Posted by Art Hovey on April 07, 2001 at 18:59:18:
Arbor Scientific sells "happy" and "unhappy" balls that look alike but one bounces like a superball and the other does not bounce at all. The latter is made of a material called "norsorex". It occurred to me that the stuff might make good valve bumpers, but I wonder if it would be affected by valve oil. Anybody out there know anything about it?