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[davep]

Hi all,
Moving on a bit from my original post regarding the steam engine which I built a couple of years ago mainly from bits of scrap (see attached pic’) and for which I now need a boiler and control system.
I have been playing around on the CAD following the reply from ‘flashtwo’ and come up with a general arrangement which works around the semi flash principle.
I haven’t made any real calculations at this stage but the boiler is based on a 2” dia’ tube laid horizontally with 10 helically coiled steam tubes underneath and a superheater outlet pipe running a double pass  through the middle (see attached pic’). Heat is supplied by gas flame channelled through the flame shroud and out of the flue. The boiler and flame shroud would be encased in a mild steel box with insulation. Control would be micro PC, probably Arduino based .
I would welcome (sensible) comments from any of the boiler experts as to whether this is a workable project and any changes or improvements to the arrangement.

[Jim72]

Hi Dave,

I'm not sure if I can provide any any more information than you already have but as I'm currently building a boiler for my 5"g Britannia which I designed myself and have had approved I may be able to suggest some useful sources of info.
I must add I'm not an expert on boilers. What little I know I've picked up from club members who really are experts well as learning along the way.

Your steam engine looks a lovely piece of workmanship did you build it yourself?

Jim

[davep]

Hi Jim, Thanks for the reply.
It's nice to know that there's someone out there with a interest in both sailing and steam, until recently I had a Parker 21 trailer sailer that we used extensively for weekend sailing on a local lake as well as trailing on holiday around the UK. I'm currenty without a boat but thinking of buying a lightweight keelboat such as a Flying Fifteen.
I made the engine mainly from bits metal found and scrounged from a plan found on the internet, it has a type of Corliss valvegear on top with a 'D' shaped spindle and appears to work quite well on compressed air down to about 5psi. I realise now of course that it has 2 drawbacks 1) If it stops near to TDC it has to be hand started and 2) it has no means of reverse. I have to sort this out on the MK 2.
The Boiler is something that I know very little about and could just go for a conventional type, but I like challenge and have always been interested in 'Flash Steam' types however they can get a bit uncontrollable so I thought something in between might be the way to go. I would just like some confirmation that it would work before cutting metal so any suggestions would be helpful.
 
Dave.
 

[tobyker]

It looks from your drg as if each water tube does a full turn between inlet and outlet. In this case there is a danger that steam will build up in the top of the loop, and risk overheating the tube. Also, if each return tube goes up to the top of the boiler, there will be no circulation in the boiler as soon as the water level has dropped below  the topof the tube. Have you consulted the K N Harris book? lots of good designs in there.

[Jim72]

Hi Dave,
Apologies for the slow response but somehow I must have hit a wrong key and the whole thing went pear shaped before vanishing into the mists

Re your boiler I'd suggest getting a copy of the Australian Miniature Boiler Standards Committee's Sub Miniature code available from AME for $A13 or about 8.50 quid. They happily do OS orders.

http://www.ameng.com.au/ame_retail_dvds_boiler_codes_and_miscellaneous.htm

I know there is the UK Blue Book but from the Model Engineer site I belong to I gather the AMBSC code gives you additional design information which should be useful to you.

Another useful source of information would be this site which gives you a nice build series of a boiler of similar dimensions to the one you're considering. While it's for a G gauge loco and not a flash steam Windemere style launch boiler it may give you some more useful information. You may notice in one of the photos the pressure gauge is fitted to the boiler via a U shaped tube that allows condensate to collect so that hot water rather than direct steam actuates the internal Bourdon tube in the gauge.

http://www.mylargescale.com/Community/Forums/tabid/56/afv/topic/aff/11/aft/123637/Default.aspx

The photo is of the smoke box end of the tube stack for the boiler I'm building for my loco, while it is much bigger the basic construction methods of silver soldering and forming the copper boiler plates remain the same.

Hope I have been able to help

Jim

[ooyah/2]

Hi all,
Moving on a bit from my original post regarding the steam engine which I built a couple of years ago mainly from bits of scrap (see attached pic’) and for which I now need a boiler and control system.
I have been playing around on the CAD following the reply from ‘flashtwo’ and come up with a general arrangement which works around the semi flash principle.
I haven’t made any real calculations at this stage but the boiler is based on a 2” dia’ tube laid horizontally with 10 helically coiled steam tubes underneath and a superheater outlet pipe running a double pass  through the middle (see attached pic’). Heat is supplied by gas flame channelled through the flame shroud and out of the flue. The boiler and flame shroud would be encased in a mild steel box with insulation. Control would be micro PC, probably Arduino based .
I would welcome (sensible) comments from any of the boiler experts as to whether this is a workable project and any changes or improvements to the arrangement.

Dave ,
Just a few comments, did you know that this style of boiler was designed by Mr A Rayman who had an article printed in ' MODEL MAKER '   1963-1964. featuring his modified Scott Boiler.

There is no such thing as Semi- flash steam, Flash steam occurs when water under high pressure instantly turns to steam, so if you are taking the steam from a wet header it's not flash steam but after going thro' the steam drier produces very hot super heated steam.
If you would like a pic of A.Raymans boiler , which is still available as a print, please send me a P.M. with your e-mail and I will scan the the page from his booklet and mail it to you as I can't post pics since the forum web page altered,before I just klicked on to Attachments and Other Options but with my Mac alas no more.

I have built this boiler and I must say that it's a very fast steamer and controllable not like a flash steam coil, I started a thread (  http://www.modelboatmayhem.co.uk/forum/index.php?topic=24875.0 ) on the forum also one of my Experiments with a Flash steam engine and coil on the R&D site about 3- clicks down from the link given.(  OOYAH A FLASH STEAMER )

You will notice that I have installed a sight glass on the boiler which is absolutely useless as the turbulence in the boiler is so great that it makes reading the glass impossible, but it is useful for seeing how much water is in the boiler before start up and firing.
This boiler was designed for a fast straight runner but it's very controllable via a screw down valve on the boiler top before going into the super heater which is about 3 ft of 1/4" O/D/ copper tube wound down in the boiler casing and in direct contact with a large paraffin burner,on my thread I have given figures of the Hydraulic test and working pressure.

Toby ,
contrary to what you say there is no problem with circulation, as I have said it's the very  opposite, if you look at the last pic which is the super heater going down into and back out of the casing it's turned nearly black due to the immense heat from the burner, the other 5/32" pipe is the water heater before going into the boiler.

As this is a proven design you should have no problem having it Certificated as long as you buy a copy of the drawing and produce it to the Tester .

Hope this helps.

George.

[davep]

Hi Guys,
Thanks for putting me right on a few points but It sounds like there is the basis of a working design I'll do a bit more research using the posts and articles that have been suggested and then give it a try.
 
Dave.