Soviet State 2-8-8-4 Locomotives in Russia

Class Details by Steve Llanso of Sweat House Media

Class P38 (Locobase 733)

Data from "SZD-Baureihe P38" in Wikipedia at [], last accessed 3 November 2019.

The only Mallets built for either Russian or Soviet railroads. Two engines built. A relatively light and late articulated that had high maintenance costs and was difficult to work in cold weather. A photo shows that above the usual array of drivers and valve gear and pistons and whatnot, the boiler had a streamlined nose much like a 1950s automobile from a Detroit design studio.

NB: The driver wheelbase given in Locobase is correct. Five of the six intervals between axles measured 1,625 mm (5 ft 4 in). The rear engine's wheelbase was longer than the front because of a 175 mm greater distance (1,800 mm/5 ft 10 3/4 in total ) between the third and fourth axles.

Despite the shortcomings, these big articulateds may have served the Soviet State for decades except for a decision at the 20th Party Congress of the CPSU (Communist Party of the Soviet Union) in February 1956. A defensible argument for ending steam locomotive production in favor of widespread electrification meant all design efforts would stop.

Principal Dimensions by Steve Llanso of Sweat House Media

Locobase ID733
RailroadSoviet State
CountrySoviet Union
Number in Class4
Road NumbersP38.0001-P38.0004
Number Built4
Valve GearWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft / m)32.55 / 9.92
Engine Wheelbase (ft / m)63.88 / 19.47
Ratio of driving wheelbase to overall engine wheelbase 0.51
Overall Wheelbase (engine & tender) (ft / m)
Axle Loading (Maximum Weight per Axle) (lbs / kg)45,107 / 20,460
Weight on Drivers (lbs / kg)355,782 / 161,380
Engine Weight (lbs / kg)470,995 / 213,640
Tender Loaded Weight (lbs / kg)
Total Engine and Tender Weight (lbs / kg)470,995 / 213,640
Tender Water Capacity (gals / ML)15,840 / 60
Tender Fuel Capacity (oil/coal) (gals/tons / Liters/MT)38.50 / 35
Minimum weight of rail (calculated) (lb/yd / kg/m)74 / 37
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)59.10 / 1501
Boiler Pressure (psi / kPa)213.20 / 14.70
High Pressure Cylinders (dia x stroke) (in / mm)22.64" x 31.5" / 575x800 (4)
Tractive Effort (lbs / kg)99,018 / 44913.86
Factor of Adhesion (Weight on Drivers/Tractive Effort) 3.59
Heating Ability
Tubes (number - dia) (in / mm)
Flues (number - dia) (in / mm)
Flue/Tube length (ft / m)20.34 / 6.20
Firebox Area (sq ft / m2)
Grate Area (sq ft / m2)115.17 / 10.70
Evaporative Heating Surface (sq ft / m2)4266 / 396.32
Superheating Surface (sq ft / m2)2548 / 236.71
Combined Heating Surface (sq ft / m2)6814 / 633.03
Evaporative Heating Surface/Cylinder Volume145.33
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation24,554
Same as above plus superheater percentage33,639
Same as above but substitute firebox area for grate area
Power L1
Power MT

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