Wheel Arrangement

In rail transport, a wheel arrangement or wheel configuration is a system of classifying the way in which wheels are distributed under a locomotive. Several notations exist to describe the wheel assemblies of a locomotive by type, position, and connections, with the adopted notations varying by country. Within a given country, different notations may also be employed for different kinds of locomotives, such as steam, electric, and diesel powered.
Especially in steam days, wheel arrangement was an important attribute of a locomotive because there were many different types of layout adopted, each wheel being optimised for a different use (often with only some being actually "driven"). Modern diesel and electric locomotives are much more uniform, usually with all axles driven.
==Major notation schemes==
The main notations are the Whyte notation (based on counting the wheels), the AAR wheel arrangement notation (based on counting either the axles or the bogies), and the UIC classification of locomotive axle arrangements (based on counting either the axles or the bogies).
Whyte notation is generally used for steam locomotives throughout the United States, Canada, the United Kingdom and Ireland. For diesels and electrics, North America uses the AAR wheel arrangement scheme while British practice uses a slightly simplified form of the European UIC classification scheme (except for small diesel shunters, where Whyte notation is used).
In mainland Europe, the UIC classification scheme is generally used for all locomotive types including steam, with some exceptions. In France, the UIC classification is used for diesels and electrics while a scheme similar to the Whyte notation, but counting axles instead of wheels, is used for steam locomotives. Notably, Switzerland had its own separate notation system until 1989, with the Swiss locomotive and railcar classification now only retained for its narrow gauge railways.
*AAR wheel arrangement - Used largely throughout the US and Canada for diesel and electric locomotives.
*UIC classification - Used in mainland Europe for all locomotive types. Used in the UK for electric and large diesel locomotives.
*Whyte notation - Used in North America, the UK and Ireland for steam locomotives, and for shunters (US: switchers) in the UK.
==Comparison of wheel arrangements and wheel picture==
:
VDEV/VMEV/UIC-System	Whyte-Notation	American name 	Picture schemeLocomotive front is to the left
A1 	0-2-2 	 	Oo
A2 	0-2-4 	 	Ooo
1A 	2-2-0 	Planet 	oO
1A1 	2-2-2 	Patentee 	oOo
1A2 	2-2-4 	 	oOoo
2′A 	4-2-0 	Crampton, Norris, Jervis 	ooO
2′A1 	4-2-2 	Single Driver 	ooOo
2A2 	4-2-4 	 	ooOoo
3A 	6-2-0 	Crampton 	oooO
N/A 	0-3-0 	 	OOO
B 	0-4-0 	Four-Wheel-Switcher 	OO
B1 	0-4-2 	 	OOo
B2′ 	0-4-4 	Forney 	OOoo
B3′ 	0-4-6 	 	OOooo
1B 	2-4-0 	Hanscom 	oOO
1′B1′ 	2-4-2 	Columbia 	oOOo
1B2′ 	2-4-4 	 	oOOoo
1B3′ 	2-4-6 	 	oOOooo
2′B 	4-4-0 	American, Eight-Wheeler 	ooOO
2′B1′ 	4-4-2 	Atlantic 	ooOOo
2′B2′ 	4-4-4 	Jubilee (CA), Reading (US) 	ooOOoo
2′B3′ 	4-4-6 	 	ooOOooo
C 	0-6-0 	Six-Wheel-Switcher 	OOO
C1 	0-6-2 	 	OOOo
C2′ 	0-6-4 	 	OOOoo
1′C 	2-6-0 	Mogul 	oOOO
1′C1′ 	2-6-2 	Prairie 	oOOOo
1′C2′ 	2-6-4 	Adriatic 	oOOOoo
1′C3′ 	2-6-6 	 	oOOOooo
2′C 	4-6-0 	Ten-Wheeler 	ooOOO
2′C1′ 	4-6-2 	Pacific 	ooOOOo
2′C2′ 	4-6-4 	Hudson, Baltic 	ooOOOoo
D 	0-8-0 	Eight-Wheel-Switcher 	OOOO
D1 	0-8-2 	 	OOOOo
D2′ 	0-8-4 	 	OOOOoo
D3′ 	0-8-6 	 	OOOOooo
1′D 	2-8-0 	Consolidation 	oOOOO
1′D1′ 	2-8-2 	Mikado 	oOOOOo
1′D1′ 	2-8-2T 	MacArthur 	oOOOOo
(1′D1′)(1′D1′) 	2-8-2+2-8-2 	Double Mikado, Garratt 	oOOOOo+oOOOOo
1′D2′ 	2-8-4 	Berkshire 	oOOOOoo
1′D3′ 	2-8-6 	 	oOOOOooo
2′D 	4-8-0 	Twelve-Wheeler, Mastodon 	ooOOOO
2′D1′ 	4-8-2 	Mountain, Mohawk (NYC) 	ooOOOOo
2′D2′ 	4-8-4 	Northern, General Service (SP), Golden State (SP), Niagara (NYC), Wyoming	ooOOOOoo
2D3 	4-8-6 	 	ooOOOOooo
3′D3′ 	6-8-6 	Turbine (Pennsylvania Railroad Steam Turbine) 	oooOOOOooo
E 	0-10-0 	Ten-Wheel Switcher 	OOOOO
E1′ 	0-10-2 	Union 	OOOOOo
1′E 	2-10-0 	Decapod 	oOOOOO
2′E 	4-10-0 	Mastodon 	ooOOOOO
1′E1′ 	2-10-2 	Santa Fe 	oOOOOOo
1′E2′ 	2-10-4 	Texas, Selkirk (Canadian Pacific) 	oOOOOOoo
2′E1′ 	4-10-2 	Southern Pacific, Overland 	ooOOOOOo
F 	0-12-0 	Pennsylvania, Twelve-Wheel-Switcher 	OOOOOO
1′F 	2-12-0 	Centipede 	oOOOOOO
1′F1′ 	2-12-2 	Javanic 	oOOOOOOo
2′F1′ 	4-12-2 	Union Pacific 	ooOOOOOOo
2′G2′ 	4-14-4 	 	ooOOOOOOOoo
Soviet (AA) 	0-2-2-0 	 	O O
B′B 	0-4-4-0 	nameless (Mallet) 	OO OO
B′B1 	0-4-4-2 	nameless (Mallet) 	OO OOo
2′BB2′ 	4-4-4-4 	nameless (Pennsylvania Railroad Duplex) 	ooOO OOoo
3′BB3′ 	6-4-4-6 	 	oooOO OOooo
2′CB2′ 	4-6-4-4 	nameless (Pennsylvania Railroad Duplex) 	ooOOO OOoo
C′C 	0-6-6-0 	Erie (Mallet) 	OOO OOO
(1′C)C 	2-6-6-0 	Denver (Mallet) 	oOOO OOO
(1′C)C1′ 	2-6-6-2 	Mallet Mogul (SP), Prairie Mallet (ATSF), Chesapeake 	oOOO OOOo
(1′C)C2′ 	2-6-6-4 	nameless (Simple articulated) 	oOOO OOOoo
(2′C)C2′ 	4-6-6-4 	Challenger (Simple articulated) 	ooOOO OOOoo
(1′C)C3′ 	2-6-6-6 	Allegheny, Blue Ridge (Mallet/Simple articulated) 	oOOO OOOooo
D′D 	0-8-8-0 	Angus (Mallet) 	OOOO OOOO
(1′D)D 	2-8-8-0 	Bullmoose (Mallet) 	oOOOO OOOO
(1′D)D1′ 	2-8-8-2 	Chesapeake, Mallet consolidation (Mallet) 	oOOOO OOOOo
(1′D)D2′ 	2-8-8-4 	Yellowstone (Mallet/Simple articulated) 	oOOOO OOOOoo
(2′D)D1′ 	4-8-8-2 	Cab Forward (Simple articulated) 	ooOOOO OOOOo
(2′D)D2′ 	4-8-8-4 	Big Boy (Simple articulated) 	ooOOOO OOOOoo
(1′E)E1′ 	2-10-10-2 	Virginian (Mallet) 	oOOOOO+OOOOOo
(2′C1′)(1′C2′) 	4-6-2+2-6-4 	Double Pacific (Garratt) 	ooOOOo+oOOOoo
(2′C2′)(2′C2′) 	4-6-4+4-6-4 	Double Hudson (Garratt) 	ooOOOoo+ooOOOoo
(2′D)(D2′) 	4-8-0+0-8-4 	Double Mastodon (Garratt) 	ooOOOO+OOOOoo
(2′D1′)(1′D2′) 	4-8-2+2-8-4 	Double Mountain (Garratt) 	ooOOOOo+oOOOOoo
(2′D2′)(2′D2′) 	4-8-4+4-8-4 	Double Northern (Garratt) 	ooOOOOoo+ooOOOOoo
==See also==
*Co-Co locomotives
Category:Locomotives
Category:Wheel arrangements