Car Suspension system Mohammad Al-Sarah Mohammad Hammoudi The Hashemite University of Jordan Faculty of Engineering Department of Mechanical Engineering Car Suspension system Mohammad Al-Sarah Mohammad Hammoudi Baha Fawwaz Ali Moaz Mustafa Quraini Omer Tahseen Zaid Al-Thaher

Discussed subjects : Introduction What does a suspension do? What are the major parts of a suspension? And what does each part do? What are the major types of car suspensions? The difference between sprung and unsprung mass and the effects of it on driving and power transmitting. An example for special suspension system.

Introduction The suspension is a part of the car chassis, which Is made of: The frame: which supports the car weight and engine (supported by the suspension). The suspension system. The steering system. The tiers and wheels.

What does a suspension do? One of the most important part of your car is the suspension, the suspension prevent you from shaking your car into pieces as you drive tons of metal at fast speed on a road no matter how smooth the road is. Car suspension provide a safe smooth ride to the car and passengers.

Major parts of a suspension The suspension is made of two major parts: Springs: Coil springs: Coil springs are the most type used Coil springs absorb the motion of the wheels. (springs can’t be used alone, because they are good at absorbing energy but not good at dissipating it, that’s why we will Introduce shock absorbers).

Leaf springs: consists of several layers of metal (called "leaves") bound together to act as a single unit. To get rid of friction between leaves it can be polished or separated by plastic layers. They were first used in horse-drawn carriages and then introduced into cars in the 1985s and they are still used in heavy duty trucks.

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. The other end is attached to a wishbone, which acts like a lever that moves perpendicular to the torsion bar. When the wheel hits a bump, vertical motion is transferred to the wishbone and then, through the levering action, to the torsion bar. The torsion bar then twists along its axis to provide the spring Force. This system was introduced In the 1950s and 1960s.

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. The concept is actually more than a century old and could be found on horse-drawn buggies. Air springs from this era were made from air-filled, leather diaphragms, much like bellows; they were replaced with molded-rubber air springs in the 1930s.

Sprung and unsprung mass Based on where springs are located on a car -- i.e., between the wheels and the frame -- engineers often find it convenient to talk about the sprung mass and the 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.

The greater the unsprung weight, the greater the inertia of the suspension, which will be unable to respond as quickly to rapid changes in the road surface. As an added benefit, putting lighter wheels on the car can increase your engine's apparent power. Why? Well the engine has to turn the gearbox and driveshaft, and at the end of that, the wheels and tires. Heavier wheels and tires require more torque to get turning, which saps engine power.

Struts and Anti-sway Bars: The shock absorbed provide damping but can’t provide structural support , that’s why a strut is Introduced also to provides damping and stability. Anti-sway bars: Anti-sway bars (also known as anti-roll bars) are used along with shock absorbers or struts to give a moving automobile additional stability. An anti-sway bar is a metal rod that spans the entire axle and effectively joins each side of the suspension together. When the suspension at one wheel moves up and down, the anti-sway bar transfers movement to the other wheel. This creates a more level ride and reduces vehicle sway. In particular, it combats the roll of a car on its suspension as it corners. strut

Dampers: damping systems consist of Shock absorbers(snubber): Unless a dampening structure is present, a car spring will extend and release the energy it absorbs from a bump at an uncontrolled rate. The spring will continue to bounce at its natural frequency until all of the energy originally put into it is used up. A suspension built on springs alone would make for an extremely bouncy ride and, depending on the terrain, an uncontrollable car. it also controls unwanted spring motion through a process known as dampening. 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.

Shock absorbers work in two cycles -- the compression cycle and the extension cycle. The compression cycle occurs as the piston moves downward, compressing the hydraulic fluid in the chamber below the piston. The extension cycle occurs as the piston moves toward the top of the pressure tube, compressing the fluid in the chamber above the piston. A typical car or light truck will have more resistance during its extension cycle than its compression cycle. With that in mind, the compression cycle controls the motion of the vehicle's unsprung weight, while extension controls the heavier, sprung weight. All shock absorbers are Velocity sensitive. The design showed here is twin tube which is the most used kind.

Suspension types They can be classified as: Dependent. Independent. Dependant suspension: Dependent suspensions have a rigid axle that connects the (front or rear) wheels. Basically, this looks like a solid bar under the front of the car, kept in place by leaf springs and shock absorbers. Independent suspension : Independent suspension is a broad term for any automobile suspension system that allows each wheel on the same axle to move independently of each other

Independent front suspension: MacPherson Strut Double wishbone suspension Multi-link suspension Trailing-arm suspension Twin I-Beam suspension Transverse leaf-spring

Dependent suspension: Solid-axle, leaf-spring Solid-axle, coil-spring Beam Axle

The Bose Suspension System The Bose system uses a linear electromagnetic motor (LEM) Amplifiers provide electricity to the motors in such a way that their power is regenerated with each compression of the system. The main benefit of the motors is that they are not limited by the inertia inherent in conventional fluid-based dampers. As a result, an LEM can extend and compress at a much greater speed, virtually eliminating all vibrations in the passenger cabin. This system will be available in the year 2009