|
Message
Rusty,
I will leave the video for a couple of days
so as to not bog down your ISP.
However I have had a long time to consider Dampers
and have gone for the polyurethane type (about 90 shore) as this has been tried
on a 4 cylinder and has been on the internet somewhere and showed up on the of
the discussion groups and in Contact mag I believe.
I know that Tracy suggests the softer the better
but it's a 2 rotor and with no toque reversals -that's
understandable.
The article suggested softer rubber dampers turned
to dust in short order.
The reason is, I believe, the distance between +ve
and -ve torque responses is much longer and the damper is caught going one way
when it is forced to go another ( in layman's language). For this reason I
believe the stiffer dampers less inclined to travel as far, as
quickly.
The material I have selected is readily available
and I purchased 300mm for $30. This is the stuff they make for the aftermarket
4WD spring mounts.
Also Tracy suggests the more toward the outer edge
of the flywheel the better for mounting the 2 rotor mounting - again
understandable. However for the larger torque fluctuations, I believe it logical
that the closer toward the centre with limit the travel.
Hope that helps.
George ( down under)
Greetings,
I made a short video
yesterday of a single rotor run. The purpose was to demonstrate and
document the prop tip behavior with the stock rubber coupler/damper, so I can
see if it gets any better with the new softer one.
As you can see, it gets
pretty wild at times, particularly when changing rpms. I'm not sure this
is completely abnormal though, because I've watched the Subaru engines on the
RAF2000 gyro do the exact same thing. They even have a bit of tip
wandering too, so some of this may be OK.
During the video, you'll
hear me say 2600 rpm, and at that point, the tips are wandering fore and aft a
bit. The next rpm tested was 3500, and it appears fairly smooth.
You'll note that my throttle control doesn't have much friction, and
closes itself if I don't hold it. By the time I say 3500 rpm into the
camera, you can see that the engine has slowed down considerably, so 3500 is
the point where I get up to come back to the camera, not when I say
3500. For that reason, 4000 rpm became a hand signal, and appears
perfectly smooth.
The video is 60 MB, so
not for the dialup crowd unless you download it overnight. Also, if
there's more traffic than I expect, I may have to shut the link down to
preserve my web space quota for the month.
Rusty
|