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Suspension System and its application in Racing Cars. Zelealem H. Birhane. Suspension. The job of a car suspension is to maximize the friction between the tires and the road surface, to provide steering stability with good handling and to ensure the comfort of the passengers. Vehicle Dynamics.
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Suspension System and its application in Racing Cars Zelealem H. Birhane
Suspension The job of a car suspension is to maximize the friction between the tiresand the road surface, to provide steering stability with good handling and to ensure the comfort of the passengers.
Vehicle Dynamics Suspension • The study of the forces at work on a moving car is called vehicle dynamics. Most automobile engineers consider the dynamics of a moving car from two perspectives: • Ride - ability to smooth out a bumpy road. • Handling - ability to safely accelerate, brake and corner. • These two characteristics can be further described in three important principles - road isolation, road holding and cornering.
Chassis • The suspension important systems include: • The frame - structural, load-carrying component that supports the car's engine and body. • The suspension system - setup that supports weight, absorbs and dampens shock and helps maintain tire contact • The steering system - mechanism that enables the driver to guide and direct the vehicle • The tires and wheels - components that make vehicle motion possible by way of grip and/or friction with the road.
Springs • Coil springs - a heavy-duty torsion bar coiled around an axis. Coil springs compress and expand to absorb the motion of the wheels. • Leaf springs - consists of several layers of metal (called "leaves") bound together to act as a single unit. Leaf springs were first used on horse-drawn carriages and were found on most American automobiles until 1985. They are still used today on most trucks and heavy-duty vehicles.
Springs • Torsion bars - Torsion bars use the twisting properties of a steel bar to provide coil-spring-like performance. This is how they work: One end of a bar is anchored to the vehicle frame. • Air springs - Air springs, which consist of a cylindrical chamber of air positioned between the wheel and the car's body, use the compressive qualities of air to absorb wheel vibrations.
Sprung/ unsprung mass The sprung mass is the mass of the vehicle supported on the springs, while the unsprung mass is loosely defined as the mass between the road and the suspension springs. The stiffness of the springs affects how the sprung mass responds while the car is being driven. Loosely sprung cars, such as luxury cars, can swallow bumps and provide a super-smooth ride; however, such a car is prone to dive and squat during braking and acceleration and tends to experience body sway or roll during cornering. Tightly sprung cars, such as sports cars, are less forgiving on bumpy roads, but they minimize body motion well, which means they can be driven aggressively, even around corners.
Shock Absorber Shock absorbers slow down and reduce the magnitude of vibratory motions by turning the kinetic energy of suspension movement into heat energy that can be dissipated through hydraulic fluid. A shock absorber is basically an oil pump. The upper mount of the shock connects to the frame, while the lower mount connects to the axle, near the wheel.
Suspension System A car can and usually have a different type of suspension on the front and back. Much is determined by whether a rigid axle binds the wheels or if the wheels are permitted to move independently. The former arrangement is known as a dependent system, while the latter arrangement is known as an independent system. In the following sections, we'll look at some of the common types of front and back suspensions typically used on mainstream cars.
Dependent Front Suspension Dependent front suspensions have a rigid front axle that connects the front wheels. Basically, this looks like a solid bar under the front of the car, kept in place by leaf springs and shock absorbers. Common on trucks, dependent front suspensions haven't been used in mainstream cars for years.
Independent Front Suspensions The MacPherson strut, developed by Earle S. MacPherson of General Motors in 1947, is the most widely used front suspension system, especially in cars of European origin. This provides a more compact and lighter suspension system that can be used for front-wheel drive vehicles.
F1 Suspension The Formula One racing car represents the pinnacle of automobile innovation and evolution. Lightweight, composite bodies, powerful V10 engines and advanced aerodynamics have led to faster, safer and more reliable cars.
F1 Suspension Rules regulating suspension design say that all Formula One racers must be conventionally sprung, but they don't allow computer-controlled, active suspensions. To accommodate this, the cars feature multi-link suspensions, which use a multi-rod mechanism equivalent to a double-wishbone system. In all cars, the primary benefit of a double-wishbone suspension is control. Unlike road cars, however, the shock absorbers and coil springs of a Formula One racecar don't mount directly to the control arms.
F1 Suspension Instead, they are oriented along the length of the car and are controlled remotely through a series of pushrods and bell cranks. In such an arrangement, the pushrods and bell cranks translate the up-and-down motions of the wheel to the back-and-forth movement of the spring-and-damper apparatus.
