Precession

[Village Idiot]

Someone mentioned a layman's rule that I like for precession of a flywheel. It goes: An automobile has a flywheel turning clockwise to the driver's view as it would be seen if it were not hidden under the hood. As the car turns right, precession at the flywheel pushes the front of the car downward. This seems a good equivalent for the Right Hand Rule (RHR) which tells the same story, but requires me to name both fingers and the thumb involved in the rule to keep it all straight inside my headbone. I reccomend it to other mental defectives, and to those with fingers already labelled for other technologies. Not really though, because I doubt validity of the RHR except for toy tops and things.

 

Hold your fire! Just tell me how I am wrong. Precession flips first one way for half of a turn of the wheel, then flops back the other way back on the next half turn.

 

If the wheel spin is of constant velocity, the flip and flop are equal to each other. Every turn sees no net precession. That is the stuff navigation likes about a gyro. It is so because the second half-turn duration equals that of the first half-turn.

 

If the flop exceeds the flip, as with a toy top, the RHR has its way. The nose of the car goes down under a right-turn of the vehicle. Assuming that a toy top is coasting, then it must be decelerating, hence the second half-turn of the wheel or top takes more time than the first one, hence the top or wheel has more time to flop than it does to flip.

 

If the flip exceeds the flop, as it would under acceleration of the wheel, then the second half-turn of the wheel has had less time to flop than the first half-turn had to flip, and a Left Hand Rule would demonstrate the net precession.

 

Thing is, I don't see that the big kids have made any allowances for a Left Hand Rule!

Edited June 30, 2012 by Heedless