VK3CKC's eLecTricks Trike Design and Build.

Feb 20, 2013
Axedale, Victoria, Australia
Following on from my July 1st, 2020 post:

You might recall that I had no access to a workshop and had started making a mid-drive using a bottom bracket to have an output sprocket at each end and a cassette on the right end to take chain drive from the pedals. It had to be possible to disassemble the module for maintenance.

Simply put, the left and right output sprockets are made from two 28t chainrings and chainring spiders. The left one is secured to the left spindle square taper with what was the left pedal arm securing bolt. The right side, although made the same way, is part of an assembly which includes the cassette.

These are the components of the mid-drive.

The axle was removed from a rear wheel hub and the ball bearings discarded. The hub was then modified (butchered?) by cutting it just inside the right side spoke flange, releasing the spoke flange and cassette mounting. A little attention with a file and the spoke flange fitted over the previously ground down pedal arm remains with the hub bearing cup pressing against the bottom bracket spindle end. This made it possible to secure it to the spindle with the original chainring securing bolt tightened against the hub bearing cup.

The assembled mid-drive. Some of the bolts are missing and will be installed with the final fitting.

A spacer (blue) was made to fill the gap between the chainring spider and the spoke flange. Bolts through the spoke flange, spacer, and chainring spider secure them together, allowing the driven cassette to turn the bottom bracket spindle to provide drive to the rear wheels. Mounting the completed mid-drive will be easy but the rear axles will be a little more difficult.