Model: N07 Internal Ratchet Coupling
Ratchet mechanisms are like electric diodes, permitting motion in one direction but not the other. In this ratchet mechanism, the rotary motion about two coupled axes are enabled for relative motion in one direction, but the clutch slips for relative motion in the other direction. Reuleaux attributes the design of this particular mechanism to a person named Wilbers who used it in a lawn mower machine. Unlike N-1 where the pawls ride on the outside diameter of the saw-toothed wheel, in N-9 the three pawls engage the teeth on the inside diameter of the circular ring.

Reuleaux was intrigued with the kinematics of ratchet gearing and wrote at considerable length about them in his two major works (see References). Leonardo da Vinci also sketched many ratchet mechanisms. See e.g. The Codex Madrid I drawings on line.

Francis Moon 2004-07-00

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