Science Fair Project Encyclopedia
Steering is the term applied to the collection of components, linkages, etc. which allow for a car or other vehicle to follow a course determined by its driver, except in the case of rail transport in which rail tracks combined together with railroad switches provide the steering function.
The most conventional steering arrangement is to turn the front wheels using a hand–operated steering wheel which is positioned in front of the driver. Other arrangements are sometimes found on different types of vehicles, for example, a tiller or rear–wheel steering. Tracked vehicles such as tanks usually employ differential steering—that is, the tracks are made to move at different speeds or even in opposite directions to bring about a change of course.
Rack and pinion
Most modern cars use rack and pinion steering mechanisms. Older designs often use the recirculating ball mechanism, which is still found on trucks and utility vehicles. In a rack and pinion design, the steering wheel turns the pinion via the steering column which may use universal joints. The rack moves from side to side and applies torque to the kingpins of the steered wheels via tie rods and a short lever called the steering arm. Ackermann steering geometry is commonly used to allow each wheel to trace the correct path while travelling in a curve.
Four wheel steering
Recently, four wheel steering has been offered in trucks with four wheel drive used for towing. All four wheels turn at the same time when you steer. There are controls to switch off the rear steer and options to steer only the rear wheel independent of the front wheels. At slow speeds the rear wheels turn opposite of the front wheels and at high speeds both front and rear wheels turn alike (electronically controlled). The turning radius in four wheel steering systems is reduced by up to twenty-five percent. The "Snaking effect" experienced during motorway drives while towing a caravan is largely nullified. Four wheel steering is popular in large farm vehicles and trucks.
General Motors offers Delphi's Quadrasteer in their consumer Silverado/Sierra and Suburban/Yukon. However, only 16,500 vehicles have been sold with this system since its introduction in 2002 through 2004. Due to this low demand, GM will not offer the technology on the 2007 update to these vehicles.
Articulated steering is a system by which a four wheel drive vehicle is split into front and rear halves which are connected by a vertical hinge. The front and rear halves are connected with one or more hydraulic cylinders that change the angle between the halves, including the front and rear axles and wheels, thus steering the vehicle. This system does not use steering arms, king pins, tie rods, etc. as does four wheel steering.
Power steering aims to make steering less strenuous for the driver. There are two types of power steering systems--hydraulic and electric/electronic. There is also a hydraulic-electric hybrid system possible.
For safety reasons all modern cars feature a collapsible steering column which will collapse in the event of a heavy frontal impact to avoid excessive injuries to the driver. This safety feature first appeared on cars built by General Motors after an extensive and very public lobbying campaign enacted by Ralph Nader.
- Steering wheel cover
- 4 wheel steering
- Caster angle
- Camber angle
- Electronic Stability Program
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