This is an old idea that I had a while back but
it took me awhile to refine the idea.

There is but one moving part other than the blades
themselves. There is a 14 inch diameter air cylinder piston
and cylinder built into a 14 inch diameter spinner. Fourteen
inch diameter spinners are a good idea for rotary powered
aircraft as they give more room under the cowl for engine
and cooling systems. More specifically they give more
room over the engine for the intake manifold.

The stroke of the piston is 4 inches because that
gives a 20 degree change in pitch from climb out to
top speed. About what one needs.

The piston is fed by dynamic air pressure entering a small hole
in the front of the spinner. At 100 MPH that is about 26 pounds
per square foot. At 200 MPH the dynamic pressure is about 100
pounds per square foot. A 14 inch diameter piston is about
1.1 square foot so the force on the piston is 27.8 pounds at
100 MPH and 106 pounds at 200 MPH. More than enough force
to increase the blade pitch with about a 7 inch lever arm.

Paul Lamar


14 inch spinners are good, but 16 inch spinners are better- Like
the one from a Midget Mustang. The first 8 inches of a prop
don't do anything other than hold the rest of the prop on the hub.

Brian Trubee