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Word Description
Camber Camber angle is the angle made by the wheels of a vehicle; specifically, it is the angle between the vertical axis of the wheels used for steering and the vertical axis of the vehicle when viewed from the front or rear. It is used in the design of steering and suspension. If the top of the wheel is farther out than the bottom (that is, away from the axle), it is called positive camber; if the bottom of the wheel is farther out than the top, it is called negative camber. Camber angle alters the handling qualities of a particular suspension design; in particular, negative camber improves grip when cornering. This is because it places the tire at a more optimal angle to the road, transmitting the forces through the vertical plane of the tire, rather than through a shear force across it. Another reason for negative camber is that a rubber tire tends to roll on itself while cornering. If the tire had zero camber, the inside edge of the contact patch would begin to lift off of the ground, thereby reducing the area of the contact patch. By applying negative camber, this effect is reduced, thereby maximizing the contact patch area. Note that this is only true for the outside tire during the turn; the inside tire would benefit most from positive camber. On the other hand, for maximum straight-line acceleration, the greatest traction will be attained when the camber angle is zero and the tread is flat on the road. Proper management of camber angle is a major factor in suspension design, and must incorporate not only idealized geometric models, but also real-life behavior of the components; flex, distortion, elasticity, etc. What was once an art has now become much more scientific with the use of computers, which can optimize all of the variables mathematically instead of relying on the designer's intuitive feel and experience. As a result, the handling of even low-priced automobiles has improved dramatically in recent years. In cars with double wishbone suspensions, camber angle may be fixed or adjustable, but in MacPherson strut suspensions, it is normally fixed. The elimination of an available camber adjustment may reduce maintenance requirements, but if the car is lowered by use of shortened springs, the camber angle will change. Excessive camber angle and can lead to increased tire wear and impaired handling. Significant suspension modifications may correspondingly require that the upper control arm or strut mounting points be altered to allow for some inward or outward movement, relative to longitudinal center line of the vehicle, for camber adjustment. Aftermarket plates with slots for strut mounts instead of just holes are available for most of the commonly modified models of cars.
Camber (Control) Camber changes due to wheel travel, body roll and suspension system deflection or compliance. In general, a tire wears and brakes best at -1 to -2° of camber from vertical. Depending on the tire and the road surface, it may hold the road best at a slightly different angle. Small changes in camber, front and rear, can be used to tune handling. Some race cars are tuned with -2~-7° camber depending on the type of handling desired and the tire construction. Oftentimes, too much camber will result in the decrease of braking performance due to a reduced contact patch size through excessive camber variation in the suspension geometry. The amount of camber change in bump is determined by the instantaneous front view swing arm (FVSA) length of the suspension geometry, or in other words, the tendency of the tire to camber inward when compressed in bump.
Caster Caster angle is the angular displacement from the vertical axis of the suspension of a steered wheel in a car, bicycle or other vehicle, measured in the longitudinal direction. It is the angle between the pivot line (in a car - an imaginary line that runs through the center of the upper ball joint to the center of the lower ball joint) and vertical. Car racers sometimes adjust caster angle to optimize their car's handling characteristics in particular driving situations.
Center (Drag) Link A drag link converts rotary motion from a crank to a second crank or link in a different plane or axis. The term is commonly used in automotive technology for the link in a four bar steering linkage that converts rotation of a steering arm to a center link and eventually to tie rod links which pivot the wheels to be steered. A drag link is used when the steering arm operates in a plane above the other links. The drag link converts the sweeping arc of the steering arm to linear motion in the plane of the other steering links.
Chassis In the case of vehicles, the term chassis means the frame plus the "running gear" like engine, transmission, driveshaft, differential, and suspension. A body, which is usually not necessary for integrity of the structure, is built on the chassis to complete the vehicle.
Coil Spring A coil spring is a mechanical device, which is typically used to store energy and subsequently release it, to absorb shock, or to maintain a force between contacting surfaces. They are made of an elastic material formed into the shape of a helix which returns to its natural length when unloaded. Coil springs are a special type of torsion spring: the material of the spring acts in torsion when the spring is compressed or extended.
Control Arm A control arm is a suspension member intended to control wheel motion in the longitudinal (fore-aft) plane. The link is connected (with a rubber or solid bushing) on one end to the wheel carrier or axle, on the other to the chassis or uni-body of the vehicle. Control arms typically are mounted ahead of the wheel. In that position they resist dive under braking forces and wheel hop under acceleration.