Background By the early 1940s, the backbone of the Soviet passenger fleet was the class Su 2-6-2, of which more than 2,000 examples were in service. These locomotives had been designed in the 1920s and had a reputation as reliable and economical performers. Axle load was 18 tons, which permitted their use on the majority of the Soviet rail system. However they were not overly powerful (about 1500 hp), which prevented their use with longer passenger trains. In 1932 Kolomna Works began production on a new
2-8-4 locomotive, designed in 1930 and designated
class IS (for "Iosif Stalin"). The class IS had more power than the class Su (about 2500 hp) and shared many components with the
class FD 2-10-2 freight locomotive, easing repairs. It became the new premier passenger locomotive on the Soviet railway system but its higher axle loading (20.2 tons) meant that its use was restricted to only certain lines. Following the end of the
Second World War, railway traffic increased as the national economy recovered. New passenger locomotives with 18-ton axle loading were needed, as the class Su locomotives were often needed in double-headed configuration.
Design In 1946 the All-Union Scientific Research Institute of Railway Transport (VNIIZhT) published basic requirements for a new passenger locomotive. Based on results from the two primary existing types of passenger locomotive, the class C and the class IS, four possible types were proposed: • 3000 hp (equivalent to a
class UU locomotive) - either 4-8-4 or 4-6-4 wheel arrangement with 22.5 ton axle load • 2500 hp (equivalent to a class IS locomotive) - either 4-8-4 or 2-8-4 wheel arrangement with 18 ton axle load • 2000 hp (equivalent to a class L locomotive) - either 2-8-2 or 4-6-4 wheel arrangement with 18 ton axle load • 1500 hp (equivalent to a class Su locomotive) - either 4-6-2 or 2-6-4 wheel arrangement with 18 ton axle load After analyzing the various proposals, VNIIZhT workers concluded that a 4-8-4 locomotive producing 3000 hp would meet requested performance characteristics, but as a locomotive with 18-ton axle loading was needed, in 1947 Kolomna Works was given orders to design and produce a 4-8-4 with 18-ton axle loading. The design team was led by L. S. Lebedyanskiy and included engineers GA Zhilin and I. Sulimtsevym among others.
Production locomotives Since the test results were positive, Kolomna Works was given an order for a small batch of prototype locomotives. In 1953 four more locomotives were built, numbered 0002–0005, and in 1954 another locomotive numbered 0006 was constructed. Some changes were made to the design of the axle boxes, shoes and wedges; the smoke box blower utilized on the first prototype was dispensed with; and the decorative streamlining panels were simplified. Numbers 0003 and 0004 were sent to the Moscow-
Kursk line for testing, while 0002 and 0005 were tested at
Krasnoyarsk and 0006 was tested on the test track at VNIIZhT. The last steam locomotive produced at Kolomna, P36-0251, was outshopped on June 29 of that year. On the smoke box door was written "1869 - 10420 - 1956 Last steam locomotive built by Kolomna Works" (10420 being the serial number of the locomotive). == Specifications ==