charles.harbert

Paul, I mostly agree with the principles that your referencing to the Sievert"s,
but there are some shortcomings IMHO with running a 13B at over 7K rpm that they
should be aware of. One the biggest is that the fuel economy (bsfc) is
significantly reduced above 6K rpm. Although rotaries can handle high rpm they
are normally redlined at 7K rpm, and there were some catastrophic failures at
levels abv this. By designing for very high rpm, you are running the engine at
over the designed speed which will require extensive modifications ($$$ i.e.
porting, clearancing, hardened gears, race bearings,etc) to be close to
efficient and reasonably reliable. I think almost  all of the 13B's a/c
applications use the lower ratio, unless it's going in a gyrocopter, or other
large diameter propeller.

The gyro guys routinely run over 7000 RPM. I just saw three at Benson Days
in Florida.  Dave Atkins claims he has one engine in a gyro 
out there with something like 2400 hours. I don't really think you need
to get into clearancing until you get to the 9 or 10K range.
I think all gears were hardened after about 1988 or so.

Paul Lamar
 
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