Operation

• Gears transmit power through interconnecting teeth. The output of the gears depends on how the gears interconnect. Different types of gears meshing in different ways may change the direction of travel, the amount of torque or the speed of the output gear.
  
  

Speed

• The gear ratio determines the output speed of a set of gears. The gear ratio is a comparison of the number of teeth on the output gear to the number of teeth on the input gear. Connecting output gears with fewer teeth to input gears with more teeth increases the speed of the output gear. This is because the output gear, with fewer teeth is forced to make more revolutions than the input gear that drives it.
  
  

Other Factors

• In a typical two-gear system pair, the output gear travels in the opposite direction of the input gear. However, gears often are arranged in complex groups that change direction along different axes, or in configurations where the output gear must travel in the same direction as the input gear. An idler gear often must be used in some of these applications. Idler gears reside between the input and output gears, but they do not affect the speed of an output gear.