Tim Wescott wrote:

And for that matter, where do you get cast iron for piston rings?

You can use the same CI that you use for the piston.
Even better, you can make the ring and the piston in one pass.


I've seen centrifugally cast recommended, but how do you get your hands on
it?

That would be hard. You could ask manufacturers of cylinders (just the
sleves). But I doubt they do have the sizes you want.
Centrifugal CI is mostly used for cylinders in cars.


Regular cast is $$$ from McMaster -- can I just visit my local
engine rebuilder and saw the snouts off of a bunch of trashed crankshafts?

A crancshaft? It will be hardened. CI from continuous castings *) isn't
that expensive. But, you get a lot of swarf ... err coal making a piston
ring out of round stock. :-)


*)
Don't know how you call it. It is a continuous process using a water
cooled, tube shaped copper mold.


Nick
--
Motormodelle / Engine Models:
http://www.motor-manufaktur.de
Ellwe 2FB * VTM 87 * DLM-S3a * cubic
more to come ...