From: Chuck Kuecker (ckuecker@mcs.net)
Date: Fri Jan 19 2001 - 05:06:41 MST
At 08:51 PM 1/18/01 -0800, you wrote:
>And if you put the two counterrotating wheels on a mount that could
>spin in any direction (I forget the name for this - three circles
>where the mount between one circle and the next, or between the
>outermost circle and the outside world, allows spinning in one of the
>three spin axis), then that would insure against any manufacturing
>defects that did introduce gyroscopic effects, and possibly allow the
>wheels to be moved. Though you might have to put each wheel on its own
>mount, since the wheels might want to twist in opposite directions in
>reaction to their mount moving.
>
>Then again, with this mount, you might not need the counterrotating
>wheel at all. The outermost mount doesn't turn relative to whatever
>it's mounted in, and everything inside is free to spin however it
>wants with respect to itself.
You are referring to a gimbal mount. This is used in inertial guidance
systems to allow the gyroscopically stabilized platform to allow the
vehicle carrying such a platform to move while the platform stays
"stationary". In that case, variations in the positions of the gimbals are
read to give the displacement from the initial position.
Gyro effects are due to the rotational inertia of the wheel. If you have
two counter-rotating wheels in the same plane, you can exactly cancel the
gyro effect by matching the inertias of the wheels. If you do this, you are
free to move the assembly without regard to gyro torque. Manufacturing
tolerances should not enter into the equation if the speeds of the
individual wheels are controllable.
Chuck Kuecker
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