Doing away with the starter was a big help.
This is a 1/8 inch thick spun aluminum bell housing
with an internal doubler stiffening up the front face.
Light weight hollow  prop shafts and needle bearings are nothing new.
The Ross has used them for years with no trouble.
What this design does is do away with a conventional prop flange. Prop
drive studs are welded directly to the hollow prop shaft.
It also simplifies the attachment of the planet carrier to the
prop shaft by welding special planet gear shaft directly to
the hollow prop shaft. This does away with another flange
and reduces the length of the load path.

These are only a couple of its advanced features :)
Like the Ross it uses needle prop thrust bearings. That too
has never given any problems in the Ross.

The Ross is one of the lightest weight PSRUs ever built
for the rotary and properly machined early versions are still
in wide spread use.

Paul Lamar

Paul,

Please talk more about how drive loads are transmitted to the propeller.

Using some rough numbers for torque peak on the output of your gearbox,
what do you see as the worst case shear loads on the drive studs?  The
reason I ask is that on my little Continental, I think clamp-up friction
between the prop flange and the propeller is responsible for the drive
loads and the bolts are just there to provide adequate clamping force.
It looks like your drive studs are only loaded in bending and shear.  In
the first drawing, does the prop site on the outside of the grey plate
or on the pink studs with the gray plate installed last?


Regards,

Matt-

This design has clamp up friction too. Nothing is in bending.
The prop sits on the outside of the plate and the studs are either
threaded or hollow and threaded for conventional prop bolts and
crush plate.

Since there are six 1/2 inch studs or drive pins (your choice).
(Could be 5/8 if you wish.)

Total shear area is 1.178 square inches for the six 1/2 inch studs.

5 inch bolt circle diameter (2.5 inch radius) and a shear stress
of only 60,000 psi that is a prop torque capacity of 176,715 inch
pounds or 14,726 foot pounds. That of course does not take into
consideration the tensile load in the bolts when they are torqued
down to clamp the wood prop. Still 14,000 foot pounds is 14,000 foot
pounds :)

Paul Lamar