brakes ppt

BRAKING SYSTEM

PURPOSE OF BRAKING SYSTEM

Stop the vehicle by converting kinetic energy to heat energy.

Heat energy is created in the brakes by friction.

Friction is created between a moving and non- moving surface at each wheel to generate the heat.

Discs and drum brakes are the most common type of braking system used.

Braking System ComponentsPedal armPush rodMaster cylinderBrake liningsproportioning valvesPressure valvesMetering valvesT joint flexible liningCalipers

BRAKING SYSTEM

Braking fundamentals

Braking Systems

Braking system components

Drum brakes & components

Disc brakes & components

Antilock braking system & components

Braking procedures

BRAKING FUNDAMENTALS

PRINCIPLE: Friction between braking surfaces converts kinetic energy into heat.In drum brakes, wheel cylinders force brake linings against the inside of the drum.In disc brakes, pads are forced against a brake disc.

Several factors can influence Vehicle Braking: Road surface Road conditions Weight of the vehicle Load on the wheels during stopping How the vehicle is being driven.

A basic Braking system has a: Brake pedal Master cylinder to provide hydraulic pressure Brake linings and hoses to connect the master cylinder to the brake assemblies Brake assemblies – Drum or Disc that stop the wheels.

DRUM & DISC BRAKES:Drum brakes have a brake shoe that expands against the inside of a drum.Disc brakes clamp a flat disc between two pads.

COEFFICIENT OF FRICTION:The coefficient of friction is the measurement of friction between pairs of surfaces.

STOPPING DISTANCE: The distance in which the vehicle stops by applying force.

BRAKE FADE: It is the reduction in stopping power caused by a build up of heat in the braking surfaces.

WEIGHT TRANSFER:In dynamic braking condition weight transfers from rear wheels to front wheels

SKIDDING:When force of braking exceeds force of adhesion between tires and road

Drum brakeDrum brakes have a drum

attached to the wheel hub and braking occurs by means of brake shoes, expanding against the inside of the drum.

A drum brake is a brake in which the friction is caused by a set of shoes or pads that press against the inner surface of a rotating drum. The drum is connected to a rotating wheel.

DISC BRAKE With disc brakes, a disc attached to

the wheel hub may be clamped between 2 brake pads.

On light vehicles, both of these systems are hydraulically operated. The brake pedal operates a master cylinder. Hydraulic lines and hoses connect the master cylinder to brake cylinders at the wheels.

Most modern light vehicles have either disc brakes on the front wheels and drum brakes on the rear, or disc brakes on all 4 wheels.

Disc brakes require greater forces to operate them. A brake booster assists the driver by increasing the force applied to the master cylinder when the brake is operated.

DISC BRAKE DRUM BRAKEBetter ventilation property than drum brake.

Low ventilation property.

Uniform wear of frictional force between pads and disc.

Non uniform wear of frictional force.

Design of disc brake is easy.

It has complex design.

Disc brake have low weight.

20% more weight than disc.

It has better anti - fade characteristics.

It has poor anti – fade characteristics.

Replacing of frictional pads is easily.

Replacing of frictional pads is difficult.

Total frictional area of pads on disc is less .

Total frictional area of pads in drum are more compare to disc.

Antilock braking system (ABS)

ABS is a system on motor vehicles which prevents the wheels from locking while braking.The purpose of ABS is:To allow the driver to maintain steering controlTo shorten braking distancesA typical ABS is composed of:A central electric unitFour wheel speed sensors (one for each wheel)Two or more hydraulic valves on the brake circuitThe electronic unit constantly monitors the rotation speed of each wheel. When it senses that one or more wheels is rotating slower than the others, it moves the valves to decrease the pressure on the braking circuit, effectively reducing the braking force on that wheel.

ADVANTAGE OF ABS

It can be used for reducing the stopping distance. It enables to steer when brakes are firmly applied. It allows braking firmly on surface with different level of grips. It can review and adjust the deriver’s driving.

DISADVANTAGE OF ABS

Driver may takes more risks when driving with vehicles fitted with ABS. people who are inexperienced in using ABS may respond inappropriately when they activate the system.

HYDRAULIC BRAKES

The principle of hydraulic brakes based on the Pascal’s law.

The function of all the components of hydraulic brakes:Master cylinder: Distribution of fluid in the pipe lines.

Calipers:Calipers are used to stop the vehicle by applying clamping force with brake pads to rotating disc. FLEXIBLE LINING

ROTOR with CALIPER BENZO BOLT DRUM BRAKE

DOTs 3 DOTs 4 DOTs 5

Less viscous as compare to other.

It has moderate viscosity.

Highly viscous as compare to other.

Air bubble formation is high.

Air bubble formation is less.

No chances of air bubble formation in pipelines.

Boiling point is 401 degree Fahrenheit.

Boiling point is 446 degree Fahrenheit.

Boiling point is 500 degree Fahrenheit.

FLUIDS There are three types of fluid using in hydraulic brake system.

Types of BRAKES

Purpose Primary brakes Secondary brakes Actuation

Mechanical brakesExhaust brakesVacuum brakesAir brakesHydraulic brakes

PositionInboard brakesOutboard brakes

ConstructionDisc brakesDrum brakes

Parking BrakeThe primary components of the park brake system are: Parking brake cablesDisc brake caliper fitted with park brakePark brake lever on drum brakes.The mechanical park brake is normally hand operated by a brake handle located on the wheels floor or under the dash. In either position, it is in easy reach for the driver to apply.

On vehicles fitted with 4 wheel disc brakes, the park brake is applied at the rear caliper by the cable-operated system.

LAYOUTS OF BRAKES ASSEMBLY Brakes are bedded in two types mainly.

Diagonally split Rear – Rear and Front - Front

ADVANTAGE OF DAIGONALY SPLIT OVER THE OTHER BRAKES LAYOUT:It helps to safe the one circuit of vehicle using tandem master cylinder if one lining is failed.

MASTER CYLINDER

The single-piston master cylinder transforms the applied pedal force into an hydraulic pressure which is transmitted simultaneously to all four wheels.

The master cylinder is connected to the brake pedal via a pushrod.

The rod from the brake pedal pushes on the piston. It moves, closing off the compensating port and trapping fluid ahead of the primary cup. Any fluid trapped in the cylinder is then forced through a valve called a residual pressure valve, into the brake lines.

TANDEM MASTER CYLINDER The tandem master cylinder

transforms applied brake force into hydraulic pressure which is transferred to the wheel units through two separate circuits. This provides residual braking in the event of fluid loss.

When the brake is applied, the primary piston moves and closes its compensating port. Fluid pressure rises, and acts on the secondary piston. It moves, closes its compensating port. Pressure builds up in this circuit. Both pistons then move and displace fluid into their separate circuits and apply the brakes.

COMBINATION VALVES

Metering valve

Pressure differential valve

Proportioning valve

BLEEDING

It means removal of air bubble present in the pipelines. The air bubble block the transfer of pressure from calliper to master cylinder. Bleeding in four Bleeding in two wheeler wheeler NEW TECHNOLOGYAccording to new technology singleMan can do the bleeding using theseMaterials.

Single person bleeding process