Editing Rack and pinion

{{short description|Type of linear actuator}}
{{for|rack-and-pinion railways|Rack railway}}
[[Image:Rack and pinion animation.gif|frame|right|Animation of a rack and pinion]]

<span lang="my">A</span> '''rack and pinion''' is a type of [[linear actuator]] that comprises a circular [[gear]] (the ''[[pinion]]'') engaging a linear gear (the ''rack'').<ref name="agma">{{cite book|isbn=1-55589-846-7|oclc=65562739|title=Gear Nomenclature, Definition of Terms with Symbols|pages=72|id=ANSI/AGMA 1012-G05|publisher=[[American Gear Manufacturers Association]]|year=2005}}</ref> Together, they convert between rotational motion and linear motion: rotating the pinion causes the rack to be driven in a line. Conversely, moving the rack linearly will cause the pinion to rotate. 

The rack and pinion mechanism is used in [[rack railway]]s, where the pinion mounted on a [[locomotive]] or a [[railroad car]] engages a rack usually placed between the rails, and helps to move the [[train]] up a steep [[Grade (slope)|gradient]].  It is also used in [[arbor press]]es and [[drill press]]es, where the pinion is connected to a [[lever]] and displaces a  vertical rack (the '''ram''').  In [[pipeline transport|pipelines]] and other industrial piping systems, a rack displaced by a [[actuator|linear actuator]] turns a pinion to open or close a [[valve]]. [[Stairlifts]], [[lock gate]]s, [[electric gate]]s, and the mechanical [[steering]] mechanism of cars are other notable applications. 

The term "rack and pinion" may be used also when the rack is not straight but '''arcuate''' (bent), namely just a section of a large gear.<ref>{{cite book | last = Phillips | first = Jack | title = General Spatial Involute Gearing | publisher = Springer Berlin Heidelberg | location = Berlin, Heidelberg | year = 2003 | isbn = 3662053020 }}</ref>

A single pinion can simultaneously drive two racks, parallel but opposite; which will always be displaced by the same distance, only in opposite directions.  Conversely, by applying opposite forces to the two racks one can obtain pure torque on the pinion, without any force component.  This '''double rack and pinion''' mechanism can be used, for example, with a pair of [[actuator#Pneumatic|pneumatic actuator]]s to operate a [[valve]] with minimum stress.<ref>{{cite web|title=Automax SuperNova Series Pneumatic Rack & Pinion Actuators|url=http://www.flowserve.com/files/Files/Literature/ProductLiterature/FlowControl/Automax/AXENBR1001.pdf|publisher=Flowserve Corporation|access-date=7 July 2014}}</ref>

== Applications gallery ==

<gallery mode=packed heights="180px" widths="240px">
File:Lock gate cogs, Montgomery Canal - geograph.org.uk - 1806427.jpg|[[Lock gate]] lifter on a [[canal]]
File:Sliding electric gate-001.JPG|Electric gate
File:Steer system.jpg|right|Automobile steering mechanism
File:Budapešť, Városmajor, pomník zubačky.jpg|Rack railway [[Wheelset (rail transport)|wheelset]]
File:Muzeum MHD, dvoukolí vozu petřínské lanovky 1891.jpg|Funicular wheelset and brake
File:Pneumatic Rack and Pinion Actuators.JPG|Double-rack pneumatic valve actuator
</gallery>

==History==

The time and place of the invention of the rack-and-pinion mechanism are unknown, but it presumably was not long after the invention of gears.  The [[south-pointing chariot]] from China and the [[Antikythera mechanism]] are evidence of these being well-known already a couple of centuries [[Before Christ|BC]].{{Citation needed|date=August 2024}}

In 1598, firearms designer Zhao Shizhen developed the Xuanyuan [[arquebus]] (軒轅銃), featuring a rack-and-pinion [[matchlock]] mechanism derived from an [[Ottoman weapons|Ottoman]] Turkish matchlock design.<ref name=zhao1598>Zhao Shizhen (1598): ''Shen Qi Pu'' (神器譜)</ref> The ''[[Wu Pei Chih]]'' (1621) later described [[Ottoman Empire|Ottoman]] Turkish [[muskets]] that used a rack-and-pinion mechanism.<ref>{{Citation |last=Needham |first=Joseph |author-link=Joseph Needham |title=Science & Civilisation in China |year=1986 |publisher=Cambridge University Press |volume=V:7: ''The Gunpowder Epic'' |isbn=0-521-30358-3 |page=446}}</ref><ref>{{cite book |last1=和田 |first1=博徳 |title=明代の鐡砲傳來とオスマン帝國 : 神器譜と西域土地人物略」『史學』第31巻1-4 |date=October 1958 |publisher=三田史学会、東京 |location=Tokyo |pages=692–719}}</ref>

The use of a variable rack (still using a normal pinion) was invented by [[Arthur Ernest Bishop]]<ref>{{cite web|title=Rack and pinion variable ratio steering gear|publisher=Google Patent Search|url=http://www.google.com/patents?vid=USPAT3753378&id=bTEwAAAAEBAJ&dq=pinion+%2Bininventor:Arthur+ininventor:E+ininventor:Bishop&jtp=1|access-date=2007-03-22}}{{dead link|date=June 2024|bot=medic}}{{cbignore|bot=medic}}</ref> in the 1970s, so as to improve vehicle response and steering "feel", especially at high speeds. He also created a low cost [[Forging|press forging]] process to manufacture the racks, eliminating the need to machine the gear teeth.

== Comparison with Worm gear ==

A rack and pinion has roughly the same purpose as a [[worm gear]] with a rack replacing the gear, in that both convert torque to linear force. However the rack and pinion generally provides higher linear speed — since a full turn of the pinion displaces the rack by an amount equal to the pinion's [[gear#pitch circle|pitch circle]] whereas a full rotation of the worm screw only displaces the rack by one tooth width.  By the same token, a rack and pinion mechanism yields a smaller linear force than a worm gear, for the same input torque. Also, a rack and pinion pair can be used in the opposite way, to turn linear force into torque; whereas a worm drive can be used in only one way.<ref name=zhig2023>ZHY Gear(1023): "[https://www.zhygear.com/worm-gears-vs-rack-and-pinion/ Worm Gears vs. Rack and pinion]". Online article at [https://www.zhygear.com/ the company's website]. [https://web.archive.org/web/20240728233459/https://www.zhygear.com/worm-gears-vs-rack-and-pinion/ Archived on 2024-07-28].</ref>

== Geometry ==
The teeth of a rack and pinion pair may be either straight (parallel to the rotation axis, as in a [[spur gear]]) or [[helical gear|helical]]. On the pinion, the profile of the working tooth surfaces is usually an arc of [[involute]], as in most gears. On the rack, on the other hand, the matching working surfaces are flat.  One may interpret them as involute tooth faces for a gear with infinite radius.  In both parts the teeth are typically formed with a gear cutter (a [[Hobbing|hob]]).<ref name="agma"/>

==See also==
{{portal|Technology}}
 {{div col|colwidth=23em}}
* [[List of gear nomenclature]]
* [[Machine element]]
* [[Pitman arm]]
* [[Rack phase difference]]
* [[Sprocket]]
* [[Steep grade railway]]
 {{div col end}}

==References==
{{Commons category|Rack gears}}
{{reflist}}

{{Gears}}
{{Powertrain}}

{{DEFAULTSORT:Rack and Pinion}}
[[Category:Automotive steering technologies]]
[[Category:Gears]]
[[Category:Actuators]]
[[Category:Turkish inventions]]