The Pi electric bicycle uses a semi-automatic 8-speed transmission to downshift into a lower gear for climbing hills, then up shift for rapid acceleration to a maximum of 20 mph on flats and allows you to pedal normally because the motor automatically disengages when not in use. Powered by a 750-watt electric motor housed in the horizontal chain and motor assembly, the Pi electric bicycle is capable of three modes of operation: electric motor power, human power, or the human-electric hybrid power combination. The electric motor and rider utilize the same 8 speed semi-automatic transmission making rapid acceleration from a stop or lower gears available for steep inclines possible (but with slower acceleration.

The motor automatically disengages from the pedals when desired so as to preserve battery life. Construction begins with a 12’ foot straight piece of 3⁄8-gauge, aircraft aluminum 6061 alloy that is roll-formed and annealed for uniform wall thickness into a complete 6′ diameter circular tube with a 4″ exterior diameter (the NiMH batteries reside within the tube from the front fork to the seat), which is then bisected to make a 6′ long arc for the bicycle’s frame. The sturdy frame supports riders up to 300 lbs. Read more at tuvie.com