AE Lecture1

8/11/2019 AE Lecture1

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Automobile EngineeringAmrita School of Engineering

Bangalore



Classification of Automobiles

1) Use

2) Capacity a) LTV b)HTV

3) Make and model

4) Fuel used

5) Body style

6) Wheels

7) Drive a) left hand drive b) right hand drive

a) front wheel drive b) rear wheel drive

c) all wheel drive

8) Transmission



Components of an Automobile

1. The Basic Structure2. The Power plant

3. The transmission system

4. The auxiliaries5. The controls

6. The super structure



Classification of Automobiles

1) Use

2) Capacity a) LTV b)HTV

3) Make and model

4) Fuel used

5) Body style

6) Wheels

7) Drive a) left hand drive b) right hand drive

a) front wheel drive b) rear wheel drive

c) all wheel drive

8) Transmission



Components of Chassis1. Engine

2. Radiator

3. Clutch

4. Gearbox

5. Universal joints cum propeller shaft6. Final drive

7. Differential

8. Half axle drive shafts9. Frame

10. Springs and wheels



11. Special dampers

12. Electrical System

13. Controls

14. Steering system

15. Brake system16. Engine control

17. Power train control



Engine : Produces power required to move the

vehicle at desired speed overcoming the

external resistances.Radiator: used to recool the hot engine cooling

water for recirculation purpose. Other parts of

cooling system are fan, fan belt drive, watercirculating pump.

Clutch: Helps to isolate the engine from the

transmission system as and when required.Also permits the vehicle to be started from rest

smoothly with out jerks.



Gearbox: provides the torque of the requiredamount at the driving road wheels.

Also helps to reverse the vehicle.Universal joints cum propeller shaft: transmits

torque from the gearbox shaft to the final

drive.The universal joints help the propeller shaft to

assume different inclinations.

The propeller shaft has a sliding arrangementwithin itself which helps the shaft to havedifferent lengths when shaft assumes differentinclinations.



Final drive: transmits the torque from thelongitudinal universal joints cum propeller

shaft to the transverse driving half axle shaftsand wheels.

It also multiplies the driving torque.

Differential: allows the driving wheels on thetwo sides of the vehicle to rotate at the sameand different speeds when ever required.

Half axle drive shafts: transmit the driving

torque from the final drive and differential unitto the driving road wheels.



Frame: supports engine, vehicle body, wheels and

other components.

Springs and wheels: transmit the vehicle load from

the frame to the road. Also damp jerks and shocks

when the vehicle wheel hits bumps in the road.

Special dampers: dampens the resultant oscillations

of the springs.

Electrical system: includes a battery, starting motor,

generator/alternator, and controls, and in the caseof SI engines (ignition coil, distributor, spark

plugs and wires) and lighting arrangement.



Controls: includes steering system, brake system,

engine control and power train control.

Steering system: is used to change the direction

of motion of the vehicle by turning the front

wheels. The front wheels are linked to the

steering wheel which is operated by the driver,

by a system of levers and rods.

Brake system: ensures safe driving of the

vehicle, used to stop or slow down the vehiclewhenever required.



Engine Control: refers to the mechanism which

permits a variation in the revolutions of the

engine crankshaft in accordance with demands.

In a vehicle this refers to the accelerator pedal

and the connected system.

Power train control: helps to engaging and

disengaging the clutch and the gearbox. These

controls, thereby make the speed and torque

variation possible.



FrameThe frame of a motor vehicle is the foundation on which

the power plant and body are carried, and which inturn is supported on the road wheels through the axles

and springs.

The engine, wheels, power train, brakes and steering

systems when installed on the frame, the assembly is

called chassis.



Functions of Frame

Functions: It takes up the engine and transmission thrust.

It takes up the torque stresses.

It supports the weight of the body and passengers/ goods. It acts as a base for mounting engine and transmission

units.

It accommodates the spring system

It acts as a base for mounting the body, fuel tank units etc.



Transmission System

Consists of clutch, a gear box, giving 3-5

different gear ratios of torque output to torque

input, a propeller shaft to transmit the torque

output from the gear box to the rear axle and a

differential gear to distribute the final torqueequally between the driving wheels.



Functions of Transmission system

1. To disconnect the engine from the road wheelswhen desired.

2. To connect the engine to the driving wheelswithout shock.

3. To vary the leverage between the engine and thedriving wheels.

4. To reduce the engine speed permanently in afixed ratio.

5. To turn the drive through a right angle.

6. To make provisions such that the driving wheelsmay rotate at different speeds while taking turns.



Body

In vehicle design and development three factorsare of equal importance:

Operational reliability

Quality of the vehicleDriver and passenger environment



Importance of Vehicle body design are

as follows:• Body contributes about 40% of total weight of

a car and about 60 to 70% of total weight of

buses. Since gross weight is limited by tyres

and other components, hence reduction in

body weight is important.

• Reduction in body weight also improves

capacity and fuel economy.

• Aerodynamic characteristics determine the fuel

consumption at high speeds and stability in

cross winds.



• The positive pressure on the front of vehicle

should be minimized and it should be deflected

smoothly to prevent the creation of eddies.

• Main customer appeal of style should also be

considered.



Requirements for vehicle body structure

1. It must be lighter.

2. It must be so designed that the stresses induced may

be uniform and be with in limits.

3. Must have reasonable fatigue life.

4. Must have sufficient stiffness to ensure minimum

deformations around openings.

5. Must ensure quite ride, easy entry and exit.

6. Must have reasonable overall dimensions withsufficient inside capacity and good access to the

engine and suspension elements.



Contd:

7. Should not have too many and complicated

components.

8. Must be so designed to allow for the

possibility of modifications at a later date.



Components of Vehicle body

Structure – All load carrying elements are

defined as the body structure.

Finish – The finish group includes all unstressed

units, eg: bonnet, bumper etc.

Equipment- the equipment group includes such

things as rim, seats, heating systems and doors.



Vehicle Layout

• Vehicle layout should take into account the

following aspects:

1. Driver comfort

2. Passenger comfort

3. Best vehicle performance

Drivers seat position in relation to the steering

wheel, foot controls and other secondary controls

is important.

It influences drivers comfort and on road safety.

It should be adjustable 45mm horizontally and 30

mm vertically.



Passenger seats can be arranged to give a more

reclining position than that used for the driver.

Comfortable entry and exit of the driver and passengers into the vehicle should be ensured.



Aerodynamics

Three forces acting on a vehicle are

1. Force of air drag in the direction of vehicle

motion (with the wind acting along the

longitudinal direction axis), Px

2. Aerodynamic lift acting vertically upward, Pz

3. Cross wind force in the lateral direction, on

the side of the vehicle, Py

.



These forces are acting at the centre of pressure

and not at the centre of gravity of the vehicle.

Hence these forces cause moments as follows:

My – Pitching moment caused by force Pz and

Px about y axis.

Mz – yawing moment caused by the force Py

about z axis

Mx - Rolling moment caused by the force Py

about x- axis.



Aerodynamic Drag

• Aero means air, dynamic means motion.

Aerodynamic is therefore the behavior of air

in motion relative to the vehicle body.

• It is also called as air resistance.

• It includes many factors such as profile

drag(57% of total drag), included drag(8%),

skin friction(10%), interference drag(15%) and

cooling and ventilation system drag (10%).

Measures to reduce Aerodynamic



Measures to reduce Aerodynamic

drag Careful selection of body profile.

Stream lines of air flow around the vehicle

should be continuous and separation of the

boundary layer with its attendant vortices

should be avoided.

Smooth, well polished body surfaces reduces

skin friction drag.

Elements such as door handles, mirrors, aerials

and badges which project out of the normal

surface of the vehicle body introduce

interferece drag and hence should be avoided.



Aerodynamic Lift1. It is the vertical component of the resultant

force caused by the pressure distribution onthe vehicle body.

2. Aerodynamic lift and pitching moment have

undesirable effects.3. The aerodynamic lift will tend to reduce the

pressure between the tyres and the ground.

4. Which causes loss of steering on the frontaxle and loss of traction on the rear axle.

5. It makes the rear wheels lift off the ground

and further reduces the available traction.



Side Force

The side force Py is formed by the asymmetric

flow of air round the vehicle body. This force

also acts at the centre of pressure and creates

moments about the centre of gravity - yawing

moment Mz about Z axis and a rolling momentMx about X axis.



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AE Lecture1