> Paul wrote>The secret to making a simple mount is use two large rubber
 > bushing located near the engine/psru/prop CG on either side
 > of the engine.
 >
 > Mark wrote> Paul, looking at your PRSU/motor mount plate, this doesn't
look
 > to me to be that close to the CoG. If tracy's PSRU can balance a whole
built
 > up engine, it is probably too heavy :) Or are you going to mount a
Hercules
 > prop.
 >
 > I understand the way you have done your mount for your aircraft as width
is
 > not an issue, and this gives you max radiator space, but the further you
 > displace the main mounts from the CoG, the more load the aux mount will
see.
 > It would be logical to me to displace this main mount rearwards, allowing
 > shorter lighter mount tubes than forward. Especially if Mazda provided
 > mounting points on the center housing.

 There is no doubt about it Mark. The plate is ahead of the CG combination
 particularly with a wood prop. With a constant speed prop the
 CG will be within and inch or two. Butch is working flat out on
 the constant speed electric prop. The distance from the rear
 housing mounting surface to the prop flange is 14 inches.

 The design currently is a compromise with the mounts probably
 three or four inches ahead of the wood prop combo CG.
 The load on the rear mount is still low however as it is about 12 or
 14 inches further back. 4" times 250 # = 1K inch pounds divided
 by 18" is about 55 pound static load on the rear mount.
 There is no torque load on the single rear mount.

One other consideration on the motor-mount plate method, you have to remove
the whole engine/psru combination if you need to remove the psru.

Tracy voids the warranty on the psru if the 'non-standard' motor-mount plate
is used, since he has not gone through the testing to verify that it works
okay.

That said, I am interested in hearing how much a NC machined version would
be.

Bill Schertz
KIS Cruiser #4045

I support the engine with a hoist and remove the PSRU and
plate separately.

Paul Lamar
 
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