Under the Whyte notation for the classification of steam locomotives, 4-6-2 represents the wheel arrangement of four leading wheels on two axles, six powered and coupled driving wheels on three axles and two trailing wheels on one axle. The 4-6-2 locomotive became almost globally known as a Pacific type after a locomotive built by the Baldwin Locomotive Works in Philadelphia was shipped across the Pacific Ocean to New Zealand.
Under the Whyte notation for the classification of steam locomotives, a 2-10-4 locomotive has two leading wheels on one axle, usually in a Bissel truck, ten coupled driving wheels on five axles, and four trailing wheels on two axles, usually in a bogie. These were referred to as the Texas type in most of the United States, the Colorado type on the Burlington Route, and the Selkirk type in Canada.
Under the Whyte notation for the classification of steam locomotives, 4-8-4 represents the wheel arrangement of four leading wheels on two axles, eight powered and coupled driving wheels on four axles and four trailing wheels on two axles. The type was first used by the Northern Pacific Railway, and initially named the Northern Pacific, but railfans and railroad employees have shortened the name since its introduction. It is most-commonly known as a Northern.
Under the Whyte notation for the classification of steam locomotives, 2-10-0 represents the wheel arrangement of two leading wheels on one axle, ten powered and coupled driving wheels on five axles, and no trailing wheels. This arrangement was often named Decapod, especially in the United States, although this name was sometimes applied to locomotives of 0-10-0 "Ten-Coupled" arrangement, particularly in the United Kingdom. Notable German locomotives of this type include the war locomotives of Class 52.
Under the Whyte notation for the classification of steam locomotives, 2-10-2 represents the wheel arrangement of two leading wheels, ten powered and coupled driving wheels, and two trailing wheels. In the United States and elsewhere the 2-10-2 is known as the Santa Fe type, after the Atchison, Topeka and Santa Fe Railway that first used the type in 1903.
Under the Whyte notation, a 2-8-4 is a steam locomotive that has two unpowered leading wheels, followed by eight coupled and powered driving wheels, and four trailing wheels. This locomotive type is most often referred to as a Berkshire, though the Chesapeake and Ohio Railway used the name Kanawha for their 2-8-4s. In Europe, this wheel arrangement was mostly seen in mainline passenger express locomotives and, in certain countries, in tank locomotives.
Locomotive classification on the Pennsylvania Railroad took several forms. Early on, steam locomotives were given single-letter classes. As the 26 letters were quickly assigned, that scheme was abandoned for a more complex system. This was used for all of the PRR's steam locomotives, and — with the exception of the final type bought — all electric locomotives also used this scheme.
The Pennsylvania Railroad (PRR) class I1s steam locomotives were the largest class of 2-10-0 "Decapods" in the United States. From 1916 to 1923, 598 locomotives were produced. They were the dominant freight locomotive on the system until World War II and remained in service until 1957. Nicknames for the type included Decs and Hippos, the latter due to their large boiler.
The M1 was a class of steam locomotive of the Pennsylvania Railroad (PRR). It was a class of heavy mixed-traffic locomotives of the 4-8-2 "Mountain" arrangement, which uses four pairs of driving wheels with a four-wheel guiding truck in front for stability at speed and a two-wheel trailing truck to support the large firebox needed for sustained power. Although built for both passenger and freight work, they spent most of their service lives hauling heavy high-speed freight trains. Many PRR men counted the M1 class locomotives as the best steam locomotives the railroad ever owned.
The Pennsylvania Railroad's S2 class was a steam turbine locomotive designed and built in a collaborative effort by Baldwin Locomotive Works and Westinghouse Electric & Manufacturing Company, as an attempt to prolong the dominance of the steam locomotive by adapting technology that had been widely accepted in the marine industry. One was built, #6200, delivered in September 1944. The S2 was the sole example of the 6-8-6 wheel arrangement in the Whyte notation, with a six-wheel leading truck keeping the locomotive stable at speed, eight powered and coupled driving wheels, and a six-wheel trailing truck supporting the large firebox. The S2 used a direct-drive steam turbine provided by the Westinghouse Electric & Manufacturing Company, geared to the center pair of axles with the outer two axles connected by side rods; the fixed gear ratio was 18.5:1. Such design was to prevent energy loss and S2 achieved a mechanical efficiency of 97% which means only 3% of steam energy was lost within the propulsion equipment. The disadvantage of a direct-drive steam turbine was that the turbine could not operate at optimal speeds over the locomotive's entire speed range. The S2 was the largest, heaviest and fastest direct-drive turbine locomotive design ever built.
The PRR S1 class steam locomotive was a single experimental duplex locomotive of the Pennsylvania Railroad. It was designed to demonstrate the advantages of duplex drives espoused by Baldwin Chief Engineer Ralph P. Johnson. The S1 class was the largest rigid frame passenger steam locomotive ever built. The streamlined Art Deco styled shell of the locomotive was designed by Raymond Loewy.
The GER Class A55 or Decapod was an experimental steam locomotive with an 0-10-0T wheel arrangement designed by James Holden for the Great Eastern Railway. It was the first ten-coupled steam locomotive in Great Britain.
The Pennsylvania Railroad's class N2sa comprised rebuilds to PRR practice of the 130 USRA Heavy Santa Fe steam locomotives the railroad received under the auspices of the United States Railroad Administration, the nationalized central control of the nation's railroads during World War I. These locomotives, as received, were classified N2s. Rebuilds began from 1923 and all locomotives were rebuilt, classified N2sa after the rebuild. They received a Belpaire firebox, the PRR-standard smokebox front, a raised headlight following PRR practice, and the bell moved from smokebox front to boiler top. Brakemen's "doghouse" shacks were built on the rear tender decks.
St. Louis–San Francisco 4018 is a class USRA Light 2-8-2 "Mikado" steam locomotive which operated for three decades hauling freight between Bessemer and Birmingham, Alabama, on the St. Louis–San Francisco Railway. It went on display at the Alabama State Fairgrounds in 1952 and is one of only a few locomotives of its type that survive.
The Pennsylvania Railroad G5 is a class of 4-6-0 steam locomotives built by the PRR's Juniata Shops in the mid-late 1920s. It was designed for passenger trains, particularly on commuter lines, and became a fixture on suburban railroads until the mid-1950s.
The Russian locomotive class Ye, and subclasses Yea, Yek, Yel, Yef, Yem, Yemv and Yes were a series of 2-10-0 locomotives built by American builders for the Russian railways in World War I and again in World War II. They were lightweight engines with relatively low axle loadings.
A duplex locomotive is a steam locomotive that divides the driving force on its wheels by using two pairs of cylinders rigidly mounted to a single locomotive frame; it is not an articulated locomotive. The concept was first used in France in 1863, but was particularly developed in the early 1930s by the Baldwin Locomotive Works, the largest commercial builder of steam locomotives in North America, under the supervision of its then chief engineer, Ralph P. Johnson.
The Southern Railway Ss was a class of 2-10-2 "Santa Fe" type steam locomotives built in 1917 and 1918 for the Southern Railway (SOU). They were assigned to haul and bank heavy freight trains over the Saluda Grade and Old Fort Loops in the Blue Ridge Mountains of North Carolina.
The Baldwin Class 12-42-F was a class of 2-10-0 "Decapod" type steam locomotives that were built by the Baldwin Locomotive Works for only four railroads all across the United States of America between 1924 and 1930.
The Norfolk and Western Y3 Class was a class of 2-8-8-2 "Mallet" articulated steam locomotives with a total of 80 locomotives built for the Norfolk and Western Railway between 1919 and 1923.
