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
EDITED: 4 Dec 2006 by PILOU
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