{{Short description|Steam locomotive wheel arrangement}} [[File:LSWR T7 4-2-2-0.jpg|thumb|Prototype LSWR T7 4-2-2-0]]
Under the [[Whyte notation]] for the classification of [[steam locomotive]]s, '''4-2-2-0''' represents the [[wheel arrangement]] of four [[leading wheel]]s on two axles, four independently driven [[driving wheel]]s on two axles, and no [[trailing wheel]]s. The arrangement became known as ''double single''.<ref>{{cite book |url=https://books.google.com/books?id=DuTvDwAAQBAJ&pg=PA63 |title=L&SWR Drummond Passenger and Mixed Traffic Locomotive Classes |year=2020 |publisher=Pen and Sward Transport |language=en |page=63|isbn=978-1-5267-6984-8 }}</ref><ref>{{cite web|title=The Evolution of Compound Locomotives |periodical=|publisher=|url=http://mikes.railhistory.railfan.net/r043.html |url-status=|format=|access-date=2023-07-08|archive-url=|archive-date=|last=|year=1935|language=en|pages=|quote=}}</ref>
==Usage== This unusual wheel arrangement was first used 1884 by Francis Webb in LNWR No. 3026, a 3-cylinder rebuild of a Metropolitan 4-4-0 Tank engine.
[[File:James Toleman 1893 World's Columbian Exposition.jpg|thumb|The ''James Toleman'']] In 1893, the arrangement was used by the British engineer Frederick Charles Winby for the locomotive ''James Toleman'', built by [[Hawthorn Leslie & Company]] in Britain. It was exhibited at the [[World's Columbian Exposition]] in [[Chicago]] and then delivered to the [[Milwaukee Road]].<ref>{{cite book |first=Angus|last=Sinclair |title=Development of the Locomotive Engine |url=https://archive.org/details/cu31924003627167/page/496 |year=1907 |publisher=Angus Sinclair Publishing Company |language=English |page=496-499}}</ref><ref>{{cite book |first=John W. |last=Smith |title=F. C. Winby’s "James Toleman" |url=https://archive.org/details/sim_railroad-history_1928_17/page/n13/mode/2up |year=1928 |publisher=The Railway and Locomotive Historical Society |language=English |page=12-14}}</ref>
Between 1897 and 1901 [[Dugald Drummond]] of the [[London and South Western Railway]] used this wheel arrangement on two classes of [[divided drive (locomotive)|divided drive]] locomotives, the [[LSWR T7 class|T7]] and E10 classes. The absence of [[coupling rods]] enabled the driving wheels to be more widely spaced than on a {{whyte|4-4-0}} locomotive and permitted the inclusion of a larger [[Firebox (steam engine)|firebox]]<ref>{{cite book| first=D.L.| last=Bradley| title=Locomotives of the London and South Western Railway, Part 2| publisher=Railway Correspondence and Travel Society| year=1967| page=77}}</ref>
Six locomotives of the type were built which performed adequately, but the uncoupled drivers led to poorer balance and increased wheelslip compared to {{whyte|4-4-0}}s,<ref>{{cite web|title=London & South Western 4-2-2-0 Locomotives in Great_Britain|url=https://www.steamlocomotive.com/locobase.php?country=Great_Britain&wheel=4-2-2-0&railroad=lsw|access-date=2024-06-18}}</ref> thus the type was not perpetuated.
==References== {{reflist}}
{{Whyte types}}
[[Category:4-2-2-0 locomotives| ]] [[Category:Whyte notation|22,4-2-2-0]] [[Category:Railway locomotives introduced in 1897]]