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Thread: Momentum and Gyros

  1. #1 Momentum and Gyros 
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    Hi everyone. This is my first post so hopefully I'll do it right!

    I have two questions that have been in my head for a while but I cant quite get through the math to figure it out. Perhaps you folks can give me a hand.

    Imagine a spinning gyroscope of a fixed weight. If the weight distribution for the spinning disk could be modified while spinning, would that cause the gyroscope to temporarily lean in one direction or another? I mean, if a movable mass on the gyroscope could be moved closer or further from the edge while it is spinning, what would happen?

    Likewise, if the a spinning gyroscope had some sort of mechanism that would allow it to change its spinning speed, would that cause it to temporarily lean in one direction or the other?

    Thanks

    mafhobb


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  3. #2  
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    what is a gyrascope?


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  4. #3  
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    Nobody has any input?
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  5. #4  
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    Just chiming in here to say that if you don't get much feedback, it's probably because no one has an answer for you.

    That said, I'd have to guess that the answer to the latter question is no, just due to the symmetry of the situation, but take that with a grain of salt. I'm no expert.
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  6. #5  
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    I think that a part of the reason that you are not getting any answers, is that you are not being very clear with your question. How is the gyroscope mounted? Are you talking about a symmetric mass movement (no center of mass displacement), or an asymmetric mass movement ( center of mass displacement)?
    "Men are apt to mistake the strength of their feelings for the strength of their argument.
    The heated mind resents the chill touch & relentless scrutiny of logic"-W.E. Gladstone


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  7. #6  
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    Quote Originally Posted by mafhobb View Post
    Hi everyone. This is my first post so hopefully I'll do it right!

    I have two questions that have been in my head for a while but I cant quite get through the math to figure it out. Perhaps you folks can give me a hand.

    Imagine a spinning gyroscope of a fixed weight. If the weight distribution for the spinning disk could be modified while spinning, would that cause the gyroscope to temporarily lean in one direction or another? I mean, if a movable mass on the gyroscope could be moved closer or further from the edge while it is spinning, what would happen?

    Likewise, if the a spinning gyroscope had some sort of mechanism that would allow it to change its spinning speed, would that cause it to temporarily lean in one direction or the other?

    Thanks

    mafhobb
    As far as I can see, provided the weight distribution change you speak about took place on the rotor and in a way that was axially symmetrical, then all that would happen is the rate of spin would slow down, due to conservation of angular momentum. The gyroscope would not lean.
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  8. #7  
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    So, is there any way to make a gyro lean by modifying something on the rotor while it is spinning?
    Last edited by mafhobb; February 4th, 2014 at 09:34 PM.
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  9. #8  
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    yes
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  10. #9  
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    How?
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  11. #10  
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    Quote Originally Posted by mafhobb View Post
    So, is there any way to make a gyro lean by modifying something on the rotor while it is spinning?
    Well obviously if you move some mass of the rotor such that you create an out of balance condition you will make it tend to wobble, which is a form of dynamic "leaning" with periodicity.

    But I'm afraid I don't see what you are driving at.
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  12. #11  
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    I am wondering if the original poster had in mind something analogous to the Coriolis effect. If the angular momentum of a spinning body increases or decreases, would the earth's rotation have any effect on the direction of the axis of rotation of the body? In other words, would the axis of rotation appear to tilt, even if only by a small amount?
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  13. #12  
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    Quote Originally Posted by JonG View Post
    I am wondering if the original poster had in mind something analogous to the Coriolis effect. If the angular momentum of a spinning body increases or decreases, would the earth's rotation have any effect on the direction of the axis of rotation of the body? In other words, would the axis of rotation appear to tilt, even if only by a small amount?
    Well a gyroscope will appear to change orientation relative to an observer on the Earth's surface, of course, as this is the principle of a gyroscopic guidance systems. But I must say the OP did not read that way to me. Perhaps he or she can clarify.
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  14. #13  
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    Yes, the question is what can be done to the spinning mass of a gyroscope itself to make it change its angle witht the earth's surface. No external forces, just a physical change of the spinning mass itself.
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  15. #14  
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    Quote Originally Posted by mafhobb View Post
    Yes, the question is what can be done to the spinning mass of a gyroscope itself to make it change its angle witht the earth's surface. No external forces, just a physical change of the spinning mass itself.
    Nothing can be done to it that will have this effect, so far as I know. But since the angle of the Earth's surface changes constantly with respect to the axis of rotation of the gyroscope, due to the Earth's rotation, then the angle will change all by itself.
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