Mike Wills wrote:

 I'm wondering if there is a consensus on drive ratio. Seems most who are
using planetaries on the higher perf airplanes are using 2.17:1 ratio. I
know of a couple of guys though who advocate the 2.85:1 ratio. A local
knowledgable racer who is putting a 13B in an RV-4 is using the Ross
2.85:1. He claims that box uses better gears, and the guys that Ive heard
of who have used it certainly havent had the problems that Ive heard of
with the 2.17:1 box.
 Obviously there is more potential horsepower available at these higher
RPMs (along with higher fuel burn). How is the durability of the engine if
run at a sustained 7500 RPM during take off and climb? Does the engine need
extra beefing up (stationary gears, etc..) for these higher RPMs? Other
advantages/disadvantages?

Thanks,

Mike Wills

I think 7500 RPM would be fine for takeoff and climb. The icing on
the cake would be a variable pitch prop to go along with the 2.85:1
PSRU.

Paul Lamar
 
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