Jerry Hey wrote:

Paul,  here is the pic of the Tailwind engine mount (Lycoming) that I
build.  You can see the gear mount structure and how the upper end of
the receiver is braced.   Note that while the gear mount is 7/8" x
.049 tubing,  the tubes supporting the dynofocal ring are either 1/2"
x .049 or 5/8" x .049 (the upper tubes).    These have been flying in
many airplanes for many years and have been proven to be adequate.
I would like to reduce the tubing size for the rotary engine.  For
the first rotary engine mount I used 3/4" x .049.  It seems too heavy
but I don't have any engineering to back up that opinion.   The tubes
are  longer connecting up to the  mmp  then for the dynofocal mount.
I would like to use 5/8" x .049 for the rotary engine mount  provided
you agree, of course.    Jerry

Longer is the key word Jerry. The upper tubes can be 5/8 but
I think you need to stick with the 3/4 for the lower tubes for 
anti buckling reasons. The lateral braces can be 5/8 as well.

Paul Lamar
 
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