Under theWhyte notation for the classification ofsteam locomotives,2-2-2-0 usually represents thewheel arrangement of twoleading wheels on one axle, four powered but uncoupleddriving wheels on two axles, and notrailing wheels, but can also be used to represent two sets of leading wheels (not in abogie) twodriving wheels, and notrailing wheels. Some authorities place brackets around the duplicated but uncoupled wheels, creating a notation 2-(2-2)-0,[1] or (2-2)-2-0,[2] as a means of differentiating between them. Others simply refer to the locomotives 2-2-2-0.[3]
The 2-2-2-0 wheel arrangement was first used on some locomotives introduced on theEastern Counties Railway byJohn Chester Craven between 1845 and 1847, and someCrampton locomotives on theSouth Eastern Railway in 1849.[4] However the 2-2-2-0 type is usually associated withFrancis Webb of theLondon and North Western Railway who between 1882 and 1890 introduced a number ofcompound locomotive classes including theLNWR Webb Experiment Class,LNWR Dreadnought Class andLNWR Teutonic Class.The locomotives were never reliable and Webb's successorGeorge Whale withdrew them all within three years of taking up office in 1903,[5] ThePennsylvania Railroad hadone engine based on the LNWR compounds which proved to be underpowered and was scrapped in 1897. The type was used with more success on French railways with a 4-cylindercompound locomotive designed byAlfred de Glehn, of theSociété Alsacienne de Constructions Mécaniques (SACM) in 1885. Onelater example was of the4-2-2-0 configuration but it was eventually rebuilt as a4-4-0 instead.[6]