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 center).[1]
Eccentric sheave, with strap and eccentric rod fitted
It is used most often in steam engines, and used to convert rotary motion into linear reciprocating motion to drive a sliding valve or pump ram. To do so, an eccentric usually has a groove at its circumference closely fitted a circular collar (eccentric strap). An attached 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 an approximation of simple harmonic motion.
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.
Galleryedit
An animation of an eccentric sheave, with strap and eccentric rod fitted
Example of using eccentrics on a steam locomotive
See alsoedit
Wikimedia Commons has media related to Eccentrics.
Balance shaft – Weights used to balance otherwise unbalanced engine movement
Cam (mechanism) – Rotating or sliding component that transmits variable motion to a follower
Crank (mechanism) – Simple machine transferring motion to or from a rotating shaft at a distance from the centreline
^. Archived from the original on 2007-11-23. Retrieved 2007-10-19.
January 01, 1970
eccentric, mechanism, mechanical, engineering, eccentric, circular, disk, eccentric, sheave, solidly, fixed, rotating, axle, with, centre, offset, from, that, axle, hence, word, eccentric, center, eccentric, sheave, with, strap, eccentric, fitted, used, most, . 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 center 1 Eccentric sheave with strap and eccentric rod fitted It is used most often in steam engines and used to convert rotary motion into linear reciprocating motion to drive a sliding valve or pump ram To do so an eccentric usually has a groove at its circumference closely fitted a circular collar eccentric strap An attached 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 an approximation of simple harmonic motion Contents 1 On bicycles 2 Gallery 3 See also 4 ReferencesOn bicycles edit nbsp 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 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 edit nbsp An animation of an eccentric sheave with strap and eccentric rod fitted nbsp Example of using eccentrics on a steam locomotiveSee also edit nbsp Wikimedia Commons has media related to Eccentrics Balance shaft Weights used to balance otherwise unbalanced engine movement Cam mechanism Rotating or sliding component that transmits variable motion to a follower Crank mechanism Simple machine transferring motion to or from a rotating shaft at a distance from the centreline Concentric objects Geometric objects with a common centre Crankshaft Mechanism for converting reciprocating motion to rotation Linkage mechanical Assembly of systems connected to manage forces and movementReferences edit Norton Robert L 2004 Design of machinery 3rd ed McGraw Hill ISBN 0 07 247046 1 Brown Sheldon Sheldon Brown s Bicycle Glossary E F Eccentric Sheldon Brown Retrieved 2007 06 09 Cannondale 1FG Easy Chain Tensioning Archived from the original on 2007 11 23 Retrieved 2007 10 19 Retrieved from https en wikipedia org w index php title Eccentric mechanism amp oldid 1194619831, wikipedia, wiki, book, books, library,
