(brāk)

(mechanical engineering) A machine element for applying friction to a moving surface to slow it (and often, the containing vehicle or device) down or bring it to rest.

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A machine element for applying a force to a moving surface to slow it down or bring it to rest in a controlled manner. In doing so, it converts the kinetic energy of motion into heat which is dissipated into the atmosphere. Brakes are used in motor vehicles, trains, airplanes, elevators, and other machines. Most brakes are of a friction type in which a fixed surface is brought into contact with a moving part that is to be slowed or stopped.

Friction brakes are classified according to the kind of friction element employed and the means of applying the friction forces. See also Friction.

The single-block is the simplest form of brake. It consists of a short block fitted to the contour of a wheel or drum and pressed against its surface by means of a lever on a fulcrum, as widely used on railroad cars. The block may have the contour lined with friction-brake material, which gives long wear and a high coefficient of friction. The fulcrum may be located with respect to the lever in a manner to aid or retard the braking torque of the block. The lever may be operated manually or by a remotely controlled force (Fig. 1a).

operating lever; force in the direction of the top arrow applies the brake. (b) Double-block brake. The blocks are pivoted on their levers; force in the direction of the arrow releases the brake. (c) External shoe brake. Shoes are lined with friction material. (d) Internal shoe brake with lining.">
Brakes. (a) Single-block brake. The block is fixed to the operating lever; force in the direction of the top arrow applies the brake. (b) Double-block brake. The blocks are pivoted on their levers; force in the direction of the arrow releases the brake. (c) External shoe brake. Shoes are lined with friction material. (d) Internal shoe brake with lining.

In double-block brakes, two single-blocks brake in symmetrical opposition, where the operating force on the end of one lever is the reaction of the other, make up a double-block brake (Fig. 1b). External thrust loads are balanced on the rim of the rotating wheel.

An external-shoe brake operates in the same manner as the block brake, and the designation indicates the application of externally contracting elements. In this brake the shoes are appreciably longer, extending over a greater portion of the drum (Fig. 1c). This construction allows more combinations for special applications than the simple shoe, although assumptions of uniform pressure and concentrated forces are no longer possible. In particular, it is used on elevator installations for locking the hoisting sheave by means of a heavy spring when the electric current is off and the elevator is at rest. See also Elevator.

An internal shoe brake has several advantages over an external shoe. Because the internal shoe works on the inner surface of the drum, it is protected from water and grit (Fig. 1d). It may be designed in a more compact package, is easily activated, and is effective for drives with rotations in both directions. The internal shoe is used in the automotive drum brake, with hydraulic piston actuation. See also Automotive brake.

Hoists, excavating machinery, and hydraulic clutch-controlled transmissions have band brakes. They operate on the same principle as flat belts on pulleys. In the simplest band brake, one end of the belt is fastened near the drum surface, and the other end is then pulled over the drum in the direction of rotation so that a lever on a fulcrum may apply tension to the belt.

Disk brakes have long been used on hoisting and similar apparatus. Because more energy is absorbed in prolonged braking than in clutch startup, additional heat dissipation must be provided in equivalent disk brakes. Disk brakes are used for the wheels of aircraft, where segmented rotary elements are pressed against stationary plates by hydraulic pistons. Flexibility, self-alignment, and rapid cooling are inherent in this design. Another application is the bicycle coaster brake.

The caliper disk brake (Fig. 2) is widely used on automotive vehicles. It consists of a rotating disk which can be gripped between two friction pads. The caliper disk brake is hydraulically operated, and the pads cover between one-sixth and one-ninth of the swept area of the disk. See also Automotive brake.

Caliper disk brake. (a) Friction pads on either side of a disk that is free to rotate. (b) Brake applied, hydraulic pressure forces the pistons toward the disk to stop its rotation and hold it stationary. (Automotive & Technical Writing, Charlottesville, Virginia)

Railway brakes are normally applied air brakes; if the air coupling to a car is broken, the brakes are applied automatically. To apply the brakes, the brake operator releases the compressed air that is restraining the brakes by means of a diaphragm and linkage. Over-the-road trucks and buses use air brakes. Another form of air brake consists of an annular air tube surrounding a jointed brake lining that extends completely around the outside of a brake drum. Air pressure expands the tube, pressing the lining against the drum.

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noun

An instrument or means of restraining: bit, bridle, leash, restraint, snaffle. See restraint/unrestraint.

verb

To control, restrict, or arrest: bit, bridle, check, constrain, curb, hold, hold back, hold down, hold in, inhibit, keep, keep back, pull in, rein (back, in. or up), restrain. See restraint/unrestraint.

n

Definition: stopping device; check
Antonyms: accelerator

v

Definition: check; stop
Antonyms: accelerate, move, start

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For more information on brake, visit Britannica.com.

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IN BRIEF: A device used to slow down or stop.

As I coasted down the long hill on my bike, I had to use the brakes to keep from going too fast.

Tutor's tip: He did not want to "brake" (use the brake, a device for slowing or stopping motion) when he came to the "break" (place where a separation occurs) in the road.

This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)

Dansk (Danish)
1.
n. - bremse
v. tr. - bremse
v. intr. - bremse

2.
n. - brage, brydebænk
v. tr. - brage, bryde

3.
n. - stang

4.
n. - bregne

5.
n. - krat, bevoksning

Nederlands (Dutch)
rem, vertragende factor, stationwagen, adelaarsvaren, kreupelhout, eg, remmen, afremmen, (vlas)braken

Français (French)
1.
n. - (Aut, etc) frein, (fig) frein à
v. tr. - (lit, fig) freiner
v. intr. - (lit, fig) freiner

2.
n. - fourche (pour broyer le lin)
v. tr. - (Tex) broyer (le lin, etc)

3.
n. - pompe

4.
n. - (Bot) fougère

5.
n. - fourré

Deutsch (German)
1.
n. - Bremse, Bremspedal
v. - bremsen

2.
n. - (Tech) Flachsbreche, Bracke
v. - (Flachs) brechen

3.
n. - Pumpenschwengel, Hebelarm

4.
n. - Adlerfarn

5.
n. - Unterholz, Dickicht

Ελληνική (Greek)
v. - φρενάρω, πατώ φρένο
n. - φρένο, (τροχο)πέδη

idioms:

• air brake    αερόφρενο

Italiano (Italian)
frenare, freno a mano, pedale del freno, freno

Português (Portuguese)
v. - frear, retardar
n. - freio (m)

Русский (Russian)
тормозить, тормоз, тормоза

Español (Spanish)
1.
n. - freno, pedal del freno
v. tr. - frenar
v. intr. - frenarse

2.
n. - agramadera
v. tr. - agramar

3.
n. - manija de bomba

4.
n. - tipo de helecho

5.
n. - matorral

Svenska (Swedish)
v. - bromsa, bråka
n. - broms, bromspedal, buskage, bräken

中文（简体） (Chinese (Simplified))
1. 煞车, 煞住, 抑制, 约束, 制动

2. 揉碎机, 揉面机, 麻梳, 重型耙, 揉碎

3. 阻碍, 约束

4. 草丛, 灌木丛

5. 蕨, 羊齿类

6. 泵柄, 泵杆

中文（繁體） (Chinese (Traditional))
1.
n. - 草叢, 灌木叢

2.
n. - 泵柄, 泵杆

3.
n. - 蕨, 羊齒類

4.
n. - 煞車
v. tr. - 煞住, 抑制, 約束
v. intr. - 煞車, 制動

5.
n. - 阻礙, 約束

6.
n. - 揉碎機, 揉面機, 麻梳, 重型耙
v. tr. - 揉碎

한국어 (Korean)
1.
n. - 브레이크
v. tr. - ~에 브레이크를 걸다
v. intr. - 브레이크를 걸다

2.
n. - 아마를 으깨어 섬유를 분리해 내는 기구
v. tr. - ~을 으깨어 섬유를 분리해 내다

3.
n. - 펌프의 자루

4.
n. - 양치류

5.
n. - 덤불

日本語 (Japanese)
n. - ブレーキ, 制動機, 歯止め, やぶ, ワラビ
v. - ブレーキをかける

العربيه (Arabic)
‏(فعل) أوقف, كبح, فرمل (الاسم) الكابح, البريك, الفرامل, جهاز أيقاف السيارة, سيارة كبيرة‏

עברית (Hebrew)
n. - ‮בלם, מעצור, סבך, איזור שיחים, כרכרה‬
v. tr. - ‮בלם, עצר‬
v. intr. - ‮בלם, עצר‬
n. - ‮כלי לניפוץ פשתן וקנבוס‬
v. tr. - ‮ניפץ (פשתן)‬
n. - ‮סוג של ידית-משאבה‬
n. - ‮סוג של שרך‬
n. - ‮סבך-יער‬

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brake	brake pads
Brake Pad	brake switch