13-12-2012, 06:46 PM
BRAKES
BRAKES.pptx (Size: 3.54 MB / Downloads: 44)
BRAKING SYSTEM
A BRAKE is a device which inhibits motion.
BRAKING is the mechanism in the motor vehicle which is used to slowing down and stopping the vehicle to rest in the shortest possible distance.
STOPPING DISTANCE
STOPPING DISTANCE depends upon
Grip between the tyre and road surface.
Tyre tread condition.
Tyre inflation.
Nature of road surface.
Stopping Distance [D] = kV2
Where; k – constant depending upon the road and tyre inflation.(1/25 for 4 wheel & 1/12 for 2 wheel)
v – velocity of vehicle per hour.
HISTORY OF BRAKES
1902 - Disc brakes were first used.
1918 - MALCOLM LOUGHEAD invented 4- wheel hydraulic brake systems.
1929 - 4-wheel hydraulic braking system were standard equipment on most high priced cars.
Early 1950’s - CHRYSLER widely introduced the disc brake.
1964 - Disc brake was reintroduced by automaker Studebaker.
1969 – Ford uses ABS technology in cars. They were placed in THUNDERBIRD & CONTINENTAL MARK III.
PRINCIPLE
Most commonly brakes use friction to convert kinetic energy into heat energy, though other methods of energy conversion may be employed.
Since kinetic energy increases quadratically with velocity (K = mv2 / 2), an object traveling at 10 kilometers per second has 100 times more energy than one traveling at 1 kilometer per second, and consequently the theoretical braking distance, when braking at the traction limit, is 100 times as long.
In practice, fast vehicles usually have significant air drag, and energy lost to air drag rises quickly with speed.
CHARACTERISTICS OF BRAKES
Peak Force - The peak force is the maximum decelerating effect that can be obtained.
Continuous Power Dissipation - Brakes typically get hot in use, and fail when the temperature gets too high. The greatest amount of power that can be dissipated through the brake without failure.
Fade - As a brake heats, it may become less effective, called brake fade.
Power - Brakes are often described as "powerful" when a small human application force leads to a braking force that is higher than typical for other brakes in the same class.