利用把手輸入一端轉速，藉由半徑的變化，因輸出端滾輪的高度需與輸入端接觸點相同，而造成輸出端的高度有往復式的高低變化。

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Input rotation by handle, with the variation in cam radius, due to that the roller is level with the input contact point, the output is a reciprocating motion of the roller.