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Steam Locomotive Types

Steam Locomotive
Wheel Arrangements and Names

Wheel
Arrangement
Name(s) applied
to this type
Use* PRR
Class
RDG
Class
Notes
2-2-0 Planet P/F      
2-2-2   P   (inspection loco) single engine known
4-2-0 Jervis ?      
4-2-2 Bicycle P      
0-4-0 Four-coupled S A A  
2-4-2 Columbia P      
0-4-0 American or Eight-wheeler F/P D D  
4-4-2 Atlantic P E P
(rebuilt from
4-4-4s)
 
4-4-4 Reading P O-1
(electric)
P
(rebuilt to
4-4-2s)
 
0-6-0 Six-coupled S B B  
2-6-0 Mogul F/P F    
2-6-2 Prairie F/P J-28    
2-6-4 Adriatic P   Q
(tank engine)
 
4-6-0 Ten-wheeler F/P G L  
4-6-2 Pacific P K G  
4-6-4 Baltic or Hudson P P
(electric)
   
0-8-0 Eight-coupled S C-1 E  
2-8-0 Consolidation F H I  
2-8-2 Mikado or MacArthur F L M  
2-8-4 Berkshire or Kanawha(C&O) F/P      
4-8-0 Twelve-wheeler F/P      
4-8-2 Mountain or Mohawk F/P M-1    
4-8-4 Northern or Niagara or Greenbrier or Pocono or Dixie or Confederation F/P R-1
(electric)
T-1  
6-8-6   F S-2
(turbine)
   
0-10-0 Ten-coupled S      
0-10-2 Union S      
2-10-0 Decapod F I-1    
2-10-2 Santa Fe F N K  
2-10-4 Texas F J-1    
4-10-0 Mastodon or Gobernador F/P      
4-10-2 Southern Pacific(SP) or Overland(UP) F      
4-12-2 Union Pacific F      
0-4+4-0   F/P AA-1
(electric)
  Articulated
2-4-4-2
(2-8-2)
  F L-5
(electric)
  Rigid Frame
4-4-4-4
(4-8-4)
  P T-1   Rigid Frame
4-4+4-4   F/P DD-1
(electric)
  Articulated
6-4-4-6
(6-8-6)
  P S-1   Rigid Frame
2-4+6-2   F     Articulated
4-6-4-4
(4-10-4)
  F Q-1   Rigid Frame
4-4-6-4
(4-10-4)
  F Q-2   Rigid Frame
0-6+6-0   F     Articulated
2-6+6-0   F     Articulated
2-6+6-2   F/P FF
(electric)
  Articulated
2-6+6-4   F     Articulated
2-6+6-6 Allegheny or Alleghany or Blue Ridge(VGN) F     Articulated
4-6+6-4 Challenger F/P GG-1
(electric)
  Articulated
0-8+8-0   F CC-1s   Articulated
2-8+8-0   F HC-1s N-1
(rebuilt)
Articulated
2-8+8-2   F HH-1s N-1
(as built)
Articulated
2-8+8-4 Yellowstone F     Articulated
4-8+8-4 Big Boy F     Articulated
2-10+10-2   F     Articulated
2-8+8+8-2 Triplex F     Articulated
2-8+8+8-4 Triplex F     Articulated
Wheel arrangements are listed using the Whyte system; the first number is the number of guide wheels at the front of the engine, the last number is the number of guide wheels at the back of the engine, the numbers in the middle are the number of driving (powered) wheels. Plus signs show articulation joints, hyphens show separation between sets of wheels otherwise. Most engines with more than one set of driving wheels were articulated, but a few types, such as the 4-4-4-4 (PRR T-1) had rigid frames. PRR also had two classes, the Q-1 and Q-2, which had the same number of drivers, in two different configurations. PRR’s articulated engines had double-letter classes, as in "GG-1" presumably since the wheel arrangement was the same as two "G" class ten-wheelers back-to-back. Most PRR electrics were articulated, with the L-5, L-6 and the R-1 being exceptions to this general rule. Names were given to types of engines by railroads and by railfans. Some wheel arrangements were given different names on different railroads, for example: the New York Central, which advertised a "water-level route" did not want a "Mountain" type locomotive, but they did want a 4-8-2, so they renamed theirs "Mohawks" after a river in New York. As long as they were at it, they renamed several other types after rivers as well, the Hudson being the best-known. Some Southern railroads did not want to call their 4-8-4 locomotives "Northerns" so they called them by several other names. During WWII, some patriotic railroaders objected to the "Mikado" name used for 2-8-2 engines, and renamed them "MacArthurs" at least for the duration of the war.

*Use: F=Freight, P=Passenger, S=Switching. Uses varied depending on conditions, from one railroad to another, and over time. The notes on this list are to give an idea of the usual use for each type on most railroads.

List compiled by Frederick Monsimer
©2001 - Permission is granted to make copies for personal noncommercial use, and to distribute copies to others provided no fee is charged.
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