Brakes are mechanical devices that impede motion by absorbing energy from moving systems. This is used to slow or stop a moving vehicle, wheel, shaft, or to prevent its movement, most often achieved by means of friction.
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Most brakes generally use friction between two pressed surfaces together to convert the kinetic energy of moving objects into heat, although other energy conversion methods can be used. For example, regenerative braking converts a lot of energy into electrical energy, which can be stored for later use. Another method converts kinetic energy into potential energy in a stored form such as pressurized air or pressurized oil. The eddy current brake uses a magnetic field to convert kinetic energy into electric current in disc brakes, fins, or rails, which are converted into heat. Still other braking methods even convert kinetic energy into different shapes, for example by transferring energy to the spinning mad wheel.
Brakes are generally applied to rotating axles or wheels, but can also take other forms such as the surface of moving fluid (flaps propagated to water or air). Some vehicles use a combination of braking mechanisms, such as drag racing cars with wheel brakes and parachutes, or airplanes with wheel brakes and wing drags lifted into the air on landing.
Karena energi kinetik meningkat secara kuadratis dengan kecepatan ( ), sebuah objek bergerak pada 10 m/s memiliki 100 kali lebih banyak energi sebagai salah satu massa yang sama bergerak pada 1 m/s, dan akibatnya pengereman teoritis jarak, ketika pengereman pada batas traksi, adalah 100 kali lebih lama. Dalam prakteknya, kendaraan yang cepat biasanya memiliki hambatan udara yang signifikan, dan energi yang hilang karena hambatan udara meningkat dengan cepat dengan kecepatan.
Almost all wheeled vehicles have some kind of brakes. Even luggage carts and shopping carts can use them for use on a moving road. Most fixed wing aircraft are equipped with wheel brakes on the undercarriage. Some aircraft also feature air brakes designed to reduce their speed in flight. Important examples include gliders and several World War II planes, especially some fighter planes and many dive bombers of the era. This allows the aircraft to maintain a safe pace in steep decline. Saab B 17 and Vought F4U Corsair fighter bomber uses undercarriage which is used as air brake.
Brake friction on the car saves braking heat in drum brakes or brake discs when braking then steers them into the air gradually. When traveling down a few vehicles can use their machine to brake.
When the modern vehicle brake pedal with hydraulic brakes is pushed against the master cylinder, the piston finally pushes the brake pads against the disc brakes that slow the wheel down. On the drum brake it's just like a cylinder pushing the brake shoe against the drum which also slows the wheel down.
Maps Brake
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Brakes can be widely described as using friction, pumping, or electromagnetism. One brake can use several principles: for example, a pump can drain fluid through a hole to create friction:
Swipe
Frictional brakes are the most common and can be widely divided into "shoe" or "pad" brakes, using explicit wear surfaces, and hydrodynamic brakes, such as parachutes, that use friction in working fluids and are not explicitly used. Usually the term "friction brake" is used to decipher the brake pad/shoe and remove the hydrodynamic brake, although hydrodynamic brakes use friction. Friction (pad/shoe) brakes often rotate the device with a stationary pad and a rotating wear surface. Common configurations include shoes that contract to rub outside a rotating drum, such as a brake band; a rotating drum with an expanding shoe to rub the inside of the drum, usually called "drum brake", although other drum configurations are possible; and pads that pinch the rotating disk, commonly called "disc brakes". Other brake configurations are used, but less frequently. For example, PCC trolley brakes include flat shoes clamped onto rails with electromagnets; The Murphy brakes pinch the rotating drum, and the Ausco Lambert disc brakes are using hollow discs (two parallel discs with structural bridges) with the shoe between the disk surfaces and extending laterally.
The drum brake is a vehicle brake where friction is caused by a set of brake shoes that compresses the inner surface of a rotating drum. The drum is connected to the rotating hub of the roadwheel.
Brake drums can generally be found on older cars and trucks. However, due to low production costs, the installation of drum brakes is also installed at the rear of some of the cheaper new vehicles. Compared to modern disc brakes, drum brakes run faster because of their tendency to overheat.
Disc brakes are a tool to slow or stop the rotation of the wheel. The brake disk (or rotor in English U.S.), usually made of cast iron or ceramic, is connected to a wheel or axle. To stop the wheel, the friction material in the form of brake pads (mounted on a device called the brake calipers) is mechanically, hydraulically, pneumatically or electromagnetically applied to both sides of the disc. Friction causes the disc and the connected wheels to slow down or stop.
Pumping
Pumping brakes are often used where the pump is already part of the machine. For example, internal combustion piston motors can have a stop fuel supply, and then pumping internal losses from the engine makes some braking. Some engines use override valves called Jake brakes to increase pumping losses. The pumping brakes can dispose of energy as heat, or it can be a regenerative brake that replenishes a pressure reservoir called a hydraulic accumulator.
Electromagnetic
Electromagnetic brakes are also commonly used where electric motors are already part of the machine. For example, many gasoline/electric hybrid vehicles use electric motors as generators to charge electric batteries and also as regenerative brakes. Some diesel/electric train locomotives use electric motors to generate electricity which is then sent to the resistor bank and disposed of as heat. Some vehicles, such as some transit buses, do not yet have an electric motor but use a "retarder" secondary brake that is effectively a generator with an internal short circuit. The associated brake types are eddy current brakes, and electro-mechanical brakes (which are actually magnetically actuated friction brakes, but today are often simply called "electromagnetic brakes" as well).
Electromagnetic brakes slow down an object through electromagnetic induction, which creates resistance and in turn either heat or electricity. Friction brakes put pressure on two separate objects to slow the vehicle in control.
Characteristics
Brakes are often depicted according to several characteristics including:
- Peak Strength - Peak force is the maximum throttling effect that can be obtained. Peak strength is often greater than the limit of traction tires, in which case the brakes can cause the wheel to slip.
- Continuous power dissipation - The brakes are usually hot used, and fail when the temperature is too high. The largest amount of power (energy per unit time) that can be lost through the brakes without failure is the continuous power dissipation. Continuous power dissipation often depends on, for example, ambient cooling temperature and airspeed.
- Fade - When the brakes get heated up, this may be less effective, called a fading brake. Some designs inherently tend to fade, while other designs are relatively immune. Further, use considerations, such as cooling, often have a major effect on fading.
- Smooth - Brakes that are captured, pulses, have a chat, or otherwise exert different braking styles can cause a slip. For example, rail wheels have little grip, and friction brakes without an anti-skid mechanism often cause a slip, which increases maintenance costs and leads to "Buk Buk" feelings for the rider inside.
- Power - Brakes are often described as "powerful" when the power of a small human application leads to a higher braking force than is common for other brakes in the same class. This "strong" notion is not related to continuous power dissipation, and may be confusing because the brakes may be "strong" and strong brakes with soft brake applications, but have a lower peak power (worse) than a less "strong" brake.
- Pedal feel - Brake pedal feeling includes subjective perceptions of brake power output as a pedal travel function. Pedal travel is influenced by brake fluid displacement and other factors.
- Drag - Brakes have varying drag amounts in off-brake conditions depending on system design to accommodate total system compliance and deformation under braking with the ability to retract frictional material from inner friction off-brake conditions.
- Endurance - Friction brakes have surfaces that need to be updated regularly. Wear surfaces including brake shoes or pads, and also brake discs or drums. There may be sacrifices, for example a worn surface that produces high peak styles can also wear out quickly.
- Weight - Brakes often "add weight" because there are no other functions. Furthermore, the brakes are often mounted on wheels, and unsprung weight can significantly injure traction in some circumstances. "Weight" can mean the brakes themselves, or may include additional support structures.
- Noise - Brakes typically cause little glitches when applied, but often cause squealing or grinding sounds loud enough.
Foundation components
The foundation component is a brake-assembly component on the wheels of a vehicle, named to form the basis of the rest of the brake system. The mechanical parts contained around the wheel are controlled by the air brake system.
Three types of foundation brake system are "S" cam brakes, disc brakes, and wedge brakes.
Brake boost
Most modern vehicles use a vacuum-assisted brake system that greatly improves the force applied to vehicle brakes by the operator. This additional force is supplied by the vacuum manifold generated by the airflow blocked by the throttle on the engine running. This force is greatly reduced when the engine runs on the throttle fully open, since the difference between ambient air pressure and absolute (absolute) air pressure is reduced, and therefore the available vacuum is reduced. However, the brakes are rarely applied at full speed; the driver takes the right foot of the gas pedal and moves it to the brake pedal - unless the left foot braking is used.
Due to the low vacuum at high RPM, accidental acceleration reports are often accompanied by failed or weak brake complaints, because the high revving engine, having an open throttle, can not provide enough vacuum to power the brake booster. This problem is exacerbated on vehicles equipped with automatic transmissions because the vehicle will automatically lower the gear during brake applications, thereby increasing the torque delivered to the wheels driven in contact with the road surface.
Noise
Although ideally the brakes will turn all kinetic energy into heat, in practice significant amounts can be converted into acoustic energy instead, contributing to noise pollution.
For road vehicles, the noise generated varies significantly with the construction of tires, road surface, and deceleration. Noise can be caused by different things. These are signs that there may be a problem with an outdated brake over time.
Fire
Railway brake malware can cause sparks and cause forest fires.
Inefficiency
A large amount of energy is always lost during braking, even with less efficient regenerative braking. Therefore, an efficient energy usage metric while driving is to note how much braking is. If most of the decelerations come from unavoidable friction rather than braking, one of them suppresses most of the services of the vehicle. Minimizing the use of the brakes is one of the maximizing behaviors of fuel economy.
While energy is always lost during a brake event, the secondary factor affecting efficiency is "off-brake pull", or the obstacles that occur when the brakes are not accidentally moved. After the braking event, hydraulic pressure drops in the system, allowing the brake caliper piston to be pulled back. However, this retraction should accommodate all compliance in the system (under pressure) as well as thermal distortion of components such as disc brakes or brake systems will drag up contact with discs, for example, tapping the pads and pistons back from the surface rubbing. During this time, there can be significant brake resistance. Braking this brake can cause significant loss of parasitic power, thereby impacting fuel economy and overall vehicle performance.
See also
References
External links
- How to Work Stuff - Brakes
Source of the article : Wikipedia
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