Automotive chassis and suspension by M A Qadeer

Automotive chassis and suspensions

M A Qadeer Siddiqui

By

Mohd Abdul Qadeer Siddiqui 1

Automotive chassis and suspensions

M A Qadeer Siddiqui

Automotive Chassis and suspensions

Mohd Abdul Qadeer Siddiqui B-tech (Automobile Engineering) Bhaskar Engineering College (JNTU- Hyderabad)

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Automotive chassis and suspensions

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Road map to the syllabus Jawaharlal Nehru Technological University Hyderabad IV B-tech. Automobile Engineering-I semester

Unit 1) Introduction to Chassis system Introduction: Requirements of an automobile with types of automobiles, layout of an automobile with reference to power plant, power requirement for propulsion, various resistance to motion of the automobile.

Unit 2) Frames: Types of frames, materials, calculation of stresses on sections, constructional details, loading points, testing of frames. Wheels and tyres: Types of wheels, construction, structure and function of tyres, static and dynamic function of tyres. Unit 3) Steering systems: Types of steering gears, front axle, under steer and over steer, wheel alignment, power steering, steering, steering geometry, wheel balancing, centre point steering, steerability. Unit 4) Brakes :Necessity of brake, stopping distance and time, brake efficiency, weight transfer, brake shoe theory, determination of braking torque, braking systems- mechanical, hydraulic, disk, parking and emergency brakes, servo and electrical brakes, details of hydraulic system, mechanical system and components. Types of master cylinders, factors influencing operation of brakes such as operating temperature, lining, brake clearance, pedal pressure, linkages etc.

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Automotive chassis and suspensions

M A Qadeer Siddiqui

Unit 5) Suspensions: Types of suspensions, leaf springs, materials, independent suspensions, torsion bar, air bellows or pneumatic , suspension, hydraulic suspension, constructional details of telescopic shock absorbers, types, vibrations and riding comfort, role axis of spring suspensions. Unit 6) Front wheel mounting, engine mounting, various types of springs used in suspension system, requirements and various types, material Unit 7) Testing: Testing procedure, types of tests and chassis components, equipment for lab and road test, preparation of test reports Unit 8) Two and three wheelers: classification of two and three wheelers, construction details, construction details of frames and forks, suspension systems and shock absorbers, different arrangement of cylinders. Carburetion system and operation

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Preface This book “automotive chassis and suspension” caters the need of JNTU-H specially. Each topic is explained in simple way to make student understand and comprehend the subject. Automotive chassis is the study of automotive body which includes the various parts such as frame, steering system, wheels, tyres and braking etc. Various types of suspensions which are used in automobiles are discussed with their constructional details and working. Chapter 1 deals with the introduction to chassis system. On what basis the chassis is designed and what are requirement of an automobile for propulsion will be discussed in this section. Chapter 2 deals with the frames. Each automobile requires a frame for its safety and design .How the frames are considered, their types, their stress factors and material used are discussed in this chapter. Chapter 3 is on wheels and tyres without which an automobile cannot stand on the road. What are various types of wheel, variour materials used in making wheels and tyres are discussed in this chapter. Chapter 4 deals with the steering system. The total controlling of a vehicle is done with steering system. Here we will be discussing about the various types of steering, the concept of oversteer and understeer. Chapter 5 deals with braking system which is the most important part of a running automobile for handling and safety. The braking system is getting more and efficient these days, ABS (antilock braking system) is the best example for that. We will be explaining about the various types of brakes, their constructional feature and their working in detail. Chapter 6 and chapter 7 focus on various suspension systems used in automobiles, mounting of wheels and testing of an automobile. Chapter 8 gives a brief introduction to 2 and 3 wheeler automobiles, their difference of constructions and operation.

The corrections, suggestions and feedbacks from the readers are always appreciated and duly acknowledge. You can reach the author at [email protected]

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Contents

1. Introduction to chassis system……8 2. Frames……………………………….14 3.Steering system……………………..34 4. Brakes……………………………….46 5. Suspensions…………………………64 6. Mountings of wheels and engine…..79 7. Testing………………………………88 8. Two and three wheelers…………….103

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1)INTRODUCTION TO CHASSIS SYSTEM REQUIREMENT OF AN AUTOMOBILE Automobiles in the present day world have become an internal part of human life. By definition an auto-mobile or car is a wheeled vehicle that carries its own motor and transports passengers. The auto-mobile as we know it was not invented in a single day by a single inventor. The history of the auto-mobile reflects an evolution that took place worldwide. Like any other commodity, auto-mobiles are also reaching the summit of perfection, customer’s demands and sorts of comforts, these include good and comfortable interiors, low noise, high speeds, safety and shock freeness even at high speeds, light steering, and power operated windows and brakes and so many other comforts including communication and entertainment facilities.

Main components of an Automobile are as follows:1) The basic structure 2) The power plant 3) The transmission system 4) Controls (Steering and Brakes) 5) The auxiliaries 6) The superstructure The basic structure is the unit on which the remainder of the unit required to turn it into a power operated vehicle. It consists of the frame, the suspension system, axle, wheels and tires. The power plant (engine) provides the motive power for all the functions which the vehicle or any part of it, may be called upon to perform.

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The transmission system consists of a clutch, a gear box giving different torque ratios at the output, a propeller shaft and a differential gear to distribute the final torque equally between the driving wheels. The auxiliaries consists of mainly of the electrical equipment, the supply system consisting of a battery and dynamo, the starter, the ignition system and auxiliary devices like driving lights, signaling other lights, heater, radio, fan etc. The controls consist of steering system and brakes. The superstructure consists of the car body attached to the frame.

LAYOUT OF AN AUTOMOBILE

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TYPES OF AUTOMOBILES Automobiles or vehicles can be classified on different bases as given below: On the Basis of Load (a) Heavy transport vehicle (HTV) or heavy motor vehicle (HMV), e.g. trucks, Buses, etc. (b) Light transport vehicle (LTV), e.g. pickup, station wagon, etc. (c) Light motor vehicle (LMV), e.g. cars, jeeps, etc.

Wheels (a) Two wheeler vehicle, for example: Scooter, motorcycle, scooty, etc. (b) Three wheeler vehicle, for example: Auto rickshaw, three wheeler scooter for handicaps and tempo, etc. (c) Four wheeler vehicle, for example: Car, jeep, trucks, buses, etc. (d) Six wheeler vehicle, for example: Big trucks with two gear axles each having four wheels.

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Fuel Used (a) Petrol vehicle, e.g. motorcycle, scooter, cars, etc. (b) Diesel vehicle, e.g. trucks, buses, etc. (c) Electric vehicle which use battery to drive. (d) Steam vehicle, e.g. an engine which uses steam engine. These engines are now obsolete. (e) Gas vehicle, e.g. LPG and CNG vehicles, where LPG is liquefied petroleum gas and CNG is compressed natural gas.

Body On the basis of body, the vehicles are classified as: (a) Sedan with two doors (b) Sedan with four doors (c) Station wagon (d) Convertible, e.g. jeep, etc. (e) Van (f) Special purpose vehicle, e.g. ambulance, milk van, etc. Transmission (a) Conventional vehicles with manual transmission, e.g. car with 5 gears. (b) Semi-automatic (c) Automatic: In automatic transmission, gears are not required to be changed manually. It is automatically changes as per speed of the automobile.

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Position of Engine Engine in Front Most of the vehicles have engine in the front. Example: most of the cars, Buses, trucks in India. Engine in the Rear Side Very few vehicles have engine located in the rear. Example: Nano car

Vehicle Propulsion Systems A diversity of powertrain configurations is appearing *Conventional Internal Combustion Engine (ICE) powertrain. *Diesel, Gasoline, New concepts * Hybrid powertrains {Parallel/Series/Complex configurations} *Fuel cell electric vehicles *Electric vehicles

Various resistances to motion of the automobile Air Resistance This is the resistance offered by air to the movement of a vehicle. The air resistance has an influence on the performance, ride and stability of the vehicle and depends upon the size and shape of the body of the vehicle, its speed and the wind velocity. The last term should be taken into account when indicated, otherwise it can be neglected. Hence in general, air resistance,

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Rolling Resistance The magnitude of rolling resistance depends mainly on (a) the nature of road surface, (b) the types of tyre viz. pneumatic or solid rubber type, (c) the weight of the vehicle, and (d) the speed of the vehicle. The rolling resistance is expressed as where W = total weight of the vehicle, N and K = constant of rolling resistance and depends on the nature of road surface and types of tyres = 0.0059 for good roads = 0.18 for loose sand roads = 0.015, a representative value. A more widely accepted expression for the rolling resistance is given by where V = speed of the vehicle, km/hr. Mean values of a and 6 are 0.015 and 0.00016 respectively. Grade Resistance The component of the weight of the vehicle parallel to the gradient or the slope on which it moves is termed as ‘grade resistance’. Thus it depends upon the steepness of the grade. If the gradient is expressed as 1 in 5, it means that for every 5 metres the vehicle moves, it is lifted up by 1 metre. Hence, grade resistance is expressed as

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2) FRAMES TYPES OF CHASSIS FRAMES: There are three types of frames 1. Conventional frame 2. Integral frame 3. Semi-integral frame

1. Conventional frame: It has two long side members and 5 to 6 cross members joined together with the help of rivets and bolts. The frame sections are used generally. a. Channel Section – Good resistance to bending b. Tabular Section – Good resistance to Torsion c. Box Section – Good resistance to both bending and Torsion

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2. Integral Frame: This frame is used now a day in most of the cars. There is no frame and all the assembly units are attached to the body. All the functions of the frame carried out by the body itself. Due to elimination of long frame it is cheaper and due to less weight most economical also. Only disadvantage is repairing is difficult.

3. Semi – Integral Frame: In some vehicles half frame is fixed in the front end on which engine gear box and front suspension is mounted. It has the advantage when the vehicle is met with accident the front frame can be taken easily to replace the damaged chassis frame. This type of frame is used in some of the European and American cars.

Three types of steel sections are most commonly used for making frames: (a) Channel section, (b) Tubular section, and

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(c) Box section

VARIOUS TYPES OF FRAME Ladder Frame So named for its resemblance to a ladder, the ladder frame is the simplest and oldest of all designs. It consists merely of two symmetrical rails, or beams, and cross member connecting them. Originally seen on almost all vehicles, the ladder frame was gradually phased out on cars around the 1940s in favor of perimeter frames and is now seen mainly on trucks. This design offers good beam resistance because of its continuous rails from front to rear, but poor resistance to torsion or warping if simple, perpendicular cross members are used. Also, the vehicle's overall height will be higher due to the floor pan sitting above the frame instead of inside it. Backbone tube Backbone chassis is a type of an automobile construction chassis that is similar to the body-on-frame design. Instead of a two-dimensional ladder type structure, it consists of a strong tubular backbone (usually rectangular in cross section) that connects the front and rear suspension attachment areas. A body is then placed on this structure. Perimeter Frame Similar to a ladder frame, but the middle sections of the frame rails sit outboard of the front and rear rails just behind the rocker panels/sill panels. This was done to allow for a lower floor pan, and therefore lower overall vehicle in passenger cars. This was the prevalent design for cars in the United States, but not in the rest of the world, until the uni-body gained popularity and is still used on US full frame cars. It allowed for annual model changes introduced in the 1950s to increase sales, but without costly structural changes. In addition to a lowered roof, the perimeter frame allows for more comfortable lower seating positions and offers better safety in the event of a side impact. However, the reason this design isn't used on all vehicles is that it lacks stiffness, because the

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transition areas from front to center and center to rear reduce beam and torsional resistance, hence the use of torque boxes, and soft suspension settings. Superleggera An Italian term (meaning "super-light") for sports-car construction using a threedimensional frame that consists of a cage of narrow tubes that, besides being under the body, run up the fenders and over the radiator, cowl, and roof, and under the rear window; it resembles a geodesic structure. The body, which is not stress-bearing, is attached to the outside of the frame and is often made of aluminum. Unibody By far the most common design in use today sometimes referred to as a sort of frame. But the distinction still serves a purpose: if a unibody is damaged in an accident, getting bent or warped, in effect its frame is too, and the vehicle undrivable. If the body of a body-on-frame vehicle is similarly damaged, it might be torn in places from the frame, which may still be straight, in which case the vehicle is simpler and cheaper to repair.

Sub frame The sub frame, or stub frame, is a boxed frame section that attaches to a unibody. Seen primarily on the front end of cars, it's also sometimes used in the rear. Both the front and rear are used to attach the suspension to the vehicle and either may contain the engine and transmission. The most prolific example is the 1967-1981 Chevrolet Camaro.

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Calculation of stresses on section

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BENDING MOMENT

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Frame Material A car’s frame is the strong skeleton upon which the car is constructed. The frame should be constructed out of material that is sturdy and dependable. The automobile frame is the base of the car. It must be strong and stable. There are a few such materials that a car’s frame can be constructed of. An automobile can be made out of more than one material. Most vehicles currently use steel. Some vehicles may use aluminum, magnesium, or a combination of materials. The main composites utilized in the construction of vehicle chassis are titanium alloys, aluminum alloys and steel alloys. Each metal has diverse properties and multiple applications. The cost of each composite greatly varies. The vehicle’s chassis has to be rigid so that it can stand up to any force that is affects it. This is important for the suspension. On the chance that the chassis bends a little, the vehicle is not going to act as it would have. The suspension will be modified. The chassis cannot be totally rigid as it will become easily broken and thus become unusable. It must be neither too rigid nor too flexible. Types of Frames This chassis can be one of several different models of chassis. The first model that was designed is the ladder frame. This particular frame is one that is usually made from metal and is similar to the form of a ladder. It is inexpensive to build and can handle heavy loads. It was utilized in older model cars, sport utility vehicles, trucks and buses. The chassis can also take the shape of a space frame. This model is designed utilizing a number of small tubes to make a chassis that is three-dimensional. The tubes are placed to manage the stress that is put on the frame. These models are extremely precise and rigid. They are designed from different materials and usually exceptionally expensive. These types of frames are used for competition vehicles and sporty road vehicles. The frame can be designed as a one-piece structure. This is called monocoque. Large metal sheets are stamped with a large stamping device. The parts are fused together to form the chassis of the vehicle. The fusing method is automated. This makes this particular frame quick to create. It has a low tolerance. This design accounts for most of the vehicles currently made. It is made usually made of steel. The chassis is made to withstand almost any impact. Aluminum is sometimes used in the body of this type of chassis to reduce the weight. It is inexpensive and offers collision protection. It is also

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not as rigid as some other frames because it does not use tubes in the construction of the frame. The last type of frame can be called a mixture of the space frame and monocoque. The construction begins as a monocoque chassis and is completed with a space frame build. It is easy and inexpensive to make. It has the best of both frames. Conclusion Many of the chassis are made of steel and can weigh almost 3000 pounds or up to 4000 pounds for a sports utility vehicle. This frame is what offers protect during a collision. The body panels, roof and door frames are made of steel as well to withstand the force of a crash. The chassis is the part of the vehicle that keeps the passengers safe.

TESTING OF FRAMES The frame as core component of a commercial vehicle has to withstand without any serious damage the load and stress of a complete vehicle lifetime and needs therefore thoroughly testing with representative load data, derived of real case use. Also other chassis parts like axles, suspension, steering or add on parts have to be validated with dynamic loads and proof their durability prior to vehicle testing and final release. Engine and drivetrain components are additionally tested on our drivetrain test benches. Most fatigue tests are performed as realistic multi-channel tests under consideration of all acting torques and forces with up to 22 actuators. Finally we have in addition our own proving ground, where we perform functional and durability tests with the complete vehicle. With our expertise to measure and establish load data, we are able to establish representative test procedures, which reflect a vehicle lifetime of 1 million km in 150 to 500h test duration.

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9-channel test of rear axle bogey suspension in the ECS fatigue laboratory

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Wheels and tyres Vehicle wheels have developed from wooden spoked wheels via cast wheels to the sheet metal disc wheel of today. This is the most commonly used wheel in motor vehicle engineering at the present time. The wheel must be able to resist and transmit all forces which act between the road and the vehicle. The following essential demands are made on the vehicle: − Adequate rim stability − Firm fit of the tyre on the rim − Firm and secure connection with the wheel hub − Good dissipation of frictional heat − Adequate space for accommodating the brake system The following travelling comfort is demanded: − Vertical and lateral impact must be as small as possible − Unbalance at circumference must be kept low − Attractive design − Simple fitting of tyres to the rim and of wheel to the hub Production should be based on the following: − Low production price − Long service life − Low weight of the rim and small mass moment of inertia Types of wheel Wheels can be distinguished by the materials used for production and the design. Five of the most common types are listed below: − Wire−spoked wheels − Sheet metal wheels, double wall welded − Disc wheels − cast light metal wheels − cast steel wheels

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a) Well−base rim, b) rump rim, c) asymmetrical rim, d) tapered bead seat rim, e) wide base rim, f) 15 tapered rim

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Rim types a) flat base rim type 80 (with side ring 1), b) tapered bead seat rim type LS (with retaining ring 2), c) tapered bead seat rim type R 5 Firestone−Kronprinz system, d) tapered bead seat rim Lemmerz−system, e) tapered bead seat rim type AR

With regard to the rim base two types are distinguished: − Wide base rim − Well−base rim The wide base rim is in sections to allow easy fitting and removal of the tyre. It can either be halved along its circumference, or divided by a detachable wheel ring with locking spring. If it is to be divided along the circumference the two rim halves are connected and held together by bolts. Tapered bead seat rims are similar to wide base rims. They are used for heavy Lorries. Pitting the larger and stiffer tyres used for these vehicles makes the devision of the rim necessary, and so the rims are divided into two or three sections.

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There are different ways of dividing them. The centrally divided simples wheel and the triplex wheel are used. This triplex wheel is divided three times along its circumference, but each ring is a closed section. The tapered bead seat rim has virtually replaced the wide base rim in motor vehicle engineering. Its advantage in comparison to the wide base is that the bead seat inclines 5° to the rim flange. The bead of the tyre is pressed onto the tapered bead seat rim by the tyre pressure. In this way the tapered bead seat rim and the flange prevent the bead from tipping. Fig shows a tyre fitted to a tapered bead seat rim.

Tyre with tapered bead seat rim 1) fabric body, 2) flexing section, 3) tread, 4) shoulder, 5) tyre side wall, 6) side rubber, 7) bead, 8) rim flange, 9) tapered bead seat, 10) clincher, 11) bead core, 12) inner tube

For vehicles up to about 5 tonnes pay weight disc wheels are mainly used. Steel wires, known as bead cores, run around the circumference of tyres. These steel wires are closed and not ductile. In the well−base rim this recess helps in fitting the tyre. The tyre and bead are pressed into the well−base at one side, and then pressed inwards or outwards across the rim flange on the opposite side. The tyre is always pressed into the well−base at the opposite side to the valve.

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Tubeless tyre: 1 rim flange, 2 side rubber, 3 tyre side wall, 4 shoulder, 5 tread In passenger cars the wheel rim can have a 'hump' at the shoulder which prevents sudden air losses in tubeless tyres on tight bends and when air pressure is low. A tubeless tyre is shown in Fig5.

Types of rim mounting holes

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Asymmetric rims are used in agricultural machines and construction machinery. These vehicles manly have rims with a broadened well−base. They are also called wide−base rims. In order to gain more space for the brakes the well−base is shifted asymmetrically to the outer rim flange. The 15 tapered rim is undivided, but has a particularly strongly inclined bead. The inclination is 15°. This type of rim is used in lorries. The rim is linked to the wheel hub by the wheel disc, but it is disconnectable. The rim diameter must always be larger than the wheel hub diameter. In the wheel disc there are clearance holes which are standardised. In Fig. 5 these clearance holes are shown. When mounting the wheel at the wheel hub you must ensure that the wheel nuts correspond to the clearance holes so that the wheel fits firmly and safely. Then wheel nuts can loosen when stressed and loaded. Centring of the wheel on the wheel hub can be done either by means of the wheel nuts or centring pins. Another method of centring is the use of a centre hole in the wheel disc. Holes and slots are made in the wheel disc to cool the brakes. The wheel nuts and the axle nuts can be covered by a hub cap. Tyres The tyres of the vehicle are intended to moderate the effects of uneven road surfaces, to improve the driving qualities and to make high speeds possible by low ground friction. Today pneumatic types are used exclusively. The rubber tyre tread is to guarantee that the tyres have a good road grip and protect the vehicle against skidding and side−slipping. To obtain a good road grip various tread patterns are available. The term 'tyre' includes the rim band, the tube and the tyre. The rim band is put between the rim and the tube to prevent friction between them. Such friction would lead to the premature destruction of the tube. The tyres used in modern vehicles are mostly low−pressure tyres. They are elastic and tend not to sink into the ground. The tread pattern should guarantee a good grip on the road. The lateral grooves on the tread help to prevent skidding, and the transversal grooves improve motion. Grip can be improved by narrow lateral and transversal grooves. Pneumatic tyres consist of several rubberised cord plies and the rubberised tread. These two sections are connected by vulcanisation, i.e. heat treatment under pressure.

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Tyre types Tires basically fall into two categories of construction: (1) bias, and (2) radial The cords of the plies in a bias-ply tire run diagonally from bead to bead. This results in a tire with good sidewall strength, a smooth ride, and adequate handling. Bias-ply tires also are cheaper to manufacture. However, bias-ply tires suffer from tread squirm, and they run hotter than other types of tire. This results in increased wear and a higher potential for failure. Initially, the cord materials were natural materials, such as cotton or linen. The first manmade material to be used was rayon, and this was super ceded by nylon (Woehrle, 1995a). Nylon eventually died out due to its tendency for "flat spotting" (Woehrle,

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1995a). When a car with nylon-reinforced tires remained stationary for even a brief time, the tire would deform. The deformity would remain for only a short distance when the car was driven, but until the tire regained its round shape, it produced an annoying thump. In a competitive market, this resulted in a poor first impression and hurt the sales of cars so equipped. A Follow-on to the bias-ply tire was the belted bias tire. This tire contained the usual bias plies, but they were reinforced with circumferential belts, initially made of Fiberglass (Woehrle, 1995a). These tires ran cooler than regular bias-ply tires and provided better tread life and stopping power. However, they also produced a stiffer ride and were more expensive than bias-ply tires. The other category of tire construction is the radial tire. The plies in this tire ran directly across the tire from bead to bead. Radial tires provide the longest tread life because they run cooler, and they also provide excellent grip. They are more expensive than bias-ply tires, and the softer sidewall is more susceptible to punctures. Furthermore, radial tires exhibit lower rolling resistance, which translates into increased fuel economy for the vehicle. Radial tires require some type of circumferential belt for reinforcement. Fiberglass has been used, but the most popular choice has been steel belts.

Functions of tyres Tires play an important role as an automobile component. Many parts may make up a car but usually one part is limited to one function. Despite its simple appearance, a tire differs from other parts in that it has numerous functions.

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Thus, a tire supports the weight of the car, reduces the impact from the road and at the same time, transmits the power to propel, brake and steer on the road. It also functions to maintain a car’s movement. In order to complete such tasks, a tire must be structured to be a resilient vessel of air. A tube is used to maintain its major function of maintaining air pressure but a tube alone cannot maintain the high pressure needed to withstand the great weight. In addition, the tube lacks the strength to withstand all of the exterior damage and impact from driving on the road. The carcass is entrusted with this function. The carcass is an inner layer that protects the tube that contains the high-pressure air and supports vertical load. A thick rubber is attached to the parts that meet the road to withstand exterior damage and wear. Tread patterns are chosen according to car movement and safety demands. A solid structure is necessary to make sure the tires are securely assembled onto rims. According to improvements in automobile quality and capability as well as the diversification of usage, the capabilities and performance of tires are becoming more complex and diversified.

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Unit 3) Steering System Steering Gears One of the important human interface systems in the automobile is the steering gear. The steering gear is a device for converting the rotary motion of the steering wheel into straight line motion of the linkage. The steering gears are enclosed in a box, called the steering gear box. The steering wheel is connected directly to the steering linkage it would require a great effort to move the front wheels. Therefore to assist the driver, a reduction system is used.

The different types of steering gears are as follows:

1. Worm and sector steering gear. 2. Worm and roller steering gear. 3. Cam and double lever steering gear. 4. Worm and ball bearing nut steering gear.

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5. Cam and roller steering gear. 6. Cam and peg steering gear. 7. Recirculating ball nut steering gear. 8. Rack and pinion steering gear.

Under steer and Over steer Understeer and oversteer are vehicle dynamics terms used to describe the sensitivity of a vehicle to steering. Simply put, oversteer is what occurs when a car turns (steers) by more than (over) the amount commanded by the driver. Conversely, understeer is what occurs when a car steers less than (under) the amount commanded by the driver. Automotive engineers define understeer and oversteer based on changes in steering angle associated with changes in lateral acceleration over a sequence of steady-state circular turning tests. Car and motorsport enthusiasts often use the terminology more generally in magazines and blogs to describe vehicle response to steering in all kinds of maneuvers.

Understeer: the car does not turn enough and leaves the road

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Oversteer: the car turns more sharply than intended and could get into a spin

Wheel Alignment: Wheel alignment, sometimes referred to as breaking or tracking, is part of standard automobile maintenance that consists of adjusting the angles of the wheels so that they are set to the car maker's specification. The purpose of these adjustments is to reduce tire wear, and to ensure that vehicle travel is straight and true (without "pulling" to one side). Alignment angles can also be altered beyond the maker's specifications to obtain a specific handling characteristic. Motorsport and off-road applications may call for angles to be adjusted well beyond "normal" for a variety of reasons. WHAT IS CAMBER, TOE, CASTER, AND OFFSET? Maintaining proper alignment is fundamental to preserving both your car’s safety and its tread life. Wheel alignments ensure that all four wheels are consistent with each other and are optimized for maximum contact with the surface of the road. The way a wheel is oriented on your car is broken down to three major components; camber, caster, and toe.

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Camber The most widely discussed and controversial of the three elements is camber. Camber angle is the measure in degrees of the difference between the wheels vertical alignment perpendicular to the surface. If a wheel is perfectly perpendicular to the surface, its camber would be 0 degrees. Camber is described as negative when the top of the tires begin to tilt inward towards the fender wells. Consequently, when the top of the tires begin to tilt away from the vehicle it is considered positive. Negative camber is becoming increasingly more popular because of its visual appeal. The real advantages to negative camber are seen in the handling characteristics. An aggressive driver will enjoy the benefits of increased grip during heavy cornering with negative camber. During straight acceleration however, negative camber will reduce the contact surface between the tires and road surface. Regrettably, negative camber generates what is referred to as camber thrust. When both tires are angled negatively they push against each other, which is fine as long as both tires are in contact with the road surface. When one tire loses grip, the other tire no longer has an opposing force being applied to it and as a result the vehicle is thrust towards the wheel with no traction. Zero camber will result in more even tire wear over time, but may rob performance during cornering. Ultimately, optimal camber will depend upon your driving style and conditions the vehicle is being driven in.

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Caster Caster is a bit harder to conceptualize, but it’s defined as the angle created by the steering pivot point from the front to back of the vehicle. Caster is positive if the line is angled forward, and negative if backward. Typically, positive caster will make the vehicle more stable at high speeds, and will increase tire lean when cornering. This can also increase steering effort as well. Most road vehicles have what is called cross-caster. Cross castered vehicles have slightly different caster and camber, which cause it to drift slightly to the right while rolling. This is a safety feature so that un-manned vehicles or drivers who lose steering control will drift toward the side of the road instead of into oncoming traffic.

Toe Perhaps the easiest concept to visualize is toe. Toe represents the angle derived from pointing the tires inward or outward from a top-down view – much like looking down at your toes and angling them inward or outward. Correct toe is paramount to even tread wear and extended tire life. If the tires are pointed inward or outward, they will scrub against the surface of the road and cause wear along the edges. Sometimes however, tread life can be sacrificed for performance or stability Positive toe occurs when the front of both tires begins to face each other. Positive toe permits both wheels to constantly generate force against one another, which reduces turning ability. However, positive tow creates straighter driving characteristics.

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Typically, rear wheel drive vehicles have slightly positive tow in the rear due to rolling resistance – causing outward drag in the suspension arms. The slight positive toe straightens out the wheels at speed, effectively evening them out and preventing excessive tire wear. Negative toe is often used in front wheel drive vehicles for the opposite reason. Their suspension arms pull slightly inward, so a slight negative toe will compensate for the drag and level out the wheels at speed. Negative toe increases a cars cornering ability. When the vehicle begins to turn inward towards a corner, the inner wheel will be angled more aggressively. Since its turning radius is smaller than the outer wheel due to the angle, it will pull the car in that direction. Negative toe decreases straight line stability as a result. Any slight change in direction will cause the car to hint towards one direction or the other. Conclusion Vehicles are designed with manufacturer’s settings for a reason. Countless hours of research and development go into designing suspension components and typically those numbers are the best to go with. Attempting to differ from the norm may result in dangerous conditions, especially for public road vehicles. As a tuner, your needs and desires may differ from the norm. In this case, be sure to exercise caution when modifying your suspension and to consult professionals prior to any major modifications. Bear in mind the differing results caused by altering your camber, caster and toe, and to remember that performance often comes at the cost of economy.

Power Steering

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There are a couple of key components in power steering in addition to the rack-andpinion or recirculating-ball mechanism.

Pump The hydraulic power for the steering is provided by a rotary-vane pump (see diagram below). This pump is driven by the car's engine via a belt and pulley. It contains a set of retractable vanes that spin inside an oval chamber. As the vanes spin, they pull hydraulic fluid from the return line at low pressure and force it into the outlet at high pressure. The amount of flow provided by the pump depends on the car's engine speed. The pump must be designed to provide adequate flow when the engine is idling. As a result, the pump moves much more fluid than necessary when the engine is running at faster speeds. The pump contains a pressure-relief valve to make sure that the pressure does not get too high, especially at high engine speeds when so much fluid is being pumped. Rotary Valve A power-steering system should assist the driver only when he is exerting force on the steering wheel (such as when starting a turn). When the driver is not exerting force (such as when driving in a straight line), the system shouldn't provide any assist. The device that senses the force on the steering wheel is called the rotary valve. The key to the rotary valve is a torsion bar. The torsion bar is a thin rod of metal that twists when torque is applied to it. The top of the bar is connected to the steering

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wheel, and the bottom of the bar is connected to the pinion or worm gear (which turns the wheels), so the amount of torque in the torsion bar is equal to the amount of torque the driver is using to turn the wheels. The more torque the driver uses to turn the wheels, the more the bar twists. The input from the steering shaft forms the inner part of a spool-valve assembly. It also connects to the top end of the torsion bar. The bottom of the torsion bar connects to the outer part of the spool valve. The torsion bar also turns the output of the steering gear, connecting to either the pinion gear or the worm gear depending on which type of steering the car has.

As the bar twists, it rotates the inside of the spool valve relative to the outside. Since the inner part of the spool valve is also connected to the steering shaft (and therefore to the steering wheel), the amount of rotation between the inner and outer parts of the spool valve depends on how much torque the driver applies to the steering wheel. When the steering wheel is not being turned, both hydraulic lines provide the same amount of pressure to the steering gear. But if the spool valve is turned one way or the other, ports open up to provide high-pressure fluid to the appropriate line. It turns out that this type of power-steering system is pretty inefficient. The Future of Power Steering Since the power-steering pump on most cars today runs constantly, pumping fluid all the time, it wastes horsepower. This wasted power translates into wasted fuel.

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You can expect to see several innovations that will improve fuel economy. One of the coolest ideas on the drawing board is the "steer-by-wire" or "drive-by-wire" system. These systems would completely eliminate the mechanical connection between the steering wheel and the steering, replacing it with a purely electronic control system. Essentially, the steering wheel would work like the one you can buy for your home computer to play games. It would contain sensors that tell the car what the driver is doing with the wheel, and have some motors in it to provide the driver with feedback on what the car is doing. The output of these sensors would be used to control a motorized steering system. This would free up space in the engine compartment by eliminating the steering shaft. It would also reduce vibration inside the car. General Motors has introduced a concept car, the Hy-wire, which features this type of driving system. One of the most exciting things about the drive-by-wire system in the GM Hy-wire is that you can fine-tune vehicle handling without changing anything in the car's mechanical components -- all it takes to adjust the steering is some new computer software. In future drive-by-wire vehicles, you will most likely be able to configure the controls exactly to your liking by pressing a few buttons, just like you might adjust the seat position in a car today. It would also be possible in this sort of system to store distinct control preferences for each driver in the family. In the past fifty years, car steering systems haven't changed much. But in the next decade, we'll see advances in car steering that will result in more efficient cars and a more comfortable ride.

STEERING GEOMETRY Definition: The group of design variables outside the steering mechanism that affect steering behavior, including camber, caster, linkage arrangement, ride steer, scrub radius, toe-in, and trail.

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Wheel Balancing Wheel balancing, also known as tire balancing, is the process of equalizing the weight of the combined tire and wheel assembly so that it spins smoothly at high speed. Balancing involves putting the wheel/tire assembly on a balancer, which centers the wheel and spins it to determine where the weights should go. But Why? The need to balance your wheels is just part of the general maintenance every car requires. As tyres wear, the distribution of weight around their circumference becomes uneven. Eventually, even if the wheel was perfectly balanced to start with, this change in weight will cause the wheel to become unbalanced. But your tyres don’t look too bad? An imbalance of as little as 30 grams can cause a noticeable vibration at 100 kph. Mechanics generally recommend balancing all four wheels every 20,000 kilometers as a matter of course. New Tyres Need Balancing Too Whenever you buy a new tyre the tyre technician should balance it as part of the fitting process. A new tyre may look perfectly round and evenly balanced, but there are small variations in weight around its circumference that must be corrected for. And the tyre isn’t the only factor that must be taken into consideration – your wheel rim, too, will contribute its own set of imbalances.

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Other Causes of Imbalance Hitting a pothole or a curb with your tyre or rim can throw out a previously balanced wheel. Wheel impacts and the normal stresses of driving may cause a wheel balancing weight to become dislodged. If this happens you are likely to experience the immediate onset of vibration. Does it really Matter? You can live with the vibration? You don’t do much motorway driving anyhow? Unbalanced wheels will still be affecting your car in ways that may end up costing you a lot more than a wheel balance would:      

Accelerated and uneven tyre wear. Undue stressing of your car’s suspension. Damage to steering components. Driver fatigue. Impaired tyre traction and steering control. Increased fuel consumption.

The Wheel Balancing Process When you take your car for a wheel balancing, the mechanic will remove the wheels and place them one by one on a machine which spins them and measures the amount and location of the imbalance. A small weight will then be attached to the rim of the wheel to even out the weight distribution and bring the wheel back into balance. The end result of wheel balancing will be a smoother, less tiring ride, a safer car, lower fuel bills and tyres that last longer. It’s worth doing. An Environmental Note Wheel balancing weights which fall from cars and trucks are one of the largest remaining sources of unregulated lead pollution. As lead is a soft metal, they break down in the environment and the lead dust finds its way into the atmosphere, soil and waterways. A simple way to eliminate this source of toxic metal pollution is to use alternative metals such as zinc or steel to fabricate wheel balancing weights. Lead balancing weights have been outlawed in Europe since 2005.

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Centre Point Steering Relative steered-wheel positioning to the swivel axis so that coincidence is obtained between the intersection point of the swivel axis with both the road and wheel plane.

Steerability: The ability of vehicle to steer is called steerability

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UNIT 4) BRAKES Brakes: A brake is a mechanical device which inhibits motion. The rest of this article is dedicated to various types of vehicular brakes.

Necessity of brakes: Most commonly brakes use friction to convert kinetic energy into heat, though other methods of energy conversion may be employed. For example regenerative braking converts much of the energy to electrical energy, which may be stored for later use. Other methods convert kinetic energy into potential energy in such stored forms as pressurized air or pressurized oil. Eddy current brakes use magnetic fields to convert kinetic energy into electric current in the brake disc, fin, or rail, which is converted into heat. Still other braking methods even transform kinetic energy into different forms, for example by transferring the energy to a rotating flywheel. Brakes are generally applied to rotating axles or wheels, but may also take other forms such as the surface of a moving fluid (flaps deployed into water or air). Some vehicles use a combination of braking mechanisms, such as drag racing cars with both wheel brakes and a parachute, or airplanes with both wheel brakes and drag flaps raised into the air during landing. Brakes are often described according to several characteristics including: 





Peak force – The peak force is the maximum decelerating effect that can be obtained. The peak force is often greater than the traction limit of the tires, in which case the brake can cause a wheel skid. Continuous power dissipation – Brakes typically get hot in use, and fail when the temperature gets too high. The greatest amount of power (energy per unit time) that can be dissipated through the brake without failure is the continuous power dissipation. Continuous power dissipation often depends on e.g., the temperature and speed of ambient cooling air. Fade – As a brake heats, it may become less effective, called brake fade. Some designs are inherently prone to fade, while other designs are relatively immune. Further, use considerations, such as cooling, often have a big effect on fade.

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Smoothness – A brake that is grabby, pulses, has chatter, or otherwise exerts varying brake force may lead to skids. For example, railroad wheels have little traction, and friction brakes without an anti-skid mechanism often lead to skids, which increases maintenance costs and leads to a "thump thump" feeling for riders inside. Power – Brakes are often described as "powerful" when a small human application force leads to a braking force that is higher than typical for other brakes in the same class. This notion of "powerful" does not relate to continuous power dissipation, and may be confusing in that a brake may be "powerful" and brake strongly with a gentle brake application, yet have lower (worse) peak force than a less "powerful" brake. Pedal feel – Brake pedal feel encompasses subjective perception of brake power output as a function of pedal travel. Pedal travel is influenced by the fluid displacement of the brake and other factors. Drag – Brakes have varied amount of drag in the off-brake condition depending on design of the system to accommodate total system compliance and deformation that exists under braking with ability to retract friction material from the rubbing surface in the off-brake condition. Durability – Friction brakes have wear surfaces that must be renewed periodically. Wear surfaces include the brake shoes or pads, and also the brake disc or drum. There may be tradeoffs, for example a wear surface that generates high peak force may also wear quickly. Weight – Brakes are often "added weight" in that they serve no other function. Further, brakes are often mounted on wheels, and unsprung weight can significantly hurt traction in some circumstances. "Weight" may mean the brake itself, or may include additional support structure. Noise – Brakes usually create some minor noise when applied, but often create squeal or grinding noises that are quite loud.

Stopping Distance and Time of vehicle Highway traffic and safety engineers have some general guidelines they have developed over the years and hold now as standards. As an example, if a street surface is dry, the average driver can safely decelerate an automobile or light truck with reasonably good tires at the rate of about 15 feet per second (fps). That is, a driver can slow down at this rate without anticipated probability that control of the vehicle will be lost in the process.

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The measure of velocity is distance divided by time (fps), stated as feet per second. The measure of acceleration (or deceleration in this case) is feet per second per second. That assumes a reasonably good co-efficient of friction of about .75; better is .8 or higher while conditions or tire quality might yield a worse factor of .7 or lower. No matter the velocity, that velocity is reduced 15 fps every second. If the initial velocity is 60 mph, 88 fps, after 1 second elapsed, the vehicle velocity would be 73 fps, after 2 seconds it would be 58 fps decreasing progressively thereafter. For the true mathematical perfectionist (one who carries PI to 1000 decimal places), it would have been technically correct to indicated the formula is 'fpsps' rather than 'fps', but far less understandable to most drivers. Since at speeds of 200 mph or less, the difference from one method to the other is in thousandths of seconds, our calculations in these examples are based on the simple fps calculations. Given the previous set of conditions, it would mean that a driver could stop the described vehicle in a total of 6.87 seconds (including a 1 second delay for driver reaction) and your total stopping distance would be 302.28 feet, slightly more than a football field in length! Virtually all current production vehicles' published road braking performance tests indicate stopping distances from 60 mph that are typically 120 to 140 feet, slightly less than half of the projected safety distances. While the figures are probably achievable, they are not realistic and certainly not average; they tend to be misleading and to those that actually read them, they create a false sense of security. By increasing braking skills, drivers can significantly reduce both the time it takes to stop and the distance taken to stop a vehicle. Under closed course conditions, professional drivers frequently achieve 1g deceleration (32 fpsps) or better. A reasonably skilled driver could easily get deceleration rates in excess of 20 fpsps without loss of control. It is very possible and probable that with some effort, the driver that attempts to be aware of braking safety procedures and practices can and should get much better braking (safely) than the guidelines used nationally, approaching that of the professionally driver published performance tests.

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To determine how long it will take a driver to stop a vehicle, assuming a constant rate of deceleration, the process is to divide the initial velocity (in fps) by the rate of deceleration. 60 MPH = 88 fps. (Fps=1.467 * MPH). If the vehicle deceleration rate is 20 fpsps (rather than the previously calculated 15 fps), then stopping time = 88/20 = 4.4 seconds. Since there is a 1 second delay (driver reaction time) in hitting your brakes (both recognition and reaction time is often 2 seconds), the total time to stop is 5.4 seconds to 6.4 seconds. To determine how far the vehicle will travel while braking, use the formula of 1/2 the initial velocity multiplied by the time required to stop. In this case, this works out to be .5 * 88 * 4.4 = 193.6 feet, plus a reaction time of either 88 feet for a second delay in reaction time, or 176 feet for two seconds reaction time. That yields 281.6 feet or 369.6 when added to the base stopping distance of 193.6 feet. If the driver is very responsive and takes only a half a second to react, the distance is reduced to 237.6 feet. Notice that the reaction time is a huge factor since it is at initial velocity. Based on pure math, it is evident that there is a very large difference in the reported performance tests and reality. Assuming a deceleration rate of 32 fpsps (1g), calculations indicate a braking stop time of 2.75 seconds (88/32). Distance traveled now is calculated to be 121 feet, which is for all practical purposed, the published performance figures, excluding reaction times. The intelligent driver will error on the safe side and leave room for reaction time and less than perfect conditions. That driver will also hone the braking skills to give more of a margin of safety. That margin can save lives. The table shows typical stopping distances included in the Highway Code Speed (mph)

20

30

40

50

60

70

80

Thinking Distance (m)

6

9

12

15

18

21

24

Braking Distance (m)

6

14

24

38

54

75

96

Total Stopping Distance (m)

12

23

36

53

72

96

120

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Brake efficiency: Braking efficiency is the breaking effort as a percentage of the weight of the vehicle. It calculates how useful your brakes are when you lightly and heavily tap on them. To calculate you're

your vehicles brake efficiency a mechanic uses a tire machine that automatically rotates your tires, and then suddenly stops them as you would when driving. He then divides the vehicle's weight by the total brake effort, and then multiplies the result by 100 to get the brake efficiency percentage. Table for brake efficiency Classes 3,4 & 7

Minimum Brake Efficiencies Required

Vehicles with 4 or more wheels having a

Service

service brake (foot-brake) operating on at

Brake

Parking Brake

least 4 wheels and a parking (handbrake)

Vehicle

Vehicle

operating on at least 2 wheels.

with a

with a split

single line

(dual)

braking

braking

system

system

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Vehicles with 3 wheels with a service brake

50%

25%

16%

i. before 1 January 1968

40%

25%

16%

ii. on or after 1 January 1968

50%

25%

16%

Vehicles first used before 1 January 1968

30% for

25% for second means of

which do NOT have one means of control

first

control

operating on ALL wheels and a parking brake operating on at least one wheel which were first used:

operating on at least 4 wheels (or 3 for three means of wheeled vehicle) and which have one brake

control

system with two means of control or two brake systems with separate means of control. Vehicles first used before 1 January 1915

One efficient braking system required

Class 5

Minimum Brake Efficiencies Required Parking Brake Service

Vehicle with

Brake

a single line Vehicle with a split (dual) braking

braking system

system

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Buses first used on or after 1 January 1968 Buses first used before 1 January 1968

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50%

25%

45%

20%

16% No Specific Requirement (see Note 1)

Note 1: On vehicles first used before 1 January 1968 having a dual braking system, the parking brake must be capable of preventing at least two wheels from rotating when the vehicle is stationary. There is no specified efficiency requirement. Note 2: 16% parking brake efficiency equates to a vehicle holding on a gradient of 1 in 6.25

Weight transfer A vehicle faces weight transfer problem in the time of braking. The inertia force acts at the centre of gravity of vehicle, while the retarding force due to the application of brakes acts at road surface. These two form an overturning couple.

This overturning couple increases the perpendicular force between the front wheels and the ground by an amount R (normal reaction at front wheel) and perpendicular force

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between the rear wheels and the ground is decreased by an equal amount. Some of the vehicle weight is thus transferred from the rear side to front axle.

It is thus observed that in vehicles where either the distribution of weight over two axles is equal, or the front axle carries more weight, the braking effect has to be more at front wheels for efficient braking. It is seen that in general for achieving maximum efficiency, about 75% of the total braking effect should be on the front wheels. However, in such a case the trouble would arise while travelling over wet road, where high braking effect on front would cause the skidding of the front wheels, because of decreasing of weight transfer. In practice, about 60% of the braking effect is applied on the front wheels.

Brake Systems Theory The basic function of the brake system in a vehicle is to convert Kinetic Energy into Heat Energy. This is done by the brake system converting momentum of the vehicle into heat energy at the brakes through the moving brake rotor/drum and a frictional material, better known as brake pads/shoes. It should be known that energy cannot be destroyed; only converted. Thus once we convert the momentum of a vehicle or Kinetic Energy into Heat Energy through brake application or friction, a vehicle will come to a stop and is held in place by Static Friction. Static Friction can also be referred to as Pressure and the road we drive is a form of Static Friction. There are four factors that determine the effectiveness of the braking system. The first three are factors of friction (Pressure, Coefficient of Friction (COF) and Frictional Contact

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Surface). The forth is a result of the first three which is created as a result, Heat or Heat Dissipation.

-Pressure, the greater the pressure that is applied by the braking system the more heat friction which will develop at the brake units. This is achieved by brake pedal force though hydraulic pressure multiplication of the master cylinder to the braking system via the brake lines and fluid. -Coefficient of Friction (COF) is the amount of friction generated between two surfaces, or the relationship between the frictional brake pads/shoes and the brake rotors/drums. COF can be expressed as a mathematical equation that is used to determine frictional material’s effectiveness to stop a vehicle. COF is determined by dividing the force required to pull an object across a surface by the weight of the object. So if you have a 100 pound object and it requires 100 pounds of force to pull that object, the equation would be 100 divided by 100 for a COF of 1. -Frictional Contact Surface is the amount of surface area in contact with the frictional brake material while braking. Simply stated, that the larger a vehicles brakes are the easier it is to stop then smaller brakes. -Heat Dissipation is the biggest factory in the effectiveness in a vehicles ability to stop safely. A brake system must be designed properly to conduct the heat away from the pads/shoes and rotors/drums and be absorbed into the surrounding air. The inability to properly dissipate heat will result in Brake Fade and loss of braking power with longer stopping distances.

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Brake Fade is commonly caused by excessive heat buildup during braking. The brake pedal will feel normal, but the ability to stop is drastically reduced. During braking and as heat is generated from the friction, the pad/shoe linings generate a gas. This result is called out-gassing or off-gassing. This gas can quickly form an air gap between the frictional material and the braking surface. As brake pressure is applied, the clamping force will slip on the gas, and this in known as brake fade. It should also be known, that Brake Fade can also be caused if, brake fluid (which is hygroscopic) absorbs too much moisture and its boiling point is lowered, causing a gas in the fluid from excessive heat buildup. Fluid is not compressible, but gas in the fluid can easily be compressed.

Determination of Braking Torque Torque is a force exerted on an object; this force tends to cause the object to change its speed of rotation. A car relies on torque to come to a stop. The brake pads exert a frictional force on the wheels, which creates a torque on the main axle. This force impedes the axle's current direction of rotation, thus stopping the car's forward movement.



Draw a free-body diagram. A free-body diagram isolates one object and replaces all external objects with vector or torsional forces. This allows you to sum forces and determine the net force and torque acting on an object.



Show all forces acting on the vehicle as the driver begins to brake. There is the downward force of gravity, and there is also the upward force exerted by the road. These two forces are equal and opposite, so they cancel each other out. The remaining force is the frictional force exerted by the road, which acts horizontally in the direction opposite to the vehicle's motion. As an example, suppose you are analyzing a 2,000 kilogram Jeep that has just begun braking. Your diagram would

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show two equal and opposite vertical forces of 19,620 Newtons, which sum up to zero, and some undetermined horizontal force. 

Determine the horizontal force of the road using Newton's second law--the force on an object equals its mass times its acceleration. You presumably either know or can obtain the weight of the vehicle from manufacturer specifications, but you will need to calculate the rate of deceleration. One of the simplest ways to do this is to assume an average rate of deceleration from the time the brakes are first applied, to the point of release. The deceleration is then the total change in speed divided by the time that elapsed during the braking process. If the Jeep went from a speed of 20 meters per second down to 0 meters per second in 5 seconds, so its average deceleration would be 4 meters per second per second. The force required to cause this deceleration equals 2,000 kg * 4 m/s/s, which equals 8,000 Newtons.



Calculate the torque that the force of the road causes about the axle. Because torque equals force times its distance from the point of rotation, the torque equals the force of the road times the radius of the wheel. The force of the road is the equal and opposite torsional reaction caused by the brakes, so the braking torque is equal in magnitude and opposite in direction to the torque exerted by the road. If the Jeep's wheel has a radius of 0.25 meters, the braking torque equals 8,000 N * 0.25 m, or 2,000 Newton-meters.

Types of Braking Systems Records show that in 1901, a British inventor named Frederick William Lanchester patented the first type of brake, known as the disc brake. Since this time, there have been many braking system types created for our safety. The brake was created to make our vehicle stop in time to avoid accidents by inhibiting the motion of the vehicle. In most automobiles there are three basic types of brakes including; service brakes, emergency brakes, and parking brakes. These brakes are all intended to keep everyone inside the vehicle and traveling on our roadways safe. If you or a member of your family has been injured in a car accident, the victim may be entitled to receive compensation for their losses and damages including; loss of wages, medical expenses, pain and suffering, and property damage. Common Braking System Types The most common types of brakes found in automobiles today are typically described as hydraulic, frictional, pumping, electromagnetic, and servo. Of course, there are several

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additional components that are involved with make braking smooth and more effective depending on road conditions and different circumstances. Some common types of braking systems include:  Electromagnetic Brakes Electromagnetic brakes use an electric motor that is included in the automobile which help the vehicle come to a stop. These types of brakes are in most hybrid vehicles and use an electric motor to charge the batteries and regenerative brakes. On occasion, some busses will use a secondary retarder brake which uses an internal short circuit and a generator.  Frictional Brakes Frictional brakes are a type of service brake found in many automobiles. They are typically found in two forms; pads and shoes. As the name implies, these brakes use friction to stop the automobile from moving. They typically include a rotating device with a stationary pad and a rotating weather surface. On most band brakes the shoe will constrict and rub against the outside of the rotating drum, alternatively on a drum brake, a rotating drum with shoes will expand and rub against the inside of the drum.  Pumping Brakes Pumping brakes are used when a pump is included in part of the vehicle. These types of brakes use an internal combustion piston motor to shut off the fuel supply, in turn causing internal pumping losses to the engine, which causes braking.  Hydraulic Brakes Hydraulic brakes are composed of a master cylinder that is fed by a reservoir of hydraulic braking fluid. This is connected by an assortment of metal pipes and rubber fittings which are attached to the cylinders of the wheels. The wheels contain two opposite pistons which are located on the band or drum brakes which pressure to push the pistons apart forcing the brake pads into the cylinders, thus causing the wheel to stop moving. Servo Brakes Servo brakes are found on most cars and are intended to augment the amount of pressure the driver applies to the brake pedal. These brakes use a vacuum in the inlet manifold to generate extra pressure needed to create braking. Additionally, these braking systems are only effective while the engine is still running. In some vehicles we may find that there are more than one of these braking systems included. These systems can be used in unison to create a more reliable and stronger braking system. Unfortunately, on occasion, these braking systems may fail resulting in automobile accidents and injuries.



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Parking and Emergency Braking Systems Parking and emergency braking systems use levers and cables where a person must use mechanical force or a button in newer vehicles, to stop the vehicle in the case of emergency or parking on a hill. These braking systems both bypass normal braking systems in the event that the regular braking system malfunctions. These systems begin when the brake is applied, which pulls a cable that passes to the intermediate lever which causes that force to increase and pass to the equalizer. This equalizer splits into two cables, dividing the force and sending it to both rear wheels to slow and stop the automobile. In many automobiles, these braking systems will bypass other braking systems by running directly to the brake shoes. This is beneficial in the case that your typical braking system fails.

Hydraulic Brakes It consists of following main parts: (i) Master cylinder (ii) Wheel cylinder (iii) Brake fluid (or brake oil) pipelines. It consists of a master cylinder which is connected to four cylinders through a pipeline. The wheel cylinder consists of brakes and shoe arrangement.

Principle: It works on the principle of Pascal's law, which states that "The confined liquid transmits pressure intensity equally in all directions."

Working: When the driver depresses pedal, the effort is transmitted through rod to piston of master cylinder. The piston moves in the cylinder and compress return spring forcing out the fluid from the cylinder into brake line through a by-pass. Piston of a brake cylinders are acted upon by the fluid and press against shoes, bringing their linings tightly against the working surfaces of the drums as soon as the pedal is released, the return spring pushes piston back. At the same time, the compression springs of the brake shoe move pistons to their initial position and the fluid begins to the flow in the reverse direction.

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Hydraulic braking system Types of Brake Master Cylinders #Single-Cylinder Single-cylinders are the most basic type of master cylinder, and are internally very similar to a plastic medical syringe. The brake pedal lever pushes the plunger (piston) inside the cylinder, which shoves fluid through the lines and into the slave cylinders. When the brake pedal is released, a spring inside of the cylinder pushes the plunger back to its original position. Negative pressure pulls the brake fluid into the cylinder from the lines and from the brake fluid reservoir. Automakers long ago switched to the more redundant tandem master cylinder, but many race car builders prefer to use a pair of single cylinders instead of a single tandem cylinder to control front/rear brake pressure bias. #Ported Tandem Cylinder A tandem cylinder is two pistons in one. The primary piston is connected to the brake pedal. When the brake pedal is pressed, the piston pushes on a spring connected to the back of the secondary piston. Once that spring compresses fully, the secondary piston starts to push fluid through its own dedicated system. The reservoir inlet port allows fluid to flow behind the pistons to keep pressure even on both sides. When the brake pedal is released, spring pressure pushes the pistons back and a small compensating port from the brake fluid reservoir introduces extra fluid into the chamber. The compensating port is necessary to speed up brake release, which would otherwise be inhibited by the speed of the fluid moving backward through the lines. #Portless Master Cylinder First introduced on the Toyota MR2, portless master cylinders offer quicker brake release than standard designs that utilize a compensating port. Portless cylinders utilize a valve assembly in the pistons that opens to equalize pressure when the brakes are released. This allows the brake cylinder to do without the compensating port, which is more restrictive to fluid flow and bleeds pressure from the brake system under initial application. The quicker-responding portless cylinder works better with anti-lock braking (ABS) systems, which use rapid pressure modulations to adjust braking force. Factors Affecting Braking distance Factors affecting braking distance are speed whereby if you drive at a higher speed, it will take you longer to stop because the number of feet you are covering per second is

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already more than if you were to travel at a lower speed. Another factor is weight and mass of a vehicle in that the heavier and larger your vehicle is, the more momentum and kinetic energy it has to continue moving forward.

Factors affecting brakes 1. Reaction Time When brake efficiency is determined by measuring braking force or deceleration, reaction time is not involved. When either stopping time or distance is measured, depending on the method used, reaction time may influence the measurement. A typical minimum reaction time with an alert driver can be as low as 0.5 sec. If this were included with the actual stopping time, it would influence considerable the estimate of brake efficiency being made. It is important to include reaction time when, for road safety purposes, estimates are being made of stopping distances as in the Highway Code but it must not be allowed to influence tests of the brakes themselves. 2. Braking on Gradients Although it is more usual to conduct brake tests which are carried out on the road on a level surface, equally accurate results can be obtained on a constant incline, the means of making allowance being very simple. The severity of a gradient can be expressed as a decimal by calculating the sine of the angle of the slope which will be a number between 0 and 1. The significance of this result is that it gives the force acting to push the vehicle down the slope as a proportion of the gross weight. For example if a vehicle is standing facing down a 1 in 8 slope, the gradient may be described as 1/8, 0.125 or as 12.5% and the force acting down the slope is 1/8 of the vehicles gross weight. If then the braking efficiency is determined by measuring either deceleration, stopping time or stopping distance, the result will be 0.125 too low and can be corrected to level road conditions by adding 0.125 or 12.5%.Similarly, a rising gradient helps a vehicle stop and the result obtained must be corrected by deducting from it the measure of the gradient.

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3. Weight Transfer Weight transfer during braking varies the axle loading and so affects the adhesion available. It also affects the reading of decelerometers of all types very slightly if the suspension is such that it allows the body of the vehicle to tip forward significantly when transfer takes place. For most vehicles this error may be ignored. 4. Wheel Locking If one of more wheels lock, the overall efficiency recorded will be less than that which would have been indicated if locking had just been avoided. Since, as has already been noted, brake tests should only be made under suitable conditions, this state of affairs should only arise at high decelerations and brakes should be released immediately to avoid unnecessary tyre wear. 5. The Effect of Speed Any effect is very small and the results achieved may be assumed to be independent of the test speed used over the range 0-40 mile/hr (0-64 km/h).

6. Brake Fade True fade is a loss of brake output due to overheating of the brake linings. Modern drum brake linings are little affected by heat until operation temperatures exceed 350440 C while disc brake linings are more heat resistant. To exceed these temperatures a vehicle must be driven very hard and even then the onset of fade is very slow. Brake linings also lose their friction if they become soaked in either hydraulic fluid of lubricating oil, or if linings get wet. Recovery from immersion in water is usually fairly rapid but if linings have become oily they must be replaced and the discs/drums cleaned.

Is it bad if your brake pedal goes to the floor? The brake pedal going all the way to the floor can be caused by a number of different issues. All of the possible causes need to be addressed, even if the car is stopping fine. One of the more common causes for the brake pedal going to the floor is a loss of brake fluid. When you're out of brake fluid, your brakes simply won't work. This is pretty easy to diagnose: You should be able to see brake fluid underneath the car if there's a leak in the system.

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Another possible cause is a bad brake master cylinder. The master cylinder is where brake fluid gets compressed. Pressure on the brake fluid cases the brakes to be applied to the wheels. If your master cylinder doesn't work properly, or only works sometimes, you're going to lose braking power, and occasionally your brake pedal will go all the way to the floor. Here's an additional reason a brake pedal could go all the way to the floor: a bad brake booster. The booster is a mechanism that uses vacuum pressure to take the force being applied to the brake pedal and amplify it. If the booster is bad, then the full amount of force needed to activate the master cylinder and pressurize the brake fluid isn't going to be there. The pedal will go all the way to the floor and the car will be harder to stop. There's one more thing that could be causing the brake pedal to go all the way to the floor: you, the driver. The more the brakes are used, the hotter the brake fluid gets. The hotter the brake fluid gets the more liquid it becomes. It sounds silly, but it's sort of like what happens to Jell-O on a hot day: it goes from a thickish liquid to a thinner liquid. When the brake fluid gets hot and thin, it needs more force to be pressurized enough to operate the brakes; your braking system may not be able to generate the force necessary. So, if your brake pedal frequently goes to the floor and you can't find a mechanical reason, check out your driving style. Make sure you aren't riding the brakes, and always make sure you take off the parking brake before you head out.

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UNIT 5) SUSPENSION Suspension Types: Front So far, our discussions have focused on how springs and dampers function on any given wheel. But the four wheels of a car work together in two independent systems -- the two wheels connected by the front axle and the two wheels connected by the rear axle. That means that a car can and usually does 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 Suspensions 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 springs and shock absorbers. Common on trucks, dependent front suspensions haven't been used in mainstream cars for years.

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Independent Front Suspensions In this setup, the front wheels are allowed to move independently. 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. The 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 frontwheel drive vehicles.

Photo courtesy Honda Motor Co., Ltd. Double-wishbone suspension on Honda Accord 2005 Coupe The double-wishbone suspension, also known as an A-arm suspension, is another common type of front independent suspension. While there are several different possible configurations, this design typically uses two wishbone-shaped arms to locate the wheel. Each wishbone, which has two mounting positions to the frame and one at the wheel, bears a shock absorber and a coil spring to absorb vibrations. Double-wishbone suspensions allow for more control over the camber angle of the wheel, which describes the degree to which the wheels tilt in and out. They also help minimize roll or sway and provide for a more consistent steering feel. Because of these characteristics, the double-wishbone suspension is common on the front wheels of larger cars. Now let's look at some common rear suspensions. Suspension Types: Rear Historical Suspensions Sixteenth-century wagons and carriages tried to solve the problem of "feeling every bump in the road" by slinging the carriage body from leather straps attached to four posts of a chassis that looked like an upturned table. Because the carriage body was suspended from the chassis, the system came to be known as a

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"suspension" -- a term still used today to describe the entire class of solutions. The slung-body suspension was not a true springing system, but it did enable the body and the wheels of the carriage to move independently. Semi-elliptical spring designs, also known as cart springs, quickly replaced the leather-strap suspension. Popular on wagons, buggies and carriages, the semielliptical springs were often used on both the front and rear axles. They did, however, tend to allow forward and backward sway and had a high center of gravity. By the time powered vehicles hit the road, other, more efficient springing systems were being developed to smooth out rides for passengers.

Dependent Rear Suspensions If a solid axle connects the rear wheels of a car, then the suspension is usually quite simple -- based either on a leaf spring or a coil spring. In the former design, the leaf springs clamp directly to the drive axle. The ends of the leaf springs attach directly to the frame, and the shock absorber is attached at the clamp that holds the spring to the axle. For many years, American car manufacturers preferred this design because of its simplicity. The same basic design can be achieved with coil springs replacing the leaves. In this case, the spring and shock absorber can be mounted as a single unit or as separate components. When they’re separate, the springs can be much smaller, which reduces the amount of space the suspension takes up. Independent Rear Suspensions If both the front and back suspensions are independent, then all of the wheels are mounted and sprung individually, resulting in what car advertisements tout as ‚fourwheel independent suspension.‛ Any suspension that can be used on the front of the car can be used on the rear, and versions of the front independent systems described in the previous section can be found on the rear axles. Of course, in the rear of the car, the steering rack – the assembly that includes the pinion gear wheel and enables the wheels to turn from side to side – is absent. This means that rear independent suspensions can be simplified versions of front ones, although the basic principles remain the same. Next, we’ll look at the suspensions of specialty cars.

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Leaf Spring Suspension System: A leaf spring suspension system is made up of one or more long, arched pieces of steel that are made to flex when necessary (like when you hit a bump or put a load in the truck bed) but with an ability to return to their original shape. One end of a leaf spring is attached to the frame, and the other end is attached to a shackle that can move, allowing the spring’s overall length to vary as its arch flexes (when carrying a load or traveling over bumps). Adding more leaf springs allows the system to support more weight – the reason heavier duty trucks have multiple layers of leaf springs.

Leaf spring suspension

Leaf Spring Comfort Factor: A single leaf spring typically doesn’t support as heavy of a load as multiples, but it flexes more freely with the ups and downs of a road, delivering a fairly comfortable ride. A stack of leaf springs supports a heavier load by making it more difficult for the main leaf to flex and preventing the truck from bottoming out. The trade-off is a stiffer ride when the truck bed is empty, because without a load, very little flex takes place.

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Coil Spring Suspension Systems: Coil spring suspension systems are used on the front of most trucks and on the front and back of most cars. Systems typically have a single coil on each side of the vehicle. The coil moves more freely than a leaf spring setup, offering more give and a comfortable ride. Truck Rear Suspension Systems: Manufacturers have traditionally used leaf springs for pickup truck rear suspensions, because they felt that type of system offered the best support for heavy loads.

TORSION BAR SUSPENSION SYSTEM A torsion bar is a type of suspension system that is typically used in wheeled vehicles such as cars, vans and trucks. A suspension system is an important and critical element of a vehicle’s design. Regardless of the design, all suspension systems perform the same important functions. They keep the tires in contact with the surface of the road, support the weight of a vehicle and absorb the forces generated by the movement and motion of the vehicle. Torsion bars are essentially metal bars that function as a spring. At one end, the torsion bar is fixed firmly in place to the chassis or frame of a vehicle. The other end of the bar may be attached to the axle, suspension arm, or a spindle, depending on the specifics of a vehicle’s design. As a vehicle moves along the road, the forces generated by the motion of the vehicle create torque on the bar, which twists it along its axis. Counteracting the torque is the fact that the torsion bar naturally wants to resist the twisting effect and return to its normal state. In doing so, the suspension provides a level of resistance to the forces generated by the movement of the vehicle. This resistance is the key principle behind a torsion bar suspension system. There are several key advantages of this system. The design of the torsion bar suspension takes up less space than other suspension systems. This can allow vehicle designers to create a more spacious passenger compartment. The height of torsion bars can also be adjusted more easily than other suspension systems. They are also extremely durable and traditionally have a long service life.

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There are also several disadvantages of torsion bar suspensions. The first is that torsion bars generally do not offer what is known as a progressive spring rate. In suspensions with a progressive spring, the coils of the spring are spaced at different distances from each other. This allows the suspension system to enable firm steering, braking and handling, while also providing for a smooth and comfortable ride. Vehicles with torsion bars are often tuned to either provide a more firm driving experience at the expense of ride smoothness, or a smoother ride at the expense of the vehicle’s handling quality. Torsion bar suspension systems were once relatively common in passenger vehicles, but today are used primarily for the suspension systems of trucks and sport utility vehicles (SUVs). Some notable automobiles that used a torsion bar suspension were the original Volkswagen Beetle, Porsche 356, Porsche 911 models that utilized an air-cooled engine, and much of the Chrysler line-up of cars from the late 1950s through the late 1980s. Torsion bar suspensions are also commonly used in racing vehicles such as Formula One cars and Sprint Cars.

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Pneumatic Suspension System Air Suspension System Components Early versions of air suspension systems were relatively simple. Air bags replaced the coil springs. The bag was inflated to the correct pressure or height with an outside compressor through a valve on the bag. Changes in technology and use added more components, and control, to the system. But today’s air suspension systems all have a basic stock of similar components that vary little from maker to maker. The differences come mainly in controls and ease of installation. Air bag material has changed little over time. The bag is a composite of rubber and polyurethane, which provides structural integrity, air-tight construction, toughness against light abrasion from road debris and sand, and resistance to salt and chemical corrosion. The bags come in three basic shapes: 

Double-convoluted bag. This bag is shaped like an hourglass. The design allows for a little more lateral flexibility than the other designs.

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Tapered sleeve. This air bag performs the same as any other but is designed to fit in a tighter area and offers a little more adjustability on ride height.



Rolling sleeve. This is also a specific-application air bag. The pertinent differences between the two sleeves are really about ride height and spring control, and what’s best for the vehicle and the application. Most air suspension systems now come with an on-board compressor. The compressor is an electric pump feeding air to the bags through a series of compressed air lines. The compressor is generally mounted on the vehicle’s frame, or in the trunk. The vast majority of compressors come with an attached drier. The compressor works by drawing outside air into the pump, compressing it and moving it to the bags. Outside air is often laden with moisture, and moisture can wreak havoc in a closed system. The drier uses a substance known as a desiccant to absorb as much moisture from the air as possible before the air is sent through the system. Simpler compressor systems rely on the compressor itself to maintain, increase or decrease pressure. More advanced systems add an air tank to maintain pressure and provide an even transition between pressures. Compressors can be activated manually or automatically, and controlled solely by the driver, automatically through an electronic system, or a combination of both.

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Pneumatic suspension system

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Hydraulic suspension system A hydraulic suspension system can be used to make a car actually dance. These are often used in low rider vehicles because the hydraulic suspension system allows the vehicle to be quickly lowered and just as quickly raised. This is accomplished by the use of a bladder that can be filled with fluid; the bladder is attached to a compressor. The compressor shoots the liquid into the bladder which quickly expands causing a small explosion inside the actuator. This explosion pushes hard on the things around it, which forces them to spring away. SHOCK ABSORBERS Dampers: Shock Absorbers

Unless a dampening 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

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built on springs alone would make for an extremely bouncy ride and, depending on the terrain, an uncontrollable car. Enter the shock absorber, or snubber, a device that 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. To understand how this works, it's best to look inside a shock absorber to see its structure and function. A shock absorber is basically an oil pump placed between the frame of the car and the wheels. The upper mount of the shock connects to the frame (i.e., the sprung weight), while the lower mount connects to the axle, near the wheel (i.e., the unsprung weight). In a twin-tube design, one of the most common types of shock absorbers, the upper mount is connected to a piston rod, which in turn is connected to a piston, which in turn sits in a tube filled with hydraulic fluid. The inner tube is known as the pressure tube, and the outer tube is known as the reserve tube. The reserve tube stores excess hydraulic fluid. When the car wheel encounters a bump in the road and causes the spring to coil and uncoil, the energy of the spring is transferred to the shock absorber through the upper mount, down through the piston rod and into the piston. Orifices perforate the piston and allow fluid to leak through as the piston moves up and down in the pressure tube. Because the orifices are relatively tiny, only a small amount of fluid, under great pressure, passes through. This slows down the piston, which in turn slows down the spring. 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 modern shock absorbers are velocity-sensitive -- the faster the suspension moves, the more resistance the shock absorber provides. This enables shocks to adjust to road conditions and to control all of the unwanted motions that can occur in a moving vehicle, including bounce, sway, brake dive and acceleration squat.

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Types of Shock Absorber Although all shock absorbers do the same job, different types of vehicles and suspension designs require different types of shock absorbers which can appear radically different.

No matter the application, all shock absorbers fit into one of three broadly defined types – conventional telescopic shock absorbers, struts or spring seat shocks

Conventional telescopic shock absorbers This is the simplest type of shock absorber and is generally replaced rather than repaired. This type of shock absorber can be found on both front and rear suspension systems and is relatively inexpensive.

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Strut type shock absorbers Although they do the same basic job, struts replace part of the suspension system and must be more ruggedly built to cope with greater loads and forces. Although most commonly seen on the front and rear of small to medium cars, larger cars are now tending towards strut based suspension design. The strut category is further divided into sealed and repairable units. As the name suggests, sealed units are designed to be fully replaced, whilst repairable (McPherson) struts are able to be fitted with replacement strut cartridges Spring seat shocks The spring seat type shows characteristics of both telescopic and strut type shock absorbers. Like struts, a spring seat shock is a suspension unit and damping device in a single unit. Unlike struts however, they are not designed to be subject to high side loads. Built using similar components to conventional shock absorbers, spring seat shocks are also sealed requiring full replacement.

Mechanism Shock absorbers are attached at the end of the piston rod and works against hydraulic fluid in the pressure tube. The movement of the suspension up and down forces the hydraulic fluid through minute holes inside the piston. However only small amount of fluid is forced inside the piston. The insertions of fluid reduce the speed of the piston which in turn slows down the piston, which in turn slows down spring and suspension movement.

The speed of the suspension and the number and size of the orifices in the piston determines the resistance a shock absorber. Nowadays, shock absorbers are made using this principle. That is faster movement of suspension means more resistance shock absorber provides. Shock absorber designed on this basis simply reduces the bounce, Roll or sway and Brake dive and Acceleration squat.

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Shock Absorber Working Principle There are two cycles in which Shock absorber works:

Compression Cycle In the compression cycle the piston moves downward and compresses the hydraulic fluid in the chamber which is situated below the piston. In this cycle or downward movement, the fluid flows to upper chamber from down chamber through piston. Some of the fluid also flows into reserve tube through the compression valve. Flow is controlled by valves in the piston and in the compression valve. Extension cycle In the extension cycle the piston moves upwards toward the top of the pressure tube. The upward movement results in the compressing of the fluid in the chamber lying above the piston. The extension cycle generally provides more resistance than compression cycle.

VIBRATION AND RIDING COMFORT Ride quality refers to the degree of protection offered vehicle occupants from uneven elements in the road surface, or the terrain if driving off-road. A car with very good ride quality is also a comfortable car to ride in. Cars which disturb vehicle occupants with major or minor road irregularities would be judged to have low ride quality. Key factors for ride quality are Whole body vibration and noise. While pleasant, the comfort of the vehicle driver is also important for car safety, both because of driver fatigue on long journeys in uncomfortable vehicles, and also because road disruption can impact the driver's ability to control the vehicle. Early vehicles, like the Ford Model T, with its live axle suspension design, were both uncomfortable and handled poorly. Automakers often perceive providing an adequate degree of ride quality as a compromise with car handling, because cars with firm suspension offer more roll stiffness, keeping the tires more perpendicular to the road. Similarly, a lower center of gravity is more ideal for handling, but low bodywork forces the driver's and passengers'

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legs more forward and less down, and low ground clearance limits suspension travel, requiring stiffer springs. Ride quality is also related to good braking and acceleration on poor surfaces. It protects the car itself, as well as its passengers and cargo, from vibration that might eventually damage or loosen components of the car. On the other hand "poor" ride quality improves blood circulation, helps to keep the driver awake, helps the driver sense speed and road condition and is enjoyed by small children and traditional sports car enthusiasts. Load bearing also interferes with ride quality - the suspension settings are very stiff so the vehicle doesn't change pitch when loaded - most trucks thus do not ride particularly comfortably. In passenger vehicles, self-leveling suspension has been introduced to counteract this effect. Road construction quality and maintenance have a direct impact on ride quality in vehicles. In jurisdictions where all roads are relatively smooth, the passengers are undisturbed already and the vehicle can be optimized for a higher degree of handling. In most industrialized countries, as well as in many development countries, pavement condition is scanned on road network level usinglaser/inertial road Profilometers. The Profilometer records road geometry and condition while driving at highway speed. Results from Profilometry can be used to design an optimal geometric pavement repair, eliminating all long wave unevenness, roughness, erroneous cross slope magnitudes and undesired cross slope variance, with the least road grinding and paving efforts. The outcome is a surface with superior ride quality.

Roll axis of Spring Suspension Roll rate is analogous to a vehicle's ride rate, but for actions that include lateral accelerations, causing a vehicle's sprung mass to roll about its roll axis. It is expressed as torque per degree of roll of the vehicle sprung mass. It is influenced by factors including but not limited to vehicle sprung mass, track width, CG height, spring and damper rates, roll center heights of front and rear, anti-roll bar stiffness and tire pressure/construction. The roll rate of a vehicle can, and usually differs front to rear, which allows for the tuning ability of a vehicle for transient and steady state handling. The roll rate of a vehicle does not change the total amount of weight transfer on the vehicle, but shifts the speed at which and percentage of weight transferred on a particular axle to another axle through the vehicle chassis. Generally, the higher the roll rate on an axle of a vehicle, the faster and higher percentage the weight transfer on that axle.

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UNIT6: MOUNTING Wheel mounting Tire and Wheel Installation Instruction

Care and attention to detail are key concerns whenever dealing with the installation of custom wheels, especially alloy wheels. Taking the time to do the job correctly will greatly reduce the potential for customer complaints. Preparing for wheel installation NOTE: Prior to installing any wheel (steel or alloy), verify the condition of the fastening system’s threads (nuts and studs or bolts and hub threads). All threads should be clean and free of dirt, grease, grit, etc. If burrs or flat spots are found, replace the offending Lug Nut. Before attempting to install the wheel to the vehicle hub, first verify that you have the correct size Lug Nut, and check thread condition. Finger-install all Lug Nuts. Each Lug Nut should be able to be easily threaded into place without the use of a tool. If not, the thread size (diameter or thread pitch) may be incorrect, or thread damage may exist on either the stud and/or nut; or the wheel bolt and/or hub’s threaded hole. Resolve any Lug Nut issues before attempting to install the wheel(s). Please be aware and to see if you have Asymmetrical or Directional tires. It is very important that they are going in the correct rotation. Asymmetrical or Directional tires will always have some type of indication to show which way the tire should rotate, this indication will be on the sidewall of the tire. Here are some samples that show the different types of indicators that tire manufactures use.

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Sample 1

Sample 2

Sample 3 Once you’re satisfied with regard to the Lug Nuts, if this is a first-time installation (new aftermarket wheels), it’s a good idea to first test-fit the wheels before mounting the tires to the wheels. Make sure that no obstructions exist on the hub face that would prevent the wheel from flush-mating to the hub (check for OE stud clips, etc.).

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Install the wheel to the vehicle hub, tightening at least three wheel Lug Nuts. There’s no need to tighten to full torque value, just make sure the wheel fits flush against the hub face. Check for disc brake clearance and for clearance between the wheel rim and any steering/suspension components. Also check hub fit. Some wheels are designed to be centered to the hub by means of the bolt holes (lug-centric), while others are designed to center to the hub via the hub center-to-wheelhub center hole (hub-centric). If the wheel’s center hole is larger than the outer diameter of the hub’s centering housing, a hub-centric ring may be needed to properly center the wheel to the hub. If you don’t see any hub-centric rings with your shipment call your PerformancePlusTire/HotRodHanks.com salesperson and they will send them to you. Hub-centric rings are not always available for some of the older vehicles. There’s nothing wrong with using a hub-centric ring. Some wheel makers may use the same center hole diameter to accommodate a variety of hub sizes. Using a centering ring allows a single center hole size to function on smaller hub diameters. Simply check this first to save time and aggravation. The rings, if needed, must be installed to the hub before the wheel is installed.

Wheel Lug Nut torque Many folks don’t realize it, but all threaded Lug Nuts are intended to stretch slightly when fully tightened to specification. In the case of wheel studs and nuts (or wheel bolts), this creates the correct preload required to properly secure the wheel to the hub. If the wheels Lug Nuts are under-tightened, they will eventually loosen, resulting in wheel damage or separation from the vehicle. If the Lug Nuts are tightened beyond their design limit, the wheel stud or bolt can permanently stretch (fatiguing beyond its designed elastic range) or even break during installation. While the use of an impact

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gun (or the use of an impact gun equipped with a torsional wrench) may be tempting in terms of saving time, let’s face it: the only way to ensure correct clamping loads is by taking the time to tighten wheel Lug Nuts with the use of a quality and properlycalibrated torque wrench. Never use an impact gun to tighten custom wheel Lug Nuts. Not only will you not be able to accurately control the level of Lug Nut tightness, but use of an impact tool can easily damage the Lug Nuts or the adjacent wheel surface. And when we’re dealing with attractive (and expensive) alloy wheels, such damage, even if only cosmetic, is simply unacceptable. Use sockets that fit the wheel! Before attempting to engage a socket to the Lug Nuts, first check to make sure that the socket is clean to prevent damaging the Lug Nut finish. Also, verify that the socket of choice will comfortably fit into the wheel’s Lug Nut hole (in those cases where the Lug Nut sinks into a recess at the wheel’s bolt holes). Using a socket that is too thick will cause the socket to jam and gall inside the recess, damaging the wheel finish (flaking off chrome, galling a powder coat finish, etc.). My preference is to set aside a dedicated set of thin wall sockets specifically for use on custom wheels. This provides a set of sockets that are kept clean, and that you know will not provide a too-tight fit into bolt hole recesses. The use of a pneumatic (or electric) impact gun offers the potential of damaging the Lug Nut’s exterior surfaces and/or the wheel’s Lug Nut hole area, in both removal and installation procedures. In a nutshell: If you’re dealing with alloy wheels, leave the impact gun on the bench. Here’s another tip: When tightening the wheel’s Lug Nuts, don’t make the mistake of finger-tightening, then lowering the vehicle to the ground to continue tightening. Instead of fighting vehicle weight, it’s best to perform your complete tightening procedure while the tire is off of the ground. If the mating surfaces (wheel to hub) aren’t fully compacted together, placing the weight of the vehicle against the tire results in then overcoming the resistance of the sidewall deflection (due to vehicle weight), which could possibly result in inaccurate torquing. INSTALLATION TIP: In order to prevent the wheel from sticking to the hub in the future (when an aluminum wheel is mated against a steel hub, this can result in electrolysis), it’s a good idea to apply a thin coating of an anti-seize paste to the hub face where the wheel makes contact.

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A thin application of this compound will make it easy to remove the wheels in the future. Re-torque While opinions on re-torquing vary, the best suggestion is to re-torque all wheel Lug Nuts after the first 50 to 100 miles, specifically after installing new wheels. This is especially true of alloy wheels, since the initial Lug Nut tightening may result in a slight compression of the wheel material (at the hub mating face). If a bit of material compression occurs, this will directly result in a lower torque value at the Lug Nuts, decreasing the clamping load. The best approach is to initially tighten all wheel Lug Nuts to specified value, drive the vehicle for 50 to 100 miles, and then re-torque the Lug Nuts. When re-torquing, raise the vehicle to lift the tires away from the ground (removing vehicle weight). Loosen all of the wheel’s Lug Nuts (in a crisscross pattern), then retighten in the proper sequence to full specified torque value.

Wheel Lug Nut torque values Always follow the vehicle maker or wheel maker torque specifications. Just remember that tighter is not necessarily better. While you should always adhere to the torque specifications listed by either the vehicle make or the wheel maker, the box below offers a broad guideline of torque values for common wheel Lug Nut sizes.

Tightening sequence Always tighten any wheel in the proper sequence pattern in order to evenly distribute the clamping load between the wheel and the hub. Especially considering today’s comparatively lightweight hubs and brake rotors, if the wheel Lug Nuts are tightened improperly (in terms of torque value and tightening pattern), the risk of creating a hub/rotor warpage increases, resulting in a brake pulsation. The goal in using the proper tightening pattern is to avoid concentrated areas of clamping force. You want to evenly distribute the clamping load across the hub surface.

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Four-bolt hub With the hub/wheel positioned so that one Lug Nut is at the 12-o’clock position, tighten the 12-o’clock position first, followed by the 6 o’clock position, followed by the 3 o’clock position, followed by the 9 o’clock position.

Five-bolt hub With the hub/wheel positioned with one Lug Nut at 12 o’clock, tighten the 12 o’clock position first, followed by the 7 o’clock position, followed by the 2 o’clock position, followed by the 10 o’clock position, followed by the 5 o’clock position. Basically, from the first Lug Nut, move to a Lug Nut that is furthest away from the first Lug Nut. Then move to a Lug Nut furthest away from that second Lug Nut, etc. Always move to the Lug Nut that is furthest away from the previous Lug Nut.

Six-bolt hub The same rule applies. After tightening the first Lug Nut, move to a Lug Nut that is furthest away from that first Lug Nut, and so-on. Always move to the Lug Nut that is furthest away from the previously-tightened Lug Nut. An example of a six-bolt pattern would be: With the hub/wheel positioned to place one Lug Nut at 12- o’clock, tighten the 12 o’clock position first, followed by the 6 o’clock position, followed by the 2 o’clock position, followed by the 7 o’clock position, followed by the 5 o’clock position, followed by the 10 o’clock position.

Engine mounting: o Install the engine mounts on to the engine. o Remove the hood. o Remove the transmission shifter tab. (There is no need to jack the car up if this is done). o Lift up the engine/transmission with the hoist using a chain rated to lift both the weight of engine and transmission, Follow all safety precautions. Support the weight of the transmission at the rear.

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o Position the engine/transmission unit over the engine bay, with the transmission angled down as far as possible. o Slowly and gradually, lower the unit down, and at the same time move it backwards until it is positioned over the chassis engine mounts. Ensure the transmission is supported and guided at the rear. o Lower the unit on to the chassis engine mounts, and pass through the securing bolts. o Support the transmission with a trolley jack, and check that it is square with the chassis. o Center punch and drill the holes in the chassis for the transmission mounting kit, and secure the transmission in position. o Tighten the engine mount bolts. o Re install the transmission shifter tab. o Install the drive-shaft by sliding the splined end into the rear of the transmission, and bolt the other end to the differential, ensuring that it is torqued to the correct setting. Note, if you are using a new transmission, remember to remove the transit oil bung at the rear of the transmission.

Various types of springs used in suspension system: Located between the car’s body and its axles, the springs absorb the up-and-down motion caused as the wheels roll over varying road surfaces. Though shock absorbers play a part in absorbing shocks, they are misnamed. Their main job is to keep the car from continuing to bounce up and down on its springs after passing over a bump. The main types of springs are Coil springs-A coil spring, also known as a helical spring, is a mechanical device, which is typically used to store energy due to resilience and subsequently release it, to absorb shock, or to maintain a force between contacting surfaces. They are made of an elastic material formed into the shape of a helix which returns to its natural length when unloaded. Leaf springs- A leaf spring is a simple form of spring commonly used for the suspension in wheeled vehicles. Originally called a laminated or carriage spring, and sometimes referred to as a semi-elliptical spring or cart spring, it is one of the oldest forms of springing, dating back to medieval times.

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A leaf spring takes the form of a slender arc-shaped length of spring steel of rectangular cross-section. The center of the arc provides location for the axle, while tie holes are provided at either end for attaching to the vehicle body. For very heavy vehicles, a leaf spring can be made from several leaves stacked on top of each other in several layers, often with progressively shorter leaves. Leaf springs can serve locating and to some extent damping as well as springing functions. While the interleaf friction provides a damping action, it is not well controlled and results in stiction in the motion of the suspension. For this reason manufacturers have experimented with monoleaf springs.

Torsion bars-A torsion bar suspension, also known as a torsion spring suspension or torsion beam suspension, is a general term for any vehicle suspension that uses a torsion bar as its main weight bearing spring. One end of a long metal bar is attached firmly to the vehicle chassis; the opposite end terminates in a lever, the torsion key, mounted perpendicular to the bar, that is attached to a suspension arm, a spindle, or the axle. Vertical motion of the wheel causes the bar to twist around its axis and is resisted by the bar's torsion resistance. The effective spring rate of the bar is determined by its length, cross section, shape, material, and manufacturing process. Air springs- Air Lift adjustable air springs (also called air bags) provide the highest level of safety and comfort when towing or hauling a heavy load. The air springs work with your existing leaf or coil suspension to give you more load support in the front or rear of your vehicle when you need it. Air Lift air springs stabilize your vehicle, giving you up to 5,000 pounds of leveling capacity.

Coil springs are the most common among passenger cars and are the simplest to visualize because they are in the prototypical spiral shape. Springs are simple. With the exception of air springs, which are more like tires or inner tubes filled with air, all the springs mentioned above are made of spring steel that resists bending. As incorporated in the suspension system, their job is to resist compression and expansion, which allows the wheels to move up and down independent of the vehicle — but always returning them to a center position.

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Material used for springs: Spring steel is a low alloy, medium carbon steel with a very high yield strength. This allows objects made of spring steel to return to their original shape despite significant bending or twisting. Silicon is the key component to most spring steel alloys. An example of a spring steel used for cars would be AISI 9255 (DIN and UNI: 55Si7, AFNOR 55S7), containing 1.50%1.80% silicon, 0.70%-1.00% manganese and 0.52%-0.60% carbon. Most spring steels (as used in cars) are hardened and tempered to about 45 Rockwell C. The most widely used spring steel is ASTM A228 (0.80–0.95% carbon), which is also known as music wire. Spring steel is one of the most popular materials used in the fabrication of lockpicks due to its pliability and resilience.

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Unit8: Testing WHEN IT RAINS, IT POURS Researchers test vehicle performance in special facilities built to mimic monsoon rains and windstorms. WEATHER TESTING Everyone complains about the weather, but auto engineers are doing something about it. 

Automakers have built high-tech test chambers so engineers can evaluate products in different environments, ranging from -40 degrees to 130 degrees.

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A model may spend 200 hours in a wind tunnel as researchers and stylists work to lower wind resistance and improve mileage. Aerodynamic drag accounts for about 20% of the energy a vehicle needs just to move through normal air resistance. DURABILITY TESTING An auto needs to withstand years of tough duty, so researchers keep studying how to extend a vehicle’s life… inside and out.

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Even seats are tested for durability. Using robots, automakers research how people of all shapes and sizes affect the upholstery, seat cushions and seat structures over the life of the vehicle.

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High performance extends to car doors too. It takes 84,000 open-and-close cycles to simulate 10 years of customer use of a car door. This testing happens in a wide range of temperatures, just like real life.

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REAL-WORLD TESTING PROVING GROUNDS Automakers test and perfect their products at huge, company-owned proving grounds, which include roads designed to replicate real-world conditions… with potholes, bumps and all. Despite the fastest computers and sophisticated test chambers, a model still needs to be tested in the real world. 

Many operations of a vehicle can be simulated by computer, but engineers need to understand how different systems in an auto interact with each other. Often that can only be done through actual use.

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It’s a global industry and testing is worldwide, too. A model may be driven in extreme conditions like the jungles of Brazil and the mountains of New Zealand. Research in the Southern Hemisphere can extend the seasons for testing and speed up development. GOING… AND GOING To test for durability, an automaker can easily rack up 2 million miles of on-road and track testing on a single model of vehicle. That equates to 80 trips around the world.

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RIGOROUS PROCESSES TESTED, RE-TESTED, CERTIFIED… ON THE ROAD TO MARKET As one of the most regulated products in the marketplace, the automobile undergoes rigorous processes to become certified according to engineering and regulatory standards. 

Through the Society of Automotive Engineers (SAE), 14,000 mobility experts in 100+ countries have provided data resulting in more than 2,600 globally recognized standards for motor vehicle transport.

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An auto must comply with more than 200 government safety and environmental regulations in the U.S. alone. Title 40 of the Code of Federal Regulations, which is the section addressing environment, is actually longer than the U.S. tax code. CASE STUDY: Substantial changes to the federal law on occupant crash protection (FMVSS 208) added 50 tests to the auto development cycle, including new crash tests, new test dummies and new airbag requirements.

Results from any one of these tests can require vehicle changes, from simple recalibrations to significant re-design and re-testing.

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Testing Equipments:

Advanced Battery Analyzer Description: Advanced battery analyzers are largely used in the automobile industry to restore and increase the life of batteries used in vehicles. The advanced battery analyzers are responsible for cycling, rapid testing and boosting of automobile batteries. Applications Advanced battery analyzers are commonly used in the following areas:    

Automobile Industry Medical Equipment Defense Cell Phones

Durability Tester Description: The Durability Tester is an instrument mainly used in the automobile industry for conducting durability tests on car seats. The test method involves conducting a cyclic endurance test on seat tilt gear motors, which are attached to the actual seats. They can be also be

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used for performing durability test on car seat heaters. Testing of basic materials and system components used for seat heaters is very important in automotive industry Durability testers can also be used for testing vehicle's key lock. The equipment is simple to use and can be easily adjusted. Applications The equipment finds application in the following areas:

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Automobile Industry Plastic Industry Biomedical Instruments Rubber Industry Polyurethane Industry

Endurance Tester Description: Endurance testers are mainly used for conducting endurance test on various parts and components of automobiles. Endurance testing is extremely important in automobile industry because it ascertains the life of various automobile components and parts under extreme conditions of pressure, temperature and vibration.

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Besides this, endurance testing of vehicles provides a system analysis that confirms that a part or component or system will perform well in a specific application. This also confirms the capacity of the vehicle's components to withstand off-road use and abuse. Applications Endurance testers are used in the following areas:

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Automobile manufacturing industry Turbine fuel systems

Flammability Tester Description: Flammability Testers are mainly used for testing the flammability and resistance to propagation of flame of materials used in the interiors of motor vehicles. The apparatus also determines the comparative burn rates of cloth, including pile and napped cloth. Salient Features

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The apparatus consists of a horizontal flame or combustion chamber made of stainless steel sheet, in which test is carried out. There is a polycarbonate window in the flame

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  

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chamber for observing the test specimen during test. There is a test specimen holder, used for mounting the test specimen during test. There is a Bunsen burner to provide flame. Supplied with an array of timers, which controls the flame application time and measures the flame time. There is a pre-set type electronic timer, which starts automatically as soon as the test specimen is brought in position above the Bunsen burner.

Flow Testers Description: Flow Testers are used to conduct accelerated stress tests of multiple components or systems of automobiles during simultaneous exposure to thermal cycling and vibration. The equipment is mainly used to perform flow tests on engine and chassis components if an automobile. The engine coolant pressure of automobiles is also measured using flow tester. Salient Features 

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The test method involves pressure cycle and flow testing of a chilled or heated engine coolant mixture. This is accomplished by passing the coolant mixture through radiators, hoses, heater cores and overflow recovery tanks. The equipment also requires environmental chambers and vibration controllers as an

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interface for synchronization to other machines. Pump cavity of coolant mixture at high temperature is accomplished by pump selection; pump and plumbing; and suction pressure and relative mounting locations of reservoir.

Fuel Injection Test Kit Description: The fuel injection test kit is widely used for testing fuel injection systems on motor vehicles. The kit helps to find out any problem in filter or regulator of the vehicle. Salient Features The important features of the fuel injection test kit are: 

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The test kit is supplied with hoses, hose clamps, and hose barb fittings to adjust with any model of vehicle. The kit also includes different types of adapters and gauges for checking various systems. There is also a fuel pressure test kit that tests fuel injection pressure systems on most domestic and imported models of cars and trucks.

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Gas Analyzer Description: Gas analyzers are devices used to analyze exhaust gases from automobile or motorcycle engines. They take care of the fact that a vehicle comply to regulatory limits and also helps to improve fuel consumption of vehicles and manufacture better models of car and engines. Analysis of exhaust gases has become very important factor in other types of engines, like those used in ships, aircrafts, construction equipment and generators. Hence advanced gas analyzers are also designed to meet these requirements. Applications Some of the areas where the gas analyzers find application are:     

Automobile Industry Aerospace Environmental Engineering Construction Industry Shipping

Impact Or Crush Testers Description: An impact test or crash test is a type of destructive testing commonly performed to assure safe design

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standards for automobiles or related components. An impact tester or crash tester is an equipment, which is used to evaluate the aftermath of loose cargo impacts during motor vehicle collisions, and the energy absorption properties of rubber materials. Applications Impact tester are widely used in the many fields. Some of its common applications are:   

Automobile Industry Plastic Industry Metal Industry

Torsional Fatigue Tester Description: The equipment is used to perform torsional fatigue endurance testing of power transmission components such as clutch and torque converters; and steering system components of various automobiles. The test method involves the installation of a hightemperature chamber to examine dynamic features of various automobile components.

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Applications The torsional fatigue tester finds application in the following areas:      

Automobile Industry Railways Airlines Architecture Shipping Nursing Industries

Vibration Tester Description: Vibration tester is an equipment widely used in the automotive industry for conducting vibration testing on various parts and accessories of automobiles. Various automotive components and their accessories are continuously subjected to vibration testing using sophisticated vibration control techniques. Various automotive components ranging from instrument panels to seats inside the car; and from airbag sensors to fuel injection pumps in the engine compartment, are being tested to examine vibration patterns and levels. Applications Vibration testers are widely used for conducting vibration tests on various automobile parts & components. Some other areas where they are used are:

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> Automotive Industry > Environmental Stress Testing > Aerospace > Military/Defense > Microelectronics

Testing a Car Testing a car in the United States is a long, expensive and often tedious process. The manufacturers' goal is to make a vehicle that meets established government safety standards, that will stand up to normal consumer use while incurring minimal warranty claims and will hit that sweet spot between customer demand and profitability. One of the more well-known tests is crash testing. You may know the slow-motion films of cars being crash tested with dummies inside "playing" car passengers. Depending on the purpose of the film, the mannequin either goes flying through the windshield, or is protected by a car seatbelt and airbag. Manufacturers like to sound the proverbial trumpet when one of their vehicles, especially a family-oriented vehicle, scores well in government and independent crash-safety tests. In the United States, the two main bodies that conduct crash safety testing are the Insurance Institute for Highway Safety and the National Highway Traffic Safety Administration. Both operate independently of the automobile industry. In addition to crash testing, automakers must track a plethora of quality measurements. These tests are conducted by the manufacturers themselves to refine their vehicles as much as possible. Here are a few questions that manufacturers may tackle:        

How noisy is it inside the cabin? How much noise comes from the engine? How much is wind noise? How much noise is created by tires contacting the pavement? How much vibration is there at different speeds? How fast does the air conditioning system or heater kick in? Does the amount of quality and luxury match other products in this brand? Does it equal or exceed competitive offerings? Are we meeting our own standards for how neat and precise the fine details on the car are? What drive train combination will give us optimal fuel efficiency while satisfying emissions requirements? How do we reduce weight and waste without compromising safety or comfort?

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How does the car perform in extreme conditions?

If that seems like a lot to keep track of, that's because it is. However, automakers typically assign specialized teams to address each one of these questions so that they can come up with the best solutions in short order. Depending on what's being measured or tested, engineers can make changes on the spot. In other cases, test findings may require an extensive rethinking of how a part or set of parts function. To make sure the entire testing process stays reasonably on schedule, manufacturers make multiple "test mules," or pre-production cars, for testing. This way, multiple systems can be designed and experimented with at once.

Car Testing Criteria Testing automobiles is expensive. The automobile prototypes, or test mules, can cost several hundred thousand dollars, even for so-called economy cars. Furthermore, it requires paying the salaries of teams of engineers, paying for the costs of special measuring equipment, and shelling out for meals and accommodations for these small armies when they must conduct their experiments away from their main offices. Therefore, an entry-level commuter car would not be subjected to the same testing criteria as a Corvette, which GM wants to market as a "world class" car. And that Corvette, likewise, would not be subjected to the same off-road rigors as a rugged Hummer. Sometimes manufacturers get valuable design and engineering data from sources outside of their official test programs for preproduction vehicles. Some of these sources include:    

Quality surveys by companies like J.D. Power and Associates Independent media and customer reviews of existing vehicles Observing trends in popular culture in how people modify their vehicles after purchase Using racing innovations to make production cars faster or safer

For all their contributions to automotive advancement, test cars almost always meet an unpleasant fate. Since they're typically unfinished works that can't be sold and put under warranty, most test mules are simply sent to the crusher once their work is done. This fate was made controversially apparent in the documentary "Who Killed the Electric Car?" After General Motors decided to abandon the EV1 electric car program against the wishes of EV1 supporters, the company faced a storm of controversy as they hauled the vehicles away to be destroyed.

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Ford faced similar outrage in 2004, when it decided to pull the plug on its electric car experiment with its Think model, which it had leased to customers willing to test it. A public relations nightmare for Ford ensued when word leaked that the company planned to destroy the cars after the three-year test period. The company eventually relented by agreeing to ship the cars back to Norway where they were produced. While those particular decisions were socially and politically charged because of their environmental overtones, the fact is that test cars are routinely destroyed once manufacturers no longer need them.

Crash test Crash test dummies have been the subject of public service announcements, cartoons, parodies, even the name of a band. Real crash test dummies, however, are true lifesavers as an integral part of automotive crash tests. Even though cars get a little safer each year, and fatality rates are declining, car crashes are still one of the leading causes of death and injury in the United States. One of the reasons cars have been getting safer is because of a well-established testing program. In this article, you'll learn all about automotive crash testing, including crash test programs, ratings, dummies and future improvements. You'll be amazed at how much thought and preparation goes into making sure that safe cars are on the roads!

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Fuel economy test Fuel economy is measured under controlled conditions in a laboratory using a standardized test procedure specified by federal law. Manufacturers test their own vehicles—usually preproduction prototypes—and report the results to EPA. EPA reviews the results and confirms about 10-15 percent of them through their own tests at the National Vehicles and Fuel Emissions Laboratory. In the laboratory, the vehicle's drive wheels are placed on a machine called a dynamometer that simulates the driving environment—much like an exercise bike simulates cycling. The energy required to move the rollers can be adjusted to account for wind resistance and the vehicle's weight.

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8) Two and Three Wheelers Classification of two and three wheelers:

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Two wheeler frame A motorcycle frame includes the head tube that holds the front fork and allows it to pivot. Some motorcycles include the engine as a load-bearing, stressed member. The rear suspension is an integral component in the design. Traditionally frames have been steel, but titanium, aluminium, magnesium, and carbon-fibre, along with composites of these materials, have been used. Because of different motorcycles' varying needs of cost, complexity, weight distribution, stiffness, power output and speed, there is no single ideal frame design.

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Two wheelar suspension A motorcycle's suspension serves a dual purpose: contributing to the vehicle's handling and braking, and providing safety and comfort by keeping the vehicle's passengers comfortably isolated from road noise, bumps and vibrations. The typical motorcycle has a pair of fork tubes for the front suspension, and a swingarm with one or two shock absorbers for the rear suspension.

Cylinder arrangement in two wheelers The majority of motorcycle engines are configured as singles, parallel twins, triples, fours and sixes; and all these may be inline or transverse. V engines include V-twins and Vfours, and horizontally opposed engines include flat-twins, flat-fours and flat-sixes. Wankel engines are either single-rotor or twin-rotor. Bigger bikes tend to have more cylinders for smoothness and increased power. Modern singles range in capacity from 50 cc to 660 cc, twins from 175 cc to 1,800 cc, triples from 380 cc to 2,300 cc, and so on. Single

1960 BSA Gold Star Single-cylinder engines (aka "singles" or "thumpers") have the cylinder vertical, inclined or horizontal, the last type most common in step-through motorcycles. Single-cylinder engines require both a larger flywheel and a heavier-duty gearbox than multicylinder engines. Small singles are cheap to build and maintain and are suitable as cheap utility motorcycles. Until the mid-1960s, road-racing machines (such as Matchless, AJS and Norton) tended to be large singles, but since then multicylinder racers have become the norm. Off-

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road bikes still use single-cylinder engines; but the new categories of dual-sport bikes tend to use twins or triples. Twin Straight

1962 Honda CB77 Super hawk 305 cc (18.6 cu in) twin engine.

Starting with Edward Turner's 1937 Triumph Speed Twin design, and until the mid1970s, the parallel-twin was the most common British motorcycle type. Parallel-twins are usually mounted transversely, with the cylinders side by side above the crankshaft, and with exhaust pipes at the front, in the cool airstream. Longitudinal twins (aka "inline twins") include the 500 cc Sunbeam S7 and S8. There are three crankshaft configurations for this engine: 360°, 180°, and the newer 270°. Parallel twins usually have only two main bearings. V-twin

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Harley-Davidson Sportster V-twin

In a V-twin engine the cylinders form a "V" around the crankshaft. A V-angle of 90°, as used by Ducati and Moto Guzzi, can give perfect primary and secondary balance, with a pleasingly irregular firing order. A lesser angle gives a more compact motor, but one which is prone to vibration, such as 42° (Indian), 45° (Harley-Davidson), 52° Honda, and 60° (Aprilia). Most V-twins have a single crankpin shared by side-by-side connecting rods (so that the cylinders are slightly offset), but a variation is to have a single crankpin with"fork & blade" con-rods, to keep the cylinders in line. Non-90° V-twins may have offset crankpins to try to reduce vibration. V-twins may be mounted either longitudinally with the cylinders protruding either side (e.g. Honda CX500 and Moto Guzzi), or transversely, (e.g. Harley Davidson, Ducati, Hesketh, Vincent, Moto Morini and Aprilia). Transverse V-twins can raise difficulties in cooling the aft cylinder, and in siting the airbox, battery, aft carburetter, and aft exhaust pipe. Flat twin

BMW's opposed twin on a 1954 R68

Main article: Flat-twin engine In a flat-twin (boxer) engine, the cylinders are horizontally opposed. The boxer has perfect primary balance, balance only a small rocking couple, and (unlike a V-twin), regular firing intervals, producing very low vibration levels (without the use of counterbalance shafts). Such engines are usually mounted with a longitudinalcrankshaft, with the cylinders protrude into the airstream, so that a flat twin can satisfactorily be air-cooled. Flats twins are made by BMW, Ural, Harley-Davidson's WW2 "XA" model, Marusho, and historically by Douglas. The longitudinal mounting makes the flat twin highly suitable for shaft final drive.

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Some early motorcycles used transverse-crank flat twin engines. Tandem twin The Tandem Twin where the cylinders are longitudinal, and have two cranks geared together such as Kawasaki's KR250 road bike and KR250 and KR350 GP Bikes. A tandem twin is effectively a pair of geared singles, and is to be distinguished from an inline twin such as the Sunbeam S7. Tandem twins are suitable primarily for two-stroke racers. Triple Inline triple

Triumph Rocket III inline-3 Three-cylinder engines, aka triples, are normally mounted transversely. The British Hinckley Triumph factory has specialised in transverse triples, although their 2,300 cc Rocket III has its engine mounted longitudinally. Other examples are the Benelli' "Tre"and the Yamaha XS750. The Italian firm Laverda made a few 1,000 cc and 1,200 cc triples. Curiously, some Laverda Triples had 120° cranks, while some had 180° cranks (essentially three-quarters of a four). BMW made the K75 longitudinally mounted 750 cc triple with the cylinders parallel to the ground. Meriden Triumph developed the 750 cc Trident, from which BSA "badge-engineered" the Rocket-3. Some triples were two-strokes. The Kawasaki triples were produced with capacities of 250, 350, 400, 500, and 750 cc in the 1970s, while Suzuki produced 380, 550, and 750 triples (the last being water-cooled). Motobecane made 350 cc and fuel-injected 500 cc triples with 3 into 4 pipes in the early seventies. Honda produced the water-cooled V-3 two-strokes MVX250 and NS400. There have been various race bike triples such as Kawasaki KR750, Suzuki TR750 transverse 3's, and Proton/Modenas KR3, Honda NS500 V-3s. Four Four-cylinder engines are most commonly found in a transverse-mounted inline four layout, although some are longitudinal (as in the earlier BMW K100). V-

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4 and boxer designs (as in the earlier Honda Gold Wing) have been produced. One of the more unusual designs was the Ariel Square Four, effectively two parallel-twin engines one in front of the other in a common crankcase – it had remarkably little vibration due to the contra-rotating crankshafts.

Inline four

Honda CB750 transverse inline-4 Since the advent of the Honda CB750 straight-four engine, straight-fours have dominated the non-cruiser street motorcycle segments. The German manufacturer Münch based their motorcycles on four-cylinder car engines (e.g. Mammut 2000 has a 2.0l with a turbo and cylinder heads by Cosworth). Flat four

The Honda GL1000 flat-four

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A flat-4 or horizontally opposed-4 is a flat engine with four cylinders arranged horizontally in two banks of two cylinders on each side of a central crankcase. The pistons are usually mounted on the crankshaft such that opposing pistons move back and forth in opposite directions at the same time, somewhat like a boxing competitor punching their gloves together before a fight, which has led to it being referred to as a boxer engine. The configuration results in inherently good balance of the reciprocating parts, a low centre of gravity, and a very short engine length.

V4

Honda VFR1200F engine with dual clutch transmission. Honda uses V4 engines in the ST series and VFR series. As for two-stroke engines, there were four cylinders in the smaller classes such as Kawasaki's 125 cc KR3 square 4 and Yamaha's 250 cc RD500 V4 (RZ 500 in the US). Yamaha later raced transverse four TZ500/700/750's and virtually all the bikes in the last decade of the two-stroke GP500 era were fours (first squares then Vees) i.e. Honda, Kawasaki, Cagiva, Suzuki, Yamaha Kawasaki also experimented with a trapezoidal four the 602S. Yamaha made the V4 RD500LC, and Suzuki the RG400 and RG500 square four road bikes. Square four A square four is a U engine with two cylinders on each side. This configuration was used on the Ariel Square Four motorcycle from 1931 to 1959. This design was revived as a

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two-stroke version on some racing Suzuki models, and their subsequent road-going version the RG500. Although some racing success was achieved, the road bikes didn't sell in great numbers, and the design was phased out in favour of in-line, four-stroke designs, as at the time two-stroke engines were quickly being superseded by more economical, reliable, and emissions-friendly four-strokes.

Five V5

Honda V5 MotoGP engine Honda has produced five-cylinder engines for racing, the RC211V 990 cc V5. No V5 engines are currently available in commercial production motorcycles. Just prior to their collapse, BSA planned a modular family of bike engines based around a 200 cc single. The range was to include the single, a 400 cc twin, a 600 cc triple and a 1000 cc V5. None of these motorcycles reached production.

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Six Inline six

Benelli Sei inline-6 The 1,047 cc Honda CBX was produced from 1978 to 1982. The 1,300 cc Kawasaki KZ1300 was produced from 1979 to 1989. Benelli made the 750 cc and 900 cc the Sei from 1972 to 1978. Honda made a 250 cc straight-six GP bike. The BMW K1600GT and K1600GTL, which were launched in 2011, have a transverse-mounted 1,649 cc engine. Flat 6

Honda Valkyrie flat-6 The six-cylinder engine is currently used by Honda in the Gold Wing, and had previously been used in theValkyrie and the Rune, both of which were cruiser developments of the Gold Wing.

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V8

Moto Guzzi V8 Galbusera built a V8 in 1938, and Moto Guzzi experimented over a period of two years with its dual-overhead-cam 500 cc V8 (the Otto Cylindri) in the 1950s. Some custom and one-off motorcycles use more than six cylinders. For example, the Boss Hoss motorcycle uses (5,700 cc, 6,000 cc and 8,200 cc) Chevy V-8 crate motors. In the 1990s DaimlerChrysler manufactured a limited number of Tomahawk concept bikes featuring a Dodge Viper's V-10 engine. Australian company Drysdale have built short runs of 750 cc V8 superbikes and 1L V8 roadgoing motorcycles, both with engines specifically developed for the purpose. No major motorcycle manufacturer has used eight or more cylinders, although Honda made the 'almost' V8 oval-piston NR750 road bike and NR500 GP bike (having eight connecting rods, for example) and Morbidelli has shown two V8 prototype road bikes, but has yet to get off the ground

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Three wheelars A three-wheeler is a vehicle with three wheels, either "human or people-powered vehicles" (HPV or PPV or velomobiles) or motorized vehicles in the form of a motorcycle, all-terrain vehicle (ATV) or automobile. Other names for three-wheelers include trikes, tricars and cycle cars. The term tricycle is used somewhat interchangeably, but the term three-wheeler is more often applied to motor vehicles. They can be legally classed as either automobiles or motorcycles. Three-wheeler cars, usually microcars, are often built for economic reasons: in the UK for tax advantages, or in the US to take advantage of lower safety regulations, being classed as motorcycles. As a result of their light construction and potential better streamlining, three-wheeled cars are usually very economical to run. Three-wheeler transport vehicles known as Auto Rickshaws are a common means of public transportation in many countries in the world. Auto rickshaws are an essential form of urban transport in many developing countries such as India, and a form of novelty transport in many Eastern countries.

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Dynamic Stability of Three-Wheeled Vehicles in Automotive-Type Applications

The idea of smaller, energy-efficient vehicles for personal transportation seems to naturally introduce the three wheel platform. Opinions normally run either strongly against or strongly in favor of the three wheel layout. Advocates point to a mechanically simplified chassis, lower manufacturing costs, and superior handling characteristics. Opponents decry the three-wheeler's propensity to overturn. Both opinions have merit. Three-wheelers are lighter and less costly to manufacture. But when poorly designed or in the wrong application, a three wheel platform is the less forgiving layout. When correctly designed, however, a three wheel car can light new fires of enthusiasm under tired and routine driving experiences. And today's tilting three-wheelers, vehicles that lean into turns like motorcycles, point the way to a new category of personal transportation products of much lower mass, far greater fuel economy, and superior cornering power. Inherently Responsive Design Designing to the three-wheeler's inherent characteristics can produce a highperformance machine that will out corner many four-wheelers. A well designed threewheeler is likely to be one of the most responsive machines one will ever experience over a winding road. Superior responsiveness is primarily due to the three-wheeler's rapid yaw response time. Yaw response time is the time it takes for a vehicle to reach steady-state cornering after a quick steering input. A softly sprung four-wheeler will have a yaw response time of about 0.30 seconds, and a four wheel sports car will respond in about half that time.

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A well designed three-wheeler can reach steady-state cornering in as little as 0.10 seconds, or about 33 percent quicker than a high-performance four wheel car. Quick steering response has nothing to do with the number of wheels or how they are configured. It is a byproduct of reduced mass and low polar moment of inertia. A typical three-wheeler is lighter and has approximately 30 percent less polar moment than a comparable four wheel design. Rollover Stability of Conventional Non-Tilting Three-Wheeler A conventional, non-tilting three wheel car can equal the rollover resistance of a four wheel car, provided the location of the center-of-gravity (cg) is low and near the side-by-side wheels. Like a four wheel vehicle, a three-wheeler's margin of safety against rollover is determined by its L/H ratio, or the half-tread (L) in relation to the cg height (H). Unlike a four-wheeler, however, a three-wheeler's half-tread is determined by the relationship between the actual tread (distance between the side-by-side wheels) and the longitudinal location of the cg, which translates into an "effective" half-tread. The effective half-tread can be increased by placing the side-by-side wheels farther apart, by locating the cg closer to the side-by-side wheels, and to a lesser degree by increasing the wheelbase. Rollover resistance increases when the effective half-tread is increased and when the cg lowered, both of which increase the L/H ratio. A simple way to model a three-wheeler's margin of safety against rollover is to construct a base cone using the cg height, its location along the wheelbase, and the effective half-tread of the vehicle. Maximum lateral g-loads are determined by the tire's friction coefficient. Projecting the maximum turn-force resultant toward the ground forms the base of the cone. A one-g load acting across the vehicle's cg, for example, would result in a 45 degree projection toward the ground plane. If the base of the cone falls outside the effective half-tread, the vehicle will overturn before it skids. If it falls inside the effective half-tread, the vehicle will skid before it overturns. To see a drawing showing a base-cone illustration of single front wheel (1F2R) and single rear wheel (2F1R) vehicles, click on: Single Front & Single Rear Wheel Comparison (23k). The foregoing is a simple rigid-body analysis and it does not consider the effects of suspension, rebound, and body-roll inertial forces. It therefore provides an approximation of rollover threshold under dynamic conditions. Oversteer/Understeer Characteristics The single front wheel layout naturally oversteers and the single rear wheel layout naturally understeers. Because some degree of understeer is preferred in consumer vehicles, the single rear wheel layout has the advantage with the lay driver. Another consideration is the effect of braking and accelerating turns. A braking turn tends to

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destabilize a single front wheel vehicle, whereas an accelerating turn tends to destabilize a single rear wheel vehicle. Because braking forces can reach greater magnitudes than acceleration forces (maximum braking force is determined by the adhesion limit of all three wheels, rather than two or one wheel in the case of acceleration), the single rear wheel design has the advantage on this count. Consequently, the single rear wheel layout is usually considered the preferred platform for a high-performance consumer vehicle in the hands of the non-professional driver. But racecar drivers often prefer slight oversteer to understeer. Oversteer gives the skilled driver the ability to perform extreme maneuvers that an understeering vehicle would simply mush through and refuse to perform. Moreover, by varying tire size and pressure, a single front wheel vehicle can be designed for neutral steer with oversteer present only at the limit of adhesion. Much depends on the details of the design, as well as driver preferences and skills. Tilting Three-Wheelers (TTWs) Tilting three-wheelers, vehicles that lean into turns like motorcycles, offer increased resistance to rollover and much greater cornering power often exceeding that of a four wheel vehicle. And designers are no longer limited to a wide, low layout in order to obtain high rollover stability. Allowing the vehicle to lean into turns provides a much greater latitude in the selection of a cg location and the separation between opposing wheels. Consider that a motorcycle has no side-by-side wheels, yet it does not overturn when going around corners. A motorcycle negotiates turns by assuming a lean angle that balances the vector of forces resulting from the turn rate. The rider leans the motorcycle into the turn so it remains in balance with the forces that are acting on it. As long as the motorcycle's lean angle matches the vector of forces in a turn (resultant), it will not overturn. In order to stay in balance with turn forces under all possible conditions, however, a motorcycle must be able to lean at an angle of 50-55 degrees before any part of the machine contacts the ground. Three and four wheel vehicles can also be made to lean into turns. But with tilting vehicles equipped with side-by-side wheels, other physical and geometric realities come into play. For example, a vehicle having a wide body may contact the ground even at moderate lean angles, which will make it impossible to stay in balance with turn forces at the upper extremes. In addition, the greater the separation between the side-by-side wheels, the greater the wheel movement at equivalent lean angles. The movement of the side-by-side wheels can become excessive even at relatively small angles of lean in vehicles having a track approaching that of conventional automobiles. And the mechanical challenges of accommodating steering, bounce, and tilting, along with the angular limitations of CV joints on powered axles, places additional limitations on the

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lean angle of tilting multi-track vehicles. As a result, much of the recent work on tilting suspension systems has concentrated the three wheel platform. The Project 32 Slalom (1F2R) and the Mercedes F300 Life-Jet (2F1R) are excellent examples of modern tilting three wheel designs. Free-Leaning versus Active Lean Control Tilting three-wheelers can be free-leaning and controlled by the rider, just like ordinary motorcycles. However, if the mechanical limit of lean is less than is necessary to balance turn forces under all possible conditions, then some form of active (forced) lean control must be used to account for turns that exceed the lean limit. This is usually accomplished by hydraulic or electro-mechanical actuators operating on signals from an electronic control unit (ECU). Normally, the ECU processes signals from sensors that monitor lateral acceleration, vehicle yaw and lean angle, steering angle, and other relevant factors, then provides control output to the lean actuators. Another advantage of active lean control is that the operator is no longer required to balance the vehicle, as when operating a motorcycle. With active lean control, the vehicle is driven just like an ordinary automobile, and the lean control system takes care of the rest. Rollover Threshold of TTWs The rollover threshold of a TTW is determined by the same dynamic forces and geometric relationships that determine the rollover threshold of conventional vehicles, except that the effects of leaning become a part of the equation. As long as the lean angle matches the vector of forces in a turn, then, just like a motorcycle, the vehicle has no meaningful rollover threshold. In other words, there will be no outboard projection of the resultant in turns, as is the case with non-tilting vehicles. In a steadily increasing turn, the vehicle will lean at greater and greater angles, as needed to remain in balance with turn forces. Consequently, the width of the track is largely irrelevant to rollover stability under free-leaning conditions. With vehicles having a lean limit, however, the resultant will begin to migrate outboard when the turn rate increases above the rate that can be balanced by the maximum lean angle. Above lean limit, loads are transferred to the outboard wheel, as in a conventional vehicle. Tony Foale, author of Motorcycle Chassis Design, explains the behavior of an all-leaning-wheels TTW in terms of a virtual motorcycle wheel located between the two opposing real wheels. In a balanced turn, the resultant remains in line with the virtual motorcycle wheel. But in turns taken above the limit of lean, the resultant projects to the outside of the

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virtual wheel (vehicle centerline), according to the magnitude of turn forces in excess of those at lean limit. It's also important to note that the vehicle cg moves inboard as the vehicle leans into a turn. When calculating the rollover threshold of a TTW having a lean limit, one must consider the inboard migration of the cg due to the angle of lean, the outboard projection of forces at the friction limit of the tires, and the traditional relationships between the cg height, the effective half-tread (at lean limit), and the wheelbase. TTWs With Only One Leaning Wheel Another interesting category of TTWs includes vehicles having only a single leaning wheel, such as the Lean Machine developed at General Motors in the late '70s and early '80s. GM's Lean Machine is a 1F2R design wherein the single front wheel and passenger compartment lean into turns, while the rear section, which carries the two side-by-side wheels and the power train, does not lean. The two sections are connected by a mechanical pivot. The rollover threshold of this type of vehicle depends on the rollover threshold of each of the two sections taken independently. The non-leaning section behaves according to the traditional base cone analysis. Its length-to-height ratio determines its rollover threshold. Assuming there is no lean limit on the leaning section; it would behave as a motorcycle and lean to the angle necessary for balanced turns. The height of the center of gravity of the leaning section is unimportant, as long as there is no effective lean limit. The rollover threshold of a vehicle without an effective lean limit will be largely determined by the rollover threshold of the non-leaning section. But the leaning section can have a positive or negative effect, depending on the elevation of the pivot axis at the point of intersection with the centerline of the side-by-side wheels. If the pivot axis (the roll axis of the leaning section) projects to the axle centerline at a point higher than the center of the wheels, then it will reduce the rollover threshold established by the non-leaning section. If it projects to a point that is lower than the center of the side-byside wheels, then the rollover threshold will actually increase as the turn rate increases. In other words, the vehicle will become more resistant to overturn in sharper turns. If the pivot axis projects to the centerline of the axle, then the leaning section has no effect on the rollover threshold established by the non-leaning section. In vehicles of this type that have a limit on the degree of lean, rollover threshold would be calculated as with an all-tilting-wheels vehicle operating at or above its limit of lean. In this case, the cg height of the leaning section would have an important effect on the behavior of the vehicle as a whole. Once a tilting vehicle reaches its limit of lean and locks against its limit stops, it can be analyzed as a non-tilting vehicle having the

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geometric configuration of the tilting vehicle at lean limit. The front-to-rear incline of the roll axis of the leaning section is an important consideration with this type of vehicle. With free-leaning designs, the roll axis should project to the ground at the front (leaning) wheel. This is done to avoid a roll/lean couple, which could result in roll inputs during acceleration and braking. This is not as important in vehicles equipped with active lean control.

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