Recirculating ball, also known as recirculating ball and nut or worm and sector, is a steering

Steering

Steering is the term applied to the collection of components, linkages, etc. which will allow a vessel or vehicle to follow the desired course...

 mechanism commonly found in older automobiles

Automobile

An automobile, autocar, motor car or car is a wheeled motor vehicle used for transporting passengers, which also carries its own engine or motor...

, and some trucks

Truck

A truck or lorry is a motor vehicle designed to transport cargo. Trucks vary greatly in size, power, and configuration, with the smallest being mechanically similar to an automobile...

. Most newer cars use the more economical rack and pinion

Rack and pinion

A rack and pinion is a type of linear actuator that comprises a pair of gears which convert rotational motion into linear motion. A circular gear called "the pinion" engages teeth on a linear "gear" bar called "the rack"; rotational motion applied to the pinion causes the rack to move, thereby...

 steering instead, but some significant manufacturers (including Chrysler

Chrysler

Chrysler Group LLC is a multinational automaker headquartered in Auburn Hills, Michigan, USA. Chrysler was first organized as the Chrysler Corporation in 1925....

 and General Motors

General Motors

General Motors Company , commonly known as GM, formerly incorporated as General Motors Corporation, is an American multinational automotive corporation headquartered in Detroit, Michigan and the world's second-largest automaker in 2010...

) still use this technology in some models; e.g., the Jeep Wrangler

Jeep Wrangler

The Jeep Wrangler is a subcompact four-wheel drive sport utility vehicle and an off-road vehicle manufactured by American automaker Chrysler, under its Jeep marque – and now in its fourth generation. It is a successor to the famous World War II 'Jeep' vehicle by way of the Willys civilian...

 and the Crossfire

Chrysler Crossfire

The Chrysler Crossfire is a rear-wheel drive sports car marketed by Chrysler as both coupé and roadster and was built for Chrysler by Karmann of Germany.-Design:...

 for the durability and strength inherent in the design.

Mechanism

The recirculating ball steering mechanism contains a worm gear inside a block with a threaded hole in it; this block has gear teeth cut into the outside to engage the sector shaft (also called a sector gear) which moves the Pitman arm

Pitman arm

The Pitman arm is a steering component in an automobile or truck.The Pitman arm is a linkage attached to the steering gear sector shaft, that converts the angular motion of the sector shaft into the linear motion needed to steer the wheels. The Pitman arm is supported by the sector shaft and...

. The steering wheel connects to a shaft, which rotates the worm gear inside of the block. Instead of twisting further into the block, the worm gear is fixed so that when it spins, it moves the block, which transmits the motion through the gear to the pitman arm, causing the roadwheels

Wheel

A wheel is a device that allows heavy objects to be moved easily through rotating on an axle through its center, facilitating movement or transportation while supporting a load, or performing labor in machines. Common examples found in transport applications. A wheel, together with an axle,...

 to turn.

Bearing balls

The worm gear is similar in design to a ball screw

Ball screw

A ball screw is a mechanical linear actuator that translates rotational motion to linear motion with little friction. A threaded shaft provides a helical raceway for ball bearings which act as a precision screw. As well as being able to apply or withstand high thrust loads, they can do so with...

; the threads are filled with ball bearings that recirculate through the gear and rack as it turns. The balls serve to reduce friction and wear in the gear, and reduce slop. Slop, when the gears come out of contact with each other, would be felt when changing the direction of the steering wheel, causing the wheel to feel loose.

Power assistance

Power steering

Power steering

Power steering helps drivers steer vehicles by augmenting steering effort of the steering wheel.Hydraulic or electric actuators add controlled energy to the steering mechanism, so the driver needs to provide only modest effort regardless of conditions. Power steering helps considerably when a...

 in a recirculating-ball system works similarly to that in a rack-and-pinion system. Assistance is provided by supplying higher-pressure fluid to one side of the block.

See also

• Jorgen Automotive Corporation
• Burman and Sons Ltd
  Burman and Sons Ltd
  Burman and Sons Ltd, of Ryland Road, Birmingham, England, manufactured Burman-Douglas steering gear.Their recirculating worm and ball design of steering gear was fitted to pre-war vehicles such as the Ford Eight and the Ford Prefect, the Bedford CA, plus many other vehicles - both pre and post-war....
  
  - defunct manufacturer of recirculating ball steering gear