The engine mounts are not highly stressed. The main problem is
   buckling of the lower members. Shot peening would not help.
   A 0.75 inch dia. 0.049 wall tube will see a max tensile load of 3000
   pounds so that is a stress of about 26,000 psi at 6G. A very rare occurrence.

   The hollow prop shaft on the other hand has to deal with continual
   torque fluctuation combined with the occasional bending loads due to stall
   or turbulence. The higher the yield psi the better.

   Paul Lamar ...No rotor no motor


Agreed on the prop shaft. The stronger the better. One of the places I
worked had a shot peener and we did almost everything. I agree that the
motor mount ISN'T highly stressed. The nice thing about the shot peening
process is that the parts exibit a more uniform strength. Again as you
said, not really needed, but comforting. I saw a lot of welded
suspension uprights in the shot peen machine. But those are more highly
stressed than the motor mounts.
Bill Jepson


Shot peening might double the cost of the motor mount.
So far most people choose the rotary mainly for cost reasons.
Therefore shot peening is not cost effective for motor mounts.
Doug of course is not concerned with cost or he would
use one of Tracy's PSRU's :)

Paul Lamar ...No rotor no motor.

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