Automobile Engineering Notes

SEM -VII Descriptive Type Question
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GeekAlign Notes
Automobile Engineering (DLOC) | Semester 7
BY - Amit Mahto

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AUTOMOBILE ENGINEERING (B.E MECH SEM -7)
Important Questions With Answers –Module wise (5/10 marks questions)
MODULE NO 1
Q1. Classify gear box and Explain synchromesh gearbox with sketch.
The following are four different types of gearbox
➢ Sliding mesh type gearbox
➢ Constant mesh type gearbox
➢ Synchromesh gearbox
➢ Epicyclic gearbox
❖ Synchromesh gearbox
Explanation:-
Diagram of
synchromesh
gearbox

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• The modern cars use helical gears and synchromesh devices in the gearboxes,
that synchronize the rotation of gears that are about to mesh.
• This eliminates clashing of the gears and makes gear shifting easier.
• It is similar to the constant mesh gearbox.
• It is provided with a synchromesh device by which the two gears to be engaged
are first taken into frictional contact which adjusts their speed after which they
are engaged easily.
• In most of the vehicles, the synchromesh devices are not fitted to all the gears.
• They are fitted only on the top gears. Reverse gear, and in some case the first
gear, do not have synchromesh devices.
• Because they are intended to be engaged when the vehicle is stationary.
• When the gear lever is moved the synchromesh cone meets with a similar cone
on the pinion.
• Due to friction the rotating pinion is, made to rotate at the same speed as the
synchromesh unit.
• To give a positive drive further movement of the gear lever enables the coupling
to override several springs loaded balls and the coupling engages with the dogs
on the ride of the pinion.
• Since both pinion and synchromesh units are moving at the same speed, this
engagement is necessary before engaging the dog teeth so that the cones have
a chance to bring the synchronizer and pinion to the same speed.
Q2. Classify gear box and explain sliding mesh gear box with diagram.
• It is the simplest type of gearbox.

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• The arrangement of gears is in a neutral position.
• The gear housing and bearing are not shown.
• The clutch gear is fixed to the clutch shaft.
• It remains always connected to the drive gear of the counter-shaft.
• Three other gears like first speed, second speed and reverse speed gear are
also rigidly fixed to the countershaft or also known as layshaft.
• Two gears mounted on the splined main shaft which can be slided by the shifter
yoke when the shaft lever is operated.
• The gears are connected to the corresponding gears of the countershaft.
• A reverse idler gear is fixed on another shaft and remain connected to the
reverse gear of the countershaft.
Working of Sliding Mesh Gearbox are as follows:
Gear is Neutral
• In this position of the gear, the engine power is not transmitted to the gear axle.
• When the gear is in neutral the clutch gear is transmitting the power to gear on
the countershaft and the countershaft further not transmitting line power to main
shaft.
• Therefore the output of the gearbox is disconnected with input for the gearbox.
• In a neutral position, just the clutch shaft gear is engaged to the countershaft
gear. Other gears are free, and therefore the transmission main shaft is not
rotating.
First or low-speed gear
• First or low-speed gear, by operating the gear shift lever, the larger gear on the
main shaft is moved along the shaft to mesh with the first gear of the
countershaft.
• In this, the main shaft and the clutch shaft both rotate in the same direction.
• Since the smaller countershaft gear is engaged with the larger main shaft gear,
a gear reduction of approximately 3:1 is obtained.
• That is, the clutch shaft turns three times for each revolution of the main shaft.
• Besides gear reduction in the differential at the rear wheels creates a higher
gear ratio, about 12:1 between the wheels and the engine crankshaft.

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Second speed gear
• By operating the gear shift lever, the larger gear of the main shaft is disengaged
from the first gear of the countershaft and then the smaller gear of the main
shaft meshes with the second gear of the countershaft.
• In second speed gear, the main shaft and the clutch shaft rotates in the same
direction.
• A gear reduction of approximately 2:1 is obtained.
• The differential gear reduction increases this gear ratio to about 8:1.

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Third top or high-speed gear
• By operating the crankshaft lever, the second gears of the main shaft and
countershaft are disengaged, and then the second and top gear of the main
shaft is forced axially against the clutch shaft gear.
• The external teeth of clutch shaft gear mesh with the internal teeth in the second
gear and top gear.
• The main shaft turns with the clutch shaft and a gear ratio of 1:1 is obtained.
• The differential reduction produces a gear ratio of about 4:1 between the engine
crankshaft and the wheels.
Reverse Gear
• Reverse gear, by operating the crankshaft lever, the larger gear of the main
shaft meshes with the reverse idler gear.
• The reverse idler gear is always in mesh with the countershaft reverse gear.
• Interposing the idler gear between the countershaft reverse gear and main shaft
bigger gear, the main shaft turns in the direction opposite to that of the clutch
shaft.
• This changes the rotation of the wheels from forward to backwards so that the
vehicle backs.

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Q3 - Explain double declutching in gearbox
• Double-clutching is a driving technique solely used in manual transmission
vehicles. To understand how it works, the most important thing to know is that
there are three systems involved: the engine, the clutch, and the transmission.
Your engine produces power, the clutch transmits that power to the
transmission, and the transmission sends the power to driven wheels. Each one
of these systems, the engine output shaft, the clutch, and the transmission
output shaft, can all rotate independently.
• The purpose of a clutch is to act as a buffer between the engine and
transmission, so when the speeds are mismatched, the clutch is utilized to sync
the two systems together. The rotation speed of the transmission output shaft,
the shaft that’s sending power to driven wheels, however, is dependent on what
gear the transmission is in. In lower gears, the engine will spin fast relative to

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the transmission output shaft. In high gears, the transmission output shaft will
spin quickly relative to the engine.
• To understand, let’s assume we’re currently in fourth gear, we’re slowing down,
and we need to downshift into third gear. As mentioned, this means we’ll be
shifting the engine to a higher RPM relative to the vehicle speed. Here’s where
understanding the independent role of each system is critical. When you press
in the clutch to downshift, the engine rotates by itself, while the clutch and
transmission output are still rotating together. As you move the gearshift from
fourth, to neutral (before reaching third gear), now the clutch and transmission
are rotating separately. Double clutching means at this point, you release the
clutch, while the transmission is still in neutral. Releasing the clutch pedal links
the engine and clutch together, but the transmission output shaft is rotating
faster, as it’s connected to the driven wheels.
• In order to successfully shift into third gear, at this point you must raise the
engine RPM by pressing the accelerator pedal, raising the rotation speed of the
engine, clutch, and third gear (which is indirectly connected to the clutch) to the
same speed as the transmission output shaft. Next, the clutch is depressed, the
gear selector is moved from neutral to third, and then the clutch is released, all
of this providing a smooth downshift.
Q4 - Explain Constant mesh gearbox with sketch.
• In this type of gearbox, all the gears of the main shaft are in constant mesh with
the corresponding gears of the countershaft (lay shaft).
• As the figure shows sliding two dog clutches are provided on the main shaft.
• The one sliding dog clutch is placed in between the clutch gear and the second
gear, and the other is placed in between the first gear and reverse gear.

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• All gears are free on the splined main shaft.
• Dog clutch slides on the main shaft to rotate with it.
• All the gears on the countershaft are fixed with it.
• When the left-hand dog clutch is made to slide to the left through the gearshift
lever, it meshes with the clutch gear and the top speed gear is achieved.
• When the left-hand log clutch meshes with the second gear, the second speed
gear is obtained.
• Likewise, by sliding the right-hand dog clutch to the left and right, the first gear
and reverse gear are obtained.
• In this type of the gearbox, all the gears are in constant mesh, they are safe
from being damaged and unpleasant grinding sound does not occur while
engaging and disengaging them
Q5 - Explain the requirements of Clutches
• Gradual Engagement: The clutches should be engaged gradually so that the
sudden jerks produced must be avoided.
• Size: The size of the clutch should be so small, so that it can be fit into minimum
space.
• Torque Transmission: The clutch should be so designed, so that it can able to
transfer maximum power through it.
• Heat Dissipation: It should be so designed, so that maximum dissipation of
heat takes place from it.
• Dynamic Balancing: For high speed clutches dynamic balancing is necessary.
• Provision of Clutch Free Pedal: There should be a clutch free pedal in
engaging or disengaging of clutch.
• Ease of Operation: Engaging and disengaging of the clutch should not be
difficult or tiresome to the operator.
• Vibration Damping: The clutch should be so designed, so that the noise or
vibration produced in the transmission can be eliminated easily.
Q6 - Different types of universal joints
➢ Cross type or spider and two yokes type or Hookes Joints
➢ Ball and trunnion type
➢ Constant velocity type universal joint
❖ Cross type or spider and two yokes types or Hookes Joints

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• This joint consists of cross piece or spider and two yokes and because of these
parts it is known as cross type or spider and two yoke type universal joint.
• There are four needle bearings one for each trunnion of the spider, the bearings
are held in place by rings heat drop in to under cuts in the yoke bearings holes.
• One commercial design of the cross type universal joint incorporates a slip joint.
• One yoke is integral with the hub that holds the female end of the slip joint.
• When the joint is used between the propeller shaft and rear axle gear shaft, the
slip joint is omitted so that direct connection is made between two joints.
• Other design of cross type universal joint are ring trunnion type are used in
torque tube drive and cross ball type used in hutch-kiss drive.
❖ Ball and trunnion type universal joint

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• The ball and trunnion type universal joint consists of ball head fastened to the
end of the propeller shaft through which a pin is pressed.
• Two steel balls fit over well the ends of the pin. So that when the assembly
(ball head, pin & balls) is fitted in to the body.
• The balls retain the roller bearings between them and U shaped channels in
the body.
• The centering button and the button spring help to keep the pinion properly
centered .
• The universal joint and propeller shaft assembly is bolted to a companion flange
with the gasket and grease cover between them.
• The rotary motion is carried out through the pin and balls ,the balls can move
back and forth in the channel of the body to compensate for varying angle of
drive at the same time, they act as a slip joint by slipping in to or out of the
channels.
❖ Constant velocity type universal joint
• It consists of two individual universal joints linked by a ball and socket
• The ball and socket splits the end of the two propeller shafts between two
universal joints.
• This type of joint permits uniform because the two joints are operating at the
same angle, the acceleration resulting at any instant from the action of one
universal joint is cancelled out by decele ration of the other and vice versa.
Q7 - Explain different types of axle with sketches
Types of live axles used in vehicles:
➢ Semi-floating axle

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➢ Full floating Axle
➢ Three Quarter Floating Axle
Full floating axle :
• In this type of axle two taper roller bearings are used.
• Bearing are placed between the axle housing and the wheel hub. Since, the
load of the vehicle is supported completely by the axle housing.
• The axle only transmits driving torque. The inner end of the axle is supported in
side gear of differential and outer end have a flange to which wheel hub is
bolted.
• During repair the axle may be removed or replaced from the housing without
disturbing the wheel by removing the nut.
• This type of axle is expensive and heavier than other axle. This type is used in
trucks or heavy commercial vehicles.
Three quarter floating axle:
• This type is a compromise between the full floating type and the semi floating
type.
• In three-quarter floating rear axle, bearings are on the axle casing and hub.
• In this case, major part of vehicle weight is taken by axle casing and not by
axle.
• This is the main advantage of three-quarter floating type over half floating type.
• The axle shafts do not have to withstand any shearing or bending; it has to take
only the end loads and driving torque
• Thus, axle breakdown is less in this case compared to the Semi floating.

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• Even though it is better than the semi floating type, it is not as robust as the full
floating type
Semi floating axle:
• A semi-floating axle is an axle shaft that is connected directly to the wheels and
transfers power to them from the differential.
• One side of the bearing has the axle housing and the other side has the axle
rod.
• This allows the rod to endure the weight of the vehicle and endure the torque
and bending effect.
• Since the rod is enduring the weight and not the assembly, it is able to handle
more weight than a non-floating axle but not as much weight as a full floating
axle.
• Most vehicles on the road which have 4-wheel drive will likely contain a semi-
floating axle.
• These axles are not meant for vehicles that carry too much weight, such as
SUVs and pick-up trucks.
• Semi-floating axles are meant for lighter cars which people drive every day to
work or around their town.
• The axles themselves are lighter which makes them very easy to install in a
vehicle.
Q8 - Different types of Stub Axle
There are four main types of stub axle
1. Elliot.
2. Reverse Elliot.
3. Lamoine.

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4. Reversed Lamoine.
• The Elliot stub axle is attached to the front axle by placing in the yoke end with
a kingpin and cotter to join the two together.
• In Reversed Elliot type stub axle, the arrangement is reversed. In Lamoine type
stub axle, instead of yoke type hinge, an L-shaped spindle is used as shown in
the figure.

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MODULE NO 2
Q1 - Explain the working of differential with sketch.
❖ Construction
• Torque is supplied from the engine, via the transmission, to a drive shaft, which
runs to the final drive unit that contains the differential.
• A spiral bevel pinion gear (P) takes its drive from the end of the propeller shaft,
and is encased within the housing of the final drive unit.
• This meshes with the large spiral bevel ring gear (C), known as the crown wheel.
• The crown wheel gear is attached to the differential carrier or cage, which
contains the sun gears (A & B) and planet pinions (C &D), which are a cluster
of four opposed bevel gears in perpendicular plane.
• The two sun wheel gears drive the axle half shafts connected to the vehicle's
driven wheels.
• The other two planet gears are aligned on a perpendicular axis which changes
orientation with the ring gear's rotation.
Working

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• The Planet pinions are stationary when the vehicle is going a straight road,
and the speeds of both the sun gears are equal, thus torque transmitted is
the same.
• Suppose if the vehicle is making a turn to the right, the main crown wheel
may make N full rotations.
• During that time, the left wheel will make more rotations because it has
further to travel, and the right wheel will make fewer rotations as it has less
distance to travel.
• Now because of the resistance, the right sun gear will rotate at a lesser
speed, say ‘n’ rotations less. The left wheel will rotate at ‘n’ more than the
input speed due to the action of the pinion gears.
• his will give the resultant speed on left wheel as (N+n) rpm and on the right
wheel as (N+n) rpm.
Q2 - Explain steering geometry in detail.
• The term ‘steering geometry’ (also known as “front end geometry”) refers to the
angular relationship between suspension and steering parts, front wheels and
the road surface. Because alignment deals with angles and affects steering the
method of describing alignment measurements is called steering geometry.
• There are 5 steering geometry angles :
✓ Camber
✓ Caster
✓ Kingpin Inclination
✓ Toe in & Toe out
A. Camber
• It is the angle of inclination of the front wheel tyre with respect to the vertical
axis view from front of vehicle.
• Camber provided may be positive or negative.
• Camber is also called as ‘wheel rake’.
• Camber angle is positive when this is outward. This happens when wheels are
further apart at top than at bottom.
• On the contrary, camber angle is negative when angle is inward. This happens
when wheels are further apart at bottom than at top.
• The camber should not be more than 2 degree.

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B. Caster :
• The angle between the king pin centre line and the vertical, in the plane of the
wheel is called caster angle.
• Caster is the slant of the steering axis as viewed from the side of the vehicle.
• The steering axis is the imaginary steering pivot line which in some vehicles
runs through the center of the king pin and on other runs through the canters of
the upper and lower ball joint.
• Caster is negative when the top of the steering axis leans to the front of the
vehicle.
• The steering axis intersection point is called leading point and the tyre ground
contact point is called trailing point.
• The positive caster is to provide directional stability. The greater the positive
caster, greater is the stabilizing force. Amount of caster about 30 good result.
C. Kingpin Inclination:
• Most of the steering systems have a kingpin which is attached to steering
knuckle to a support
• In some later design kingpin is replaced by ball and socket joint. In this design,
the Steering

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• knuckle and knuckle support are combined into a single part, This part is called
steering knuckle. No kingpin is used in this case.
• The steering knuckle is supported at the top and bottom by control arm
D. Toe in & Toe Out
• Toe-in is the amount by which the front wheels are set closer together at the
front than at the rear when the vehicle is stationary.
• Toe-out is the amount by which the wheel may be set closer at the rear than
the front when the vehicle is stationary.
• The difference in distance, toe-in or toe-out into a vehicle to counteract the fact
that the tyres tend to change their track when the vehicle is running on the road
• An equal amount of toe-out will not cause anymore tyre wear. But this toe-out
will tend to make the wheel wander and therefore toe-in is usually preferred.
The correct toe-in causes rapid tyre wear, vibration and wheel wobble.
• Adjustment of toe-in or toe-out is provided on all vehicle by track rod attached
to the steering or on the ball joint end of the steering arms on the rack and pinion
steering.

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Q3 - Explain Antilock-Braking system in detail
• Anti-lock Braking System also known as anti-skid braking system (ABS) is an
automobile safety system which prevents the locking of wheels during braking
and avoid uncontrolled skidding.
• The modern abs system allows steering during braking which gives more control
over the vehicle in case of sudden braking.
• The main advantages of using ABS system in vehicle is that it provides better
control over the vehicle and decreases stopping distance on dry and slippery
surfaces
• Since in ABS installed vehicle the chance of skidding is very less and hence it
provides a better steering control during braking.
• Without ABS system, even a professional driver can fail to prevent the skidding
of the vehicle on dry and slippery surfaces during sudden braking.
• But with ABS system, a normal person can easily prevent the skidding of the
vehicle and get better steering control during braking.
Principle of Working
• It works on the principle of threshold braking and cadence braking.
• Cadence braking and threshold braking is a technique in which a driver applies
the brakes and releases it before locking up the wheel and then applies the
brakes and releases it again before locking.
Main Components of ABS System
It has four main components
1. Speed sensors 2. Valves 3. Pump 4. Controller

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Working of Anti-lock Braking System (ABS)
• The controller (ECU-Electronic Control Unit) reads the signal from each of the
speed sensors of the wheel.
• As the brakes are suddenly applied by the driver, this makes the wheel to
decelerate at faster rate and may cause the wheel to Lock.
• As the ECU reads the signal which indicates the rapid decrease in the speed of
the wheel, it sends signal to the valve which makes the valve close and the
pressure to the brake pad reduces and prevents the wheel from locking.
• The wheel again starts to accelerate, again the signal sends to the controller,
this time it opens the valve, increasing the pressure to the brake pad and brakes
are applied, this again reduces the speed of the wheel and tries to make it stop.
• This process of applying brakes and releasing it happens 15 times in a second
when a driver suddenly applies the brake harder.
• Due to this the locking of the wheel is prevented and the skidding of the vehicle
eliminated.
• During braking with ABS system, the driver can steer the vehicle and reduces
the risk of vehicle collision.
Advantages
• It prevents the locking of the wheel and thus eliminates the chance of skidding.
• The skidding of the vehicle is completely removed, which results in excellent
control during braking

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• A better steering control is obtained with the ABS system.
• It reduces the chance of collision by 30 %.
Disadvantages
• A vehicle equipped with ABS (Anti-lock Braking System) is costlier as compared
with a vehicle without ABS.
Q4. Final drive & its types
Types of final drives are.
• Bevel drive.
There are three types of bevel gears namely.
a) Spur bevel gears.
b) Spiral bevel gears.
c) Hypoid gears.
• Worm and Worm wheel.
• Final drive is the last stage of power transfer from propeller shaft to rear
(or front if –automobile is front wheel driven) axles and then to wheels.
• It turns the propeller shaft motion at right angle to drive the rear axle. The
final drive is composed of a bevel gear (or pinion) and crown wheel.
• The level pinion is connected to propeller shaft. The pinion is in mesh with
the crown wheel.
• Crown wheel is part of differential. Final drive provides fixed speed
reduction. Because the crown wheel has more number of teeth and it is

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connected to rear axles and level pinion has less number of teeth.
Schematic diagram of final drive shown below
Q5 - Explain Overdrive
• An overdrive is a mechanism that allows an automobile to cruise at sustained
speed with reduced engine RPM, leading to better fuel economy, lower noise,
and lower wear.
• It is mounted at the rear end of the gearbox.
• The gear ratio provided by an overdrive unit is 30% more than the direct top
gear.
• The unit consists of an epicyclic gear train.
• The planet carrier is connected to the output shaft of the gear box.
• When the sun gear is locked to the output shaft of the gear box, the planet
carrier rotates about the sun gear.
• The ring gear rotates more slowly than planet gear thus giving more ratio than
the direct drive.
• Overdrive is used in some sports cars and luxury cars.

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Q6 - Explain Over-steer and under-steer
❖ Understeer
• It means lack of grip. When this happens, the driver will have little response
from the steering wheel.
• It takes place when the vehicle’s front wheels begin to plow straight despite
turning the steering wheel.
• Front-wheel-drive cars are prone to this phenomenon because they send the
engine power to the wheels that steer the car. So, when the tires start, the driver
does not feel any grip to steer.
• It most commonly happens due to accelerating early while turning in a corner.
You lift the weight distribution that takes the control off of the front tires and
leads to understeer.
• It can also occur when you turn the wheels on your car too fast and too far.
• Applying more suspension or increasing front wing can minimize the understeer.
Tire pressure adjustment also helps sometimes.
❖ Oversteer
• It happens when the front side of a vehicle has more grip than the back side. It
makes the car to spin when driving into a corner.
• Oversteer is the result of the rear end of a car being fishtailed or sliding out.
• Rear-wheel-cars are susceptible to oversteer because here the rear end of the
car has the control power. So, when the rear end loses the grip, it overtakes the
front and oversteer occurs.

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• Oversteer is not something to be concerned over because it happens in
everyday driving. However, it could be dangerous if occurs in snowy, muddy, or
rainy conditions.
• You have to do the opposite to fix this problem. You have to loosen the
suspension or downforce to drop the grip.
Q7 - Explain Reversibility of steering gears.
• Steering gear is said to be reversible if the deflection of steered wheel due to
road surface is transmitted through steering linkages and steering gears to the
steering wheels
• Steering gear is said to be irreversible if the deflection of steered wheel due to
road surface is not transmitted through steering linkages and steering gears to
the steering wheels.
• Some degrees of irreversibility is desired to stop shocks sustained by the road
wheels such system is known as semi reversible system.

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MODULE NO 3
Q1 - Explain the difference between sprung and un-sprung mass.
Sprung mass
• Sprung mass (or sprung weight), in a vehicle with a suspension, such as an
automobile, motorcycle, or a tank, is the portion of the vehicle's total mass that
is supported by the suspension, including in most applications approximately
half of the weight of the suspension itself.
• The sprung mass typically includes the body, frame, the internal components,
passengers, and cargo, but does not include the mass of the components at the
other end of the suspension components (including the wheels, wheel bearings,
brake rotors, calipers, and/or continuous tracks (also called caterpillar tracks), if
any), which are part of the vehicle's unsprung mass.
• The larger the ratio of sprung mass to unsprung mass, the less the body and
vehicle occupants are affected by bumps, dips, and other surface imperfections
such as small bridges. However, a large sprung mass to unsprung mass ratio
can also be deleterious to vehicle control.
Unsprung mass
• In a ground vehicle with a suspension, the unsprung mass (or the unsprung
weight) is the mass of the suspension, wheels or tracks (as applicable), and
other components directly connected to them, rather than supported by the

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suspension (the mass of the body and other components supported by the
suspension is the sprung mass).
• Unsprung mass includes the mass of components such as the wheel axles,
wheel bearings, wheel hubs, tires, and a portion of the weight of driveshafts,
springs, shock absorbers, and suspension links.
• If the vehicle's brakes are mounted outboard (i.e., within the wheel), their mass
(weight) is also considered part of the unsprung mass.
Q2 - Stating the requirements of suspension
All the parts which perform the function of isolating the Automobile from the road
shocks are collectively called a suspension system. Requirements of an automobile
suspension system:
➢ In order to provide comfortable ride to the passengers & avoid additional
stresses in the vehicle frame.
➢ The vehicle should neither bounce nor roll away passengers when cornering
pitch when accelerating, braking or sudden lifting or dropping of the front wheel
with respect to rear wheels. Although some of road irregularities & inequalities
are absorbed by large tyres.
➢ It is necessary to provide a suspension system reducing the shocks to
passengers & for comfortable ride also reduce additional stresses in the
automobile frame & body.
➢ Suspension system acts as a safeguard for the occupants against road shocks
& provide comfort ride.
➢ Suspension system keep the body perfectly in level while travelling over the
uneven road.
Q3 - Explain Wishbone type suspension systems

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• In automobiles, wishbone suspension is an independent suspension design
using two (occasionally parallel) wishbone-shaped arms to locate the wheel.
• Each wishbone or arm has two mounting points to the chassis and one joint at
the knuckle.
• The shock absorber and coil spring mount to the wishbones to control vertical
movement.
• Wishbone designs allow the engineer to carefully control the motion of the
wheel throughout suspension travel, controlling such parameters as camber
angle, caster angle, toe pattern, roll center height, scrub radius, scuff and more.
Q4 - Air suspension and its feature in detail.
• Air suspension is a type of vehicle suspension powered by an electric or
engine-driven air pump or compressor.
• This compressor pumps the air into a flexible bellows, usually made from
textile-reinforced rubber. Unlike hydro pneumatic suspension, which offers
many similar features, air suspension does not use pressurized liquid, but
pressurized air. The air pressure inflates the bellows, and raises the chassis
from the axle.
Components of air suspension
An air suspension has 3 basic componets
a) The air supply
b) the air bags
c) the height control valves
• Air bags are simply a rubber that holds airs.Air bags are also referred to as
spring or bellows

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• The air bags are located between the frame of the vehicle and the vechile axles
• Air bags are rated for weight and pressure capacities
• At the very least, there will be one air bags for each side of each axle in the
vechile.
Q5 - Requirements of wheels and Tyres
Requirement of wheels
• should be light in weight
• It should be possible to remove or mount the wheel easily
• It should be balanced both statically & dynamically
• Wheel material should not not be deteriorate. It must have better resistance
corrosion.
• It should have good load carrying capacity , it must resist bending , tensile,
compressive & torsional stress
• Cushing effect is necessary to absorb shock load
Requirement of tyres
• Good cornering stability
• Direct and immediate response to steering movements
• Guarantee requirement of sustained maximum speed
• Small fluctuations in wheel load
• Good suspension and damping properties (little rolling hardness)
• High smoothness as a result of low radial tyre run-out and imbalances
• Little steering effort required during parking and driving
• Low running noise
• Long-term durability
• High-speed stability

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Q6 - Types of wheels, types of tyres.
❖ Types of tyres.
1. Solid tyre : these are of limited use specially in industrial application
2. Pneumatic or air filled tyre : in this type an air is acts as a cushioning medium
confined in an inner tube. These are classified below
a. On basis of pressure and volume
i. High pressure tyre (pressure up to 4.2 kg/cm²)
ii. Conventional tyre ( pressure range 1.68 to 2.8 kg/cm²)
iii. Super cusion tyre (pressure range 1.4 to 1.68 kg/cm²)
b. On basis of construction
i. Tube tyre
ii. Tubeless tyre
c. Carcass types tyre
i. Cross ply tyre
ii. Radial ply tyre
iii. Belted bias tyre

P a g e | 30

P a g e | 31
• Combination of both the radial and cross ply type are known as Belted -
bias tyre
• Basic construction is the bias ply over which run a number of breaker
belts.
• The belts improve the characteristic of the bias ply to a large extent.
Q7 - Shock absorbers and its types
• A shock absorber or damper is a mechanical or hydraulic device designed to
absorb and damp shock impulses.
• It does this by converting the kinetic energy of the shock into another form of
energy (typically heat) which is then dissipated. Most shock absorbers are a
form of dashpot (a damper which resists motion via viscous friction)
Types:
1. Twin-tube :
(a) Basic twin-tube:
• Also known as a "two-tube" shock absorber, this device consists of two
nested cylindrical tubes, an inner tube that is called the "working tube"
or the "pressure tube", and an outer tube called the "reserve tube".
• At the bottom of the device on the inside is a compression valve or
base valve.
• When the piston is forced up or down by bumps in the road, hydraulic
fluid moves between different chambers via small holes or "orifices" in
the piston and via the valve, converting the "shock" energy into heat
which must then be dissipated.
(b)Twin-tube gas charged:

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• Variously known as a "gas cell two-tube" or similarly-named design,
this variation represented a significant advancement over the basic
twin-tube form.
• Its overall structure is very similar to the twin-tube, but a low-pressure
charge of nitrogen gas is added to the reserve tube.
• The result of this alteration is a dramatic reduction in "foaming" or
"aeration", the undesirable outcome of a twin-tube overheating and
failing which presents as foaming hydraulic fluid dripping out of the
assembly.
• Twin-tube gas charged shock absorbers represent the vast majority of
original modern vehicle suspensions installations.
(c) Position sensitive damping:
• Often abbreviated simply as "PSD", this design is another evolution of
the twin-tube shock. In a PSD shock absorber, which still consists of
two nested tubes and still contains nitrogen gas, a set of grooves has
been added to the pressure tube.
• These grooves allow the piston to move relatively freely in the middle
range of travel (i.e., the most common street or highway use, called by
engineers the "comfort zone") and to move with significantly less
freedom in response to shifts to more irregular surfaces when upward
and downward movement of the piston starts to occur with greater
intensity (i.e., on bumpy sections of roads— the stiffening gives the
driver greater control of movement over the vehicle so its range on
either side of the comfort zone is called the "control zone").
• This advance allowed car designers to make a shock absorber tailored
to specific makes and models of vehicles and to take into account a
given vehicle's size and weight, its maneuverability, its horsepower,
etc. in creating a correspondingly effective shock.
(d)Acceleration sensitive damping:
• The next phase in shock absorber evolution was the development of a
shock absorber that could sense and respond to not just situational
changes from "bumpy" to "smooth" but to individual bumps in the road
in a near instantaneous reaction.
• This was achieved through a change in the design of the compression
valve, and has been termed "acceleration sensitive damping" or "ASD".
• Not only does this result in a complete disappearance of the "comfort
vs. control" tradeoff, it also reduced pitch during vehicle braking and
roll during turns.
• However, ASD shocks are usually only available as aftermarket
changes to a vehicle and are only available from a limited number of
manufacturers.
(e) Coilover :

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• Coilover shock absorbers are usually a kind of twin-tube gas charged
shock absorber inside the helical road spring.
• They are common on motorcycle and scooter rear suspensions, and
widely used on front and rear suspensions in cars.
2. Mono tube:
• The principal design alternative to the twin-tube form has been the mono-
tube shock absorber which was considered a revolutionary advancement
when it appeared in the 1950s.
• As its name implies, the mono-tube shock, which is also a gas-pressurized
shock and also comes in a coil over format, consists of only one tube, the
pressure tube, though it has two pistons.
• These pistons are called the working piston and the dividing or floating
piston, and they move in relative synchrony inside the pressure tube in
response to changes in road smoothness.
• The two pistons also completely separate the shock's fluid and gas
components.
• The mono-tube shock absorber is consistently a much longer overall
design than the twin-tubes, making it difficult to mount in passenger cars
designed for twin-tube shocks.
• However, unlike the twin-tubes, the mono-tube shock can be mounted
either way— it does not have any directionality.
• It also does not have a compression valve, whose role has been taken
up by the dividing piston, and although it contains nitrogen gas, the gas in
a mono-tube shock is under high pressure (260-360 p.s.i. or so) which
can actually help it to support some of the vehicle's weight, something
which no other shock absorber is designed to do.
3. Spool valve:
• Spool valve dampers are characterized by the use of hollow cylindrical
sleeves with machined-in oil passages as opposed to traditional
conventional flexible discs or shims.
• Spool valving can be applied with monotube, twin-tube, and/or position-
sensitive packaging, and is compatible with electronic control.
• Primary among benefits cited in Multimatic’s 2010 patent filing is the
elimination of performance ambiguity associated with flexible shims,
resulting in mathematically predictable, repeatable, and robust pressure-
flow characteristics.

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Q8 - Explain telescopic types of shock absorber
• The most common type of shock absorber is Telescopic type hydraulic shock
absorber or sometimes called telescopic shock absorber.
• The very common shock absorber is telescopic type. It is an hydraulic shock
absorber. The name telescopic is derived because the shape of this shock
absorber is completely matches with the ancient telescope.
• There are two types of this shock absorber. First one is twin tube telescopic type
and other one is mono tube telescopic
❖ Twin Tube Telescopic Shock Absorber
• As shown in the diagram, this type of shock absorber have twin tubes one inner
tube shown by symbol A and other outer tube shown by symbol B. There are
two 2 way valves one is shown by V1 and other is by V2.
• Valve V1 is connected with a piston rod and free to move vertically inside the
tube A. The Valve V2 is fixed at one end of the tube A. Oil is filled inside the
tube A below the valve V1. At the initial condition piston or we can say valve V1
is at middle of the cylinder.
• The annular space between tube A and B is half filled with the oil. There are two
eyes of the shock absorber which is shown by E1 and E2. E1 is connected to
the chassis frame and E2 is connected to the axle.
• When the vehicle come across a bump, the eye E2 tends to move upward.
Therefor to absorb the bump valve V1 start to move downward which compress
the fluid trapped between the valve V1 and V2.
• This will pressuring the valve V1 and V2 thus the oil start to move from upper
side of the valve assembly through valve V1 and also some oil move in the
annular space between tube A and B through valve V2.

P a g e | 35
• This process converts all the vibration energy into fluid friction and absorbs
shocks.
• When the vehicle rebound, the valve V1 start to move upward which again
pressuring the valve V1 hence it open again and the oil start to flow below valve
V1.
• During its upward movement it also sucks some oil from the annular space
between tube A and B thus the vehicle get its initial condition.
❖ Mono Tube Telescopic Shock Absorber:
• This is another type of shock absorber used in automobile industries. As the
name implies this type of telescopic shock absorber has one tube which two
chambers.
• There are two piston one is shown by P1 and other is by P2. Piston P1 is
attached with a piston rod. Piston P2 is floating piston which can move upward
and downward according the pressure its upward and downward side.
• This shock absorber have two chamber A and B separated by the floating piston
P2. The upper chamber A is filled with the oil and lower chamber is filled with
high pressurize nitrogen gas.
• There are two eyes of the shock absorber which is shown by E1 and E2. E1 is
connected to the chassis frame and E2 is connected to the axle.
• When the vehicle come across a bump, the eye E2 tends to move upward.
Therefor to absorb the bump piston P1 start to move downward which compress
the oil situated between chamber A.
• This will rise the oil pressure thus the floating piston start to move downward
and compress the gas till the oil pressure and gas pressure equalize.
• This process uses the vibration energy of bump to compress the gas thus
absorb vibration.
• When the vehicle again come across the level road, the piston P1 start to move
upward which reduce oil pressure situated upper side of floating piston.

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• Due to this pressure difference the floating piston start to move upward thus the
vehicle gets its initial position.
❖ Advantages of telescopic shock absorber:
• This shock absorber is available in various size according to the requirement.
• Noise free operation
• Less maintenance required.
• Low manufacturing cost.
• High operating spee

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MODULE 04
Q1. Classify battery and explain Lead-Acid battery with neat diagram.
Lead acid battery:
Definition: The battery which uses sponge lead and lead peroxide for the conversion
of the chemical energy into electrical power, such type of battery is called a lead acid
battery. The lead acid battery is most commonly used in the power stations and
substations because it has higher cell voltage and lower cost.
Construction of Lead Acid Battery:
• The various parts of the lead acid battery are shown below. The container and
the plates are the main part of the lead acid battery.
• The container stores chemical energy which is converted into electrical energy
by the help of the plates.
• Container – The container of the lead acid battery is made of glass, lead lined
wood, ebonite, the hard rubber of bituminous compound, ceramic materials or
moulded plastics and are seated at the top to avoid the discharge of electrolyte.
At the bottom of the container, there are four ribs, on two of them rest the
positive plate and the others support the negative plates.The prism serves as
the support for the plates and at the same time protect them from a short-circuit.

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• Plate – The plate of the lead-acid cell is of diverse design and they all consist
some form of a grid which is made up of lead and the active material. The grid
is essential for conducting the electric current and for distributing the current
equally on the active material. If the current is not uniformly distributed, then the
active material will loosen and fall out.
• Active Material – The material in a cell which takes active participation in a
chemical reaction (absorption or evolution of electrical energy) during charging
or discharging is called the active material of the cell. The active elements of
the lead acid are
• Lead peroxide (PbO2) – It forms the positive active material. The PbO2 are dark
chocolate broom in colour.
• Sponge lead – Its form the negative active material. It is grey in colour.
• Dilute Sulfuric Acid (H2SO4) – It is used as an electrolyte. It contains 31% of
sulfuric acid.
• Separators – The separators are thin sheets of non-conducting material made
up of chemically treated leadwood, porous rubbers, or mats of glass fibre and
are placed between the positive and negative to insulate them from each other.
Separators are grooved vertically on one side and are smooth on the other side.
• Battery Terminals – A battery has two terminals the positive and the negative.
The positive terminal with a diameter of 17.5 mm at the top is slightly larger than
the negative terminal which is 16 mm in diameter.
Working Principle of Lead Acid Battery:

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• The composition of Lead-Acid battery is a combination of Pb (negative) and
PbO2 (positive) as electrodes, with H2SO4 as electrolyte in charged form and
PbSO4 and water in discharged form.
• The main active materials of a lead-acid battery are:
➢ Lead peroxide (PbO2) - The positive plate is made of lead peroxide.
➢ Sponge Lead (Pb) - The negative plate is made of pure lead in soft sponge
condition.
➢ Dilute Sulphuric Acid (H2SO4) - Dilute sulphuric acid used for lead acid
battery has ratio of water: acid =3:1.
• The lead acid storage battery is formed by dipping lead peroxide plate and
sponge lead plate in dilute sulphuric acid. A load is connected externally
between these plates.
• In diluted sulfuric acid the molecules of the acid split into positive hydrogen ions
(H+) and negative sulfate ions (SO2−4). The hydrogen ions when reach at PbO2
plate, they receive electrons from it and become hydrogen atom which again
attack PbO2 and form PbO and H2O (water).
• PbO2+2H−→PbO+H2O This PbO reacts with H2SO4 and forms PbSO4 and
H2O (water).PbO+H2SO4−→PbSO4+H2O
• SO2−4 ions are moving freely in the solution so some of them will reach to pure
Pb plate where they give their extra electrons and become radical SO4. As the
radical SO4 cannot exist alone it will attack Pb and will form PbSO4. As H+ ions
take electrons from PbO2 plate and SO2−4 ions give electrons to
• Pb plate, there would be an inequality of electrons between these two plates.
Hence there would be a flow of current through the external load between these
plates for balancing this inequality of electrons. This process is called
discharging of lead acid battery.
• Then the load is disconnected and we connect PbSO4 covered PbO2 plate with
positive terminal of an external DC source and PbO2covered Pb plate with
negative terminal of that DC source. During discharging specific gravity of
sulfuric acid solution falls due to formation of water during reaction at PbO2
plate. But there is still sulfuric acid existing in the solution. This sulfuric acid also
remains as H+ and SO) 42− ions in the solution.
• Hydrogen ions (cation) being positively charged, move to the electrode
(cathode) connected with negative terminal of the DC source. Here each H+ ion
takes one electron from that and becomes hydrogen atom. These hydrogen
atoms then attack PbSO4 and form lead and sulfuric acid.
PbSO4+2H−→Pb+H2SO4

P a g e | 40
• SO2−4 ions (anions) move towards the electrode (anode) connected with
positive terminal of DC source where they give up their extra electrons and
become radical SO4. This radical SO4 cannot exist alone hence reacts with
PbSO4 of anode and forms lead peroxide (PbO2) and sulfuric acid (H2SO4).
PbSO4+2H2+SO4−→PbO2+2H2SO4
• Hence by charging the lead acid storage battery cell, Lead sulfate of anode gets
converted into lead peroxide. Lead sulfate of cathode is converted to pure lead.
Terminal potential of the cell increases. Specific gravity of sulfuric acid
increases.
❖ Ampere-Hour Rating of Lead-Acid Battery:
• Typical ampere-hour ratings for 12 V lead-acid automobile batteries range from
100 Ah to 300 Ah.
• This is usually specified for an 8 h discharge time, and it defines the amount of
energy that can be drawn from the battery until the voltage drops to about 1.7 V
per cell. For a 240 Ah rating, the battery could be expected to supply 30 A for
an 8h period (see Figure ).
• With greater load currents, the discharge time is obviously shorter. However,
the ampere-hour rating is also likely to be reduced for a shorter discharge time
because the battery is less efficient when supplying larger currents.
• Another method of rating a lead-acid battery is to define what its terminal voltage
will be after about 5 s of supplying perhaps 250 A.
• This corresponds to the kind of load that a battery experiences in starting an
automobile. It is important to avoid battery overloads that may demand
excessive currents. Drawing a larger current than the battery is designed to
supply may cause severe damage.

P a g e | 41
• The rating of a battery is typically stated for temperatures around 25°C, and this
must be revised for operation at lower temperatures.
• Because the chemical reactions occur more slowly at reduced temperatures,
the available output current and voltage are less than at 25°C. Around -18°C a
fully charged battery may be capable of delivering only 60% of its normal
ampere-hour rating.
• As the cell is discharged and the electrolyte becomes weaker, freezing of the
electrolyte becomes more likely. A fully charged cell is less susceptible to
freezing, but even a fully charged cell may fail when its temperature falls to
about -21°C.
Q2. Short note on alkaline battery.
Alkaline battery :
• The first Alkaline battery was brought into market by Eveready Battery, Toronto.
It was developed by Lew Urry who was attached to this company as a chemical
engineer.
• Lew Urry developed the small alkaline battery in 1949. The inventor was working
for the Eveready Battery Co. at their research laboratory in Parma, Ohio.
Alkaline battery lasts five to eight times as long as zinc-carbon cells, their
predecessors.
• These batteries are introduced to overcome the weight and mechanical
weakness of the lead plates.
• The main working principle of the alkaline battery is based on the reaction
between zinc (Zn) and manganese dioxide (MnO2).

P a g e | 42
• An alkaline battery is so named because the electrolyte used in it is potassium
hydroxide, a purely alkaline substance.
Construction of alkaline battery:
• The body of the battery is made of a hollow steel drum. This drum contains all
materials of the battery, and it also serves as the cathode of the battery.
• The positive terminal of the battery is projected from the top of this drum. Fine-
grained manganese dioxide (MnO2) powder mixed with coal dust is molted to
the inner peripheral surface of the empty cylindrical drum.
• This molded mixture serves as a cathode mixture of the alkaline battery. The
inner surface of the thick layer of cathode mixture is covered with a paper
separator.
• The central space, inside this paper separator, is filled with zinc powder with
potassium hydroxide electrolyte. The zinc serves as an anode, and its powder
form increases the contact surface.
• The paper separator soaked with potassium hydroxide holds the electrolyte in
between cathode (MnO2) and anode(Zn). A metallic pin (preferably made of
brass) is inserted along the central axis of the alkaline battery to collect the
negative charge.
• This pin is called negative collector pin. This pin is in touch with a metallic end
sealed cap. There is a plastic cover just inside the Metallic end sealed cap, and
this plastic cover electrically separates positive steel drum and negative end cap
of alkaline battery.In an alkaline battery cell, the powder zinc serves as an
anode; manganese dioxide serves as cathode and potassium hydroxide serves
as an electrolyte.
Advantages of Alkaline Battery

P a g e | 43
• This has high energy density.
• This battery performs equally well in both continuous and intermittent
applications.
• This performs equally well in low and as well as high rate of discharge.
• This also performs equally well at ambient temperature as well as at low
temperature.
• Alkaline battery has also low internal resistance.
• It has enough longer self life.
• Leakage is low in this battery.
• It has better dimensional stability.
Disadvantage of Alkaline Battery
Practically this type of battery does not have any disadvantage except its high
cost.
Q3. Short note on ZEBRA BATTERY.
ZEBRA battery :
• A lower-temperature variant of NaS batteries was the development of the
ZEBRA (originally, "Zeolite Battery Research Africa"; later, the "Zero Emissions
Batteries Research Activity") battery in 1985, originally developed for electric
vehicle applications.
• The battery uses NaAlCl4 with Na+-beta-alumina ceramic electrolyte.

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• The Na-NiCl2 battery operates at 245 °C (473 °F) and uses molten sodium tetra-
chloro-aluminate (NaAlCl4), which has a melting point of 157 °C (315 °F), as
the electrolyte.
• The negative electrode is molten sodium. The positive electrode is nickel in the
discharged state and nickel chloride in the charged state.
• Because nickel and nickel chloride are nearly insoluble in neutral and basic
melts, contact is allowed, providing little resistance to charge transfer.
• Since both NaAlCl4 and Na are liquid at the operating temperature, a sodium-
conducting β-alumina ceramic is used to separate the liquid sodium from the
molten NaAlCl4.
• The primary elements used in the manufacture of these batteries have much
higher worldwide reserves and annual production than lithium.
• It was invented in 1985 by the Zeolite Battery Research Africa Project (ZEBRA)
group at the Council for Scientific and Industrial Research (CSIR) in Pretoria,
South Africa.
• It can be assembled in the discharged state, using NaCl, Al, nickel and iron
powder.
• The positive electrode is composed mostly of materials in the solid state, which
reduces the likelihood of corrosion, improving safety.
• Its specific energy is 90 Wh/kg; specific power is 150 W/kg.
• The β-alumina solid ceramic is unreactive to sodium metal and sodium
aluminum chloride.
• Lifetimes of over 1,500 cycles and five years have been demonstrated with full-
sized batteries, and over 3,000 cycles and eight years with 10- and 20-cell
modules.
• For comparison LiFePO4 lithium iron phosphate batteries store 90–110 Wh/kg,
and the more common LiCoO2 lithium-ion batteries store 150–200 Wh/kg. A
nano lithium-titanate battery stores 72 Wh/kg and can provide power of 760
W/kg.
• The ZEBRA's liquid electrolyte freezes at 157 °C (315 °F), and the normal
operating temperature range is 270–350 °C (520–660 °F).
• Adding iron to the cell increases its power response.
• ZEBRA batteries are currently manufactured by FIAMM Sonick and are used in
the Modec Electric Van, the IVECO daily 3.5 ton delivery vehicle, the prototype
Smart ED, and the Th!nk City.
• In 2011 the US Postal Service began testing all-electric delivery vans, one
powered by a ZEBRA battery.
• In 2010 General Electric announced a Na-NiCl2 battery that it called a sodium–
metal halide battery, with a 20-year lifetime.

P a g e | 45
• Its cathode structure consists of a conductive nickel network, molten salt
electrolyte, metal current collector, carbon felt electrolyte reservoir and the
active sodium–metal halide salts.
• In 2015, the company abandoned the project. Sumitomo developed a battery
using a salt that is molten at 61 °C (142 °F), far lower than sodium based
batteries, and operational at 90 °C (194 °F).
• It offers energy densities as high as 290 Wh/L and 224 Wh/kg and
charge/discharge rates of 1C with a lifetime of 100 - 1000 charge cycles.
• The battery employs only nonflammable materials and neither ignites on contact
with air nor risks thermal runaway.
• When not in use, Na-NiCl2 batteries are typically kept molten and ready for use
because if allowed to solidify they typically take 12 hours to reheat and charge.
• This reheating time varies depending on the battery-pack temperature, and
power available for reheating.
• After shutdown a fully charged battery pack loses enough energy to cool and
solidify in 3–4 days
Advantage of zebra battery :
• High energy density (5 times higher than Lead acid)
• Large cells (up to 500Ah) possible
• Cycle life better than 1000 cycles
• Tolerant of short circuits
• Safer than Sodium Sulfur cells
• Typical cell failure is short circuit which does not cause complete failure of
the battery.
• Low cost materials
Applications
• Traction applications
• EVs
• HEV
• Railway
Q4. Explain various battery ratings.
• Battery rating : Rating of a battery is determined by the current it can produce
and the time for which it can sustain this current. Batteries are rated in many
ways the most important of which are:

P a g e | 46
• Ampere Hour capacity: It represents the lasting power of a battery on small
load. It represents the rate of current a battery can deliver continuously for 20
hours after which the cell voltage should not drop below 1.75V at 80 °F.
• Twenty minute rate: It represents the rate of current a battery can deliver
continuously for 20 minutes the cell voltage not dropping below 1.5V at 80 °F.
• Reserve capacity: RC is a battery's ability to sustain a minimum stated
electrical load; it is defined as the time (in minutes) that a lead-acid battery at
80 °F will continuously deliver 25 amperes before its voltage drops below 10.5
volts.
• Cold cranking amps: CCA is a measure of a battery's ability to start a car in
cold weather, when thickened engine oil and slowed chemical reactions make
starting hardest. CCAs denote how much current the battery can deliver to the
starter at 0° F. It represents the current in amperes which the battery can supply
continuously for 30 sec or 1minute without cell voltage dropping below 1.4V
Q5. Explain bendix drive in detail.
• A Bendix drive is a type of engagement mechanism used in a starter motors of
internal combustion engines.
• Inertia type drive works on the principle of inertia of unbalanced weight
• In this type pinion is mounted on threaded sleeve
• Engage : When ignition switch pressed the stater motor begins turning the
inertia of the drive pinion assembly causes it to wound the spring forcing the
length of the spring to change and engage with ring gear.
• Disengage : When the engine starts back drive from the ring gear causes the
drive pinion to exceed the rotation speed of the starter at which point the drive
pinion is forced back and out of the mesh with the ring gear

P a g e | 47
MODULE 05
Q1. State the importance of vehicle body design explain three layouts each of
Passenger car and bus.
❖ Importance of body design
• Vehicle body is a superstructure.
• Body is either integral with the under frame or bolted to the frame.
• The body & chassis make complete vehicle.
• A body consist of a doors, windows, engine covers, roof, luggage, cover etc.
• Different type of body's is attached to chassis according to application.
• The important design considerations are as follows:
➢ Customer appeal of style
➢ Reduction in body weight to improve capacity & fuel economy.
➢ Aerodynamic characteristics which determine the fuel consumpton,
speed. &_stability in cross wind. The positive pressure at front
should be decreased & deflated smoothly for the prevention of eddies
creations.
Layouts of passenger bus:-
• Chasis is a main structure, upon which all the major component of an
automobile which are..necessary to proper the vehicle are assembled.
• Chasis comprises of everything of a vehicle except the body, cabin &
equipment. The automobile chassis consist of following components:
• Frame:- It is a skeleton to hold the major unit together There are of two types:
➢ The conventional pressed steel frame to which all mechanical unit are
attached.
➢ Integral or frameless construction in which body construction perform
combine function of body & frame. So, it decreases the weight & save fuel
consumption also reduces manufacturing cost but increases repair cost if
damage occur during accident
• Engine – It provides motive power to perform the various function of vehicle.
• Transmission System - It consists of clutch, gearbox,universal.joint, propellers
shaft, differential, rear axle, wheel.

P a g e | 48
• Suspension System - This system isolates the vehicle body from the road shock
which are in the form of rolling, bouncing & pitching. It provides comfort to
passenger & reduce the steps in frame.
• Controls- Vehice includes steering system, braking system & engine control.
• Electrical control: This system consists of supply systems Battery & dynamo
starting relay, ignition system (Battery or magneto-ignition system), other
miscellaneous system like driving light signalling, reverse,light, panel light, wiper
,etc.
• Radiater: It is advice used to recool the hot engine cooling water for recirculation
purpose. The radiator is connected to engine by base pibe to allow the cooled
water circulation.
Layout of passenger car:
• The layout of a car is often defined by the location of the engine and
drive wheels. Layouts can roughly be divided into three categories:
front-wheel drive, rear-wheel drive and four-wheel drive.
• Many different combinations of engine location and driven wheels are
found in practice, and the location of each is dependent on the
application for which the car will be used.
Front-wheel-drive layouts
• Front engine, front-wheel drive : The front-engine, front-wheel-drive layout
(abbreviated as FF layout) places both the internal combustion engine and
driven wheels at the front of the vehicle. This is the most common layout for
cars since the late 20th century.
• Mid-engine, front-wheel drive : Some early front-wheel drive cars from the
1930s had the engine located in the middle of the car.
• Rear-engine, front-wheel-drive: A rear-engine, front-wheel-drive layout is one
in which the engine is between or behind the rear wheels, and drives the front
wheels via a driveshaft, the complete reverse of a conventional front-engine,
rear-wheel-drive vehicle layout. This layout has only been used on prototype
and concept cars.

P a g e | 49
Rear-wheel drive layouts
• Front-engine, rear-wheel drive : The front-engine, rear-wheel drive layout
(abbreviated as FR layout) is one where the engine is located at the front of the
vehicle and driven wheels are located at the rear. This was the traditional
automobile layout for most of the 20th century, and remains the most common
layout for rear-wheel drive cars.
• Mid-engine, rear-wheel drive : The mid-engine, rear-wheel drive layout
(abbreviated as MR layout) is one where the rear wheels are driven by an
engine placed just in front of them, behind the passenger compartment. In
contrast to the rear-engined RR layout, the center of mass of the engine is in
front of the rear axle. This layout is typically chosen for its low moment of inertia
and relatively favorable weight distribution.
• Rear-engine, rear-wheel drive : The rear-engine, rear-wheel drive layout
(abbreviated as RR layout) places both the engine and drive wheels at the rear
of the vehicle. In contrast to the MR layout, the center of mass of the engine is
between the rear axle and the rear bumper. Although very common in transit
buses and coaches due to the elimination of the drive shaft with low-floor bus,
this layout has become increasingly rare in passenger cars. The Porsche 911
is notable for its continuous use of the RR layout since 1963.

P a g e | 50
Four-wheel drive layouts
• Front-engine, four-wheel drive : The front-engine, four-wheel drive layout
(abbreviated as F4 layout) places the engine at the front of the vehicle and
drives all four roadwheels. This layout is typically chosen for better control on
many surfaces, and is an important part of rally racing as well as off-road driving.
Most four-wheel-drive layouts are front-engined and are derivatives of earlier
front-engine, rear-wheel-drive designs.
• Mid-engine, four-wheel drive : The mid-engine, four-wheel drive layout
(abbreviated as M4 layout) places the engine in the middle of the vehicle,
between both axles and drives all four road wheels. Although the term "mid-
engine" can mean the engine is placed anywhere in the car such that the centre
of gravity of the engine lies between the front and rear axles, it is usually used
for sports cars and racing cars where the engine is behind the passenger
compartment. The motive output is then sent down a shaft to a differential in the
centre of the car, which in the case of an M4 layout, distributes power to both
front and rear axles.
• Rear-engine, four-wheel drive: The rear-engine, four-wheel drive layout
(abbreviated as R4) places the engine at the rear of the vehicle, and drives all
four wheels. This layout is typically chosen to improve the traction or the
handling of existing vehicle designs using the rear-engine, rear-wheel-drive
layout (RR). For example, the Porsche 911 added all-wheel drive to the existing
line-up of rear-wheel drive models in 1989.
Q2. Chassis types and structure types: Open, Semi integral and integral bus
structure
Following are the four main types of car chassis.

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Ladder Frame Chassis. Ladder chassis.
Backbone Chassis. backbone chassis.
Monocoque Chassis. Monocoque.

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Tubular chassis. Tubular Chassis.
➢ TYPES OF FRAMES:
There are three types of frames
• Conventional frame
• Integral frame

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• Semi-integral frame
Open type:
• In open or non-load carrying type, loads on vehicle are transferred to
suspension system entirely by separate chassis.
• The body work is either made of very flexible material or made stiff. The body is
isolated from the chassis deflection rubber mountings.
• The vehicle loads get concentrated round the mounting and hence result in early
failures. Hence this type of construction has become obsolete in case of cars.
• Application: In trucks, the wooden load carrying bodies are rigidly attached to
chassis frame and stiff cabs are mounted on flexible cabin mounts.
Semi integral type:
• In the semi integral type, the body mounts are made of stiff material.
• The body structure has now become semi integral.
• This prevents squeaking due to the relative displacement between the body and
the chassis.
• Therefore, some of the load transferred to the body structure.
• The semi integral type permits case of styling changes and eliminate road noise
when proper insulation are used.
Integral type:
• In the integral or fully integral body shell, the longitudinal and cross members of
the chassis were incorporated into the framework of the load carrying body.
• With this arrangement, part of the load previously carried by chassis, is diffused
through the body structure.
• This aspect eliminates heavy chassis members that ought to carry the full
bending load.

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• In the integral construction, the body must be provided with extensions at the
front and reinforcements at the rear.
• The latter is required to support the suspension members and bumpers.
• The body must also be reinforced at the other points.
• In spite of all these, the resulting unitary body is found to be lighter.
• Application: Integral body construction is widely used in passenger cars and
to a limited extent in bus design.
Q3. Short note on Aerodynamic drag.
• Automotive aerodynamics is the study of the aerodynamics of road vehicles.
• Its main goals are reducing drag and wind noise, minimizing noise emission,
and preventing undesired lift forces and other causes of aerodynamic instability
at high speeds.
• Air is also considered a fluid in this case. For some classes of racing vehicles,
it may also be important to produce down-force to improve traction and thus
cornering abilities.
• Vehicles with an aerodynamic shape use less fuel.
• Air flows easily over them and less energy is needed to move them forward. At
95 Km/h 60-70% of a vehicle’s energy is used to move it through the air,
compared with only 40% at 50 Km/h.
• Installing a sloping front roof on a lorry could save you as much as 7% of your
fuel costs. Even small changes to design and shape will make a difference.

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• Aerodynamic drag is also called as air resistance.
• Air drag force acts in the direction of vehicle motion.
• The total aerodynamic drag of a vehicle include many factors such as profile
drag (57%), induced drag (8%), skin friction (10%), interference drag (15%) and
cooling and ventilation drag (10%).
• Stream line of air flow around the vehicle should be continuous and separation
of the boundary layer with its attendant vertices should be avoided.
• Skin drag coefficient should be decrease by smooth and well-polished of body
surface.
• The accessories such as mirror, door handle aerials and badges which project
outward from normal surface of body produce interference drag and projection
below the vehicle such as axle, propeller shaft, tow bar also contribute
interference drag hence such projection should be avoided.
Aerodynamic lift:
• It is the vertical component of the resultant force caused by the pressure
distribution on the vehicle body.
• The aerodynamic lift and pitching moment are undesirable effects.
• The aerodynamic lift tends to reduce the pressure between the tyre and the
ground.
• This causes the loss of steering on the front axle and loss of traction on the rear
axle.
• Pitching causes rear wheel lift off the ground and reduces available traction. It
is the rocking chair or rotating action about the transverse axis through the
vehicle parallel to ground.
• Due to pitching, the front suspension moves out of phase with the rear resulting
in rocking effect in a vehicle.
Side force:
• The imbalance of the wheel due to centrifugal force acts on the vehicle during
turning which produces a side thrust.
• To sustain that force, the plane of the wheel makes some angle with the
direction of motion of the vehicle.
• This is achieved by the direction of tyre which is flexible.
Yawing movement (Bouncing):
• It is vertical movement of the complete body .When complete body of vehicle
goes up and down which is known as bounce or bouncing.

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• Depending upon the movement of front end or rear end the bounce is known as
front end bounce or rear end bounce.
Rolling movement:
• It is the movement of a vehicle about its longitudinal axis produced due to
centrifugal force act during cornering.
• The retarding and cornering forces are applied at road levels but the centre of
gravity of a vehicle is at a certain height.
• During cornering, a turning couple is produced about the longitudinal axis of the
vehicle owing to centrifugal force acting at centre of gravity and forces acting at
the point of contact of road and tyre patch.
• his results in a motion known as rolling.
• A combination of rolling and pitching is called diagonal pitch.
Remedies: In order to control all the above suspension movements; anti roller bar,
stabilizer, pitch and roll control bars, hydraulic systems, mechanical levelling devices
etc. are provided to vehicles.

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MODULE 6
Q1. Short note on Adaptive Cruise Control (ACC)
Adaptive Cruise Control is the next big thing in terms of automated speed
management in new cars. It is an intelligent form of cruise control that slows down
and speeds up automatically to keep pace with the car in front of you.
WORKING
• The driver sets a maximum speed similar to what one would do with normal
cruise control.
• A radar sensor located in the front end of the car locates traffic ahead of it and
locks on to the car ahead.
• This sensor then controls the speed of your car so that it always stays 2-3
seconds behind the car in front.
• Using the input from the radar sensors, the computer unit measures the distance
of the car ahead and calculates the speed relative to it.
• If there are multiple vehicles in the sensor’s field of coverage at the same time,
it automatically selects which of the vehicles the system should track.
• For instance, if you’re approaching a slower vehicle ahead or if another vehicle
cuts in front of you, the adaptive cruise control slows down the car by initiating
corrective controls in the engine management and, if necessary, in the braking
system as well.
• ACC is very conscientious when it comes to safety. If you’re driving too close
to the car in front, it will warn you in two stages.
• First, it will alert you with visual and acoustic signals, and then with a short
braking jolt.
• If necessary, the system will bring your car to a complete stop. Some units
employ a laser, while others use an optical system based on stereoscopic
cameras.
• Regardless of the technology, ACC works day or night, but its abilities can be
hampered by extreme conditions, such as heavy rain, fog, or snow

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Q2. Short note on Electronic Stability Program (ESP),
Electronic Stability Program (ESP)
• Imagine you are driving a car at high-speed and suddenly come across an
obstacle. In such a scenario, you will be forced to take a sharp turn or apply
brakes to avoid a possible collision. While doing so, you might lose control and
skid off the road.
• Thus, it may lead to an untoward incident such as an accident. Also, the car you
are driving may tip over. So, to avoid this situation, the manufacturers employ
Electronic Stability Program or Electronic Stability Control system. It is one of
the active safety systems in a modern car.
• The term ESP stands for Electronic Stability Program while the ESC for
Electronic Stability Control. It is an intelligent safety system which can predict
driving intentions.
• Firstly, the ESP helps the driver to maintain the wheel trajectory. It does so by
applying brakes to the individual wheels. Secondly, it can also adjust the engine
performance in critical maneuvers. However, the ultimate purpose of the ESP
is to enhance vehicle stability. Thus, ESP improves stability by avoiding
skidding.
❖ Components of the Electronic Stability Program or Electronic Stability Control:
➢ Hydraulic Unit
➢ Wheel speed sensors
➢ Steering angle sensor
➢ Yaw rate and lateral acceleration sensor
➢ Engine Control Unit]
WORKING
• The wheel speed sensors detect the speed of each wheel. Furthermore, they
send this data to ECU continuously.
• The steering angle sensor determines the position of the steering wheel by
measuring the actual steering angle.
• Additionally, the Yaw rate and lateral acceleration sensors determine the exact
location of the vehicle with reference to the driver's input.
• Afterward, the ECU processes this input data. However, if the sensor data varies
suddenly, the ESP detects that the vehicle is facing a difficult driving condition.

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• Thus, the system can detect that if there is an obstacle in the path or a very
sharp turn.
• In such cases, the system applies the desired braking force only on the wheels
in need. And thus, it restores the driver control over the vehicle.
• This system has more advantage compared to the ABS and TCS systems.
• This is because it can actually predict the driving behavior of the vehicle.
• When the Electronic Stability Program comes into action, it gives an indication
in the form of a glowing indicator in the instrument cluster.
• In most of the cases, the driver does not feel any difference in the vehicle except
the enhanced control when the ESP starts working.
Q3. Short note on Electronic Brake Distribution (EBD)
Electronic brake force distribution (EBD )
• Electronic brake force distribution (EBD or EBFD) or electronic brake force
limitation (EBL) is an automobile brake technology that automatically varies the
amount of force applied to each of a vehicle's wheels, based on road conditions,
speed, loading, etc.
• Always coupled with anti-lock braking systems (ABS), EBD can apply more or
less braking pressure to each wheel in order to maximize stopping power whilst
maintaining vehicular control.
• Typically, the front end carries the most weight and EBD distributes less
braking pressure to the rear brakes so the rear brakes do not lock up and cause
a skid. In some systems, EBD distributes more braking pressure at the rear
brakes during initial brake application before the effects of weight transfer
become apparent.
WORKING

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• The simple idea behind an EBD system is that it need not be necessary to apply
the same amount of braking force on each wheel so as to reduce the speed of
the car or bring it to a complete stop.
• An EBD system makes use of three components which make it tick. The speed
sensors, brake force modulators and electronic control unit (ECU).
• Speed Sensor: The speed sensor not only calculates the speed of the car, but
the speed of the engine also (RPM). One of the scenarios can be that the speed
of the wheel might not be the same as the speed of the car. Such a situation
can lead to the wheel(s) skidding. The speed sensors calculate the slip ratio
and relay it to ECU.
• Electronic Control Unit: It is a small chip which collects the data from the
speed sensors in each wheel and uses the data to calculate the slip ratio
(difference between the speed of the car and the rotation of the tyre). Once the
slip ratio is determined, it makes use of the brake force modulators to keep the
slip ratio within limits.
• Brake Force Modulators: It is the job of these modulators to pump brake fluid
into the brake lines and activate the brake cylinders. The brake force applied
on each wheel can be modulated.

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Q4. Short note on Traction Control System (TCS)
Traction control system (TCS):
• TCS is an abbreviation of Traction Control System. As the name suggests, this
system deals with controlling the traction of the drive wheels of the vehicle.
• The main purpose of employing this system is to control wheel slip occurring
during acceleration on slippery roads.
• The TCS is always coupled with ABS and uses the hardware of ABS to function.
Usually, it is experienced that the wheels of a vehicle spin on the same location
without moving forward when accelerated on slippery roads like ice covered
roads.

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• This happens due to the reduced friction. In such a case, if the speed of rotation
of that wheel lowers, then the wheel achieves its desired tractive force and can
move forward under control. Thus, the role of the TCS begins here.
Working:
• The Electronic Control Unit (ECU) has the module of the Traction Control
System in it. It compares the rotational speeds of drive wheels of the vehicle
with the help of the wheel speed sensors of ABS.
• If any of the drive wheels is rotating with exceptionally high speeds, then the
TCS considers it as the spinning of the corresponding wheel.
• The TCS, then, immediately sends a signal to apply brakes to that particular
wheel.
• Thus, the traction control system avoids the wheel-slip; allowing the driver to
accelerate under control.
• There are some other ways also by which Traction Control System can avoid
wheel spinning such as reducing the engine power delivered to the spinning
wheel or cutting off the fuel supply to some engine cylinders etc.
• A common misconception about the traction control system is that it prevents
the wheel from sticking in the snow.
• But this is not true as the system does not have the ability to increase the wheel
traction above its normal range.
• However, the use of TCS is especially useful for people driving on snow-covered
roads regularly.

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