I just finished the production prototype RV-6A/9A motor mount

yesterday.The

tooling for all the RV series(with the exception of the RV-3&4) is

ready

to

produce mounts. For more information and to see them, go to
www.conversionconcepts.com
Fred E. Breese, Conversion Concepts, Inc.

James Phillips wrote:

I've been waiting for group comments on these motor mounts and haven't

seen any. That surprises

me. So... what do you all think?

James

These are the disadvantages as I see them. 

1: The MM tubes will interfere with a tangential muffler or turbo charger.
See the 3D drawing below.

2: The vibration isolation will not be as good as it would be
with the motor mounts moved outboard as in 3D drawing #2 below.

3: The rubber bushings are subjected to higher heat from the
exhaust as they are much closer to the exhaust.

4: It is intrinsically a higher weight design. You start out with
an aluminum plate between the engine and the oil pan about 14" by 16" 
by 1/2 inch thick which weighs 11 pounds. You then either MUST 
cut large holes or mill extensive pockets in the plate to reduce 
the weight. If half the weight is reduced the plate still weighs 
five or six pounds. This is in addition to the stock motor plate 
which weighs about 8 pounds.

5: Since the lateral gyro torque loads of the prop must go through
the spacers and into the engine and then into the rubber bushings
the PSRU system is less stiff with potentially more misalignment
of the input shaft.

6: The cost will be higher if for no other reason than the cost
of the 11 pound aluminum sandwich plate. At three dollars a pound
surplus material that alone would be $33 additional. The cost of 
pocketing the plate could run up to $300 extra.
 
7: The rear mounts are way over designed as the front mounts
will take near 100% of the peak load. This unnecessarily adds
weight and requires additional tubes that might interfere with other
parts. This also means the back 90% of the 1/2 inch sandwich plate 
serves no real function.

There is no beating a Questair Venture style motor mount
using the current stock motor plate for two purposes.

Paul Lamar
 
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