automotive chassis and suspension by m a qadeer

8/14/2019 Automotive chassis and suspension by M A Qadeer

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Automotive chassis and suspensions M A Qadeer Siddiqui

By

Mohd Abdul Qadeer Siddiqui


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utomotive Chassis andsuspensions

Mohd Abdul Qadeer Siddiqui

B-tech (Automobile Engineering)

Bhaskar Engineering College (JNTU- Hyderabad)


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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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ontents

1.Introduction to chassis system8

2.Frames.14

3.Steering system..34

4.Brakes.46

5.Suspensions64

6.Mountings of wheels and engine..79

7.Testing88

8.Two and three wheelers.103


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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 deviceslike 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 ingeneral, 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 torear, 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 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.

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 cars 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

cars 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 vehicles 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, thevehicle 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 toform 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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Wheels and tyresVehicle 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:

Wirespokedwheels

Sheet metal wheels, double wall welded

Disc wheelscast light metal wheels

cast steel wheels


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a) Wellbaserim, 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 FirestoneKronprinz system, d)

tapered bead seat rim Lemmerzsystem, e) tapered bead seat rim type AR

With regard to the rim base two types are distinguished:

Wide base rim

Wellbaserim

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 inclines5 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 wellbase rim this recess helps in fitting the tyre.The tyre and bead are pressed into the wellbase at one side, and then pressed inwards

or outwards across the rim flange on the opposite side.

The tyre is always pressed into the wellbase 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 wellbase. They are also called widebase

rims. In order to gain more space for the brakes the wellbase is shifted asymmetrically

to the outer rim flange. The 15 tapered rim is undivided, but has a particularly stronglyinclined 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 sideslipping. 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 lowpressure 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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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 tyresTires 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 cars 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 SystemSteering GearsOne 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

Understeerand oversteerare 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 cars 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 realadvantages 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 its 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 tirelean 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 manufacturers 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 steeringin 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 dependson 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 thesteering 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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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 homecomputer 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 computersoftware. 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 dont 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 smallvariations in weight around its circumference that must be corrected for. And the tyre

isnt 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 weightto 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 dont 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 cars 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. Its 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 andwaterways.

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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UNIT 4 BRAKESBrakes:

A brakeis 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 convertkinetic 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 forceThe 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 dissipationBrakes 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.

FadeAs 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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SmoothnessA 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. PowerBrakes 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 feelBrake 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.

DragBrakes 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.

DurabilityFriction 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.

WeightBrakes are often "added weight" in that they serve no other function.

Further, brakes are often mounted on wheels, and unsprung weight can significantlyhurt traction in some circumstances. "Weight" may mean the brake itself, or may

include additional support structure.

NoiseBrakes 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 theseexamples 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 testsindicate 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 skilleddriver 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 CodeSpeed (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 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


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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 threewheeled 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 ofcontrol

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


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Buses first used on or after 1

January 196850% 25% 16%

Buses first used before 1January 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
http://trapinrap123.files.wordpress.com/2013/04/weighttransfer.jpg


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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

materials 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 thepads/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 africtional 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 youwill 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. Becausetorque 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 SystemsRecords 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 drumbrake, 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 twoopposite 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 systemsincluded. 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 confinedliquid 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 brakepressure 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 initialapplication. 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 roadsafety 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 350-

440 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. Thebooster 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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Independent Front Suspensions

In this setup, the front wheels are allowed to move independently. TheMacpherson

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 front-

wheel 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 mountingpositions 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 semi-

elliptical 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