AUTOMOTIVE MECHANICS SYSTEMS Wheel & Tires , Break system

Carlos Hermógenes garnica Ramírez

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

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

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).

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.

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

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 electrolyte type.

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.

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

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.

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

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 º to 90 º.

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 the pavement.

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.

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.

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 used according 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 each end 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.

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 shows the 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

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

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. 21 are 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.

Loads

154 (Index for easy assembly)

149 (twin mount Index)

The annotation regrovable means 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 are many 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.

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 of the 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 stuck in 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

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.

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, if correct, 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)

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, cause irregular 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, as appropriate, 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 different pressures 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.

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 the atmosphere.

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 shows the components of a drum brake system. They are:

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 a rigorous 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.

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 the lining 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)

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

The current trend is to place on vehicles drum brakes in the rear and front disc, although there are vehicles that are equipped with disc brakes on all four wheels,

The advantages over drum brakes are:

Better cooling of the whole. Less slack in the brake pedal pads for being very close to

the disk. More effective braking. System maintenance easier. More difficult to bring up the fading, to be more cool.

Description (fig. 6 and 7)

Figure 6

Figure 7

The bracket, clamp or jaw, consisting of:

A fork (E) attached to portamangueta (M). Two cylinders (T) containing the pistons (P). Between the pistons is the brake disc (D) attached to the

wheel, through attachment disc (R), all mounted on the axle shaft or spindle.

The brake pads (F), are sandwiched between the pistons and the brake disc.

The piston seal is made by a joint (J) of rectangular section, which also ensures the retreat of the piston.

A subject with a dust ring piston prevents oxidation.

Operation

Under the action of pressure in the cylinders the pistons apply against the disc, the pads on both sides, stopping.

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 the

disc 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

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 hidáulico 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 handbrake cable adjustment. S. Servo control frenos.T brake drum. U. Brake disc. X. Rear brake caliper. Y. Three-way fitting.

Figure 11

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.

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 drives the 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).

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) mounted at 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 isolating the 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

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:

Rigid They 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

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 the valve 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

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. Their mission 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 two independent circuits. Some of these systems are:

Fig. 18

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)

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

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

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) to move 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

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, eliminates irregular 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:

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) are transmitted 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.

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.

CONCLUSION We note that the above components are vital for a car because in them can be

determined to give good braking or not