ABSTRACT
Gears were invented many centuries ago and have been widely used since that time [1]. Historically, the development of gear design dovetailed with the development and design of other mechanisms and mechanical components. This applied design approach could also be called direct design because a shape (geometry) of a part was directly defined only by its function and performance requirements. Ancient engineers were designing custom gears (Figure 1.1) for particular applications based on the knowledge of desired performance (input and output parameters) and available power sources, such as gravity, water current, wind, spring force, human or animal muscular power, etc. This knowledge allowed them to define gear arrangement and geometry, including a number of stages, location and rotation directions of input and output shafts, shape and size of the gear wheels, profile and number of teeth, and other parameters. Gear design also included material selection, which should provide the required strength and durability of every component in the gear drive.
