一種能改變鏈輪與飛輪速比的腳踏車.它的結構與輕便腳踏車基本相同，所不同的是在後軸上裝有變速機構.變速機構分外變速和內變速兩種.內變速腳踏車採用內三飛變速後軸，有快速、中速和慢速三檔.變速動作是通過控制手控三級定位變速裝置（前、中、後三檔）來實現.外變速腳踏車採用多齒輪片的外五飛（１５、１７、２０、２４、２８牙飛輪片）與雙層結構的雙鏈輪（５２、４８牙鏈輪片），通過手控無級定位變速裝置達到改變傳動速比的作用.變速車的特點是可以根據不同的騎行條件而選擇相應的速度.騎腳踏車時最好能保持車速均勻，兩腳蹬踏力及頻率比較一致.實驗證明，人們在騎車時，因受腿部肌肉收縮快慢的約束，一般兩腿的迴轉頻率，保持在每分鐘６０—７０次，但在騎車時掌握此頻率確非容易，因往往受坡道、彎路、風力、風向等因素的不斷變化及各種路面的影響，為此，騎車者就得不斷改變雙腳的蹬力，使之保持某種速度.在腳踏車上安裝變速機件，使車輛在上坡等需要增加蹬力時能增大力矩，在平坦路面上或順風等適宜增速時能調整速比，使之加速.這是變速車的主要優點.使用變速腳踏車，以減少騎行時疲勞感的奧秘，就在於人們充分利用了能量變換的特性.變速車還能改善長途騎行中的枯燥乏味感，提高人們騎車時的興趣.Can change the speed ratio of a bicycle sprocket and the flywheel. Its structure is basically the same bike with the light, the difference is that in the post-axis with speed change mechanism. Exceptionally variable speed change mechanism and the two kinds of internal gear. Within the variable-speed bicycle use within the three flying speed rear axle, with fast, medium speed and slow third gear. variable-speed motion through a three position manual shift control device (before, during and after third gear) to achieve. outside the multi-speed bike gear film outside the 5-fei (15,17,20,24,28 tooth flywheel-chip) and the two-tier structure of the double-sprocket (52,48 tooth sprocket film), through manual stepless speed changing device to change the location of the role of the transmission speed ratio. is characterized by speed, according to different riding conditions to select the appropriate speed. riding a bike is best able to maintain uniform speed, feet Diego more consistent strength and frequency. experiments show that people cycling, due to leg muscle contraction speed constraints, the general legs of the rotary frequency, remain at 60-70 times per minute, but in cycling to capitalize on this frequency is certainly not easy, because often by the ramps, detours, wind, wind direction and other factors changing and various surface effects, for which cyclists have to constantly change the feet of the pedal force, so to maintain a certain speed. to install variable speed bicycle parts for vehicles such as the need to increase pedal uphill when power increased torque, in the flat road or other suitable growth rate when the wind speed ratio can be adjusted so as to accelerate. This is the main advantage of variable-speed cars. the use of variable-speed bicycle, in order to reduce fatigue when riding the mystery lies in the people's full use of the energy conversion features. transmission cars can also improve the long-distance ride in the boring sense, enhance people's interest in cycling.
