Vehicle body

SRI KRISHNA COLLEGE OF ENGINEERING AND TECHNOLOGY
DEPARTMENT OF MECHATRONICS ENGINEERING
Session: Vehicle Body Construction
11/24/2020 16MT407 - Theory of Automobile Engineering 1
MODULE 1

SESSION OBJECTIVES
 On the completion of this session, the students might
be able to understand,
 How the various parts form the vehicle body to
give aesthetic view to the consumer?

Topics
 Introduction
 Importance of vehicle body design
 Different Types of vehicle Body
 Body Construction & its components
 Requirements of automobile body
 Materials for body construction work
 Aerodynamic in vehicle body construction

INTRODUCTION
The basic form of the modern automobile body is older horse driver carriage
Less Speed, Little stylish, Little space More speed, More stylish, Large space

INTRODUCTION
What is automotive
body :
 Body is the super
structure for all vehicle.
 It may either be
constructed separately
and bolted to the
chassis or manufactured
integral with the chassis
(i.e Frameless
Construction).
 The chassis & Body
make the complete
vehicle.

IMPORTANCE OF VEHICLE BODY DESIGN
Importance of vehicle body design:
 The body should be light.
 It should have minimum number of
components.
 It should provide sufficient space for
passenger and luggage.
 It should withstand vibration while in
motion.
 It should offer minimum resistance to air.
 It should be cheap & easy in manufacturing.
 It should be attractive in shape & colour.
 It should have uniformly distributed load.
 It should have long fatigue life.
 It should provide good vision & Ventilation.

TYPES OF VEHICLE BODY
Types of vehicle Body :
CAR
Straight Truck
Truck Half Body
Platform type truck

INTRODUCTION
Tractor
Tractor with articulated trailer
Dumper Truck
Tanker truck

INTRODUCTION
Delivery Van
Station Wagon
Jeep
Pickup truck

BODY CONSTRUCTION AND ITS COMPONENTS
Body Construction and its components:
Purpose of car body :
 The main purpose of car body is for
containing and protection of engine &
accessories as well as passenger.
 To fulfil the above requirements, the vehicle
body has classified as three groups.
1. Structure : All body load carrying elements
are defined as structure.

2. Finish: This groups includes all unstressed
units like bonnet, boot, Lid bumper, etc.
Lid bumper
Boot Space
Bonnet

3. Equipment : This group includes various
parts like Rim, Seats, Door’s, Window etc.
Rim
Seats
Door’s & Window

COMPONENTS OF CAR BODY
Components of car body:
The various components of car body are,
 Body
 sheets
 Bonnet
 Front & Rear Doors
 Front panels
 Roof panels
 Floor panels with engine beams
 Wheel arches
 Wind screen pillar
 Wind screen front & rear
window
 Front & Rear bumber
 Cowl Assembly
 Seats, Hood, etc.

The formation of the structure :
 All steel section of bodies are stamped out
by dies separately & welded to other section
for forming all steel bodies
 The body of the car is made up of many
sheet metal panels.
 Which gives strength & rigidity to the car.
The main skeleton of the car body has two
types of panels
1. Outside panel – Give shape of the car
2. Inside panel – Reinforce the shell of the
body

The formation of the
structure :
 Initially the floor of the car
body is assembled and
then pillars, rails, and
panels are welded in order
to form the complete car
body
 The floor is made of three
pressed steel panels such
as front, center & rear
section FRONT
MID
REAR

 The inner panels provide mounting location
for various trim panels and connecting
assemblies.
 This two panels are welded together and to
the pillars and rails so as to form the
skeleton of the body.

 The floor panel unit gives lower profile & car
accommodates more passenger.
 The rear wheel houses inner panels and
rocker panels are welded to the floor panel .
 The wheel house panel is accommodate with
wheel axle movement.
 The box shaped rocker panel which gives
additional strength to the floor panel
wheel house panel
Rocker panels

COWL ASSEMBLY :
 The Cowl assembly or front portion of the
car is made up of many smaller panel
stamping of sheet metal.
 The top outer cowl panel is sometimes
vented to allow the fresh air into the car.
 The pillars on the sides of the cowl are
used for fastening the front door hinges
and the cowl side panels.
 The fire wall of the cowl assembly is the
sheet metal panel which separates the
front passenger space from the engine.
 This wall is insulated, so engine heat &
Noise cannot reach passenger
 Finally the cowl is welded to the
rocker panel & the floor panel

DASHBOARD :
 Instrument panel / Dashboard are welded
or bolted to the cowl

Construction of center
pillars:
 The center pillars supports
the rear doors and hinges. It
also supports the sticker
plates of the front doors
 The roof rail & center pillars
are usually of box section. It
gives maximum strength to
the body.

Drip Mounting:
 Drip Mounting are added to
the side rails of the roof the
roof panel.
 The drip Mounting are U-
Shaped channel
 It is used to catch & Direct
the water to the back of the
car during raining.

Roof Panel:
 The roof panel is welded to
the top side rails.
 The rear window & Front
windshield frames are
attached to the roof panel by
spot welding.

Quarter panel:
 A quarter panel is the body
panel of an automobile
between rear door & the
trunk boot.
 It is made of sheet metal or
fiber reinforced plastics
Fender :
 The similar front section
between the door & Hood is
called a fender.

Trunk Lid:
 The trunk lid provides cover
for the trunk compartment.
 It is attached to the body
with the help of hinges.
 In order to prevent the water
and dust to enter into the
compartment a rubber
weather strip is provided.
 Locking arrangement is also
provided for the rear
compartment.

Front End sheet metal:
 Engine compartment is formed by assembling
different sheet metal panels.
 This assembly covers the front wheels &
therefore it prevents the dirt, mud, snow etc.,
being thrown off by the front tyres on the
engine and the body of the car.
 Radiator support bolted with radiator for
support it.
 A stone shield is bolted to the radiator support
and the fenders
 It prevents striking of small flying stones on to
the radiator & thus it avoids their damage
 2 Fenders covers the front wheel are connected
by radiator support
Front End sheet metal
Radiator support
stone shield

Car Engine hood:
 It is constructed in the same
manner as the trunk lid.
 It has inner & Outer panels
 The inner panel acts as the
reinforcement to the engine
hood.
 The provision for mounting
location, Hood lock and hinges
are provided in the inner panel.
 The outer panels gives shape to
the body.
 The hood is attached to the car
body by means of hinges.

Adjustable seat:
 One of the most important
components inside the car is a
seat.
 The seat of the car are various
types such as folding back,
bucket.
 The seats are mounted on rails
which make them adjustable
 The back can also be tilted in
the convenient position.
 They are also provided with
head rest for safety in case of
accident
Folding back/Bench type seat
Bucket type seat

Car Doors:
 Present day cars use four doors,
two in front & Two in rear. Some
having fifth - back side.
 Front door hinged in front pillars
where as rear doors are hinged
on center pillars.
 The glasses used in cars are
specially designed – when its
broken doesn’t form sharp
edges.

Door Glass:
 Toughened glass has been used
for wind screen & window
panels.
 If impact happen on window the
broken piece are in the form of
rounded granules and never
cause injury.
 Now a days laminated glass are
used, while impact crakes only
happen. (No Broken piece)
interlayer, typically of polyvinyl butyral
(PVB) or ethylene-vinyl acetate
(EVA), between its two or more layers of
glass

MATERIALS FOR CAR BODY
Materials for car body:
 Steel (Majority cases, Cheapest, stamped out to form various shape)
 Aluminum is used by some manufacturer – better formability, lightness & anti
rusting quality.
 Plastic also a passion of making car body
 Thermo plastics are often used components like boot covers, grills etc
 Thermosetting plastics – glass reinforced plastics like fiber are being used
for body shells.
 The latest type plastics is carbon fiber (stronger than steel)
 But cost is only disadvantage

AERODYNAMIC IN VEHICLE BODY CONSTRUCTION
Automotive Aerodynamic:
 Whenever a vehicle moves through a
large mass of air which is either
stationary or moving, the air exerts a
force on the vehicle.
 A vehicle body which is not well
designed will have more air resistance
and thus power of the vehicle is lost in
overcoming this resistance
 This results in less power available to
propel the vehicle which affects the
vehicle performance.

Force exerted by air on a moving
vehicle has three components:
 Aerodynamic Drag Force
 Aerodynamic Lift Force

Aerodynamic Drag Force:
It is comprised primarily of two forces
i. Frontal Pressure: It is caused by the
air attempting to flow around the front
of the car.
ii. Rear Vacuum: It is caused by the
“hole” left in the air as the car passes
through it

Frontal Pressure :
 As millions of air molecules approach the front of the car, by begin to
compress & rise the air pressure in front of the car.
 At the same time, the air molecules traveling along the sides of the car are at
atmospheric pressure, a lower pressure compared to the molecules at the
front of the car.
Frontal Pressure is caused by the air attempting to flow around the front of the vehicle

Rear Vacuum :
 It is caused by the “hole” left in the air as a vehicle passes through it.
 At speed above a crawl, the space immediately behind the car’s rear window
& trunk is empty or like a vacuum
 These empty areas behind the car never be filled with air molecules by a fast
moving car.
 But air molecules attempt to fill into this area, but the car is always one step
ahead, and as a result, a continuous vacuum sucks in the opposite direction.
This inability to fill the hole
left by the car is technically
called Flow detachment.

Wake region :
 .When the air moving over the vehicle is
separated at the rear end, it leaves a
large low pressure turbulent region
behind the vehicle known as wake
 This wake contributes the formation of
pressure drag, which is eventually
reduces the vehicle performance

Lift :
 Every object traveling through air
creates either lifting or down force
situation.

Lift :
 Race cars, SUV’s use inverted wings to
force the car down onto the track,
increasing traction.
 But average streets cars tends to create
lift.
 Reason is “Car body itself generates a
low pressure area above itself”
Range Rover –Velar SUV
Maruti Waonar – Street Cars

Lift :
 Under side of the car responsible for
creating Lift or Down force.
 If a front of the end is lower than the
rear end, then the widening gap
between the underside and the road
creates a vacuum, or low pressure area.
 Therefore the suction equates the down
force

 The aerodynamic Drag force in a vehicle
affect the Maximum vehicle speed and
fuel efficiency.
 Commonly known as air resistance.
𝐹 𝐷 = 0.5 𝜌 𝐶 𝑑 𝐴𝑉2
ρ - Air Density in Kg/m3
Cd - Coefficient of Discharge.
A – Projected frontal area in m2
V – Vehicle speed in m/s

 The aerodynamic Lift force in a vehicle
affect the steering & maximum
performance
 Vehicle body design required minimum
or Zero lift force
 Total force acting on body is drag force
only
𝐹𝐿 = 0.5 𝜌 𝐶𝑙 𝐴𝑉2
ρ - Air Density in Kg/m3
Cl - Coefficient of lift.
A – Projected frontal area in m2
V – Vehicle speed in m/s

Way to reduce the drag force on SUV:
 Lowering the front bumper and Bonnet, including the front windshield.
 Rounding off the corners and sharp edges
 Extending the front bumper
 Make small chamfers at the rear end of the roof and the side body there will be
a significant change in the drag.

External Devices that reduces drag:
Spoilers:
 Providing the down force by creating a
“dam” at the rear lip of the trunk
 Works like windshield, & creates a high
pressure in the area above the trunk.

External Devices that reduces drag:
Front Air dams:
 Air dams at the front of the car restrict
the flow of the air reaching the
underside of the car.
 This creates a low pressure area under
the car. effectively providing down force

END

Vehicle body

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