On Feb 14, 8:41*am, Charles Vincent wrote:
bildan wrote:
On Feb 14, 6:38 am, jan olieslagers
wrote:
My friend absolotely wants it in the plane as it is in the car, i.e.
with the clutch side rearward (the plane is a traditional "puller"), and
wants to take power from the clutch side. His idea is to have a belt
reduction "behind" the engine, then a transmission axle above the engine
to drive the prop.
I think the key is that the shaft has to be thin and flexible to get
its resonance well below that of any other part of the drive train.
Going the other way to make a very stiff shaft raises its natural
resonance frequency so it's likely to match some other component
resulting in destructive resonance.

You should model that sometime...

Charles

It's been done many times - and examples built. If the propeller/
shaft resonance is well below the lowest fundamental frequency of the
engine/PSRU, you're probably OK. If it's above the lowest fundamental
frequency, you're probably not OK.

The neat thing is that the most successful solution is also likely to
be the lightest.

As an example, look at the ridiculously skinny half shafts on the rear
of a Honda CRV.

I ran the models several times on a V8 with a simple flex-plate PTO on
the flywheel housing driving an overhead shaft via a cog belt. It
didn't look as if there would be any problems at all if the propeller
shaft was thin enough.

The V8 sat low in the nose, water pump forward with the radiator in
front of that just like in a car. The prop shaft went forward over
the engine. It would fit perfectly in a 3/4 scale P-40 or a Piper
Pawnee glider tug.