Steam Locomotive Wheel Arrangements

Introduction

This is a table of the various steam locomotive wheel arrangement classifications used in different countries.  It was originally produced, in French, by Andre-Pierre Allanic, who has a web site at http://perso.club-internet.fr/cosme/index.htm.   It is reproduced here in English with his kind permission.

To the Steam Locomotive Glossary, to Steam Locomotive Links.

Background

Some time after the introduction of steam locomotives, it became necessary to find a way of classifying them.  Eventually, a system was introduced based on the number and arrangement of the axles or wheels, which allowed a locomotive type to be described by observing the types of wheels, beginning from the front: the number of carrying wheels, followed by the number of driving wheels, followed by the number of trailing wheels.   In using the system, the French counted the axles, the Germans also counted the axles but used letters only for the driving axles instead of numbers and the Americans and British counted the number of wheels. This table shows how the classifications work.

Wheel Arrangement French Notation German Notation US and UK Notation US nicknames, also sometimes used elsewhere
Oo 011 A1 0-2-2  
oO 110 1A 2-2-0  
oOo 111 1A1 2-2-2  
ooO 210 2A 4-2-0 Jervis
ooOo 211 2A1 4-2-2  
OO 020 B 0-4-0  
OOo 021 B1 0-4-2  
oOO 120 1B 2-4-0  
oOOo 121 1B1 2-4-2 Colombia
ooOO 220 2B 4-4-0 American
ooOOo 221 2B1 4-4-2 Atlantic
ooOOoo 222 2B2 4-4-4 Reading
OOO 030 C 0-6-0  
oOOO 130 1C 2-6-0 Mogul
oOOOo 131 1C1 2-6-2 Prairie
oOOOoo 132 1C2 2-6-4 Adriatic
ooOOO 230 2C 4-6-0 Ten-wheeler
ooOOOo 231 2C1 4-6-2 Pacific
ooOOOoo 232 2C2 4-6-4 Baltic or Hudson
OOOO 040 D 0-8-0 Switcher
oOOOO 140 1D 2-8-0 Consolidation
oOOOOo 141 1D1 2-8-2 Mikado
oOOOOoo 142 1D2 2-8-4 Berkshire
ooOOOO 240 2D 4-8-0 Mastodon or Twelve-wheeler
ooOOOOo 241 2D1 4-8-2 Mountain
ooOOOOoo 242 2D2 4-8-4 Niagara or Northern
OOOOO 050 E 0-10-0  
OOOOOo 051 E1 0-10-2 Union
oOOOOO 150 1E 2-10-0 Decapod
oOOOOOo 151 1E1 2-10-2 Santa Fe
oOOOOOoo 152 1E2 2-10-4 Texas
ooOOOOO 250 2E 4-10-0 Gobernador
ooOOOOOo 251 2E1 4-10-2 Overland
OOOOOO 060 F 0-12-0  
oOOOOOO 160 1F 2-12-0 Centipede
ooOOOOOOo 261 2F1 4-12-2 Union Pacific
OOO+OOO 030+030 CC 0-6-6-0 Erie
oOOO+OOOooo 130+033 1CC3 2-6-6-6 Allegheny
ooOOO+OOOo 230+031 2CC1 4-6-6-2 Cab Forward
ooOOO+OOOoo 230+032 2CC2 4-6-6-4 Challenger
oOOOO+OOOOo 140+041 1DD1 2-8-8-2 Mallet
oOOOO+OOOOoo 140+042 1DD2 2-8-8-4 Yellowstone
ooOOOO+OOOOoo 240+042 2DD2 4-8-8-4 Big-Boy

A note from Arno Martens of Toronto points out that German steam locomotive notation used:

Capital letters = powered axles
Numeral = leading or trailing unpowered axle
small  o = idividially powered axles
' = movable relative to the main frame

On German steam locos, suffixes were used for the type of steam and number of cylinders.

v = compound
n = no super heat
h = superheated

A Pacific like the BR 01 is a 2'C'1' h3, with 2 leading axles in a bogie, 3 powered axles by a common source, 1 trailing axle, swivable relative to the main frame, superheated, 3-cylinder.

That's why the interesting BRA 19 with its individual V-2 motor driven axles was designated as 1'Do' 1 h8.