Rear Drive
The Rear Drive mounts to the "non-drive side" of the bicycle to allow the user to freely pedal the bike
The bike's disc rotor mounts are used to mount the Rear Drive to the rear wheel
6 spokes bend around the brake caliper, and mount the rear sprocket
Taking existing geometry from the bike, and creating the geometry of the spokes proved to be a challenge, but after 2 3D printed prototype iterations, the spokes fit between the brake caliper and the bike spokes.
Spoke FEA Study
The spokes are long and thin, and need to be strong enough to support the large loads from the motor
Using specs from the motor manufacturers website, FEA analysis shows that the spoke will not fail under the motor's maximum torque (59 N-m)
Rear Drive Prototypes
"Rotor Mount Left" Uses the 6 bolt disc brake mounts, and protrudes through the rotor
The spoke attaches to "Rotor Mount Right" on the inner side of the rotor
There is about 0.3 inches between the brake caliper and the bike spokes, the "Spoke" must fit between these constraints
The 120T rear sprocket will be mounted to 6 of these Spokes, and a #25 chain will connect the "Front Drive" to the "Rear Drive"