Here is Bud's opinion on planetary gears the rotaries have been
flying with for the last 38 years.

The truth is the planetary has six times the critical line contact
length of any spur gear of the same width and that is
why they have been used in all size aircraft engines for
the last 100 years.

Just because you can rebuild a racing engine does not mean
you are a competent engine designer or gear box designer let alone
aircraft engine designer. I know a lot of race engine builders :)
Just about every SCCA racer builds his own engines.


Paul Lamar


"What about planetary gears in a PSRU?
I choose to use the best for safety and dependability in the Geared
Drive. For this reason, I am against the use of planetary gears in a
PSRU. Consider what they were designed for; to change an automatic
transmission from one gear and into another. They were designed to work
at high RPM for only short periods of service. They are very small and
turn at ultra high RPM when in continuous use, and from twenty plus
years of personal experience in professional auto racing, my personal
opinion is that there is any way that planetary gears can possibly hold
up long term. The strongest and most dependable kind of gear is a
straight cut spur, which is what I chose to use in the Geared Drive PSRU. "

The next generation of high bypass jet engines from GE will use
planetary gears to drive the fan.
http://www.geae.com/engines/commercial/genx/
C. Smith




Our local engine builder, Pratt & Whitney, seems to think planetary gears are OK
for extended runs as well:

http://machinedesign.com/article/green-technology-jets-gear-up-to-fly-greener-06
19

http://www.sae.org/aeromag/techinnovations/1298t10.htm

http://news.thomasnet.com/companystory/829228

"ZHUKOVSKY, Russia, Aug. 19 - MOSCOW AIR SHOW - Pratt & Whitney successfully
completed accelerated endurance testing equivalent to more than 20,000 hours of
service operation on the PurePower PW1000G fan drive gear system. Pratt &
Whitney is a United Technologies Corp. (NYSE:UTX) company."



Jack Hilditch