Rack and Pinion: Definition and Application

What is Rack and Pinion?

A rack and pinion is a type of linear actuator that comprises a circular gear (the pinion) engaging a linear gear (the rack), which operates to translate rotational motion into linear motion. A rack and pinion drive can use both straight and helical gears.

Driving the pinion into rotation causes the rack to be driven linearly. Driving the rack linearly will cause the pinion to be driven into a rotation.

Helical gears are preferred due to their quieter operation and higher load-bearing capacity. The maximum force that can be transmitted in a rack and pinion mechanism is determined by the tooth pitch and the size of the pinion.

For example, in a rack railway, the rotation of a pinion mounted on a locomotive or railroad car engages a rack between the rails and helps move the train up a steep incline.

There is a base rack for every pair of conjugate involute profiles. This base rack is the profile of the conjugate gear with an infinite pitch radius. A generation rack is a rack outline used to indicate tooth details and dimensions for the construction of a generation tool, such as a hob or gear mill.

Application of rack and pinion

A rack and pinion are commonly found in the steering mechanism of cars or other wheeled, steered vehicles. Rack and pinion provide less mechanical advantage than other mechanisms such as recirculating ball, but less backlash and greater feedback, or steering “feel”.

Here are just a few of the common modern applications that regularly utilize rack and pinion gearsets:

  • Car steering: The system works by converting a revolving motion into linear motion. Most cars, small trucks, and SUVs come equipped with a rack and pinion system, rather than the recirculating ball steering found in larger trucks, larger SUVs, and other heavy-duty vehicles.
  • Railways: Rack railways are mountain railways that use a rack built into the center of the track and a pinion on their locomotives. This allows them to work on steep gradients, up to 45 degrees, as opposed to conventional railways which rely on friction alone for locomotion. Additionally, the rack and pinion addition provides these trains with controlled brakes and reduces the effects of snow or ice on the rails.
  • Stairlifts: Virtually all stairlifts contain a rack and pinion gear, with the gear allowing for upward movement in similar ways as above.
  • Actuators: Actuators are machines that move various components, such as a pipeline transport system. In such a system, a rack and pinion gear help control the valves that the system requires for basic functioning.

FAQs.

What is Rack and Pinion?

A rack and pinion is a type of linear actuator that comprises a circular gear (the pinion) engaging a linear gear (the rack), which operates to translate rotational motion into linear motion. A rack and pinion drive can use both straight and helical gears.

What are the application of Rack and pinion?

A rack and pinion is commonly found in the steering mechanism of cars or other wheeled, steered vehicles. Rack and pinion provides less mechanical advantage than other mechanisms such as recirculating ball, but less backlash and greater feedback, or steering “feel”.

How many teeth rack and pinion?

Empirically, a pinion with approximately 20 teeth is optimal. That is why Apex Dynamics has invented the “Curvic Plate” pinion, in which the torque, backlash, wear and service possibilities are optimal.

What is difference between pinion and gear?

Pinion Gear – A pinion is the smaller of two meshed gears in an assembly. Pinions can be either spur or helical type gears, and be either the driving or driven gear, depending on the application. Pinion gears are used in many different types of gearing systems such as ring and pinion or rack and pinion systems.