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Steam Locomotive Wheel Arrangements
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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 |
Wheel
Arrangement |
French
Notation |
German
Notation |
US and UK
Notation |
US nicknames,
also sometimes
used elsewhere |
|
|
Wheel
Arrangement |
French
Notation |
German
Notation |
US and UK
Notation |
US nicknames,
also sometimes
used elsewhere |
| | ||||
| 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 |
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Wheel
Arrangement |
French
Notation |
German
Notation |
US and UK
Notation |
US nicknames,
also sometimes
used elsewhere |
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This table of the various steam locomotive wheel arrangement classifications used in different countries was originally produced in French, by Andre-Pierre Allanic, who has a web site at perso.club-internet.fr/cosme.
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”.
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