Suspension Systems

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Suspension Systems

  1. 1. Suspension SystemsThe Suspension is one of the main components mounted on the frame part or thebasics structure of the vehicle. Also known as the chassis, the basic structure of thevehicle is the carrying unit upon which mounts several parts such as Power plant,Transmission, Suspension, Wheels & Tires, and the braking systems. Theillustration below depicts the basic components of vehicle on which frame or bodygets mounted.------------------------------------------------------------------------------------------------------------------- ---------- IQPC GmbH | Friedrichstr. 94 | D-10117 Berlin, Germany t: +49 (0) 30 2091 3330 | f: +49 (0) 30 2091 3263 | e: eq@iqpc.de | w: www.iqpc.de Visit IQPC for a portfolio of topic-related events, congresses, seminars and conferences: www.iqpc.de
  2. 2. The structure of car chassis has changed with course of time. Previously the chassisframe was either an integral or semi-integral frame upon which the car components,which included suspension system, got mounted. But recently, the manufacturersattach assembly parts to the body itself, thus eliminating the concept of framefunctionality during its manufacture. By doing so, all the functions of the frame arecarried out by the body. As an integral part of vehicle’s wheel alignment, thesuspension system contributes in reducing the tear & wears of the tires, and alsoassists in providing stability in driving of the vehicle.Components of Suspension SystemThe Suspension system in the vehicle essentially comprises of shock absorbers, coilsprings, spring shackles, stabilizer and leaf springs. This independent suspensionsystem of the car acts as an intermediate, connecting the rear wheels to its body soas to satisfy enjoyable as well as safety driving needs. The following gives a briefdescription about prime components in vehicle’s suspension system:Shock absorbersThese are also referred to as dampers, as they provide driving comfort bydampening the car’s vertical motion. In other words, they render a smooth drivewithout letting the car sway away or wallow alongside the road. Moreover, theshock absorbers eliminate the car vibrations that would otherwise have hadexperienced by its driver in the absence of shock absorbers. As significant unit ofvehicle’s suspension system, its presence provides dual benefit to the vehicle.Firstly, it makes sure that car chassis is protected from the bumps on the road.Shock absorbers absorb the shocks resulting from the road bumps by ensuring thatthe velocity of the car is not disturbed. In the absence of shock absorbers, every------------------------------------------------------------------------------------------------------------------- ---------- IQPC GmbH | Friedrichstr. 94 | D-10117 Berlin, Germany t: +49 (0) 30 2091 3330 | f: +49 (0) 30 2091 3263 | e: eq@iqpc.de | w: www.iqpc.de Visit IQPC for a portfolio of topic-related events, congresses, seminars and conferences: www.iqpc.de
  3. 3. bump on the road would have otherwise directly passed on the thrust to the carchassis, thus causing physical imbalance to car’s frame or body. Indirectly, shockabsorbers aid in prolonging a car’s physical life span. Secondly, they aid in keepingthe tires mobile on the road. Shock absorbers work in conjunction with othersuspension system components, primarily the springs. Technically, the shockabsorbers take the shocks from road bumps onto it through springs, which transferthe road shocks to the absorbers in form of kinetic energy. Shock absorbers in factcan allow the road shocks to be dissipated upon them by way of a constrictionvalve. It is suggested that the stiffness of any suspension is directly proportional tothe size of the constriction valve.SpringsSprings transforms the energy in road shocks onto the shock absorbers in form ofkinetic energy. They come either as coil springs or as leaf springs or in form oftorsion bars. Coil springs are essentially coiled torsion bars. All the pre-1985 makesof cars had leaf springs, and even today a significant number of heavy duty vehiclescontain it. Further, leaf springs can be bifurcated as either full-elliptic or semi-elliptic or three-quarter elliptic or transverse spring type or in form of helper springtype. Amongst these, the semi-elliptic, transverse spring and helper spring type ofleaf springs are common in use today. In fact, 75% of the cars today carry semi-elliptic leaf spring within its suspension system. The torsion bar rendersperformance very similar to coiled-spring type. However, its degree of performancerests on the twisting abilities of its steel bar. The rear suspension of Peugeot 205s,Porsches (pre- 1989), amongst other cars had torsion bar springs, wherein the axlegets directly attached to one end of steel shaft. The other end of it gets held bysplines through a slotted tube. As aforementioned, the twisting ability of steel bardictates its magnitude of its performance.------------------------------------------------------------------------------------------------------------------- ---------- IQPC GmbH | Friedrichstr. 94 | D-10117 Berlin, Germany t: +49 (0) 30 2091 3330 | f: +49 (0) 30 2091 3263 | e: eq@iqpc.de | w: www.iqpc.de Visit IQPC for a portfolio of topic-related events, congresses, seminars and conferences: www.iqpc.de
  4. 4. A Coil-over unitIt is typical all-in-one unit which assists the shock absorber as well as thesuspension spring. This unit takes care of the adjustable spring plate and adjustabledampening valve of the car. Essentially, this small unit is a tension adjuster. Intoday’s times of enhanced technology and innovative technicalities, a large numberof cars carry adjustable compression dampening whereas motor bikes are rewardedwith spring tension preload adjustments.Types of Suspension SystemVarious technical experts give different meanings to vehicle’s suspension system.However, they more or less tend to confuse a layman. With advancement intechnology implicating added computer software systems to regulate most of thecar component’s architecture, it is not ideal anymore to relate a car’s suspensionsystem to given one type. Although for the sake of understanding, suspensionsystem could be ideally dissected into four main types, namely – Conventionalsuspension system, Independent suspension system, Air suspension systemand Hydro elastic suspension system. In fact the later two types can be termed asDigital suspension systems.Conventional suspension systemIn this traditional type of suspension system, two wheels get mounted on each sideof the axle, so as to disallow its wheels from experiencing gyroscopic effect,although when the bump is experienced by only one of the wheels. Thus, theupward velocity to be effected by both the wheels is eliminated. This type ofsuspension system is popularly used in rear driving wheels, whereby the wheels getplaced on the live axle, with the aid of shock absorbers and leaf springs or coilsprings suspending it accordingly. This type of suspension system makes use of Coil------------------------------------------------------------------------------------------------------------------- ---------- IQPC GmbH | Friedrichstr. 94 | D-10117 Berlin, Germany t: +49 (0) 30 2091 3330 | f: +49 (0) 30 2091 3263 | e: eq@iqpc.de | w: www.iqpc.de Visit IQPC for a portfolio of topic-related events, congresses, seminars and conferences: www.iqpc.de
  5. 5. springs. In more recent times, the air spring finds place instead of conventional coilspring, immaterial whether powered by an engine driven or compressor. In this, thepressurized air acts as a spring. This type of suspension has simple structure,therefore can be built on a low cost budget. Asymmetric tandem axle suspensionsystems are purely conventional or traditional in form of their getting used on heavytrucks or trailers. However, tandem axle could be classified into either Airsuspension or spring suspension or a torsion bar suspension. This type ofsuspension is better than single axle and resolves the problem of diversification ofload, which single axle suspension suffered from.The following illustration depicts key suspension types with efficacy.------------------------------------------------------------------------------------------------------------------- ---------- IQPC GmbH | Friedrichstr. 94 | D-10117 Berlin, Germany t: +49 (0) 30 2091 3330 | f: +49 (0) 30 2091 3263 | e: eq@iqpc.de | w: www.iqpc.de Visit IQPC for a portfolio of topic-related events, congresses, seminars and conferences: www.iqpc.de
  6. 6. Independent suspension systemThis suspension type utilizes the front wheels in order to have its designincorporated. However, both the front and rear wheels get benefited from it.Independent suspension system comes in 3 forms, namely - McPherson Strut,double wishbone and trailing arm or multi-link suspension.McPherson StrutIt consists of a ball joint on the single arm over which is pivoted combo of strut-strut shock absorber and spring. It is most widely used suspension system incars, wherein the steering gear is either connected to the arm of the spindle or tothe lower end of shock absorber. In this, all the three components – the shockabsorber, spring and spindle assist in steering operations. In fact, the strut actsmore than the shock absorbers in providing support to the vehicle, whilesimultaneously absorbing the shock.Double WishboneThe system in this allows the free upward and downward movement of the spindle.By this, its wishbone movement around pivot points is described by its slight motionvarying side to side, such a motion or movement also called as scrub. The scrubmotion always exists, except where the motion is too long. This type of suspensionis also articulated by movements of Steer and Camber. Although this type is mostlyarticulated by Double A arm, Double wishbone can also be in the form of a single A-arm combined with a solid arm. Double Wishbone aids in providing a consistent feelin handling of steering.------------------------------------------------------------------------------------------------------------------- ---------- IQPC GmbH | Friedrichstr. 94 | D-10117 Berlin, Germany t: +49 (0) 30 2091 3330 | f: +49 (0) 30 2091 3263 | e: eq@iqpc.de | w: www.iqpc.de Visit IQPC for a portfolio of topic-related events, congresses, seminars and conferences: www.iqpc.de
  7. 7. Multi-link SuspensionIn this, each arm is separately placed unlike the other forms of independentsuspension system. However, the mechanics or the principle used by multi-linksuspension is identical to other forms of independent suspension system. All foursuspension arms are torque by the spindle, so as to turn according to the steering.The benefits of this type of front wheel independent suspension system can befound in experiencing lesser vibrations, enhanced tire grip, and negligible steeringreaction. However, multi-link suspension is expensive, which increases the wear &tear of tires due to increased torque transmission. Moreover, upon installation ofMulti-link suspension, vehicle would require better performing shock absorbers.Air Suspension systemThis system comprises of an air tank, compressor and air bags for each wheel.While maintaining pressure to approximately 5.6 to 7 kg/sq.m, air tank gets filledwith air. Further, with application of load the leveling valve gets actuatedcompressing the air bag. The level of frame is enhanced when the compressed airbag gets filled by the air in the tank. As and when the load from chassis isdecreased, the air bag releases more air.The diagram below could clarify the working of Air Suspension System.------------------------------------------------------------------------------------------------------------------- ---------- IQPC GmbH | Friedrichstr. 94 | D-10117 Berlin, Germany t: +49 (0) 30 2091 3330 | f: +49 (0) 30 2091 3263 | e: eq@iqpc.de | w: www.iqpc.de Visit IQPC for a portfolio of topic-related events, congresses, seminars and conferences: www.iqpc.de
  8. 8. The prime advantage of Air suspension system lies in the maintenance ofconstant frequency of vibration irrespective of whether the vehicle is unladed or not.This is the system incorporating today’s digital technology, which aids in renderingof smooth and comfortable ride. Once the vehicle sets in motion, Air suspensionsystem helps in reducing weight. Moreover, this suspension system favorsmaintain constant frame height. However, common problems faced by Airsuspension system may be due to dryer failure, compressor failure and Air strutor Air bag failure.------------------------------------------------------------------------------------------------------------------- ---------- IQPC GmbH | Friedrichstr. 94 | D-10117 Berlin, Germany t: +49 (0) 30 2091 3330 | f: +49 (0) 30 2091 3263 | e: eq@iqpc.de | w: www.iqpc.de Visit IQPC for a portfolio of topic-related events, congresses, seminars and conferences: www.iqpc.de
  9. 9. Hydrolastic suspension systemThis kind of suspension provides better leveling of the car, by connecting front andrear system amicably. Hydrolastic displacers are each provided in front and endsuspension units. The rubber valves take care of damping necessities. A small borepipe interconnects the front and end suspensions. In this case, if the front wheelexperiences a bump, fluid is transmitted to the rear suspension unit by aid of apiston giving pressure to such fluid. With changing times, Hydrolastic suspension isnow refined to Hydro pneumatic suspension. The main difference between the twolies in the architecture of displacer unit, removal of rubber springs in the refinedversion and the inclusion of nitrogen gas which acts as a damper as well as thespring. The fluid however is allowed to freely flow from the front to rear unit, merelyacting as separating diaphragm.Usage of Auxiliary Devices in modern day usageIt is unanimously agreed that different suspension systems suffer from differentdrawbacks. As a solution to correct this situation and also for striving for achieving‘Driving safety’ as well as ‘Driving comfort’, vehicles are now being incorporated byauxiliary devices such as Panhard rod, torque arm and sway bar. These devices areattached to a suspension system in use without disturbing its architecture ofapplication. While a Panhard rod assists in preventing the axel wheel from swayingor moving laterally, the Sway bar acts as a stabilizer. A torsion spring function inthe Sway bar aids in enhancing the roll stiffness of the suspension.In today’s global scenario, the significance of suspension systems in the car iswell-recognized. That the vehicle suspension systems add immense value to themobility of the vehicle and also operates as a pertinent part for its life-long------------------------------------------------------------------------------------------------------------------- ---------- IQPC GmbH | Friedrichstr. 94 | D-10117 Berlin, Germany t: +49 (0) 30 2091 3330 | f: +49 (0) 30 2091 3263 | e: eq@iqpc.de | w: www.iqpc.de Visit IQPC for a portfolio of topic-related events, congresses, seminars and conferences: www.iqpc.de
  10. 10. maintenance is an undisputed recognition. The manufacturers have now gone a stepforward to patent some of its suspension system designs. As to how thesuspension systems can add better value to comfortable driving on the platformof economies of scale, will be elaborated in the following article. Equally important isto take notice on how the use of lightweight materials could add to drivingscalability. Use of lightweight materials also accentuates the need for lightweightsuspension systems, in order to provide effective results as well as an adherenceto the government regulations proposing the need for lighter vehicles.References:http://www.carbibles.com/suspension_bible.htmlwww.frost.comwww.benthamscience.comhttp://autoshepherd.com/category/Steering-Suspension/1072 Want to know more about suspension systems? Check out our Download Centre, where you will find more articles, white papers and interviews regarding this topic: http://bit.ly/suspension-articles------------------------------------------------------------------------------------------------------------------- ---------- IQPC GmbH | Friedrichstr. 94 | D-10117 Berlin, Germany t: +49 (0) 30 2091 3330 | f: +49 (0) 30 2091 3263 | e: eq@iqpc.de | w: www.iqpc.de Visit IQPC for a portfolio of topic-related events, congresses, seminars and conferences: www.iqpc.de

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