Basics of Automobile Engineering

Basics of Automobile Engineering

Basics of Automobile Engineering( only for reference purpose only)Basic Structure

Chassis

Transmission of PowerIt is the mechanism through which the driving torque of the engine is transmitted to the driving wheel of the vehicle. The transmission is a sort of speed and power changing device needed between the engine of the automobile and the driving wheels. It provides the means of varying the gear ratio between the engine and rear wheels.

Power TransmissionA transmission system includes whole of the mechanism required to transfer torque from the engine flywheel to rear road wheel, i.e. the clutch, gear box, propeller shaft, final drive, differential and axle shafts. The purposes of transmission are as under:It enables the engine to be disconnected from the driving wheels.It enables the running engine to be connected to the driving wheel smoothly and without shock.It enables the leverage between the engine and the driving wheels to be varied.

1. ClutchA clutch is a mechanism which connects or disconnects the transmission of power from one working part to another, i.e. the crankshaft and the gear-box primary shaft. Functions of a clutch:To permit engagement or disengagement of a gear when the vehicle is stationary and the engine is running.To transmit the engine power to the road wheels smoothly without shock to the transmission system while setting the vehicle in motion.To permit the engaging of the gears when the vehicle is in motion without damaging the gear wheels.

Single plate clutch

It is the most common type of clutch used in motor vehicles. It consists of only one clutch plate, mounted on the spines of the clutch shaft. The fly wheel is mounted on the engine crane shaft and rotates witch it. The pressure plate is bolted to the fly wheel through clutch springs, and is free to slide on the clutch shaft when the clutch pedal is operated.

2. GearboxAn IC engine produces little power at low rpm and maximum power at the given speed depending on the particular engine. With direct coupling, a set or fixed road speed is provided to the engine by this. But this would only be suitable on level ground, because when climbing the vehicle has to be lifted as well as propelled on slight gradient.

The accelerator could help to overcome this on level ground but on steep gradient even at full throttle the engine speed would rapidly decrease and finally stop. In order to maintain engine speed on all conditions of load and vehicle speed, the gear-box uses a system of leverage for keeping the speed of the engine up while sacrificing some road speed.

In this case, gear wheels on the main shaft and lay shafts are constantly engaged and the rotary motion is transmitted to the main shaft by engaging dog clutches.Constant Mesh GearboxI speed gear II speed gear main shaft III speed gear top and III speed engaging dogs top gear primary shaft or main drive gear counter shaft/cluster gear

3. Universal jointsIn order to make a flexible connection between two rigid shafts at an angle with each other varying constantly, universal joints are used. Due to the action of the road springs, position of the rear axle is varied and allowance should be made in it when the gear box is coupled to the rear axle by the propeller shaft. Therefore, for connecting two shafts inclined to one another at an angle as well as for transmitting the rotary motion from the engine to the road wheels throughout the, universal joints are used.

4. Propeller ShaftThe propeller shaft is a driving shaft for connecting the transmission output shaft to the differential at the rear axles. It also carries the rotary motion of the transmission output shaft to the differential for rotating rear wheels. The propeller shaft needs to transmit power between two points at varying vertical and horizontal distances from each other. This is handled by using two universal joints at the two ends of the propeller shaft.

5. DifferentialNecessity of Differential: When the vehicle is taking a turn, the outer wheels will have to travel greater distance as compared to the inner wheels in the same time. If therefore, the vehicle has as a solid rear axle only, there will be tendency for the wheels to skid. Hence if the wheel skidding is to be avoided, some mechanism should be provided in the drive axle. The Mechanism which reduces the speed of inner wheels and increases the speed of outer wheels when taking turn and while running straight it keeps the speeds of all the wheels same in known as differential mechanism.