Therefore, the mechanism that the accelerating theory of pushing depends on speedchange is not the sole condition of the weight's acceleration forward.
因此，单纯从获得速度改变量大小的角度来推断蹬冰加速的机制，并不是重心沿前进方向加速的唯一条件。
2
CAM mechanism with variable inputting speed, its driving force will change along with the profile of CAM, thus make the design of CAM mechanism becomes a difficult problem.
变速输入的凸轮机构，驱动力随凸轮廓线而变化，使得凸轮机构的设计成为一个难题。
3
In 1817, another British Roberts adopted with round 4 wheel mechanism and back to change spindle speed.