Drivetrain
 

Each set of pedals can be shifted independently. The crank sprocket for each pedal set drives a rear bicycle free-wheel so the pedals can "coast". A #40 sprocket has been added to the side opposite the bike sprockets. This #40 sprocket connects all four pedal sets to a single "collector" 1-inch diameter shaft. This central shaft connects to a second interim shaft. The centerline of the interim shaft is aligned with the pivot points of the trailing arms that connect the rear axle to the sides of the frame. This alignment allows the chain tension to remain constant as the rear axle moves up and down. The chain connection between the interim shaft and rear axle is also located at the center of the axle to minimize chain movement as the rear axle twists. The rear axle is split so that the rear wheels can travel at different speeds during turns. Drive is through the left rear wheel while the right wheel spins free.
 
An unfortunate result of the design process was increased drivetrain drag. A final frame design was created and then the drivetrain was routed around the frame utilizing the first collector shaft. Eliminating either the collector or interim shaft would have helped. The tensioners for each length of chain are set as loose as is practical to help lessen the drag. The tensioner for the final axle connection needed to be placed so there was nearly 270° of chain wrap on the rear sprocket. Without that placement the chain skipped a tooth under heavy loads.

Seats & Drivetrain Install:
 

June & July 2008