The gearbox is an important part of the transmission system that transmits the torque generated by the engine to the wheels by varying the speed and torque ratio and direction depending on the condition of the vehicle. Gearboxes have a system that combines different types of gears.


Function of the gearbox in the transmission system
1. Engine torque, speed and direction transferred to the wheels vary according to the resistance felt against the vehicle's movement.
2. Neutral condition is important so that there is no contact between the engine and the wheels when the engine is running and the clutch is engaged.
3. Helps to change the direction of the vehicle (reverse).

Tractive Force
The force moving from the engine to the wheel causes the vehicle to move parallel to the track, this force is called the traction force.
The torque experienced on the wheel is equal to the product of the gear ratios in the gearbox and the final drive.
Te = n1 x n2 x T
Te -> Torque Act on Wheel, n1 -> Gear Box ratio, n2 -> Final Drive ratio, T -> Engine Torque
Tractive Effort, F = Te / r (r -> Tire Radius)

Tractive effort is used to overcome the resistance felt against the movement of the vehicle and to move it forward.

The defenses against the movement of the vehicle are:

1. Wind resistance.
2. Gradient resistance.
3. Rolling resistance.

 


Wind resistance.

Wind resistance (or air resistance) is the force exerted by air on a vehicle against the forward motion of the vehicle. Resistance varies according to the size, shape, speed and wind speed of the vehicle.

Gradient resistance.

This is the resistance that the vehicle experiences when climbing. Such resistance is constant at all speeds of the vehicle. Resistance varies according to the slope of the road and the vehicle load.

Rolling resistance

This is the resistance between the tires of the moving vehicle and the road surface. These resistances vary depending on the nature of the tire and the road.

Different types of gearboxes

Various types of gearboxes, both manual and automatic, are used in automobiles today.
The most common types of gearboxes used in vehicles are the selective type, the progressive type, the epicyclic type (automatic) and the semi-automatic.