Components

• The two components of a rack and pinion gear are the rack--the flat, toothed component--and the pinion, which is a standard round gear. The teeth on both gears are wedged and angled to allow them to mesh together.
  
  

Transferring Motion

• As with any gear system, the two gears are positioned so the teeth interleave. As the pinion teeth mesh with the rack teeth, pressure is applied and the rack moves. The diameter of the pinion determines how far the rack will move with each turn of the gear.
  
  

Examples

• Two examples of where rack and pinion gears are found are trains and automobiles. Train wheels are smooth steel, which does not provide much grip when climbing steep hills. Some train systems are equipped with rack and pinion gearing. The pinion gear is lowered as the train approaches the hill, meshing with the rack and preventing the train from slipping down the hill. Racks and pinions are also found in automobiles where the pinion is used to transfer the radial motion of the steering wheel to turn the wheels.