I've built a few. My family ran a little bike pedaled smoothy biz briefly. Sweetpedals.com 

I use a standard rack, with a front hub, connected to a roller skate wheel. I use Oster brand blenders, don't think that part matters but I got several from the 70's for cheap. The thing for us is that we needed to have multiple blender canister that fit the base.

I'll try to attach some pictures. 

Let me know if I can answer any thing. 

Much love from Philly

Ry