| 摘要 |
A bicycle is provided with an automatically variable gear ratio drive by employing a frame having a bifurcated truss rotatably supporting an axle for the rear wheel, this axle being fixed to the rear wheel for rotation therewith. A pedal assembly is positioned intermediate the wheels with a one-way clutch on the pedal assembly and a pulley is mounted on the rear wheel axle, this pulley being constituted by two laterally separated segments which are laterally moveable on the axle. A belt or chain interconnects the pedal assembly with the pulley, and an idler maintains tension on the belt or chain. The inner sides of the pulley segments are sloped and the outer side portions of the belt or chain are shaped to mate with these sloping sides so that tension on the belt or chain will cause it to move inwardly on the pulley to increase the gear ratio. Centrifugal means are provided to rotate with the axle to increase the spacing between the pulley segments with increasing bicycle speed, and this increases the gear ratio. Spring means are associated with the axle to bias the pulley segments together and thus decrease the gear ratio as the bicycle speed decreases. Means are also provided for adjusting the tension on the spring means so that the rider can vary the relationship between gear ratio and velocity to suit himself, and a second spring means which is cable adjusted is provided so that the rider can alter the gear ratio when he wishes. Lastly, means are provided for delaying the centrifugal action to facilitate starting the bicycle.
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