wrote in message
...
On Tue, 21 Dec 2004 14:32:57 -0500, Corky Scott
wrote:

What really beats on the gears, and what automotive use does not
experience, is the harmonics. Harmonics load the gears in BOTH
directions, with in the order of 10 times the steady state torque.

That tends to shear off teeth!!!

Torsional resonance has been a problem with many PSRU units, over many
years, including units from big manufacturers of certificated equipment. If
resonance is not carefully studied and tested for, you are almost guaranteed
to have a problem.

Does your car have a harmonic balancer on the crankshaft? Why do you
suppose it is there?

I work with big trucks and we have a problem there with torsional resonance
from the power pulses of the big diesels, especially at high torque and low
rpm (sound familiar?). If, for instance, one removes a clutch with a
dampened disc and replaces it with a clutch with a solid disc, the
transmission input shaft splines might shear -- or the transmission gears --
or the differential gears. It is almost impossible to convince a customer
that his cheap clutch replacement caused his rear axle to fail, but it did!
Truck component manufacturers put a lot of effort into finding and
eliminating resonance. I hope your PSRU designer did too...

Also note that changing ANY component in the drive train can mess up the
torsional dynamics, which is a bad thing for a bunch of experimenter
homebuilders. Even cutting down a metal prop a couple inches. Why do you
suppose that the FAA will allow a 25 hour test period with a certified
propeller/engine combination, but 40 hours without?
Resonance is a big reason.
-Bob