FrankLu的發現之旅

如果我們把BB中心想像成是支點，而曲柄想像成力臂；則我們不難發現這是一個槓桿系統。以長曲柄來說，力臂較長，想當然爾，在施力上會比較省力，尤其在爬坡的時候，騎士們可以很清楚感受到長曲柄的好處。但是相對的，長曲柄卻有一個致命缺點：它不利迴轉速。http://mkl-note.blogspot.com/2009/02/blog-post_26.html

大致的搜尋一下, 可找到如上圖的計算方式.  
曲柄的長度（單位mm）=等效腿長（單位mm）＊0.2
http://www.highpath.net/index.html


另外找到的一個算法為:
曲柄的長度（單位mm）=胯下長（單位mm）＊0.216
http://www.nettally.com/palmk/crankset.html


以我為例, 等效腿長為88cm, 跨下長為83cm.
換算得到的曲柄長約為180mm.

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找到的第三個算法是: 
曲柄的長度（單位mm) = 股骨高 （單位mm）＊0.185
One writer in a major magazine article quite a few years ago claimed that after considerable testing with many different riders, 18.5% of the distance from the top of the femur to the floor in bare feet should be the crank length. You can find the top of the femur pretty easily. It's 5" to 6" below your hip bone, and moves rearward when you raise your knee.
http://www.peterwhitecycles.com/fitting.htm

Finding the top of the femur is the hard part. Feel along the outside of your hip to find the place where your leg joins the hip. The top of the femur is slightly above the actual joint, so if you lift your leg, the top of the femur will move back slightly. Search for this movement.

以我為例, 股骨高為95cm, 換算得到的曲柄長約為175mm.


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找到的第四個算法是: http://www.naxin.why3s.com/phpbb/viewtopic.php?t=654&sid=665567d805600d454b2e7dd225fa5fa3

由五次環法冠軍,法國 保納德.興諾 這位選手的機械師所寫的書上所建議的
曲柄長度,讓大家參考一下
跨下長78公分以下,適用170mm的曲柄
跨下長78cm~84cm,適用172.5mm的曲柄
跨下長84cm~90cm,適用175mm的曲柄
跨下長90cm~95cm,適用177.5的曲柄



看起來, 照前人的經驗, 175mm左右的曲柄應最適合我吧!




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最佳的整理 : Finding your correct crank length
http://www.myra-simon.com/bike/cranks.html


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