Editing Driving wheel

{{Short description|Powered wheel of a locomotive}}
{{About|the powered wheels on locomotives|powered wheels on automobiles|drive wheel|steering control on automobiles known as that in the UK|Steering wheel}}
[[Image:462driving.jpg|thumb|300px|The driving wheels (boxed) on [[Pennsylvania Railroad 1737]]]]
[[Image:Traction motor german-class140.jpg|thumb|300px|Traction motor for a German locomotive]]

On a [[steam locomotive]], a '''driving wheel''' is a powered wheel which is driven by the locomotive's [[piston]]s (or [[turbine]], in the case of a [[steam turbine locomotive]]).<ref>{{cite book| page=37| title=Locomotive Dictionary| edition=1909| first=George L.| last=Fowler| year=1909| publisher=The Railroad Age Gazette| location=New York| url=https://books.google.com/books?id=4rA5AQAAMAAJ&q=locomotive+driving+wheel&pg=PA107| via=Google Books}}</ref> On a conventional, non-articulated locomotive, the driving wheels are all coupled together with side rods (also known as [[coupling rod]]s); normally one pair is directly driven by the [[main rod]] (or [[connecting rod]]) which is connected to the end of the [[piston rod]]; power is transmitted to the others through the side rods.<ref>{{cite book| page=177| title=Catechism of the Locomotive| first=Matthias N.| last=Forney| publisher=The Railroad Gazette| location=New York| year=1879| url=https://books.google.com/books?id=ZkMYAAAAYAAJ&q=locomotive+coupling+rods&pg=PA177| via=Google Books}}</ref><ref>{{cite book| page=560| title=Theory of Machines| edition=second| first=S.S.| last=Rattan| publisher=The McGraw-Hill Publishing Company Ltd.| location=New Delhi, India| year=2006| orig-year=1993| isbn=0-07-059120-2| url=https://books.google.com/books?id=emo4W_VFhEsC&q=locomotive+coupling+rods&pg=PA560| via=Google Books}}</ref><ref>{{cite book| page=382| title=Railway Management and Engineering| edition=third| first=V.A.| last=Profillidis| year=2006| publisher=Ashgate Publishing| location=Aldershot, England, and Burlington, VT, USA| isbn=978-0-7546-4854-3| url=https://books.google.com/books?id=MumsYYDF2xAC&q=locomotive+coupling+rods&pg=PA382| via=Google Books}}</ref>

On [[diesel locomotive|diesel]] and [[electric locomotive]]s, the driving wheels may be directly driven by the [[traction motor]]s. Coupling rods are not usually used, and it is quite common for each axle to have its own motor.  [[Jackshaft (locomotive)|Jackshaft]] drive and coupling rods were used in the past{{sfn|Ransome-Wallis|2001|pages=175-176}}<ref>{{cite book| page=52| title=Internal-Combustion Locomotives and Motor Coaches| first1=Prof. I.| last1=Franco| first2=P.| last2=Labryn| date=11 November 2013| isbn=978-94-017-5765-2| url=https://books.google.com/books?id=E3YPCQAAQBAJ&q=locomotive+coupling+rods&pg=PA52| via=Google Books| publisher=Springer}}</ref> (e.g. in the [[Crocodile (locomotive)|Swiss Crocodile locomotive]]<ref>{{cite book| page=38| title=Electric Traction – Motive Power and Energy Supply| first=Andreas| last=Steimel| publisher=Oldenbourg Industrieverlag GmbH| location=Munich| year=2008| isbn=978-3-8356-3132-8| url=https://books.google.com/books?id=Hdvr82d23mkC&q=locomotive+coupling+rods&pg=PA38| via=Google Books}}</ref>) but their use is now confined to [[Switcher locomotive|shunter locomotives]].

On an [[articulated locomotive]] or a [[duplex locomotive]], driving wheels are grouped into sets with wheels within each set linked together.

==Diameter==
[[Image:MILW 261 drivers.jpg|thumb|300px|Half of the driving wheels of [[Milwaukee Road 261]]]]
[[Image:60163 Tornado wheel.JPG|thumb|left|One of six {{convert|6|ft|8|in|2|abbr=on}} driving wheels belonging to [[60163 Tornado|60163 ''Tornado'']]]]
Driving wheels are generally larger than [[leading wheel|leading]] or [[trailing wheel]]s. Since a conventional steam locomotive is directly driven, one of the few ways to '[[Gear ratio|gear]]' a locomotive for a particular performance goal is to size the driving wheels appropriately.<ref>{{cite book| page=[https://archive.org/details/electricrailway01greegoog/page/n594 586]| title=Electric Railway Handbook| first1=Albert S.| last1=Richey| first2=William C.| last2=Greenough| edition=first| publisher=McGraw-Hill Book Company| location=New York| year=1915| url=https://archive.org/details/electricrailway01greegoog| quote=locomotive driving wheel ratio.| via=Internet Archive}}</ref> Freight locomotives generally had driving wheels between {{convert|40|and|60|in|mm|0}} in diameter; dual-purpose locomotives generally between {{convert|60|and|70|in|mm|0}}, and passenger locomotives between {{convert|70|and|100|in|mm|0}} or so.

The driving wheels on express passenger locomotives have come down in diameter over the years, e.g. from {{convert|8|ft|1|in|mm|0|abbr=on}} on the [[GNR Stirling 4-2-2]] of 1870 to {{convert|6|ft|2|in|mm|0|abbr=on}} on the [[SR Merchant Navy Class]] of 1941. This is because improvements in valve design allowed for higher piston speeds.

==Flangeless wheels== 
Some long-wheelbase locomotives (four or more coupled axles) were equipped with '''blind drivers'''. These were driving wheels without the usual [[flange]]s, which allowed them to negotiate tighter curves without binding.<ref>{{cite journal| page=136| journal=Locomotive Firemen and Enginemen's Magazine| date=August 1916| title=Questions and Answers: Distance Traveled by Driving Wheels in Curving| first=F.P.| last=Roesch| volume=61| issue=2| editor-first=John F.| editor-last=McNamee| publisher=Brotherhood of Locomotive Firemen and Enginemen| location=Columbus, Ohio| url=https://books.google.com/books?id=fPXNAAAAMAAJ&q=locomotive+blind+driver&pg=PA136| via=Google Books}}</ref>

Some three-driving-axle locomotives also had flangeless wheels on the middle axle, such as [[Everett Railroad 11]], and the [[NZR WH class]].

==Balancing==
{{main|Engine balance}}
[[Image:Steam locomotive driving wheel.jpg|thumb|300px|A flangeless driving wheel on a [[steam locomotive]]]]
On locomotives with [[side rod]]s, including most [[Steam locomotive|steam]] and [[Jackshaft (locomotive)|jackshaft]] locomotives, the driving wheels have weights to balance the weight of the coupling and connecting rods.<ref>{{cite journal| page=414| title=Another Balancing Scheme| journal=Locomotive Engineering| date=September 1898| publisher=Angus Sinclair Co.| location=New York| volume=XI| issue=9| url=https://books.google.com/books?id=dDwOAQAAIAAJ&q=locomotive+driver+balancing&pg=PA444| via=Google Books}}</ref><ref>{{cite journal| page=18| title=The Rule of Equipoise: In Counter-Balancing Locomotive Driving Wheels| journal=International Railway Journal| first1=E.M.| last1=Herr| first2=S.P.| last2=Bush| first3=W.H.| last3=Lewis| first4=C.H.| last4=Quereau| volume=XII| issue=1| date=September 3, 1904| location=Philadelphia and Chicago| url=https://books.google.com/books?id=DvlKAAAAYAAJ&q=locomotive+driver+balancing&pg=RA1-PA18| via=Google Books}}</ref> The crescent-shaped balance weight is clearly visible in the illustrative image.

==Whyte notation==
In the [[Whyte notation]], driving wheels are designated by the middle number or numbers in the set.{{sfn|Ransome-Wallis|2001|page=505}}<ref>{{cite book| pages=55–56| title=History of Technology| volume=33| editor-first=Ian| editor-last=Inkster| publisher=Bloomsbury Academic| location=London and New York| year=2017| isbn=978-1-4742-3725-3| url=https://books.google.com/books?id=iP8jDwAAQBAJ&q=whyte+notation&pg=PA76| via=Google Books}}</ref> The [[UIC classification]] system counts the number of axles rather than the number of wheels and driving wheels are designated by letters rather than numbers. The suffix 'o' is used to indicate independently-powered axles.<ref>{{cite book| chapter=Know your Engine: Main line diesel and electric locomotive wheel arrangements| title=More Amazing and Extraordinary Railway Facts| first=Julian| last=Holland| publisher=David & Charles| year=2011| location=Newton Abbot| isbn=9781446356838| chapter-url=https://books.google.com/books?id=AT6-g1i9t6YC&q=whyte+notation&pg=PT150| via=Google Books}}<!-- this book does not have page numbers shown in the digitized version on Google Books --></ref>

The number of driving wheels on locomotives varied quite a bit. Some early locomotives had as few as two driving wheels (one axle). The largest number of total driving wheels was 24 (twelve axles) on the [[2-8-8-8-2]] and [[2-8-8-8-4]] locomotives. The largest number of coupled driving wheels was 14 (seven axles) on the ill-fated AA20 [[4-14-4]] locomotive.

==Other uses of the term ''driving wheel''==
The term ''driving wheel'' is sometimes used to denote the ''[[Sprocket|drive sprocket]]'' which moves the [[Caterpillar track|track]] on tracked vehicles such as [[tank]]s and [[bulldozer]]s.<ref>{{cite book| page=viii| title=Armoured Guardsmen| first=Robert| last=Boscawen| publisher=Pen & Sword| orig-year=2001| year=2010| location=Barnsley, England| isbn=978-1-84884-317-2| url=https://books.google.com/books?id=kNtDBgAAQBAJ&q=driving+wheel+on+tracked+vehicles&pg=PR8| via=Google Books}}</ref><ref>{{cite book| page=7| title=The Kids' Guide to Military Vehicles| first=Lisa M. Bolt| last=Simons| publisher=Edge Books| location=Mankato, MN| year=2010| isbn=978-1-4296-3370-3| url=https://books.google.com/books?id=yhgYAatMOJ0C&q=driving+wheel+on+tracked+vehicles&pg=PP5| via=Google Books}}</ref>

==In popular culture==
Many American roots artists, such as [[The Byrds]], [[Tom Rush]], [[The Black Crowes]] and the Canadian band [[Cowboy Junkies]] have performed a song written by [[David Wiffen]] called "Driving Wheel", with the lyrics "I feel like some old engine/ That's lost my driving wheel."<ref>{{cite web| url=https://www.musixmatch.com/lyrics/Chris-and-Rich-Robinson/Driving-Wheel| title=Lyrics: Driving Wheel| website=MusixMatch| access-date=July 8, 2017}}</ref>

These lyrics are a reference to the traditional blues song "Broke Down Engine Blues" by [[Blind Willie McTell]], 1931.<ref>{{cite web| url=https://genius.com/Blind-willie-mctell-broke-down-engine-blues-lyrics| title=Broke Down Engine Blues| website=Genius| access-date=July 8, 2017}}</ref> It was later directly covered by [[Bob Dylan]] and [[Johnny Winter]].

Many versions of the American folk song "[[In the Pines]]" performed by artists such as Leadbelly, [[Mark Lanegan]] (on ''[[The Winding Sheet]]''), and [[Nirvana (band)|Nirvana]] (On ''[[MTV Unplugged In New York]]'') reference a decapitated man's head found in a driving wheel.<ref>{{cite web| url=http://songmeanings.com/songs/view/3530822107858607935/| title=Lead Belly - In the Pines| website=Song Meanings| access-date=July 8, 2017}}</ref> In addition, it is likely that Chuck Berry references the locomotive driving wheel in "Johnny B. Goode" when he sings, "the engineers would see him sitting in the shade / Strumming with the rhythm that the drivers made."

==See also==
{{colbegin}}
* [[AAR wheel arrangement]]
* [[Boxpok]]
* [[Drive axle]]
* [[Sprocket|Sprocket wheel]]
* [[UIC classification]]
* [[Whyte notation]]
{{colend}}

==References==
{{Reflist}}
{{refbegin}}
* {{cite book| title=Illustrated Encyclopedia of World Railway Locomotives| editor-first=P.| editor-last=Ransome-Wallis| publisher=Dover Publications| location=Mineola, NY| orig-year=1959| year=2001| isbn=0-486-41247-4| url=https://books.google.com/books?id=GVgiRfFBiTgC&q=locomotive+coupling+rods&pg=PA176| via=Google Books}}
{{refend}}

{{Locomotive running gear}}

[[Category:Steam locomotive technologies]]
[[Category:Train wheels]]