Hi, All
As a mechanical engineer, vibration problems are annoying but also a
challenge. I have been pondering possible "simple, elegant" solutions
and the first thing that came to mind is the small weight on a long rod
to significantly increase the moment of inertia. The inertia can be
increased by adding weight to the system or putting a smaller amount of
weight rigidly attached, away from the system. This is used by most
competitive archers to minimize the the disturbance in aim while loosing
the arrow. Also by the guy/girl walking a tightrope. The setup used in
archery tends to be a long (about a meter) rod (usually Carbon but
sometimes Aluminum) with a small weight (less than .25 kg) at the end of
the rod. The rod or in some cases rod's are mounted perpendicular to
the bow. My thought is that a similar although much smaller arrangement
could be applied here. The amount of jiggle imparted by the
mirror/aperture compared to releasing a bow string is many magnitudes
smaller. The rod could be short (.5m?) and the weight (.1 kg?). Only
by "fully" understanding the mechanism of motion could one predict the
"best" position for the rod/weight combo but many have already devised
the necessary test setups to derive this empirically. We may find that
the length of the rod or the size of the weight might vary from lens to
lens and due to differences in mass and length. All that is needed is
to increase the inertia to reduce the amplitude. I have been thinking
about getting a mono pod for the race track, a setup like this would
definitely help there. I know it's easy to just think about solutions
when somebody else is going to have to do the work, but maybe "somebody"
will have the time and energy to try this out.
Mike Butler
Chief Mechanic / Engineer
Team FCAR
http://home.earthlink.net/~teamfcar/
Dublin, California
Date: Mon, 31 May 1999 14:23:55 -0700
From: Winsor Crosby <wincros@xxxxxxxxxxxxx>
Subject: RE: [OM] Vibrations with MLU on OM-1
We do have some empirical evidence here - Gary's lens test with the
200mm
lenses. Horribly degraded images. Since there is no tripod ring on these
lenses they are constrained to be unbalanced on the tripod. So
unbalanced
tripod mounting is not_always_best. It seems to be more complicated than
that. Probably it has to do with pendulum effect and its period of
vibration. Maybe some imbalance is good, but too much is bad?
Winsor
Winsor Crosby
Long Beach, California, USA
mailto:wincros@xxxxxxxxxxx
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