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.
The Pennsylvania Railroad's 52 T1 class duplex-drive 4-4-4-4 steam locomotives, introduced in 1942 and 1945-1946, were their last steam locomotives built and their most controversial. They were ambitious, technologically sophisticated, powerful, fast and distinctively streamlined by Raymond Loewy. However, they were also prone to wheelslip both when starting and at speed, complicated to maintain and expensive to run. The PRR vowed in 1948 to place diesel locomotives on all express passenger trains, leaving unanswered questions as to whether the T1's flaws were solvable, especially taking into account that the two prototypes did not have the problems inherent to the production unit. An article appearing in a 2008 issue of the Pennsylvania Railroad Technical and Historical Society Magazine showed that inadequate training for engineers transitioning to the T1 may have led to excessive throttle applications, resulting in driver slippage. Another root cause of wheelslip was faulty spring equalization. The drivers were equalized together and not equalized with the engine truck. In the production fleet the PRR equalized the engine truck with the front engine and the trailing truck with the rear engine, which helped to solve the wheelslip problem.
A 4-4-4-4 steam locomotive, in the Whyte notation for describing locomotive wheel arrangements, has a four-wheel leading truck, two sets of four driving wheels, and a four-wheel trailing truck. While it would be possible to make an articulated locomotive of this arrangement, the only 4-4-4-4s ever built were duplex locomotives—with two sets of cylinders driving two sets of driven wheels in one rigid frame, essentially a 4-8-4 with divided drive.
A camelback locomotive is a type of steam locomotive with the driving cab placed in the middle, astride the boiler. Camelbacks were fitted with wide fireboxes which would have severely restricted driver visibility from the normal cab location at the rear.
The Pennsylvania Railroad's class B6 was its most successful class of switcher, or as the PRR termed them, "shifter". The PRR preferred the 0-6-0 wheel arrangement for larger switchers, whereas on other roads the 0-8-0 gained preference. The PRR used road locomotives, generally 2-8-0s, when larger power was required.
The Pennsylvania-Reading Seashore Lines was a railroad that operated in southern New Jersey in the 20th century. It was created in 1933 as a joint consolidation venture between two competing railroads in the region.
The Pennsylvania Railroad's class P5 comprised 92 mixed-traffic electric locomotives constructed 1931–1935 by the PRR, Westinghouse and General Electric. Although the original intention was that they work many passenger trains, the success of the GG1 locomotives meant that the P5 class were mostly used on freight. A single survivor, prototype #4700, is at the Museum of Transportation in St Louis, Missouri.
The Pennsylvania Railroad's class O1 comprised eight experimental boxcab electric locomotives built in 1930 and 1931. They were built in preparation for the New York to Washington Electrification project. They had the wheel arrangement classified as 4-4-4 in the Whyte notation. Although successful, they were not powerful enough for the railroad's increasingly heavy trains. For production, the PRR chose to concentrate on the P5 class, effectively an enlarged and more powerful version of the O1 with an additional pair of driving wheels.
The Pennsylvania Railroad's class AA1 comprised two experimental electric locomotives constructed in 1905 by the company's own Altoona Works with the assistance of Westinghouse. Intended as testbeds as the PRR began its electrification project, both locomotives remained service into the 1930s.
Pennsylvania Railroad's Odd D #10003 was an experimental electric locomotive built in 1907 by Baldwin and Westinghouse. It had an 4-4-0 wheel arrangement in the Whyte notation, or 2-B in the AAR scheme. On the PRR, class D was assigned to 4-4-0 locomotives. Production classes of locomotive were assigned a number after the letter, but one-off locomotives were simply designated "Odd".
The Pennsylvania Railroad's class Q1 comprised a single experimental steam locomotive for dual service, #6130. PRR Board approves $595,000 for the construction of this experimental Class dual service locomotive on Oct,9 1940, it was built in March 1942, its streamlined shrouding, according to an interview of noted an interview of John W. Epstein, Special Projects Manager and vice president, Raymond Loewy & AssoC.,, was designed by Raymond Lowey but due to WWII, there was no publicity about it. A duplex locomotive, it had a wheel arrangement of 4-6-4-4, comprising a four-wheel leading truck, two sets of driving wheels in a rigid locomotive frame, and a four-wheel trailing truck. The first group of six driving wheels was driven by a pair of cylinders mounted conventionally in front of them, while the rear four driving wheels were driven by cylinders mounted behind them on either side of the firebox.
Class D16 on the Pennsylvania Railroad was their final development of the 4-4-0 "American" type of steam locomotive. A total of 429 of these locomotives were built at the PRR's Juniata Shops, spread across five subclasses; some had 80 in (2,030 mm) diameter driving wheels for service in level territory, while others had 68 in (1,730 mm) drivers for mountainous terrain. In the pre-1895 scheme, these locomotives were second class L.
Class E6 on the Pennsylvania Railroad was the final type of 4-4-2 "Atlantic" locomotive built by the railroad, and second only to the Milwaukee Road's streamlined class A in size, speed and power. Although quickly ceding top-flight trains to the larger K4s Pacifics, the E6 remained a popular locomotive on lesser services and some lasted to the end of steam on the PRR. One, #460, called the Lindbergh Engine, is preserved at the Railroad Museum of Pennsylvania. It was moved indoors to begin preparations for restoration on March 17, 2010. On January 10, 2011, PRR #460 was moved to the museum's restoration shop for a two- to three-year project, estimated to cost $350,000. The engine is listed in the National Register of Historic Places.
Class D6 on the Pennsylvania Railroad was a class of 4-4-0 steam locomotive. Nineteen were built by the PRR's Altoona Works between 1881–1883. They were equipped with 78-inch (1,981 mm) drivers. Seven were later converted to 72-inch (1,829 mm) drivers and classified D6a.
Class L1s on the Pennsylvania Railroad comprised 574 2-8-2 "Mikado" type steam locomotives constructed between 1914 and 1919 by the railroad's own Juniata Shops as well as the Baldwin Locomotive Works (205) and the Lima Locomotive Works (25). It was the largest class of 2-8-2 locomotives anywhere, although other railroads had more Mikados in total.
The Pennsylvania Railroad's K4s class Pacific number 1737 was the prototype of the class of 4-6-2 steam locomotives that eventually would number 425 locomotives.
The Pennsylvania Railroad G5s was 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 G5s was the largest and most powerful 4-6-0 locomotive, except for a single Southern Pacific 4-6-0 that outweighed it by 5500 lb.
The Pennsylvania Railroad's class E2, E3, E7 steam locomotives were of the 4-4-2 "Atlantic" passenger type, frequently called “light Atlantics” after the introduction of the heavier E6 Atlantics. All were similar in size and boiler capacity but differed in firebox type, valves and valve gear, and cylinder diameter. Classes E2 and E3 were built simultaneously. Starting in 1916 a rebuilding program converted ninety class E2a,b,c to class E7s by replacing slide valves with piston valves and increasing cylinder diameter from 20.5 to 22.5 inches. Fourteen class E2 were similarly converted to class E7sa. Ninety class E2a,d, E3a,d were converted to class E3sd. These improvements allowed many of the engines to remain in active service into the 1930s.
The Pennsylvania Railroad's no. 2512 was a single de Glehn Compound 4-4-2 "Atlantic" type locomotive that the railroad imported from France in 1904.
