Hi Gunter, you want the Sweep command for that, not Rail revolve.

Some examples:

http://vimeo.com/30765016
http://moi3d.com/forum/index.php?webtag=MOI&msg=4623.1
http://moi3d.com/forum/index.php?webtag=MOI&msg=767.2
http://moi3d.com/forum/index.php?webtag=MOI&msg=490.36

- Michael