Four conical mounts are designed and used for cantilevering an

aircraft

engine.
You are using only two in a bed mount situation to accept 90% of the

total

load
in the radial direction.

Paul Lamar

True, but I have 4 of them.  Since these pics were taken the rear mounts
have been modified so there are 3 supporting rods.

Dave Leonard

The two rear conical mounts in your set up have near zero load as the CG

of the

engine prop psru combination is located about where the front conical

mounts

are located. That heavy rear cross beam is doing nothing and is along
for the ride. You could also save more weight by mounting the front rubber
mounts on the psru adapter plate and bypass most of the loads on Tracy's

plate

spacers and long 10 mm bell housing bolts. This would get the front rubber
bushings 3 inches further away from the 1400-1800 degree F turbo housing.
This would then eliminate the large heavy plate you have sandwiched

between Tracy's

spacers and the front end housing of the engine. I also see no diagonals
laterally bracing the front rubber bushing holders.

Not that I expect you to do any of this as there is nothing really unsafe

about your

design perhaps with the possible exception of the non-existent lateral

bracing but it is a

good example of why this is not a good approach. On the other hand you

have known

about my approach to motor mounts as you have been on here a long time I

therefore

have no sympathy for you :) As I recall you and I had a bit of

communication on this

subject a year or two ago when I criticized a similar mount on someone

else's

airplane. Little did I know at the time it was personal :)

I'll do a 3D on an aircraft engine to show the loads on a cantilevered

conical mount

set up.

Paul Lamar

Paul,
Good idea to show the loads in this way - I confess to being ignorant in
this are as well, as previous e-mails have indicated.
Also there has been others - no longer on the site I believe, that have
promoted Dave Leonard's approach and apparently it has proven to be ideal in
a stock-car set-up, or the like.

David McCandles (from Perth) and I, have discussed the merits of this
briefly and David is unconvinced that it suitable in an aircraft
application.

 I have an open mind to everything and the idea of having the rubber mount
where the mount bolt is secured both ends, thereby eliminating any possible
bending loads, is attractive - however it may not be practical or even
necessary.
Always confused !
BTW that double plate set-up would be much heavier than my bellhousing and
may not be as strong. With the bolt on mounts it would be much simpler as
well !
George (down under)

 
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