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To quote Al,
"I might be full of it", .... but:
A couple of years ago, when I started to read up on all the fantastic
aftermarket gadgets available and legal to the US folks (I am from
Europe and modifying vehicles is a PITA MAJOR), I read about a
vibration/torque pulse damper that consisted of a rather massive
ring with holes (don't remember if they where evenly spaced or not...)
the holes where filled with rolls (cylindrical), with what seemed of
different sizes. The rolls where free to roll around inside their
specific hole.
obviously once the crank started to turn the rolls would be drawn to
the outside, but depending on the torque pulses they would roll back
and forth inside the holes, supposedly dampening (?) vibration/torque
pulses. Supposedly a development from WW II aircraft engines.
Usable only with even number cylinder engines and even firing order engines..
On the site below this thing is called a pendulum absorber??
See:
http://www.tciauto.com/Products/Rattler/
Lynn, Bill, George, Richard - anyone knows what I am talking about? Any possible application for the 1-rotor?
Am I full of it??
TJ
On 12/4/07, George Lendich <lendich@optusnet.com.au> wrote:
Ok Al,
I can understand that now that you have explained
it further.
All we have to do is marry up the frequency of the
single rotor, one pulse per shaft rotation, to that of a known
damper.
We know that the more outward (to the edge of
the flexplate) and the softer the damper the better for the 2 rotor, 2
pulses per shaft rotation .
I believe that Richard's suggestion that the damper
for the single be closer to the centre of the flexplate.
George (down under)
I don't have any expertise on this subject. But I
do play around with harmonic vibrations all the time in physics lab. I
understand aspects from statistical point of view too. Here's my wild
theory:
Apply torque wrench to the damper. Also measure
the angle of that wrench as you apply torque. You would end up with chart that
says: at 1 degree, you have 5 lbs. At 3 degrees you have 18 lbs. Etc. If you
change the durometer of ONE of your dampers, you change the above numbers AND
the frequency response of the unit. Using above numbers you should be able to
predict effect and test a whole bunch of frequency responses. That would allow
you to tune the device to optimize the damping. It gets you away from the
"Aha!" approach of experimenting. Converts your ideas into numbers.
Just an idea. I could be totally full of
it.
-al wick
----- Original Message -----
Sent: Sunday, December 02, 2007 3:05
PM
Subject: [FlyRotary] Re: Giving up on
single rotor
Al,
It sounds like you might be right - but I wish
I had an idea of what your talking about in regard to torque V angle of
deflection.
I do my best but you have me beat on this
one.
George ( down under)
----- Original Message -----
Sent: Monday, December 03, 2007 1:19
AM
Subject: [FlyRotary] Re: Giving up on
single rotor
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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