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Tony Bird

Senior Member
Joined
Feb 20, 2011
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Location
Cardiff, South Wales, UK
Hi,

Simple Boiler.

Earlier this year I was asked that if I thought it was possible to build a boiler for a small model steam driven boat. The model which was to be about 60cm (2 foot) long with a 125mm (5”) beam unfortunately the hull wasn’t very deep about 35mm (1.25”). The boiler was a prominent part of its design it was very small of a water tube type with its chimney coming out of the centre of it. The model was to be to a Stand-off Scale’ looking like but only close to scale measurements.

Some thoughts and several drawings made, even with an increased size the boiler would be very small. Eventually it was decided that the only boiler that would give some running time would be of a ‘Pot’ design. The engine to be powered is quite small but it was thought that it would be a good idea to increase the heating area of the boiler with the addition of ‘Hedgehog’ spikes. The boiler needed to be as low as possible so there wasn’t a great deal of combustion space for the burner so a ceramic burner would be needed. It might also be possible to use ‘Sterno’ jellied meths used a chaffing fuel in a tray to fire the boiler, though it wouldn’t put out as much heat as the gas burner.

A start was made on the boiler but the project stopped as the guy that started it lost interest, so the two boilers were left in a box for the last six months. Recently I decided I needed a boiler to power a small steam engine built and it was decided to complete the boilers.

Some notes on the build so far. The copper sheet used for the boiler is 0.8mm (1/32”) thick and came from a redundant water tank. The galvanised steel sheet came from B&Q (UK hardware store). The 2mm copper hedgehog spikes came from some electric earth cable, which I think are know as ‘Tailings?’

The boiler is a low-pressure design for around 20psi to power small oscillating engines and will be hard soldered together. The annealed copper for the boiler tube was bent around a wooden former and held in place with plastic cable ties while the holes for the rivets were drilled. After riveting the seam of the tube was soldered. After pickling the boiler tube was put back on the wooden former and the holes for the hedgehog spikes were drilled. The end caps were hammered to shape around a steel former. The steel flame guard was cut using tin snips and the holes drilled with a step drill. The copper boiler supports were hammered around a wooden pattern. The flame guard/boiler support is held together with screws going into stepped nuts soldered into its parts. This is as far as the boilers were constructed to six months ago.

Yesterday I found all the pieces and cut some guides in the bases for a ceramic burner or Sterno tray.

I will post further photographs as work progresses but the boilers are of a very simple design and construction.





















Regards Tony
 
Great post. Thanks for sharing.
 
Tony,
I see that after you roll the copper shell you solder it without a butt strap joint,don't you think that one is necessary ?
George.
 
Hi George,

I see that after you roll the copper shell you solder it without a butt strap joint, don't you think that one is necessary?

No. I have used butt strap joints but with such a small low pressure boiler the extra work isn't necessary in my opinion. There is an overlap of 6mm (1/4") there are four rivets and the hard solder has penetrated right through the joint and the end cap flanges are outside the boiler.

Regards Tony.
 
Hi George,

I see that after you roll the copper shell you solder it without a butt strap joint, don't you think that one is necessary?

No. I have used butt strap joints but with such a small low pressure boiler the extra work isn't necessary in my opinion. There is an overlap of 6mm (1/4") there are four rivets and the hard solder has penetrated right through the joint and the end cap flanges are outside the boiler.

Regards Tony.

Hi Tony,
Thanks I didn't see the 1/4" O/Lap which I agree is sufficient for your boiler and with the hard brazing is more than strong enough.

George.
 
Hi,

Simple Boiler 2.

Some work on the boilers was done yesterday, after marking out holes for the steam bushes, steam dome and steam pipe was drilled in the boiler barrel. This was done while the barrel was mounted on its former a step drill was used after a deep pilot hole the same diameter as the step drills smallest size doing this helps stop the step drill wandering while drilling the former. The boiler barrel having been drilled has to be knocked off its former.

The pilot holes for the heat exchanger pins were enlarged using a brooch until the pins could be tightly pushed in having done this the first double row was soldered in after pickling the second set were fitted and soldered.

Regards Tony.



















.
 
Hi George,

I tell fibs the end cap fits inside not outside of the boiler barrel. That what comes of starting and stopping jobs.



The boiler to date was dry assembled to line up the fitting holes in the top of the boiler with the ones to be drilled in the flame guard.





Not a lot of work done, more hopefully later in the week.

Regards Tony.
 
Hi,

Managed to finish the first boiler today. Having made the boiler bushes, steam dome and the union for the steam pipe before sticking it altogether and testing it. I haven't described making the above parts as it is very similar to what was described in my Making Water Gauge thread. But I could take photographs of making them for the second boiler if it is wished. There has been a small alteration to the boilers design it now has two stays to allow the steam pipe to be in the centre of the boiler.

Bushes in back head.



Steam pipe under dome.



Steam pipe goes through the boiler and is mildly super heated before exiting the boiler casing.




Test equipment pressure gauge.



Box of adapters to attach pressure gauge to boiler.



Pump good to just over 200psi! No expense spared the cost £1.50 each!



Second test, failed first due to two small weeps.



Boiler painted with VHT paint.



Boiler in flame guard and water gauge fitted.





The chimney is a push fit on the steam dome and will take the exhast from the engine. There is the other boiler is to finish then its a ceramic burner and my version of a Goodall top-up valve to make. The safety valve will probably be a Mamod low pressure one.

Regards Tony.
 
Where did you get the expensive pump Tony,and nice job as usual.
Don
 
Tony, I'm just about at the point of needing a top-up valve, otherwise known as a Goodall valve I believe.
I would prefer to make it rather than buying one so I await your next move with interest.

John
 
Hi John,

Tony, I'm just about at the point of needing a top-up valve, otherwise known as a Goodall valve I believe.
I would prefer to make it rather than buying one so I await your next move with interest.

Just started a new thread in the boiler section on making a top up valve.

Regards Tony.
 
Hi,

I have finished the boilers chimney which is fitted with an experimental oil/steam separator.



The exhaust steam enters the chimney through the left hand pipe and goes up the chimney in a removable blast pipe which directs the exhaust near the top of the chimney against its wall. The oil and condensed steam tends to stick to the inside wall of chimney and travel down the chimney exiting via the right hand pipe into a receiver. Well that's the theory, in practice the oil water mix soon blocks the exit pipe so no steam comes out and drips into a tray. I haven't tried it over a long period and in a hull yet.

Regards Tony.
 
Nice work Tony
I am in the process of getting materials to make a boiler for Minnie traction engine.
Any help would be gratefully received.
What pickling agent do you use.I am assuming Sulphuric Acid,diluted to what strenth ?
Thanks
John
 
Hi John,

What pickling agent do you use. I am assuming Sulphuric Acid, diluted to what strength?

I haven't used Sulphuric acid for many years, Citric acid works well and is safer. It can be bought as a powder from Chemists or Wine Making Stores. Just make a saturated solution using warm water. (When no more crystals will dissolve in the water it is saturated).

If I can be of further help please ask.

Regards Tony.
 
Hi Tony,
very nice boiler, thanks for sharing the built.
I wonder why the exhaust pipes are lagged with insulating (?) material the white stuff in fact...I would have expected the opposite, cooling the exhaust pipes to condense steam (and oil) !
Cheers
 
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