1.4 WORKING OF A VEHICLE

The basic working of a vehicle may be described as discussed in the following steps:

1). Cranking of vehicle. 
The driver turns the ignition key, and the battery supplies the current to the starter motor. The starter motor turns the flywheel and the crankshaft, which are interconnected.

2). Starting of engine. 
As the crankshaft is rotated, air-fuel mixture is drawn into the cylinder and is compressed by the piston. Then, the spark plug ignites this mixture and the pressure that is subsequently generated during combustion drives the piston towards the bottom of the cylinder The motion of the piston is transferred to the crankshaft, causing it to rotate. This action is repeated over and over again which results in engine running continuously.

3). Transmission of engine power to wheels.
The driver presses the clutch, which connects the crankshaft to the transmission. The driver shifts the gear shift lever into the suitable gear (i.e. from neutral to low speed gear) and the power is transmitted to the wheels. When the wheel is rotated, it pushes back the earth and the reaction being equal and opposite in direction, the vehicle starts moving forward. The pushing force or the driving thrust is subject to the turning moment or the torque applied at the wheels. The greater the torque at the wheels, greater is the driving thrust and faster speeds can be achieved in the minimum time. The speed of the vehicle after the start is controlled by means of accelerator. In order to maintain higher speed, shift from lower gear to higher gears is required.

The gears are stepped down while climbing a hill, negotiating a turn, or going through a muddy road, as at this time, higher torque is required at the wheels.
( In case of vehicles with automatic transmission, the driver pushes the gear shift lever in drive range for operation. The clutch operation and gear selection are done automatically.)

4). Turning of vehicle. 
In order to take a turn, the driver turns the steering wheel. This turning of steering wheel is transferred to the wheels and the left and right wheels turn at suitable angles. Also, the differential mechanism allows one wheel to turn faster than the other which is necessary for taking a turn.

5). Braking of vehicle. 
When it is required to stop the vehicle, the driver presses the brake pedal. The flow ofpower to the wheels is discontinued and the vehicle slows down or stops.