Automotive chassis and suspension by M A Qadeer

By

Automotive Chassis and

suspensions

Mohd Abdul Qadeer Siddiqui

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.

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

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.

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

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.

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

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.

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.

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,

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

2) FRAMES

TYPES OF CHASSIS FRAMES:

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

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,

(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

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

three-dimensional 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.

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

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.

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

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

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.

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.

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.

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.

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,

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.

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.

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.

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.

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.

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.

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.

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.

There are a couple of key components in power steering in addition to the rack-and-pinion 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.

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.

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.

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.

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.

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

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.

 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

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

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

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 brake (foot-brake) operating on at least 4 wheels and a parking (handbrake) operating on at least 2 wheels.

Service Brake Parking Brake Vehicle with a single line braking system Vehicle with a split (dual) braking system

Vehicles with 3 wheels with a service brake operating on ALL wheels and a parking brake operating on at least one wheel which were first used:

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 which do NOT have one means of control operating on at least 4 wheels (or 3 for three wheeled vehicle) and which have one brake system with two means of control or two brake systems with separate means of control.

30% for first means of control

25% for second means of control

Vehicles first used before 1 January 1915 One efficient braking system required

Class 5 Minimum Brake Efficiencies Required

Service Brake Parking Brake Vehicle with a single line braking system

Vehicle with a split (dual) braking system

Buses first used on or after 1

January 1968 50% 25% 16%

Buses first used before 1

January 1968 45% 20%

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

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

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.

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

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

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.

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.

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.