Help with Rotating Weighted Ball in Socket: Design Rules Needed

[john winslow]

Please can you help with the following.

If a ball which is bias weighted at a point on its circumference is enclosed in a socket which is few thousandths of an inch bigger in diameter than the ball will the weighted bias cause the ball to rotate as the socket is turned in the opposite direction or will the ball simply turn with the rotation of the socket in the same direction. I guess it has a lot to do with friction, weight bias etc. Can anyone help with any design rules for this.
Many thanks in advance.
John

 

[pallidin]

Originally posted by john winslow
Please can you help with the following.

If a ball which is bias weighted at a point on its circumference is enclosed in a socket which is few thousandths of an inch bigger in diameter than the ball will the weighted bias cause the ball to rotate as the socket is turned in the opposite direction or will the ball simply turn with the rotation of the socket in the same direction. I guess it has a lot to do with friction, weight bias etc. Can anyone help with any design rules for this.
Many thanks in advance.
John

The circumferential bias weight of the ball will cause that ball to be in asymetric contact with the spherical container. Also, The bias weight will tend towards a stable position such that it is the closest point on the ball to the center of the earth.
That point of contact will have the greatest resitance to movement, as it will have 1) the most contact with the container, and 2) will "fight" displacement due to its gravitational attraction towards the center of the earth.
Given such, what will happen is that a turn of the container will cause the ball to turn with it for a very short distance due to friction, and then the ball will rotate back to its "stable" orientation.