Materials for steam engines

[clevinski]

Hi, All,

I have spent summer and most of the fall rebuilding my 7x14 mini-lathe, scraping the saddle, cross-slide, and compound; extending the cross-slide movement; modifying the saddle adjustment system to allow adjustment from above; implementing John Lindo's gear reduction system to increase torque; and adding a saddle lock.

Now I am ready to start on my second engine project, and I've decided I want to try the Little Husky. I would like, however, to be able to run it on steam, not just compressed air. As a result, the material selection is important. I made up a list of which material to use for which component, but ended up with a lot of expensive phosphor bronze for the cylinder, cylinder head and valve chamber, while using a brass piston. At which point I realized I don't know what I'm doing with metal selection for steam, so I decided to ask for some help here. Are there some general recommendations that the group can make on material selection of the components that come in contact with steam? Obviously, dissimilar materials where there is movement between parts, but beyond that, I'm a bit lost. Any input is appreciated...

 

[10K Pete]

Most steam engines, kits, models or full size, use cast iron for just about
everything. Depends on the size of the engine. If it's a 'bar stock' size
then anything goes (mostly) but larger engines usually have cast iron
cylinders, steam chests and bases, with bronze valves, glands, pistons,
bearings. Steel for rods, cranks, eccentrics, etc.

The requirement is to clean, dry and oil the machine after running so as
to not allow rust. Even bronze will corrode if not cared for.

Soft metals shouldn't run together like piston/cylinder obviously. Pick
metals for their bearing/running properties, and similar thermal
expansion for that part of the engine. A bronze piston in a CI cylinder
is fine IF you allow for the higher expansion of the bronze. That sort
of stuff.

Pete

 

[Mechanicboy]

I will recommend to buy a set of the unmachined Stuart steam engine to example Stuart 10V or Stuart 10H to learn out how to use tool and technique to build a steam engine. See in the E-bay or similar web site to buy the set of unmachined Stuart steam engine for a good price.

 

[10K Pete]

I will recommend to buy a set of the unmachined Stuart steam engine to example Stuart 10V or Stuart 10H to learn out how to use tool and technique to build a steam engine. See in the E-bay or similar web site to buy the set of unmachined Stuart steam engine for a good price.

Maybe a good price where you are but Stuart casting sets don't often
show up in this country and when they do... oh boy the price is high.
Frequently even higher than they were new!! I've been looking for some
time without success. :wall:

Pete

 

[Hopper]

A brass piston in a brass cylinder will work just fine.

 

[bazmak]

I have built 2 locos and by far the best,and most expensive is bronze castings
for cylinders and valves etc.Cast iron would be a second choice

 

[Blogwitch]

This is a very handy chart for finding materials that work together well

Just one major point about making an engine to run on live steam.

DO NOT use silver steel (drill rod) or gauge plate for making shafts, covers etc, even though it comes in nice ground and accurate finishes, use it only if needing to make hardened parts, it then becomes a little better at corrosion resistance.
In a damp atmosphere it will corrode very easily and the resulting rust will cause a miriad of damaged parts. I used to refurbish other peoples engines, and had to replace silver steel parts with stainless, either rod or bar/strip, before I could even look at anything else.

I hope this helps


Bogs

 

[clevinski]

Many thanks to everyone for the replies and valuable information, especially to Blogwitch for the useful chart! I'm going to put together a list of parts and materials for the Little Husky, and run it by you guys to see if I made any errors.

It seems like a set of Stuart 10V, unmachined castings from Mini-Steam in Ohio is about $150 plus shipping.

 

[bb218]

10K,
I have a Stuart Kit, twin Cylinder un-machined I think it is maybe a 10H ? I would sell it for what I have in it. I think I have around $220 in the kit in interested PM me and I will look for sure what I have. Mike

 

[clevinski]

Hello, All,

Re Stuart Kits, I had emailed them concerning U.S. distribution. Please find their reply below; perhaps it is of interest to others.

"We only have one dealer in the U.S. The Great Toy Steam Company you can find them on the net, other than that you can purchase straight from our secure website and we will ship to you in the States.

Regards,

Andy Meakin

Stuart Models"

 

[RonGinger]

For a first or second engine it might be better to do something with bar stock not castings. Castings are expensive and can be hard to set up so you get a full part out of the casting. If you screw up a part in bar stock its usually very cheap to make another. Once your basic machining skills are pretty good then try something with castings.

 

[clevinski]

Ron,

That's the plan right now... I'm planning for the casting-free Little Husky.

 

[Mechanicboy]

Maybe a good price where you are but Stuart casting sets don't often
show up in this country and when they do... oh boy the price is high.
Frequently even higher than they were new!! I've been looking for some
time without success. :wall:

Pete

Yes, it is expensive to provide a set Stuart steam engine. It is best to locate the used market where one or another selling steam engine that is not machined finished and can be less expensive to obtain.