The roller diameter is the ONLY determining factor, not tire size. Took me by suprise when I started the FD thing.
This guy may have something close to your idea:Friction drive with the Predator rack mounted and if possible utilizing the S.A. IGH as the roller.
Thanks, m_mThis guy may have something close to your idea:
Project 2-speed friction drive bike start up
https://www.youtube.com/watch?v=C3gQHNGewJU
His build was documented on the other forum.
Could your 3 speed hub be incorporated into this build in the link? The original build was pure utility, but the in frame version has become a beautiful bike as well. I'm a sucker for good looking.This whole idea can be built as an in frame very easily. Remember this bike evolved into this. http://motorbicycling.com/showthread.php?t=35810