Paul this may be a separate topic.

If you have a single rotor engine is there a rule of thumb to predict the
magnitude of a torque peak or do you need a dyno run for the data?  I'm also
looking for a drive for a single rotor, but my goal is to reduce the output
speed from about 7750 to about 6000.  Not an off-the-shelf ratio.  Can you
put gears like this in an off-the-shelf case or do you need a new case? The
alternative is to go to a twin-rotor and detune it.  The weight difference
between the single with reduction and detuned twin may not be that different
in terms of weight, but it does push up cost and complexity of the plumbing.
George W

Sounds like a custom box.

Paul Lamar ...No rotor no motor.

George,
Why would you need a 1.29:1 ratio the prop speed is limited to about 2,800
so if your taking the single to 7750 rpm for take-off you need a 2.76:1
ratio. Better to use the 2.85 and spin the prop at 2700 rpm. I'm guessing
you want 7750 rpm for take-off  HP. The single can produce between 115 to
125 hp at 7500 rpm with PP - how much HP do you need? A single can produce
100 hp without PP.

In regard to weight, the difference is about 100 lbs( maybe more), and more
still if you use a light weight PSRU like Richard Sohn.
George ( down under)

OK, I'll come clean.  I need a reduction for a ducted fan system that is
tip-speed sensitive.  There is no direct correlation here between the type
of fan I working on and and a free air prop.  Its one of those designs where
if it works, whee!  And if it doesn't, you'll never hear about it.  If a
single rotor is the equivalent of a three cylinder engine, do the FAA recip
torque safety factors apply?  I seem to remember running across them while
research ing drive-shafts (which I'm not using).

George W

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