This article is from the Model Trains FAQ, by Christopher D Coleman with numerous contributions by others.
I'm confused what all the locomotive types are.
This is a ROUGH listing of prototype locomotives types.
STEAMERS - (# front/pilot - middle/drivers - back/trailingswheels).
Principal Makers: Alco, Baldwin, Lima, N&W RR.
Burns Coal, Wood or Oil in firebox, fumes pass through water-sfilled boiler in flue tubes, and exit into smokebox and upsthrough stack. Heated water passes from the rear tender tanksto boiler to the cylinders. Reciprocating rods connect pistonssto wheels.
O-anything-O Switcher
4-4-0 American
4-4-2 Atlantic
2-6-2 Prairie
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 Mastodon
4-8-2 Mountain
4-8-4 Northern
2-10-0 Deacpod
4-6-6-4 Challenger
4-8-8-4 Big Boy
2-8-8-8-2, 2-8-8-8-4 Triplex
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 Allegheny
4-4-4 A Baltimore
4-6-4-4 Pennsylvania
4-10-0 Mastodon
4-10-2 Southern Pacific
4-12-2 Union Pacific
A steamer with two pair of cylinders is Duplex.
A duplex with the front and/or rear drivers hinged is Articulated.
A duplex which uses the steam in the cylinder pairs sequentially is a
Compound.
A duplex which divides the steam between cylinder pairs is a Simple.
An articulated compound is a Mallet.
 
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