| 摘要 |
A power transmission system for a wheeled personal transportation device such as a bicycle comprises a sequence of at least three operably interconnected sets of gearwheels, a first set in the sequence for receiving rotational force and a last set in the sequence for transmitting rotational force for a driven wheel of the device. The first set and the last set each comprise user-selectable gearwheels. At least one intermediate set in the sequence comprises an input gearwheel subset and an output gearwheel subset, at least one of the input gearwheel subset and the output gearwheel subset comprising a plurality of user-selectable gearwheels. A frame for a personal transportation device comprises a base and a steering shaft on the base for supporting a steering column. Crank connection means are provided on the base for operably receiving a crank/pedal combination and an associated first set of user-selectable gearwheels. An upper-rearward extension extends from a rear of the base for operably receiving a second set of gearwheels comprising an input gearwheel subset and an output gearwheel subset. At least one of the input gearwheel subset and the output gearwheel subset comprise a plurality of user-selectable gearwheels. The frame further comprises a subextension associated with the upper-rearward extension for supporting a gearwheel-change mechanism associated with a respective one of the output gearwheel subset and the input gearwheel subset; and a lower-rearward extension extending from the rear of the base for supporting the driven wheel and a rotatable third set of gearwheels.
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