On Mon, 03 Apr 2006 19:14:53 -0400, Bob Engelhardt
wrote:

Don Foreman wrote:
... My hunch
is that with this spring constant and mass the resonant freq will be
several hertz, ...

Oh, that sounds bad. Imagine trying to watch a video that jiggles up
and down at several hertz! Seasickness in your living room - talk about
capturing the experience on tape. I'd think an order of magnitude lower
would be better ("sway" rather than "jiggle"). Of course, the "badness"
would depend upon the amplitude and the distance to the taped object. A
1" amplitude while taping the horizon would be imperceptible, but if
taping a person 6' away, probably pretty bad.

... the system will then
become a second-order highpass filter with flat response above the
cutoff freq, ... I say "highpass" because the system attenuates
boat motion conveyed to the camera at low frequencies. ...

I don't think that you'd want to pass the high frequencies, e.g.,
vibration - that would give a fuzzy picture, wouldn't it?

You're right. I don't know what I was thinking. It's a lowpass.

If it's damped properly, the resonance doesn't mean that it'll jiggle
at that frequency. The resonance just determines the corner
frequency. Response to stimulus would be flat below resonance, 3dB
down at resonance, and then go down from there.

It probably won't do much aside from couterbalance it. I doubt if
there is much boat motion component above 1 Hz, unless it's going fast
and hitting small waves.

A really steady steadycam could be made using a silicon accelerometer
(about $15 from DigiKey), a torquer (small DCPM motor) and an
electronic feedback control system. That camera would be steady
even with the boat doing the watusi. Might be kinda neat....

Oh oh - another project for Don 8-)

Uh huh. I happen to have a few sample 2-axis accels in my
goodiebox. Working on something else....don't need yet another
unfinished project.

I wonder if angular motion wouldn't be more objectionable than linear
motion. It sure is with binoculars. Wonder if a little gyro
stabilizer might work better than a spring-mass system.