Steering

[2] Steering is achieved through various arrangements, among them ailerons for airplanes, rudders for boats, cylic tilting of rotors for helicopters,[3] and many more.

The use of a variable rack (still using a normal pinion) was invented by Arthur Ernest Bishop[4] in the 1970s, so as to improve vehicle response and aim to allow for more comfortable steering, especially at high speeds.

He also created a low cost press forging process to manufacture the racks, eliminating the need to machine the gear teeth.

Auto manufacturers in the United States began to use rack and pinion steering with the 1974 Ford Pinto.

Both types were enhanced by reducing the friction; for screw and nut it is the recirculating ball mechanism, which is still found on trucks and utility vehicles.

The nut moves a sector of a gear, causing it to rotate about its axis as the screw is turned; an arm attached to the axis of the sector moves the pitman arm, which is connected to the steering linkage and thus steers the wheels.

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.

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.

As vehicles have become heavier and switched to front-wheel drive, particularly using negative offset geometry, along with increases in tire width and diameter, the effort needed to turn the wheels about their steering axis has increased, often to the point where major physical exertion would be needed were it not for power assistance.

In EPS, the amount of assistance is easily tunable to the vehicle type, road speed, and driver preference.

An added benefit is the elimination of the 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.

[7] Modern speed-sensitive power steering systems reduce the mechanical or electrical assistance as the vehicle speed increases, giving a more direct feel.

At low speed (e.g. parking) the rear wheels turn opposite to the front wheels, reducing the turning radius, sometimes critical for large trucks, tractors, vehicles with trailers and passenger cars with a large wheelbase, while at higher speeds both front and rear wheels turn alike (electronically controlled), so that the vehicle may change position with less yaw and improved build-up of the lateral acceleration, enhancing straight-line stability.

[10][11] The "snaking effect" experienced during motorway drives while towing a travel trailer is thus largely nullified.

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, which debuted at the 1988 Pikes Peak International Hill Climb.

Renault introduced an optional all-wheel steering called '4control'[17][18][19] in 2009, at first on the Laguna GT, which is currently available on the Talisman,[18] Mégane[17] and Espace[19] vehicle lines.

Crab steering is used when the vehicle needs to proceed in a straight line but at an angle: when changing lanes on a highway at speed, when moving loads with a reach truck, or during filming with a camera dolly.

On many vehicles, when cornering, the rear wheels tend to steer slightly to the outside of a turn, which can reduce stability.

Typical methods of achieving compliance understeer are to use a Watt's link on a live rear axle, or the use of toe control bushings on a twist beam suspension.

Some suspensions typically have compliance oversteer due to geometry, such as Hotchkiss live axles, semi-trailing arm IRS, and rear twist beams, but may be mitigated by revisions to the pivot points of the leaf spring or trailing arm, or additional suspension links, or complex internal geometry of the bushings.

Articulated steering is a system by which a vehicle is split into front and rear halves which are connected by a vertical hinge.

A few types of vehicle use only rear-wheel steering, notably fork lift trucks, camera dollies, early pay loaders, Buckminster Fuller's Dymaxion car, and the ThrustSSC.

Therefore rear-wheel steering usually only found in slower vehicles that need high-maneuverability in tight spaces, e.g. fork lifts.

For heavy haulage or for increased maneuverability, some semi-trailers are fitted with rear-wheel steering, controlled electro-hydraulically.

Collapsible steering columns were invented by Béla Barényi and were introduced in the 1959 Mercedes-Benz W111 Fintail, along with crumple zones.

on cars built by General Motors after an extensive and very public lobbying campaign enacted by Ralph Nader.

Boats with inboard motors sometimes steer by rotating the propeller pod only (i.e., Volvo Penta IPS drive).