Baltimore and Ohio Railroad Locomotives - Locomotive Classification

Locomotive Classification

Before the Civil War, the B&O organized its locomotives into four classes, based upon relative power. After the war this was felt to be inadequate, and a classification scheme was devised, based upon wheel arrangement. Each wheel arrangement was assigned a letter, except for 4-4-0 locomotives, which were subdivided according to cylinder size. When articulated steam locomotives were first introduced, they were assigned a single class ("O"). This proved inadequate almost immediately and a two letter code was used instead, based on treating the locomotive as if it were two engines coupled back-to-back.

Within each letter class, a number was assigned for each successive design. Usually the first class was numbered "1". Locomotives acquired through mergers were renumbered and reclassified to fit into the sequences of numbers and classes.

Lowercase letter suffixes were used to denote successive modifications of a design. The "t" suffix was also used to indicate that the locomotive was assigned an extra large tender. In the 20th century, such modifications were common, and the pattern of suffixes could become confusing. At one point there was even a class "Qodd" Mikado (2-8-2).

Diesel locomotives were initially classified according to intended service and model. Eventually this was dropped in favor of using the manufacturer's model designations.

Steam classes were as follows:

• A initially 4-6-0 camelback locomotives; later 4-4-2
• B 4-6-0
• C 0-4-0
• D 0-6-0
• E 2-8-0
• F 4-4-0 with 16" dia. cylinders or less
• G 4-4-0 with 17" dia. cylinders
• H 4-4-0 with 18" dia. cylinders
• I 4-4-0 with 19" dia. cylinders
• J 4-4-0 and 4-4-4 with Wootten fireboxes
• K 2-6-0
• L 0-8-0
• M 4-4-0 with 20" dia. cylinders
• N 4-4-4-4 — One locomotive: #5600 George H. Emerson
• O originally for any Mallet type; replaced by two letter code
• P 4-6-2
• Q 2-8-2
• R 0-4-4 Forney locomotives
• S 2-10-2 – Two classes S and S-1
• T 4-8-2
• U 0-10-0
• V 4-6-4 – Four locomotives in four classes: V-1, V-2, V-3, and V-4.
• W 4-2-2-2-2-4 geared locomotive (never built)
• Y 2-10-0

Articulated classes:

• DD 0-6-6-0
• EE 2-8-8-2
• EL 2-8-8-0
• EM 2-8-8-4
• KB 2-6-6-4
• KK 2-6-6-2
• KL 2-6-8-0
• LL 0-8-8-0
• MK 4-4-6-2

Electric locomotive classes were as follows:

• LE-1 the original Bo+Bo motors
• LE-2 Bo-Bo motors intended for freight haulage
• OE-1, OE-2, 'OE-3 Bo-Bo
• CE-1 Bo switcher

There was one gasoline-powered locomotive:

• CG 0-4-0