Slide this page :)
http://206.145.80.239/zbc/showthread.php?t=38585&page=4&pp=15
The helicoide can maybe gives you some ideas :)

You can also see that :) http://www.mathematische-basteleien.de/spiral.htm

And Michael himself made this : http://moi3d.com/forum/index.php?webtag=MOI&msg=80.2