I came across a place in Toronto called ChocoSol that was said to have a 'bicycle machine' and use them to grind chocolate in Oaxaca, Mexico. Although they used to use these machines when they started the business, the volume has grown so much so that they use electric machines to husk and grind cocoa beans now and use the bicycle for demo purposes only. Nevertheless, it was still a learning opportunity and a chance to see a working bicycle machine.
Electric assist
Grinding by hand
Tension adjustment and leather chain
vaccuum pipe filled with cement as a flywheel
bolted in
For the record, the chocolate is really tasty.