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W&H MAIN YARDS: Locomotive Types

Compiled by Christopher Coleman
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Last Updated 6-25-97

Operational Clasification

Locomotives are most basicly classified by their method of operation, using the method:

FUEL CONVERSION (into mec. energy) TRANSMISSION (generation to application)
coal internal combustion (engine) electric
diesel external combustion (steam) hydraulic
oil steam turbine direct (geared, side rods)
gasoline combustion turbine recipricating (connecting rods)
electricityelectrical (transformer)

Theoreticly all combinations are possible, though some make no sense. Turbines, for example, are already rotating so there is no need for reciprocating rods. The most common examples are:

diesel-internal combustion-electric (diesel electric)
coal-external combustion-recipricating (conventional steam engine)
oil-external combustion-recipricating (conventional steam engine)
wood-external combustion-recipricating (early steam engine)
gasoline-combustion turbine-direct (gas-turbine)
electricity-electrical-electric (Milwaukee Road Bi-Polar electrics)
electricity-electrical-direct (PRR GG-1)
electricity-electrical-recipricating (PRR DD-1)


Shays, Cimaxes, Heislers were designed for branch, short and logging line use, and so had to be able to negotiate tight curves.

coal-external combustion-direct
oil-external combustion-direct
wood-external combustion-direct


A number of combinations were tried, but did not gain popular acceptance.

coal-internal combustion-electric (GE experimental coal slurry)
coal-steam turbine-electric (N&W's Jawn Henry, C&O's experimental M1's)
coal-steam turbine-direct (Pensylvania's S-2)
diesel-internal combustion-electric (UP's Big Blows)
diesel-internal combustion-hydraulic (D&RG/SP demonstrators)

The Whyte System

Recipricating steam locomotives are commonly catagorized by wheel arrangement number of:

0-anything-0 Switcher
4-4-0 American
4-4-2 Atlantic
2-6-2 Prarie
2-6-0 Mogul
4-6-2 Pacific
4-6-4 Hudson
2-8-0 Consolidation
2-8-2 Mikado
2-8-4 Berkshire
4-8-0 Mastadon
4-8-2 Mountain
4-8-4 Northern
2-10-0 Deacpod
4-6-6-4 Challenger
4-8-8-4 Big Boy
4-8-8-8-4 Tripex
4-6-0  Tenwheeler
4-10-0 Twelvewheeler 
2-10-2 Santa Fe
2-10-4 Texas
2-4-2 Columbia
2-6-6-6  Allegeney
4-4-4 A Baltimore
4-6-4-4 Pennsylvania
4-10-0 Mastodon
4-10-2 Southern Pacific
4-12-2 Union Pacific 

For a more complete list see Wheel Arrangements of North American Steam Locomotives or Wes Barris has an extensive list at his Steam Locomotive Information pages.

Diesels and Electrics

Traction motored and geared truck locos are commonly classified by another system:
A = single powered axle
B = double powered axle
C = triple powered axle
D = quadruple powered axle
1 = single unpowered axle
2 = double unpowered axle
3 = triple unpowered axle
4 = quadruple unpowered axle
Sometimes  these are used with an o (Ao, Co) to indicate independent drive.
- = trucks mounted on the same frame or subframe
+ = trucks mounted on different frames (frames hinged together 
      or pivoted on main frame)

For example:

B-B       GM GP's, BL-2, FT, F's, GE U__B's
C-C       GM SD's, GE U__C's, E44
A1A-A1A   E's, PA's 
2-B+B-2   PRR DD1, DD2
1-C+C-1   PRR FF2
2-C+C-2   PRR GG1
1-B-D-D-B-1  MILW EP-2

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