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Class (locomotive) refers to a group of locomotives built to a common design for a single railroad. It is analogous to ship class. A ship class is a group of ships of a similar design. ...
Development
As locomotives became more numerous, the need arose to deal with them in groups of similar engines rather than as named or numbered individuals. These groups were named "classes" and at first tended to reflect capability rather than design. For example, the Baltimore and Ohio Railroad grouped its roster into four classes before the Civil War, though they had by that point dozens of different designs. 1876 map The Baltimore and Ohio Railroad (B&O) is one of the oldest railroads in the United States, with an original line from the port of Baltimore, Maryland west to the Ohio River at Wheeling, West Virginia and Parkersburg, West Virginia. ...
A civil war is a war in which parties within the same culture, society or nationality fight for political power or control of an area. ...
Later classes were based on design. A group of locomotives built off the same blueprints constituted a class, and if some of the locomotives in the class were sufficiently modified, a new class might be established for the modified examples. When electric locomotives were introduced, the same sceme was applied to them.
Since steam and early electric locomotives were usually custom built, classes were assigned by the railroad, and each railroad had its own system. Mergers of lines and sales of locomotives brought about changes of class. Early diesels were often fitted into the locomotive class system, but since they were generally not custom-built, the use of manufacturer model designations overtook the class system and made it irrelevant, except for historical discussion.
Class system organization Usually the class system for a railroad was built on a simply hierarchy which assigned each class a code.
First level: Wheel arrangement The first level was usually for the wheel arrangement and was usually coded by a letter of the alphabet. Different railroads used different codes, so that "J" on the New York Central Railroad meant a 4-6-4 (Hudson), while on the Norfolk and Western Railway it mean a 4-8-4 (Northern), and on the Baltimore and Ohio Railroad it denoted a 4-4-0 with a Wootten firebox. Locomotive wheel arrangement is how the wheels of the locomotive are arranged by type, position, and connections. ...
The New York Central Railroad (AAR reporting mark NYC), known simply as the New York Central in its publicity, was a railroad operating in the North-Eastern United States. ...
A 4-6-4 locomotive, in the Whyte notation for the classification of steam locomotives, has four leading wheels (generally arranged in a leading truck), six coupled driving wheels and four trailing wheels (often but not always in a trailing truck). ...
Norfolk and Western Railway - Wikipedia /**/ @import /skins-1. ...
The Norfolk & Western Railways Class J locomotive #611, a 1950 product of the railroads own Roanoke, Virginia shops. ...
1876 map The Baltimore and Ohio Railroad (B&O) is one of the oldest railroads in the United States, with an original line from the port of Baltimore, Maryland west to the Ohio River at Wheeling, West Virginia and Parkersburg, West Virginia. ...
Atlantic, Mississippi and Ohio Railroad #87, delivered 1873-10-27 from the Mason Machine Works of Taunton, Massachusetts. ...
Articulated locomotives were handled through two different methods. On many railroads each wheel arrangement was assigned its own unique letter, due to the limited number of arrangements that had to be represented. On other railroads this was insufficient, and commonly articulated locomotives were represented with a two letter code, one letter for the arrangement of each half. Therefore the Pennsylvania Railroad GG1 (UIC 2Co+Co2) is represented as if it were two ten-wheelers (4-6-0) coupled tail-to-tail. An articulated locomotive is a steam locomotive with one or more engine units which can move relative to the main frame. ...
UIC may refer to: University of Illinois at Chicago Union Internationale des Chemins de Fer (translation: International Union of Railways) UEFA_Intertoto_Cup This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ...
In the Whyte notation, a 4-6-0 is a railroad steam locomotive that has a two-axle leading truck followed by three driving axles. ...
Second level: Sequential model A sequence number was often added to distinguish different designs of the same wheel arrangement. As a rule, the first design for a given arrangement had no sequence number, so that numbering stated at 1 with the second design for the wheel arrangement. For example, there were two main classes of 2-10-2 locomotives on the B&O. labelled "S" and "S-1". This 2-10-2 locomotive is a Pennsylvania Railroad class N1s. ...
1876 map The Baltimore and Ohio Railroad (B&O) is one of the oldest railroads in the United States, with an original line from the port of Baltimore, Maryland west to the Ohio River at Wheeling, West Virginia and Parkersburg, West Virginia. ...
Third level: Variants Letter suffixes were often used to indicate variants in a basic design. Sometimes these also referred to specific characteristics; for example, for many years the Pennsylvania Railroad used a "s" suffix to indicate superheating, while on the B&O a "t" suffix indicated an engine with an oversize tender. 1893 map The Pennsylvania Railroad (AAR reporting mark PRR) was an American railroad that was founded in 1846 and merged in 1968 into Penn Central Transportation. ...
In physics, superheating (sometimes referred to as boiling retardation, boiling delay, or defervescence) is the phenomenon in which a liquid is heated to a temperature higher than its standard boiling point, without actually boiling. ...
1876 map The Baltimore and Ohio Railroad (B&O) is one of the oldest railroads in the United States, with an original line from the port of Baltimore, Maryland west to the Ohio River at Wheeling, West Virginia and Parkersburg, West Virginia. ...
Tender may mean: one of several types of boat or ship, all sharing the general function of servicing another type of air or sea vessel: seaplane tender - supplies and services seaplanes submarine tender - resupplies submarines motor torpedo boat tender - resupplies motor torpedo boats ships tender - used to transport people...
Class Names Most locomotives were given simple codes, but some classes were named, formally or not. - The Union Pacific Big Boy class was said to have been given that name when it was scrawled on the smokebox of one at the factory.
- The Baltimore and Ohio Railroad P-7 class was referred to as the "President" class because initially each locomotive had the name of a United States president on the cab.
- Also on the B&O, the S and S-1 classes were referred to as "Big Sixes" because the road numbers began with 6.
Big Boy was the nickname universally applied to the Union Pacific Railroads twenty-five 4000 class 4-8-8-4 steam locomotives built between 1941 and 1944 by Alco. ...
1876 map The Baltimore and Ohio Railroad (B&O) is one of the oldest railroads in the United States, with an original line from the port of Baltimore, Maryland west to the Ohio River at Wheeling, West Virginia and Parkersburg, West Virginia. ...
For the pop band, see Presidents of the United States of America. ...
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