Dave McGuire wrote:
    It's called "crowning" here too.  How in blazes does that work?
 I've always wondered about it. 
FWIW, this shows up with a search for "pulley crowning":
  
http://www.lhup.edu/~dsimanek/scenario/crowning.htm
(click thru to the answer page). It looks familiar, I think somebody else
pointed to the same page during a previous discussion of this topic on the list.