John Carmack wrote:
>
> With counter rotating blades you won't have any rolling torque, but you
> will still have a gyroscopic stabilizing effect that will make it resist
> changes in attitude.
I must disagree, John. Picture two gyroscopes with opposite spin
directions, and the frames locked rigidly together. When you tilt them,
one gyro tries to precess one way, the other tries to precess the other
way. If the angular moments of inertia and angular momenta are
identical, the two precessions will cancel, leaving you with a
gyroscopic device that will simply fall over instead of precessing.
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.
--
Love wealth above life itself, and starve in splendor.
-- Elvish proverb
Donald Qualls, aka The Silent Observer NAR # 70141-SR Insured
Rocket Pages http://silent1.home.netcom.com/launches.htm
Telescope Pages http://silent1.home.netcom.com/astronomy.htm
Lathe Pages http://silent1.home.netcom.com/HomebuiltLathe.htm
Opinions expressed are my own -- take them for what they're worth
and don't expect them to be perfect.
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