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7 Nov 2011

Vehicle body Engineering by pawloski

VBE

Syllabus- Types: Saloon, convertibles, limousine, estate car, racing and sports car. Visibility: regulations, driver’s visibility, test for visibility, methods of improving visibility and space in cars. Safety design, safety equipments for cars. Car body construction; design criteria, prototype making, initial tests, crash tests on full scale model, Dummies and Instrumentation.

CAR BODY DETAILS

‘Carriage’ is the term for the vehicle jolting with 5miles/hour to the smoothcomfort vehicle with a km/min. in the early version i.e. 1896-98 –Body is nothing but aconvenient 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 “Carfor everyone”This car took few man-hours to assemble engine but several man-hours for bodymanufacture.

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

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:

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 structurecurved

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

Types crash test

§ Frontal-impact tests: which is what most people initially think of when asked about a crash test. These are usually impacts upon a solid concrete wall at a specified speed, but can also be vehicle-vehicle tests. SUV’s have been singled out in these tests for a while, due to the high ride-height that they often have.

§ Offset tests: in which only part of the front of the car impacts with a barrier (vehicle). These are important, as impact forces (approximately) remain the same as with a frontal impact test, but a smaller fraction of the car is required to absorb all of the force. These tests are often realized by cars turning into oncoming traffic. This type of testing is done by the IIHS and Euro CAP

§ Side-impact tests: these forms of accidents have a very significant likelihood of fatality, as cars don’t have a significant crumple zone to absorb the impact forces before an occupant is injured.

§ Roll-over tests: which tests a car’s ability (specifically the pillars holding the roof) to support itself in a dynamic impact. More recently dynamic rollover tests have been proposed as opposed to static crush testing (video).

§ Roadside hardware crash tests: are used to ensure crash barriers and crash cushions will protect vehicle occupants from roadside hazards, and also to ensure that guard rails, sign posts, light poles and similar appurtenances do not pose an undue hazard to vehicle occupants.

§ Old versus new: Often an old and big car against a small and new car , or two different generations of the same car model. These tests are performed to show the advancements in crashworthiness

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

Vehicle Aerodynamics

Vehicle Aerodynamic Factors

§ Aerodynamic Forces

§ Laminar Separation

§ Tripping of Boundary Layer

§ Pressure Distribution

§ Wake

§ Tires

§ Glass and Trim

§ General Improvements

§ Unconventional Features

Aerodynamic Forces

§ Lift force

§ Drag force

§ Side force

§ Effects of aerodynamic forces are profound

§ Force coefficients

§ Example

§ What is a vehicle’s drag force, with a frontal area of 1.5 m², C_D of 0.4, and traveling at 30 m/s

§ Aerodynamic down force

§ Opposite of lift in direction

§ Uses an inverted airfoil

§ Increases load on tires without increasing the vehicle’s weight (up to 10% of vehicle’s weight)

§ Improves cornering performance with no weight penalty

§ First discovered in 1960s!

§ Example of down force

§ Example

§ Rear Spoiler (Mazda RX-7 R-2)

§ C_D = 0.31 (0.29 without spoiler)

§ C_{L front} = 0.10 (0.16 without spoiler)

§ C_{L rear} = 0.08 (0.08 without spoiler)

§ Underbody improvements

§ Aerodynamic properties

§ Reduce drag

§ Increase down force

Laminar Separation

§ Laminar Separation

§ Flow separation inside the boundary layer

§ Laminar Bubble

§ Streamlines enclosed within the laminar separation

§ Laminar bubble area is sensitive and can easily separate, resulting in excess drag

§ Can appear in low Re range (10⁴-10⁵), and disappear as speed increases, causing severe discrepancies in flow visualization and analysis

§ The rear end shape is the most critical factor in lowering the drag coefficient

§ Flow separation above the rear window can cause annoying dirt deposits on the glass

Tripping of Boundary Layer

§ Introduction of aerodynamic disturbances

§ Fins

§ Vortex generators

§ Strips of coarse sand paper

§ Forcing laminar to turbulent flow

§ Drag reduction due to delay in the onset of flow separation

Pressure Distribution

§ Helps the placement of inlets and outlets

§ Lower pressure at the outlet

§ Higher pressure at the inlet

§ Favorable pressure distribution

§ Prevents flow separation

§ Unfavorable pressure distribution

§ Promotes flow separation

§ Promotes turbulent flow within boundary layer

§ Example of inlet

§ Radiator inlet configurations

Wake

§ The disturbed air flow left behind the vehicle

§ Usually in the form of a vortex

§ Caused by merging air flows at different velocities near sharp edges

§ Increases drag

§ Presents danger to the following vehicles

§ Can be controlled with small fins or smooth edges

Tires

§ Tires influence a vehicle’s aerodynamic properties

§ Cross sectional area

§ Frontal area

§ Rotation of tires

§ Effects of tire rotation

§ Effect of all-wheel-steering

Glass and Trim

§ Drag can be reduced by making glass and trim as flush with the body as possible

§ Elimination of rain gutter improves the vehicle aerodynamics

General Improvements

1- Front spoiler

2- Ducted engine cooling

3- Shrouded windshield wiper arms

4- Aerodynamic mirrors

5- Smooth windshield transitions

6- Smooth side window transitions

7- Smooth rear window transition

8- Optimized trunk corner radii

9- Optimized lower rear panel

10 – Smooth fuel tank and underbody

11- Optimized rocker panels

12- Flush wheel covers

13- Elimination of the rain gutter

Unconventional Features

§ Large rear fins promote lateral stability in the 1966 Peugeot CD

§ 1969 Chaparral 2J used auxiliary fans to create suction under the car

§ Ford’s rear mounted transverse engine

§ Fans improve aerodynamic properties and reduce drag

Wind Tunnel

§ Used to study the aerodynamic properties of an object in a stationary manner

§ Motion is simulated by moving air (fluid) around the object of interest

§ Properties measure in wind tunnel include pressures, forces, velocities, and vibrations

§ Wind tunnel studies are not 100% accurate

§ Wind tunnel pictorials:

Types of Wind Tunnels

§ A basic wind tunnel (open-circuit)

§ General Motors’ wind tunnel (close-circuit)

§ Open-circuit wind tunnels

§ Less expensive

§ Subject to ambient conditions

§ Require more power

§ Close-circuit wind tunnels

§ Avoids loss of return air’s momentum

§ Constant ambient conditions

§ Expensive

§ A wind tunnel can not always simulate road conditions, e.g.,

§ Ground effect

§ Tire rotation

§ Reynolds number (scale corrections)

§ Wall interference

§ Natural variations in ambient conditions

§ Challenges

§ Model size

§ The larger, the greater the wall effect

§ The smaller, the less accurate

§ Simulation of the moving road

§ Mounting of model and rotating wheels

§ Wall effect

§ Examples of wall effect corrections

§ Simulation of moving ground

§ Important issue about wind tunnel studies,

§ Understanding the aerodynamic problem is more critical than sensitive instrumentation

§ Whatever works satisfactorily in the wind tunnel, will usually work well on the road

§ Scale model studies are usually too conservative, and the vehicle can be further optimized

Measurement of aerodynamic forces

Ways that air velocity and pressures are measured in wind tunnels:

§ air velocity through the test section (called the throat) is determined by Bernoulli’s principle. Measurement of the dynamic pressure, thestatic pressure, and (for compressible flow only) the temperature rise in the airflow

§ direction of airflow around a model can be determined by tufts of yarn attached to the aerodynamic surfaces

§ direction of airflow approaching an aerodynamic surface can be visualized by mounting threads in the airflow ahead of and aft of the test model

§ dye, smoke, or bubbles of liquid can be introduced into the airflow upstream of the test model, and their path around the model can be photographed (see particle image velocimetry)

§ pressures on the test model are usually measured with beam balances, connected to the test model with beams or strings or cables

§ pressure distributions across the test model have historically been measured by drilling many small holes along the airflow path, and using multi-tube manometers to measure the pressure at each hole

§ pressure distributions can more conveniently be measured by the use of pressure-sensitive paint, in which higher local pressure is indicated by lowered fluorescence of the paint at that point

§ pressure distributions can also be conveniently measured by the use of pressure-sensitive pressure belts, a recent development in which multiple ultra-miniaturized pressure sensor modules are integrated into a flexible strip. The strip is attached to the aerodynamic surface with tape, and it sends signals depicting the pressure distribution along its surface.

§ pressure distributions on a test model can also be determined by performing a wake survey, in which either a single pitot tube is used to obtain multiple readings downstream of the test model, or a multiple-tube manometer is mounted downstream and all its readings are taken (often by photograph).

Flow visualization

In experimental fluid dynamics, flows are visualized by three methods:

§ Surface flow visualization: This reveals the flow streamlines in the limit as a solid surface is approached. Colored oil applied to the surface of a wind tunnel model provides one example (the oil responds to the surface shear stress and forms a pattern).

§ Particle tracer methods: Particles, such as smoke, can be added to a flow to trace the fluid motion. We can illuminate the particles with a sheet of laser light in order to visualize a slice of a complicated fluid flow pattern. Assuming that the particles faithfully follow the streamlines of the flow, we can not only visualize the flow but also measure its velocity using the particle image velocimetry or particle tracking velocimetry methods.

§ Optical methods: Some flows reveal their patterns by way of changes in their optical refractive index. These are visualized by optical methods known as the shadowgraph, schlieren photography, and interferometer. More directly, dyes can be added to (usually liquid) flows to measure concentrations; typically employing the light attenuation or laser-induced fluorescence techniques

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.

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

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

Never Get Exhausted

3 Dec 2011

Web Technology Materials ~ Never Get Exhausted

26 Nov 2011

Gandhi Nagar Matriculation Higher Secondary School, Tiruvannamalai

20 Nov 2011

New Tamil Promo Song

Dynamic IP allocation

12 Nov 2011

Automobile books download

Google Tilt

7 Nov 2011

Vehicle body Engineering by pawloski

Unit V Body materials, Trim and Mechanisms

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