Larry, thanks for the reply. I was looking for something a little
more elegant than the RV-4 mount that I had built previously (please
see the attached picture). BTW, Paul has designed a RV-4 mount that
I like alot better than mine but mine is DONE and I'm not too keen
about building another mount unless I could just bolt the engine to
a conical type mount.
Ken Powell
C150 / RV-4 under construction
Ken,
That mount is interesting and the one that peaked my interest the most I
must say. The frame behind the mounts appears super strong. I especially
like that you brought a pipe in tension to the Bell housing end of the
engine. This is good for a static down force obviously but I'm trying to
figure out the load paths with a side to side movement or negative force
stall. Correct me if I am wrong please but wouldn't the approx. 35 " moment
still fulcrum directly at the rear rubber mounts?
Doug
Doug,
Ken's mount interests me as well. Do you think the "pipes in tension to the
bell housing" you mentioned would obviate some of the concerns about
streched engine bolts and unatural load transmissions through the engine
casing from end mounting? I wonder if these could be easily retrofitted to
standard dynafocals without getting in the way of exhaust & intake
apparatuses (or is that apparati?). I'm assuming you are the same Doug Fir
that posted earlier on this thread.
Alex Rose
Alex
No, the pipes in tension would not help the bolts much in a dynamic flying
situation. The trouble as I see it is not in designing or finding a method
to mount the rotary on dynafocals.
Simply said where is the wiggle happening? Near the bell housing? In this
case, assuming a stiff strong frame exist to support the vibrational
dampers, the prop has a very short moment or lever to apply force to distort
the engine especially if the rear mount is singular in the center. Now if
the engine is supported at the back, the lever and force applied is
multiplied by the increased distance of the engine's length. So of course
the expected force, density of the rubber, mount surface area etc. have to
be calculated which I assume Ken has a good handle on.
I would guess the rubber he used is extremely hard. I wonder if any damping
in this type of mount is even needed or desirable with a smooth rotary
engine but I digress. So how do we test the design? Picking the rear of a
heavy car (or weight) up using the plane as a lever and the prop shaft a
fulcrum proves little more than the static strength in that one plane of
movement.
Forgive the long dialog. You have to realize I am dealing with an airplane
with an engine mounted to a frame about 18" wide and 16" high that extends
33 inches from a little fire wall about 10" X 14" at the point of bonding.
Adding any additional wiggle that is not already inherent in the tail design
is of 'grave' concern.
Regards
Doug Fir
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