請問公路車換刀輪適合嗎?? - 公路車
By Andy
at 2014-04-18T13:57
at 2014-04-18T13:57
Table of Contents
※ 引述《WuDhar (was eliminated)》之銘言:
: 前者總能K=(1/2)mv^2(人+車)+(1/2)Iw^2(輪子轉動能)
: 後者總能K'=(1/2)mv^2(人+車)+(1/2)I'w^2(輪子轉動能)
假設對同一個騎士而言,輸出總能量K為定值
然後兩輪框重量相同,轉動慣量一個為I一個為I',其中I'>I
K = (1/2)mrw^2 + (1/2)Iw^2
= (1/2)mrw'^2 + (1/2)I'w'^2
那從式子中可以知道w會大於w'
意思就是總能量相同下,我前者速度大於後者,早騎更遠了
所以幹嘛沒事用轉動慣量大的輪組只為了把一部分能量存成轉動能?
高框或板輪的優勢是風阻值小,尤其在越高速下風阻力差異越大
因此高速下,從風阻得到的正效益>重量&轉動慣量的負效益
當在高速下停止踩踏
因為低風阻(主因)加上轉動慣量自然滑更遠,一般人"覺得"有好很好的慣性就是指這個
的確轉動慣量是原因之一,但轉動慣量只是前面你先存進去的動能再拿出用而已
真正的效益是"低風阻"
不論慣量(inertia)或轉動慣量(moment of inertia)根本沒帶來實際好處
所以老問題,為什麼不直接把動能換成速度就好?(也早就騎更遠不是嗎?)
PS.三鐵因為高速+巡航,自然板輪有優勢
--
: 前者總能K=(1/2)mv^2(人+車)+(1/2)Iw^2(輪子轉動能)
: 後者總能K'=(1/2)mv^2(人+車)+(1/2)I'w^2(輪子轉動能)
假設對同一個騎士而言,輸出總能量K為定值
然後兩輪框重量相同,轉動慣量一個為I一個為I',其中I'>I
K = (1/2)mrw^2 + (1/2)Iw^2
= (1/2)mrw'^2 + (1/2)I'w'^2
那從式子中可以知道w會大於w'
意思就是總能量相同下,我前者速度大於後者,早騎更遠了
所以幹嘛沒事用轉動慣量大的輪組只為了把一部分能量存成轉動能?
高框或板輪的優勢是風阻值小,尤其在越高速下風阻力差異越大
因此高速下,從風阻得到的正效益>重量&轉動慣量的負效益
當在高速下停止踩踏
因為低風阻(主因)加上轉動慣量自然滑更遠,一般人"覺得"有好很好的慣性就是指這個
的確轉動慣量是原因之一,但轉動慣量只是前面你先存進去的動能再拿出用而已
真正的效益是"低風阻"
不論慣量(inertia)或轉動慣量(moment of inertia)根本沒帶來實際好處
所以老問題,為什麼不直接把動能換成速度就好?(也早就騎更遠不是嗎?)
PS.三鐵因為高速+巡航,自然板輪有優勢
--
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公路車
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