Factors controlling the stop of an automobile

1.13. Factors controlling the stop of an automobile

The following factors control the stop of an automobile

1.13.1. Speed and load:

Lesser the speed and lesser the load, the less energy shall be absorbed to stop the vehicle as the brakes convert energy of motion into heat.

The higher the speed and more the load, the more energy shall be absorbed for stopping a vehicle.

1.13.2. Road surface:

The coefficient of friction between the road and tyre is affected by the -nature of road. If the road is slippery, the vehicle shall stop at a greater distance than if the road is dry.

1.13.3. Tyre treads:

A good tyre tread has good holding ability. It provides a greater coefficient of friction than a smooth tyre.

1.13.4. Gradient:

When a vehicle is going up a gradient or hill, the gravitational force assists in stopping the movement of the vehicle. If the vehicle is going down a gradient or hill, the force of gravity tends to keep the vehicle moving and hence a greater braking force is required to overcome its movement.

1.13.5. Number of wheels braking:

For getting maximum braking effort, all the wheels should be equipped with brakes. If any of the wheels is not equipped with brakes the time and distances of stopping the vehicle shall increase.

1.13.6. Coefficient of friction of braking surfaces:

The ability to hold a moving wheel is controlled by the coefficient of friction between the brake lining and brake drum. If the linkages are glazed with oil or grease they will tend the brake drums to slip as the coefficient of friction is lowered down.

1.13.7. Braking force of engine:

The engine is also used as a brake when going down a hill. The braking effect of the engine is more in lower gear speed than in direct drive.

1.13.8. Pressure applied through energization:

More the self -energizing ability of the brake shoe, better the braking effect.

1.13.9. Weight transfer:

On application of brakes, there is a natural transfer of weight from the rear wheels to the front wheels caused by the tendency of the mass to continue in its forward motion.

The greater the deceleration, the greater is the load or weight transfer from rear to front wheels.

During the stop, the weight holding the rear wheels to the road is lessened while the weight on the front wheel is increased by exactly the same amount. It is due to this fact that brakes are designed so that applied effort is greater on front wheels than on the rear.