect.com/productsearch.aspx?Keywords=DV164120. It's relatively cheap and has a full tutorial, examples etc. Its certainly the fastest way to get going but there's a few principles that need to be understood but they aren't really a subject for this forum. The PICkit2 has a 16f690 on board and apart from memory capacity I believe would have all the I/O channels required to build this controller. I may have over simplified that but if it isn't right the code is portable to bigger chips with more ports and more memory so it will just be a case of moving up to a different device.

I've no idea how this will go but I'm expecting a boiler pressure of 50psi so a temp of about 140degC I believe. I was considering using a thermistor as I've found a bead type that goes to 300degC but the Vital Byte guy advises using thermocouples. We'll see.

Yes; Hall sensors for rev counters for the engine and pump. Pump motor speed and control of the RC servo (for gas control. valve) will be PWM. Serial port used for the display (basic TTY screen using hyperterminal). All these functions exist on the 16f690 

The pump was a bit of a throw together to get me going and see if the motor could do the job. However it does have a torque of 55Kg/cm. My crank throw is 1cm and piston is 1/4" so I'd assume it should be able to pump to 616psi so more than enough. as the stroke is 2cm so 1.26 cc/stroke and the max revs are 140rpm that means it should theoretically pump 1.7litres/min. Which again is probably more than enough water.

So that's it for now really, once I get going I'll look for 8 meters of 1/4" copper tube, which should give me 145sq/ins of heating surface. If that enough or not I don't know but is close to the Vital Byte heating surface

Pete


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## fcheslop (Jul 5, 2010)

Hi Pete, PID is Proportional Band Integral Device it is used for simple examples in a car cruise control or in a domestic heating circuit to enable a constant to be reached .Very simply it looks for a gain say in temp in a given time then uses feed back to adjust itself so that it stays within the set point and stops the temp wildly oscillating around the set point.There is software available for pid control by pic chips.Have a look on WWW.CURIOUSINVENTOR.COM/PROJECTS Or try googling pid control for pic chips theres a load of sites.Apologise offered for over simplifying PID but I didn't want to go into it to deeply.


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## doubletop (Jul 5, 2010)

Interesting; I wasn't aware of PID but thank you for bringing it to my attention. http://en.wikipedia.org/wiki/PID_controller . 

I see Microchip have an application note on the subject and source code available. http://ww1.microchip.com/downloads/en/AppNotes/00964A.pdf

It certainly is worth considering. The last time I was involved in this sort of stuff was the inertial navigation systems for the Phantom and Harrier. 

_(At this point how many on this forum are wondering how far off topic we could really go with this?)_

Pete


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## doubletop (Jul 6, 2010)

I've been looking more into this PID stuff and come to the conclusion I've been living under a rock. But its certainly what is required in the two control loops.


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## flashtwo (Jun 2, 2011)

Hi,

I've just found this forum and I'm the "Vital Byte" guy.

The horizontal monotube boiler (a better description than a "flash boiler") has been developed over the last two years to give a very satisfactory performance.

This year the original monotube coil has been fitted into a vertical boiler and, with a new burner arrangement, has improved the boats performance.

I intend to build an Edwardian steam launch, the design of which specifies a vertical rather than an horizontal boiler.

An 7000 word article has been accepted by the British magazine "Engineering in Miniature" and may be published latter this year. The article details the control philosophy with particular reference to the PID mentioned above and the control loops used.

I've been using a Stuart D10 engine and the boiler now has about 240 sq.inches surface area. The engine ticks over at about 5psi and gives continuous performance in excess of 500RPM with a 5 inch, four bladed prop at about 22 psi. The boat can be stopped in the middle of the lake and restarted in reverse if necessary.

Ian.


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## picclock (Jun 2, 2011)

Hi Pete

>>My crank throw is 1cm and piston is 1/4" so I'd assume it should be able to pump to
>>616psi so more than enough. as the stroke is 2cm so 1.26 cc/stroke and the max revs are
>>140rpm that means it should theoretically pump 1.7litres/min. Which again is probably
>> more than enough water.

I'm not sure the numbers compute ???. If the piston is 1/4" diameter (6.25mm) thats an area of 30 square mm, or around 1/3 of a cm2. with a stroke of 2cm's that's 0.6cc per rev, which is only 84cc or 0.8 litres per minute.

Don't know if this helps or not - please feel free to ignore or curse me ;D

Best Regards

picclock


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## doubletop (Jun 3, 2011)

Ian

Welcome aboard. As you can see from this thread, after an initial 'flash' of activity my work around this stopped. Actually I got involved in getting my locomotive running and that has taken all my time until recently. It would be good if you could post a reference to the article when it gets published so those of us on distant shores can source a copy.

For those of you who haven't seen it take a look a Ian's stuff over here on Model Boat Mayhem

http://www.modelboatmayhem.co.uk/forum/index.php?topic=15817.0

picclock

It looks like my numbers got doubled up somewhere along the line. But it didn't get much further than building the pump I'm afraid. Maybe I'll get some inspiration and back to this once Ian's article is published.

Pete


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## picclock (Jun 4, 2011)

Hi Doubletop

What sort of valves were you using in your pump ? Are they homemade or a purchased item ?

One of the reasons I picked up on the size is that one of my projects uses a pump for 1 litre per minute against 120psi. For some reason I find it difficult to design valves that have a good flow rate when open, and yet are small in size. Any details much appreciated.

Best Regards

picclock


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## doubletop (Jun 4, 2011)

Apologies for the delay in replying, I didn't get a notification for some reason.

I scratch built the pump based on a hand pump and I'm not sure what drawings I used. I think it was one of Firebirds but I've just spent 20 mins looking for the thread and can't find it. It was nothing special and I haven't proven the flow capability, this thread is about as far as I got.

Pete


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## firebird (Jun 5, 2011)

Hi picclock

If it was based on my design you can find it here. 

http://www.homemodelenginemachinist.com/index.php?topic=2092.120

I built it to test the small boiler I built. It has proved to be very reliable and has been used several times now. Hope this helps.

Cheers

Rich


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## arnoldb (Jun 5, 2011)

I'll second Rich's pump design; works a treat for testing boilers :bow:

Picclock:


> I'm not sure the numbers compute. If the piston is 1/4" diameter (6.25mm) thats an area of 30 square mm, or around 1/3 of a cm2. with a stroke of 2cm's that's 0.6cc per rev, which is only 84cc or 0.8 litres per minute.


I agree with the approximate calculations up to 0.6cc per rev (based on the parameters from the earlier thread), but 1cc = 1ml, so 84cc is 0.084 litre.



> One of the reasons I picked up on the size is that one of my projects uses a pump for 1 litre per minute against 120psi. For some reason I find it difficult to design valves that have a good flow rate when open, and yet are small in size. Any details much appreciated.


You'll need a bigger pump and higher revs - or a multi-piston pump for that. Have you considered flap valves ?

Regards, Arnold


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## picclock (Jun 5, 2011)

@ arnoldb 

My bad - I think my typing fingers are developing Alzheimers  ???. Odd thing was I looked at it and thought it must be smaller than that - truly a brainfade moment.

@ Firebird 
The pump I'm currently using has a cylinder housing a squarish plate with an oring for the seal. The plate fits into a cylinder but its shape is square with rounded corners. as the valve lifts the fluid flows past the oring and the gap between the square plate sides and the cylinder. It also has a stainless steel spring which acts to keep the valve closed when there is no pressure differential.

I don't think this would be classed as a flap valve as the whole body of the plate is free to move. If I remember correctly, I think the problem of having a hinge mechanism inside the pump body made this too difficult to engineer. However it may be possible to rethink the construction to overcome this limitation on the Mk2. 

btw in testing I got the pump up to 900 psi before I chickened out (outlet blocked so no flow).

Thanks for the ideas and comments.

Best Regards

picclock


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