eccentric

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eccentric

eccentric circles, with the center of each circle marked (Academy Artworks)

1. Departing from a recognized, conventional, or established norm or pattern. See synonyms at strange.
2. Deviating from a circular form or path, as in an elliptical orbit.
3. 1. Not situated at or in the geometric center.
   2. Having the axis located elsewhere than at the geometric center.

1. One that deviates markedly from an established norm, especially a person of odd or unconventional behavior.
2. Physics. A disk or wheel having its axis of revolution displaced from its center so that it is capable of imparting reciprocating motion.

[Middle English eccentrik, planetary orbit of which the earth is not at the center, from Medieval Latin eccentricus, not having the same center, from Greek ekkentros : ek-, out of; see ecto- + kentron, center (from kentein, to prick).]

adjective

Deviating from the customary: bizarre, cranky, curious, erratic, freakish, idiosyncratic, odd, outlandish, peculiar, quaint, queer, quirky, singular, strange, unnatural, unusual, weird. Slang kooky, screwball. British Slang rum, rummy². See usual/unusual.

noun

A person regarded as strange, eccentric, or crazy: crackpot, crazy, lunatic. Informal crank, loon, loony. Slang cuckoo, ding-a-ling, dingbat, kook, nut, screwball, weirdie, weirdo. See wise/foolish.

Definition: bizarre, unusual
Antonyms: boring, common, dull, normal, ordinary, plain, regular, standard, unexciting, usual

n

Definition: person who is bizarre, unusual
Antonyms: normal, standard

1. a deviation from the normal or conventional. adj 2. away from the central or reference position.

Not having the same center or center line.

eccentric head and shaft

Tutor's tip: "Acentric" means off-center, while "eccentric" describes someone who is interesting in a peculiar or abnormal way.

Eccentric sheave, with strap and eccentric rod fitted.

In mechanical engineering, an eccentric is a circular disk (eccentric sheave) solidly fixed to a rotating axle with its centre offset from that of the axle (hence the word "eccentric", out of the centre).^[1]

It is most often employed in steam engines and used to convert rotary into linear reciprocating motion in order to drive a sliding valve or a pump ram. In order to do so an eccentric usually has a groove at its circumference around which is closely fitted a circular collar (eccentric strap) attached to which an eccentric rod is suspended in such a way that its other end can impart the required reciprocating motion. A return crank fulfills the same function except that it can only work at the end of an axle or on the outside of a wheel whereas an eccentric can also be fitted to the body of the axle between the wheels. Unlike a cam, which also converts rotary into linear motion at almost any rate of acceleration and deceleration, an eccentric or return crank can only impart simple harmonic motion.

Contents 1 On bicycles 2 Gallery 3 See also 4 References

On bicycles

Eccentric bottom bracket on a Burley tandem bicycle held in place with two set screws

The term is also used to refer to the device often used on tandem bicycles with timing chains, single-speed bicycles with a rear disc brake or an internal-geared hub, or any bicycle with vertical dropouts and no derailleur, to allow slight repositioning, fore and aft, of a bottom bracket in order to properly tension the chain.^[2]

They may be held in place by a built-in wedge, set screws threaded into the bottom bracket shell, or pinch bolts that tighten a split bottom bracket shell.^[3]As a standard sized bottom bracket threads into the eccentric, an oversized bottom bracket shell is required to accommodate the eccentric.

Gallery

An animation of an eccentric sheave, with strap and eccentric rod fitted

Example of using eccentrics on a steam locomotive

See also

• Balance shaft
• Cam
• Crank (mechanism)
• Concentric
• Crankshaft
• Linkage (mechanical)

References

1. ^ Norton, Robert L. (2004), Design of machinery (3rd ed.), McGraw-Hill, ISBN 0072470461 .
2. ^ Brown, Sheldon. "Sheldon Brown's Bicycle Glossary E-F: Eccentric". Sheldon Brown. http://www.sheldonbrown.com/gloss_e-f.html. Retrieved 2007-06-09. 
3. ^ "Cannondale 1FG Easy Chain Tensioning". http://www.cannondale.com/bikes/03/ce/model-3mrss.html. Retrieved 2007-10-19. 

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Dansk (Danish)
adj. - excentrisk
n. - ikke cirkulær, aparte

Nederlands (Dutch)
excentriek(eling), excentrisch

Français (French)
adj. - excentrique, original, bizarre, (Math, Tech) excentrique
n. - excentrique, original, (Tech) excentrique

Deutsch (German)
n. - Exzentriker
adj. - exzentrisch

Ελληνική (Greek)
n. - ιδιότροπος (άνθρωπος), έκκεντρο
adj. - εκκεντρικός, ιδιότροπος, αλλόκοτος, παράξενος, έκκεντρος, παράκεντρος

Italiano (Italian)
eccentrico

Português (Portuguese)
n., -
adj. - excêntrico (m)

Русский (Russian)
чудак, оригинал, эксцентрик, эксцентричный

Español (Spanish)
adj. - excéntrico, excéntrica (tec.), estrafalario, estrambótico, extravagante, (geom) que no tiene el mismo centro, elíptico, que no está en el centro
n. - excéntrico, estrafalario, estrambótico, extravagante

Svenska (Swedish)
n. - excentrisk människa, original, särling, excenter (skiva) (mek.)
adj. - excentrisk, originell, excenter- (mek.)

中文（简体）(Chinese (Simplified))
古怪的, 不同圆心的, 反常的, 古怪的人, 偏心轮, 偏心圆

中文（繁體）(Chinese (Traditional))
adj. - 古怪的, 不同圓心的, 反常的
n. - 古怪的人, 偏心輪, 偏心圓

한국어 (Korean)
adj. - 보통이 아닌, 괴짜의, 중심을 달리하는
n. - 괴짜

日本語 (Japanese)
adj. - 普通でない, 一風変わった, 中心を異にする, 円でない
n. - 奇人

العربيه (Arabic)
‏(الاسم) شخص شاذ أو غريب الأطوار (صفه) شاذ, منحرف عن المركز‏

עברית (Hebrew)
adj. - ‮לא מעגלי, לא משותף-מרכז, מוזר וגחמני בהופעתו או בהתנהגותו‬
n. - ‮מתקן לשינוי תנועה מעגלית לתנועת קדימה-אחורה במנוע‬

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