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is sometimes used. The pawl bears against the surface at an angle so that any backward motion will cause the pawl to jam against the surface and thus prevent any further backward motion. Since the backward travel distance is primarily a function of the compressibility of the high friction surface,
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When the teeth are moving in the unrestricted (i.e. forward) direction, the pawl easily slides up and over the gently sloped edges of the teeth, with a spring forcing it (often with an audible 'click') into the depression between the teeth as it passes the tip of each tooth. When the teeth move in
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Because the ratchet can only stop backward motion at discrete points (i.e., at tooth boundaries), a ratchet does allow a limited amount of backward motion. This backward motion—which is limited to a maximum distance equal to the spacing between the teeth—is called
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breaking. When non-thermal forces (e.g. alternating pushes and pulls) are applied to an asymmetric substrate (e.g. an asymmetric gear), directed motion generically appears. This principle is known as the "Ratchet
Principle" or "Curie's Principle," after
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the opposite (backward) direction, however, the pawl will catch against the steeply sloped edge of the first tooth it encounters, thereby locking it against the tooth and preventing any further motion in that direction.
170:) is a mechanical device that allows continuous linear or rotary motion in only one direction while preventing motion in the opposite direction. Ratchets are widely used in machinery and tools. The word
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While the ratchets referenced in statistical physics are typically at the molecular or microscopic scales, the concept was inspired by the ratchet and pawl in its introductions by
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For safety reasons, the ring has a ratchet, so it cannot be misadjusted in the counter-clockwise direction, and would not lead to
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Red arrows indicate which way force is applied to the gear rack. The rack and pawl are both restricted to only
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225:. In cases where backlash must be minimized, a smooth, toothless ratchet with a high friction surface such as
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Ratchet mechanisms are used in a wide variety of applications, including these:
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19:"Ratchet mechanism" redirects here. For the muscle ratchet mechanism, see
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A ratchet featuring a gear (1) and pawl (2) mounted on a base (3)
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this mechanism can result in significantly reduced backlash.
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Red arrows indicate which way force is applied to the gear.
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with teeth, and a pivoting, spring-loaded finger called a
546:"Brownian motors: noisy transport far from equilibrium"
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Animation of ratchet gear rack (green) and pawl (pink).
56:. Unsourced material may be challenged and removed.
556:(2–4): 57–265 – via Elsevier Science Direct.
132:Animation of ratchet gear (green) and pawl (pink).
174:is also used informally to refer to a ratcheting
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522:. British Horological Institute. Archived from
16:Gear and pawl; prevents motion in one direction
242:, the concept of a ratchet, often termed a "
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116:Learn how and when to remove this message
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54:adding citations to reliable sources
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516:"Know your terminology – Clocks"
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402:, also known as a 'come-along.'
41:needs additional citations for
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186:A ratchet consists of a round
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544:Reimann, Peter (April 2002).
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445:to the start time of a dive.
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414:The ratchet mechanism of a
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573:Mechanisms (engineering)
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248:time-reversal symmetry
234:In theoretical physics
166:(occasionally spelled
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21:Sliding filament model
329:Anti-rollback devices
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65:"Ratchet" device
450:harmful consequences
310:(overrunning clutch)
50:improve this article
504:hautehorlogerie.org
264:Marian Smoluchowski
252:left-right symmetry
240:statistical physics
182:Theory of operation
303:Computer keyboards
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353:Tie down straps
348:Socket wrenches
333:roller coasters
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268:Richard Feynman
238:In theoretical
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156:linear movement
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106:November 2023
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61:Find sources:
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39:This article
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528:. Retrieved
524:the original
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474:Sprag clutch
443:diving watch
437:Setting the
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257:Pierre Curie
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206:asymmetrical
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190:or a linear
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158:(not shown).
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48:Please help
43:verification
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479:Check valve
386:or spanner.
382:Ratcheting
363:Typewriters
314:Grease guns
530:2008-05-15
492:References
358:Turnstiles
343:Slacklines
283:Cable ties
76:newspapers
469:Freewheel
416:cable tie
319:Handcuffs
308:Freewheel
567:Category
458:See also
331:used in
288:Capstans
223:backlash
216:Backlash
369:Gallery
172:ratchet
164:ratchet
90:scholar
298:Clocks
227:rubber
168:rachet
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485:Diode
441:of a
439:bezel
400:hoist
338:Looms
324:Jacks
202:click
97:JSTOR
83:books
274:Uses
266:and
200:(or
197:pawl
192:rack
188:gear
69:news
554:361
52:by
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