利用一組四連桿(crank-rocker)來產生往復的動作，並用一勾爪來操控棘輪，使棘輪單方向步進，勾爪是利用重力來自動歸位，左上方金黃色的旋鈕，可以用來控制棘輪步進的距離。

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A crank and rocker 4-bar linkage produces a reciprocating motion with a hook that operates the ratchet. The hook resets by gravity. The yellow button controls the length of each stroke