Paul,

I've been thinking about the turbo compound idea a bit since we   talked about
it last Sunday.  I'm thinking that the exhaust turbines used for a
turbocharger aren't really that well suited for putting  horsepower  into the
crankshaft.  They are designed to spool up quickly and optimized   for driving
a centrifugal compressor.

I was looking at the turbocharger used on the P-38 and the B-17  and  it's
fairly large in diameter with the exhaust exit well away from the   shaft so
the force on the blades work a longer moment arm.  I think it  also  turns
much slower.  I'm thinking a configuration like this would be  much  more
efficient for our purposes and would allow normal gears to feed  the  power to
the crank.

Steve Brazil

Perhaps something like this? Cheaper and more durable than  building  a two liter
four cylinder turbo charged 500 HP piston engine. It should burn  at  least 5% less
fuel per HP generated than the very best piston engines, given   there is at least
as much wasted energy in the exhaust as comes out of the engine  shaft.

Paul Lamar

Yes!  I've always thought this was the best idea proposed.  It's
concentric with the motor and could use a planetary, if needed, to
transfer power to the e-shaft.  The new larger rotary would allow a
larger diameter turbine still and slow the revs.

Chris Cosman

Due to the large diameter of the turbine and the high RPM of the  rotary
I don't think the turbine needs gearing.
-- 
Paul Lamar ...No rotor no motor.

Okay, so what would it take to implement this approach?  Custom casting?
Is it necessary for the blades to be tapered or could they be made
from a high quality stainless extrusion, just cut them to length and
devise a 'keeper' to hold them in the ring?

The beauty of the hollow blades is they pump a bit of cool air down
the inside (like a furnace fan) and keep themselves cool.

To me this seems like the kind of 'bolt on' edge the rotary needs to
wipe out the competition.

Chris Cosman

Just get a turbine out of a R3350 TC for a start. Not optimum
but it would prove the concept. The blades are hollow for air
cooling.