some basic direction regarding boiler making

Hello,
I'm very new to wobbler engine and boiler making. Really I've only made one tiny one but find it great fun so far. I've started on another project and figured I better ask some questions to try to avoid some mistakes that could be hazardous.

I'm wondering about basic boiler design... stays..how they are made and when they are needed. End caps ....will mine silver soldered on be okay? Possible internal heat tubes in my boiler chamber....comments, ideas?

Any direction or suggestions would be helpful but I am feeling a bit overwhelmed with all the extensive and high end information out there and don't really think I will get that involved but just want to stay safe and have fun.

I will see if I can attach a picture.


Thank you.

PS I am checking out some of the books listed in one of the threads. Thanks

 

You need to go and talk to your local boiler inspector: they will explain to you the rules for making boilers in your country and advise you.

Jo

 

If we had a boiler inspector that would be knowledgeable about model engine boilers I would be very very surprised and if that individual existed they would be at least 200 miles away....hence why I thought I would ask here, but I guess no luck here either.

 

In the US there are no boiler inspectors for models. In some places there are state inspectors, and they might have legal responsibility for all boilers, but they simply dont have time to bother with model size stuff.

For model boilers there are hundreds of sizes, shapes and uses. You will have to give a better description of what you want to build to get a more useful answer.

In general I suggest the copy-cat approach. Browse the web look for lots of examples and build something that seems to be like most of what you find. If you kind of follow the middle of the road you wont go far wrong.

For the small boiler like your photo most are simply a can- no stays, no tubes, just a pot. This works because most dont run much more that 30 psi.

 

Hello,

I am in the same boat as you, made a couple of very simple engines and now making a tiny boiler.

Myfordboy has a series of videos on youtube about making a boiler that I found interesting ..... the second one gives details re silver soldering.

Stan Bray's book Making Simple Steam Engines is aimed at you and I. So is Building Simple Model Steam Engines by Tubal Cain, both have sections regarding boiler building.

I found the following two books to be less useful
Brazing and Soldering by Richard Lofting
Soldering and Brazing by Tubal Cain.

If you can turn your simple engines over with lung power then you dont need very much steam pressure at all, I beleive lung power = approx 2psi.

Bill

 

To be somewhat contrary, why not soft solder it?

Things like Mamod Toys have been done this way for decades.

You could check everything with a car tyre pump and pressure gauge. Set the blow off safety valve with the tyre gauge


If you think about it, old fashioned food tin cans were soldered and quite a lot went into a pressure cooker- to cook at obviously a higher steam pressure. 'Metal Box' used to do negative toroidal seams to vent the cans and they all went through solder 'horses'- before all that.

Cheers

Norm

 

I guess you could soft solder a very small boiler, but silver soldering with the newer flux coated silver rod {not cheep} is not difficult if you have the oxygen acetylene torch setup.

 

learn to silver solder.....PLEASE.....

Its not worth the risk to soft solder a boiler, even if the intent is to run low pressure. It only takes one failure of a critical part to make a fun hobby into a trip to the hospital.

 

Google this, Model Boilers and Boiler Making.pdf

It will give you a good start, and worth the $25 or so on Amazon

 

For boilers over say 10Lbs pressure.
Soft solder does not have the tensile strength.
You never ever test a boiler with air, always water as its non compressible.

 

Soft solder has been used on very low pressure small boilers but I would not recommend it for anything over 10 - 15 PSI and even then only if the joints have sufficient mechanical strength and the soft solder is used simply as a sealing agent



This is one of my own small boilers (sorry about the awful picture)

This one IS Silver Soldered but you will notice that the ends are flanged inside the boiler barrel and project quite a distance inside

There is also a copper rod stay in the centre for extra safety

The same applies to the under slung water tubes which are flared out on the inside prior to silver soldering

This was used to steam a little wobbler (oscillating) engine at a maximum of about 10 PSI.

It is probably overkill at this sort of pressure and capable of considerably more but I hope it shows what I mean about mechanical strength of the joints.

Best Regards Mark

 

{You never ever test a boiler with air, always water as its non compressible.}

When I test the boilers at my work we have city water pressure over 100 psi , I just fill the boiler to 100 psi with water and see if the safety valve pops-off {safety valves are set at 100 psi} but it does make a big water mess to clean up..

 

I'll just add this to a reason never to use soft solder on a boiler.......it melts when the boiler (if the boiler) ever runs dry.

The next run will probably not be without a few leaks at best.....or a catastrophic failure.

Sorry if I seem to be a party pooper to soft soldered boilers, but a steam powered explosion is not something I think anyone should have to go through.....................

 

Very true

I have had a soft soldered pipe union fail due to the temperature of the pipe being sufficient to melt the soft solder

If the boiler does run dry (a situation which SHOULD not occur) silver solder provides some protection in needing a fairly high temperature to actually melt it.

Also I believe (correct me if I'm wrong) that silver soldered joints actually alloy to the parent metal, to an extent, providing even greater strength

Best Regards Mark

 

Perhaps I should mention again that I was attempting to find a solution to finding a bit of wet steam for a very small engine and its boiler. No more than that.

If we want to get on the 'heavy stuff' the dangers of welding and silver soldering are just as big or bigger than playing with a toy boiler.

The risks from having oxy acetylene cylinders are immense- probably contravening insurance and safety regulations. There's a 200 metre EXCLUSION Zone in case of bottle fire and welding steel is - and has been known for decades- carcinogenic.

Perhaps others have gone far further than I intended for my guidance to the poster

Norman

 

It is a long time since I built a boiler. All I knew or needed came from a book by K N Harris : Model boilers and Boilermaking. It is available on eBay still I think

 

For a simple pot boiler capable of driving an oscillator , soft solder is adequate and has been used for at least 100 years on models by Mamod and other manufacturers.
We are talking a tube with flanged end plates and a couple of screwed pipe flanges , spirit fired and running at 15 -25 psi.
Any sensible model engineer will know how to design and prepare suitable joints for the boiler components.
For private use none of the "regulations" count , unless you live in "Big Brother Land" .
Reading some of the posts here I wonder how some people dare to switch on their machinery without a long stick.
If you wish to test your boiler fill it with cold water , removing all the air.
Plug all the outlets and fit your pressure gauge to one and a hand operated boiler pump to another and pump away .
If you haven't got a hand pump and can't be bothered to make one then apply a small flame to the boiler and the water will expand , do this until it reaches your required test pressure (often twice working pressure).
Sensibly a boiler of any design (excepting flash boilers) will require a safety valve and a water level gauge , some method of maintaining the water level is handy ( the hand or eccentric operated boiler pump)
Norman the risks of having oxy-acetylene cylinders are very low , far less than bomb disposal , or driving a car for that matter , that's why practically every factory and garage in the western world has a set.
There are many things that cause cancer including smoking , spray painting and eating bacon so I doubt we need worry about occasionally welding steel.
It shouldn't need saying that the safety recommendations for any workshop practice aught to be adhered to wherever possible , safety glasses and respirators are cheap and easy to procure.
One last point if a boiler does run dry and the solder melts it won't expode because there is no steam in it .........it's dry.
Dan.

 

{One last point if a boiler does run dry and the solder melts it won't explode because there is no steam in it .........it's dry.}
Why the boiler explodes is because the boiler operator finds no water in the sight glass and tyres to add water
with the feed water pump the water hits the red hot boiler and up it goes...That is why there are so many safeties
on boilers like the low water cut off switch..

 

Links to K.N. Harris books in PDF format.

Model Boilers and Boilermaking
http://www.fastonline.org/CD3WD_40/JF/424/19-422.pdf

Model Stationary and Marine Steam Engines
http://www.fastonline.org/CD3WD_40/JF/424/19-423.pdf

The last time I checked these links are still active. The links have been there for many years so I doubt that there are any copyright issues with these files.

Don

 

So there's a good tip from packrat , don't pump water into a boiler that has run dry and is red hot !
A scenario which probably would be worse with a silver soldered boiler.
Of course a sensible user wouldn't use a spirit burner that could contain enough fuel to completely evaporate the boiler contents and heat the boiler to dangerous levels .
I think this thread , which should be about a simple boiler for a small "wobbler" engine has completely lost it's way and a simple request for advice becomes confusticated with the irrelevent.
Dan.