{{Short description|Round gear, usually the smaller of two (meshed) gears}} {{About|a type of gear}}

thumb|right|Pinion and annular gear A '''pinion''' is a round gear—usually the smaller of two meshed gears—used in several applications, including drivetrain and rack and pinion systems.

== Applications == === Drivetrain === Drivetrains usually feature a gear known as the pinion, which may vary in different systems, including

* the typically smaller gear in a gear drive train (although in the first commercially successful steam locomotive—the ''Salamanca''—the ''pinion'' was rather large).<ref name="agma">{{cite book|isbn=1-55589-846-7|oclc=65562739|title=Gear Nomenclature, Definition of Terms with Symbols|year=2005|pages=72|id=ANSI/AGMA 1012-G05|publisher=American Gear Manufacturers Association}}</ref> In many cases, such as remote controlled toys, the pinion is also the drive gear for a reduction in speed, since electric motors operate at higher speed and lower torque than desirable at the wheels. However the reverse is true in watches, where gear trains commence with a high-torque, low-speed spring and terminate in the fast-and-weak escapement. * the smaller gear that drives in a 90-degree angle towards a crown gear in a differential drive. * the small front sprocket on a chain driven motorcycle. *the '''clutch bell''' gear when paired with a centrifugal clutch, in radio-controlled cars with an engine (e.g., nitro).<ref>{{cite web| url = http://www.nitrorc.com/articles/clutch.html| archive-url = https://web.archive.org/web/20020127002635/http://www.nitrorc.com/articles/clutch.html| url-status = dead| archive-date = January 27, 2002| title = Clutch Tuning| author = Eric Perez| publisher = NitroRC.com| access-date = 2010-01-29}}</ref>

=== Rack and pinion === thumb|right|Rack and pinion animation {{Main|Rack and pinion}} In rack and pinion systems, the pinion is the round gear that engages and moves along the linear rack.

== See also == * List of gear nomenclature

== References == {{reflist}}

Category:Gears

{{wiktionarypar|pinion}} {{Gears}}

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