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UNIT-V

Suspension system;
Suspension system is the term given to the system of springs, shock absorbers and linkages
that connects a vehicle to its wheels . It is basically cushion for passengers protects the luggage or
any cargo and also itself from damage and wear.

Sir William Brush is the father of suspension system in automobiles.

The main role of suspension system are as follows:

⚫ It supports the weight of vehicle .
⚫ Provides smoother ride for the driver and passengers i.e. acts as cushion.
⚫ Protects your vehicle from damage and wear .
⚫ It also plays a critical role in maintaining self driving conditions.
⚫ It also keeps the wheels pressed firmly to the ground for traction .
⚫ It isolates the body from road shocks and vibrations which would otherwise be
transferred to the passengers and load.

Principle :
When a tire hits an obstruction, there is a reaction force. The size of this reaction force
depends on the unsprung mass at each wheel assembly.

In general, the larger the ratio of sprung weight to unsprung weight, the less the body and
vehicle occupants are affected by bumps, dips, and other surface imperfections such as small
bridges. A large sprung weight to unsprung weight ratio can also impact vehicle control.

No road is perfectly flat i.e. without irregularities. Even a freshly paved highways have
subtle imperfections that can be interact with vehicle’s wheels. These are the imperfections that
apply forces on wheels.
According to Newton ‘s law of motion all forces have both magnitude and direction. A
bump in the road causes the wheel to move up and down perpendicular to the road surface. The
magnitude of course ,depends on whether the wheel is striking a giant bump or a tiny speck. Thus,
either the wheel experiences a vertical acceleration as it passes over an imperfection.

The suspension of a car is actually part of the chassis, which comprises all of the important
systems located beneath the car's body. These system include :
⚫ Frame
⚫ Suspension system
⚫ Steering system
⚫ Tires or Wheels

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Components of Suspension system;

There are three fundamental components of any suspension system .
⚫ Springs
 Coil spring
 Leaf springs
 Air springs
⚫ Dampers
 Shock Absorbers
 Struts:-
 Anti-sway Bars
⚫ Anti sway bars.
Types of Suspension system;

Advantages;

⚫ Comfort to passengers
⚫ Good handling
⚫ Shields the vehicle from damage
⚫ Increases life of vehicle
⚫ Keeps the tires pressed firmly to ground.
Braking System;
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A brake is a mechanical device which inhibits motion, slowing or stopping a moving object
or preventing its motion. The rest of this article is dedicated to various types of vehicular brakes.

Most commonly brakes use friction between two surfaces pressed together to convert
the kinetic energy of the moving object 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
tored forms as pressurized air or pressurized oil. Eddy current brakes use magnetic fields to
convert kinetic energy into electric current in the brake disc, fin, or rail, which is converted into heat.
Still other braking methods even transform kinetic ene energy
rgy 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.
Since kinetic energy increases quadratically with velocity ( ), an object
moving at 10 m/s has 100 times as much energy as one of the same mass moving at 1 m/s, and
consequently the theoretical braking distance, when braking at the traction limit, is 100 times as
long. In practice, fast vehicles usually have significant air drag, and energy lost to air drag rises
quickly with speed. Almost all wheeled vehicles have a brake of some sort. Even baggage
carts and shopping carts may have them for use on a moving ramp. Most fixed-wing
fixed aircraft are
fitted with wheel brakes on the undercarriage. Some aircraft also feature air brakes designed to
reduce their speed in flight.

Notable examples include gliders and some World War II II-era

era aircraft, primarily some fighter
aircraft and many dive bombers of the era. These allow the aircraft to maintain a safe speed in a
steep descent. The Saab B 17 dive bomber and Vought F4U Corsair fighter used the deployed
undercarriage as an air brake. Friction brakes on automobiles store braking heat in the drum
brake or disc brake while braking then conduct it to the air gradually. When traveling downhill some
vehicles can use their engines to brake.

When the brake pedal of a modern vehicle with hydraulic brakes is pushed, ultimately
a piston pushes the brake pad against the brake disc which slows the wheel down. On the brake
drum it is similar as the cylinder pushes the brake shoes against the drum which also slows the
wheel down. Brakes may be broadly described as using friction, pumpumping,
ping, or electromagnetic. One
brake may use several principles: for example, a pump may pass fluid through an orifice to create
friction: Frictional brakes are most common and can be divided broadly into "shoe" or "pad" brakes,
using an explicit wear surface,
ce, and hydrodynamic brakes, such as parachutes, which use friction in a
working fluid and do not explicitly wear. Typically the term "friction brake" is used to mean
pad/shoe brakes and excludes hydrodynamic brakes, even though hydrodynamic brakes usefriction.

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Friction (pad/shoe) brakes are often rotating devices with a stationary pad and a rotating
wear surface. Common configurations include shoes that contract to rub on the outside of a rotating
drum, such as a band brake; a rotating drum with shoes that expand to rub the inside of a drum,
commonly called a "drum brake", although other drum configurations are possible; and pads that
pinch a rotating disc, commonly called a "disc brake".

Other brake configurations are used, but less often. For example, PCC trolley brakes include
a flat shoe which is clamped to the rail with an electromagnet; the Murphy brake pinches a rotating
drum, and the Ausco Lambert disc brake uses a hollow disc (two parallel discs with a structural
bridge) with shoes that sit between the disc surfaces and expand laterally. Pumping brakes are often
used where a pump is already part of the machinery. For example, an internal-combustion piston
motor can have the fuel supply stopped, and then internal pumping losses of the engine create some
braking. Some engines use a valve override called a Jake brake to greatly increase pumping losses.
Pumping brakes can dump energy as heat, or can be regenerative brakes that recharge a pressure
reservoir called a hydraulic accumulator.

Electromagnetic brakes are likewise often used where an electric motor is already part of the
machinery. For example, many hybrid gasoline/electric vehicles use the electric motor as a generator
to charge electric batteries and also as a regenerative brake. Some diesel/electric railroad
locomotives use the electric motors to generate electricity which is then sent to a resistor bank and
dumped as heat.

Types of Braking system in Automobile;

 By applications –
1. Foot Brake,
2. Hand brake.
 By Method of power –
1. Mechanical brake,
2. Hydraulic brake.
3. Vacuum brake,
4. Electrical brake and
5. Air brake.
 By method of operations –
1. Manual brake,
2. Servo brake.
3. Power operation.
 By construction –
1. Drum type brake,
2. Disc type brake.

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Anti-lock braking system (ABS)

Anti-lock braking system (ABS) is an automobile safety system that allows the wheels on
a motor vehicle to maintain tractive contact with the road surface according to driver inputs
while braking, preventing the wheels from locking up (ceasing rotation) and avoiding uncontrolled
skidding. It is an automated system that uses the principles of threshold braking and cadence
braking which were practiced by skillful drivers with previous generation braking systems. It does
this at a much faster rate and with better control than a driver could manage.
ABS generally offers improved vehicle control and decreases stopping distances on dry and
slippery surfaces for many drivers; however, on loose surfaces like gravel or snow-covered
pavement, ABS can significantly increase braking distance, although still improving vehicle control.
Since initial widespread use in production cars, anti-lock braking systems have evolved
considerably. Recent versions not only prevent wheel lock under braking, but also electronically
control the front-to-rear brake bias. This function, depending on its specific capabilities and
implementation, is known as electronic brake force distribution(EBD), traction control system,
emergency brake assist, or electronic stability control(ESC).

Operation
The anti-lock brake controller is also known as the CAB (Controller Anti-lock Brake).
Typically ABS includes a central electronic control unit (ECU), four wheel speed sensors,
and at least two hydraulic valves within the brake hydraulics. The ECU constantly monitors
the rotational speed of each wheel; if it detects a wheel rotating significantly slower than the others,
a condition indicative of impending wheel lock, it actuates the valves to reduce hydraulic pressure to
the brake at the affected wheel, thus reducing the braking force on that wheel; the wheel then turns
faster.
Conversely, if the ECU detects a wheel turning significantly faster than the others, brake
hydraulic pressure to the wheel is increased so the braking force is reapplied, slowing down the
wheel. This process is repeated continuously and can be detected by the driver via brake pedal
pulsation. Some anti-lock systems can apply or release braking pressure 15 times per
second.[17] Because of this, the wheels of cars equipped with ABS are practically impossible to lock
even during panic braking in extreme conditions.
The ECU is programmed to disregard differences in wheel rotative speed below a critical
threshold, because when the car is turning, the two wheels towards the center of the curve turn
slower than the outer two. For this same reason, a differential is used in virtually all roadgoing
vehicles. If a fault develops in any part of the ABS, a warning light will usually be illuminated on
the vehicle instrument panel, and the ABS will be disabled until the fault is rectified.
Modern ABS applies individual brake pressure to all four wheels through a control system of
hub-mounted sensors and a dedicated micro-controller. ABS is offered or comes standard on most
road vehicles produced today and is the foundation for electronic stability control systems, which are
rapidly increasing in popularity due to the vast reduction in price of vehicle electronics over the
years.
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Modern electronic stability control systems are an evolution of the ABS concept. Here, a
minimum of two additional sensors are added to help the system work: these are a steering
wheel angle sensor, and a gyroscopic sensor. The theory of operation is simple: when the gyroscopic
sensor detects that the direction taken by the car does not coincide with what the steering wheel
sensor reports, the ESC software will brake the necessary individual wheel(s) (up to three with the
most sophisticated systems), so that the vehicle goes the way the driver intends. The steering wheel
sensor also helps in the operation of Cornering Brake Control (CBC), since this will tell the ABS
that wheels on the inside of the curve should brake more than wheels on the outside, and by how
much.
ABS equipment may also be used to implement a traction control system (TCS) on
acceleration of the vehicle. If, when accelerating, the tire loses traction, the ABS controller can
detect the situation and take suitable action so that traction is regained. More sophisticated versions
of this can also control throttle levels and brakes simultaneously.

Components of ABS
There are four main components of ABS:
 Speed sensors,
 Valves,
 Pump, and
 Controller.
Speed sensors
A speed sensor is used to determine the acceleration or deceleration of the wheel. These
sensors use a magnet and a coil of wire to generate a signal. The rotation of the wheel or differential
induces a magnetic field around the sensor. The fluctuations of this magnetic field generate a voltage
in the sensor. Since the voltage induced in the sensor is a result of the rotating wheel, this sensor can
become inaccurate at slow speeds. The slower rotation of the wheel can cause inaccurate
fluctuations in the magnetic field and thus cause inaccurate readings to the controller.
Valves
There is a valve in the brake line of each brake controlled by the ABS. On some systems, the
valve has three positions:
In position one, the valve is open; pressure from the master cylinder is passed right through
to the brake.
In position two, the valve blocks the line, isolating that brake from the master cylinder. This
prevents the pressure from rising further should the driver push the brake pedal harder.
In position three, the valve releases some of the pressure from the brake.

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The majority of problems with the valve system occur due to clogged valves. When a valve
is clogged it is unable to open, close, or change position. An inoperable valve will prevent the
system from modulating the valves and controlling pressure supplied to the brakes.

Pump
The pump in the ABS is used to restore the pressure to the hydraulic brakes after the valves
have released it. A signal from the controller will release the valve at the detection of wheel slip.
After a valve release the pressure supplied from the user, the pump is used to restore a desired
amount of pressure to the braking system. The controller will modulate the pumps status in order to
provide the desired amount of pressure and reduce slipping.
Controller
The controller is an ECU type unit in the car which receives information from each
individual wheel speed sensor, in turn if a wheel loses traction the signal is sent to the controller, the
controller will then limit the brake force (EBD) and activate the ABS modulator which actuates the
braking valves on and off.
Use
There are many different variations and control algorithms for use in ABS. One of the
simpler systems works as follows,
The controller monitors the speed sensors at all times. It is looking for decelerations in the
wheel that are out of the ordinary. Right before wheel locks up, it will experience a rapid
deceleration.

If left unchecked, the wheel would stop much more quickly than any car could. It might take
a car five seconds to stop from 60 mph (96.6 km/h) under ideal conditions, but a wheel that locks up
could stop spinning in less than a second.
The ABS controller knows that such a rapid deceleration is impossible, so it reduces the
pressure to that brake until it sees an acceleration, then it increases the pressure until it sees the
deceleration again. It can do this very quickly, before the tire can actually significantly change
speed. The result is that the tire slows down at the same rate as the car, with the brakes keeping the
tires very near the point at which they will start to lock up. This gives the system maximum braking
power.
This replaces the need to manually pump the brakes while driving on a slippery or a low
traction surface, allowing steering even in the most emergency braking conditions.
When the ABS is in operation the driver will feel a pulsing in the brake pedal; this comes
from the rapid opening and closing of the valves. This pulsing also tells the driver that the ABS has
been triggered. Some ABS systems can cycle up to 16 times per second.

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Hydraulic braking system

The disc brake or disk brake is a device for slowing or stopping the rotation of a wheel while
it is in motion. A brake disc (or rotor in U.S. English) is usually made of cast iron, but may in some
cases be made of composites such as reinforced carbon-carbon or ceramic-matrix composites.

This is connected to the wheel and/or the axle. To stop the wheel, friction material in the
form of brake pads (mounted on a device called a brake caliper) is forced mechanically,
hydraulically, pneumatically or electromagnetically against both sides of the disc. Friction causes
the disc and attached wheel to slow or stop. Brakes (both disc and drum) convert motion to heat, but
if the brakes get too hot, they will become less effective because they cannot dissipate enough heat.
This condition of failure is known as brake fade.

Construction of Braking system;

The most common arrangement of hydraulic brakes for passenger vehicles, motorcycles,
scooters, and mopeds, consists of the following:
 Brake pedal or lever
 A pushrod (also called an actuating rod)
 A master cylinder assembly containing a piston assembly
 Reinforced hydraulic lines
Brake caliper assembly usually consisting of one or two hollow aluminum or chrome-plated
steel pistons (called caliper pistons), a set of thermally conductive brake pads and a rotor (also called
a brake disc) or drum attached to an axle.The system is usually filled with a glycol-ether based brake
fluid (other fluids may also be used).
At one time, passenger vehicles commonly employed drum brakes on all four wheels. Later,
disc brakes were used for the front and drum brakes for the rear. However disc brakes have shown
better heat dissipation and greater resistance to 'fading' and are therefore generally safer than drum
brakes. So four-wheel disc brakes have become increasingly popular, replacing drums on all but the
most basic vehicles. Many two-wheel vehicle designs, however, continue to employ a drum brake
for the rear wheel.The following description uses the terminology for and configuration of a simple
.
In a hydraulic brake system, when the brake pedal is pressed, a pushrod exerts force on the
piston(s) in the master cylinder, causing fluid from the brake fluid reservoir to flow into a pressure
chamber through a compensating port. This results in an increase in the pressure of the entire
hydraulic system, forcing fluid through the hydraulic lines toward one or more calipers where it acts
upon one or two caliper pistons sealed by one or more seated O-rings (which prevent leakage of the
fluid).

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The brake caliper pistons then apply force to the brake pads, pushing them against the
spinning rotor, and the friction between the pads and the rotor causes a brakingtorque to be
generated, slowing the vehicle. Heat generated by this friction is either dissipated through vents and
channels in the rotor or is conducted through the pads, which are made of specialized heat-tolerant
materials such as kevlar orsintered glass.
Subsequent release of the brake pedal/lever allows the spring(s) in my master cylinder
assembly to return the master piston(s) back into position. This action first relieves the hydraulic
pressure on the caliper, then applies suction to the brake piston in the caliper assembly, moving it
back into its housing and allowing the brake pads to release the rotor.
The hydraulic braking system is designed as a closed system: unless there is a leak in the
system, none of the brake fluid enters or leaves it, nor does the fluid get consumed through use.

Pneumatic braking system

An air brake or, more formally, a compressed air brake system, is a type of friction brake for
vehicles in which compressed air pressing on a piston is used to apply the pressure to the brake
pad needed to stop the vehicle.
Air brakes are used in large heavy vehicles, particularly those having multiple trailers which
must be linked into the brake system, such as trucks, buses, trailers, and semi-trailers in addition to
their use in railroad trains.
George Westinghouse first developed air brakes for use in railway service. He patented a
safer air brake on March 5, 1872. Westinghouse made numerous alterations to improve his air
pressured brake invention, which led to various forms of the automatic brake. In the early 20th
century, after its advantages were proven in railway use, it was adopted by manufacturers of trucks
and heavy road vehicles.

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Construction of Braking system;

Air brake systems are typically used on heavy trucks and buses. The system consists of
service brakes, parking brakes, a control pedal, and an air storage tank. For the parking brake, there
is a disc or drum brake arrangement which is designed to be held in the 'applied' position by spring
pressure.
Air pressure must be produced to release these "spring brake" parking brakes. For the service
brakes (the ones used while driving for slowing or stopping) to be applied, the brake pedal is pushed,
routing the air under pressure (approx 100–120 psi or 690–830 kPa) to the brake chamber, causing
the brake to be engaged. Most types of truck air brakes are drum brakes, though there is an
increasing trend towards the use of disc brakes in this application. The air compressor draws filtered
air from the atmosphere and forces it into high-pressure reservoirs at around 120 psi (830 kPa).
Most heavy vehicles have a gauge within the driver's view, indicating the availability of air
pressure for safe vehicle operation, often including warning tones or lights. Setting of the
parking/emergency brake releases the pressurized air in the lines between the compressed air storage
tank and the brakes, thus allowing the spring actuated parking brake to engage. A sudden loss of air
pressure would result in full spring brake pressure immediately.
A compressed air brake system is divided into a supply system and a control system. The supply
system compresses, stores and supplies high-pressure air to the control system as well as to
additional air operated auxiliary truck systems (gearbox shift control, clutch pedal air
assistance servo, etc.).

Highly simplified air brake diagram on a commercial road vehicle (does not show all air
reservoirs and all applicable air valves). The air compressor is driven by the engine either
by crankshaft pulley via a beltor directly from the engine timing gears. It is lubricated and cooled by
the engine lubrication and cooling systems.

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Compressed air is first routed through a cooling coil and into an air dryer which removes
moisture and oil impurities and also may include a pressure regulator, safety valve and smaller purge
reservoir. As an alternative to the air dryer, the supply system can be equipped with an anti-freeze
device and oil separator. The compressed air is then stored in a reservoir (also called a wet tank)
from which it is then distributed via a four way protection valve into the front and rear brake circuit
air reservoir, a parking brake reservoir and an auxiliary air supply distribution point. The system also
includes various check, pressure limiting, drain and safety valves.Air brake systems may include
a wig wag device which deploys to warn the driver if the system air pressure drops too low.
Control system
The control system is further divided into two service brake circuits: the parking brake
circuit and the trailer brake circuit. This dual brake circuit is further split into front and rear wheel
circuits which receive compressed air from their individual reservoirs for added safety in case of an
air leak. The service brakes are applied by means of a brake pedal air valve which regulates both
circuits.
The parking brake is the air operated spring brake type where its applied by spring force in
the spring brake cylinder and released by compressed air via hand control valve. The trailer brake
consists of a direct two line system: the supply line (marked red) and the separate control or service
line (marked blue). The supply line receives air from the prime mover park brake air tank via a park
brake relay valve and the control line is regulated via the trailer brake relay valve. The operating
signals for the relay are provided by the prime mover brake pedal air valve, trailer service brake
hand control (subject to a country's relevant heavy vehicle legislation) and the prime mover park
brake hand control.

Advantages of Air Brakes;

Air brakes are used as an alternative to hydraulic brakes which are used on lighter vehicles such
as automobiles. Hydraulic brakes use a liquid (hydraulic fluid) to transfer pressure from the brake
pedal to the brake shoe to stop the vehicle. Air brakes have several advantages for large multitrailer
vehicles:

 The supply of air is unlimited, so the brake system can never run out of its operating fluid, as
hydraulic brakes can. Minor leaks do not result in brake failures.
 Air line couplings are easier to attach and detach than hydraulic lines; there is no danger of
letting air into hydraulic fluid. So air brake circuits of trailers can be attached and removed
easily by operators with little training.
 Air not only serves as a fluid for transmission of force, but also stores potential energy. So it
can serve to control the force applied. Air brake systems include an air tank that stores sufficient
energy to stop the vehicle if the compressor fails.
 Air brakes are effective even with considerable leakage, so an air brake system can be
designed with sufficient "fail-safe" capacity to stop the vehicle safely even when leaking.

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Introduction of Steering system

Steering is the collection of components, linkages, etc. which allow a vessel (ship,boat)
or vehicle (car, motorcycle, bicycle) to follow the desired course. An exception is the case of rail
transport by which rail tracks combined together with railroad switches (and also known as 'points'
in British English) provide the steering function.

The most conventional steering arrangement is to turn the front wheels using a hand–
operated steering wheel which is positioned in front of the driver, via the steering column, which
may contain universal joints (which may also be part of the collapsible steering column design), to
allow it to deviate somewhat from a straight line. Other arrangements are sometimes found on
different types of vehicles, for example, a tiller or rear–wheel steering. Tracked vehicles such
as bulldozers andtanks usually employ differential steering — that is, the tracks are made to move at
different speeds or even in opposite directions, using clutches and brakes, to bring about a change of
course or direction.

Wheeled vehicle steering - Basic geometry

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Ackermann steering geometry

Caster angle θ indicates kingpinpivot line and gray area indicates vehicle's tire with the
wheel moving from right to left. A positive caster angle aids in directional stability, as the wheel
tends to trail, but a large angle makes steering more difficult.
Curves described by the rear wheels of a conventional automobile. While the vehicle moves
with a constant speed its inner and outer rear wheels do not.
The basic aim of steering is to ensure that the wheels are pointing in the desired directions.
This is typically achieved by a series of linkages, rods, pivots and gears. One of the fundamental
concepts is that of caster angle – each wheel is steered with a pivot point ahead of the wheel; this
makes the steering tend to be self-centering towards the direction of travel.
The steering linkages connecting the steering box and the wheels usually conforms to a
variation of Ackermann steering geometry, to account for the fact that in a turn, the inner wheel is
actually travelling a path of smaller radius than the outer wheel, so that the degree of toe suitable for
driving in a straight path is not suitable for turns. The angle the wheels make with the vertical plane
also influences steering dynamics (see camber angle) as do the tires.

Rack and pinion, recirculating ball, worm and sector

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Rack and pinion steering mechanism:

1. Steering wheel;
2. Steering column;
3. Rack and pinion;
4. Tie rod;
5. Kingpin

Rack and pinion unit mounted in the cockpit of an Ariel Atom sports car chassis. For most
high volume production, this is usually mounted on the other side of this panel

Steering box of a motor vehicle, the traditional (non-assisted), you may notice that the
system allows you to adjust the braking and steering systems, you can also see the attachment
system to the frame.
Many modern cars use rack and pinion steering mechanisms, where the steering wheel turns
the pinion gear; the pinion moves the rack, which is a linear gear that meshes with the pinion,
converting circular motion into linear motion along the transverse axis of the car (side to side
motion). This motion applies steering torque to the swivel pin ball joints that replaced previously
used kingpins of the stub axle of the steered wheels via tie rods and a short lever arm called the
steering arm.
The rack and pinion design has the advantages of a large degree of feedback and direct
steering "feel". A disadvantage is that it is not adjustable, so that when it does wear and
develop lash, the only cure is replacement.
Older designs often use the recalculating ball mechanism, which is still found on trucks and
utility vehicles. This is a variation on the older sector design; the steering column turns a large screw
(the "worm gear") which meshes with a sector of a gear, causing it to rotate about its axis as the
worm gear is turned; an arm attached to the axis of the sector moves the Pitman arm, which is
connected to the steering linkage and thus steers the wheels. The recalculating ball version of this
apparatus reduces the considerable friction by placing large ball bearings between the teeth of the
worm and those of the screw; at either end of the apparatus the balls exit from between the two
pieces into a channel internal to the box which connects them with the other end of the apparatus,
thus they are "recalculated".
The recirculating ball mechanism has the advantage of a much greater mechanical advantage,
so that it was found on larger, heavier vehicles while the rack and pinion was originally limited to
smaller and lighter ones; due to the almost universal adoption of power steering, however, this is no
longer an important advantage, leading to the increasing use of rack and pinion on newer cars.

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The recirculating ball design also has a perceptible lash, or "dead spot" on center, where a
minute turn of the steering wheel in either direction does not move the steering apparatus; this is
easily adjustable via a screw on the end of the steering box to account for wear, but it cannot be
entirely eliminated because it will create excessive internal forces at other positions and the
mechanism will wear very rapidly. This design is still in use in trucks and other large vehicles,
where rapidity of steering and direct feel are less important than robustness, maintainability, and
mechanical advantage.
The worm and sector was an older design, used for example in Willys and Chrysler vehicles,
and the Ford Falcon (1960s).
Other systems for steering exist, but are uncommon on road vehicles. Children's toys and go-
karts often use a very direct linkage in the form of abellcrank (also commonly known as a Pitman
arm) attached directly between the steering column and the steering arms, and the use of cable-
operated steering linkages (e.g. the Capstan and Bowstring mechanism) is also found on some home-
built vehicles such as soapbox cars and recumbent tricycles.

Steering Gear Boxes;

The steering gears converts the rotary motion of the steering wheel into the to-and-fro
motion of the link rod of the steering linkages. Moreover it also provides necessary leverage so that
the driver is able to steer the vehicle without fatigue.

There are various types of steering gear boxes are available in automobile.
 Worm and Wheel steering gear box,
 Cam and double roller steering gear box,
 Worm and nut steering gear box,
 Recalculating ball type steering gear box,
 Rack and pinion steering gear box,

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Power steering

In automobiles, power steering (also known as power assisted steering (PAS) or steering
assist system) helps drivers steer by augmenting steering effort of the steering wheel.
Hydraulic or electric actuators add controlled energy to the steering mechanism, so the driver
needs to provide only modest effort regardless of conditions. Power steering helps considerably
when a vehicle is stopped or moving slowly. Also, power steering provides some feedback of forces
acting on the front wheels to give an ongoing sense of how the wheels are interacting with the road;
this is typically called "rοad feel".
Representative power steering systems for cars augment steering effort via an actuator, a
hydraulic cylinder, which is part of a servo system. These systems have a direct mechanical
connection between the steering wheel and the linkage that steers the wheels.
This means that power-steering system failure (to augment effort) still permits the vehicle to
be steered using manual effort alone.
Other power steering systems (such as those in the largest off-road construction vehicles)
have no direct mechanical connection to the steering linkage; they require power. Systems of this
kind, with no mechanical connection, are sometimes called "drive by wire" or "steer by wire", by
analogy with aviation's "fly-by-wire". In this context, "wire" refers to electrical cables that carry
power and data, not thin-wire-rope mechanical control cables.
In other power steering systems, electric motors provide the assistance instead of hydraulic
systems. As with hydraulic types, power to the actuator (motor, in this case) is controlled by the rest
of the power-steering system.
Some construction vehicles have a two-part frame with a rugged hinge in the middle; this
hinge allows the front and rear axles to become non-parallel to steer the vehicle. Opposing hydraulic
cylinders move the halves of the frame relative to each other to steer.
Power steering helps the driver of a vehicle to steer by directing some of the power to assist
in swiveling the steered road wheels about their steering axes. As vehicles have become heavier and
switched to front wheel drive, particularly using negative offset geometry, along with increases in
tire width and diameter, the effort needed to turn the wheels about their steering axis has increased,
often to the point where major physical exertion would be needed were it not for power assistance.
To alleviate this auto makers have developed power steering systems: or more correctly
power-assisted steering—on road going vehicles there has to be a mechanical linkage as a failsafe.
There are two types of power steering systems; hydraulic and electric/electronic. A hydraulic-
electric hybrid system is also possible.A hydraulic power steering (HPS) uses hydraulic pressure
supplied by an engine-driven pump to assist the motion of turning the steering wheel. Electric power
steering (EPS) is more efficient than the hydraulic power steering, since the electric power steering
motor only needs to provide assistance when the steering wheel is turned, whereas the hydraulic
pump must run constantly.

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Department of Mechanical Engineering

 AUTOMOBILE ENGINEERING

In EPS, the amount of assistance is easily tunable to the vehicle

type, road speed, and even driver preference. An added benefit is the
elimination of environmental hazard posed by leakage and disposal of
hydraulic power steering fluid. In addition, electrical assistance is not lost
when the engine fails or stalls, whereas hydraulic assistance stops
working if the engine stops, making the steering doubly heavy as the
driver must now turn not only the very heavy steering—without any
help—but also the power-assistance system itself.
Speed Sensitive Steering
An outgrowth of power steering is speed sensitive steering, where
the steering is heavily assisted at low speed and lightly assisted at high
speed. The auto makers perceive that motorists might need to make large
steering inputs while manoeuvering for parking, but not while traveling at
high speed. The first vehicle with this feature was the Citroën SM with
itsDiravi layout[citation needed], although rather than altering the amount
of assistance as in modern power steering systems, it altered the pressure
on a centring cam which made the steering wheel try to "spring" back to
the straight-ahead position. Modern speed-sensitive power steering

systems reduce the mechanical 9o3r electrical assistance as the vehicle

speed increases, giving a more direct feel. This feature is gradually
becoming more common. Department of Mechanical Engineering
 AUTOMOBILE ENGINEERING

Automobile Engineering
(QUESTION BANK)
UNIT-I
1. Discuss about the fuel supply system in S.I. engine.
2. Explain about the different types of air filters.
3. Explain about the formation of spray in C.I. engine.
4. Discuss about the chassis and body components in automobile. 5. Explain how a four
wheel drive mechanism offers better power transmission in a automobile.
6. Explain with a simple schematic diagram, working of a four wheel drive automobile.
7. Describe in detail about the multipoint fuel injection for S.I. engines.
8. Write about oil pumps and engine service?
9. Write about splash and pressure lubrication systems?
10.Explain how the power can be transmitted in front wheel drive by using a neat
diagram?
11. Sketch a chassis of any four wheelers and mark various parts on it. Explain the
functions of various components of automobile.
12. How can turbo-charging improve performance of an
engine?

UNIT-II
1. What do you mean by the term “Ignition”? How is it related with “combustion”?
2. Sketch and explain different types of Ignition systems used in automotive engines.
3. Why lubrication system is essential in a automobile, explain working of
pressurized lubrication system.
4. Explain in detail about the liquid cooling system with a diagram.
5. Discuss about the bendix drive mechanism. 6. Explain why engines
should not be sub-cooled.
7. Explain about horn, wiper, fuel gauge and engine temperature
indicator?

UNIT-III
1. What are the pollution standards for automobile?
2. Discuss different energy alternatives with their merits and demerits.
3. What are the advantages of using hydrogen as fuel?
4. What are the merits and demerits of biomass?
5. Explain about central locking and electric windows?
6. Write about thermal and catalytic converters?
7. Explain the use of alternative fuels for emission control?
8. Explain the mechanism of pollutants formation?
9. Explain briefly the methods available to control emissions from a automobile.
10. Explain with relevant sketches, working of electric windows in a automobile.
11. Explain Compensated voltage control with the help of a diagram. 12.
Name the various electrical components used in an automobile & give their
functions?
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UNIT-IV
1. Explain with a simple sketch, working of centrifugal typeDoefpcarlutm
tcehntaonfdMwehcy
hafnrieceal Engineering
play should be provided for clutch.
2. Draw and explain with a simple sketch, working of a constant mesh gear box.
 AUTOMOBILE ENGINEERING
3. Describe in detail about single plate clutch with a neat diagram.
4. Explain about the differential rear axle with neat sketch.
5. What are the functions of universal joint and Propeller shaft?
6. Discuss the working principles of i) Torque tube drive. ii) Hotchkiss drive.
7. Explain about sliding mesh and synchro mesh gear boxes with neat diagrams?
8. Explain about magnetic clutch and fluid fly wheel in detail?
9. Write about functions of a propeller shaft and Hotch – Kiss drive?

UNIT-V
1. Explain with a simple sketch, working of worm and ball bearing nut steering mechanism.
2. What are the functions of steering system, explain with relevant sketch Ackerman steering
mechanism.
3. Explain with a schematic diagram, working of rigid axle front wheel suspension system.
4. Discuss about the Davis steering mechanism in the automobiles.
5. Describe about the mechanical brake system.
6. Explain the Davis Steering Mechanism? Write its relative merits?
7. Explain about steering geometry in detail?
8. Sketch the arrangement of pneumatic braking system used in automobiles and explain?
9. Explain about the types of steering gears?
10. Describe the cam and roller type of Steering Gear with neat diagram?

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Department of Mechanical Engineering