VEHICLE STRUCTURE AND ENGINES

1. UNIT I
VEHICLE STRUCTURE AND ENGINES

2. TYPES OF AUTOMOBILES
• (i) with respect to the purpose
• (a) Passenger vehicles. Ex. Car, bus, jeep, scooter, mopeds and
motor cycles
• (b) Goods carriers: ex. Trucks and lorries
• (ii) weight of the vehicles:
• - Heavy weight vehicle- buses, trucks and trailers
• - Light weight vehicles - cars, jeeps
• - Medium weigh vehicles – minibus and station wagon
• (iii) With respect to the fuel:
• - Petrol vehicles – scooters, cars motors cycles
• - Diesel vehicles - Buses , trucks
• Gas vehicles – Coal gas, LPG, CNG vehicles
• Electric vehicle – Heavy cranes, battery truck, cars and fork lifts

3. • (iv) with respect to capacity:
• Heavy transport vehicles – Bus lorries, trucks, tractors
• Light transport vehicles _ Car, scooter, mopeds, motor
cycles, jeeps
• (v) with respect to number of wheels:
• Two wheelers – Scooters, mopeds
• Four wheelers – car, jeep, buses, truckes
• Three wheelers – Auto, tempos
• Six wheelers - heavy trucks
• (vi) With respect to side of driver seat
• - Left hand drive- American, European and UAE
• -Right hand drive – Indian vehicles

4. • Bullock cart consists of
• (i) Frame (ii) wheels & axle
• (iii) Yoke (iv) Body or superstructure and
platform
• These pars can be divided into two main
portions
• (i) Machine portion (ii)carriage portion

6. • Classification of chassis:
 According to the fitting of engine:
- Full-forward – ex cars, mahindra jeeps
-semi- forward – Tata Se series of vehicles
- Bus chassis – Busses and trucks
- Engine at back- Volkswagen cars, Leyland bus of
England.
- Engine at centre- Royal tiger world master buses of
Delhi transport.
 According to the number of wheels fitted in the vehicles
and number of driving wheels:

7. • Characteristics of a good chassis:
• Fast pickup, strength, safety, durability,
dependability, ease of control, quietness, speed,
power accessibility, economy of operation low
centre of gravity stability load clearance, braking
ability, simplicity of lubrication.
• Chassis Components: Frame, suspension systems
• steering system, braking system, internal
combustion engine, clutch, gear box , propeller
shaft, universal joint ,differential, springs

12. • VEHICLE AERODYNAMICS:
• Resistance to vehicle motion:
• 1.Air resistance or aerodynamic drag:
• A vehicle travelling at a particular speed in air encounters a force
resisting its motion.
• A) Size of the vehicle (b) shape of the vehicle
• C) Speed of the vehicle (d) wind velocity
• 2. Gradient resistance: component of the vehicle weight which is
parallel to the plane of the road.
• 3. Rolling resistance: of tyres on hard surfaces is due to hysteresis
in the tyre material.
 Tyre rolling resistance
 Road rolling resistance
 Resistance due to tyre slip angle
 Resistance due to bearing friction and residual braking

13. • Aerodynamics of Automobile body:
• Various aerodynamic force acting on the vehicle.
• (i) Drag force (Fx): Force of air drag is acting in the
direction of vehicle motion with the wind acting along
the longitudinal direction axis.
• The main causes (i) shape drag (ii)Skin friction drag.
• (ii) Lift force(Fz):Aerodynamics lift force is the vertical
component of the resultant force caused by the
pressure distribution on the body.
• (iii) Cross wind force (Fy):It is acting in the lateral
direction on the side of the vehicle.
• These forces acting at the centre of pressure instead of
centre of gravity & various cause of moments

14. • (i)Pitching moment (My): is caused by the drag
force Fx or lift force Fz about Y axis. This
moment makes the rear wheels lift off from the
ground and further it reduces the available
traction.
• (ii) Yawing moment(Mz): Cross wind force Fy
about Z axis
• (iii) Rolling moment(Mx): Cross wind force Fy
about X axis
•