Mathematical Model and Verification for the Stable Region of a Bicycle Rear Derailleur System

• Main Authors: Ueng, Yang-Shyh, 翁央士
• Other Authors: Sung, Cheng-Kuo
• Format: Others
• Language: zh-TW
• Published: 1996
• Online Access: http://ndltd.ncl.edu.tw/handle/63130767008678970754

碩士 === 國立清華大學 === 動力機械學系 === 84 === The rear derailleur system of a multi-speed bicycle consists of a freewheel, a derailleur system, chain, and shift level. Because of the distinctive performance, the index shift levels have been very popular. This thesis proposed a concept of "stable region" that is physically existence and can be used for determining the traveling distance of the shift level to guarantee a smooth up- and down-shifting characteristic. Beginning with the definition of the stable region as a range of cable displacement, a mathematical model for the stable region was created according to the contact conditions among the chain, guide pulley, and freewheel. On the basis of this model, the stable region of an existing rear derailleur system was found numerically. For the sake of verifying the validity of the mathematical model, an equipment for measuring the stable region of a certain type of derailleur was constructed for the comparison between the theoretical and experimental results. By analyzing the characteristics of the stable region, a modified design was made for the existing rear derailleur system. According to the test results, the modified design illustrated a remarkable improvement for the shifting performance.