PowerPoint Presentation

VEHICLE DYNAMICSPRESENTED BY: GROUP 3

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CONSIDERATIONS IN VEHICLE DYNAMICSRideVehicle HandlingBrakes

a cars ability to smooth out a bumpy road

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Important Systems that affect Vehicle DynamicsFrameSuspension systemSteering systemTires and wheels

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Car(Sprung Weight)Unsprung WeightSpringsShockTire (Rubber)Axles, Hubs, Bearings and Part of the suspension components

Thesprung massis the mass of the vehicle supported on the springs, while theunsprung massis loosely defined as the mass between the road and the suspension springs.

Tire has spring and shock absorber property. It can store and dissipate energy4

Suspensionis the term given to the system ofsprings,shock absorbersandlinkagesthat connects avehicleto itswheelsand allows relative motion between the twoC C - C

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OMFORTONTACTONTROL

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Car Suspension PartsSpringDampersShock absorbersStrutsAnti-sway bars

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SpringCoil SpringCoil springs compress and expand to absorb the motion of the wheels.Leaf SpringThis type of spring consists of several layers of metal bound together to act as a single unit.Torsion Baruse the twisting properties of a steel bar to provide coil-spring-like performance

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Dampers: Shock AbsorberShock absorbers slow down and reduce the magnitude of vibratory motionsShock absorbers work in two cycles -- thecompression cycleand theextension cycle.All modern shock absorbers arevelocity-sensitive

by turning the kinetic energy of suspension movement into heat energy that can be dissipated through hydraulic fluid.

Unless adampening structureis 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.

-- the faster the suspension moves, the more resistance the shock absorber provides

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StrutsBasically a shock absorber mounted inside a coil spring.Struts performs two jobs: dampening and structural supportShocks and struts can be considered critical safety features.

That means struts deliver a bit more than shock absorbers, which don't support vehicle weight -- they only control the speed at which weight is transferred in a car, not the weight itself.

Because shocks and struts have so much to do with the handling of a car, they can be considered critical safety features. Worn shocks and struts can allow excessive vehicle-weight transfer from side to side and front to back. This reduces thetire'sability to grip the road, as well as handling andbrakingperformance.9

Anti-sway BarsAre 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 andreduces vehicle sway. In particular, it combats the roll of a car on its suspension as it corners. For this reason, almost all cars today are fitted with anti-sway bars as standard equipment, although if they're not, kits make it easy to install the bars at any time.10

Types of SuspensionDependentDependent front suspensions have a rigid front axle that connects the front or the rear wheels.Weight, and AlignmentIndependentIn this setup, the front wheels are allowed to move independently.

Basically, this looks like a solid bar under the car, kept in place byleaf springs and shock absorbers. Common on trucks, dependent front suspensions haven't been used in mainstream cars for years.

Weight - or more specifically unsprung weight. Solid front axles weigh a lot and either need sturdy, heavy leaf springs or heavy suspension linkages to keep their wheels on the road.

Alignment - simply put, you can't adjust the alignment of wheels on a rigid axis. From the factory, they're perfectly set, but if the beam gets even slightly distorted, you can't adjust the wheels to compensate.

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Macpherson StrutThe MacPherson strut combines a shock absorber and a coil spring into a single unit. This provides a more compact and lighter suspension system that can be used for front-wheel drive vehicles.

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Advantages and DisadvantagesAdvantagesCheaper and Lighter than double-wishbone suspensionGreat for FWDNarrower than double-wishbone suspension

DisadvantagesTaller than double-wishbone suspensionMounts to body, so unibody is almost necessary for handling stress and forces

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Double WishboneAre used mostly at the front. There are two wishbones, one above the other, to keep the wheel upright as it rises and falls.

In automobiles, adouble wishbone(orupper and lowerA-arm)suspensionis anindependent suspensiondesign using two (occasionally parallel)wishbone-shaped arms to locate the wheel. Each wishbone or arm has two mounting points to thechassisand one joint at the knuckle. Theshock absorberandcoil springmount to the wishbones to control vertical movement. Double wishbone designs allow the engineer to carefully control the motion of the wheel throughout suspension travel, controlling such parameters ascamber angle,caster angle,toepattern,roll centerheight,scrub radius, scuff and more.

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Advantages and DisadvantagesAdvantagesVersatile (Placement of Shocks, etc.)Can handle large deflectionFront/BackDisadvantagesExpensiveComplex design

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Dependent vs. Independent SuspensionDependent SuspensionIndependent SuspensionMotion of a wheel on one side of the vehicle is dependent on the motion of its partner on the other side Motion of wheel pairs is independent, so that a disturbance at one wheel is not directly transmitted to its partner Rarely used in modern passenger cars Better ride and handlingCannot give good ride More expensive Cannot control high braking and accelerating torquesUsed in commercial and off-highway vehicles

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Engine Support and BushingsAbushingorrubber bushingis a type ofvibration isolator. It provides an interface between two parts, damping the energy transmitted through the bushing.

A common application is invehicle suspension systems, where a bushing made ofrubber(or, more often,synthetic rubberorpolyurethane) separates the faces of two metal objects while allowing a certain amount of movement. This movement allows the suspension parts to move freely, for example, when traveling over a large bump, while minimizing transmission of noise and small vibrations through to the chassis of the vehicle. A rubber bushing may also be described as aflexible mountingorantivibration mounting.

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Advantages and DisadvantagesAdvantagesLessnoise andvibrationare transmitted. Require little to nolubrication.DisadvantagesRubber bushings can deteriorate quickly in the presence of oils and extreme heat and cold.The flexibility of rubber also introduces an element of play in the suspension system.

As compared to solid connection

(e.g.,motor oil,mineral oil)

This may affect wheels of the vehicle during high-load conditions (cornering and braking), adversely affecting the vehicle'shandling.

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