On Fri, 02 Jul 2010 18:19:18 -0700, Matty F wrote:

OK I've decided to use billiard balls for my Newton's cradle. But I
would rather not drill into the balls or try to glue things on them.
How can I hold the balls in position? This very large version has some
rings, which is what I am considering:
http://i48.tinypic.com/1euurq.jpg

hmm, one elegant approach might be a disc of metal (washers with very
large inner diameters) at each side of the ball and four rods connecting
them, forming a cage around the ball. With the right kind of metal, acorn
nuts etc. I think it could look quite interesting.