Subbing steel for Cast Iron?

[spope14]

My students are making a stirling engine as a project. They selected it, and I support it. Had to figure out the materials,and what to buy. No budget, hate to say, the budget is frozen shut, no more spending (and I had a few bucks left, and the year is only 1/4 gone-----a bit of panic here). But alas, no matter HOW much I complain, this is the way it is....but i digress.

So a part of the engine is the "power cylinder". 2 inch OD, 1.505 ID, cast Iron specced. I m thinking of subbing 11L17 or maybe 4140 for it - most likely 4140 because of less movement. Thought of brass.

I know a bit of the lubricity of cast iron, but alas, will NOT have it unless I spend the $91.00 for the 6 foot bar, only need 24 inches, and through MSC, this is $42.00 and a shipping fee. Before running out and buying this, would like to know if alternatives exist in steels. I also have D2, A2, H13, and S7, and even brass and bronze on hand in major quantities.....
Looking for ideas, suggestions, and REASONS.

[wierdscience]

Well I don't think it will be a problem at all,hey its a stirling engine,it matters more that the cylinder be glass smooth than what if any lube it gets,and its not like its going to produce 50 hp at 5,000 rpm.

Have you considered designing the engine around a common bronze bushing?

Oh.I know,how about a common ductile iron pipe coupling?

[darryl]

How about wrist pins from large diesel engines? I don't know if they get that large, but should be excellent for cylinders if the bore is large enough. So I've been told.

[NAMPeters]

A tad more info is needed on the piston/cylinder combo and the sealing thereof. I assume that the clearences are critical so you need to be concerned about the relative thermal growth of the parts from start up to running. If there is rubbing then lubricity and surface finish are a concern. Are you starting from a proven design or creating this from scratch?

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Neil Peters

[JCHannum]

I doubt that steel would be a problem, brass might expand too much, and need different clearances.
I know at least one person who makes beautiful model engines who only uses leaded steel. His rationale is that it is much easier to machine, and he only runs them at shows so wear is not a problem. A side benefit is that it finishes and polishes and seems more resistant to rust and discoloration than other steels.
A good source of cast iron for engine cylinders is used brake pistons. You can offer an elective in Dumpster diving.

[BC21OSH]

Many machine shops have small scrap pieces laying around left over from previous jobs that they may be willing to part with reasonably or even donate for a good cause.

You might check with some in your area.

Bernard

[Michael Az]

A recient discovery I made may help you and others. I live in a small town and not a big town within 150 miles. I'm always looking for metal material for projects because buying new can get expensive, and for me, shipping charges. I have been looking for some nice cast iron for awhile. The other day a fellow told me he had pulled a cooking grill out of a fast food restaurnt and he asked me if I wanted it for the top plate which is about 3/4 inch thick. I think it is steel plate about 3 by 4 foot. I told him yes and he brought it over. It is the whole stove and I was pretty happy to find it had 8 counterweights that are cast iron 2" X 4" X 16". I just got it and haven't disasembled it yet. I wanted to mention this because everybody has a McDonalds and Burgerking. Lots of momentary switches and electrical controls, stainless handles, compressor and other stuff.
Michael

[JCHannum]

Just found this, Durabar, Grade 2 cast iron by the foot. 2" is $15.50 plus shipping.

Mark Meincke
34361 Schwartz Road
Avon OH, 44011

407-937-5630
e-mail ottosideshaft@yahoo.com
[This message has been edited by JCHannum (edited 10-27-2003).]

[This message has been edited by JCHannum (edited 10-27-2003).]

[GRH]

Try calling "Speedy Metals"
414-784-4140
they are in New Berlin Wisconsin.

They have no cutting charges and are very
reasonable. I ordered some 6" dia Alum tube
on a Mon and it arrived on Wed.
Good Service
They accept credit cards.

Regards Graeme

[Rich Carlstedt]

Cast Iron, besides being a "self" lubricated material, has several advantages over steel.
It is easy to cut, a factor utilized by some builders, it will not corode as easily as steel (important in some thermal engines!)and most of all, very stabil. It does not warp easily, and so for critical cylinders, etc, you need not worry about loosing the fit from subsequent machining work/stresses.

I think steel will work, but be aware of its disadvantages.