Paul Lamar
Yes I agree Paul. I am under the impression that we were speaking
about a
Schertz beam or a bell housing mount arrangement where the two front
bushings take most of the weight. So I can enlighten the engineer a
little
better can you refer me to the webpage that shows what type of Barry
mounts
you have in mine?
Doug
Sure Barry Controls.
http://www.barrycontrols.com/
Paul Lamar
I wasn't aware that Barry Controls already makes an extensive assortment of
motor mounts for the aircraft industry. Except for some small isolators I
wasn't able to find a picture like the one we that is shown on the Schertz
beam though. Mike, before we go down this road of reinventing the wheel
wouldn't it be wiser to contact Barry Controls and see if they can supply a
mount closer to your specs? If for some reason it is to expensive or they
don't want to bother with the project then I will be happy to pursue
the it.
Usually fine tuning rubber mounts is done in the mix as well as density of
the rubber used. Barry Controls already has reams of data in real life
testing.
Doug
Well here is the data I have from their printed catalog.
You might want to contact them for a copy of the printed catalog.
Paul Lamar
I knew about the aircraft mounts that Barry makes. My question originated
with the thought that if these were optimized for Lycoming vibrations they
could be improved upon for the rotary engine frequency range.
What got me started asking is the frequency spec that Barry lists for the
22000 series mounts. The spec is in the 10-15 hertz range. I got to
thinking the other night (usually gets me into trouble) that the rubber
vibration isolation mounts may act like a low pass filter instead of a band
damping filter. More specifically, if you take the spec from the 2200x
mount at 15 hertz, the mount will isolate the engine vibrations from the
frame at anything ABOVE 15 hz. Of course we would never see any vibrations
below that on a continuous basis, particularly on the rotary. I've likely
been thinking too much again and not getting anything built.
Mike McGee, RV-4 N996RV, O320-E2G, Hillsboro, OR
13B in gestation mode, RD-1C, EC-2
Mike
I see where you are coming from now. I spoke with the engineer today,
showed him some data that Paul sent, and he said something to the fact like
'easy fix'. That is until I told him that the load on the mounts may be
subject to 6 Gs and other directional stress and that they are on an
AIRCRAFT. His facial expression changed a millimeter. In his line of work
machinery and buildings usually just sit there and vibrate. He said that in
aircraft applications we would probably be better off with a known source
and tweaking their design. Typically when he did work for my company he
would look at our machine in operation in his laboratory, and come back with
about 3 to 4 samples of different hardness for us to test. He did agree
with you that 22000 series mounts were probably inducing resonance's at
other frequencies in the airframe. What he can do is take a running engine
into his lab and see what is going on. Perhaps Mazda engineers can give me
more info when I go there late July.
I believe Tracy's Crooks RV-4 had these problem. It apparently went away
(or is masked when he changed to another prop and PSRU ratio.
Any feedback of anyone out there actually flying with Barry Mounts would be
appreciated.
Doug
Tracy does not fly with Barry mounts. I was unaware he had any problems with
the rubber mounts he did use. I think they were shock absorber rubber bushings
as I recall. His engine vibration in the cockpit is not as low as it could
be as I have flown with Tracy in his RV4. It is not objectionable in any sense
however.
All Questair Ventures fly with these Barry mounts. In theory there should be
only one resonant point for these Barry mounts. That means only 10 cps vibrations
will be transmitted. All other frequencies in our range will be filtered out.
John Slade is using these mounts in his Cozy with a differnt, more radical
design of mine called "bushings in the firewall trick". He claims zero vibration
on his web site.
Paul Lamar
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