Soviet State 2-6-2 Locomotives in Russia

Class Su (Locobase 731)

Data from [] (a Ukrainian website organizing steam tours) for the data. Dzherelo says the information comes from Anthony J. Heywood & Jan D.C. Button, Soviet Locomotive Types: The Union Legacy (1995); and updated and expanded by "Diagrams [of] Locomotives and Tenders", published in Moskva (Moscow), 1935 p. 132-133, PDF supplied by Teemu Koivmaki in his 5 October 2019 email. (Many thanks to Teemu for sending what might never have fallen into Locobase's hands. An indispensable addition to Locobase's library.). See also "'Prairie' Type Locomotives for the Russian Soviet Railways", Locomotive Magazine, Volume XXXVIII [38], Number 475 (15 March 1932), pp. 77-78.

A Soviet-era follow-on to the S class begun in 1911 and the Sv's that came out in 1915. Su stands for (S, strengthened) . Compensated springing included fulcrums that could be adjusted to reduce maximum axle load from 18 tonnes (39,360 lb) to 16 tonnes (35,280 lb) -- also reducing adhesive weight by 6 tonnes (13,230 lb). Kolomna Works produced a development of the widely-used Kraus-Helmholtz bogie, which combined the leading truck and the first coupled axle in a single traversing unit.

The steel Belpaire firebox is prominent in photographs as is the long gap between the last driver and the trailing axle. The Soviet diagram shows the valve diameters as 250 mm (9.84") each. LM explained that the Soviet superheater differed from the usual Schmidt design having six supeheater tubes in each flue instead of the usual four.

The design also used a feed water heater mounted in the front of the boiler. LM contended that pre-heating the water softened the exhaust and "a more even blast secured on the fire, so that there is little spark throwing." The firebox could be fitted with grates for coal or an oil-burner and Su class engines were delivered as one or the other.

550 were built from 1926-1931 (Type 1) and were the first design from L [Lev] S Lebedyansky, the most noteworthy 20th-Century locomotive designer. 1,850 followed in 1932-1941 (Type 2, Type 3, and Sum) and, after the Great Patriotic War, 1,350 more were built in 1947-1950 (Type 4). The data for Type 4 in the specs can be considered representative. Most still active in 1960, 886 still in use in 1967 and considered highly successful locomotives.