be a simpler alternative to other overload-protection devices such as clutches and torque-limited or current-limited motors.

In spite of the advantages of metal and plastic, wood continued to be used for large gears until a couple of centuries ago because of cost, weight, tradition, or other considerations. In 1967 the Thompson Manufacturing Company of Lancaster, New Hampshire still had a very active business in supplying tens of thousands of maple gear teeth per year, mostly for use