Automobile module iv

CHASSIS, BRAKES AND
TYRES
Anoop P
Asst. Professor
Dept. of Mechanical Engg.
MITS, Puthencruz
Department of Mechanical Engineering, MITS Puthencruz
1

CHASSIS AND FRAMES
2

CHASSIS
Chassis is a French term which is now denotes the whole vehicle
except body.
“Chassis consists of engine, power train, brakes, steering system
and wheels mounted on a frame”.
3

4

REQUIREMENTS OF FRAMES
5

FRAME
A frame is the main structure of the chassis of a motor vehicle. All
other components fasten to it.
6

CONSTRUCTION OF A FRAME
7

CLASSIFICATION OF FRAMES
1. Conventional frame
2. Integral frame
3. Semi-integral frame
8

9

CONVENTIONAL FRAME
10

11

INTEGRAL/UNITIZED FRAME
12

13

SEMI-INTEGRAL FRAME
14

TYPES OF FRAMES
1. Ladder Frame
2. Backbone Frame
3. X-frame
4. Perimeter Frame
5. Platform Frame
6. Unibody (or) Unit body
7. Sub Frame
15

LADDER FRAME
The ladder frame is the simplest and oldest of all designs.
It consists of two symmetrical rails, or beams, and cross member
connecting them.
Originally seen on almost all vehicles, the ladder frame was gradually
phased out on cars around the 1940s and is now seen mainly on trucks.
This design offers good beam resistance because of its continuous rails
from front to rear, but poor resistance to torsion.
Also, the vehicle's overall height will be higher due to the floor pan sitting
above the frame instead of inside it
16

17

BACKBONE FRAME
Backbone frame is a type of an automobile construction frame that is
similar to the body-on-frame design.
Instead of a two-dimensional ladder type structure, it consists of a
strong tubular back bone (usually rectangular in cross section) that
connects the front and rear suspension attachment areas.
A body is then placed on this structure.
18

19

X-FRAME
This is the design used for the full-size American models of General Motors.
In which the rails from alongside the engine seemed to cross in the passenger
compartment, each continuing to the opposite end of the cross member at the
extreme rear of the vehicle.
It was specifically chosen to decrease the overall height of the vehicles, and
to increase in the space for transmission.
The X-frame was claimed to improve on previous designs, but it lacked side
rails and thus did not provide adequate side-impact and collision protection.
So This design was replaced by perimeter frames.
20

21

PERIMETER FRAME
Similar to a ladder frame, but the middle sections of the frame rails sit
outboard of the front and rear rails.
This was done to allow for a lower floor pan, and therefore lower overall
vehicle in passenger cars.
In addition to the perimeter frame allows lower seating positions when that
is desirable, and offers better safety in the event of a side impact.
However, the design lacks stiffness, because the transition areas from front
to center and center to rear reduce beam and torsional resistance.
22

23

PLATFORM FRAME
This is a modification of the perimeter frame in which the passenger
compartment floor and often the luggage compartment floor were
permanently attached to the frame, for extra strength.
Neither floor pieces were sheet metal straight off the roll, but had been
stamped with ridges and hollows for extra strength.
This was used by the Germans on the Volkswagen Beetle and the
Mercedes-Benz "Ponton" cars of the 1950s and 1960s, where it was called
in English-language advertisements as the "frame floor".
24

25

UNI-BODY
In an unibody (also unit body, unitary construction, or unitized
construction) design.
the frame and body are constructed as a single unit.
This became the preferred construction for mass market automobiles and
crossovers especially in the wake of the two energy crises of the 1970s
and the mid-2000s oil price increases.
26

27

SUB FRAME
A subframe is a structural component of a vehicle.
Such as an automobile or an aircraft, that uses a separate structure within
a larger body-on-frame or unit body to carry certain components, such as
the engine, drivetrain, or suspension.
The sub frame is bolted and/or welded to the vehicle.
When bolted, it is sometimes equipped with rubber bushings or springs to
dampen vibration.
28

The principal purposes of using a subframe are, to spread high chassis
loads over a wide area of relatively thin sheet metal of a monocoque body
shell, and to isolate vibration and harshness from the rest of the body.
For example, in an automobile with its power train contained in a subframe,
forces generated by the engine and transmission can be damped enough
that they will not disturb passengers.
As a natural development from a car with a full chassis, separate front and
rear subframes are used in modern vehicles to reduce the overall weight
and cost.
29

30

VARIOUS LOADS ACTING ON THE FRAME
1. Short duration Load – While crossing a broken patch.
2. Momentary duration Load – While taking a curve.
3. Impact Loads – Due to the collision of the vehicle.
4. Inertia Load – While applying brakes.
5. Static Loads – Loads due to chassis parts.
6. Over Loads – Beyond Design capacity.
31

MATERIALS FOR FRAME
32

CRUMPLE ZONE
Crumple zones were first introduced in cars by Mercedes-Benz in
1953.
The introduction saw a complete shift in the design of cars.
Where previously cars were designed with extremely rigid bodies
that were intended to be very resistant during an accident they
were now built so that they would crumple or deform in the event
of a crash
33

Crumple zones are areas at the front and back of a car that are
designed to deform in a controlled manner in the event of an accident.
They are intended to increase the stopping time of a collision so
therefore decrease the force acting on the occupants.
Crumple Zones are designed to absorb the kinetic energy from impact
during an accident by controlled deformation.
The purpose of crumple zones is to reduce the force experienced by
the occupant of a car during a crash.
This is achieved by the controlled deformation of the crumple zones
during a collision.
The crumpling increases the stopping time and prevents the car from
rebounding.
This has the effect of minimizing the momentum change and the
impulse and so the forces experienced by the occupants is minimized.
34

35

IMPACT BEAMS/ ANTI -INTRUSION BAR
An anti-intrusion bar or beam is a passive safety device,
installed in most cars and other ground vehicles, which must
protect passengers from side impacts.
Side impacts are particularly dangerous for two reasons:
a) the location of impact is very close to the passenger, who can
be immediately reached by the impacting vehicle
b) in many side-impact accidents, the impacting vehicle may be
larger, taller, heavier, or structurally stiffer than the struck
vehicle.
The role of an anti-intrusion bar is to absorb the kinetic energy of
the colliding vehicles that is partially converted into internal work
of the members involved in the crash.
36

37

SEATBELTS
Seatbelts limit the forward motion of an occupant, stretch to
absorb energy, to lengthen the time of the occupant's negative
acceleration in a crash, reducing the loading on the occupants
body.
They prevent occupants being ejected from the vehicle and
ensure that they are in the correct position for the operation of the
airbags.
38

AIR BAGS
Airbags inflate to cushion the impact of a vehicle occupant with
various parts of the vehicle's interior.
The most important being the prevention of direct impact of the
driver's head with the steering wheel and door pillar.
39

40
An airbag is an automotive safety restrain system for an occupant as well
as passengers. The system consists of a flexible fabric envelope or
cushion, designed to inflate rapidly during an automobile collision.
A safety device used in the four wheelers to avoid the Head and Chest
injuries from collision by providing the cushion between the occupants.

AIR BAG INFLATION SYSTEM
The sensor sends the electric signal to burn the propellant kept
here to generate the gas
Monitors the readiness of the airbag system
A device that stores enough electrical energy to deploy the airbag
if the vehicle’s battery destroyed in it
41

BRAKING SYSTEM
42

INTRODUCTION
Brakes are one of the most important control components of the
vehicle.
They contribute very much in the running and control of the
vehicle.
The efficiency of the brakes depends on the lives and comfort not
only of driver and passengers but other persons moving on the
road.
Furthermore it is a fact that owing to recent improvements in the
braking mechanism may be chiefly attributed the increased
speeds of the modern cars on the road.
43

FUNCTION
To stop the moving vehicle in the shortest possible distance.
To help in controlling the speed of the vehicle and to reduce the
speed at turning and other crowded places.
To control the speed of vehicle at turns and also at the time of
driving down on a hill slope.
44

PRINCIPLE
Braking of a vehicle depends upon the static function that acts between
tyres and road surface.
Brakes work on the following principle to stop the vehicle :
“The kinetic energy due to motion of the vehicle is dissipated in the form
of heat energy due to friction between moving parts (wheel or wheel
drum) and stationary parts of vehicle (brake shoes)”.
The heat energy so generated due to application of brakes is dissipated
into air.
Brakes operate most effectively when they are applied in a manner so
that wheels do not lock completely but continue to roll without slipping on
the surface of road.
45

CLASSIFICATION
On the Basis of Method of Actuation
• Foot brake (also called service brake) operated by foot pedal.
• Hand brake – it is also called parking brake operated by hand.
On the Basis of Mode of Operation
• Mechanical brakes
• Hydraulic brakes
• Air brakes
• Vacuum brakes
• Electric brakes.
On the Basis of Action on Front or Rear Wheels
• Front-wheel brakes
• Rear-wheel brakes.
On the Basis of Method of Application of Braking Contact
• Internally – expanding brakes
• Externally – contracting brakes.
46

MECHANICAL BRAKES
47

INTERNAL EXPANDING BRAKE
48

EXTERNAL CONTRACTING BRAKE
49

HYDRAULIC BRAKES
50

51

Hydraulics is the use of a liquid under pressure to transfer force or motion, or to
increase an applied force.
The pressure on a liquid is called HYRAULIC PRESSURE.
And the brakes which are operated by means of hydraulic pressure are called
HYDRAULIC BRAKES.
These brakes are based on the principle of Pascal’s law.
52

A TYPICAL HYDRAULIC BRAKE
53

PASCAL’S LAW
The pressure exerted anywhere in a mass of confined liquid is transmitted
undiminished in all directions throughout the liquid.
Applied in hydraulic lifts, hydraulic brakes etc.
54

MASTER CYLINDER IN ACTION
When we press the brake pedal, it pushes on primary piston through a linkage.
Pressure is built in the cylinder and the lines as the brake pedal is depressed
further.
The pressure between the primary and secondary piston forces the secondary
piston to compress the fluid in its circuit.
If the brakes are operating properly, the pressure will be same in both the circuits.
If there is a leak in one of the circuits, that circuit will not be able to maintain
pressure.
55

TANDEM MASTER CYLINDER
56

WORKING
57

58

WHEEL CYLINDER/SLAVE CYLINDER
59

60

BLEEDING OF BRAKES
When air enters, into the brake system and any brake line is
disconnected, bleeding of brakes has to be done.
Since air is compressible so any presence of air inside brake
lining does not allow to transmit brake force to apply brakes.
Therefore, the system must be free from presence of air.
“ Bleeding is the process of removal of air from the braking
system”.
61

BLEEDING PROCEDURE
Remove all dirt from the master cylinder filler plug. Then fill the master cylinder
up to lower edge of the filler neck by removing the filler plug.
Clean all the bleeding connections provided on all wheel cylinders.
After this bleeder hose and fixture is connected to that wheel cylinder which has
longest brake line. The other rend of bleeder hose is placed in a glass jar, and
submerge this end in the brake fluid.
How bleeder valve is opened by half to three quarter turn.
Then press the foot pedal and allow it to return back slowly.
This pumping action must be continued till all the air along with some brake fluid
comes out through bleeding hose.
After this bleeding operation is carried out on all wheel cylinders. This completes
the bleeding operation. At the end master cylinder is filled with brake fluid to
required level
62

ADVANTAGES OF HYDRAULIC BRAKES
63
Equal braking effort to all the four wheels
Less rate of wear (due to absence of joints compared to mechanical
brakes)
Force multiplication (or divisions) is very easy by changing the size of one
piston and cylinder relative to other.
DIS-ADVANTAGES OF HYDRAULIC BRAKES
Even slight leakage of air into the breaking system makes it useless.
The brake shoes are liable to get ruined if the brake fluid leaks out.

VACUUM BRAKE
64

65

DRUM BRAKES
Drum brakes work on the same principle as the disc brakes. Shoes
press against a rotating surface.
In this system that surface is called a drum.
Drum brake also has an adjuster mechanism, an emergency brake
mechanism and lots of springs.
The shoes are pulled away from the drum by the springs when the
brakes are released.
66

DISC BRAKES
67
In a disc brake, the fluid from the master cylinder is forced into a caliper
where it presses against a piston.
The piston in turn squeezes two
brake pads against the disc
(rotor), which is attached to
wheel, forcing it to slow down
or stop.

68

EMERGENCY BRAKES
In cars with disc brakes on all four wheels, an emergency brake has to be
actuated by a separate mechanism than the primary brakes in case of a total
primary break failure.
Most cars use a cable to actuate the emergency brake.
Some cars with four wheel disc breaks have a separate drum brake integrated
into the hub of the rear wheels.
This drum brake is only for emergency brake system and is actuated only by
the cable.
It has no hydraulics.
69

APPLICATIONS OF BRAKESDisc brake
used in aircraft brakes; preferred for front axles of vehicles, motorcycles, scooters, bicycles, Still-
larger discs are used for railroad cars and some airplanes. Passenger rail cars and light rail
vehicles, in racing and very-high-performance road cars.
Hydraulic brakes
Used in automobiles, cranes and lifts or elevators, airplanes, mining vehicles etc.
Air Brakes
used in large heavy vehicles, such as trucks, buses, trailers etc.
Vacuum Brakes
In railways ( India and South Africa) in the mid-1880s.
Electric brakes
Brake controlled by an electric current and are seen on medium duty trailers like caravans,
Recreational vehicle and Consumer-Grade Car Trailers.
Internally – expanding brakes
This type of brake is commonly used in motor cars and light trucks.
Externally – contracting brakes
This type of brake is used on the wheel brakes of cars and. trucks because it permits a more
compact and economical construction.
70

AIR BRAKES
71

COMPONENTS
The main components of air brake system are :
Air compressor with air filter to compress atmosphere air.
Un-loader valve to maintain a set pressure.
Air reservoir to store compressed air at specified pressure.
Brake valve to control the intensity of braking.
Brake chambers are installed at each wheel to convert air pressure into useful
mechanical energy.
72

ADVANTAGES
Air brakes are more powerful than mechanical or hydraulic brakes,
are exclusively used in heavy vehicles.
The air brake simplifies the chassis design. The components of the
system can be located on the chassis any where and are
interconnected by a pipe line.
Apart from braking, the compressed air from the reservoir can be
used for tyre inflation, windscreen wipers, horns and many other
accessories.
73
DIS-ADVANTAGES
Air brakes involve more parts.
Air compressor uses engine power.

ELECTRIC BRAKES
This type of brakes are not very popular, as service brakes.
These are commonly used on trailers.
The current from the battery is utilized to energize an electromagnet within
the brake drum.
This actuates a cam to expand the brake shoes.
When current stops, the cam and brake shoes are returned to the release
position by retractor springs.
The severity of braking is controlled by means of a rheostat, which is
operated by the driver through the foot pedal.
Hydraulic pressure has also been used to apply electric brakes. As pedal is
pressed more, hydraulic pressure actuates the rheostat to increase current to
the electromagnet.
74

ADVANTAGES OF ELECTRIC BRAKES
The operating linkage is simplified in electric brakes. The require only one
cable for each drum.
There is less time-lag between the pressing of the brake pedal and application
of brakes at the wheels.
For trailer brakes, this type offers much simplified connection; simply on cable
has to be carried to the trailer side.
75

ENGINE EXHAUST BRAKES
76

This type of brake is used on Tata vehicles as a auxiliary brake.
It is meant for use while travelling on a lengthy downhill gradient and
in heavy traffic.
It becomes necessary to slow down continuously over a large
distance.
The brake comes into operation when the foot control valve is
pressed and remains engaged as long as this valve is kept pressed.
The moment the foot is taken off the valve, the brake gets released.
When the foot control valve is pressed, the compressed air from the
air tank enters the air cylinder, where it operates a linkage to close
the butterfly valve at the exhaust manifold.
This brake is used to sow down the vehicle speed to 40 kmph or
less.
77

HAND BRAKE/ PARKING BRAKE
78
Hand brakes are usually the mechanical brakes.
On most of the vehicles hand brake applied only the
rear brakes.

WHEELS AND TYRES
79

INTRODUCTION
The importance of wheels and tyres in the automobile is obvious.
Without the engine the car may be towed, but even that is not
possible without the wheels.
The wheel, along with the tyre has to take the vehicle load, provide a
cushioning effect and cope with the steering control.
80

REQUIREMENTS
The various requirements of an automobile wheel are:
1. It must be strong enough to perform the above said functions.
2. It should be balanced both statically as well as dynamically.
3. It should be lightest possible so that the un-sprung weight is least.
4. It should be possible to remove or mount the wheel easily
5. It material should not deteriorate with weathering and age. In case the
material is susceptible to corrosion, it must be given suitable protective
treatment
81

WHEEL - BASICS
82

TYPES OF WHEELS
Disc Wheel
Wire Wheel
Alloy Wheel
83

DISC WHEEL
84

OUTSET, ZERO SET, IN SET
85

WIRE WHEEL
86

ALLOY WHEEL
87

TYRE -FUNCTIONS
• Act as the primary suspension, cushioning the vehicle from
effects of rough surface.
• Provide frictional contact with the road surface which allows
the driving wheels to move the vehicle
• Front tyres allows the wheels to steer
• Tyres allow braking to slow or stop the vehicle
88

PROPERTIES OF TYRES
•Non-skidding
•Uniform wear
•Load-carrying capacity
•Speed Capacity
•Cushioning
•Power consumption
•Noise
•Balance
89

TERMINOLOGIES
• Steel Wheels – Most popular design. Very strong and cheap to produce.
• Alloy Wheels – Attractive and light weight, but expensive and difficult to clean.
• Spoked Wheels – Used on older vehicles. Cannot be fitted with tubeless tyres.
• Divided rims – Rims are made in two halves which are bolted together, (rims must never be
separated while the tyre is inflated)
• Split rims –Tyre is held in place by a large circlip
• Plies – Layers of strong fabric which are built up to give the tyre its strength and shape
• Bead – loops of steel which are the anchor point for the plies
• Cross Ply Tyre – Main plies of the tyre run at an angle (45 degrees) from one bead to the
other
• Radial Ply Tyre – Main plies of the tyre run at 90 degrees from one bead to the other
• Tread – Rubber pattern. Provides grip with the road surface and assists in clearing water
away
• Side Wall – Connects the beads to the tread of the tyre
90

PARTS
•Beads: Two rings that are made of steel wire and encased in rubber. They
hold tire side walls snugly against the rim and prevent tyre from coming off
•Body Plies: Rubberized fabric and cords wrapped around beads. Form
carcass or body of the tyre.
•Tread: Outer surface of the tyre that comes in contact with the road
91

•Sidewall: Outer part of the tyre that extends from the bead to the tread.
•Marking on the sidewall provides the information about the tyre.
•Liner: Thin layer of rubber that is bonded to the inside of the plies.
Provides a leak proof membrane for tubeless tires.
•Belts: Used to strengthen the body plies and stiffen the tread.
•Lie between tread and plies
92

CUTAWAY SECTION OF A TYRE
93

BIAS PLY/CROSS PLY TYRE
•One of the oldest design
•Several textile plies are laid across each other, running from bead to
bead in alternate directions
•Number of plies depends on the size of the tyre and the load it has to
carry
•Same number of plies is used on the crown and the sidewalls
•Plies run at an angle from bead to bead
•Does not use belts
•Allows body of the tyre to flex easily
•Improved cushioning, hence smooth ride on rough roads
•Weakness: Reduced traction at high speeds and increase rolling
resistance
94

95

RADIAL PLY TYRE
•Plies run straight across from bead to bead.
•Has a very flexible sidewall and a stiff tread, giving it a very stable
footprint
•Consist of a carcass ply formed by textile arcs running from one bead to
the other.
•Each ply is laid at an angle of 90 degrees to the direction the tyre rolling
•At the top of the tyre crown (under the tread), a belt made up of several
plies reinforced with metal wire is laid.
•These crown plies, laid one on top of the other, overlap at an angle
determined by the type of the tyre.
96

97

BELTED BIAS TYRE
•Bias ply tyres with belts added to increase tread stiffness.
•Belts do not run around the sidewalls, they lay under the tread area
only
•Belts and plies run at different angles
•Offers some reduction in rolling resistance over a bias ply tire
•Provides smooth ride and good traction
98

99

100

ADVANTAGES OF RADIAL PLY TYRES
•Side walls can bend easily, its shock absorbing capacity is 25% more
than bias ply or cross ply.
•Lower rolling resistance and hysteresis loss leads to less fuel
consumption
•Longer tread life because of less heat build in tyre.
•Breaking efficiency on wet roads is better because of greater sidewall
flexibility and tread stiffness.
•Better steering characteristics.
•While taking turns it has less tendency to distort and lift off the road from
one side.
•Larger resistance to punctures ,cuts and impacts in the tread area.
101

102
Bias contact patch Radial contact patch

Non-Directional Tyres
Uniform grooves
Can run in any direction
Unidirectional Tyres
Grooves are in one direction
Direction of rotation is clearly marked
103

TUBED AND TUBELESS TYRES
104

CROSS-SECTION OF TUBELESS TYRE
105

ADVANTAGES OF TUBELESS TYRES
•Lesser un-sprung weight.
•Better cooling
•Lesser rolling resistance
•Comfortable ride
•Slower leakage of air
•Simpler assembly
•Improved safety
106

TYRE SPECIFICATIONS
107

108

NITROGEN IN TYRES
•Makes up around 80% of the air
•Dry inert gas. It is less reactive than oxygen.
•Leaks out of the sidewall three times slower then oxygen.
•Oxygen oxidizes the rubber in the sidewall.
•Pumped into tyres in a pure form, hence it does not contain moisture found
in compressed ambient air which causes rusting of steel rims.
•The result is that all materials that come into contact with the compressed
gas inside the tyre are less subject to oxidation corrosion
109

WHEEL BALANCING
110

TYRE ROTATION
111

CAUSES OF TYRE WEAR
• Over inflation
• Under-inflation
• Front-wheel-Misalignment
• Rear-wheel Misalignment
• Defective wheels
• Excessive Speeds
• Excessive Wheel Camber
• Flats on Tyres
112

THANK YOU!!!
113

Automobile module iv

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Automobile module iv