Power transmission to the wheels
There are different arrangements of power transmission by which engine power is transmitted to the wheels. The usual arrangements and the variations in the arrangements are explained in detail below.
1. Front engine – rear wheel drive
Most of the vehicles are having this arrangement. In this case the engine power is transmitted to the vehicle rear wheels through the clutch, gear box, propeller shaft, differential and rear axle. The main advantages are better cooling is achieved, since steering and drive are independent, it is easy for construction and vehicle controlling is easy. With this arrangement, a uniform load distribution can be assured between the axles, but a long universal joint shaft is required. Because of the propeller shaft floor level will be increased, thereby the centre of gravity increases and the vehicle stability is poor.
2. Front engine – front wheel drive
Most of the modern cars are having this arrangement. In this case, the engine power is transmitted to the front wheels through the clutch, gear box, differential and short axle shafts. With this arrangement, a more compact transmission is obtained because the universal joint long propeller shaft drive is no longer necessary and the clutch and the gearbox are combined with the driving axle. The other advantages are: better cooling is achieved, better vehicle control, since the centre of gravity will be lowered resulting in more stability. However, it is difficult to provide both steering and power drive.
3. Rear engine-rear wheel drive
Some cars do have this arrangement. In this case, the engine power is transmitted to the rear wheels through the clutch, gear box, differential and short axle shafts. With this arrangement, outlet of exhaust is easy, streamlined motion is achieved in the front. This arrangement allows a better view of the road and reliably separates the engine from the passengers. This aspect reduces the noise and penetration of the exhaust gases into the saloon. The main difficulty of this layout is the complicated control of the engine, gearbox and clutch, since they are positioned far from the driver.
Besides, with this layout, the driver and the front passenger sit near the front of the vehicle and in the case of collision or striking an obstacle they may be severely injured. Further engine cooling becomes a problem. Less stability especially when the vehicle moves along a gradient.
4. Four Wheel drive
Some of the cross country vehicles have this arrangement. In this case, the engine power is transmitted to all the four wheels of the vehicle. The main advantage of this arrangement is the entire vehicle weight is available for traction. This arrangement however involves additional cost.