Abstract
Except providing the basic functions of up-shift and down-shift, the smoothness of chain shifting process is more critical in designing the freewheel. The reaction force from the pedal determines how smooth the rider feels during the gear shifting process. The smoothness is therefore an important factor when designing a freewheel. This study proposed a generalized method for trimming the sprocket in accordance with the designed nonlinear paths. In this method, the common shifting characteristics were observed based on the various combinations of chain parameters and the number of tooth. The gear shifting process were divided into six modes which were verified by computer simulation and experiment. The variation of the length of free chain was thus selected as the smoothness index for designing the freewheel. According to the proposed generalized method, a prototype of freewheel was designed and manufactured by using the CAD/CAM softwares and CNC machine. The result of the experiment verified the feasibility of the method developed in this study.