Wrathall Mark wrote:

Frank Wrote> My guess is that props are made to turn at about 3000 RPM

max

because 50

years ago that was about the max that a Lycont could turn.

If you check out WW1 airacrft powered by rotories, some of these had
performance approaching an RV-6, and ran huge propellors below 1500 rpm.
(Cleget 1200rpm, Le Rhone 1400rpm). GA aircraft turn 2500-2800rpm as the
best compromise between prop effiency and engine efficiency. If you are
going to a reduction drive you are freed from this compromise. Looking at
most prop driven aircraft with out this compromise, they mostly run a

lower

prop RPM. If you are fitting a 13b to an existing design design, you

still

have the prop diameter limitation.  Is it more efficient to run a two

blader

at lycon design speed, or a three blader of the same diameter slower?

Mark Wrathall

tommayer wrote:

Paul,
    Would you explain people are not using the higher ratio planetary
reduction gear on airplanes, and only on gyros?  From past posts it sounds
like the higher ratio has fewer inherent weak links.  Tom Mayer

Conventional wisdom has it we should keep down the RPM for cruise. Gyro guys
rarely cruise. They get up there and go berserk for a half hour or so :-)

I think we could cruise over 6000 RPM no problem. Probably a bit higher
fuel consumption.

Paul Lamar
 
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