At 09:28 PM 9/19/2002 -0500, John Carmack wrote:
>At 07:16 PM 9/19/2002 -0700, you wrote:
>
>>Still don't believe me? Ever seen those weighted bicycle wheels with
>>handles on them, used for high school physics demonstrations? You spin
>>up the wheel, and hand it to someone sitting in the teacher's swivel
>>chair; tilting it will make them rotate one way or the other due to
>>precession. Now, if you make a new shaft that holds two such wheels and
>>a plate with 3-4 roller blade wheels to couple the tires, so that they
>>always turn in opposite directions at equal speeds, you can demonstrate
>>to yourself that such a device has absolutely no gyroscopic stability --
>>it completely lacks precession, which is what keeps a gyroscope or top
>>from falling. In fact, the contrarotating wheels have no more resistance
>>to tilting when spinning than they do when dead still.
>
>Ok, I need to find some spinning wheels on shafts to convince myself of
>that. I can easily admit I may not be thinking about it correctly...
>
>Does it still apply when the spinning masses are on the same shaft, but
>NOT coupled? I can see how directly coupling them could let them trade
>off forces, but two wheels (or rotors) spinning independently?
Yes -- all the coupling is for is to maintain equal angular speed
for both wheels.
-p
Mars or Bust!
www.marssociety.com
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