Vehicle Body Engineering

VEHICLE BODY

ENGINEERING

AT1402 VEHICLE BODY ENGINEERING

OBJECTIVE

At the end of the course, the students will be able to have a sound knowledge for the design of the

vehicles body to give maximum comfort for the passengers and exposed to the methods of stream

lining the vehicles body to minimize drag.

UNIT- I CAR BODY DETAILS

Types: saloon, convertibles, limousine, estate car, racing and sports car. Visibility: regulations,

driver’s visibility, tests for visibility, methods of improving visibility and space in cars. Safety:

safety design, safety equipments for cars. Car body construction; design criteria, prototype

making, initial tests, crash tests on full scale model, Dummies and Instrumentation

UNIT-II VEHICLE AERODYNAMICS

Objectives. Vehicle drag and types; various types of forces and moments, effects of forces and

moments, side wind effects on forces and moments, Various body optimization techniques for

minimum drag, wind tunnel testing: flow visualization techniques, scale model testing,

component balance to measure forces and moments.

UNIT- III BUS BODY DETAILS

Types: mini bus, single decker, double-decker, two level and articulated bus. Bus body layout;

floor height, engine location, entrance and exit location, seating dimensions. Constructional

details: frame construction, double skin construction, types of metal sections used, Regulations,

Conventional and integral type construction.

UNIT-IV COMMERCIAL VEHICLE DETAILS

Types of body; flat platform, drop side, fixed side, tipper body, tanker body, Light commercial

vehicle body types. Dimensions of driver’s seat relation to controls. Drivers cab design.

UNIT –V BODY MATERIALS, TRIM AND MECHANISMS

Steel sheet, timber, plastic, GRP, properties of materials; Corrosion, anticorrosion methods.

Selection of paint and painting process. Body trim items. Body mechanisms.

TEXT BOOK

1. J.Powloski - “Vehicle Body Engineering” - Business Books Ltd, London -1989

REFERENCES

1. Giles.J.C. - “Body construction and design” - Liiffe Books Butterworth & Co. - 1971.

2. John Fenton - “Vehicle Body layout and analysis” - Mechanical Engg. Publication Ltd.,

London – 1982.

3. Braithwaite.J.B. - “Vehicle Body building and drawing” - Heinemann Educational Books Ltd.,

London – 1977.

UNIT –I CAR BODY DETAILS

‘Carriage’ is the term for the vehicle jolting with 5miles/hour to the smooth

comfort vehicle with a km/min. in the early version i.e. 1896-98 –Body is nothing but a

convenient seat for the driver and a cover for the engine and other chassis.

Initially horse carriage builder build the body to a steel framing/chassis.

To reduce the weight and to get difference in shape, sheet metal panels replaced

hardwood framing reinforced with ironwork.

Around 1909-Vehicle speed 12miles/hr-design of body took place.

In 1913 Henry Ford started mass production of cars-Ford “Model-T” with slogan “Car

for everyone”

This car took few man-hours to assemble engine but several man-hours for body

manufacture.

In the next model “Model-A” many wooden components are replaced.

In 1930 Butt corporation of Philadelphia made all metal body, using sheet metal

pressings-jointed by welding.

In 1930 only Spot welding had been introduced.

First style-Two seater open and equipped with sheets for covering the driver and

passengers during inclement weather.

Later a glass screen was erected in front of the driver.

Four-seater style with collapsible hood and celluloid side screen-“all weather” body.

Popular ‘saloon’ model-enclosed body, glass windscreen, wind-up windows and sheet

metal roof.

In 1950 integral construction was introduced in passenger car construction.

Types of Car body

1. Saloon or Sedan

i) Four door saloon

ii) Two door saloon

iii) Pillar less saloon

iv) Hatch back

v) Fast back

vi) Notch back

2. Convertibles

3. Limousine

4. Estate car

5. Sports Coupe

6. Coupe

1. Saloon

Saloon is a passenger car with two rows of seats and adequate passenger space in

the rear compartment for passengers. The vehicle usually has a separate rearboot for

luggage.

- This is most popular passenger car

- Passenger comfort such as easy Entery and Exit, Good A/C,heating,ventelation

system and styling are the fetures of the model.

- Drag co-efficient is about 0.35-0.5

- The features of Two door and Pillar less saloon are as same that of Four door

saloon.

- In Pillar less saloon, there not be center pillar and In case of Two door saloon,

there is only Two doors are available.

- Hatch back- Identified by a rear door including the back window that opens

vertically to access a storage area not separated from the rest of the passenger

compartment. May be 3 or 5-door and 2 to 5 seats.

- Fast back- Fast back sedan is a two-box sedan, with continuous slope from the

roof to the base of the Boot, but excludes the Hatback feature.

- Notch back- Notchback sedan is a three-box sedan, where the passenger volume

is clearly distinct from the trunk volume of the vehicle (when seen from the side).

The roof is on one plane, generally parallel to the ground, the rear window at a

sharp angle to the roof, and the trunk lid is also parallel to the ground.

2. Convertibles

A convertible is a type of automobile in which the roof can retract

and fold away, converting it from an enclosed to an open-air vehicle.

3. Limousine

- limousine is a luxury sedan or saloon car, especially one with

a lengthened wheelbase. The chassis of a limousine may have been extended by

the manufacturer or by an independent coach builder. It is usually provided with

a partition between the passenger compartment and driver compeartment.

- It is provided with components and equipments of high quality and better finish.

-Cusion seats, A/C, cooling glass etc are the features of this model.

4. Eastate car

-The luggage compartment is countinuation of the passenger of the

passenger compartment without partition between them.

-Thus more luggage space and longer wheel base are the speciality of this model.

-The other names are “Universal”, “Kombi”, “ Station wagen”, “Campaing van”,

“Break van”.

-Convertible limousine has provited with windup window and foldind roof.

5. Sports Coupe

-It is a two seater with fixed roof.

-Better Aerodynamic shape to better acceleration.

-Light weight combined with rigidity.

-Drag Co-efficient is 0.2-0.3

6. Coupe

-Similar to sports coupe but with two small seats at back.

Visibility

Good allround visibility is now one of the main requirements of body

design.This is clearely depends on the size of the window openings and their

position relative to the occupents.

Forward visibilty can be improved by bringing the front seats of the

passenger car closer to the front windscreen. On the other hand the problem of

entry is increased, since the distance between the seat and the pillar is decreased.

Ease entery is possible by suitably shaping doors( as shown by dotted line) at

the expence of a more complecated structure.

In military vehicles the downward visibility is improtant and the driver

must be positioned as high as possible in relation to the lower edge of the

windscreen. There are no strict regulations regarding visibility. It is assumed that

the upward angle of the vertical visibility should be such as to enable the driver to

see the trafic lights etc and this must be taken into consideration at the design

stage.

Rearward visibility has assumed considerable importance in modern trafic

conditions and the increase in glass area required to maintain a given rear view

veartical angle with a ‘Fast Back’ window is shown in fig.

Visibility can be divided into two aspects

1. Ability to see

2. Ability to be seen

Safety

Safety equipments for cars:

1. Bumber design: The bumber should be designed to absorb more energy.

2. Ignition switch should be connected with door lock that ignition can be switched ,

only when all four doors are perfectely locked.

3. Airbag and Safety bags have to be used.

4. Herlomatic flash or Horn.

5. Collapsible steering.

6. Heat toughened glass.

Car body Construction

-Four door saloon considered as a hollow tube with holes cut in the sides. Front and

rear bulkheads complete the box form provide torsional stability.Roof stable structure-

curved shape-prevents misalignment.

-Floor-complete panel from front to rear. Fitted with integral straightening ribs to prevent

buckling.

-With sill, Wheel arch, cross member and heelboard- strongest part of the body.

Prototype

Car prototype can be considered to be the test model of a new car design that is

intended to be produced in mass quantity. There is no company that goes out and starts

mass production of a new car, without first creating a prototype of it.

A car prototype can also be referred as a test car. These car prototypes are

developed to demonstrate the new qualities of their product to clients. By subjecting these

car prototypes to numerous tests, the car designer gets to see the strengths, weaknesses,

mistakes and limitations in a new car project. Then, by gathering this information, the car

designer proceeds to rework the design through the car prototype until the car reaches the

objectives of the designer. Sometimes, the participating cars in a race are also called

prototypes. The reason for this is that these cars are not mass-produced. These car

prototypes are specialized machines that are supposed to showcase new innovations and

designs that the car manufacturer carries. These car prototypes are the models for future

mass-produced cars the manufacturer will be creating, based on the results of the tests on

the car prototype.

Tests:

-Initial tests

-Crash test

Dummies and Instrumentation

Crash test dummies are full-scale anthropomorphic test devices (ATD) that

simulate the dimensions, weight proportions and articulation of the human body, and are

usually instrumented to record data about the dynamic behavior of the ATD in simulated

vehicle impacts.

Non-contact optical speed & distance measurement systems EEP-2, EEP-3, Micro

EEP-10 and DAS 1A

Pass by noise measurement system Ex. M/s Bruel & Kjaer, Denmark.

Gyro platform for pitch, roll and yaw measurement

Measurement of steering wheel Ex. M/s Datron Messtechnik, Germany.

Steering torque / angle measurement system

Dynamic simulation software – ADAMS

Correlation software ‘n code’

Ride quality meter

Fuel flow meters (positive displacement type)

High speed multi-channel data acquisition systems

Draw bar pull measuring Equipment

8 – Channel thermal array recorder

UNIT- I I VEHICLE AERODYNAMICS

This study concerns about the airflow around the vehicle body. At a speed of

about 70 km/hr aerodynamic drag exceeds to 50% of total resistance to motion and above

100 km/hr it is the most important factor.

Aerodynamic Drag

Form drag - 57%

Lift drag - 8%

Surface drag -10%

Interference drag -15%

Cooling and ventilation drag - 10%

Aerodynamic forces and moments

Forces

1. Lift force

2. Side force or cross wind force

3. Drag force

Moments

1. Rolling moment

2. pitching moment

3. Yawing moment

Optimization Technique

1. Modification of Fore body

2. Modification of windshield

3. Modification of Roof

4. Modification of vehicle rear end

Wind tunnel and Flow visualization test

It is the most useful tool to study the aerodynamic aspects of the vehicle. The

various forces and moments can be evaluated for the vehicle by using scale models.

The instrument used to measure the forces and moments is called a component

balance.

Flow pattern can be obtained by using smoke method, Tuft or Oil coating methods.

Advantages of wind tunnel test

1. Wind velocity and wind angle can be easily and accurately measured.

2. Flow pattern study can also be made accurately.

3. Forces and moments can be measured simultaneously.

4. Testing time and cost is less.

UNIT- I I I BUS BODY DETAILS

Types of Bus body

1. Classic or Normal control bus

2. Single deck bus

3. Split level

4. Double Decker

5. Two level single Decker

6. Articulated bus

1. Classic or Normal control bus

This type of bus has the engine in front of the passenger carrying

compartment. This design which has almost universal at one time has practically

disappear and is mainly of historical interest.

2. Single Ducker

The single deck bus is almost universal today as this layout eliminates all

the disadvantages of above type.

3. Split level

It is intermediate solution between single and double ducker. It having

More seats than single ducker and more stability than Double Ducker.

4. Double Decker

These vehicles have more number of seats for a given overall length but

Stability is not so high compared to single ducker.

5. Two level single Decker

It is used for luxury coaches. This layout provides good forward visibility

for all passengers. good luggage space and easy installation of an under floor or

rear engine.

6. Articulated bus

Bodies for very large coaches or in particular city buses are often made in

two parts because of axial load limitations

Classification of bus by Passenger capacity

1. Micro bus

2. Small coaches for long distance

3. Small buses for towns

4. Medium coaches for long distance

5. Medium buses for towns

6. Large coaches for long distances

7. Large buses for towns

8. Very large buses for towns

Body design aspects

1. Floor height

Shaping of the frame allows the body to be lowered. The floor should be placed as

low down as possible so that the distance of center of gravity from the road surface is

as small as possible.

2. Power plant location

1. Engine behind the front axle

2. Engine above front axle

3. Engine in front of front axle

4. Engine at rear

5. Engine at under floor

3. Location of Entrance and Exit

Construction details

Frame construction

1. Chassis preparation

2. Side and front framing

3. Roof framing and rear end

4. Truss panel riveted

5. General inspection

6. Flooring and interior lining

7. Roof panels

8. Panelling and moulding

9. Final finishing

Double skin construction

All metal bodies or composite bodies are adopted for bus body

construction. In composite body construction wood is used considerably in between

metal member and outside panels. Double skin construction is also being adopted.

Normally inner skin will take part in load carrying and outer skin will be fixed in

such a way that it can be replaced easily.

Types of metal sections used

1. Curved section

2. Channel section

3. Angle section

4. Zed section

5. Corner pillar section

6. Drip rail section

Regulations

There are nothing but laws regarding the length, height, width, window

height and width, door height and width, front overhang and rear overhang, roof

height from the floor etc.

Conventional and integral type construction

Conventional design

The conventional chassis building involves in building up of a ladder type

frame with two long side members interconnected by cross members at intervals. The

units like engine, gear box, radiator, axles, steering wheel, fuel tank are mounted on

the frame.

Integral design

In the integral bus construction, the base structure is formed by building a

structure with four long side members, cross members out-riggers and wheel arch

supports, units like engine, gear box, axles etc. These are mounded on the flexible

under structure, which is fabricated by welding.

UNIT IV COMMERCIAL VEHICLE DETAILS

Types of body

1. Flat platform

2. Drop side

3. Fixed side

4. Tipper body

5. Tanker body

Flat platform - A flat structure consists of a floor blade with edge members and

beams which are used to mount the engine and suspension elements.

Drop side - This type of body follows the main structure of the flat platform body

with an addition of timber sides and a tailboard, capable of being drop to assist in

loading and unloading.

Tipper body - The prime requirement of any tipping body is that it shall be a rigid

unit capable of withstanding the rough usage to which the type of body is subjected.

Tanker body-Commodities carried by tanker includes fuel, oils, milk, water, varnish,

and edible oils etc. In the case of fuel transport, to ensure safe handling, internal

baffle plates are used to cut down the surge of liquid.

Light Commercial vehicle types

1. Single rear door with under-floor compartment van

2. Two door van

3. Two door with sliding side door van

4. Multi door van

5. Raised roof van

6. Workshop van

Dimensions of driver’s seat

1. Heavy forward control

2. Heavy normal control

3. Passenger car

The following pints must have in mind when planning the driver’s seating position

1. The most comfortable position of the body is achieved when the bulk of the

weight of the seated person is taken by the ischial bones.

2. The seat cushions should be fairly rigid and must have sufficient shock absorbing

qualities to prevent resonance of any springs that may be incorporated.

3. A good back-rest relieves the neck and shoulder muscles.

4. The angle between the seat and back-rest must be ohtuse.

5. Armrests reduce tiredness.

Drivers cab design

1. Forward control cab

2. Normal control cab

3. long distance cab

The design of the cab should ensure a degree of comfort for the group directly

related to the duration of the work inside it, modern cabs in trucks are having

comfortable as passenger cars.

UNIT –V BODY MATERIALS, TRIM AND MECHANISMS

Body materials

1. Timber

2. Steel sheet

3. Plastic

4. GRP

1. Timber

Before the introduction of plastics, timber was used in vehicle body

construction, because it is readily available, easily worked and

economically competitive, so far as the smaller manufacturer.

2. Steel sheet

The vehicle body building industry uses many different types of steel.

Low carbon steel is used for general construction members. High tensile

steels are used for bolts and nuts which will be subjected to heavy load.

The steel sheet thickness various from 0.08mm to 1.5mm. This type of

sheet metal is mostly used in vehicle body construction.

3.GRP

It is a combination of two basic materials. One is glass fiber and other is

thermoplastic resign. The resign materials are relatively low strength,

brittle but when combined with glass fiber it becomes strong material.

4. Plastic

The use of plastics for interior trim is well established, and new

applications are being found for components associated with the running

gear, examples including reservoirs, air cleaner housings, belt covers etc.

Corrosion and Anti-corrosion

A vehicle body exposed to corrosion through out its life and because of the load

carrying structure determines the service life of the vehicle, it is essential that it should be

properly protected against such effects. There are three types of vehicle body corrosion.

1. Chemical corrosion

2. Electro chemical corrosion

3. Fretting corrosion

Anti-Corrosion treatment

Corrosion can be prevented by three basic methods

1. Improve materials.

2. Protective coating.

3. Correct design.

Selection of paint

The colors for finishing the vehicle should be based on scientific principles of

colouring, which can be briefly outlined as follows,

All shades are based on three colours i.e Blue, yellow and red. The basic concepts of

colour technology are as follows,

TONE: The tone of colour can be defined by its position in the spectrum. i.e Wave length

VALUE: Value can be measured by the mixture of a natural grey, value corresponds to

the concept of brightness or darkness of colours

INTENSITY: Intensity is defined by the mixture of white in the colours, where full

colour has no white mixed with it.

Painting processes

1. Cleaning

2. Pre treatment

3. Priming

4. Finish coating

5. Stoving

Trim

All items added to the body structure are called trim items. Seat cushions,

instruments, accessories such as ventilation and A/C system, floor lining, head linings,

door locks, window winding mechanism, lights, mirrors, etc. are called trim items.

Body mechanisms

1. Door locking mechanisms

2. Window winding mechanism

3. Seat adjustment mechanism