請問公路車換刀輪適合嗎?? - 單車

By Edward Lewis
at 2014-04-18T21:07
at 2014-04-18T21:07
Table of Contents
※ 引述《chandler0227 (錢德勒)》之銘言:
: ※ 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
我文中也有提到了本來就要先多付出些能量
而轉成轉動能會得到「易維持速度」的buff效益
「只要沒有狀況」,就像先定存再持續收利息
所以說長途(收一段時間)優勢才會出來,一煞車或紅綠燈就沒了不否認
但這也就是重輪的優劣
以本人自身練平路ITT160k,60鋁邊的輪子巡航均速比90全碳的要高
目前還無法解釋,先擱著(想用終端速度概念但暫時找不到切入點)
(講模糊一點,輪子甩不出來的感覺)
轉動元件設計問題沒有離開概念
引擎一直「常態性」的「加減速拉降轉」,當然轉動元件慣量能多小就多小
如果有一個引擎是要做成穩定性的等轉速長時間運轉,那我認為設計就會變
回到單車,
如果要儲存能量為何不是騎鋼管加車重(m)轉成動能而是要轉成輪子轉動能(I)
(事實上我ITT也故意插滿水)
我的理由是因為輪子很好換,我騎鋼管車平路可以那爬坡賽怎麼辦
但鋁邊重輪一換跑零不用烙引擎就變登山王
(目前想到另一個比喻儲能是電容,儲存電荷達到穩流效果)
簡言之,我認為慣量是好,也承認他出現優勢的條件嚴苛
--
: ※ 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
我文中也有提到了本來就要先多付出些能量
而轉成轉動能會得到「易維持速度」的buff效益
「只要沒有狀況」,就像先定存再持續收利息
所以說長途(收一段時間)優勢才會出來,一煞車或紅綠燈就沒了不否認
但這也就是重輪的優劣
以本人自身練平路ITT160k,60鋁邊的輪子巡航均速比90全碳的要高
目前還無法解釋,先擱著(想用終端速度概念但暫時找不到切入點)
(講模糊一點,輪子甩不出來的感覺)
轉動元件設計問題沒有離開概念
引擎一直「常態性」的「加減速拉降轉」,當然轉動元件慣量能多小就多小
如果有一個引擎是要做成穩定性的等轉速長時間運轉,那我認為設計就會變
回到單車,
如果要儲存能量為何不是騎鋼管加車重(m)轉成動能而是要轉成輪子轉動能(I)
(事實上我ITT也故意插滿水)
我的理由是因為輪子很好換,我騎鋼管車平路可以那爬坡賽怎麼辦
但鋁邊重輪一換跑零不用烙引擎就變登山王
(目前想到另一個比喻儲能是電容,儲存電荷達到穩流效果)
簡言之,我認為慣量是好,也承認他出現優勢的條件嚴苛
--
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