Why they could ride so fast 為什麼他們能騎得那麼快?

cyclingnut · Member

Why they could ride so fast 為什麼他們能騎得那麼快?

kwyan · Veteran Member

Both. That is why we need to train hard and also need to learn how to pedal efficiently. There have been a lot of studies on this subject which is often considered as the single most difficult technique to master.

Studies include:

(1) pedalling with longer or shorter crank is more efficient?

(2) sitting more forward or backward is more efficient?

(3) pedalling a lower gear faster or pedalling a higher gear slower is more efficient?

(4) is pedalling a circle the most efficient way? (it is commonly agreed to be more efficient than pedalling square)

(5) is the body position the lower the better?

(6) is pushing (downstroke) and pulling (upstroke) at the same time better than pushing with one foot and unweighting with the other?

(7) is climbing while seated better or standing better?

(8) which ankling technique is better, toes down, heels down, toes down on downstroke (and toes up on upstroke) or heels down on downstroke (and heels up on upstroke)?

(9) is there any other technique to push oneself further (alternate the foot with harder effort)?

There seems to be no firm answer to many of the above questions yet. I will try to dig out what I have read and share with you later.

-- Edited by kwyan at 10:36, 2005-05-24

kwok kam ming · Newbie

都話有冇中文lo~!睇唔明啊

我估佢地成日都有練ga

kwyan · Veteran Member

對不起,只因中文輸入需時,會盡快...

kwyan · Veteran Member

中文版本

兩者都有。那是為什麼我們需要努力地訓練以及需要學習該如何有效率地踩踏板。在這一個踩踏板的題目上已經有許多研究並常常被當作為單一最難掌握的技術

研究的項目包括：

（1) 曲柄的長短對踩踏板的效率有何影嚮？

（2) 坐位的前後位置對踩踏板的效率有何影嚮？

（3) 快速地踩踏一個較低的齒輪比或慢慢地踩踏一個較高的齒輪比何者更有效率？

（4) 圓型的踩踏方法是否最有效率？(普遍同意比方形踩踏方法更有效率）

（5) 是否身體的位置伏得愈低則愈有效率？

（6) 是否採用一腳推時（向下行程）一腳拉（向上行程）的踩踏方法勝於一腳推時和一腳吊(減磅)的踩踏方法？

（7) 是採用坐姿還是採用站姿的爬坡方法較好？

（8) 腳踝技術比較好的方法，是足趾向下推、腳跟向下墬、向下行程時足趾向下推（和向上行程時足趾向上挑）、或是向下行程時腳跟向下墬（而向上行程時腳跟向上揚）?

（9) 有任何其他的技術可更進一步地用盡自己嗎? （用交替重腳法?）

許多上述的問題似乎仍然沒有絕對的可靠答案。我將稍後試著搜出我曾見過的論述與大家分享。

TH CHAN · Member

根據物理學兩倍速度等於四倍空氣抵抗力.同時輸出功率更為前者八倍.

空氣阻力相對速度二次方,而輸出功率是相對速度三次方關係.

功率(P) = 力(F) X 速度 (V)

-- Edited by TH CHAN at 14:11, 2005-05-29

kwyan · Veteran Member

According to the data that I have read (see http://www.coe.uky.edu/~brian/pdfs/ejap-2003.pdf) doubling the speed of cycling will not require increasing the power output as much as 8 times.

Speed Power

4 m/s (14.4kph) 23.1W (the power for riding on

cycling track, barely enough

to lit up some headlight)

8 m/s (28.8kph) 112.2W (the power for an easy ride)

12 m/s (43.2kph) 333.2 W (now I know how much

cooling I need for an

hour's ride on the trainer)

Increasing the speed from 4 m/s to 8 m/s doubles the speed, but the power output is only 4.86 times, not 8 times.

Air resistance is roughly proportional to the square of speed but the internal resistance is probably more like a linear relationship. Total resistance come from air PLUS internal resistance (hub bearing etc.) and at contact between tyres and roads, so the power output is the SUM of air resistance which is proportional to the square of speed and other resistance which is proportional to the speed, and the total is only slightly more than the square of speed.

根據資料，踩單車的兩倍速度並不需要八倍的能量輸出。

將速度由每秒四公尺提升至每秒八公尺，兩倍速度但能量輸出是4.86倍而已，衹是稍高於四倍。

空氣阻力相對速度二次方，但其他阻力如輪軸的軸承等，相對速度一次方，而總輸出功率是空氣阻力和其他阻力的總和，故衹是稍高於速度二次方而小於速度三次方。

TH CHAN · Member

單車行使時主要阻力是滾動阻力+空氣阻力.在底速行車時滾動阻力佔總阻力比例較高,

但高速行車時空氣阻力佔總阻力比例會相對題高,例如將速度由每秒六公尺提升至每秒十二公尺,

兩倍速度但能量輸出已是六倍多,速度越高空氣阻力佔總阻力比例越大,就越接近理論所示.

TH CHAN · Member

-- Edited by TH CHAN at 15:37, 2005-06-02

TH CHAN · Member

RE: Engineering of cyclist

kwyan · Veteran Member

RE: Why they could ride so fast 為什麼他們能騎得那麼快?