The braking system in automobile. Mechanical Brakes. Hydraulic brakes. Power brakes.

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2. Braking system
• Brake is a device used for slowing ,stopping &
controlling the vehicle.
• Braking operation based on kinetic energy of vehicle
is to converting into heat, which dissipated into
atmosphere.
• While driving the vehicle, torque of the engine
produces The tractive effort due to periphery of
driving vehicle. When the brakes are applied it
produces negative tractive effort on wheel.
• While, this help to slow down an vehicle
Main functions of braking system
• To stop the vehicle safely in shortest possible
distance in case of emergency.
• To control the vehicle when it is descending along
the hills.
• To keep the vehicle in desired position after
bringing in at rest.
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3. Braking Requirements
1. Brakes must be strong enough to stop vehicle with in a minimum distance in an
emergency.
2. Brakes must have good antifade characterstics i.e. their effectiveness should not
decrease with prolonged application. This requirement demands cooling of brakes
should be very efficient.
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4. Types
• The brakes of an automobile are classified according to as :-
1. Purpose: From this point of view Brakes are classified as service or primary and parking or
secondary brakes.
2. Location: From this point of view brakes are located at wheels or at transmission.
3. Construction: -From this point of brakes are drum brakes and disc brakes.
4. Method of actuation: This criterion gives following brake type
a) Mechanical Brakes
b) Hydraulic Brakes
c) Electric Brakes
d) Vacuum Brakes
e) Air Brakes
f) By-wire Brakes
5. Extra braking effort
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5. Drum Brakes
• A drum brake is a brake in which the friction is caused by
a set of shoes or pads that press against a rotating drum
shaped part called a brake drum.
• The term "drum brake" usually means a brake in which
shoes press on the inner surface of the drum.
• When shoes press on the outside of the drum, it is usually
called a clasp brake.
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6. WHEEL CYLINDER
One wheel cylinder is used for each wheel. Two
pistons operate the shoes, one at each end of the
wheel cylinder. When hydraulic pressure from the
master cylinder acts upon the piston cup, the pistons
are pushed toward the shoes, forcing them against
the drum. When the brakes are not being applied,
the piston is returned to its original position by the
force of the brake shoe return springs.
BRAKE SHOE
Brake shoes are made of two pieces of sheet steel
welded together. The friction material is attached to
the lining table either by adhesive bonding or
riveting.
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7. BRAKE DRUM
The Brake Drum is generally made of a special type of cast iron.
Itis positioned very close to the brake shoe without actually
touching it, and rotates with the wheel and axle. As the lining is
pushed against the inner surface of the drum, friction heat can
reach as high as 600 degrees F.
The Brake Drum must be:
Accurately balanced.
Sufficiently rigid.
Resistant against wear.
Highly heat-conductive.
Lightweight.
BACK PLATE
The Back Plate serves as the base on which all the components
are assembled. It attaches to the axle and forms a solid surface
for the wheel cylinder, brake shoes and assorted hardware.
Since all the braking operations exert pressure on the back
plate, it needs to be very strong and resistant to any wear and
tear or corrosion.
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8. WORKING
The drum brake stops the tire from
rotating by using the hydraulic
pressure transmitted from the master
cylinder to the wheel cylinder to
press the brake shoe against that
brake drum, which is rotating
together with the tire.
When the hydraulic pressure to
the wheel cylinder disappears, the
force of the return spring pushes the
shoe away from the inner surface of
the drum and returns it to is original
position.
ADVATAGES
Drum brakes are smaller for the same brake force.
Due to simple in construction it can be easiliy
repair.
Due to the fact that a drum brake's friction
contact area is at the circumference of the brake,
a drum brake can provide more braking force
than an equal diameter disc brake.
DISADVANTAGES
The use of many clips and springs makes overhaul
of the brake drum assembly very time-consuming.
Another problem with drum brakes is that if a
vehicle is driven through water, it takes longer to
get the brakes working effectively.
When the drums are heated by hard braking,
the diameter of the drum increases slightly due to
thermal expansion, this means the brakes shoes
have to move farther and the brake pedal has to
be depressed further.
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9. DISC BREAK
A disc brake is a wheel brake which slows
rotation of the wheel by the friction caused by
pushing brake pads against a brake disc with a
set of calipers. This is connected to the wheel
and the axle. To stop the wheel, friction
material in the form of brake pads, mounted on
a device called a brake caliper, is forced
mechanically, hydraulically, or
electromagnetically against both sides of the
disc. Friction causes the disc and attached
wheel to slow or stop.
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10. Parts of disc break
Master cylinder
► It is the parts of disc break by which force is converted
into pressure
Caliper
The brake caliper is the assembly which houses the brake pads
and pistons. The pistons are usually made of plastic,
aluminium or chrome-plated steel.
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11. Rotors
Rotors are metal discs supported by the suspension.
The Calipers clamp on to them to slow their rotation,
and then slow or stop the car.
Rotor pad
► Rotor pad is provided friction force when is
contact with
rotor
► Work to slow or stop vehicle
Vents
► Vents are provided cooling
► when generate heat due to friction
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13. Mechanical Brakes
• Mechanical brakes are assemblies consisting of mechanical elements for the slowing or
stopping of vehicle.
• They use levers or linkages to transmit force from one point to another.
• There are several types of mechanical brakes.
1)Band brakes, the simplest brake configuration, have a metal
band lined with heat and wear resistant friction material.
2)Drum brakes, which are commonly used on automobile rear wheels work when shoes
press against a spinning surface called a drum.
3)Disc breaks are constructed of brake pads, a caliper, and a rotor. During operation, the
brake pads are squeezed against the rotor. Cone brakes are made with a cup and a
cone, which is lined with heat and wear resistant material. During actuation, the cone is
pressed against the mating cup surface.
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14. Pros of Mechanical Brakes:
•Easier to replace
•Cheaper
•Easy maintenance
Cons of Mechanical Brakes
•Needs more squeeze power by hand to enable
brake
•More maintenance required
•Brake cable gets stretched
•Heavier
band brake
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15. HYDRAULIC SYSTEM
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17. a) MASTER CYLINDER
The master cylinder is the heart of the brake's
hydraulic system.
It converts the force exerted on the brake pedal
into hydraulic pressure to apply the brakes.
Depressing the brake pedal moves a push rod in
the master cylinder. Mounted on the push rod are a
pair of pistons (primary and secondary) in tandem
(one after the other) that exert force against the fluid
in the master cylinder bore.
The pressure created displaces fluid through the
various brake circuits and lines to each of the wheels
and applies the brakes.
Since brake fluid is incompressible it acts like a
liquid linkage between the master cylinder's pistons
and the calipers and wheel cylinders.
Components
Fig: Single master cylinder
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18. https://youtu.be/Xk2zGvKfrhc
TANDEM CYLINDERS
Tandem cylinders are two interconnected cylinders.
The piston rod of the first cylinder enters through the
base of the second cylinder and pushes its base. In
this manner the greater effective surface area of
both pistons generates greater force, despite a small
cylinder diameter and unaltered operating pressure.
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19. b) WHEEL CYLINDER
A wheel cylinder is a component in a drum brake system. It is located in each wheel and is
usually at the top, above the shoes. Its responsibility is to exert force onto the shoes so they
can contact the drum and stop the vehicle with friction.
c) BRAKE SHOES
Brake shoes are made of two pieces of sheet steel welded together.
d) BRAKE DRUM
The brake drum is generally made of a special type of cast iron. It is positioned very close
to the brake shoe without actually touching it, and rotates with the wheel and axle.
e) BRAKE FLUID
Brake fluids are used to transfer force into pressure. It works because liquids are
incompressible.
Since oils damage rubber seals and hoses in the braking system, brake fluids are not
petroleum based.
Most brake fluids used today are glycolether based, but mineral oil and silicone (DOT 5)
based fluids are also available.
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21. Air Brakes
Vacuum Brakes
Electric Brakes
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22. Air Brakes
air brake system, is a type of friction brake for vehicles in which compressed air
pressing on a piston is used to apply the pressure to the brake pad needed to stop
the vehicle. Air brakes are used in large heavy vehicles, particularly those having
multiple trailers which must be linked into the brake system, such as trucks, buses,
trailers, and semi-trailers, in addition to their use in railroad trains. George
Westinghouse first developed air brakes for use in railway service.
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24. VACUUM BRAKES
The vacuum brake system is controlled through a brake pipe connecting abrake
valve in the driver's cab with braking equipment on every vehicle.
The operation of the brake equipment on each vehicle depends on the
condition of a vacuum created in the pipe by an ejector or exhauster.
The ejector, using steam on a steam locomotive, or an exhauster, using
electric power on other types of train, removes atmospheric pressure from the
brake pipe to create the vacuum.
With a full vacuum, the brake is released. With no vacuum, at normal
atmospheric pressure in the brake pipe, the brake is fully applied.
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25. PARTS
Exhauster:
It is usually controlled from the driver's brake
valve, being switched in at full speed to get
a brake release or at slow speed to maintain
the vacuum.
Brake Block:
This is the friction material which is pressed
against the surface of the wheel tread by
the upward movement of the brake cylinder
piston.
Vacuum Reservoir:
The operation of the vacuum brake relies on
the difference in pressure between one side
of the brake cylinder piston and the other. In
order to ensure there is always a source of
vacuum available to operate the brake, a
vacuum reservoir is provided on, or
connected to the upper side of the piston.
Brake Pipe:
The vacuum-carrying pipe running the length of the
train, which transmits the variations in pressure
required to control the brake. It is connected
between vehicles by flexible hoses, which can be
uncoupled to allow vehicles to be separated.
Ball Valve:
The ball valve is needed to ensure that the vacuum
in the vacuum reservoir is maintained at the required
level, i.e. the same as the brake pipe, during brake
release but that the connection to the brake pipe is
closed during a brake application. 25

26. ADVANTAGE
The advantage of being simple in design and of having the
ability to get a partial release, something the air brake could not
do without additional equipment.
LIMITATIONS
The practical limit on the degree of vacuum attainable means that a
very large brake piston and cylinder are required to generate the force
necessary on the brake blocks
The existence of vacuum in the train pipe can cause debris to be
sucked in.
The vacuum brake was not as effective as the air brake, it taking
longer to apply and requiring large cylinders to provide the same brake
effort as the air brake. It was also slow to release and requires
additional equipment to speed up its operation.
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27. Electrical Brakes
• Electric brakes are actuator devices that use an electrical
current or magnetic actuating force to slow or stop the
motion of a rotating vehicle.
• There are two main types of electric brakes: 1)magnetic and
2) friction.
• Magnetic brakes are non-contact brakes that use magnetic
fields to actuate the braking components.
• Permanent magnetic brake
• Electromagnetic brake
• Eddy current brakes
• Hysteresis powered brakes
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28. Permanent Magnetic Brake
In permanent magnet brakes, holding force is created by permanent magnets
and released by energizing the magnetic field. Permanent magnet brakes are
higher torque and smaller diameter versus spring applied brakes. Permanent
magnet brakes also allow torque to be controlled by varying the offsetting current
to the brake.
1. Applications:- electric motors, Robotics
2. Advantages:- High and accurate Torque,
long life, unaffected by power supply, safe
and easy to use
3. Disadvantages:- Require a constant current
control to offset the permanent magnetic
field.
https://youtu.be/JDCjT5MOs8Y
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29. Electromagnetic brake
Electro-mechanical disk brakes operate via
electrical actuation, but transmit torque
mechanically. When electricity is applied to the
coil of an electromagnet, the magnetic flux
attracts the armature to the face of the brake. As
it does so, it squeezes the inner and outer friction
disks together.
1. Applications:- Copy machines, conveyor drives,
packaging machinery, printing machinery, food
processing machinery and factory automation.
2. Advantages:- Fast response time, smooth,
reliable, and backlash free operation, produce
high torque, automatic air gap available.
3. Disadvantages:- Braking force diminishes as
speed diminishes, load cannot be held at a
standstill causing safety concern.
https://youtu.be/zytA5sspA1k 29

30. Eddy current brakes
eddy current brakes rely on electromagnetism to
stop objects from moving. Eddy currents are created
when a conductor passes through a magnetic field,
which creates opposing forces that spin inside the
conductor.
1. Applications:- Train and roller coaster brakes.
2. Advantages:- Noncontact, Frictionless,
resettable, light weight, few moving parts.
3. Disadvantages:- Unusable at low speeds,
generates heat.
https://youtu.be/2tsVuf9pLOE
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