A belt drive bicycle frame with an eccentric bottom bracket

摘要

The frame 20 comprises a tube 21 in which is mounted a bottom bracket 30 with an eccentric shaft and bearing assembly 50 with a co-rotating belt pulley and pedal cranks. The bottom bracket 30 can be adjusted angularly in the frame tube 21 for belt tensioning and/or height variation to suit a rider's leg length and fixed in position by a clamping action provided by a protruding screw 40 mounted in a radial hole 32 in the bracket 30 and movable along an arcuate slot 22 in the tube 21.