rack and pinion

Rack and pinion animation

A Rack and Pinion is a pair of gears which convert rotational motion into linear motion. The circular pinion engages teeth on a flat bar - the rack. Rotational motion applied to the pinion will cause the rack to move to the side, up to the limit of its travel.

Alternatively the rotation of a pinion mounted on a locomotive or a railcar will engage a rack between the rails and pull a train along a steep slope.

The rack and pinion arrangement in vehicle steering is commonly found in the steering mechanism of cars or other wheeled, steered vehicles. This arrangement provides a lesser mechanical advantage than other mechanisms such as recirculating ball, but much less backlash and greater feedback, or steering "feel". The use of a variable rack was invented by Arthur E Bishop^[1] , so as to improve vehicle response and steering "feel" on-centre, and that has been fitted to many new vehicles, such as the 2008 Honda Accord, after he created a hot forging process to manufacture the racks, thus eliminating any subsequent need to machine the form of the gear teeth.

Enclosed steering rack in an automobile

For every pair of conjugate involute profile, there is a basic rack. This basic rack is the profile of the conjugate gear of infinite pitch radius.^[2]

A generating rack is a rack outline used to indicate tooth details and dimensions for the design of a generating tool, such as a hob or a gear shaper cutter.^[2]

For rack and pinion railways see Rack and pinion railway.

References

Gears
Gear systems	Spur gear systems • Worm gear • Rack and pinion • Epicyclic (planetary) gearing • Harmonic drive • Cycloidal drive • Non-circular gear
Gear shapes	Straight cut gear • Bevel gear • Helical gear • Hypoid gear
Geartooth profiles	Involute • Cycloid
Gear mechanics	Transmission • Differential • Gear coupling • Gear train • Bicycle gearing • Continuously variable transmission • Offset (gears)
See also	Ball screw • Leadscrew • Jackscrew • Belt drive • Chain drive • Gear manufacturing

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