Editing Driving wheel (section)

==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.