Btw that casting is supposed to house skate bearings, it's not meant to be a sliding fit, as it is now -- don't know if that was the reason cast iron was considered?

I think lost foam casting of the type I did wouldn't be possible with iron -- I can imagine big problems there from mold fragility and flammable gas. And considerable danger. I'd want to stay with regular greensand castings. Maybe others have done it, I don't know. But it doesn't appeal to me.

Also, I plan on keeping the traveling parts as light as I can, so aluminum is first choice for this part. The steel is in the base.