Suspension (vehicle)

The suspension is part of the undercarriage of vehicles. It aims to ensure that the wheels follow bumps in the road while providing uniform as possible traction, the rest of the vehicle but not possible moves up and down.

Without suspension suggestions would be transferred by road bumps unfiltered on the vehicle, which would lead, especially at higher speeds to very strong shaking in the vertical direction. Vehicle, driver, passengers and cargo would be exposed to strong forces and the wheels would temporarily lose contact with the road and reduce greatly the wheel load. So the suspension is not only for comfort, but also the driving safety and protection of the vehicle.

Even the tires wears a small part in the suspension of the vehicle. The main part of which is ensured by the springs.

Travel

The way the wheel between unloaded ( wheel load zero) sets and loaded position (usually twice the static wheel load ) is referred to as total travel. At rest, the mass of the vehicle rests on the springs and reduces the overall travel to sag on the positive travel.

A large suspension travel allows compensation of large bumps in the road, but causes a high center of gravity of the vehicle and therefore is contrary to two-lane vehicles at high speeds in bends. Therefore, sports cars have usually a small travel. The shorter the spring excursion, the stiffer the spring must. This is true for conventional steel - linear springs whose force increases with the Wegverkürzung, and for steel torsion bar springs whose torque increases with the angle of rotation, but it is not always the case for air, gas, hydraulic or combination systems.

The travel can be reduced by Bump.

Unsprung and sprung mass

The construction is resilient to the sprung mass. The springs are supported from the structure of so-called unsprung masses, essentially the axles and wheels on the ground. To unsprung masses include other than the wheels and axles, axle shafts (driven axes, attributed with independent suspension only partially ) the wheel bearings, brakes and suspension components ( shocks, springs, sway bars and suspension link (only for rigid axle ) ). The wheel load and to a lesser extent, the accelerations in the construction are the better, the smaller the unsprung mass in relation to the sprung mass of the vehicle.

In order, the best possible ratio of unsprung to reach the sprung mass, particularly lightweight wheels made ​​of aluminum alloys, magnesium alloys or carbon fiber as well as light braking systems are used for example with carbon fiber -ceramic brake discs of sports and racing cars.

Damping

Without shock absorbers, the vehicle would be a swinging after every speed bump or change in direction long as only the shock would be absorbed. These movements affect not only driving comfort, they endanger especially driving safety, since, constantly changing the forces that push the wheel on the road during the swing, and thus the maximum forces that the tire along and transmitted across can. When swaying thus the vehicle in curves is so unstable that it can no longer be controlled and inevitably breaks or even overturns. In the technical implementation has therefore - not only in vehicle technology - proven a spring - damper combination.

Designs

In the first automobiles, the suspension was achieved as in carriages, each by one pair of leaf springs per axle. To date, this construction is used on commercial vehicles.

Today's most common form of suspension is by coil springs.

The VW Beetle was already in the pre-war prototypes behind two torsion springs ( torsion springs ), which often broke first, before the right material was found. In the large series there were no problems with it. Here, a torsion bar in the center of the vehicle is securely supported and mounted on the side of the vehicle about 30 cm in front of the rear - drive axle for rotation for each wheel in a fixed tube; there sitting on the torsion bar, the so-called " spring sword " as a lever arm to which the Halbach pendulum is attached to the wheel bearing.

In the 1950s there were at American automakers vehicles with longitudinally arranged torsion springs, sometimes even with level control.

The spread of buses and trucks air suspension in which a compressor generates air pressure which causes about bellows a comfortable suspension with the possibility of a level control, was first used in Germany by Borgward. In the sixties, a part of the upper class limousines from Mercedes -Benz was air suspension.

Citroën is building in his car of the middle class and upper class since the Citroën DS, a hydropneumatic suspension ( hydropneumatic ) a. In the past, Mercedes -Benz and Rolls- Royce have used under license. With the Citroën XM Citroën introduced the electronically controlled Hydractive. The Citroën Xantia Activa had additionally an active chassis stabilization, which almost completely suppressed the body roll when cornering.

DaimlerChrysler In the late 1990s, the S-Class with the so-called AirMatic equipped the first premium manufacturer, which consists of a quadruple air suspension with adjustable dampers. Here for the first time an externally guided rolling bellows was used with axial tensile members. Meanwhile, various manufacturers offer the upscale models with an (optional ) air suspension, which significantly contributes to the comfort. The level can be adjusted with the air suspension on the driving situation. For example, can be increased or decreased on the highway in the terrain level whereby the air resistance is reduced.

The highlight of the recent technical development is considered the computer-aided fully active suspension, such as Active Body Control in introduced in 1999 Mercedes -Benz CL- Class in which it is a hydraulic system for active spring base point adjustment.

Still not found in production vehicles is the electric suspension, in which an electromagnetic linear motor pushes the wheel down or pulls up again. All potholes over which you drive will be completely damped / sprung without the occupants of the vehicle feel about it. This system also makes it possible in theory to let the car jump over obstacles.

Bikes

For bicycles and motorcycles different suspension systems are used. Commonly found is a telescopic fork at the front, which also takes over the wheel control means of telescoping tubes except the suspension.

Rear suspensions are usually configured as a rocker. For scooters this rocker is at the same time drive carrier with motor and gear reduction, but increasing the unsprung masses. Rare suspension and wheel guidance systems are also installed separately, such as the Ackermann steering in the Yamaha GTS 1000 Bimota Tesi or. Successfully established, however, are the " Telelever " systems from BMW, which decouples the wheel location at the front of the suspension. In earlier times, the front wheels were often guided by swinging; is divided into long and short swing and pushed and pulled swing. Special types of swing are the Parallelogrammgabeln and the pendulum forks of motorcycles of the 1920s and 1930s.

The rear wheel of bicycles is nowadays often sprung; this means an enormous gain in comfort.

Tricycles

Trikes ( a front wheel, rear axle) have, however, usually no telescopic fork ( it would be for the high weight too unstable ), but swing guides on the front wheel. The asymmetric variant of the " tricycle ", the motorcycle sidecar, has reasons of trail shortening and lighter tractability often a " Earles Fork " forward, pushed a long swinging fork with separate components for wheel location and supports; the rear mostly used the found from the motorcycle manufacturer arrangement, and the sidecar was usually a longitudinal link or a semi-trailing arm.

Three Wheeler have a motorbike style swingarm for the driven single rear wheel, while the two front wheels are independently suspended on double wishbones with leaf or coil springs, or, as in Morgan Threewheelern of sliding sleeves.