Subject: Motor mount question.
From: Rotary Engine
Date: 9/20/2009, 11:08 AM
To: AAA Put this in the To box


 On a completely unrelated note. I was wondering why a two point rear
 stabalizer mount is used with the combined engine mount psru aapter. It was
 mentioned that there was a bending moment on the ends of the plate and that
 during a flight test drop onto a runway some bending had occured.Obviously
 we don't design for this operating condition, but for normal use. It just
 seems that if the stabalizer mount that was a three point triangle it would
 help counteract gyroscopic loads from the propeller at increased angles of
 attack like for climb. Are we just inheriting the two point link from a
 previous successful installation without necessairly evaluating it, or is
 there some not obvious reason other than weight concerns.
 george grimes

 I don't recommend a two point rear stabilizer mount.
 How did you get that impression?
 I recommend a single rear engine mount.
 Which photo did you see that in?
 Can you email it back to me?

 Paul Lamar


Test drop onto runway did NOT bend the MM plate.  It's much tougher
than that.  I don't know if the main wheel caught first and caused the
prop to hit the ground or if the prop tip caught a clump of dirt, but
it was the sudden stop and 120 deg rotation that bent the MM plate.
See my earlier message for complete description of the accident.

Bob W.

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I think George is missing some 3D's on the rear motor mount schemes.
Here are some. There are a variety of ways of doing it.
The loads are very low. Sometimes on the order of 50 pounds due
to the motor plate being near the CG of the engine, PSRU and prop
combination.

Paul Lamar
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