Charlie and Tupper England wrote:

ACRE NL wrote:

Don Dunbar wrote:

Hi Paul and group,
Attached the Velvet drive drawing, This can be found at www.marinegears.com/index.html

The bearing spread does look marginal for an aircraft Don.
As much as 600 ft pounds due to prop gyro torque can be applied
to the output flange of an aircraft PSRU.

A boat PSRU never sees anything like that much torque.

What is the distance between those output shaft bearings?

Paul Lamar

I'm not an engineer & I didn't stay at a Holiday Inn last
night. But marine abuse has always seemed much more severe
than the a/c environment. What's the bending load on the
output shaft when 480hp worth of torque drives the tips of a
20" (or bigger?) prop into the surface of the water after
the boat hull & prop get airborne? Also, some racing boats
run continuously with only 1/2 the prop in the water.

Wouldn't these bending loads approach the gyro loads of a
prop?

Charlie England

Those are torque loads Charlie. Bending loads are what happens when
you set the prop vertical and grab the bottom and top blades.
Pull out on the bottom and push in at the top blade. This is the
kind of forces you get on a spinning gyroscope. Same thing happens
on a prop. Worst case scenario is stalling the airplane at full
power. The nose can drop 60 degrees in one second. Aerobatics
engines have a lot of trouble with this. That is why the last
part of an aircraft engine crankshaft is so long and straight.

Paul Lamar
 
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