Brake

Brake
This article is about the vehicle component. For other uses, see Brake ( disambiguation ) not to be confused with Break A brake is a mechanical device that inhibits movement by absorbing energy from a moving system. [ 1 ] It is used for slowing or stopping a moving vehicle, wheel, axle, or to prevent its motion, most often accomplished by means of clash. [ 2 ]

background

Most brakes normally use clash between two surfaces pressed together to convert the kinetic energy of the moving aim into heat, though other methods of department of energy conversion may be employed. For example, regenerative brake converts much of the energy to electrical energy, which may be stored for late practice. early methods convert kinetic energy into potential energy in such store forms as supercharge air or pressurized oil. Eddy current brakes use magnetic fields to convert kinetic energy into electric stream in the bracken disk, fin, or rail, which is converted into inflame. still early braking methods even transform kinetic energy into different forms, for exercise by transferring the energy to a rotating flywheel.

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Brakes are generally applied to rotating axles or wheels, but may besides take other forms such as the surface of a moving fluid ( flap deployed into water or tune ). Some vehicles use a combination of braking mechanisms, such as drag racing cars with both bicycle brakes and a chute, or airplanes with both rack brakes and haul flaps raised into the publicize during land. Since kinetic energy increases quadratically with speed ( K = m five 2 / 2 { \displaystyle K=mv^ { 2 } /2 } K=mv^{2}/2 ), an object move at 10 m/s has 100 times adenine much energy as one of the same mass moving at 1 m/s, and consequently the theoretical brake distance, when braking at the grip limit, is 100 times as long. In practice, debauched vehicles normally have significant air travel drag, and energy lost to publicize drag rises quickly with focal ratio. about all wheeled vehicles have a brake of some classify. even baggage carts and shopping carts may have them for use on a moving ramp. Most fixed-wing aircraft are fitted with wheel brakes on the undercarriage. Some aircraft besides feature air travel brakes designed to reduce their focal ratio in flight. luminary examples include gliders and some World War II -era aircraft, primarily some fighter aircraft and many dive bombers of the earned run average. These allow the aircraft to maintain a safe speed in a steep descent. The Saab B 17 dive bomber and Vought F4U Corsair combatant used the deploy undercarriage as an air brake. Friction brakes on automobiles store braking heat in the drum brake or disc brake while braking then conduct it to the vent gradually. When traveling downhill some vehicles can use their engines to brake. When the brake pedal of a modern vehicle with hydraulic brakes is pushed against the passkey cylinder, ultimately a piston pushes the brake pad against the brake disk which slows the roulette wheel down. On the brake barrel it is alike as the cylinder pushes the brake shoes against the cram which besides slows the wheel down .

Types

Brakes may be broadly described as using friction, pumping, or electromagnetics. One brake may use several principles : for example, a heart may pass fluid through an orifice to create clash :

frictional

Frictional brakes are most common and can be divided broadly into “ shoe ” or “ pad ” brakes, using an denotative wear come on, and hydrodynamic brakes, such as parachutes, which use clash in a cultivate fluid and do not explicitly wear. typically the terminus “ friction brake ” is used to mean pad/shoe brakes and excludes hydrodynamic brakes, even though hydrodynamic brakes use friction. Friction ( pad/shoe ) brakes are often rotating devices with a stationary slog and a revolve wear surface. common configurations include shoes that contract to rub on the outside of a rotating barrel, such as a band brake ; a rotating drum with shoes that expand to rub the at heart of a brake drum, normally called a “ drum brake “, although other drum configurations are potential ; and pads that emergency a revolve disk, normally called a “ phonograph record brake “. early brake configurations are used, but less often. For exercise, PCC trolley brakes include a bland shoe which is clamped to the rail with an electromagnet ; the Murphy brake pinches a revolve drum, and the Ausco Lambert phonograph record bracken uses a hollow disk ( two parallel discs with a structural bridge ) with shoes that sit between the phonograph record surfaces and expand laterally. A drum brake is a vehicle brake in which the friction is caused by a set of brake shoes that imperativeness against the inner surface of a rotating drum. The cram is connected to the rotating roadwheel hub. Drum brakes broadly can be found on older car and truck models. however, because of their low product cost, drum brake setups are besides installed on the rear of some low-cost modern vehicles. Compared to modern magnetic disk brakes, drum brakes wear out faster due to their tendency to overheat. The disk brake is a device for slowing or stopping the rotation of a road wheel. A brake magnetic disk ( or rotor in U.S. English ), normally made of frame cast-iron or ceramic, is connected to the rack or the axle. To stop the steering wheel, friction fabric in the form of brake pads ( mounted in a device called a brake caliper ) is forced mechanically, hydraulically, pneumatically or electromagnetically against both sides of the phonograph record. clash causes the magnetic disk and attached bicycle to slow or stop.

Pumping

Pumping brakes are frequently used where a pump is already part of the machinery. For case, an internal-combustion piston motive can have the fuel issue stopped, and then internal pump losses of the engine create some brake. Some engines use a valve overrule called a Jake brake to greatly increase pump losses. Pumping brakes can dump energy as heat, or can be regenerative brakes that recharge a press reservoir called a hydraulic accumulator .

electromagnetic

electromagnetic brakes are besides much used where an electric motor is already part of the machinery. For exemplar, many hybrid gasoline/electric vehicles use the electric motor as a generator to charge electric batteries and besides as a regenerative brake. Some diesel/electric dragoon locomotives use the electric motors to generate electricity which is then sent to a resistor depository financial institution and dumped as heat. Some vehicles, such as some transit buses, do not already have an electric motor but use a secondary “ retarder ” brake that is efficaciously a generator with an home short-circuit. relate types of such a brake are eddy current brakes, and electro-mechanical brakes ( which actually are magnetically drive friction brakes, but nowadays are often fair called “ electromagnetic brakes ” a well ). electromagnetic brakes slow an object through electromagnetic induction, which creates underground and in turn either heat or electricity. Friction brakes enforce atmospheric pressure on two separate objects to slow the vehicle in a control manner .

Characteristics

Brakes are much described according to several characteristics including :

  • Peak force – The peak force is the maximum decelerating effect that can be obtained. The peak force is often greater than the traction limit of the tires, in which case the brake can cause a wheel skid.
  • Continuous power dissipation – Brakes typically get hot in use, and fail when the temperature gets too high. The greatest amount of power (energy per unit time) that can be dissipated through the brake without failure is the continuous power dissipation. Continuous power dissipation often depends on e.g., the temperature and speed of ambient cooling air.
  • Fade – As a brake heats, it may become less effective, called brake fade. Some designs are inherently prone to fade, while other designs are relatively immune. Further, use considerations, such as cooling, often have a big effect on fade.
  • Smoothness – A brake that is grabby, pulses, has chatter, or otherwise exerts varying brake force may lead to skids. For example, railroad wheels have little traction, and friction brakes without an anti-skid mechanism often lead to skids, which increases maintenance costs and leads to a “thump thump” feeling for riders inside.
  • Power – Brakes are often described as “powerful” when a small human application force leads to a braking force that is higher than typical for other brakes in the same class. This notion of “powerful” does not relate to continuous power dissipation, and may be confusing in that a brake may be “powerful” and brake strongly with a gentle brake application, yet have lower (worse) peak force than a less “powerful” brake.
  • Pedal feel – Brake pedal feel encompasses subjective perception of brake power output as a function of pedal travel. Pedal travel is influenced by the fluid displacement of the brake and other factors.
  • Drag – Brakes have varied amount of drag in the off-brake condition depending on design of the system to accommodate total system compliance and deformation that exists under braking with ability to retract friction material from the rubbing surface in the off-brake condition.
  • Durability – Friction brakes have wear surfaces that must be renewed periodically. Wear surfaces include the brake shoes or pads, and also the brake disc or drum. There may be tradeoffs, for example a wear surface that generates high peak force may also wear quickly.
  • Weight – Brakes are often “added weight” in that they serve no other function. Further, brakes are often mounted on wheels, and unsprung weight can significantly hurt traction in some circumstances. “Weight” may mean the brake itself, or may include additional support structure.
  • Noise – Brakes usually create some minor noise when applied, but often create squeal or grinding noises that are quite loud.

foundation garment components

foundation components are the brake-assembly components at the wheels of a vehicle, named for forming the basis of the rest of the bracken arrangement. These mechanical parts contained around the wheels are controlled by the air brake system. The three types of foundation garment brake systems are “ S ” cam brakes, phonograph record brakes and lodge brakes. [ 3 ]

Brake boost

Most mod vehicles use a vacuum assisted brake system that greatly increases the impel applied to the vehicle ‘s brakes by its hustler. [ 4 ] This extra force is supplied by the manifold void generated by atmosphere menstruation being obstructed by the accelerator on a prevail engine. This force is greatly reduced when the engine is running at amply assailable accelerator, as the remainder between ambient atmosphere pressure and manifold paper ( absolute ) air coerce is reduced, and consequently available vacuum is diminished. however, brakes are rarely applied at full restrict ; the driver takes the properly animal foot off the boast pedal and moves it to the brake pedal – unless left-foot brake is used. Because of low vacuum at high RPM, reports of unintended acceleration are frequently accompanied by complaints of failed or weakened brakes, as the high-revving locomotive, having an afford choke, is unable to provide enough vacuum to power the brake promoter. This problem is exacerbated in vehicles equipped with automatic pistol transmissions as the vehicle will automatically downshift upon application of the brakes, thereby increasing the torsion delivered to the driven-wheels in reach with the road surface .

noise

Although ideally a brake would convert all the kinetic energy into heat, in practice a significant sum may be converted into acoustic department of energy alternatively, contributing to noise contamination. For road vehicles, the noise produced varies significantly with run down construction, road surface, and the magnitude of the deceleration. [ 5 ] noise can be caused by unlike things. These are signs that there may be issues with brakes wearing out over time.

Fires

Railway brake malfunctions can produce sparks and causal agent forest fires. [ 6 ]

inefficiency

A significant amount of energy is always lost while brake, tied with regenerative brake which is not perfectly efficient. therefore, a good metric unit of efficient department of energy practice while driving is to note how a lot one is braking. If the majority of deceleration is from ineluctable friction rather of braking, one is squeezing out most of the service from the vehicle. Minimizing brake use is one of the fuel economy-maximizing behaviors. While energy is always lost during a brake event, a secondary factor that influences efficiency is “ off-brake embroil ”, or drag that occurs when the brake is not intentionally actuated. After a brake consequence, hydraulic blackmail drops in the system, allowing the brake caliper pistons to retract. however, this retraction must accommodate all conformity in the system ( under pressure ) arsenic well as thermal aberration of components like the bracken phonograph record or the brake system will drag until the contact with the disk, for exercise, knocks the pads and pistons back from the rubbing coat. During this time, there can be significant brake drag. This brake drag can lead to significant epenthetic power loss, thus impacting fuel economy and overall vehicle performance .

See besides

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Category : Car Brakes