What Is a Crown & Pinion Gear Used For?

By Sasha Rousseau ; Updated April 12, 2017
The pinion and rack system is useful in machines in which the steering mechanism is perpendicular to the wheels, such as in cars.

A pinion gear is used to steer against the force of gravity. The crown, also called a pinion, is a wheel with cogs or teeth along its rim. A rack is a straight piece that also has cogs or teeth. The pinion’s cogs interlock with those of the rack, so as the pinion rolls, it rolls along the rack. The pinion and rack’s interlocking clogs allow the pinion to roll along the rack even in circumstances in which it has to roll uphill or sideways.

Trains on an Uphill Track

Trains that must travel uphill may use crown wheels instead of smooth wheels and the track the train must travel up may be a pinion. Gravity pulls the train downhill and if the train wheels weren’t able to interlock with the track –- for example, if they were smooth –- the train would be likely to roll downward. Switzerland’s mountainous landscape requires that many of its railways use a crown and pinion gear system.

Car Steering Wheel

In a car’s rack and pinion steering system, the pinion is a round column with teeth running along its shaft. The pinion interlocks and runs along the rack at 90 degrees –- a collar holds it in place. The pinion connects with the steering column so when the steering wheel is turned, the pinion runs in the opposite direction. As the pinion runs along the rack in that direction, the rack moves under it in the opposite direction, which turns the wheels in the direction the driver is turning. The rack and pinion system is the most common steering equipment in cars at present.

Locking Doors on a Track

Rack and pinion systems are useful for doors or cutting mechanisms that must stay on a precise track. For example, the doors on many prison cells run on a rack and pinion system so they can’t easily be pushed out. Placing an industrial cutting mechanism along a rack and pinion gear system is a safety measure because the interlocking gear ensures the pinion will be locked into traveling along a precise track.

Roller Coasters

Roller coaster cars run on rails when they are right-side-up, but in order to safely spin a roller coaster car, a four-track system is used. The car’s bottom wheels continue to run on the roller coaster’s rails but a crown and pinion gear system is used for spin control. As the car tilts into a spin, the crown wheels on the side of the car connect with the pinion running on that part of the roller coaster to direct and control the spin.

About the Author

Sasha Rousseau began writing in 2003. She won the best fiction award from "Thoroughfare Literary Magazine," placed in the Sir Martin Gilbert Churchill National Essay Competition and has been published in the "Washington Post." She graduated magna cum laude with a Bachelor of Arts in writing seminars and English from Johns Hopkins University.