Dictionary:

clutch¹

  (klŭch)

1. To grasp and hold tightly.
2. To seize; snatch.

1. To attempt to grasp or seize: clutch at a life raft.
2. To engage or disengage a motor vehicle's clutch.

1. A hand, claw, talon, or paw in the act of grasping.
2. A tight grasp.
3. Control or power. Often used in the plural: caught in the clutches of sin.
4. A device for gripping and holding.
5. 1. Any of various devices for engaging and disengaging two working parts of a shaft or of a shaft and a driving mechanism.
   2. The apparatus, such as a lever or pedal, that activates one of these devices.
6. A tense, critical situation: came through in the clutch.
7. A clutch bag.

1. Being or occurring in a tense or critical situation: won the championship by sinking a clutch putt.
2. Tending to be successful in tense or critical situations: The coach relied on her clutch pitcher.

[Middle English clucchen, from Old English clyccan.]

1. The complete set of eggs produced or incubated at one time.
2. A brood of chickens.
3. A group; a bunch.

To hatch (chicks).

[Variant of dialectal cletch; akin to Middle English clekken, to hatch, from Old Norse klekja.]

A machine element for the connection and disconnection of shafts in equipment drives. If both shafts to be connected can be stopped or made to move relatively slowly, a positive-type mechanical clutch may be used. If an initially stationary shaft is to be driven by a moving shaft, friction surfaces must be interposed to absorb the relative slippage until the speeds are the same. Likewise, friction slippage allows one shaft to stop after the clutch is released.

When positive connection of one shaft with another in a given position is needed, a positive clutch is used. This clutch is the simplest of all shaft connectors, sliding on a keyed shaft section or a splined portion and operating with a shift lever on a collar element. Because it does not slip, no heat is generated in this clutch. Interference of the interlocking portions prevents engagement at high speeds; at low speeds, if connection occurs, shock loads are transmitted to the shafting. Positive clutches may be of the square jaw type (Fig. 1) with two or more jaws of square section meshing together in the opposing clutches, or the spiral jaw type, a modification of the square-jaw clutch that permits more convenient engagement and provides a more gradual movement of the mating faces toward each other.

Square-jaw-type positive clutch.

When the axial pressure of the clutch faces on each other serves to transmit torque instead of the mating shape of their parts, the clutch operates by friction. This friction clutch is usually placed between an engine and a load to be driven; when the friction surfaces of the clutch are engaged, the speed of the driven load gradually approaches that of the engine until the two speeds are the same. A friction clutch is necessary for connecting a rotating shaft of a machine to a stationary shaft so that it may be brought up to speed without shock and transmit torque for the development of useful work. The three common designs for friction clutches, combining axial and radial types, are cone clutches (Fig. 2), disk clutches, and rim clutches. In a cone clutch, the surfaces are sections of a pair of cones. The disk clutch consists essentially of one or more friction disks connected to a driven shaft by splines. A rim clutch has surface elements that apply pressure to the rim externally or internally.

Cone-type friction clutch.

In the overrunning type of clutch, the driven shaft can run faster than the driving shaft. This action permits freewheeling as the driving shaft slows down or another source of power is applied. Effectively this is a friction pawl-and-ratchet drive, wherein balls or rollers become wedged between the sleeve and recessed pockets machined in the hub (Fig. 3). The clutch does not slip when the second shaft is driven, and is released automatically when the second shaft runs faster than the driver. The centrifugal clutch employs centrifugal force from the speed of rotation. This type of clutch is not normally used because it becomes unwieldy and unsafe with increasing size. Clutch action is also produced by hydraulic couplings, with a smoothness not possible with a mechanical clutch. Automatic transmissions in automobiles represent a fundamental use of hydraulic clutches. See also Coupling; Torque converter.

Overrunning clutch with spring-constrained rollers or balls.

Magnetic coupling between conductors provides a basis for several types of clutches. The magnetic attraction between a current-carrying coil and a ferromagnetic clutch plate serves to actuate a disk-type clutch. Slippage in such a clutch produces heat that must be dissipated and wear that reduces the life of the clutch plate. Thus the electromagnetically controlled disk clutch is used to engage a load to its driving source. See also Brake; Coupling.

verb

1. To take firmly with the hand and maintain a hold on: clasp, clench, grab, grapple, grasp, grip, seize. See keep/release.
2. To get hold of (something moving): catch, grab, seize, snatch. Informal nab. Idioms: lay hands on. See get/lose.

noun

1. The act of catching, especially a sudden taking and holding: catch, grab, seizure, snatch. See get/lose.
2. An act or means of holding something: clasp, clench, grasp, grip, hold. Sports grapple. See keep/release.

noun

A number of individuals making up or considered a unit: array, band, batch, bevy, body, bunch, bundle, clump, cluster, collection, group, knot, lot, party, set. See group.

Definition: grab, hold, snatch
Antonyms: let go, let loose, loose, unfasten

A device made for gripping the teeth in a dental arch, to which face-bows or tracing devices may be attached rigidly enough to behave in space relations during the movements as if they were jaw outgrowths.

For more information on clutch, visit Britannica.com.

A device which permits the drive train of a machine to be connected to, or disconnected from, a prime source of power; usually operates on a mechanical principle with friction surfaces that can be joined or separated, but other types include a fluid coupler.

clustered pier

1. the number of eggs laid by a hen on consecutive days in an uninterrupted series. Clutch lengths vary from 2 to 6 days but may be as many as 360.
2. a setting of eggs.
3. a group of chickens hatched by a hen from a setting of eggs.

Flywheel

Clutch for a drive shaft: The clutch disc (center) spins with the flywheel (left). To disengage, the lever is pulled (black arrow), causing a white pressure plate (right) to disengage the green clutch disc from turning the drive shaft, which turns within the thrust-bearing ring of the lever. At rest, all 3 rings connect, with no gaps.

Rear side of a Ford V6 engine, looking at the clutch housing on the flywheel

Single, dry, clutch friction disc. The splined hub is attached to the disc with springs to damp chatter.

A clutch is a mechanism for transmitting rotation, which can be engaged and disengaged. Clutches are useful in devices that have two rotating shafts. In these devices, one shaft is typically driven by a motor or pulley, and the other shaft drives another device. In a drill, for instance, one shaft is driven by a motor, and the other drives a drill chuck. The clutch connects the two shafts so that they can either be locked together and spin at the same speed, or be decoupled and spin at different speeds.

Vehicle clutches

There are many different vehicle clutch designs but most are based on one or more friction discs, pressed tightly together or against a flywheel using springs. The friction material varies in composition depending on whether the clutch is dry or wet, and on other considerations. Friction discs once contained asbestos, but this has been largely eliminated. Clutches found in heavy duty applications such as trucks and competition cars use ceramic clutches that have a greatly increased friction coefficient, however these have a "grabby" action and are unsuitable for road cars. The spring pressure is released when the clutch pedal is depressed thus either pushing or pulling the diaphragm of the pressure plate, depending on type, and the friction plate is released and allowed to rotate freely.

When engaging the clutch, the engine speed may need to be increased from idle, using the manual throttle, so that the engine does not stall (although in most cars, especially diesels, there is enough power at idling speed that the car can move. This requires fine control of the clutch). However, raising the engine speed too high while engaging the clutch will cause excessive clutch plate wear. Engaging the clutch abruptly when the engine is turning at high speed causes a harsh, jerky start. This kind of start is desired in drag racing and other competitions, however.

Wet and dry clutches

A 'wet clutch' is immersed in a cooling lubricating fluid, which also keeps the surfaces clean and gives smoother performance and longer life. Wet clutches, however, tend to lose some energy to the liquid. A 'dry clutch', as the name implies, is not bathed in fluid. Since the surfaces of a wet clutch can be slippery (as with a motorcycle clutch bathed in engine oil), stacking multiple clutch disks can compensate for slippage. Most Moto Guzzi, Ducati, and BMW motorcycles typically use a dry clutch much like a car.

Clutch operation in automobiles

In a car the clutch is operated by the left-most pedal using hydraulics or a cable connection from the pedal to the clutch mechanism. Even though the clutch may physically be located very close to the pedal, such remote means of actuation are necessary to eliminate the effect of slight engine movement, engine mountings being flexible by design. With a rigid mechanical linkage, smooth engagement would be near-impossible, because engine movement inevitably occurs as the drive is "taken up". No pressure on the pedal means that the clutch plates are engaged (driving), while depressing the pedal disengages the clutch plates, allowing the driver to shift gears or coast.

A manual transmission contains cogs for selecting gears. These cogs have matching teeth, called dog teeth, which means that the rotation speeds of the two parts have to match for engagement. This speed matching is achieved by a secondary clutch called a synchronizer, a device that uses frictional contact to bring the two parts to the same speed, and a locking mechanism called a blocker ring to prevent engagement of the teeth (full movement of the shift lever into gear) until the speeds are synchronized.

Non-powertrain clutches in automobiles

There are other clutches found in a car. For example, a belt-driven engine cooling fan may have a clutch that is heat-activated. The driving and driven elements are separated by a silicone-based fluid. When the temperature is low, the fluid is thin and so the clutch slips. When the temperature is high, the fluid thickens, causing the fan to spin. There are also electronically engaged clutches (such as for an Air conditioning compressor) that use magnetic force to lock the pulley and compressor together.

Clutch operation in motorcycles

On most motorcycles, the clutch is operated by the clutch lever, located on the left handlebar. No pressure on the lever means that the clutch plates are engaged (driving), while pulling the lever back towards the rider will disengage the clutch plates, allowing the rider to shift gears. Motorcycle clutches are usually made up of a stack of alternating plain steel and friction plates. One type of plate has lugs on its inner diameter that key it to the engine crankshaft, while the other type of plate has lugs on its outer diameter that key it to a basket that turns the transmission input shaft. The plates are forced together by a set of coil springs when the clutch is engaged. Racing motorcycles often use slipper clutches to eliminate the effects of engine braking.

Centrifugal clutches

Some cars and mopeds have a centrifugal clutch, using centrifugal effects to engage the clutch above certain rpm, see Saxomat.

Other clutches

• Dog clutches
• Cone clutches
• Safety clutches: These devices allow a rotating shaft to "slip" when higher than normal resistance is encountered on a machine. An example of a safety clutch is the one mounted on the driving shaft of a large grass mower. The clutch will "slip" or "give" if the blades hit a rock, stump, or other immobile object.
• Overrunning clutch or freewheel
• Single plate & Multi-plate friction clutches
  • Single plate: This type of clutch is used almost exclusively in vehicles and has three main parts:
    • (i) Driving members
    • (ii) Driven members
    • (iii)operating members
• Centrifugal clutch and semi-centrifugal clutch
• Hydraulic clutch
• Electromagnetic clutch

See also

• Clutch (band)
• Riding the clutch

External links

• HowStuffWorks has a detailed explanation of the working of a clutch.

Wikimedia Commons has media related to:

Category:Couplings

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.
v. tr. - gribe hårdt fat i, hage sig fast i
v. intr. - klynge sig til
n. - hårdt greb, kløer, kobling, kuld
adj. - koblings-, til at holde i hånden

idioms:

• clutch at a straw    gribe efter et halmstrå

2.
n. - kuld, redefuld
v. tr. - gribe

Nederlands (Dutch)
(vast)grijpen, vaste greep, koppeling, (mv) de greep van een wrede macht, broed

Français (French)
1.
v. tr. - saisir, étreindre, s'agripper
v. intr. - s'agripper, se cramponner à qch
n. - (Aut) embrayage, action de saisir, griffe (d'un animal), serre (d'un oiseau de proie), (US) moment difficile
adj. - fait en situation de crise, fiable en situation de crise

idioms:

• clutch at a straw    (fig) se raccrocher à n'importe quoi

2.
n. - couvée
v. tr. - faire éclore (des poussins)

Deutsch (German)
1.
v. - fassen, sich anklammern, umklammern, ergreifen, greifen nach, ein/auskuppeln
n. - Klauen, Umklammerung, Kupplung, Griff
adj. - in einer kritischen Situation gemacht

idioms:

• clutch at a straw    sich an einen Strohhalm klammern

2.
n. - Brut, Gelege
v. - ausbrüten

Ελληνική (Greek)
v. - πιάνω, γραπώνω, αρπάζω, συλλαμβάνω, τσακώνω, κάνω να πιάσω, προσπαθώ να αρπάξω
n. - πιάσιμο, λαβή, άδραγμα, άρπαγμα, (μηχαν.) συμπλέκτης, αμπραγιάζ, επώαση, κλώσημα, σμάρι, σμήνος, (πληθ.) αρπάγη, νύχια

idioms:

• clutch at a straw    πιάνομαι απ' όπου βρω

Italiano (Italian)
afferrare, aggrapparsi, frizione, pedale della frizione, nidiata, covata

Português (Portuguese)
v. - agarrar, embrear, incubar ovos
n. - garra (f), apresamento (m), ninhada (f), embreagem (f) (Téc.)

Русский (Russian)
хватать, цепляться, сцепление, выводок, группа, скопление

Español (Spanish)
1.
v. tr. - agarrar, embragar, tratar de asir
v. intr. - agarrarse a, tratar de asir, usar el embrague
n. - pedal de embrague, embrague, agarre
adj. - agarrado, asido, embragado

idioms:

• clutch at a straw    agarrarse a un clavo ardiendo, agarrarse de un pelo

2.
n. - nidada
v. tr. - poner huevos, desovar

Svenska (Swedish)
v. - gripa, sluta
n. - hårt grepp, koppling (tekn.), kona, klo, äggrede, kycklingkull

中文（简体） (Chinese (Simplified))
1. 抓住, 攫取, 抓, 攫, 爪子, 掌握, 控制, 手, 抓住的, 攫取的

idioms:

• clutch at a straw    捞稻草, 做最后绝命的挣扎

2. 一窝蛋, 一窝雏鸡, 孵

中文（繁體） (Chinese (Traditional))
1.
n. - 一窩蛋, 一窩雛雞
v. tr. - 孵

2.
v. tr. - 抓住, 攫取
v. intr. - 抓, 攫
n. - 爪子, 掌握, 控制, 手, 抓住
adj. - 抓住的, 攫取的

idioms:

• clutch at a straw    撈稻草, 做最後絕命的掙扎

한국어 (Korean)
1.
v. tr. - ~을 꽉 잡다, 매혹하다
v. intr. - 잡으려 들다, 자동차의 클러치를 조작하다
n. - 붙잡음, 위기, 클러치
adj. - 손잡이가 없는, 핀치에 강한

2.
n. - 한 번에 품은 알, 한 배에 깐 병아리
v. tr. - 새끼를 부화하다

日本語 (Japanese)
n. - しっかりつかむこと, 把握, 手中, 危機, クラッチ, 卵
v. - ぐいと掴む

العربيه (Arabic)
‏(فعل) قبض على, أمسك, كمش (الاسم) جهاز تعشيق تروس, الحركه, قابض, كلاتش, دبرياج, قبضه‏

עברית (Hebrew)
v. tr. - ‮אחז, לפת, תפס‬
v. intr. - ‮ניסה לתפוס או לאחוז, להיעשות מתוח מפחד (מדוברת)‬
n. - ‮לפיתה, אחיזה, מצמד, מזווג, בריכה‬
adj. - ‮שניתן לסמוך עליו במצבים מכריעים, שהושג ברגע קריטי‬
n. - ‮קבוצת אפרוחים, מדגר‬
v. tr. - ‮דגרה (תרנגולת)‬

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