An automobile is a motor vehicle used for transportation that runs on roads. Most have seating for 1-8 people and four wheels. Automobiles have various controls for driving, safety, and passenger comfort. Over time, additional features like backup cameras and entertainment systems have been added. Electric vehicles are becoming more commercially available. While automobiles provide transportation benefits, they also have societal costs like road maintenance and pollution. There are over 1 billion vehicles globally. Automobiles can be classified by purpose, size, fuel source, transmission, wheels, and side of driver seat placement. Key components include the frame, engine, transmission, controls, and accessories. Braking and four-wheel drive systems are important safety systems.

1. Introduction
An automobile is a wheeled, self-powered motor vehicle used for transportation and a product of
the automotive industry. Most definitions of the term specify that automobiles are designed to run
primarily on roads, to have seating for one to eight people, to typically have four wheels with tyres,
and to be constructed principally for the transport of people rather than goods. Automobiles are
equipped with controls used for driving, parking, passenger comfort and safety, and controlling a
variety of lights. Over the decades, additional features and controls have been added to vehicles,
making them progressively more complex. Examples include rear reversing cameras, air
conditioning, navigation systems, and in car entertainment. Vehicles using alternative fuels such
as ethanol flexible-fuel vehicles and natural gas vehicles are also gaining popularity in some
countries. Electric vehicles, which were invented early in the history, began to become commercially
available in 2008.
The costs to society of automobile use include:
1. Maintaining roads,
2. Land use,
3. Road congestion,
4. Air pollution,
5. Public health,
6. Health care, and
7. Disposing of the vehicle at the end of its life.
Road traffic accidents are the largest cause of injury-related deaths worldwide.
The benefits may include on-demand transportation, mobility, independence, and convenience. The
societal benefits may include: economic benefits, such as job and wealth creation from automobile
production, sales and maintenance, transportation provision, society well-being derived from leisure
and travel opportunities, and revenue generation from the tax opportunities. The ability for humans
to move flexibly from place to place has far-reaching implications for the nature of societies. It was
estimated in 2010 that the number of cars had risen to over 1 billion vehicles, up from the 500
million of 1986.
What is Automobile?
A self-propelled passenger vehicle that usually has four wheels and an internal combustion engine,
used for land transport is known as automobile. An automobile (or automotive) is a vehicle that is
capable of propelling itself. Since seventeenth century, several attempts have been made to design
and construct a practically operative automobile. Today, automobiles play an unimaginable role in
the social, economic and industrial growth of any country. After the introduction of internal
combustion engines, the Automobile industry has seen a tremendous growth.

2. Classification of automobile:
Automobiles can be classified into several types based on several criteria. A brief classification of
automobiles is listed below:
Based on purpose:
1. Passenger vehicles – These automobiles carry passengers – e.g.: Buses, Passenger trains, cars
2. Goods vehicles – These vehicles are used for transportation of goods from one place to another.
e.g.: Goods lorry, goods carrier
Based on capacity:
1. Heavy Motor Vehicle (HMV) – Large and bulky motor vehicles – e.g.: Large trucks, buses
2. Light Motor Vehicle (LMV) – Small motor vehicles – e.g.: Cars, Jeeps
3. Medium Vehicle – Relatively medium sized vehicles – e.g.: Small trucks, mini buses
Based on fuel source:
1. Petrol engine vehicles – Automobiles powered by petrol engine – e.g.: scooters, cars, mopeds,
motorcycles
2. Diesel engine vehicles – Automotives powered by diesel engine – e.g.: Trucks, Buses
3. Gas vehicles – Vehicles that use gas turbine as power source – e.g.: Turbine powered cars
4. Solar vehicles – Vehicles significantly powered by solar power – e.g.: Solar powered cars
5. Hydrogen vehicles – Vehicles that have hydrogen as a power source – e.g.: Honda FCX Clarity
6. Electric vehicles – Automobiles that use electricity as a power source – e.g.: Electric cars, electric
buses
7. Steam Engine Vehicles – Automotives powered by steam engine – e.g.: Steamboat, steam
locomotive, steam wagon
8. Hybrid Vehicles – Vehicles that use two or more distinct power sources – e.g.: Hybrid buses,
hybrid cars like Toyota Prius, Honda Insight
9. Hybrid Electric Vehicle (HEV) – Automobile that uses both Internal Combustion Engine and
Electric Power Source to propel itself – e.g.: Jaguar C-X75
Based on type of transmission:
1. Automatic transmission vehicles – Automobiles that are capable of changing gear ratios
automatically as they move – e.g.: Automatic Transmission Cars

3. 2. Conventional transmission vehicles – Automotives whose gear ratios have to be changed
manually
3. Semi-automatic transmissionvehicles – Vehicles that facilitate manual gear changing with clutch
pedal
Based on number of wheels:
1. Two wheeler – Automobiles having two wheels – e.g.: Scooters, motorcycles
2. Three wheeler – Automotive having three wheels – e.g.: Tricycles, Auto rickshaws, Tempos
3. Four wheeler – Vehicle having four wheels – e.g.: Car, Jeep
4. Six wheeler – Automobile having six wheels used for heavy transportation – e.g.: Large trucks,
large buses
Based on the side of drive:
1. Left hand drive automobile – Vehicle in which steering wheel is fitted on the left hand side – e.g.:
Automobiles found in USA, Russia
2. Right hand drive automobile - Vehicle in which steering wheel is fitted on the right hand side –
e.g.: Automobiles found in India, Australia
Components of an Automobile:
The main units of an automobile are:
1. The basic structure
2. The power plant
3. The transmissionsystem
4. The auxiliaries
5. The controls
6. The superstructure

4. The Basic Structure
This is the unit on which are to be built the remainder of the units required to turn it into a power
operated vehicle. It consists of the frame, the suspension system, axles, wheels and tyres.
FRAME
There are two distinct forms of construction in common use:
1. The conventional pressed steel frame to which all the mechanical units are attached and on
which the body is superimposed.
2. Integrated Frame and Body
The integrated frame and body type of construction also referred to as unitized construction,
combines the frame and body into a single, one-piece structure. This is done by welding the

5. components together, by forming or casting the entire structure as one piece, or by a combination
of these techniques. Simply by welding a body to a conventional frame, however, does not constitute
an integral frame and body construction. In a truly integrated structure, the entire frame-body unit
is treated as a load-carrying member that reacts to all Integrated-type bodies for wheeled vehicles
are fabricated by welding preformed metal panels together. The panels are preformed in various
load-bearing shapes that are located and oriented so as to result in a uniformly stressed structure.
Some portions of the integrated structure resemble frame like components, while others resemble
body like panels. This is not surprising, because the structure must perform the functions of both of
these elements. An integrated frame and body type construction allows and increases in the amount
of noise transmitted into the passenger compartment of the vehicle. However, this disadvantage is
negated by the following advantages:
1. Substantial weight reduction, which is possible when using a well-designed unitized body,
2. Lower cargo floor and vehicle height,
3. Protection from mud and water required for driveline components on amphibious vehicles.
4. Reduction in the amount of vibration present in the vehicle structure.
For larger trucks, the frames are simple, rugged, and of channel iron construction. The side rails are
parallel to each other at standardized widths to permit the mounting of stock transmissions, transfer
cases, rear axles, and other similar components. Trucks that are to be used as prime movers have an
additional reinforcement of the side rails and rear cross members to compensate for the added
towing stresses
Frame Maintenance
Frames require little, if any, maintenance. However, if the frame is bent enough to cause
misalignment of the vehicle or cause faulty steering, the vehicle should be taken off of the road.
Drilling the frame and fish plating can temporarily repair small cracks in the frame side rails. Care
should be exercised when performing this task, as the frame can be weakened. The frame of the
vehicle should not be welded by gas or arc welding unless specified by the manufacturer. The heat
removes temper from the metal, and, if cooled too quickly, causes the metal to crystallize. Minor
bends can be removed by the use of hydraulic jacks, bars and clamps.
Four wheel drive:
There are almost as many different types of four-wheel-drive systems as there are four-wheel drive
vehicles. It seems that every manufacturer has several different schemes for providing power to all of
the wheels. The terminology used as follows:
1. Four-wheel drive - Usually, when carmakers say that a car has four-wheel drive, they are
referring to a part-time system. These systems are meant only for use in low-traction
conditions, such as off-road or on snow or ice.
2. All-wheel drive - These systems are sometimes called full-time four-wheel drive. All-wheel
drive systems are designed to function on all types of surfaces, both on- and off-road, and
most of them cannot be switched off. Part-time and full-time four-wheel-drive systems can
be evaluated using the same criteria. The best system will send exactly the right amount of
torque to each wheel, which is the maximum torque that won't cause that tire to slip.
Braking System

6. The safe and reliable use of a road vehicle necessitates the continual adjustment of its speed and
distance in response to change in traffic conditions. This requirement is met in part by the braking
system, the design of which plays a key role in ensuring a particular vehicle is suitable for a given
application. This is achieved through the design of a system that makes as efficient use as possible of
the finite amount of traction available between the tyre and the road over the entire range of
operating conditions that are likely to be encountered by the vehicle during normal operation.
The Functions and Conditions of use of a Brake System
In order to understand the behaviour of a braking system it is useful to define three separate
functions that must be fulfilled at all times:
(a) The braking system must decelerate a vehicle in a controlled and repeatable fashion and when
appropriate cause the vehicle to stop.
(b) The braking system should permit the vehicle to maintain a constant speed when travelling
downhill.
(c) The braking system must hold the vehicle stationary when on a flat or on a gradient.
Consideration of the diverse conditions under which the brakes must operate leads to a better
appreciation of their role. These include, but are not limited to, the following:
_ slippery wet and dry roads.
_ rough or smooth road;
_ split friction surfaces;
_ straight line braking or when braking on a curve;
_ wet or dry brakes;
_ new or worn linings;
_ laden or unladen vehicle;
_ vehicle pulling a trailer or caravan;
_ frequent or infrequent applications of short or lengthy duration;
_ high or low rates of deceleration;
_ skilled or unskilled drivers.
Clearly the brakes, together with the steering components and tyres, represent the most important
accident avoidance systems present on a motor vehicle which must reliably operate under various
conditions. The effectiveness of any braking system is, however, limited by the amount of traction
available at the tyre–road interface.

7. The primary functions of a brake system, listed above, must be fulfilled at all times. In the event of a
system failure, the same functions must also be performed albeit with a reduced efficiency.
Consequently, the braking system of a typical passenger car comprises a service brake for normal
braking, a secondary/emergency brake used in the event of a service brake failure and a parking
brake. Current practice permits service brake components to be used in the secondary/parking brake
systems.
Irrespective of the detail design considerations all brake systems divide into the following
subsystems:
(1) Energy source
This includes all those components which generate, store or release energy required by the braking
system. In standard passenger cars muscular pedal effort, applied by the driver, in combination with
a vacuum boost system comprise the energy source. In the event of a boost failure, the driver can
still apply the brakes by muscular effort alone. Alternative sources of energy include power braking
systems, surge brakes, drop weight brakes, electric and spring brakes.
(2) Modulation system
This embraces those elements of the brake system which are used to control the level of braking
effort applied to each brake. Included in this system are the driver, pressure limiting/modulating
values and, if fitted, anti-lock braking systems (ABSs).
(3) Transmissionsystem
The components through which energy travels to the wheel brakes comprise the transmission
system. Brake lines (rigid tubes) and brake hoses (flexible tubes) are used in hydraulic and air brake
systems. Mechanical brakes make use of rods, levers, cams and cables to transmit energy. The
parking brake of a car quite often makes use of a mechanical transmission system.
(4) Foundation brakes
These assemblies generate the forces that oppose the motion of the vehicle and in doing so convert
the kinetic energy associated with the longitudinal motion of the vehicle into heat.
Principle
Brakes are required to stop the vehicle within the smallest possible distance and this is done by
converting the kinetic energy of the vehicle into the heat energy which is dissipated into the
atmosphere.
Brakes are employed to stop or slow down the speed of a vehicle. When brake is applied to wheel,
braking force is created. This force opposes the speed of wheel or rotation of force.
Braking requirement:
1) The vehicle must stop in smallest distance.
2) It must act suddenly in emergency.
3) It must have strong braking force.
4) It must neither slip nor skid the vehicle and lead to less heat production.
5) It must operate on least effort.
Types of brakes: Breaks are divided into seven types as per there uses, functionality, locations etc.
1) On the basis of purpose saved.
a) Main brake.
b) Parking brake.
2) On the basis of location.
a) Wheel mounted.
b) Transmission mounted.
3) On the basis of drivers ergonomics.
a) Foot brake.
b) Hand brake.

8. 4) On the basis of actuating.
a) Mechanical brake.
b) Hydraulic brake.
c) Air brake.
d) Electric brake.
5) On the basis of construction.
a) Drum brake.
b) Disc brake.
6) On the basis of application of brake efforts.
a) Manual brake.
b) Power brake.
c) Power assisted.
7) On the basis of action of brake shoes.
a) Internal expanding brake.
b) External contracting brake.
Brake Drum:
Construction of Brake Drum:
The brake drum is mounted on the axle hub and the whole assembly is held in the wheel. The brake
shoes are handled on the back plate by means of pin expander which is fitted in between shoes. The
friction material is pasted or biretta on brake shoes. Due to friction action, brake is applied.
Following parts are used in break drum:
1) Brake drum.
2) Back plate.
3) Brake shoe.

9. 4) Brake lining.
5) Expander.
6) Anchor.
7) Returning spring.
8) Adjuster.
Disc brake:
Construction of disc break:
1) Caliper or cylinder casing.
2) Rooter disc.
3) Piston.
4) Friction pad.
5) Pad supporting plate.
6) Bleeder plug.
Mechanical Brakes
• Mechanical brakes are invariably based on the frictional resistance principles
• In mechanical brakes artificial resistances created using frictional contact between the moving
member and a stationary member, to retard or stop the motion of the moving member.
Basic mechanism of braking
An element dA of the stationary member is shown with the braked body moving past at velocity v.
When the brake is actuated contact is established between the stationary and moving member and a
normal pressure is developed in the contact region. The elemental normal force dN is equal to the
product of contact pressure p and area of contact dA. As one member is stationary and the other is
in relative motion, a frictional force dF is developed between the members. The magnitude of the
frictional force is equal to the co-efficient of friction times the normal force
Mathematically,
dFf =µ.dN=µ.p.dA
dN=p.dA.

10. The moment of the frictional force relative to the point of motion contributes to the retardation of
motion and braking.
Design and Analysis
To design, select or analyze the performance of these devices knowledge on the following are
required.
• The braking torque
• The actuating force needed
• The energy loss and temperature rise
Torque induced is related to the actuating force, the geometry of the member and other contact
conditions. Most mechanical brakes that work on the frictional contact basis are classified based on
the geometry. There are two major classes of brakes, namely drum brakes and disc brakes. Drum
brakes basically consists of a rotating body called drum whose motion is braked together with a shoe
mounted on a lever which can swing freely about a fixed hinge H. A lining is attached to the shoe
and contacts the braked body. The actuation force P applied to the shoe gives rise to a normal
contact pressure distributed over the contact area between the lining and the braked body. A
corresponding friction force is developed between the stationary shoe and the rotating body which
manifest as retarding torque about the axis of the braked body.
Brakes Classification:
Drum Brakes are classified based on the shoe geometry.
Shoes are classified as being either short or long. A short shoe is one whose lining dimension in the
direction of motion is so small that contact pressure variation is negligible, i.e. the pressure is
uniform everywhere. When the area of contact becomes larger, the contact may no longer be with a
uniform pressure, in which case the shoe is termed as long shoe. The shoes are either rigid or
pivoted, pivoted shoes are also some times known as hinged shoes. The shoe is termed rigid because
the shoes with attached linings are rigidly connected to the pivoted posts. In a hinged shoe brake -
the shoes are not rigidly fixed but hinged or pivoted to the posts. The hinged shoe is connected to
the actuating post by the hinge, G, which introduces another degree of freedom Preliminary Analysis
The figure shows a brake shoe mounted on a lever, hinged at O, having an actuating force Fa,
applied at the end of the lever. On the application of an actuating force, a normal force Fn is created
when the shoe contacts the rotating drum. And a frictional force Ff of magnitude f.Fn, f being the
coefficient of friction, develops between the shoe and the drum. Moment of this frictional force
about the drum center constitutes the braking torque.
Short Shoe Analysis

11. For a short shoe we assume that the pressure is uniformly distributed over the contact area.
Consequently the equivalent normal force Fn = p .A, where p is the contact pressure and A is the
surface area of the shoe. Consequently the friction force Ff = f.Fn where f is the co-efficient of
friction between the shoe lining material and the drum material. The torque on the brake drum is
then, T = f Fn. r = f.p.A.r A quasi static analysis is used to determine the other parameters of
braking.
Substituting for Fn and solving for the actuating force, we get,
Fa = Fn(b+-fc)/a
Leading and trailing shoe
• For a given direction of rotation the shoe in which self energization is present is known as the
leading shoe
• When the direction of rotation is changed, the moment of frictional force now will be opposing the
actuation force and hence greater magnitude of force is needed to create the same contact pressure.
The shoe on which this is prevailing is known as a trailing shoe Self Locking At certain critical value
of f.c the term (b-fc) becomes zero. i.e no actuation force need to be applied for braking. This is the
condition for self-locking. Self-locking will not occur unless it is specifically desired.
Fading of Brakes
With prolonged application of brakes, their effectiveness decreases. This is called fading of brakes.
This happens on account of reversible changes in the friction properties of the brake linings on
account of high temperatures produced due to prolonged application. However, because such
property changes are reversible, usual effectiveness of the brake is restored when they cool off.