How does a powerball work?

  1. A powerball is a gyroscope intended for body building.
    What I dont understand is how this powerball is feeded by the wrist movements but my gyroscope doesnt spin faster by moving it in my wrist.
    What is different from a toy gyroscope to the powerball because in their adds they say its a gyro.
     
  2. jcsd
  3. rcgldr

    rcgldr 7,526
    Homework Helper

    Unlike a gyro, the end points of the axis of a powerball are located in a circular slot. You start by spinning the ball, then rotate the powerball enclosure around. This forces the side of the end of each axis against the sides circular slot, and combined with the resistance to having the axis rotated creates enough "downforce" combined enough friction to create enough grip to increase the rate of rotatation of the interior ball. The ends of the axis are fairly small in diameter, so it doesn't take a lot of angular speed to get the interior ball rotating fairly fast.

    My experience with the original ones is they don't last long. Something seems to wear down inside the circular slot, reducing the friction and it gets harder and harder to get the interior ball to acclerate. Eventually you just can't get it to accelerate. The other issue was if you really applied a lot of force in an attempt to get the interior ball to spin really fast, it would cause the power ball to crack or split apart.

    Maybe this is fixed in the new ones.
     
    Last edited: May 15, 2005
  4. Do you think that if I buy one Ill be able to unmount it and see how it works and then mount it again
     
  5. Chi Meson

    Chi Meson 1,772
    Science Advisor
    Homework Helper

    If you "unmount it" (take it apart) you will find inside a ball that is able to spin on an axis. That's all. I doubt you will find out how it works until you understand torque and conservation of angular momentum.
     
  6. rcgldr

    rcgldr 7,526
    Homework Helper

    Unlikely, there's a lot of force on the edges of the inner slot.

    The way to understand how this works, is to imagine taking a regular gyroscope, and rubbing the side of the axis along a flat surface with a lot of friction, in order to spin the gyro.

    For the powerball, the side of the axis is forced against the sides of the slots, and the movement by the user just causes the axis sides to be spun by the sides of the slots.
     
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