Brake

Brakes are used to reduce or limit the speed of moving machinery or vehicles. They work mostly by the conversion of the supplied kinetic energy by friction into heat energy. In contrast to the regenerative braking thereby losing the kinetic energy for locomotion. Brakes are used as a machine element closely with clutches and the brake is a special coupling, in which is fixed a page. In this respect, many brake types of couplings can be derived. Vehicles within the meaning of the Road Traffic have a dual circuit braking system in Germany, so possess two independently functioning brakes.

The types of brakes in vehicles by far the most commonly used are the disc brake and drum brake, an evolved form of the block brake. Usually a brake to reduce the rotational speed of rotating parts will be used. But many of the listed principles can also be used to reduce a linear movement when the designs are slightly different.

In part, the nature of the operation of the brake is used for categorizing. However, for example, the term air brake, hydraulic brake or cable brake says nothing about the design from, but only kind of power transmission to the mechanical actuating elements.

Brake horsepower

The braking power depends on the braking force, and the instantaneous speed, and is fully converted into heat.

With

Physically, is converted into heat energy with a brake, the kinetic energy () is a decelerated to the velocity difference () (or delayed ) physical mass (m) To note that the speed square in the calculation:

Due to the specific heat capacity of the brake heats it on continuously. Keep you Cool the heat radiation according to the Stefan- Boltzmann law, the heat convection by wind or blower with variable heat transfer coefficient and the heat conduction through the connecting elements ( conduction ).

An example calculation for heating of a disc brake contains the main articles brake disc.

Mechanical brakes

All mechanical brakes are grinding brakes and are based on reducing a motion by friction between a fixed and moving bodies.

Scratch brake

Since the earliest days of the principle of the scratch brake is known. A lever is attached to or trapped in that the ( possible ) shorter pieces to the floor and the longer piece to the operator displays on a vehicle. By tightening the brake lever, the short lower end is pressed over leverage in the ground and so slows down the vehicle. This technique was popular for a long time and is still used, for example, when sledge, sports equipment or kids vehicles.

Hindrance

The stumbling block represents a primitive form of block brake

Block brake

The vast number of all brakes used in the 20th century in land vehicles can be assigned to the principle of block brake. Spindle brakes on historic carriages have, for example, brake pads made ​​of linden wood.

Shoe brake

The shoe brake is a mechanical brake in which a rotating cylinder is slowed from the outside by means of pressed- brake pads.

Drum brake

The drum brake has a cylindrical rotating body ( drum), are pressed against the braking by internal or external, fixed brake shoes. The operation of the brake pads is usually done by hydraulic cylinder inside the drum or rotating eccentric bolt from the outside. Depending on the design more types can be distinguished.

Disc brake

The disc brake comprises a follower on said shaft brake disc, the brake pads are pressed from both sides. Such brakes are found today in all popular vehicles such as cars, trucks, motorcycles, bicycles and even on trains.

Wet brake

A sub-category of the disk brake, the wet brake ( often referred to as "wet brake "). Here rotates one (or more by intermediate slices separated ) brake disc (s ) which are slowed down by friction with the pressure plate, friction ring (outside) and the washers in an oil bath. The pressing is effected by a pressure plate which consists of two discs. Between the plates balls are mounted in elongated, shallow depressions becoming. Due to the rotation of the two disks each other, which thereby move toward or away at each other, the contact pressure is adjusted to the brake pad and shims.

The oil serving for transporting the heat energy. Advantage of this system is that it is thermally stable (no fading) and very low wear and thus maintenance. In addition, no brake dust forms. Disadvantages are the, in the event of a repair, usually high cost. These types of brakes can be found partly in tractors and quads. The wet brake is artverwandt me the wet clutch, which is widely used in motorcycles.

Wedge brake

The electronically controlled wedge brake (type of disc brake ) a small electric motor pushes a brake pad having a wedge-shaped back profile between the brake pads and the brake disc.

In the conventional wedge brake ( used in horse-drawn carriages ) rams the coachman drive a wedge between the wheel and the wheel arch.

Magnetic brake

For magnetic rail brakes, a brake pad is pressed by magnetic force to the rail on which the vehicle travels.

Band brake

The band brake is also a mechanical brake, in which, however, in contrast to the back brake, a belt is wrapped around a drum.

Centrifugal brake

Centrifugal brakes are usually not directly a severe reduction in the number of revolutions, but the boundary of the same. They operate on the same principle as centrifugal clutches. A common use is to limit the reverse rotation speed rotary phone, called the number switch.

Retarder

Track brakes are on the track body, such as marshalling yards, built-in.

Electric brakes

• Eddy current brake - It uses the eddy current effect. It receives an electrically conductive material (usually a metal plate ) is moved by a magnetic field. This electrical eddy currents are induced in the material. These in turn produce a magnetic field that opposes the torque produced. The disc is braked by it.
• Electric motor brake - the drive motor is used when braking as a generator. In modern generator brakes the energy generated is fed back into the power grid (rail vehicles and trolleybuses ) and an energy storage device ( electric cars ). This process is also known as recuperation.
• Dynamic brake - the current generated by the generator is converted into heat by electric resistances.

Magnetic brakes

• The Magnetarder works on the eddy current principle without additional auxiliary power.

• The hysteresis effect of the use of a magnet or electromagnet to a moving ferromagnetic material. The energy loss is caused by the repeated reversal of magnetization of the material. In contrast to the eddy current brake, the force generated / torque is generated in the hysteresis is not rate- and speed- dependent.

• Magnetic particle brake - by applying a magnetic field using a coil, a magnetic powder is pressed to the moving member to be braked and stiffened, whereby a braking action is produced.

• The magnetic brake for rail vehicles combines the action of a frictional or block brake and eddy current brake.

Flow brakes, brake fluid

• A retarder using the viscosity of a liquid ( oil) in order to slow the rotational movement of a shaft. The retarder operates wear-free and is therefore often used as a retarder in trucks or buses. In the latter, also, because it can be virtually free of steps, ie controlled smoothly in its delay performance.
• In high-speed vehicles, in particular the aerospace, parachutes and air brakes are used to increase the air resistance and reduce the speed. When Mercedes -Benz SLR McLaren or Bugatti Veyron 16.4, for example, is employed by a rapid deceleration of the rear spoiler by 65 degrees around through a vortex, an increase of Cw - value and so a better delay and a higher Heckanpressdruck (and thus increased braking performance of the to reach the rear wheels ) (see also air brakes).
• Example of an air brake is also the porch in the striking works of Clocks.
• Water eddy brakes are one of the power brakes for stationary test, such as engine test stands. They are used for braking a device under test ( combustion engine, electric motor or other drives).
• Drag anchor or tow lines reduce the speed of boats and ships in rough seas or in emergencies

Compared engine brake

In certain light rail vehicles (for example, steam locomotives with Riggenbach counter-pressure brake), aircraft and ships to brake the drive is switched or deflected in the opposite direction. For aircraft, this is referred to as the thrust reverser. Even with boats and ships, the principle of reverse thrust is used for braking.

Brakes on the application

• Overrun brake
• Automatic brake
• Brake ( railway)
• Brake ( motor vehicle )
• Retarder
• Bicycle brake
• Parking brake
• Stop brake