Alright,
My primary interest is the rotor itself. There is plenty of room for
improvement  there. And several design issues to consider. Material
selection is most important. My interest is using a castable alloy to
simplify the whole process. Our friend Jeff selected a common aircraft
alum billet to machine the one we saw a few months back. He suggested
using a tougher piston forging alloy when I talked to him at 7 stock.

As far as I can tell, the nasa 398 shown on your main site is the best
alum hyper alloy to cast pistons from. Looks to me like it will take the
extra heat necessary for rotor use. The beralcast 363 will produce a
lighter part and appears to spec better than most alum casting alloys on
heat issues.

No matter what, lightening the rotor by 30-50% will greatly lower the
drag on the whole system. If there is serious reason to believe that the
rotor combustion surface will react poorly to the volatile environment,
then we need to come up with a good high temp surface material to
combine with the alloy. I have in mind the image of the cross section
photo of the rotor housing steel liner with the grooves on the back
side, but using the same type liner material for the rotor surface.

If it is necessary to use a steel or iron rotor combustion surface, then
that changes how to approach choosing a good alloy to support it. We
have 250hp to contain, which means for most of us it gives us a good
enough climb up to 12000ft, no need for turbos really. Will the two best
alloys fail at these temp loads? Will the hyper alloy nasa 398 rattle
apart because it is so rigid?

Ed Carver