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Instead of using durometer in this case. I think it
would be better to measure torque vs. angle of deflection. Using torque wrench
and simple angle measure device. If you graphed this, you would end up with a
chart that defines frequency response of the damper. Goal to have damper
frequency response that's out of phase with the worst torsional pulses.
Once you've measured frequency response, you could
then tune it with durometer tweaks. So you might end up with 2 dampers at 50
durometer, 2 at 40, to obtain your ideal frequency response of
system.
I've always been drawn to having damper that has
more than one frequency response. You never see designs like that. So with mild
TV, it would respond one way. Suddenly it would have different response with
larger TV. Both responses out of phase. They use this method with electronics
and I've seen a few auto clutch dampers utilizing the concept.
FWIW
al wick
----- Original Message -----
Sent: Saturday, December 01, 2007 10:46
PM
Subject: [FlyRotary] Re: Giving up on
single rotor
Righ-t-o Rusty!
Thanks
George ( down under)
So what durometer is your gut feeling now
that you went this far?
Hi George,
I don't think you can compare the durometer of one
damper to another, because the physical size is as important as the hardness
of the rubber. The Autoflight drive uses a stock Centaflex coupler
that's only available in 50 and 60 durometer. It's a fairly large
diameter, and thick coupler. 50 was better than 60, but two 50's
(effectively 25) in series was way too soft. Maybe a 40 would be
good, but it doesn't exist.
Richard seems to be having better luck with
the Hirth drive. Two strokes are rough at low rpms, so perhaps
they already have the right damper for the job. I also suspect
his engine has softer power pulses at low rpms. It's a 12A for one,
and PP for another. PP is great at high rpms, but not know for good
power down low. It's the best theory I
have.
Cheers,
Rusty
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