TABLE OF CONTENTS 1. Abstract 5 2. Introduction 6 3. How Brakes Work 7 4. Brake Basic 7 a. Leverage 8 b. Hydraulic 9 c. Friction 9 5. Simple Braking System 10 6. Types Of Brakes 10 a. Disc Brake 11 b. Drum Brakes 11 7. Types Of Disc Brake 11 a. Floating Caliper Disc Brake
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TABLE OF CONTENTS1. Abstract 52. Introduction 63. How Brakes Work 74. Brake Basic 7
8. Main parts of disc brakes 129. Working Of Disc Brake 1310. Self adjustment of disc brake 1511. Emergency Brakes 1512. Brake Fade 1613. Advantages 1814. Why are disc brakes more efficient ? 2115. Why do disc brakes have better braking behavior? 2216. Why do disk brakes have higher safety reserves? 2217. Limitations 2318. Testing Of Disc Brakes 2319. Conclusion 2420. References 25
ABSTRACT:
The current tendencies in automotive industry need intensive investigation in problems of
interaction of active safety systems with brake system equipments. At the same time, the
opportunities to decrease the power take-off of single components, disc brake systems.Disc
brakes sometimes spelled as "disk" brakes, use a flat, disk-shaped metal rotor that spins with the
wheel. When the brakes are applied, a caliper squeezes the brake pads against the disc (just as
you would stop a spinning disc by squeezing it between your fingers), slowing the wheel.
The disc brake used in the automobile is divided into two parts: a rotating
axisymmetrical disc, and the stationary pads. The hydraulic brake is an arrangement of braking
mechanism which uses brake fluid, typically containing ethylene glycol, to transfer pressure
from the controlling unit, which is usually near the operator of the vehicle, to the actual brake
mechanism, which is usually at or near the wheel of the vehicle.
The frictional heat, which is generated on the interface of the disc and pads, can cause
high temperature during the braking process. Hence the automobiles generally use disc brakes on
the front wheels and drum brakes on the rear wheels. The disc brakes have good stopping
performance and are usually safer and more efficient than drum brakes.
The four wheel disc brakes are more popular, swapping drums on all but the most basic
vehicles. Many two wheel automobiles design uses a drum brake for the rear wheel. Brake
technology began in the '60s as a serious attempt to provide adequate braking for performance
cars has ended in an industry where brakes range from supremely adequate to downright
phenomenal.
One of the first steps taken to improve braking came in the early '70s when
manufacturers, on a widespread scale, switched from drum to disc brakes. Since the majority of a
vehicle's stopping power is contained in the front wheels, only the front brakes were upgraded to
disc during much of this period. Since then, many manufacturers have adopted four-wheel disc
brakes on their high-end and performance models as well as their low-line economy cars.
Occasionally, however, as in the case of the 1999 Mazda Protege's, a manufacturer will revert
from a previous four-wheel disc setup to drum brakes for the rear of the car in order to cut both
production costs and purchase price.
INTRODUCTION
HISTORY OF DISK BRAKE
Ever since the invention of the wheel, if there has been "go" there has been a need for
"whoa." As the level of technology of human transportation has increased, the mechanical
devices used to slow down and stop vehicles has also become more complex. In this report I will
discuss the history of vehicular braking technology and possible future developments.
Before there was a "horse-less carriage," wagons, and other animal drawn vehicles relied
on the animal’s power to both accelerate and decelerate the vehicle. Eventually there was the
development of supplemental braking systems consisting of a hand lever to push a wooden
friction pad directly against the metal tread of the wheels. In wet conditions these crude brakes
would lose any effectiveness.
The early years of automotive development were an interesting time for the designing
engineers, "a period of innovation when there was no established practice and virtually all ideas
were new ones and worth trying. Quite rapidly, however, the design of many components
stabilized in concept and so it was with brakes; the majority of vehicles soon adopted drum
brakes, each consisting of two shoes which could be expanded inside a drum."
In this chaotic era is the first record of the disk brake. Dr. F.W. Lanchester patented a
design for a disk brake in 1902 in England. It was incorporated into the Lanchester car produced
between 1906 through 1914. These early disk brakes were not as effective at stopping as the
contemporary drum brakes of that time and were soon forgotten. Another important development
occurred in the 1920’s when drum brakes were used at all four wheels instead of a single brake
to halt only the back axle and wheels such as on the Ford model T. The disk brake was again
utilized during World War II in the landing gear of aircraft. The aircraft disk brake system was
adapted for use in automotive applications, first in racing in 1952, then in production
automobiles in 1956. United States auto manufacturers did not start to incorporate disk brakes in
lower priced non-high-performance cars until the late 1960’s.
HOW BRAKES WORK
We all know that pushing down on the brake pedal slows a car to a stop. But how does
this happen? How does your car transmit the force from your leg to its wheels? How does it
multiply the force so that it is enough to stop something as big as a car?
BRAKE BASICS
When you depress your brake pedal, your car transmits the force from your foot to its
brakes through a fluid. Since the actual brakes require a much greater force than you could apply
with your leg, your car must also multiply the force of your foot. It does this in two ways:
Mechanical advantage (leverage)
Hydraulic force multiplication
The brakes transmit the force to the tires using friction, and the tires transmit that force to the
road using friction also. Before we begin our discussion on the components of the brake system,
let's cover these three principles:
Leverage
Hydraulics
Friction
LEVERAGE
The pedal is designed in such a way that it can multiply the force from your leg several
times before any force is even transmitted to the brake fluid.
In the figure above, a force F is being applied to the left end of the lever. The left end of
the lever is twice as long (2X) as the right end (X). Therefore, on the right end of the lever a
force of 2F is available, but it acts through half of the distance (Y) that the left end moves (2Y).
Changing the relative lengths of the left and right ends of the lever changes the multipliers.
HYDRAULIC SYSTEMS The basic idea behind any hydraulic system is very simple: Force applied at one point is
transmitted to another point using an incompressible fluid, almost always an oil of some sort.
Most brake systems also multiply the force in the process
FRICTION
Friction is a measure of how hard it is to slide one object over another. Take a look at the
figure below. Both of the blocks are made from the same material, but one is heavier. I think we
all know which one will be harder for the bulldozer to push.
Friction force versus weight
To understand why this is, let's take a close look at one of the blocks and the table:
Even though the blocks look smooth to the naked eye, they are actually quite rough at the
microscopic level. When you set the block down on the table, the little peaks and valleys get
squished together, and some of them may actually weld together. The weight of the heavier
block causes it to squish together more, so it is even harder to slide.
Different materials have different microscopic structures; for instance, it is harder to slide
rubber against rubber than it is to slide steel against steel.
The type of material determines the coefficient of friction, the ratio of the force required
to slide the block to the block's weight. If the coefficient were 1.0 in our example, then it would
take 100 pounds of force to slide the 100-pound (45 kg) block, or 400 pounds (180 kg) of force
to slide the 400-pound block. If the coefficient were 0.1, then it would take 10 pounds of force to
slide to the 100-pound block or 40 pounds of force to slide the 400-pound block.
So the amount of force it takes to move a given block is proportional to that block's
weight. The more weight, the more force required. This concept applies for devices like brakes
and clutches, where a pad is pressed against a spinning disc. The more force that presses on the
pad, the greater the stopping force.
A SIMPLE BRAKE SYSTEM
The distance from the pedal to the pivot is four times the distance from the cylinder to the
pivot, so the force at the pedal will be increased by a factor of four before it is transmitted to the
cylinder.
The diameter of the brake cylinder is three times the diameter of the pedal cylinder. This
further multiplies the force by nine. All together, this system increases the force of your foot by a
factor of 36. If you put 10 pounds of force on the pedal, 360 pounds (162 kg) will be generated at
the wheel squeezing the brake pads.
There are a couple of problems with this simple system. What if we have a leak? If it is a
slow leak, eventually there will not be enough fluid left to fill the brake cylinder, and the brakes
will not function. If it is a major leak, then the first time you apply the brakes all of the fluid will
squirt out the leak and you will have complete brake failure.
TYPES OF BRAKES
1. DRUM BRAKES
2. DISC BRAKES (CALLIPER BRAKES)
DRUM BRAKES :-
The drum brake has two brake shoes and a piston. When you hit the brake pedal, the piston
pushes the brake shoes against the drum This is where it gets a little more complicated. as the
brake shoes contact the drum, there is a kind of wedging action, which has the effect of pressing
the shoes into the drum with more force. The extra braking force provided by the wedging action
allows drum brakes to use a smaller piston than disc brakes. But, because of the wedging action,
the shoes must be pulled away from the drum when the brakes are released. This is the reason for
some of the springs. Other springs help hold the brake shoes in place and return the adjuster arm
after it actuates.
DISK BRAKE BASICS:-
The disk brake has a metal disk instead of a drum. It has a flat shoe, or pad, located
on each side of the disk. To slow or stop the car, these two flat shoes are forced tightly against
the rotating disk, or rotor. Fluid pressure from the master cylinder forces the pistons to move in.
This action pushes the friction pads of the shoes tightly against the disk. The friction between the
shoes and the disk slows and stops the disk.
TYPES OF DISK BRAKES
The Three Types Of Disk Brakes Are:-
1. FLOATING CALIPER DISK BRAKES
2. FIXED CALIPER DISK BRAKES
3. SLIDING CALIPER DISK CALIPER
MAIN PARTS:
The main components of a disc brake are:
The brake pads
The caliper, which contains a piston
The rotor, which is mounted to the hub
BRAKE PAD
CALIPER AND ROTOR
WORKING OF DISC BRAKES
FLOATING-CALIPER DISK BRAKES
The caliper is the part that holds the break shoes on each side of the disk. In
the floating-caliper brake, two steel guide pins are threaded into the steering-knuckle adapter.
The caliper floats on four rubber bushings which fit on the inner and outer ends of the two guide
pins. The bushings allow the caliper to swing in or out slightly when the brakes are applied
When the brakes are applied, the brake fluid flows to the cylinder in the caliper and
pushes the piston out. The piston then forces the shoe against the disk. At the same time, the
pressure in the cylinder causes the caliper to pivot inward. This movement brings the other shoe
into tight contact with the disk. As a result, the two shoes “pinch” the disk tightly to produce the
braking action
STAGES OF WORKING
FIXED-CALIPER DISK BRAKE
This brake usually has four pistons, two on each side of the disk. The reason for the
name fixed-caliper is that the caliper is bolted solidly to the steering knuckle. When the brakes
are applied, the caliper cannot move. The four pistons are forced out of their caliper bores to
push the inner and outer brake shoes in against the disk. Some brakes of this type have used only
two pistons, one on each side of the disk
SLIDING-CALIPER DISK BRAKE
The sliding-caliper disk brake is similar to the floating-caliper disk brake. The
difference is that sliding-caliper is suspended from rubber bushings on bolts. This permits the
caliper to slide on the bolts when the brakes are applied.
Proper function of the brake depends on (1) the rotor must be straight and smooth, (2) the
caliper mechanism must be properly aligned with the rotor, (3) the pads must be positioned
correctly, (4) there must be enough "pad" left, and (5) the lever mechanism must push the pads
tightly against the rotor, with "lever" to spare.
Most modern cars have disc brakes on the front wheels, and some have disc brakes on all four
wheels. This is the part of the brake system that does the actual work of stopping the car
The most common type of disc brake on modern cars is the single-piston floating caliper.
In this article, we will learn all about this type of disc brake design