1. Braking System

2. Hydraulic Brakes Principle
 The brakes which are actuated by the hydraulic pressure (pressure of a fluid) are called hydraulic brakes. Hydraulic brakes are commonly used in the automobiles.
Principle
 Hydraulic brakes work on the principle of Pascal’s law which states that “pressure at a point in a fluid is equal in all directions in space”. According to this law when pressure is applied on a fluid it travels equally in all directions so that uniform braking action is applied on all four wheels.

3. Construction and Working of Hydraulic Brakes

4.  When brake pedal is pressed, the force is transmitted to the brake shoes through a liquid (link). The pedal force is multiplied and transmitted to all brake shoes by a force transmission system.
 The previous figure shows the system of hydraulic brake of a four wheeler automobile. It consists of a master cylinder, four wheel cylinders and pipes carrying a brake fluid from master cylinder to wheel cylinder.
 The master cylinder is connected to all the four-wheel cylinders by tubing or piping. All cylinders and tubes are fitted with a fluid which acts as a link to transmit pedal force from master cylinder to wheel cylinders.

5. Brake Fluid
 The fluid filled in the hydraulic brake system is known as brake fluid. It is a mixture of glycerin and alcohol or caster oil and some other additives.
 Master cylinder consists of a piston which is connected to peal through connecting rod. The wheel cylinder consists of two pistons between which fluid is filled.
 Each wheel brake consists of a cylinder brake drum. This drum is mounted on the inner side of wheel. The drum revolves with the wheel. Two brake shoes which are mounted inside the drum remain stationary. Heat and wear resistant brake linings are fitted on the surface of the brake shoes.

6. Application of Hydraulic Brakes
 When brake pedal is pressed to apply the brakes, the piston in the master cylinder forces the brake fluid. This increases the pressure of fluid. This pressure is transmitted in all the pipes and up to all wheel cylinders according to Pascal’s law.
 This increased pressure forces out the two pistons in the wheel cylinders. These pistons are connected to brake shoes. So, the brake shoes expand out against brake drums. Due to friction between brake linings and drum, wheels slow down and brakes are applied.

7. Release of Brakes
 When pedal is released, the piston of master cylinder returns to its original position due to retractor spring provided in master cylinder. Thus, fluid pressure drops to original value. The retractor spring provided in the wheel cylinders pulls the brake shoes and contact between drum and brake linings is broken. Therefore, brakes are released.

8. Advantages Dis- Advantage  Equal braking action on all wheels.
 Increased braking force.
 Simple in construction.
 Low wear rate of brake linings.
 Flexibility of brake linings.
 Increased mechanical advantage.
Dis- Advantage
 Whole braking system fails due to leakage of fluid from brake linings.
 Presence of air inside the tubings ruins the whole system.

9. Master Cylinder

10. Wheel Cylinder

11. Brake Positioning of Car With No ABS

12. Brake Positioning of Car with ABS

13. Mechanical Brakes: Types of Mechanical Brake:
 Drum Brakes (Internal Expanding or External Contracting)
 Disc Brakes (Single or Two caliper)

14. Drum Brakes: Brake drum Back plate Brake shoes Brake Liners
 Construction: The main components of drum brakes are
Brake drum
Back plate
Brake shoes
Brake Liners
Returning Springs
Cam
Brake Linkages

15.  In this system the wheel is attached to drum
 In this system the wheel is attached to drum. There are brake shoes used to contact the rotating drum for braking operation. The shoes provide lining on their outer surface.
 The cam is used to lift the brake shoes at one end, other end is connected by some method so as to make as the brake sleeve come into contact in the brake drum.
 The returning spring is provided for bringing the brake shoes back to its original position, after releasing the brake pedal. All these parts are fitted in the back plate and enclosed with brake drum

17. Cam-operated Drum-brakes
 Initially almost all the drum-brakes were cam-operated. The cam is used to force the shoes against the drum. Foot-brake shoe- expanders for cars are now mostly hydraulically operated. Today the cam-operated expander is only used in large trucks, and particularly in articulated trailers. However, cams are preferred in parking-brake mechanisms in both drum and disc layouts.
 The disc-type cams use a plate in the cam-type brake-shoe expander. The plate rotates about an axis perpendicular to its plane. The profile of the plate provides a reciprocating motion to its follower, the shoe, which bears against the cam edge.

18.  The shoe-expander provides a suitable force ratio between the input effort and the output brake-shoe load. During initial period of braking, only the tension of the pull-off springs and friction in the mechanism are required to be overcome, hence a low force ratio is needed. But when the shoes are actually pressing hard against the drum and further braking is necessary, a progressively increasing force ratio is necessary. These requirements are met through variable-movement ratio cams.

19. Working:
 When the pedal is pressed the cam moves the shoes outwards through linkages, there by coming in frictional contact with the rotating drum. As soon as the brake pedal is released the retaining springs help the brake shoes to brought back and release the brakes.

20. DISC BRAKES: Construction:
 The discs are made of gray cast Iron. The brake pressure in case of disc brakes have to be much lighter than the drum brakes.
 It consists of rotating disc and two friction pads which are actuated by the four hydraulic wheel pistons contain in two halves of an assembly is called a caliper.
 The caliper assembly is secured to the steering knuckle in a front wheel brakes. The road wheel is fashioned to the outer surface of the disc. The friction pads rides freely on each side of the discs. They are in position being the hydraulic systems.

21. Different Parts of Disc Brakes

22. Different Parts of Disc Brake

30. Working :
 When the brakes is applied hydraulic pressure is supply to the fluid inlet tube, due to which the wheel cylinder piston force the friction pads against the rotating disc. In the released piston, the spring hold the piston pads so that they maintain contact with disc surface.

31. Advantage of Disc Brakes
 Main advantage of disc brakes is their resistance to wear as the discs remain cool even after repeated brake applications.
 Brake pads are easily replaceable.
 The condition of brake pads can be checked without much dismantling of brake system.
Disadvantage of Disc Brakes
 More force is needed be applied as the brakes are not self emerging.
 Pad wear is more.
 Hand brakes are not effective if disc brakes are used in rear wheels also. (Hand brakes are better with mechanical brakes).

32. POWER BRAKES The vacuum booster is a metal canister that contains a
 Back in the day, when most cars had drum brakes, power brakes were not really necessary -- drum brakes naturally provide some of their own power assist. Since most cars today have disc brakes, at least on the front wheels, they need power brakes. Without this device, a lot of drivers would have very tired legs.
 The Vacuum Booster
The vacuum booster is a metal canister that contains a
clever valve and a diaphragm. A center of the canister connects to
rod going through the the master
cylinder's other.
piston on one side and to the pedal linkage on the
Another key part of the power brakes is the check valve.

33. Vacuum Booster

34. Power Brake Diagram

35.  The vacuum booster is a very simple, elegant design
 The vacuum booster is a very simple, elegant design. The device needs a vacuum source to operate. In gasoline-powered cars, the engine provides a vacuum suitable for the boosters. In fact, if you hook a hose to a certain part of an engine, you can suck some of the air out of the container, producing a partial vacuum. Because diesel engines don't produce a vacuum, diesel-powered vehicles must use a separate vacuum pump.
 On cars with a vacuum booster, the brake pedal pushes a rod that passes through the booster into the master cylinder, actuating the master- cylinder piston. The engine creates a partial vacuum inside the vacuum booster on both sides of the diaphragm. When you hit the brake pedal, the rod cracks open a valve, allowing air to enter the booster on one side of the diaphragm while sealing off the vacuum. This increases pressure on that side of the diaphragm so that it helps to push the rod, which in turn pushes the piston in the master cylinder.
 As the brake pedal is released, the valve seals off the outside air supply while reopening the vacuum valve. This restores vacuum to both sides of the diaphragm, allowing everything to return to its original position.

36. Pneumatic (Air) Brakes

37. Air brake can better understand by the layout diagram as shown in figure. This system mainly consist a compressor, air filter, reservoir, valves and brake pads. The compressor takes air from atmosphere through an filter and compressed it. This compressed air sent to a reservoir through the unloader valve, which gets lifted or opened at a predetermined reservoir pressure. This air supply to brake chambers which is also called the diaphragm units situated at each wheel, through the brake valve. The brake valve is controlled by the driver who can control the intensity of braking according to the requirement. When the driver pushes the brake lever, pressure in the reservoir decreases which pushes the brakes pad toward types and apply brakes.  Advantage of air brake: 1. Air brake system are much more powerful than the ordinary mechanical or hydraulic brakes and that is the reason they are exclusively used in heavy vehicles They are easy to install on chassis because it is interconnected by pipes.

39. SERVO BRAKES applied comfortably by a driver to the
 If the force
applied
comfortably
by a driver
to the
footbrake is insufficient to retard the vehicle at the required rate, some form of assistance is necessary. The boosting force applied to supplement the driver’s effort is called servo assistance.
 In the past servo assistance was provided by rotation of the brake drum (self-servo) to keep the pedal force low. Today due to introduction of powerful disc brakes, the servo assistance is provided by either pneumatic or hydraulic means.
 In practice, vacuum assistance is added for medium cars, hydraulic assistance for heavy cars and vehicles fitted with anti-lock braking systems, and compressed-air assistance for some light trucks and minibuses.

40. Vacuum Assisted Servo
 This servo system is the most popular. The induction manifold depression of the spark ignition engine is used as source of servo energy in most systems. Since vacuum energy is not available at the manifold of a diesel engine, an engine-driven ‘vacuum’ pump (exhauster) in this case provides the required assistance.
 Vacuum servos in use today are called suspended-vacuum systems, because ‘vacuum conditions’ prevail on both sides of the servo piston during operation of the vehicle with the brakes off. When the brake is applied, outside air is bled in to the chamber on one side of the piston to create a pressure difference. This arrangement allows the servo to respond quickly in comparison to the older atmospheric suspended type system.

41. Indirect Servo System. Direct Servo System.
 In this older system, air is present on both sides of the piston and the air is ‘drawn out’ to provide assistance. The two main types of suspended-vacuum servos are the indirect and direct type.
 There are 2 types of Vacuum Assisted Servo
Indirect Servo System.
Direct Servo System.

42. Layout of A Servo System

43. Hydraulic Assisted Servo
 Since the pressure difference of a vacuum assisted servo arrangement is limited, a system to provide a much greater source of energy is necessary to stop a heavy motor car or light truck. This is achieved by incorporated a hydraulic servo, which operates on a pressure range of 5295 to 8842 kPa. The hydraulic power produced by the engine-driven pump of this system can also be used to provide for other servo needs, e.g. power-assisted steering, lifts etc.
 Figure below illustrates a continuous-flow hydraulic servo system. A multi-cylinder pump, driven from the engine or transmission, supplies fluid to the servo valve, mounted behind the conventional master cylinder. The brakes are in the ‘off position in the diagram, when the fluid can easily pass between the master-cylinder piston and servo valve to a drilling connecting the reservoir.

44. Tyres cushion provided with wheel.
• It consists of mainly the outer cover i.e. the tyre proper and the tube
inside.
• The tube assembly is mounted over the wheel rim.
• Air inside the tube that carries the entire load and provides the cushion.
• Deal with the worst possible forces, shocks and other parameters and also
absorb most of the shocks thus providing a smooth ride.
• Modern tyre consist of an inflatable rubber ring fitted round the wheel.
• Vehicles activities such as acceleration, vehicle control and braking occurs
through the tyres and their contact on the road surface.

45. Function Of Tyre To support the vehicle load.
To provide cushion against shock.
To transmit driving and braking forces to the road.
To provide cornering power for smooth steering.
It must be strong enough to carry loads and resist damage.
It must have a long lifetime and run smoothly.
Must meet all the requirement of all weather conditions and on all surfaces without overheating.
It must provide good road grip for traction, cornering, accelerating and
braking.

46. Desirable Properties
POWER CONSUMPPTION :- The automotive tyre absorb some power due to friction between the tread rubber and the road surface and also due to hysteresis loss on account of the tyre being continuously fixed release, should be least as less as possible.
TYRES NOISE :- Tyre noise may be in the form of definite pattern sing, a sequel, or aloud sound, Should be minimum.
BALANCING :- As a rotating part of automobile, must be balance statically and dynamically. Absence of balance give rise to peculiar oscillation called wheel tramp and wheel wobble.

47. Classification of Tyres
On basis of Construction
Conventional Tyre
Tubeless Tyre
On basis of Carcass or Skelton
Cross Ply Tyre
Radial Ply Tyre
Belted-Bias Tyre

48. Conventional Tube Tyre
Consists of two main parts i.e. the Carcass and the Tread.
Carcass is the basic structure taking mainly the various loads and consist of a number of plies wound in a particular fashion from the cords of rayon or any other suitable material.

49. Conventional Tube Tyre
The sidewall is a protective rubber coating on the outside of the tyre
carcass and is designed to resist cutting, abrasion, and cracking.
To prevent the tyre from being thrown off from the rim, the plies are attached to the two rings of bundles of bronze coated high tension steel wire strands insulated with rubber.
A radial load tyre normally has one such bundle in the lead whereas a cross ply tyre for off road use may have two or three bundles.
15 SEPTEMBER 2015
BY: KHUSHIN LAKSHKAR

50. Don’t need separate tube in luau the air which is under immense pressure is filled in the tyre itself for this purpose a non-return valve is fitted to the rim.
Based on the construction, almost similar to tubed tyre except lined on inside with a special air retaining liner made of halogenated rubber like Bromo-butyl or Chloro-butyl for better performance.
Major difference between the tubed tyre and the tubeless tyre lies in the bead area of the tyre.
15 SEPTEMBER 2015
BY: KHUSHIN LAKSHKAR

51. Tube Tyre vs. Tubeless Tyre
15 SEPTEMBER 2015 BY: KHUSHIN LAKSHKAR 11

52. Excellence of Tubeless Tyre over Tube Tyre
LESSER UN-SPRUNG WEIGHT :- Lighter compared to tubed tyre, reduces wheel bounce and un-sprung weight overall it saves fuel.
BETTER COOLING :- In case of tubed tyres, the heat associated with the
compressed air has to passed though the tube material i.e. rubber which is
a good conductor of heat. The absence of tube makes it possible for the
heat to be transferred to the atmosphere directly resulting in better cooling
ultimately increasing the life time of the tyre.
COMFORTABLE RIDE :- Tubeless tyre absorb shock and vibration are
absorbed at the tyre level thus making the ride softer, less noisy and more comfortable.
SLOWER LEAKAGE OF AIR :- The inner liner in the tubeless tyre is not
stretched like the tube it retains the air better resulting in its slower
leakage.

53. Excellence of Tubeless Tyre over Tube Tyre
SIMPLE ASSEMBLY :- Tubeless tyre only the tyre has to be fitted to the rim
making it invulnerable to punctured during its operation.
LESSER ROLLING RESISTANCE :- Rolling resistance in the tubeless tyre is less compared to the tubed based tyre, tubeless tyre sidewall is more mobile as there is no internal tube to generate heat and friction. This also helps the tyre to remain cooler by eliminating the risk of generating heat.
IMPROVED SAFETY :- In the presence of hole in the tyre it can be repaired simply by plugging whereas in case of conventional tubed tyres it is time consuming as the whole tyre has to be remove for repair. A tubeless tyre retains the air pressure for a long period even when it is punctured by a nail provided, placed at the same position. Thus the risk of being punctured is greatly reduced promoting reduce accident or improved safety.

54. Cross-Ply Tyre
Ply cords are woven at angle of 30 to 40 degree to the tyre axis.
Two layers that runs in opposite direction however the cords are not woven like warp because that would lead to the rubbing of the two layer that would lead to heat generation which would damage the tyre material.

55. Bias Ply Tyre Construction
One of the oldest design
Several textile plies are laid across each other, running from bead to bead in alternate directions
Number of plies depends on the size of the tyre and the load it has to carry
Same number of plies is used on the
crown and the sidewalls
Plies run at an angle from bead to bead
Does not use belts
Allows body of the tyre to flex easily
Improved cushioning, hence smooth ride on rough roads
Weakness: Reduced traction at high speeds and increase rolling resistance

56. Belted Bias Tyre Construction
Bias ply tyres with belts added to increase tread stiffness.
Belts do not run around the sidewalls, they lay under the tread area only
Belts and plies run at different angles
Offers some reduction in rolling resistance over a bias ply tire
Provides smooth ride and good traction

57. Radial Ply Tyre Construction
Plies run straight across from bead to bead.
Has a very flexible sidewall and a stiff
tread, giving it a very stable footprint
Consist of a carcass ply formed by textile arcs running from one bead to the other.
Each ply is laid at an angle of 90 degrees to the direction the tyre rolling
At the top of the tyre crown (under the tread), a belt made up of several plies reinforced with metal wire is laid.
These crown plies, laid one on top of the other, overlap at an angle determined by the type of the tyre.

58. Advantages of Radial Ply Tyres
Side walls can bend easily, its shock absorbing capacity is 25% more than bias ply or cross ply.
Lower rolling resistance and hysteresis loss leads to less fuel consumption
Longer tread life because of less heat build in tyre.
Breaking efficiency on wet roads is better because of greater sidewall
flexibility and tread stiffness.
Better steering characteristics.
While taking turns it has less tendency to distort and lift off the road from one side.
Larger resistance to punctures ,cuts and impacts in the tread area.

59. Cross-section of tubeless tyre

60. Advantages of tubeless tyres
Lesser unsprung weight.
Better cooling
Lesser rolling resistance
Comfortable ride
Slower leakage of air
Simpler assembly
Improved safety

61. WHEELS
Wheels along with the tyre has to take the vehicle load, provide a
cushioning effect and cope with the steering control.
Various requirement of an automobile requirement are:
Strong enough to perform the above functions.
Balanced both statically and dynamically.
Possible to remove or stand the vehicle wheel easily.
As lightest as possible so that the un-sprung weight is least.
Easy to clean, easy to wash and be of good quality.

62. WHEELS
Should not deteriorate with age and weathering. If material is vulnerable to corrosion, must be given suitable protective treatment.
must be of maximum strength to take the weight road shocks, driving torque and must be able to compensate all sorts of load varying in magnitude and direction.
must be strong enough to resist local deformation or when it hits a road kerb or any other obstacle.

63. TYPES OF AUTOMOBILES WHEELS
PRESSED STEEL DISC
WHEELS WITH STEELWIRE SPOKES
LIGHT ALLOY CASTING WHEELS.

64. PRESSED STEEL DISC Most popular and most used types of wheel.
Strong, light, stiff and resistant to accidental damage.
Can be manufacture in mass at a very economical low cost.
These type of wheel has two pressings namely the rim and the disc
member wielded together.

65. WIRE SPOKE WHEELS
Oldest in design but remained in use largely because of light weight and
strong construction but costly.
Rim attached to the hub through wire spokes.
Much stronger in tension and transmit all the forces to the rim.
Spoke has very little resistance to the bending, fastened so that complex
loads coming on the wheels are resolved into tensile load evenly
distributed among the adequate number of spokes.
The stress and loads faced by car wheel are very complex, more critical in
cases such as accelerating, braking and cornering and when such action is
required. More often the spokes have different sets to take the
acceleration, braking and weight forces.
Also able to take the side thrust during cornering by having a triangular pattern.

66. WIRE SPOKE WHEELS

67. LIGHT ALLOY CAST WHEEL
made from casting of light alloys of aluminium and magnesium.
Wider rims and radial ribs, also acts as angled spokes to provide
strength and air circulation.
Construction avoids any sharp lines and angles to improve strength.
Disadvantages over the other two, specially use in racing car.
Aluminium and magnesium are usually.

68. LIGHT ALLOY CAST WHEEL Light in weight.
Heavier sections can be used to improve the stiffness of the wheel and
result in better stress distribution.
Rims with larger area can be used, results in the use of wider tyres with less diameter, an absolute advantage in racing car since the lower centre of gravity and wider tyres result in better road grip particularly during cornering.
Better conductor of heat and hence heat dissipation from tyres and brakes is improved.
Only corrosion is the main problem, chemically sensitive to salt spray and
need regular checking and inspection for corrosion.

69. CAST LIGHT ALLOY WHEEL