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8/9/2019 RAMIREZ - Wheel & Tires, Break System
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AUTOMOTIVEMECHANICS SYSTEMSWheel & Tires , Break system
Carlos Hermgenes garnica Ramrez
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Index
1.wheels and tires
1.1 introduction
1.2 elements of the wheel
1.3 tires radial & conventional
2.brake systems
2.1 introduction
2.2 elements of the system brakes
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Introduction
in the following information you will find a variety of two components essential for the
safety of your vehicle, these elements require optimum performance and the reader's
understanding give detailed information on their operating principles and how they
have evolved time
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WHEELS AND TIRES
Introduction
The wheel is an automobile that is in direct contact with the pavement.
Its mission, besides supporting the weight of the car, is to transmit the power from the
transmission in order to move the vehicle, and ensure the direction and stability in
times of acceleration and deceleration.
Wheels must be of adequate strength to withstand the weight of the vehicle, transmit
forces and braking thrusters and opposing lateral forces in a wide range of speeds and
terrain conditions.
It must also meet a range of features to fulfill their functions:
Resistance to sustain the weight of the vehicle.
Non slip resistance in times of braking.
Ability to absorb and dampen largely (10%) of uneven
ground.
Wear resistance.
Easy to dissipate heat produced during braking and as a
result of adhesion.
Light weight, reducing the effects of inertia and unsprung
weight.
Cross-resistance to the effects of drift. Aesthetics and ease of assembly and disassembly of the
coupling.
Elements of the wheel
The wheel assembly is made up two distinct elements , The metal part (D),the tire (N).
o Metal part
The metallic elements made up of:
Tire.
Disco.
Cube (in the wheels of wires or radios).
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It is the metal of the wheel, through a suitable profile, supports the tire and allow the
binding of the vehicle to the hub via disk or coupling parts.
The main feature is their profile tires, which is cross-section. It is essential to consider:
Tab (P).Is the surface which supports the heel side of the
deck.
Heel Seat (A).Is the surface of the rim on which rest the
heels of the cover.
Base (B).Corresponds to the surface of the tire between
the bead both seats.
Valve outlet hole (O).The tire has a hole that allows the
mounting of the valve where it excels.
Normally the disk rim, forming a single unit and joins in different ways.
Types of wheels
Deep base.
Knockdown: semihonda or flat.
Tire Terminology dimensional
Width (A)It is measured in inches. Is the elevation of the profile
between the two vertices, formed by the bead seats and
flanges.
Nominal diameter (D)
It is measured in inches. It is the difference
corresponding to the bead seat, as theoretically, in any of
the vertices mentioned above.
The tires are defined by their profile and its diameter.
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The disc wheel can be highlighted, mainly, the following functional areas:
Surface: is the disk surface to be fitted on the
corresponding hub of the vehicle.
Holes: are those that allow the passage of bolts.
Central hole (for the wheels that hold) is the hole in the
center of the disk that saves the hub of the hub.
Window valve: the opening in the disk to provide access
to inflation valve when necessary. Some tires have two
diametrically opposite windows, which makes the wheel
balancing, while providing dual access for mounting twin.
Ventilation windows: those practiced in the disk to
facilitate cooling of the brake drums or discs.
The types of wheels that are manufactured today are:
Disc wheels stamped steel. Are rigid, impact-resistant
and relatively light and easy to produce in large
quantities.
They are the most commonly used today.
Disc wheels in light alloy. The holes for the passage of the
mounting studs, have a conical seat for proper centering
of the wheel.
Can be of different types:
A -Conventional. B -no windows. C -Abort.
Types of connection between disc and rim
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The connection between the disk and the rim can be (Fig. 6):
A -For arc welding.
B -rivets.
C -On the spot welds.
D -by stamping.
Alloy wheels
By submitting a lower weight compared to steel, aluminum and magnesium alloys,
allow greater thickness, thereby increasing the rigidity and stress distribution takes
place on the wider area.
In this type of wheel, the rim may be wider, allowing the assembly of large section
tires.
Because this material is a good conductor of heat, cooling the brakes and tires is better
than steel wheels. However they are very sensitive to salt corrosion and electrolytetype.
Steel spoked wheels
These wheels are very light as well as of great strength. Its use is practically restricted
to certain vehicles or competitive sports.
All efforts are subject to the wheels is transmitted from the rim to the hub via their
radios whose tensile strength is much greater than the compression. Due to the low
resistance offered to the flexibility, the radios separately must intertwine in order to
achieve adequate strength.
Because the radios are fixed to the wheel rim with nuts, and thus do not get a proper
seal can not mount them tubeless tires.
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Its manufacturing cost is very high. The wheel is coupled to the shaft through the
grooves of the spindle and the wheel hub by a moth.
o The pneumatic
It is the part that is mounted on the rim. Is in direct contact with the ground. This is a
rubber air-filled, and provide necessary adhesion with the pavement, serves as a buffer
for the irregularities of the latter.
It consists of three main elements:
The camera (T),which has a cylindrical shape, is soft
rubber inflatable thing standing between the rim and the
outside (cover).
The cover (C),which is the outside, which then devote
further study.
The protector (P),which is between the rim and the
camera. Do not take all the wheels.
Tires with camera
Are the tire and the cover forming a whole with the camera, ensuring the seal it. The
camera has a built valve. They called tube-type.
This tire does not support a tubeless tire. The guard does not allow the camera to
come into contact with the rim.
Tubeless tires
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Currently used tubeless tires, in which this element is suppressed due to increased
leakage that offer air remaining between the cover and rim. They are called tubeless.
The main advantage of tubeless tires is that with a flat tire loses air rather slowly,
allowing for some miles round, while in the camera-equipped air is instantly lost. Other
benefits include decreased risk of bursting, no rust on the inside of the rim, no air
pockets form between the camera and deck and the reduced weight of the whole.
It has the disadvantage of the seal, as any deformation of the tire allows air loss.
The sealing is achieved through a highly impermeable layer of rubber to grip the inside
air that leads to the deck.
The cover has to be mounted on a rim special. Take a suitable valve, mounted in a hole
in it.
Covers
Housing
It is part of the tire structure that gives you flexibility and strength, and enduring
efforts. It consists of layers of tissue with stickers and cross strings together to give
strength to the whole.
Belt or wearing courses
Mounts between the tread and casing and is intended that the tire is not deformed
excessively, rolling through the area.
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Tread pattern
This is the area of contact between the ground and the vehicle, being the area of
greatest wear of the wheel. It consists of a thick layer of rubber, which is practiced
sculpture tire grip that allows both the vehicle and the evacuation of water for them.
Shoulders
They are outboard where the tread ends. This is where it generates the highest
temperature of the tire.
Flanks
Are the side edges of the cover. They are subjected to constant stresses (bending and
load). They are those who are deformed due to uneven ground.
Heels
They are the junction of the cover to the rim. They are housed in steel rings generally
securing the attachment to the rim.
Hard rubber layer
Whatever type of cover, inside is coated with a layer of vulcanized hard rubber.
Types of roofs
According to the architecture and arrangement of the layers or tarps that form the
housing cover or the use or nonuse of belts. Manufactured today are three types of
shells, which give the following names to the deck:
Diagonal or conventional covers.
Covers bias belted.
Radial tires.
Covers conventional diagonal or
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The housing is composed of several canvases that cross each other, heel to heel, and is
formed by layers of textile cords and steel wires, which form an angle of 30 to 40 to
the axis of the circumference of the cover, between layers and angles of 60 to 90 .
One of the most important features are the angles that form the threads, as they
determine their resistance, directional stability and discomfort on driving.
Drawbacks. By shooting occurs:
A deformation of the surface of contact with thepavement.
More rapid wear on heating.
A lower adhesion.
Higher fuel consumption.
At present almost not used.
Belted bias ply
Also called reinforced deck. It combines the diagonal roof structure with a strip or belt,
it does improve its characteristics. At present there is widespread use.
Radial tire
In this cover, the housing or frame, consists of several layers of textiles or steel wires
that are aimed in the direction of radius of a bead to another, forming with the axis of
the circumference of the cover at an angle of 90 .
Between the tread and the casing is placed several layers that form the belt. The
strings that form the belt at an angle approximately 20 , with the bearing pin. This
stabilizes the waist top or upper case.
Advantages:
This reduces the deformation of the surface in contact
with the pavement. There is no movement between the casing plies.
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Increased mileage.
Improving adherence.
Better stability.
Decreased fuel consumption.
Increased comfort due to its great flexibility.
Reduced heating and tire wear.
Covers materials
The main materials used in their manufacture are:
Natural or synthetic rubber. The obtained natural
coagulation of latex is a synthetic product obtained from
hydrocarbons.
The black smoke, to get:
The characteristic black color. Increased resistance to pressure.
Greater flexibility.
Sulfur, to facilitate vulcanization.
The cables, manufactured from rayon, polyester,
fiberglass and steel.
o Tire Choice
If we consider the functions of the tire on the vehicle, which occur simultaneously and
they are:
Support the load.
To transmit the motor effort.
Steer the vehicle.
Participate in stability.
Participate in the suspension.
Participate in the braking and moreover their application
to different lands and times of the year, the ideal tire is
very difficult to do, we can say that does not exist.
We choose the ideal type of structure, sculpture, wheel and pressure as a function of:
The vehicle.
The utilization.
The speed.
Time of filming.
For all this, the manufacturers make a range of products, under the terms of use, to
achieve:
The adhesion of the tire. Directional stability.
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The ride comfort.
Tire wear slow and smooth.
The rolling resistance.
Good drainage and a little noisy.
Manufacturers, in their catalogs, they recommend the best type of tire must be usedaccording to all the circumstances and factors involved in each specific case.
Types of wheel mounting
According to their assembly, are divided into two groups:
Simples. When a wheel is mounted at each end of the
axis of rotation. This is usually the employee at the front
of trucks.
Trade Center. When two wheels are mounted at eachend of the axis of rotation. It is the type of mount that is
often used at the rear of trucks and buses, supporting
approximately twice the load that the front axle.
The tires are matched must meet the following requirements:
Being of the same dimension
Inflated to the same pressure.
If possible, the same brand, type and have the same
degree of wear. Having a tolerance match on the axes of 0.5%.
Register, always larger diameter wheel on the outside of
the match.
The valve
The valve is the element that allows the tire filled with air, control or retention and
drainage.
Assembly can be:
In pneumatic chambers.
Tires without cameras.
The provision represents the valve in the chamber and its assembly.
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The valve that is mounted on the camera.
The layout and placement represents the rim of the valve in a tubeless tire.
The fig.17 showsthe valve mounted on the rim, if not bring a camera.
Special tires
These tires have required a special design to manufacture in order to achieve higher
speeds and increased security.
o Multiple tires with air chamber (Kleber) (fig. 18)
The structure of the radial tire and lacks the normal bladder, which in this case, is
divided into three compartments, each with its corresponding valve.
It is adaptable to all types of commercial tires. You do not need the spare tire,
maintaining stability in case of a puncture.
o Tire Denobo
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This tire does not bring a camera. The tread is wide and narrow sides. Under normal
conditions it is more effective than a radial tire.
In the event of a puncture, when it begins to deflate, puncture automatically sealed by
a fluid that carries inside, avoiding overheating of the tire. In this case we can make a
journey of 160 km at a speed of 80 km / h.
o Pneumatic Drop Center
The tire Drop Center is a tubeless tire and its use is for trucks and buses.
It is best refrigerated classic tires, having a slightly higher surface to them.
o Super Single Tires
This tire is tubeless type. Their relationship is so between 50 and 70.
Replaced in some cases, twin wheels because of its:
Simplicity.
Good load balancing.
Less weight.
Lower rolling resistance.
Approval
All tires must, for their production, meet the specifications and standards set forth in
the Regulations for Tires Approval No. 30 and No. 54.
Example: the approval mark E 9-002430, indicates that the tire has been deemed
approved in Spain with number 002430.
Nomenclature
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In the Approval Regulations relate the data corresponding to the identification of the
tire. These data must be printed on the tire sidewalls and respond to the specific
characteristics of the tire.
In Fig.21are described in numbers, letters and signs marking a cover for tourism
Michelin.
A -"Bib" indicates the location of the wear indicator.
B -The trademark.
C -Tire width: 185 mm.
D -Tire Series: 70. The figure 70 indicates that the deck height h is approximately equal
to 70% of its width g. That is: h = 0.7
E -The structure is radial g
F -Inner diameter: 14 inches (corresponds to the diameter of the tire).
G -Tubeless tire (Tubeless).
H -Load Index: 88 (560 Kg).
I -Index of speed.
J -Trademark.
K -Type.
o Markings truck covers
Example: 315 / 80 R 22.5 154/149 L REGROVABLE - Tubeless
Is marked in annotation 154 / 149 which means the charges.
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Loads
154 (Index for easy assembly)
149 (twin mount Index)
The annotation regrovablemeans that the tire is intended to be regrooving the tread
when it is worn.
o Structure
If the casing is radially contained a R.
If the tire is belted bias, appears Biasbel Ted.
If the cover is diagonal, does not include sign.
o Terms of Use
Speed Index: Represents the maximum recommended speed for the vehicle. There aremany indexes, among which stand out S(up to 180 km / h), H(180 to 210 km / h) and
V(over 210 km / h).
Load index or load index table: represents an index, which is tabulated. This table
shows us the number of kilos that corresponds to each tire (eg, index 88,
corresponding to 560 kg).
Use in snow or SM contained a sign S + M. (Recall that S= snow means snow in
English).
o With or without camera
If the tire bring a camera, does not contain any symbol.
If the tire does not bring a camera, includes the word
tubeless.
o Date of manufacture
In a box include 3 or 4 digits. The first two indicate the week of the year it was
manufactured and the last or last two digits, the decade in which it was manufactured.
o Wear indicator
For security reasons, do not wait until the tires are flat to replace them. The tires have
wear indicators, which are manifested by the appearance of smooth transverse bands
when the tread depth is reduced to 1.6 mm.
This device is intended to draw attention to tire wear and power and monitor its
progression.
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Retread
Is to replace the rubber of the tread, the whole canvas of the waist or part of it.
Only those tires can be retreaded with the housing in good condition.
Repairs are not always advisable.
Use of chains
When weather conditions cause the appearance of snow or ice on the asphalt, tire grip
is greatly reduced, causing a limitation in the ability of traction. Under these
conditions, to ensure the motor, the chains are placed covering the circumference ofthe cover across the direction of rotation of the same as regular distances. This allows
the string to "bite" on the snow and ice, providing enough traction for the advance.
Strings must always be placed in the drive shaft, ie, in the front-wheel drive vehicle in
front and rear in the rear-wheel drive, due to the heavy demands that cause the tread.
Vehicle speed should be moderate and the time when ice or snow is gone, should be
removed.
If conditions are too extreme, a good alternative to the chains are called winter tires.
Its main feature is the tread, which provides a range of mobile rubber shims are stuckin the snow a few millimeters and allow greater ability to adhere lengthwise. When
driving on dry roads, on its own configuration, the gills are sharpened due to wear
calculated by the manufacturer and that leaves them ready for next use in snow. The
downside of these tires is the most wear and less able to travel at high speed, so its
use should be limited to the winter season.
Another type of tire has the tread of a steel nails with rounded tips, standing on the
deck about 2 mm.
Main factors that influence the safety and performance of the tires
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The tires have a certain capacity. As a general rule should not be exceeded.
A tire overloaded by 20%, loses 30% or so of their performance.
o Under inflated
Shooting with low inflation is the cause of most of the damage the tire: abnormal
wear, deformation, heating, etc..
A low inflation of 20%, causing a reduction in yield of 30% or so.
o On inflation
Excessive pressure decreases adhesion, favoring skating and the risks of cuts, and
excessive fatigue causes the tire carcass.
o Room temperature
The tire wear also depends largely on the ambient temperature during the shoot.
o
Speed of shooting
Significantly influences the rate of tire wear.
A tire wears out twice as fast at 120 km / h. at 70 km / h.
o Shocks
The clashes against the curbs, the move at high speed over bumps, rocks or other
obstacles can damage the tire, but its consequences are not always appear at the time.
o Driving Style
A sport driving winding roads, with strong acceleration and frequent braking, tensions
rise considerably reduced and very variable performance tires.
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For guidance, we can say that, generally, if a guy running causes more fuel
consumption or faster wear of the brakes, while also causing increased consumption of
tires.
o Inflation pressures and verification
Correct inflation - Security.
- Fuel savings.
- Duration of the covers.
- Comfort
The inflation pressure should be checked regularly.
o Check the pressure when the tires are cold
In a passenger tire is cold that means that there shot a least an hour before, or has run
2 or 3 miles at low speed.
Light truck tires are cold means when there is no road for hours.
It is normal for pressure to build over the course of filming.
If you need to check the pressure after a certain route (hot tires), keep in mind that, ifcorrect, should be higher in 0.3 kg / cm. to the recommended cold.
Later, when possible, we must put adequate pressure on cold tires.
o Do not deflate tires never hot
Ovid not properly inflate the spare wheel.
o Watch the tires during the filming
Well maintained tires provide security and good mileage.
o Monitoring the state of the decks and wheels
The condition of the tires should be checked regularly:
The cuts, cracks, tears, tarpaulins apparent, etc., In the
tread or sidewall may require replacement or repair.
Check also the condition of the wheels and valves,
especially in the assembly without a camera.
o Watch how tire wear (fig. 26)
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The wear abnormally fast or irregular, indicating an abnormal use of pneumatic or
mechanical mismatch. For example:
A mismatch of parallelism in the front axle or in certain
cases in the back, causing abnormal wear and quick.
Clearances too important bearing or direction, causeirregular wear.
Misregulated brakes can cause localized wear or growing
from one point to another of the tread.
A fall exaggerated positive or negative , Can cause erosion that affects only a portion of
the tread.
Wheel Maintenance
The rim must be kept well balanced. This is done by placing the outside or inside, asappropriate, a lead counterweights prevent the vibrations caused by the difference in
mass along the perimeter.
We must take special care to clean up after driving on muddy roads, as gobs of mud
stuck to the tire can throw the tire and cause vibrations. We must also take
precautions when parking, avoiding rubbing the rims with the curbs, which could
dislodge balancing weights.
As regards the tires, the main care should focus on inflation pressures, based on those
recommended by the manufacturer and suitable to the load. Never put differentpressures in the tires on the same axis.
We must also pay attention to tread depth, remembering that it should not be less
than 1.6 mm. across its surface.
When wear occurs on both sides of the tread, the cause is insufficient pressure. If,
however, occurs in the central area due to excessive pressure.
To change the tires, you must:
Put the tires in better shape, or new, in the rear.
The change in position between the wheels, not to
change the side. Change front / rear without crossing left
/ right.
In case of a puncture or blowout, the driver can always
try to control the vehicle with the address. It is therefore
preferable to take the best wheels behind to try to
reduce the chances of damage to the axis on which we
can not act directly.
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BRAKE SYSTEM
Introduction
The mission of the braking system is to create a regulated power to slow or stop a
moving vehicle and to have it parked. This braking action is achieved by means of a
friction, that is, by the resistance to relative motion between two surfaces in contact,
making one of them stationary in contact with another phone, which will result in the
slowing down the latter, the system used to get the braking motor vehicles. The
braking action is, therefore, to absorb heat energy, when you touch a moving part of
solidarity to the wheels (drums and discs) from a fixed to the vehicle (the shoes and
pads). The heat energy generated in braking element is transmitted to theatmosphere.
The engine brake is used to slow down, first, to take our foot off the accelerator, the
engine being dragged by the rotation of the wheels and provides some help to normal
braking.
The brake system consists of:
Command system.
Braking element.
Braking element
Using two braking systems according to the elements used and how to operate the
phone:
Drum brake system.
Disc brake system.
o Drum brake system
Description
Figure 1 showsthe components of a drum brake system. They are:
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B -Bowler.
C -Union Pier footings below.
F -Retention teeth.
H -Garrison braking.
J -Dish pad holders.
L -top spring sap-TAS.
N -Transom pad control.
T -Tambor.
Z -Zapata.
Brake drum
Brake drums (T)are made of pearlitic gray cast centrifuged.
For resistance, while a convenient power dissipation, nerves are aggregated to the
outside of the drums.
The friction surface of drums must be machined perfectly, to get a precise finish, and arigorous focus and a uniform surface.
Shoe holder plate
It is a plate or disc (J)that supports the footings and the mechanisms of hydraulic or
mechanical drive.
Shoes
The calipers (Z)are constructed of forged steel or cast or stamped aluminum, the most
used the stamped steel, since they can occur in large quantity and low price.
To establish contact with the inner surface of the drum, the shoes are covered with a
lining (H)riveted or glued.
The shoes must meet the following characteristics:
Have a hardness less than the inner surface of the drum
for longer life.
Mechanical resistance to abrasion, high temperatures
and its shape. A high friction coefficient.
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For this we use materials that meet these properties, such as synthetic resins and
mineral compounds (made of carbon, sulfur, barium, magnesium and manganese).
The drum brake actuation means may be mechanical, hydraulic or pneumatic.
Operation (Fig. 2 and 3).
Figure 2 Figure 3
The drum is slowed by the action of two shoes, but for clarity in the explanation, only
one has been drawn in Fig.2.
The shoes come in one end a hole is introduced in which a pivot (P)in which the spins,
and the other end is resting on a cam (mechanical drive) or the pistons (hydraulic) of
the bowler.
When you pull the brake pedal or turning the cam (L)or moves the pistons of the
bowler (S) (Fig. 1),so that the pads are opened, turning on pivots. This causes thelining of the calipers (Z)coming into contact with the brake drum (B),decreasing the
speed of rotation thereof and thus the wheel.
When not actuated the brake pedal, the springs (L and C)bonding pads (Fig. 1),make
them return to their initial position.
Bowler of the wheel(Fig. 4)
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Figure 4
Receptors or bowlers cylinders (G)of the wheels are generally fixed on the pad holders
dishes.
The pressurized fluid enters the cylinder through a hole (R).
Each cylinder consists mainly of:
Two opposed pistons (A).
Two rubber sealing cups (D). A spring intermediary (C)that holds the cups applied to
the piston face.
The pistons act directly or through buttons (F)on the pads.
Each end of the cylinder is protected by a coat of rubber (B).At the bottom of each
bowler will put a screw (E).
When braking, the pressure acts on the two pistons (A) (Fig. 5),which in turn applied
to the calipers (Z)against the drums.
Figure 5
o
Disc Brake System
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By removing the cylinder pressure is released the disc.
There are no return springs or piston separation.
The disc is made of pearlitic gray cast iron.
The gag with the pills reach approximately 1 / 5 of thedisc surface.
Types of disc brake
The types of disc brakes is determined by the number of pistons and clamping system
clamp.
Depending on the number
of pistons According to the method of
securing the clamp
- Two pistons.
- Four pistons.
- Jaw.
- Mobile or floating clamp.
Depending on the number of pistons
Two pistons (fig. 8)
In this brake, the most used, the jaw has two pistons (P). Four-piston (fig. 9)
Used in high-performance vehicles. Four pistons are
used, increasing the capacity and effectiveness of the
braking.
According to the method of securing the clamp
If the jaw is fixed, each tablet is powered by a piston (fig. 8 and 9).If the jaw is
movable or floating, generally only takes a plunger to push on one side to the pickup
and the other is pinched jaw or to throw, pushing too hard against the bar and getting
the same braking action ( Fig. 10).
Figure 8
Figure 9
Figure 10
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Brake control system
The brake control system is constituted by the set of elements used to create the force
that will move the cam, the piston or to the membrane, according to the braking
system used. Both the brake disc and drum systems use the same command.
We distinguish the following types:
Mechanical system.
Hydraulic system. Pneumatic system.
Hydropneumatic
system.
A. Pedal brake pedal.
B. Bombra hidulico
control circuit.C. Steel cables.
D. Liquid filled expansion
tank circuit.
F. Braking corrector.
G. Control pipe rear
brakes.
I. Brake light switch
control.
K. Rear brake caliper.
L. Bar command.
N. Control piston rear brakes.
P. Palanca.
R. Regulating device handbrakecable adjustment.
S. Servo control frenos.T brake
drum.
U. Brake disc.
X. Rear brake caliper.
Y. Three-way fitting.
Figure 11
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o Mechanical system (parking brake)
Description (figs. 11 and 12)
Figure 12
It consists of a mechanical brake mechanism (fig. 11),called the parking brake,
operated from inside the vehicle by means of the lever (P)so that, once set command,
the wheels are locked to prevent vehicle movement. This mechanism is generally
applied to the rear wheels when the vehicle is stationary.
The lever (P)drives the flexible steel cable (C).
Operation in the drum brake system
The displacement of the pads is obtained by means of a lever (D)and a push rod (V)
(Fig. 12).
The control is done by cable (C)and is generally performed as follows:
By operating the cable on the lever (D),it works by pushing the left stick (V)dozer,which approximates the shoe (K)to the drum.
The lever (D)at the top shoe close (X)to the drum. After about two lugs, cable and the
action continues, the pressure pads on the brake drum causes it to freeze.
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Figure 13
If the system disk (Fig. 13),the parking brake operates as follows:
The lever (C)rotates in the direction of the arrow by moving the lever (L),which drivesthe plunger (E),using the tablet (A)against the disc (D).The pellet (B)acts on the
reaction exerted on the clamp (M).
o Hydraulics(Fig. 11)
The operation of hydraulic systems are based on two principles:
Fluids are practically incompressible. The same pressure
that runs on the master cylinder to the bowler gets full.
When a liquid, totally enclosed in a container, a pressure
is applied at one point, the pressure is communicated to
the whole mass of liquid with the same intensity.
The force obtained in each cylinder will be proportional to the respective surface of
each piston being greater, therefore, in having larger diameter pistons.
The braking system hydraulically should therefore allow to distribute the braking effort
on all 4 wheels. This is necessary to provide 4 receiving elements (bowler).
The system consists essentially of (fig. 14):
Figure 14
A brake fluid reservoir (L).
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A main pump (B).
A control or brake pedal (M).
Cylinders receptors (bowler) (D).
The pipes connecting the various elements (T).
Main pump(fig. 15)
Figure 15
It consists of a cast (A)within which there is a cylinder which moves a piston (P).
In the axis of piston rod is placed (V) mountedat its other end, to pedal (F).
On the opposite side of the piston hole and connects with the pipe is closed by a
double-acting valve (D),kept on its seat by a spring rubber (R).
The other end of the piston (pedal side) is manned by a rubber seal (L),ensuring the
seal.
The top of the cylinder is connected to the reservoir of liquid (X)by a feed hole (E)and
an expansion port (M),much smaller than the first.
Operation of the pump to operate the pedal
By pressing the pedal, the tip of the push rod will bear
against the piston after traveling a short distance (about
1 mm.) Which is the free travel of the pedal.
By continuing stepping, the piston moves slightly in the
cylinder and close the hole expansion (M),thus isolatingthe hopper chamber.
The expansion port is closed, the advancement of the
piston increases the pressure when this pressure exceeds
the small spring action of the valve, it opens and the fluid
will be sent by pipeline to the wheel cylinders (slave
cylinders).
The pistons of the bowlers pushing the shoes against the
drums.
Operation of the pump to release the pedal
When the foot is released:By the action of the spring pads recover its rest position
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by dragging them to the pistons of the bowlers of the
wheels, the fluid returns through the pipes to the main
pump.
The main pump piston by a spring recovers its original
position, creating a pressure drop in the circuit, which
brings back the liquid.The force of the fluid circuit returns to the main cylinder
acts on the valve, double acting spring slightly
compressed, the fluid then passes through the periphery
of it.
Pipes
Pipes can be:
RigidThey consist of copper tubes, brass or steel. They must
be resistant to oxidation and corrosion. Place fixed to the
frame or bodywork.
Flexible
These are called tails. Connect the dots with movements
during walking and is mounted between the frame and
wheels, and frame and the front or rear axles.
Auxiliaries
These are elements that are applied to the brake master system, and explained, to
improve performance, increase security and make it more comfortable in handling.
These are:
o
Braking Limiter
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Description
For the braking of a vehicle is performed in an efficient, it is necessary to apply a
resistive torque wheels without locking the wheels important. The adhesion of the
wheels to the ground state is a function of soil, tire and the load on the wheels.
When hard braking a vehicle, the vehicle's kinetic energy is transferred to the front
wheels, while the rear load is lightened. We therefore applied a significant burden on
the front with respect to the applied load on the rear.
As adherence is a function of load, this increase and decrease the front wheels in the
rear.
For safe and effective braking, it is necessary to vary in proportion braking effort
exerted on the rear wheels relative to the front.
This device (fig. 16)consists of a body (A).Inside moves a valve (V)which is based on a
calibrated spring (M).
Brake fluid enters the limiter for the bottom (B)and leaves to go to the rear wheels
lock inserts the two side holes (D and F).
Figure 16
Operation
When the brake pedal for a brake light, brake fluid passes through the contour of thevalve and the pressure reaches the bowlers of the rear wheels, is identical to the front
wheels.
When you want to get fast braking of the vehicle, the fluid pressure acting on the
bottom of the valve, moving and overcoming the action of the spring and back clog
pipes. The pressure on the rear wheels is therefore limited.
When the weight of the back can vary considerably, limiting variables are used, which
act according to the load. It works more or less effective, depending on the height and
position of the frame and suspension.
o Brake Compensator
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It depends on your point of application. Are classified as:
Sobrepesores: applied to the front brake system. Their
mission is to amplify the pressure supplied by the master
cylinder.
Depressants: applied to the rear brake system. Theirmission is to reduce the pressure on the rear braking
elements to avoid locking the wheels.
o Braking or security
The hydraulic main pump with a piston brakes, as described above, has the
disadvantage that a brake fluid leak knocked out the entire system with the
consequent risk that this entails.
Different manufacturers solve this problem by equipping the vehicle with a dual brake
master pump with a double, with a primary and a secondary piston, and with twoindependent circuits. Some of these systems are:
Fig. 18
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Fig. 20
Circuits, front and rear, are separated by a piston for
each circuit (Fig. 17).
The separation of the circuits is performed in diagonal
left front wheel and right front right rear left rear wheel.This system is widely used today.
A dual master cylinder piston (fig. 19)acts on the
elements of the four-wheel braking and the other circuit
piston and act only on the front wheels.
A dual master cylinder piston (fig. 20)acts on both front
and rear wheels, and the other piston acts on the two
front wheels and one rear wheel. Each front disc brake is
actuated by two pairs of pads.
o Servo-brakes(Fig. 21)
Serves to reduce the effort that the driver must apply to actuate the braking elements.
Install the brake booster, necessarily, between the brake pedal and pump. It has an
immovable position.
Whatever the type, power brakes are always designed so that the driver effort can be
exerted directly on the brake circuit is defective, the welfare system (servo).
Figure 21
Operation (fig. 22)
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In resting phase
The valve (A)is open. The valve (B)is closed. The cameras, anterior (D)and posterior
(C)receive depression of the motor (intake manifold) and spring (M)pushes the piston
back.
Active phase
The valve (A)is closed. The valve (B)is open. The posterior chamber (C)is at
atmospheric pressure and anterior chamber (D),depression of the engine, therefore,
there is an imbalance, the pressure compresses the spring and multiplies the force
exerted on the pedal.
Figure 22
o Electrodynamic retarder (brake power)(Figs. 23 and 24)
Also called a retarder or retarder. This type of brake works only when the engine is
running and to complement the service brake.
Figure 23
Figure 24
Operation
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The fixture or retarder operates without friction, through the principle of eddy
currents.
Two mild steel discs (rotors), driven directly by the vehicle's transmission, rotating
magnetic field created by electromagnets solidarity of the chassis (coils), and are
powered by the vehicle's electrical system.
The retarder is operated from the cockpit by a lever that acts by binding the battery of
the vehicle with electromagnets.
Four independent circuits allow the gradual excitation of the brake torque. They serve
mainly to stop in long slopes, in order to download the service brake to avoid the
phenomenon of fading. To produce a reduction in speed there is no friction between
the movable and fixed. The electric brake is integrated in the vehicle's transmission to
the output of the gearbox or close to the differential and is fastened to the chassis
itself. It is used in heavy vehicles such as third auxiliary brake. It is, therefore, a brake,although it can stop the vehicle.
o Hydrodynamic retarder (hydraulic)(Figs. 25)
Retarder is projecting a current flow of oil, the rotor (R)on the stator (E).
Its mission is to transform kinetic energy into thermal oil. The heat generated is largely
absorbed in the heat exchanger (I),which is essential for the proper operation of the
retarder.
The control and maintenance of oil will be in accordance with the manufacturer's
instructions.
The leads retarder inside a casing and two concave disks with blades facing. One of
them, the stator, (E)attached to the frame straight and the other is the rotor (R)
attached to the shaft.
The system is operated via a lever with various positions or by the brake pedal. During
operation there is no mechanical friction.
When activating the retarder is sent to the crankcase oil containing the rotor and
stator. By turning the rotor as a pump pushes the oil to the stator which produces the
energy absorption and the reaction produces brake rotor drive system.
Figure 25
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o Retarder on the exhaust manifold(Figs. 26 and 27)
The mission of this system is to get the braking effect by making the engine as a
compressor, absorbing kinetic energy takes the vehicle. Its use is equivalent to a
reduction in the gearbox.
By actuating the piston gradually, air pressure drives the circuit court cylinder injection
(E)and the master cylinder of the throttle valve (C),located at the outlet of the
exhaust manifold, retaining the gases exhaust and performing the effect on the engine
compressor.
Inertia braking system
The mission of inertia braking system is to stop the trailer when braking the vehicle.
Its use is reduced to caravans or light trailers.
shows the set of arms and lever system.
Operation
The bar (L),it is usually hitch own spear, and is mechanically connected to the trailer
brake drums. By pulling the tractor trailer, the spear separates the drum pads, and
when it stops, the very inertia of the trailer makes the bar (B) tomove forward,
shortening the distance (D)and operating the brake shoes forcing them to touch the
drum, as indicated by arrows. The more abrupt deceleration of the vehicle is the
tractor, the more intense the effect on the bar and consequently the stronger the
braking on the trailer.
Anti-lock brakes or ABS
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The antilock system's mission is to allow maximum use of braking power grip
conditions very critical, automatically adjusting braking force with a permissible degree
of slippage between the tire and the road, giving preference to directional stability and
maneuverability on the braking distance.
Avoid wheel locks, even in icy tracks, shortens the braking distance, eliminatesirregular tire wear and prevent the braking effect between the scissor drive vehicle and
trailer.
Description
Basically the ABS system has the following elements:
B -Electronic control unit.
C -Group modulator (solenoid).
D -master cylinder (hydraulic or pneumatic system).
E -Pedal (hydraulic or pneumatic system).
PS -speed transducer (sensor-wheel polar).
Shutter speed
What is the sensor (S)and the main field, which informs the control unit of the speed
of each wheel.
Modular group
The solenoid valves are mainly adapting the pressure in the brake slave cylinders,
depending on orders received by the control unit.
The braking system consists of a hydraulic unit that connects via the pump solenoid
brake cylinders.
In pneumatic braking device consists of separate valves.
The valves can get into the brake cylinders:
The reduction of pressure.
Maintaining pressure.
Communication with the brake circuits.
Electronic control unit
Must fulfill the following functions:
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Receives signals from the sensors in the wheels (sensor,
wheel-polar).
The signals are analyzed.
Are calculated wheel slip and decelerations or
accelerations.
Send the valves (modulating the braking pressure). Performs checking of the system, leaving all or part
inoperative in case of failure, alerting the driver to
witnesses.
Operation(fig. 30)
The ABS is an electronic system that automatically corrects the braking force of each
wheel (or axis) depending on the level of grip it finds.
The electrical impulses generated by induction on the wheel sensor (sensors) aretransmitted to the electronic control unit, where they are constantly evaluated.
When the unit detects a tendency to lock the wheel, the valve directs the start of the
modulation of pressure in brake cylinders.
This modulation allows the wheel to obtain effective braking with minimal slippage.
The operating control system remains on whether the vehicle speed is less than 7 km /
h. or 15 km / h. if coupled to a semitrailer, and off to overcome these speeds.
In case of failure of the ABS system it is canceled and the vehicle can continue to
operate, using the classic control system is installed.
When the availability of motor vehicle and trailer or semitrailer, the ideal is that both
have ABS.
Pneumatic brake
Pneumatic braking systems used to drive air pressure, allowing to obtain high braking
forces. Compressed air is generated by a compressor which is driven by a belt that
transmits motion from the crankshaft. It is used in large trucks and buses carrying
capacities, which for its braking system must be equipped with brakes that can
develop powerful.
The installation is composed of the systems and circuits described in Fig.32:
Power System:
Delivers.
Regulates.
Holds.
Stores the compressed air.
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Figure 32
System use:
Generates the braking forces.
Control system:
Check pressures of certain circuits.
Advised of the existence of a pressure drop at
some point.
The installation of service and emergency brakes, is composed of the following circuits:
Power circuit..
Circuit No. 1 .- front service brakes and emergency
vehicle to the trailer.
Circuit No. 2 .- front service brakes of the tractor and the
trailer .
Circuit No. 3 .- emergency and parking brakes on the rear
axle of the tractor and ancillary services.
Brake circuit remote control trailer .
o Description
Compressor cylinder
End
The compressor is used to produce compressed air.
Operation
The air absorbed by the piston through the intake valve is compressed by the piston on
its way forward and sent the cylinder through the exhaust valves. The outlet of the
compressor lubricating oil is made by the engine lubrication circuit of the vehicle.
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CONCLUSION
We note that the above components are vital for a car because in them can bedetermined to give good braking or not