Thread: Materials for small steam engines

Brass for the cylinder, stainless for the piston and con rod. Aluminium for supports, or painted steel. Flywheel can be brass, steel, cast iron or a mixture. Aluminium or plastic can be a bit light on it's own but weight can be added to the periphery. Phosphor bronze for the bearings, or some plastics are suitable PTFE, mind the heat!

You can use ordinary mild steel for the piston and con rod, just that it can go rusty.
Some have used an engineering plastic like Delrin/Acetal for the piston.


Dave'H

Assett machinery have unmachined kits, not sure of the price. It comes with everything you need to build one.

Dave

Forgot to say if you just want materials offcutsgalore on ebay have all sorts, but it does get pricey.

Dave

Yep....stainless steel on stainless steel of the same alloy will gall and cold weld to the point where even a 50 tonne press won't move it. You could try stainless on brass or different stainless alloys in contact with each other. Even a stainless steel shaft can't be made as close a fit as a brass shaft can into a steel ball bearing inner race without running the risk of it galling.

It is that sort of metalurgical question... you need to have dissimilar materials on bearing surfaces so that one performs the 'sacrificial wear' duty and provides metal on metal lubication- like phospor bronze bearings on a metal shaft.

Would the same 'cold weld' issue be a problem with the same grade of brass on brass?

I appreciate the feedback... once I sort out the materials I should be okay from there.

Originally Posted by Gerbilsquasher

It is that sort of metalurgical question... you need to have dissimilar materials on bearing surfaces so that one performs the 'sacrificial wear' duty and provides metal on metal lubication- like phospor bronze bearings on a metal shaft.

Would the same 'cold weld' issue be a problem with the same grade of brass on brass?

I appreciate the feedback... once I sort out the materials I should be okay from there.

I think brass on brass is fine......simply because you see parts made with brass on brass, including those Mammod model steam engines. Galling is related to cold/vacuum welding, Wikipedia also has a good article on the topic: Cold welding - Wikipedia, the free encyclopedia

Originally Posted by Graziano

I think brass on brass is fine......simply because you see parts made with brass on brass, including those Mammod model steam engines. Galling is related to cold/vacuum welding, Wikipedia also has a good article on the topic: Cold welding - Wikipedia, the free encyclopedia

May I suggest having a look at EJ Winter Models of NSW.
I got my castings from there to build a No 7 Bolton Horizontal steam engine.
They have all of the drawings etc & metals & tooling.
regards
Bruce

This place is very good for plans for steam engines Steam Engine Plans - most are free to download.

Dave'H

Originally Posted by Dave'H

Brass for the cylinder, stainless for the piston and con rod.

Stainless is a nightmare for expansion when hot. You'd need to be careful to match the expansion coefficient with the cylinder very carefully if you used it for a piston or it'd seize in the bore.

Try welding some and watch how it moves around.

PDW