AMB

Of course the servos are shock mounted with
rubber grommets. The vibration is entering
through the servo arm.

The up and down vibration of the engine causes
an up and down vibration in the elevator, which is
translated to a continuous push pull vibration in
the pushrod. This causes premature wear in the
servo gear teeth and bearings.

The elevator is made of the lightest possible balsa.
It is mounted with pin type hinges for freedom of
movement. Easy hinges could possible reduce
the elevator's motion, but would be a difficult
modification with the wood already full of epoxy.

WNewbury

You would think that a balanced propeller could
be mounted in any direction. In theory it is true,
but a prop that is statically balanced, may not be
so well balanced when spinning. If there is a little
extra weight near the hub on one blade and a little
extra near the tip on the other it could look perfect
on the dubro balancer. At 10,000 rpm the heavier
tip would have more momentum and try to pull
the engine off center.

It will do this regardless of which direction it is
mounted. It will, however, add its own vibration to
that of the engine if mounted straight up at TDC.
It will subtract from the engine if mounted straight
down at TDC. Since the prop appear balanced,
you need to try both directions to find which one
is better. some props are so good you can't tell
a difference.

The propellers I use are pretty good in this respect.
I usually mount the propeller so that when the
engine stops, the prop is in a near horizontal
position (so it doesn't break in deadstick landings).

The PAW engines NEVER quit in the air, so this
is not an issue. On these engines, I mount the
prop in a direction to make it easy to flip start.
Then I mark where I want to add the lead weight.
After I weight the prop, I mount it in the same
orientation.

Jenny