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Gyro confusion!

  1. Aug 14, 2006 #1
    Hey! this is my first post here, and I apologize if it is in the incorrect forum, but I have been banging my head against the wall over this concept and I can't seem to find a straight answer. It concerns gyroscopes.

    The question is, can two counter-rotating masses on a common spindle stabilize? or does the angular momentum cancel out, causing the gyro to fall as if it had never been spun at all? Here is an image that might make it more clear:
    http://waffleimages.inorpo.com/files/db/db30ce33c1c79796a5c309b88325f37936c1ed5d.jpe
    The red and blue rings are the masses in question, and they are attached to the spindle via the yellow ball bearings. They counter-rotate, as evidenced by the green arrows showing the direction of rotation for each mass. Assuming that both rings are spinning at the same rate, and lower point of the frame is placed on a table, what will happen?
    There are two possible outcomes here:
    1. As the rate of spin drops due to friction, the inclination to precess is canceled out by the opposite rotations, meaning it stays upright until the last possible moment.
    2. The two masses cancel each other's angular velocity and the whole assembly falls as it would if there was no spin on the weights.

    My hope is that the device will act as traditional one-weight gyro, but with a much greater inclination toward stability. Remember, the spindle/frame is rotationally isolated from the weights. Will it fall, or will be rock steady?
     

    Attached Files:

  2. jcsd
  3. Aug 14, 2006 #2

    Danger

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    Your link comes up as a forbidden page, and the attachments aren't yet approved, so your answer will have to wait. From the written description, though, I believe that it would be a stable platform.
     
  4. Aug 14, 2006 #3

    rcgldr

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    Counter rotating gyros should act as if they aren't spinning, except there are huge stresses in the bearings.
     
  5. Aug 16, 2006 #4

    LURCH

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    Stable platform. The mass in the gyros is in motion, all that motion (for one gyro) is along a plane. This gives the device inertia causing it to tend to stay aligned with that plane. Cuasing the motion of those masses to divert from alignment to that plane requires a force. Since the two planes are parralel to each other, niether gyro is providing a force to divert the other and in fact each is reinforcing the the other. Rotation in oppsite directions means that some or most of the effects of precession will oppose and cancel out, giving a platform that is more stable than two gyros rotating in the same direction.
     
  6. Aug 16, 2006 #5
    I have a question for you. I've assumed these two gyros are of equal mass. Viewed from above, if the gyro furthest from the point of support tries to precess clockwise, and the other gyro (spinning in the opposite direction) wants to precess counterclockwise, then the sum precession will be clockwise due to the outer gyro having greater leverage.

    Is that right so far?

    So, if we make the outer gyro of less mass than the inner gyro, is it possible to balance precession?
     
  7. Aug 16, 2006 #6

    rcgldr

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    Now that I see the diagram, the "outer" gyro will provide the dominant precession reaction, but the angular momentum will be greatly reduced compared to a normal gyro.

    link videos showing that opposite spin is different than same spin:

    http://demoroom.physics.ncsu.edu/html/demos/252.html

    Yes, or the same mass but spinning slower than the inner gyro.
     
    Last edited: Aug 16, 2006
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