Editing Centrifugal governor

{{Short description|Mechanism for automatically controlling the speed of an engine}}
[[Image:centrifugal governor.png|right|thumb|Drawing of a centrifugal "fly-ball" governor. The balls swing out as speed increases, which closes the valve, until a balance is achieved between demand and the proportional gain of the linkage and valve.]]

A '''centrifugal governor''' is a specific type of [[governor (device)|governor]] with a feedback system that controls the speed of an [[engine]] by regulating the flow of [[fuel]] or [[working fluid]], so as to maintain a near-constant speed. It uses the principle of [[proportional control]].

Centrifugal governors, also known as "centrifugal regulators" and "fly-ball governors", were invented by [[Christiaan Huygens]] and used to regulate the distance and pressure between [[Millstone#Grinding_with_millstones|millstones]] in [[windmill]]s in the 17th century.<ref>{{citation|last=Hills|first=Richard L|title=Power From Wind|publisher=Cambridge University Press|year=1996}}</ref><ref>{{cite book|url=https://books.google.com/books?id=iwbWCgAAQBAJ&q=%22Centrifugal+Governor%22+Huygens&pg=PA36|title=Adaptive Control Processes: A Guided Tour|first=Richard E.|last=Bellman|date=8 December 2015|publisher=Princeton University Press|access-date=13 April 2018|via=Google Books|isbn=9781400874668}}</ref> In 1788, [[James Watt]] adapted one to control his [[steam engine]] where it regulates the admission of steam into the [[cylinder (engine)|cylinder]](s),<ref>[http://mi.eng.cam.ac.uk/IALego/steam.html University of Cambridge: Steam engines and control theory]</ref> a development that proved so important he is sometimes called the inventor. Centrifugal governors' widest use was on steam engines during the [[Steam power during the Industrial Revolution|Steam Age]] in the 19th century. They are also found on [[Stationary engine|stationary]] [[internal combustion engine]]s and variously fueled [[turbine]]s, and in some modern [[striking clock]]s.

A simple governor does not maintain an exact speed but a speed range, since under increasing load the governor opens the throttle as the speed (RPM) decreases.

==Operation==
[[File:Centrifugal governor and balanced steam valve (New Catechism of the Steam Engine, 1904).jpg|thumb|upright|Cut-away drawing of steam engine speed governor. The valve starts fully open at zero speed, but as the balls rotate and rise, the central [[valve stem]] is forced downward and closes the valve. The drive shaft whose speed is being sensed is top right]]

The devices shown are on steam engines. Power is supplied to the governor from the engine's output shaft by a belt or chain connected to the lower belt wheel. The governor is connected to a [[throttle]] valve that regulates the flow of [[working fluid]] (steam) supplying the [[Prime mover (locomotive)|prime mover]].  As the speed of the prime mover increases, the central spindle of the governor rotates at a faster rate, and the kinetic energy of the balls increases.  This allows the two [[mass]]es on lever arms to move outwards and upwards against gravity. If the motion goes far enough, this motion causes the lever arms to pull down on a [[thrust bearing]], which moves a beam linkage, which reduces the [[aperture]] of a throttle valve. The rate of working-fluid entering the cylinder is thus reduced and the speed of the prime mover is controlled, preventing over-speeding.

Mechanical stops may be used to limit the range of throttle motion, as seen near the masses in the image at the top of this page.

===Non-gravitational regulation===
A limitation of the two-arm, two-ball governor is its reliance on gravity to retract the balls when the governor slows down, and therefore a requirement that the governor stay upright.

Governors can be built that do not use gravitational force, by using a single straight arm with weights on both ends, a center pivot attached to a spinning axle, and a spring that tries to force the weights towards the center of the spinning axle. The two weights on opposite ends of the pivot arm counterbalance any gravitational effects, but both weights use centrifugal force to work against the spring and attempt to rotate the pivot arm towards a perpendicular axis relative to the spinning axle.

Spring-retracted non-gravitational governors are commonly used in [[Single-phase electric power|single-phase]] [[alternating current]] (AC) [[induction motor]]s to turn off the starting [[field coil]] when the motor's rotational speed is high enough. They are also commonly used in [[snowmobile]] and [[all-terrain vehicle]] (ATV) [[continuously variable transmission]]s (CVT), both to engage/disengage vehicle motion and to vary the transmission's pulley diameter ratio in relation to the engine [[revolutions per minute]].

==History==
[[File:Centrifugal governor in Sluis, Netherlands.JPG|thumb|right|A millstone governor at [[Sluis]] in the [[Netherlands]].]]
Centrifugal governors were invented by [[Christiaan Huygens]] and used to regulate the distance and pressure between [[millstone]]s in [[windmill]]s in the 17th century.<ref>{{citation|last=Hills|first=Richard L|title=Power From the Wind|publisher=Cambridge University Press|year=1996}}</ref><ref>{{cite book|url=https://books.google.com/books?id=iwbWCgAAQBAJ&dq=%22Centrifugal+Governor%22+Huygens&pg=PA36|title=Adaptive Control Processes: A Guided Tour|first=Richard E.|last=Bellman|date=8 December 2015|publisher=Princeton University Press|isbn=9781400874668 |accessdate=13 April 2018|via=Google Books}}</ref>

[[File:Boulton and Watt centrifugal governor-MJ.jpg|thumb|left|upright|Boulton & Watt engine of 1788]]
James Watt applied the same technology to steam engines.<ref name="Hannavy2021">{{cite book |last1=Hannavy |first1=John |title=The Governor: Controlling the Power of Steam Machines |date=2021 |publisher=Pen & Sword Transport |location=Barnsley, S. Yorks. |pages=60-78}}</ref> He designed his first governor (or 'centrifugal speed regulator') in 1788, following a suggestion from his business partner [[Matthew Boulton]]. It was a [[conical pendulum]] governor and one of the final series of innovations Watt had employed for steam engines. 

Over subsequent decades a series of improvements and modifications were made by a number of different engineers and manufacturers. Among the inventors who contributed to development of the governor in the 19th century were Charles Porter, Wilson Hartnell, [[Richard Tangye]], Rudolph Proell and Buss.<ref name="Hannavy2021" />

[[File: Ashton Frost engine governor.jpg|thumb|upright|A Porter governor on a [[Corliss steam engine]]. This design, patented by Charles Porter in 1858, used lighter balls and a sliding weight on the spindle; it suited faster engines.]]
[[File:Governor - 17836825593.jpg|thumb|upright|The Pickering Governor (first patented in 1862) has balls mounted on [[leaf springs]]. It was especially suited to smaller high-speed engines and was manufactured in large numbers.]]
As engine speeds increased, the basic Watt-type governor became less reliable as it would tend to over-compensate, [[oscillating]] between opening and closing the steam valve and preventing the engine from running smoothly.<ref name="Hannavy2021" /> This led to many modifications and variations over time, including the addition of a dead weight around the spindle, and the application of springs as part of the design. A number of different firms of engineers patented their own variation on the concept, which they would apply to their own engines, and more modern governors were sometimes retrofitted to engines already in service.

==Uses==
[[File:Ellenroad Engine House - large steam engine governor - geograph.org.uk - 7349748.jpg|thumb|left|upright|The spring-loaded Whitehead governor, patented in 1895, was widely used on mill engines (as here at [[Ellenroad Ring Mill Engine|Ellenroad]]).]]
Centrifugal governors' widest use was on steam engines during the [[Steam power during the Industrial Revolution|Steam Age]] in the 19th century. They are also found on [[Stationary engine|stationary]] [[internal combustion engine]]s and variously fueled [[turbine]]s, and in some modern [[striking clock]]s.

Centrifugal governors are used in many modern [[Repeater (horology)|repeating watches]] to limit the speed of the [[Striking clock#Parts of mechanism|striking train]], so the repeater does not run too quickly.

Another kind of centrifugal governor consists of a pair of masses on a spindle inside a cylinder, the masses or the cylinder being coated with pads, somewhat like a [[centrifugal clutch]] or a [[drum brake]]. This is used in a spring-loaded [[record player]] and a spring-loaded [[telephone]] dial to limit the speed.

==Dynamic systems==
The centrifugal governor is often used in the cognitive sciences as an example of a [[dynamic system]], in which the representation of information cannot be clearly separated from the operations being applied to the representation. And, because the governor is a [[servomechanism]], its analysis in a dynamic system is not trivial.  In 1868, [[James Clerk Maxwell]] wrote a famous paper [[:File:On Governors.pdf|"''On Governors''"]]<ref>{{cite journal|last=Maxwell|first=James Clerk|title=On Governors|journal=Proceedings of the Royal Society of London|volume= 16|year= 1868 |pages= 270–283 | doi = 10.1098/rspl.1867.0055 | jstor=112510|doi-access=}}</ref> that is widely considered a classic in feedback [[control theory]]. Maxwell distinguishes moderators (a centrifugal [[brake]]) and governors which control [[Power (physics)|motive power]] input. He considers devices by [[James Watt]], Professor [[James Thomson (engineer)|James Thomson]], [[Fleeming Jenkin]], [[William Thomson, 1st Baron Kelvin|William Thomson]], [[Léon Foucault]] and [[Carl Wilhelm Siemens]] (a liquid governor).

===Natural selection===
In his famous 1858 paper to the [[Linnean Society of London|Linnean Society]], which led [[Charles Darwin|Darwin]] to publish ''[[On the Origin of Species]]'', [[Alfred Russel Wallace]] used governors as a metaphor for the [[Evolution|evolutionary principle]]:

<blockquote>The action of this principle is exactly like that of the '''centrifugal governor''' of the steam engine, which checks and corrects any irregularities almost before they become evident; and in like manner no unbalanced deficiency in the animal kingdom can ever reach any conspicuous magnitude, because it would make itself felt at the very first step, by rendering existence difficult and extinction almost sure soon to follow.<ref>{{cite web|last=Wallace|first=Alfred Russel|title=On the Tendency of Varieties to Depart Indefinitely From the Original Type|url=http://www.wku.edu/~smithch/wallace/S043.htm|access-date=2009-04-18}}</ref></blockquote>

The [[Cybernetics|cybernetician]] and anthropologist [[Gregory Bateson]] thought highly of Wallace's analogy and discussed the topic in his 1979 book ''Mind and Nature: A Necessary Unity'', and other scholars have continued to explore the connection between natural selection and [[systems theory]].<ref name="Unfinished Business">{{cite web|last=Smith|first=Charles H.|title=Wallace's Unfinished Business|url=http://www.wku.edu/~smithch/essays/UNFIN.htm|publisher=Complexity (publisher Wiley Periodicals, Inc.) Volume 10, No 2, 2004|access-date=2007-05-11}}</ref>

==Culture==
[[File:Governor Memorial to Boulton and Watt (3549047844).jpg|thumb|right|upright|Governor-inspired Memorial to Boulton and Watt in Smethwick.]]
A giant statue of Watt's governor stands at [[Smethwick]] in the [[England|English]] [[West Midlands (county)|West Midlands]].

A centrifugal governor is part of the city seal of [[Manchester, New Hampshire|Manchester]], New Hampshire in the US and is also used on the city flag. A 2017 effort to change the design was rejected by voters.<ref>[https://granitegeek.concordmonitor.com/2017/11/07/manchester-city-flag-celebrates-one-coolest-inventions-industrial-revolution-want-change/ Granite Geek: "Manchester city flag celebrates one of the coolest inventions from the Industrial Revolution – happily, they won’t change it"]</ref>

A stylized centrifugal governor is also part of the coat of arms of the [[Swedish Work Environment Authority]].

In Liu Cixin's science fiction novel [[Death's End|Death's End (from the "Three-Body" series)]], the steam engine centrifugal governor is used as a metaphor for [[Speed of light|"constant speed" (the speed of light)]] . <ref>{{Cite book |last=Liu |first=Cixin |url=https://www.worldcat.org/title/936360629 |title=Death's end |date=2016 |isbn=978-0-7653-7710-4 |oclc=936360629}}</ref>

==See also==
* [[Cataract (beam engine)]]
* [[Centrifugal switch]]
* [[Hit and miss engine]]

==References==
{{Reflist}}

==External links==
* {{Commons category inline|Centrifugal governors}}

{{Steam engine configurations}}
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[[Category:British inventions]]
[[Category:Control devices]]
[[Category:Cybernetics]]
[[Category:Inventions by Christiaan Huygens]]
[[Category:Mechanical power control]]
[[Category:Mechanisms (engineering)]]
[[Category:Rotating machines]]
[[Category:Scottish inventions]]
[[Category:Steam engine governors]]