This document discusses different types of automobiles classified based on purpose, weight, fuel used, capacity, number of wheels, and driver seat location. It describes the key parts of a bullock cart including the frame, wheels/axle, yoke, body/superstructure, and how they are divided. Vehicle chassis are classified based on engine fitting location and number/driving wheels. Desirable chassis characteristics and components such as the frame, suspension, steering, braking and powertrain systems are outlined. Finally, the aerodynamic forces acting on vehicles and their causes are summarized.

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
•