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![]() The Baltimore and Ohio Railroad's #5600 George H. Emerson. | |||||||||||||||||||||
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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.
The first locomotive built with this arrangement was the Baltimore and Ohio Railroad's sole class N-1 #5600 George H. Emerson, constructed at the B&O's own Mount Clare Shops in May 1937. To reduce the fixed wheelbase, this locomotive had the two sets of cylinders at opposite ends, so that the rear pair were beside the firebox. The firebox was an unconventional water tube design which was tested well on other locomotives and needed a large space. The 4-4-4-4 wheel arrangement proved to be a poor design, as it restricted the firebox size and exposed the cylinders to dust and dirt, causing premature wear. The locomotive was not considered successful enough to duplicate. The sole N-1 was retired in 1943 and scrapped in 1950. [1]
The next locomotives to use the 4-4-4-4 arrangement were the Pennsylvania Railroad's 52 class T1 locomotives (although the single class S1 was originally intended to be a 4-4-4-4, it was later changed to 6-4-4-6 due to increased weight). These had the cylinders in front of the wheels they drove, so that the rear pair were between the two sets of drivers. These locomotives were impressive performers but suffered from wheelslip and severe reliability problems, and did not last long in service. [2]
The two prototypes, #6110 and #6111, were constructed at the Baldwin Locomotive Works in April 1942. The mechanical design work had been undertaken by Baldwin's chief engineer Ralph P. Johnson, while the streamlining was the handiwork of industrial designer Raymond Loewy. [2] [3] Both locomotives showed fantastic performance in test trials, leading to the construction of 50 further examples. Numbers 5500 through 5524 would be constructed at the PRR's Altoona Works while 5525 through 5549 would be constructed at Baldwin.
As operation continued, problems arose. The T1 class was known for violent uncontrollable wheel slip as well as performance and maintenance issues caused by the Franklin oscillating-cam Poppet valves. [4] The PRR did show interest in trying to solve these problems such as replacing the original poppets on #5500 with easier to maintain Franklin rotary-cam poppet valves and refitting #5547 with Walschaerts valve gears reclassifying the latter engine as a "T1a". [4]
The PRR decided to stop development of the T1 class, replacing all examples by the mid-1950s with diesel units. All members of the class were scrapped. It is very likely the T1 may have had many of its shortcomings solved had the PRR not retired the short-lived class so soon. [4] During its short service life, the T1 was rumored to have operated at higher speeds than the steam speed record set by the London and North Eastern Railway's Mallard, but the claims could not be officially verified. [5]
Several bush tramway engine types were built with this wheel arrangement. These were known as "16-Wheelers". Two notable New Zealand-based builders were J. Johnson and Sons Ltd. in Invercargill and A & G Price in Thames.
Only one locomotive of the 4-4-4-4 arrangement is being constructed. When finished, PRR 5550 will be the 53rd and only surviving example of the PRR T1 class rather than a replica. The new build T1 is expected to implement some design improvements to help aid in solving problems encountered by the original 52. The estimated date of project completion is currently set to be around 2030. [6] As of November 2023, the project is 43.3% complete with an estimated total cost of US $7,000,000. [7]
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 New Zealand locomotive that was shipped across the Pacific Ocean.
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, 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.
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) K4 4-6-2 "Pacific" was its premier passenger-hauling steam locomotive from 1914 through the end of steam on the PRR in 1957.
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 (PRR) class T1 duplex-drive 4-4-4-4 steam locomotives, introduced in 1942 with two prototypes and later in 1945-1946 with 50 production examples, were the last steam locomotives built for the PRR and arguably its 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, in addition to being complicated to maintain and expensive to run. The PRR decided 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 units.
The Pennsylvania Railroad's class B6 was its most successful class of switcher locomotive, or as the PRR termed them "shifter". The PRR preferred the 0-6-0 wheel arrangement for larger switchers, whereas on other railroads the 0-8-0 gained preference. The PRR generally used 2-8-0s when larger power was required.
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. It was the longest and heaviest rigid frame reciprocating steam locomotive that was ever built. The streamlined Art Deco styled shell of the locomotive was designed by Raymond Loewy.
The New York Central Railroad's Niagara was a class of 27 4-8-4 steam locomotives built by the American Locomotive Company for the New York Central Railroad. Like many railroads that adopted different names for their 4-8-4s rather than “Northerns”, the New York Central named them “Niagaras”, after the Niagara River and Falls. It is considered as one of the most efficient 4-8-4 locomotives ever built.
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 mainly 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 National Museum of Transportation in St Louis, Missouri.
The Pennsylvania Railroad's class R1 comprised a single prototype electric locomotive constructed in 1934 by the Baldwin Locomotive Works of Philadelphia, Pennsylvania, US, with the electrical equipment by Westinghouse.
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.
The Pennsylvania Railroad class Q1, #6130, was a single experimental steam locomotive designed for dual service. The locomotive entered service in 1942, and retired in 1949 after accumulating a relatively low 165,000 service miles.
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 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 and 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.
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.
Pennsylvania Railroad 5550 is a mainline duplex drive steam locomotive under construction in the United States. With an estimated completion by 2030, the locomotive will become the 53rd example of the Pennsylvania Railroad's T1 steam locomotive class and the only operational locomotive of its type, as well as the largest steam locomotive built in the United States since 1952. The estimated cost of PRR 5550 was originally $10 million, but an updated projected cost of $7 million was released with the acquisition of an existing long-haul tender from the Western New York Railway Historical Society in August 2017. Construction began in 2014 with the casting of the locomotive's keystone-shaped number plate. As of February 2024 the locomotive was 43% complete.
The Pennsylvania Railroad's class K29s comprised a single experimental 4-6-2 "Pacific" type steam locomotive. Constructed by Alco-Schenectady, it was given road number 3395. Although only one demonstrator was constructed, the K29s would become the basis for the highly successful K4s Pacifics and L1s Mikados. The lone example spent most of its life on the PRR's Pittsburgh division main line and was retired around 1929.