On Sat, 22 Nov 2008 14:08:15 -0800, "Marc J. Zeitlin"
wrote:

Charlie wrote:

... They are called 'drive lugs'. They are called
drive lugs because they are what drives the prop.

With metal props, you're absolutely correct. However, with wooden
props, it is in fact the friction of the face of the prop hub on the
mounting flange that drives the propeller. The wood is not strong
enough to withstand the torque pulses (especially in the larger
engines) if only the small area in the drive lug holes was taking the
force.

a few years ago a friend just out of the shakedown flight for his
quickie Q200 flew from Orange to a flyin that I attended.

when he landed he was quizzing the other fliers from his area about
the bushfires. what bushfires the other guys asked?
I could smell bushfires all the way down here but we couldnt see where
the hell any of them were.

one of the wags asked "y' gotta wooden prop?"
"yeah"
"y' betta check y' prop mate"

so we all went over, found a screwdriver, and removed spinner, pulled
off the lockwire and took the prop off. the back of the bearing
surface of the prop was charred to a depth of about an eighth of an
inch. the bushfire was quietly developing in the spinner.

my mate was horrified because he had retorqued the prop nuts the night
before making the flight.

the prop was one made for a certain manufacturer in bundaberg and was
from Queensland Hoop Pine.
QHP imho doesnt have the crush strength needed at the hub.
I'm told that none of their props ever succeeds in service much longer
than 300 hours.they all lack the crush strength.

something for Veedubber to explore is whether epoxy saturation of the
hub area could increase the crush strength of readily available softer
woods.
laminating hard faces wont do it because they just transfer the
pressure unabated to the soft core and crush it.

btw bob your specialists are schmiked up guys. they have long beaten
the survival estimates given in my old medical texts. looks like they
are going to succeed.

Stealth Pilot