Unsourced material may be challenged and removed. The primary purpose of the steering system is to allow the driver to guide the vehicle. File:Curves, described by a types of steering mechanism pdf moving vehicle.
Curves described by the rear wheels of a conventional automobile. While the vehicle moves with a constant speed its inner and outer rear wheels do not. The basic aim of steering is to ensure that the wheels are pointing in the desired directions. This is typically achieved by a series of linkages, rods, pivots and gears. The rack and pinion design has the advantages of a large degree of feedback and direct steering “feel”. 1930s, and many other European manufacturers adopted the technology.
The steering column turns a large screw which meshes with nut by recirculating balls. This design is still in use in trucks and other large vehicles, where rapidity of steering and direct feel are less important than robustness, maintainability, and mechanical advantage. To reduce friction the sector is replaced by a roller or rotating pins on the rocker shaft arm. Generally, older vehicles use the recirculating ball mechanism, and only newer vehicles use rack-and-pinion steering. This division is not very strict, however, and rack-and-pinion steering systems can be found on British sports cars of the mid-1950s, and some German carmakers did not give up recirculating ball technology until the early 1990s. Other systems for steering exist, but are uncommon on road vehicles. Power steering helps the driver of a vehicle to steer by directing some of its power to assist in swiveling the steered road wheels about their steering axes.
A hydraulic-electric hybrid system is also possible. In EPS, the amount of assistance is easily tunable to the vehicle type, road speed, and even driver preference. An added benefit is the elimination of environmental hazard posed by leakage and disposal of hydraulic power steering fluid. In addition, electrical assistance is not lost when the engine fails or stalls, whereas hydraulic assistance stops working if the engine stops, making the steering doubly heavy as the driver must now turn not only the very heavy steering—without any help—but also the power-assistance system itself.
An outgrowth of power steering is speed sensitive steering, where the steering is heavily assisted at low speed and lightly assisted at high speed. Auto makers perceive that motorists might need to make large steering inputs while manoeuvering for parking, but not while traveling at high speed. Modern speed-sensitive power steering systems reduce the mechanical or electrical assistance as the vehicle speed increases, giving a more direct feel. This feature is gradually becoming more common.
Early example of four-wheel steering. 1937 Mercedes-Benz Type G 5 with four-wheel steering. In most active four-wheel steering systems, the rear wheels are steered by a computer and actuators. The rear wheels generally cannot turn as far as the front wheels. There can be controls to switch off the rear steer and options to steer only the rear wheels independently of the front wheels. Some of the modern European Intercity buses also utilize four-wheel steering to assist maneuverability in bus terminals, and also to improve road stability. The first rally vehicle to use the technology was the Peugeot 405 Turbo 16.
Its debut was at the 1988 Pikes Peak International Hill Climb, where it set a record breaking time of 10:47. However, only 16,500 vehicles were sold with this system from its introduction in 2002 through 2004. Due to this low demand, GM discontinued the technology at the end of the 2005 model year. Crab steering is a special type of active four-wheel steering. It operates by steering all wheels in the same direction and at the same angle.