The document provides information about braking systems in automobiles. It discusses the components and functioning of drum brakes and disc brakes. It also describes the hydraulic brake system used in most passenger vehicles and the introduction of anti-lock braking systems (ABS) in the 1980s. ABS uses sensors and valves to prevent wheel lockup during hard braking, maintaining steering control. Causes of brake failure include issues that reduce friction like grease or worn components, and remedies involve replacing or adjusting the faulty parts.

1. FEDERAL UNIVERSITY OF TECHNOLOGY
MINNA
IN AFFILIATION WITH
FEDERAL COLLEGE OF EDUCATION (TECH)
AKOKA
A TERM PAPER ON
THE METHOD OF ACTUATING THE BRAKES,
ACTUATING MECHANISM; CAUSES AND
REMEDIES OF DAMAGES
AUTOMOBILE DEPARTMENT
BY
OLORUNFUNMI OLUWASEYI BABATUNDE
2011/3/0006AE
&
SALAMI AYODELE .O
2011/3/000
300 LEVEL
LECTURER:MR ADEOGUN K.B
COURSE: BRAKING SYSTEM

2. Introduction
THE BRAKE
Brake (device), device used to slow and stop a rotating wheel and thus a moving
vehicle. Brakes such as those on automobiles, trucks, trains, and bicycles use
friction between a wheel and another object to slow the motion of the vehicle.
The friction created by the rubbing together of two objects generates a large
amount of heat. A brake system must be capable of dissipating the heat as
rotating wheels slowly, because excess heat can cause the brakes to lose their
grip and fail.
Automobile braking device
Passenger cars and light trucks use a hydraulic brake system to stop motion
Such a system uses a chemical-based liquid known as brake fluid to transmit
pressure from a brake pedal to the brakes on each wheel. Aviator and inventor
Malcolm Longhead, one of the founders of the Lockheed Martin Corporation,
invented hydraulic brakes in 1918. Four-wheel hydraulic brakes were introduced
on the 1921 Duesenberg and the 1924 Chrysler automobile models.
To apply the brakes, the driver steps on a brake pedal. The pedal pushes a
piston inside an assembly called the master cylinder, which is filled with brake
fluid. The master cylinder is connected to the wheel brakes by hollow steel tubes
called brake lines, which are also filled with brake fluid. Pushing the piston
squeezes the fluid inside the master cylinder, creating hydraulic pressure. Since
liquid cannot be compressed, the pressure is transmitted through the brake lines
to additional pistons inside each brake. These pistons push brake linings against
drums and discs attached to the wheels in order to slow the vehicle down. For
safety purposes, the brake system for the four wheels of a car or truck is divided
into two separate circuits (each with its own piston inside the master cylinder). If
a fluid leak in either circuit causes a loss of pressure, the two brakes in the other
circuit will still be operational to stop the vehicle. Cars and trucks use two types
of brakes, called drum brakes and disc brakes, to stop motion.
Prior to 1965, all cars and trucks had drum brakes on the front and rear wheels.
Drum brakes consist of curved brake shoes that rest within a rotating iron
cylinder, or drum, connected to the axle and the wheel. When drum brakes are
applied, hydraulic pressure from the master cylinder pushes a pair of pistons in
the drum against the brake shoes. The shoes then press against the wall of the
drum, slowing the wheel. When the brakes are released, springs pull the shoes
back away from the drum. Various types of self-adjusting mechanisms within
drum brakes help maintain the correct amount of distance between the shoes
and drum.

3. In 1965 disc brakes were introduced on automobiles. Disc brakes have greater
stopping power than drum brakes and are usually installed on the front wheels to
improve braking during sudden stops. Disc brakes consist of a metal disc, or
rotor, that is connected to the wheel. A device called a caliper rests on the edge
of the rotor and holds two friction pads on either side of the rotor. Applying the
brakes causes fluid to push a piston within the caliper, which pinches the brake
pads against the rotor and slows the wheel. Disc brakes do not have return
springs, like those in drum brakes, to disengage the brakes. Instead, a seal
around the piston bends slightly when the brakes are applied and then retracts to
pull the piston back away from the rotor when the brake pedal is released. Also,
disc brakes rely on a very small amount of wobble, called run out,that is normally
present in the rotor. When the brakes are released, the runout of the rotor simply
pushes the pads away from the rotor.
Disc brakes are considered superior to drum brakes, because disc brakes can
handle higher braking temperatures and dissipate heat more quickly. Also, disc
brakes do not trap water as drum brakes can. When drum brakes become wet,
they suffer a decrease in braking, called brake fade, which can happen when
driving through deep puddles. Most cars and trucks use disc brakes on the front
wheels and drum brakes on the rear wheels, although some cars now feature
disc brakes on all wheels.
Disc brakes generally require added pedal pressure, so most vehicles equipped
with these brakes have power-braking systems to reduce a driver’s pedal effort.
Most power-braking systems use a vacuum to increase braking power. An
engine’s pistons create a vacuum as they draw air into the engine. This vacuum
is connected by a tube to both sides of a special spring-loaded diaphragm
located near the master cylinder. When the brake pedal is pressed, ordinary air is
allowed to enter on one side of the vacuum diaphragm. The vacuum on the other
side then pulls the diaphragm to one direction with added force. This added force
is sent to the master cylinder, increasing braking power.
Both drum and disc brakes contain several features to dissipate the large amount
of heat produced by friction. If the heat is not dissipated, the brakes may
malfunction. To dissipate heat more quickly, many rotors are vented and have
cooling fins sandwiched between the faces of the rotor. Most disc brakes use
semi metallic brake pads that contain chopped steel-wool fiber to aid heat
dissipation. The brake linings on drum brakes are made of heat-resistant
material. Prior to the introduction of disc brakes, most vehicles had brake linings
that contained asbestos fiber. Asbestos brake linings were mostly discontinued in
the late 1980s because of the health risks posed by asbestos. Even so, some
replacement brake linings made by parts manufacturers still contain asbestos.

4. Disc and Drum Brakes
Disc and drum brakes create friction to slow the wheels of a motor vehicle. When
a driver presses on the brake pedal of a vehicle, brake lines filled with fluid
transmit the force to the brakes. In a disc brake, the fluid pushes the brake pads
in the caliper against the rotor, slowing the wheel. In a drum brake, the fluid
pushes small pistons in the brake cylinder against the hinged brake shoes. The
shoes pivot outward and press against a drum attached to the wheel to slow the
wheel.
Anti-lock braking system (A.B.S)
In 1985 the first antilock brake system (ABS) was introduced for motor vehicles in
the United States as a safety feature to give drivers more control when braking.
ABS uses a microprocessor and individual wheel-speed sensors to monitor the
brakes. Hydraulic control valves for each brake circuit prevent skidding during
panic stops or when braking hard on wet or slippery surfaces. By 1990 ABS was
available on about 25 percent of all new cars and trucks. ABS is now available on
over 90 percent of all new vehicles.
Wheel-speed sensors monitor the rotation of each wheel. When the brakes are
applied, the ABS microprocessor compares wheel speeds. If one or more wheels
are rotating more slowly than the others are (a situation that causes wheel lockup
and loss of driver control), the system energizes control valves to isolate the
affected brake circuit. Brake pressure is held momentarily and is then released
before it is reapplied. This cycle allows the wheel to regain traction and prevents
skidding. The hold-release-reapply cycle is repeated rapidly for as long as

5. needed or until the vehicle comes to a stop. The cycling of the ABS control
valves and pulsating hydraulic pressure can usually be heard and felt through the
brake pedal. These indicators are designed intentionally to alert the driver that
the ABS is assisting braking. The driver should maintain firm pedal pressure
while the ABS is active, as pumping the pedal can defeat the action of the ABS
and increase the stopping distance. The ABS does not operate during normal
braking and does not engage unless one or more wheels start to lose traction.
Improvements in ABS technology now allow some systems to prevent wheel spin
when accelerating on wet or slippery surfaces. This capability is known as
traction control. When the wheel-speed sensors detect that a drive wheel is
starting to spin, the ABS applies the brake on the affected wheel to slow it down.
Some of these newer systems also provide additional control when cornering or
changing lanes.
The ABS is a four-wheel system that prevents wheel lock-up by automatically
modulating the brake pressure during an emergency stop. By preventing the
wheels from locking, it enables the driver to maintain steering control and to stop
in the shortest possible distance under most conditions. During normal braking,
the ABS and non-ABS brake pedal feel will be the same. During ABS operation,
a pulsation can be felt in the brake pedal, accompanied by a fall and then rise in
brake pedal height and a clicking sound.
Vehicles with ABS are equipped with a pedal-actuated, dual-brake system. The
basic hydraulic braking system consists of the following:
ABS hydraulic control valves and electronic control unit
Brake master cylinder
Necessary brake tubes and hoses
Hydraulic Control Unit (HCU).
Anti-lock brake control module.
Front anti-lock brake sensors / rear anti-lock brake sensors.
HOW A.B.S WORKS
When the driver hits the brakes this pressurizes a hydraulic system which causes
the brake pads to squeeze against the discs which causes the car to slow down.
If the ABS system detects that one wheel is slowing down more rapidly than the
rest (a symptom of wheel-lock) it automatically reduces the brake pressure on
this wheel by opening a pressure release valve in the hydraulic system. ABS also
has the ability to build the pressure back up via the hydraulic motor. The system
reacts remarkably quickly, and compared wheel speeds many times a second.

6. ABS systems can act on just the front wheels (which do most of the braking
work), or all four depending on what car you're driving.
An ABS system consists of the following components:
Some wheel speed sensors
Brake calipers
A hydraulic motor
Some pressure release valves
A quick thinking computer (or control module) which coordinates the whole
process
Anti-lock Brake Systems (ABS) operates as follows:
1. When the brakes are applied, fluid is forced from the brake master
cylinder outlet ports to the HCU inlet ports. This pressure is transmitted
through four normally open solenoid valves contained inside the HCU,
then through the outlet ports of the HCU to each wheel.
2. The primary (rear) circuit of the brake master cylinder feeds the front
brakes.
3. The secondary (front) circuit of the brake master cylinder feeds the rear
brakes.

7. 4. If the anti-lock brake control module senses a wheel is about to lock,
based on anti-lock brake sensor data, it closes the normally open solenoid
valve for that circuit. This prevents any more fluid from entering that
circuit.
5. The anti-lock brake control module then looks at the anti-lock brake
sensor signal from the affected wheel again.
6. If that wheel is still decelerating, it opens the solenoid valve for that circuit.
7. Once the affected wheel comes back up to speed, the anti-lock brake
control module returns the solenoid valves to their normal condition
allowing fluid flow to the affected brake.
8. The anti-lock brake control module monitors the electromechanical
components of the system.
9. Malfunction of the anti-lock brake system will cause the anti-lock brake
control module to shut off or inhibit the system. However, normal power-
assisted braking remains.
10. Loss of hydraulic fluid in the brake master cylinder will disable the anti-lock
system. [li[The 4-wheel anti-lock brake system is self-monitoring. When
the ignition switch is turned to the RUN position, the anti-lock brake control
module will perform a preliminary self-check on the anti-lock electrical
system indicated by a three second illumination of the yellow ABS wanting
indicator.
11. During vehicle operation, including normal and anti-lock braking, the anti-
lock brake control module monitors all electrical anti-lock functions and
some hydraulic operations.
12. Each time the vehicle is driven, as soon as vehicle speed reaches
approximately 20 km/h (12 mph), the anti-lock brake control module turns
on the pump motor for approximately one-half second. At this time, a
mechanical noise may be heard. This is a normal function of the self-
check by the anti-lock brake control module.
13. When the vehicle speed goes below 20 km/h (12 mph), the ABS turns off.
14. Most malfunctions of the anti-lock brake system and traction control
system, if equipped, will cause the yellow ABS warning indicator to be
illuminated.
Actuation Methods / Mechanism
Actuators are used on machinery, appliances, vehicles and medical devices to
cause motion of one part relative to another. Examples include automatic
openers on supermarket doors, solenoid operated power door locks, and fill
valves on washing machines. Actuators are available for every range of linear
and rotational movement and type of motive force that drives them. Actuators
may have total movements from hundredths of an inch to many feet.
Considerations for implementing actuator applications include range of motion,
driving force, mounting options, materials and motive power methodology
required.

8. Actuation Method Types
Actuation methods include mechanical, electro-magnetic, pneumatic, vacuum,
hydraulic and thermal sealed systems. All usually use one form of energy to
cause the release or movement of another form of energy.
Mechanical Actuators
o Mechanical actuators are many times driven by human power, such as lever
hood or trunk openers on automobiles where the lever inside the car is
connected to a cable which then pulls a spring loaded latch, releasing the hood
for opening.
Electrical Actuators
o Electrical actuators include solenoids which create a magnetic field in the
cylindrical opening inside a coil, drawing in an actuation plunger to create linear
motion. Electrical solenoids are used on industrial machines, appliances, vending
machines and in many areas of transportation including automotive starters,
choking mechanisms, fuel injection systems and safety interlocks.
Pneumatic and Vacuum Actuators
o Air driven actuators include pneumatic cylinders, bellows and vane motors. Large
diaphragm motors open and close pneumatically actuated control valves or
adjust their proportional position for throttling control. When combined with return
springs, pneumatic actuators can be used to position dampers or to lift doors. Air
brakes on large trucks use rugged diaphragm actuation motors. Automotive air
conditioning and heating systems use manifold vacuum to energize small
diaphragm actuators on air dampers and water valves.
Hydraulic Cylinders
Hydraulic actuators are used in all forms of transportation braking. One of
the advantages of hydraulic braking is that brake fluid is incompressible
and its force can be multiplied to thousands of pounds. Automotive disc
brake calipers and brake cylinders are examples of hydraulic actuators.
Actuators used in jacking, lifting and pressing all use hydraulic cylinders.

9. o
Actuator Mechanism
Causes of brake failure
Several factors can interfere with this friction and lead to brake failure:
Grease or oil on brakes causes brake failure, because it interferes with friction. If
oil leaks, it may indicate that an oil seal has failed.
When the brakes overheat to a great degree, the metal in the brake rotors or
drums develops hard spots. These are known as hot spots. The hot spots resist
the friction from the brake shoes and pads. Because the shoes or pads have
nothing they can grasp, there's no friction. Consequently, braking power is lost.
Brakes that squeal indicate that the brake pads are wearing thin. By the time the
brakes begin making a grinding sound, they've worn down past the pads to the
rotors, which will cost more than pads to replace

10. Fault Causes Remedies
 Noisy brake Weak shock absorber Change
Axle supports insecure Retighten
Broken springs change
 Erratic brake Weak road springs Change
Bad steering geometry Alignment
 Brake unbalanced Oil or brake fluid  Remove, wash
on linings and refit back
Distorted brake  Straiten or change
drum  Inflate the tyres
tyre evenly inflated  Re-tight the back
back plate loose plate
on the axle  Re-change the
worn steering steering
connection connection
bolts connecting  Re-tight back
axle suspension
spring loose
lining of different  Put correct grades
type or grade and same type
 Brake spongy  Low fluid level in Top up with fluid
reservoir
 Defective hose(if Remove and blow
blocked) and

11. leaking out, change hose
 Master cylinder
main cap worn
 Leak past master Remove and
cylinder secondary replace new one
cap Remove and
 Air in the system change
Bleeding to
eradicate air from
the system
 Brake grab Lining not bedded Repaired
in
Wrong type of Fit in the correct
lining type
Oil or brake fluid Wash with petrol,
lining clean with sand
Loose back plate paper or en-cloth
on anchor pins and refit
 Brake pedal Lining not bedded Repaired
in
Brake drum Change
grabbed or worn
out
Master cylinder You tight back to it
loosed on mount sitting
 Brake pedal hard Seized piston in Change
wheel cylinder Scrub with sand
Oil or brake fluid paper Wash with
on lining fuel, clean and
Binding brake refit back
pedal Clean rust area
and wash with
fluid and refit
 Far brake pedal Air in system Bleed to eradicate
travel air from the
Cracked braked system
drum Remove and
change totally
Change part that
Leak in system cause
leakage(pipe,
hose)
Low fluid level in Top up the level
reservoir with brake fluid

12. Excessive
clearance between Adjust
lining and drum
Excessive pushrod Adjust the push
clearance rod
 Brake drag Pull off spring Change
broken or wear
Master cylinder by Remove and clean
pass port chocked
Seized piston in Change
wheel cylinder
Shoe seized Change
piston on anchor
pin Change
Hand brake
mechanism seized Change
Pedal return
spring Change or clean
Binding pedal rust area and refit
Hand brake cable back
over adjusted
pedal to pushrod Re-adjust the
adjustment too hand brake
small
 Brake inefficient Lining not bedded Change
Lining greasy Wash and sand
Incorrect type of paper before fit
lining Remove and
change to correct
type of lining

13. References
http://auto.howstuffworks.com/auto-parts/brakes/brake-problems/brake-
failure1.htm
http://ptumech.loremate.com/automobile/node/6
http://www.drivingfast.net/technology/abs.htm
http://www.google.com.ng/imgres?q=braking+system&um=1&hl=en&biw=1366&bih=6
Salami. A project on braking system 1995