From: donald gillies <gillies@ece.ubc.ca>
"This would be rather hard to do. Here is the cog diagram for suntour freewheels (I snagged this from an ebay auction a few years ago) :
http://www.ece.ubc.ca/
If it helps, I've got a higher resolution copy of this SunTour drawing on my Flickr page:
http://farm4.static.flickr.com/
SunTour gets credit for designing a freewheel system that would let you build almost any freewheel imaginable, but it required an amazing variety of spacers and cog variations. Converting an existing freewheel from standard to ultra spacing could be quite a challenge!
Thanks to Rob Hawk of the I-bob list for providing the SunTour drawing to me.
regards,
Steve Kurt
Peoria, IL USA