Soviet State 4-6-4 Locomotives in Russia

Class Details by Steve Llanso of Sweat House Media

Class 2-3-2 (Locobase 736)

First two of a proposed class of ten streamliners intended to work the Moscow-Leningrad line's Krasnaya Strela (Red Arrow). No. 1 hit 106 mph in test run on 29 June 1938.#2 had different superheater and boiler tubes; it operated until 1957-1958.

Class 2-3-2V (Locobase 737)

Data from 2-3-2B [V]" in Wikipedia at [], last accessed 21 September 2023.

Similar to Class V engines, but with much bigger drivers. 6998 developed 3,400 hp during a test in which it pulled a 900-ton train up a 0.6% grade that it entered at 110 kph (68.3 mph) and topped out at 76 kph (47.2 mph).

Wikipedia places this single locomotive in the context of Soviet State Railways wishing to increase the power and maximum speed of its express locomotives. The 1932 design of IS 2-8-4s (Locobase 4352) offered a good level of power, but was limited in its speed. So Lvov, the Voroshilovgrad Works's design engineer developed a locomotive that borrowed from existing engines like the FD (Locobase 727) and IS, but explored the value of taller drivers and streamlining.

Collaboration with what Google translates as the "Moscow Aviation Institute's" wind tunnel resulted in the profile visible in photographs.The design's streamlining thrust a large hemispherical nose forward of the front buffers. Its obtrusiveness wasn't helped by the use of a large, silver star surrounding the single, centered headlight. Much of the rest of the sheathing fell in line with streamline designs in several other countries. A smooth glacis under the nose hid cylinder heads and air brake pumps. A valence below a high running board that continued back to below the cab exposed all of the running gear.

Lvov's economy in design centered on using "most of the elements of the steam boiler [tubes, firebox, and other fittings], cylinders, rear bogie frame, axle liners and wedges, as well as much more." Thus, if the 2-3-2 B operated from depots that also ran FDs or IS locomotives, most repairs would use already existing stores. Innovation included high-strength steel in the frame, much of which was welded. Steel alloys in the motion, all axles turned in roller bearings, and drivers eschewed spokes by adopting discs similar to those of Boxpok or Baldwin.

Once in service in June 1938, limited tests such as the one described above showed promise at a cost of a 15% increase in fuel consumption "per unit of work." But the 6998's potential could not be fully sampled "and its thermal performance were never fully studied." After the end of the Great Patriotic War in 1945, the SDZ removed the shroud and limited speeds to 70 kph (43.5 mph). Obviously, some engineers wondered just what its upper speed limit might be, so the railway coupled a special train to the 6998 in 1957 and set a Soviet steam traction record of 175 kph (108.7 mph).

6998 was retired in 1963 and scrapped.

Principal Dimensions by Steve Llanso of Sweat House Media

Locobase ID736 737
RailroadSoviet StateSoviet State
CountrySoviet UnionSoviet Union
Number in Class21
Road Numbers16998
Number Built21
Valve Gear
Locomotive Length and Weight
Driver Wheelbase (ft / m)16.08 / 4.90
Engine Wheelbase (ft / m)55.35 / 16.87
Ratio of driving wheelbase to overall engine wheelbase 0.29
Overall Wheelbase (engine & tender) (ft / m)96.39 / 29.38
Axle Loading (Maximum Weight per Axle) (lbs / kg)42,600 / 19,32347,399 / 21,500
Weight on Drivers (lbs / kg)142,198 / 64,500
Engine Weight (lbs / kg)247,000 / 112,037304,238 / 138,000
Tender Loaded Weight (lbs / kg)
Total Engine and Tender Weight (lbs / kg)
Tender Water Capacity (gals / ML)12,936 / 49
Tender Fuel Capacity (oil/coal) (gals/tons / Liters/MT)24.20 / 22
Minimum weight of rail (calculated) (lb/yd / kg/m)79 / 39.50
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)78.70 / 199986.60 / 2200
Boiler Pressure (psi / kPa)213 / 14.70213.20 / 14.70
High Pressure Cylinders (dia x stroke) (in / mm)22.81" x 27.56" / 579x70026.38" x 30.31" / 670x770
Tractive Effort (lbs / kg)32,988 / 14963.1244,139 / 20021.14
Factor of Adhesion (Weight on Drivers/Tractive Effort) 3.22
Heating Ability
Tubes (number - dia) (in / mm)
Flues (number - dia) (in / mm)
Flue/Tube length (ft / m)
Firebox Area (sq ft / m2)
Grate Area (sq ft / m2)70 / 6.5175.78 / 7.04
Evaporative Heating Surface (sq ft / m2)2669 / 248
Superheating Surface (sq ft / m2)1281 / 119
Combined Heating Surface (sq ft / m2)3950 / 367
Evaporative Heating Surface/Cylinder Volume139.20
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation14,91016,156
Same as above plus superheater percentage14,91021,326
Same as above but substitute firebox area for grate area
Power L1
Power MT

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