In normal flight there is no load
on the prop bearings when the prop shaft is driven by a planetary
gear set.

Paul, Where does the prop thrust go? Not being a smartass here I just

wanted to be sure I followed

where you were going. I realize needles are lighter but they do need a

better shaft surface. I

like the fact that the tapered rollers don't rely on the shaft surface

as much and are easy to

replace when worn. I really like the large diameter hollow shaft though.

Much lighter and stiffer

to boot. Bill Jepson

Into the separate thrust needle bearing.  Same as the Ross.

We harden the hollow shaft and grind it like any other bearing surface.
The spec is Rockwell C 58. Saves weight over a separate bearing race.

Paul Lamar

Several years ago I speculated about a lighter and stronger reduction unit.
This is near what I suggested. May I suggest an alternative ? On the prop
ned of the shaft use a roller bearing all the prop loads but thrust can be
taken by the roller bearing. On the gear end use a tapered roller bearing
taking the thrust of the prop plus locating the gears also with both axial
and radial location . Since the shaft is located on only one end axially,
the machining of the case is a noncritical item. I like one bearing doing 2
jobs. The bearing can be reversed for pusher or tractor applications. This
makes for a less expensive job. Also the prop flange needs to have a large
flat surface to transfer torque loads to wooden props. 6 inch diameter prop
flange is marginal. 8 inches @ 59 lb/ft bolt torque for the prop bolts  is
more than adequate margin to carry the engine torque to the prop. This
statement comes from the canard world. A 6 inch flange must be frequently
checked to remain tight and if good wood or fiberglass is not used the wood
next to the prop will crush. An 8 inch will not crush.

smale@ncinternet.net

Thanks for your suggestions. An eight inch flange would be no problem
as the aluminum flange in this design is not part of the shaft.


Paul Lamar

 
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