While I do not want to discourage you from your project, I would like to 
suggest another possibility that you should consider.  It would help to
track 
the history of prop hub failures with wood and metal props.  My suspicion
is 
that the cracks start because of vibrations encountered with metal props
that 
would have been damped out by a wood prop.  

A related problem is the failure of Lycoming O-320 oil pump impellers.
Does 
it make any sense that the best lubricated part in the engine should wear 
away until the keyway has eaten itself 75% of the way around the gear?  My

suspicion is that the gear is subject to high frequency oscillations
because 
it sits at the opposite end of the crankshaft from the prop.  

As you collect information it would be useful to know how many tapered
cranks 
there are out there and how many are attached to wood props.

For the nervous out there reading this discussion,  I would mention that
you 
can out a new O-200 crankshaft in your engine for the cost of a
replacement 
C-85 shaft,  giving you a 10% power increase.

Good luck, 
Bob Condon
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