page_title: Pennsylvania Railroad 5550
section_title: The Original T1 Class
hierarchical_section_title: Pennsylvania Railroad 5550 / Introduction / The Original T1 Class
caption_attribution_description: English: Photo of a Pennsylvania Railroad streamlined steam locomotive T1 class. Note the photo uploaded is of better quality than the one shown in the newspaper scan. A renewal search was done in periodicals for the years 1969 and 1970. There were no listings for the Wilkes-Barre Record. There is no evidence of renewal.
context_page_description: Pennsylvania Railroad 5550 is a mainline duplex drive steam locomotive being built in the United States of America. Upon completion, estimated to be around 2030, the locomotive will be the 53rd addition to the Pennsylvania Railroad's T1 steam locomotive class. The total estimated cost of PRR 5550 was US $10,000,000, but with the acquisition of an existing long haul tender from the Western New York Railway Historical Society in August 2017, the total cost is now estimated to be closer to US $7,000,000. The project is following some of the protocols and objectives laid down during the construction of the LNER Peppercorn Class A1 steam locomotive Tornado in the United Kingdom. The T1 Trust has also worked closely with many United Kingdom based steam locomotive foundations to aid in the construction of PRR 5550. Construction of the locomotive began in 2014 with the casting of the locomotive's keystone-shaped number plate. Major components completed as of March 2019 include two Boxpok drivers, the prow, cab, third course boiler and fire door. Front tube sheet construction was underway at a St. Louis, Missouri-based fabricator.
context_section_description: The Pennsylvania Railroad's T1 class steam locomotive was one of the most unique and controversial class of locomotives ever constructed. This was due to its unusual Duplex drive 4-4-4-4 wheel arrangement, its use of the Franklin Type A oscillating-cam poppet valve and its characteristic streamlining conceived by famous industrial designer Raymond Loewy. The T1 was also the only class of Pennsylvania duplex able to travel on all of the railroad's network. The T1 was also the first production series locomotive designed to use the poppet valve. The two prototype T1 locomotives were constructed in 1942 by the Baldwin Locomotive Works, numbered 6110 and 6111 respectively. Of the production series for the T1 class, with 25 locomotives Numbered 5500 to 5524 being constructed at the Pennsylvania Railroad's Altoona Works and the other 25 locomotives Numbered 5525 to 5549 being constructed at Baldwin. In total, 52 T1 class locomotives were constructed including the two prototypes. This made the T1 the most numerous engine produced of all the Pennsylvania Railroad's duplex drive locomotives.
  The T1 class suffered from a number of performance and design issues including difficulties regarding the poppet valves used by the locomotives. The original materials used to construct the poppet valves used by the T1 had fatigue issues which were increased when the locomotives were operated above 100 miles an hour. In 1947, a higher strength and fatigue resistant alloy was used and retrofitted to the T1 class to solve the fatigue problems. Nevertheless, the design of the Franklin Type A poppet valves made several key areas of the valves hard to access during maintenance overhauls. Despite the constant issues, the poppet valves did allow the T1 to perform better than conventional valved locomotives at high speeds. The poppet valves required less horsepower for fast operation and were able to distribute steam flow with precision valve operation when going at high speeds. The T1's were further burdened by excessive wheel slip on one of the two engine sets when the locomotive operated at high speed or when the engine started moving. The Pennsylvania Railroad tried to address the problem by changing the spring bed arrangement on the T1, from being a single bed that supported only the eight drivers, to two beds; the forward bed supporting the pilot truck and first engine and the aft bed supporting the second engine and trailing truck. Despite this, a permanent solution couldn't be found to ultimately prevent violent wheel slip, even though an "anti-slip" mechanism had been installed on the PRR Q2 class duplex. It is possible that the engineers, more familiar with the K4s class were better used to the slower throttle action of the K4s, whereas the T1 reacted more immediately to the engineer's throttle input due in part to the use of poppet valves.
  Before many of the problems that plagued the T1 class could be solved, the Pennsylvania Railroad decided to begin the transition from steam power to diesel. Furthermore, the problems associated with the operation of the T1 locomotives would help to ensure an earlier retirement from service as compared to the more reliable steam engine classes such as the K4s. Between 1952 and 1953, the T1's were retired from service within the Pennsylvania Railroad. Scrapping of the T1's began in 1953. The last surviving T1's were scrapped in 1956. Consequently, the premature retirement and disposal of the T1 left several vague speed claims and performance related or technical questions unanswered.
caption: PRR 6110, the prototype for the T1 class steam locomotive built for the Pennsylvania Railroad by the Baldwin Locomotive Works seen in 1942.
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