Car Suspensions Why important • power generated by a engine is useless if the driver can't control the car • Car suspension job : – to maximize the friction between the tires and the road surface – to provide steering stability with good handling – to ensure the comfort of the passengers Double-wishbone suspension Suspension as part of Chassis major systems in vehicle major systems in vehicle • Frame - structural, load-carrying • Steering system - mechanism that component that supports the car's enables the driver to guide and direct engine and body, which are in turn the vehicle supported by the suspension • Tires and wheels - components that • Suspension system - setup that make vehicle motion possible by way of supports weight, absorbs and dampens grip and/or friction with the road shock and helps maintain tire contact three components of any suspension: Coil Springs • springs • most common type • dampers made by heavy-duty • anti-sway bars. torsion bar coiled around an axis. Coil springs compress and expand to absorb the motion of the wheels Leaf springs • several layers of metal bound together to act as a single unit. mostly used in trucks and heavy-duty vehicles Torsion bars • use the twisting properties of a steel bar to provide coil-spring-like performance • One end of a bar is anchored to the vehicle frame -- the other end to a wishbone, which acts like a lever that moves perpendicular • When the wheel hits a bump, vertical motion is transferred to the wishbone -- then, through the levering action. Torsion bar then twists along its axis to provide the spring force Dampers: Shock Absorbers • controls unwanted spring motion through a process known as dampening • Shock absorbers reduce magnitude of vibration by turning kinetic energy of suspension movement into heat energy Dampers: Struts and Anti-sway Bars • strut -- shock absorber mounted inside a coil spring • perform two jobs: dampening function like shock absorbers, and structural support for the vehicle suspension Dampers: Anti-sway Bars • anti-roll bars -- used along with shock absorbers or struts to give additional stability Suspension Types: Front McPherson strut • Front suspension - dependent systems • combines shock absorber and coil – rigid front axle that connects the front spring into a single unit wheels • more compact and lighter suspension • Front Suspension - Independent system that used for front-wheel drive Systems vehicles – allowed to move independently Double wishbone suspension systems • several different configurations with wishbone-shaped arms • mounting positions one at frame and one at wheel • Each wishbone bears a shock absorber and a coil spring to absorb vibrations • help minimize roll or sway and provide for a more consistent steering feel Coil Spring type 1 • wheel spindles are supported by an upper and lower 'A' shaped arm • the lower arm carries most of the load Coil Spring type 2 Multi-link suspension • as the spindle turns for steering, it alters • lower arm be replaced the geometry of the suspension by with a single solid arm torquing all four suspension arms – as control arm • gives even better road-holding properties • load-bearing capability • the spring (red) is separate from the almost entirely to the shock absorber upper arm and the spring mounts Trailing-arm suspension • arm is joined at the front to the chassis, allowing the rear to swing up and down • twin-trailing-arm work on exactly same as the double wishbones Rear suspension - dependant systems Solid-axle, coil-spring • Solid-axle, leaf-spring Beam Axle 4-Bar • diagonal bar • rear end housing is always perpendicular to the ground prevent side-to- • lateral stability by diagonal bar side movement in the beam • front wheel drive cars Hydrolastic Suspension Hydropneumatic Suspension.