Traction Engine Boiler

[wade_he]

I am building a 2 inch scale minnieapolis steam tractor as siin in Live Steam in the 70's. I am hung up on the boiler. I have gotten advise to make the shell out of stainless, of which I have a correct sized piece, and the rest (tubes, firebox, tubesheets) out of copper. Has anyone done this? Is it safe? I really want to stare, but I need advise.

Thanks, Wade.

PS. this is my first really big project. I have finished all four wheels and they are awsome.

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Wade

[SGW]

I think I would make a boiler exactly according to the plans. A boiler explosion would ruin your day big time.

[wade_he]

Thanks, that may be the way I go. I am still looking for information.

Wade

[SGW]

There's a book called something like "Model Boilers and Boilermaking" by (I think) K.N. Harris available from England. I think a guy named Dave Farmer has also written about boilermaking. Back issues of Model Engineer magazine have endless articles about making model boilers for locomotives.

I'm a little twitchy about using unknown stainless steel and copper. There's a gazillion kinds of stainless steel, and while some kinds might be acceptable for this application, others might be pretty bad. You also have the possibility of galvanic action between the stainless and the copper, or at the joints.

Not to say that it definitely wouldn't work. It might, but it's a really complex question that, to answer properly, needs a lot of information you may not have.

[wade_he]

Hey,

Thanks for the opinion. The stainless I have is for high pressure steam, 3,600 psi. I could also do the whole thing in stainless, any ideas about that?

Wade

[SGW]

Sorry, my knowledge of all this is pretty limited. As far as boilers go, I'm mostly aware of how little I know and how much can go wrong.

All stainless would give you pretty poor heat transfer compared to copper, so depending on how much excess capacity is designed into the boiler, you could end up with steaming problems if it's marginal. (I'm assuming here that the directions specify a copper boiler.)

Would you braze or silver solder the joints, or weld? If you're planning on welding, unless you are a pro I would farm out that job to a certified boiler welder.

I don't know how brazed or silver soldered joints would work on a stainless steel boiler. Silver soldered copper boilers have a long track record of success. I assume you could do the same for stainless, but it would be unfortunate to be wrong.

Also be sure, if you use brazing or silver solder, you get the right kind of material. Some kinds, I think the phosphorous-bearing, can get brittle and crack. But don't quote me on that one.