Driving wheel

Image:MILW 261 drivers.jpg]]

Image:60163 Tornado wheel.JPG]]

Driving wheels are generally larger than leading or trailing wheels. Since a conventional steam locomotive is directly driven, one of the few ways to 'gear' a locomotive for a particular performance goal is to size the driving wheels appropriately.{{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}} 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 flanges, which allowed them to negotiate tighter curves without binding.{{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}}

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

{{main|Engine balance}}

Image:Steam locomotive driving wheel.jpg]]

On locomotives with side rods, including most steam and jackshaft locomotives, the driving wheels have weights to balance the weight of the coupling and connecting rods.{{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}}{{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}} The crescent-shaped balance weight is clearly visible in the illustrative image.

In the Whyte notation, driving wheels are designated by the middle number or numbers in the set.{{sfn|Ransome-Wallis|2001|page=505}}{{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}} 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.{{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}}

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.

The term driving wheel is sometimes used to denote the drive sprocket which moves the track on tracked vehicles such as tanks and bulldozers.{{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}}{{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}}

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."{{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}}

These lyrics are a reference to the traditional blues song "Broke Down Engine Blues" by Blind Willie McTell, 1931.{{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}} 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 (On MTV Unplugged In New York) reference a decapitated man's head found in a driving wheel.{{cite web| url=http://songmeanings.com/songs/view/3530822107858607935/| title=Lead Belly - In the Pines| website=Song Meanings| access-date=July 8, 2017}} 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."

{{colbegin}}

• AAR wheel arrangement
• Boxpok
• Drive axle
• Sprocket wheel
• UIC classification
• Whyte notation

{{colend}}

{{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