Harrison,

Here are some more pictures and illustrations for the light weight
hollow prop shaft that nobody has tried yet. The idea here is to
use the pinion shafts to connect the prop shaft directly to the
rotating planet carrier. This minimize the load path and eliminates
the cost and weight of splines. The same idea is used on the prop
end. The prop drive lugs are welded directly to the flared hollow prop
shaft. These are threaded internally for the prop clamping bolts.
No conventional prop shaft steel flange is used. This in theory cuts
the weight greatly. The prop flange (spacer, back up washer) shown
can be light weight aluminum as there is no load on it.

Since you have an NC mill and you are willing to build your own PSRU
you are the ideal person to try this idea.

I'll send some pictures of the planet gear set shortly so you can get
a feel for how small and light weight it really is.

Paul Lamar

More pictures and illustrations. The full color illustration was done by Butch.
The airplane is Ed Anderson's rotary powered RV6 and the picture was taken from
Tracy's porch at Shady Bend Air park in Florida. If I can hold this at arms length
you know it does not weigh much :)

BTW several 3 rotor turbo airplanes have flown with the four pinion versions
so we know it is hell for leather stout. The six pinion version shown here
has 50% more torque capacity.

Paul Lamar

snips.

"Burns, Mark" wrote:

Paul;

        I had an idea concerning your hollow prop shaft PSRU. The idea of welding pinion shafts onto the hollow prop shaft has always bothered me. In fact, I know of aircraft manufacturers that would never allow a part with the kinds of stresses on a prop shaft to be held together with a weld. Still yet I liked the idea. I think I found a solution that would not only eliminate the weld but also make it much simpler to mass-produce. Unfortunately it would make it heavier, but not that much. Instead of welding pinion shafts to the prop shaft simply thicken the walls, then drill out and tap holes in the end of the thicker walls in the ends and use bolts to hold the planet gears on one end and the prop flange and prop on the other. I think this would increase the reliability, cause fewer problems with the prop shaft becoming imbalanced, and mass production much simpler. It would be slightly heavier due to the increased metal in between where the pinion shafts were on your original design. This way it could be made very easily with a lathe, drill press, and tap, and eliminate welding.
        Just an idea, Tell me what you think.

Thanks,
Mark

Sure. That should work fine. You need a short section of no threads
to take the shear loads.

Paul Lamar

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