Making a simple boiler.

[JasonBModerator @jasonb]

Boiler for £200 is the one you want

Edited By JasonB on 01/08/2015 10:31:56

[Gas_mantle.Participant @gas_mantle]

Thanks for the link.

That photo shows exactly what I'm intending although I intended to use 12 (or possibly more) bolts, the idea of me using 10mm thick tube is to get around the problem of a flange.

I think if I'm careful I'll have room for an O ring and suitably sized bolts.

Fizzy, can you remember the diameter of that ring and how wide the face is ?

Thanks

Peter.

[HopperParticipant @hopper]

I made this little boiler about 45 years ago for a high school project, from a piece of brass tube about 1.5" diameter with about .060" wall thickness. The ends were turned from some 1/4" brass plate, stepped and silver soldered in position. It has served two generations of boys without failure. Burner is an old cough lozenge tin full of cotton wool soaked in methylated spirits and a bit of flyscreen wire gauze on top.

The little engine is about 1/2" bore and similar stroke from memory. So does not use much steam. There is a pressure gauge that screws in the water filler fitting in the top of the boiler. ISTR it ran at anything from 5 to 30psi or so. Not particularly high when you remember that domestic water pressure is often 80psi or so. So plumbing pipe will stand up to the lower pressure for small steam engines, with no need for 10mm wall thickness overkill.

Another thing to do to dry out your steam and get rid of the water droplets is that small brass valve on the steam outlet, cracked just open. This "wire draws" the steam through the small opening, resulting in the downstream steam being at a lower pressure but same temperature as the steam in the boiler. Thus, it is technically superheated! (Very slightly.)

I should think something like this would be easier to do than trying to seal end plates with bolts etc. A propane torch with those throw away gas bottles is cheap, for the silver soldering (aka silver brazing these days).

And I have often thought those throw away propane bottles would be the perfect size and shape to make a little boiler out of. I havent checked what pressure they are rated at, but they are all steel, welded construction, not too thick walled and have a nice threaded fitting on the end that could be used to screw on a suitable steam line etc. Just have to be completely sure to get all the propane out before starting work. Steam cleaning probably the safest way.

Edited By Hopper on 01/08/2015 11:52:17

[AjohnwParticipant @ajohnw51620]

One of the odd aspects about model boilers is that there seems to be very little information on design on the web. The only book I am aware of is by Harris which I understand is out of print. Some info on the thought processes should be available as people are bound to try and it would at least give them a clue as to what to do. So this album is for info only and etc as is states in the description.

**LINK**

I might get shot for posting it. It might even get removed.

Early on he mentions reducing thickness by using monel rather than copper. He also wished that there was information around on using stainless steel as he sees it as ideal. It's good to see that things have moved on because one of the problems in this sort of area in amateur circles things don't or only very very slowly.

John

–

[Gas_mantle.Participant @gas_mantle]

Posted by John W1 on 01/08/2015 13:24:45:

One of the odd aspects about model boilers is that there seems to be very little information on design on the web.

I quite agree John, I've spent quite sometime looking for information online, there's quite a bit for more skilled modellers who can make 'proper' boilers with tubes etc and then there's the very amateurish one made from baked beans and the like.

But there's very little info about anything in between, like the sort of thing I'm interested in.

[AjohnwParticipant @ajohnw51620]

He does show one simpler design of vertical boiler but still adds pipes. The reason is to extract more heat rather than it just going up the chimney. That has a bearing on the rate steam can be fed to the engine. This is it, apart from the tubes it's as I mentioned earlier.

One aspect about the metal thickness is the time and amount of heat that will be needed to heat that up – as some one mentioned. Also the rate it looses heat at which is why they are often lagged some how.

John

–

[Gas_mantle.Participant @gas_mantle]

Cheers John,

Even that is beyond my skills and tooling at the moment, I'd love to have a go at making something more sophisticated but at the moment it's just not possible.

I appreciate my idea won't be a super efficient steam generator but I'm convinced it will power small models like I'm currently building and will be perfectly safe.

Peter.

[nigel jones 5Participant @nigeljones5]

sorry – thought it was to be made in copper not steel! Regarding the o ring dims,(wait for the cannons to start firing!!) I just got one that looked like it would fit and machined the groove with a parting tool till it looked right and the o ring just stood proud of it. Thats all I ever do when its just a static seal, and ive honestly never had one leak. Ive got all the tecky dims if needed but for a compression seal they arent that fussy. And if your making out of 10mm steel theres absolutely zero chance of it exploding at this size given the restriction on heating area. Firing it will propably require more thought than building it though! The face was no bigger than 10mm. I got a bit close with the holes but even a tiny break through would have no bearing on the seal. o ring was thicker than 1/8 im sure, hence the not so critical groove depth. Im currently building a self designed steel boiler for my 7 1/4 invicta. Not had the design approved yet but I have every confidence it will be – all the others have been. I realy should keep a propper record of the approved designs including the 2" minnie I just did for a fellow on here.

[Gas_mantle.Participant @gas_mantle]

Thanks Fizzy,

What you've done is pretty much what I'm planning to do albeit I'm intending a slightly larger diameter and more bolts.

The steel supplier has tubes in 3.5" and 4" OD both with 10mm thick walls as yet I haven't decided which to go for.

I take your point with walls that thick I'll probably have more trouble heating it than exploding it !

Cheers

Peter,

Edited By Peter Nichols on 01/08/2015 20:54:20

[Paul LousickParticipant @paullousick59116]

Building and operating a safe boiler is of the utmost importance, both to yourself and to spectators. A boiler is potentially a bomb, waiting to explode. Steam at boiling point is 100 degrees C, at 180 psi it is approx 180 deg.

Boilers in Australia must be built to a code and inspected by a certified inspector.  The code for boilers with a design pressure of more than 250 kpa, barrel diameter of more than 100mm & water capacity of more than 1 litre.

AMBSC Boiler Code – Part 1 – Copper Boilers

AMBSC Boiler Code – Part 2 – Steel Boilers

Working Pressure:  250-700 kPa (36-101 psi)

Boiler diameter:  4” – 14” Dia

Water Capacity:  Fire tube – 50 litres max

Water Capacity:  Water tube – 25 litres max

 

(There is also a code for Sub-Miniature boilers but I have not read it)

Documents available from:

Boiler codes developed and published by the Australian Miniature Boiler Safety Committee (AMBSC)

http://www.smex.net.au/Store/Store_AALS-Codes.php

These books specify the type and size of materials required to build a boiler, construction technique, safety equipment and testing requirements. Everything that you need to safely build a boiler.

Paul.

Edited By Paul Lousick on 02/08/2015 01:54:01

Edited By Paul Lousick on 02/08/2015 01:55:15

[JasonBModerator @jasonb]

Having suggested a low rated safety valve much like Brian John is using for his small boilers that would keep it below 30psi and as the total capacity would be 0.75lts (100OD x 150lg)that would keep below the 3bar/ltr rule and also bring it within the Aussie sub-miniature catagory. Also does the Aussie rule apply to a man in a shed or only for running in public?

Nick, thinking about machining your ring groove in the end of a 150mm long x 100OD tube it won't be easy as there is a lot hanging out teh chuck. May be better to go with a thicker endplate and cut the groove on that.

[Gas_mantle.Participant @gas_mantle]

Thanks Jason, I did wonder about cutting the groove, the idea of cutting the end plate does seem to make a lot more sense.

One way or another I'm sure I can get a good seal and built something perfectly safe.

Peter.

[julian atkinsParticipant @julianatkins58923]

hi peter,

although you wont find much online perhaps, ME has contained many many designs for simple steam boiler plants for stationary engines over the years. some of these have already been refered to by previous posters.

i do not think a very thick piece of steel tube, however the ends are attached, will be much use as a boiler as it will take far too much to heat up.

LBSC described a number of very simple quick to build stationary boilers for his Christmas projects and are worth looking at if you want something cheap and simple.

running stationary engines on steam can be a messy business, plus cause problems if not careful with cast iron cylinders and pistons. i would opt for a properly designed copper and silver soldered vertical boiler fired by gas, and of course you will need to fit displacement lubricators to the engines.

cheers,

julian

[AjohnwParticipant @ajohnw51620]

What Peter could do to minimise the heat up problems is machine the steel to just leave flanges for the screws. If he uses the sums I posted from Harris which are for copper he will have plenty in hand. Leave a rad where the parts neck in just to be ultra safe. There isn't much point in making the flange thickness more than a bit over the diameter of the screws used. It would be a good idea to do the sums on the pressure load and core size of the screws.

If it's a vertical type I suspect he will have problems using an O ring seal at the hot end. Maybe not horizontal with the heat applied a sensible distance from the ends. That would involve applying heat to the thinner sections as well. To use them on a vertical I suspect he would have to machine up a sort of cup along the lines of the usual vertical boiler say 50mm or more deep. That would allow the water to take away heat before it gets to the O ring. 50mm?? I'm guessing. As this is bolted to the tube flanges it doesn't need to be ultra thick.

I asked for ideas on home made burners in another thread. No help at all so far. This might help on that score

**LINK**

Holes could be used instead of slot and the areas reduced for different power levels.

Also this video on youtube – a "cavalier" poster maybe but he does show what burners using propane etc are about. More suitable for horizontal as he shows it.

**LINK**

Obviously there is a need to improve on his lash up and the bit of paper towel air adjustment. Most people know what a bunsen burner adjustment looks like or as some do different size holes etc until it works. Actually the hole size that came with it might be suitable or smaller if less power is needed. Can't say that I am keen on his boilers but suppose they could be pressure tested.

Myford boy on youtube shows a needle valve from the usual blow lamp being used to control a burner for a furnace. The same sort of idea could be used. Actually going back to the cavalier I would wonder about leaving the propane torch alone and fitting the burner tube directly on it. The air mix should then be close to what it should be.

There is some mention of pressure testing by filling completely with water and heating. Various methods of heating are mentioned but I would try a hot air gun first. Bunsen burners and gas stoves sound a bit extreme to me. The pressure will rise and can be read of the boilers pressure gauge. It could also be pumped up with a bicycle pump.

John

–

 

 

 

Edited By John W1 on 02/08/2015 11:18:59

[Paul LousickParticipant @paullousick59116]

Hi Jason,

The Aussie code only specifies the minimum requirements for an amateur engineer to build a safe boiler. Material sizes for the boiler are actually larger than what would be required for a commercial, professionally built boiler to compensate for the lack of skills of some model engineers.

It does not discriminate between operating a boiler to "a man in a shed or only for running in public". No one would know of what you did in the privacy of your own shed unless something went wrong. But would you risk the chance of a boiler exploding and scalding you with boiling water and steam, possibly causing permanent injury to your face and eyes ?

Paul.

[AjohnwParticipant @ajohnw51620]

It seems that in order to see them the Aussie standards have to be paid for. The introduction on their web site does mention where members of the public etc and locomotives.

**LINK**

Harris mentions the explosion aspect and has the opinion that it's not entirely correct – it's more like the way water pipes burst when frozen. The problem is what comes out – the water is at a temperature that it can only get to under pressure. Release the pressure and it will vaporise into super heated steam where it escapes just like it does from a safety valve.

Interesting link

**LINK**

Must admit I have mixed feeling about this sort of thing. It can get out of hand and kill hobbies completely. Also about comments like that the silver solder didn't break in that pdf – it should add on those tested. Looking at older information on the subject of boiler testing 3x working pressure has been used. I've seen comments about strength safety factors of 6 rather than the 8 Harris uses.

John

–

[Gas_mantle.Participant @gas_mantle]

Hi all,

John, the boiler will be a horizontal and I had intended to make a slight flat face along one side as a bottom in order that the area receiving the heat with be slightly thinner. Once I've got a pressure gauge and safety valve and had chance to look at them properly I thought I may also do the same to the top face also.

I'll see how long it takes to heat up etc then if necessary I can always turn down the whole diameter apart from the ends where the plates are bolted. In effect I'll have a tube with inbuilt flanged ends.

Julian who is LBSC ? do you have links please ?

Peter.

[AndyPParticipant @andyp13730]

Google is your friend ! LBSC

[AjohnwParticipant @ajohnw51620]

I came across an interesting thought on a vertical boiler so thought it might be worth posting here to keep it all together.

It looks like an interesting mix of water content and heating area to me plus a fair chance of super heating if the space at the top is big enough.

John

–

[JasonBModerator @jasonb]

Plenty of vertical boilers like that about John, they usually have a "smokebox" at the top that gathers all the fule gasses into one chimney

[AjohnwParticipant @ajohnw51620]

I thought that the general proportions of space tor the fire, flue tubes and water are a bit different to what I have seen at the model engineering end. Probably not as efficient but maybe more convenient.

John

–

[Author]

Posts