Soviet State 4-14-4 Locomotives in Russia

Class Details by Steve Llanso of Sweat House Media

Class AA-20 (Locobase 4818)

Data from [] corrected by November 1935 article in Railway Mechanical Engineer written by D. Babenko. RME notes that this is a translation of an article that appeared in The Motive Power, published in Moscow.

A masterpiece of Soviet gigantism. Although properly proportioned, it was just too big. Also, its 13"-diameter piston valves might have been undersized for such large cylinders. The main rod reached back to the fourth axle and that was still only to the middle of the set of drivers. Babenko notes that the grate is so big because the fuel had such low caloric value. Adding the combustion chamber to the firebox (which itself had four arch tubes) increased the direct heating surface to 865.2 cu ft.

Drivers had lateral motion as follows:

1st and 2nd 1 1/16" to each side

7th 1 3/8"

The tires on the 3rd, 4th, and 5th axles were flangeless.

So the only flanged and laterally immobile axle was the 6th.

In any event, the experiment wasn't repeated, either by the Soviet Union or by anyone else. According to Wes Barris ([]), it made one test run and tore the track up.

Stephen Karlson ([]) comments "[One] faction favored a more powerful locomotive, and to keep the axle loadings within limits, providing additional driving axles." The class ID, says Karlson, stood for A. Andreyev, 20 (metric) ton axle loading, first of series.

"Like John Armstrong's 4-6-6-6," says Karlson," it was three engines: first of class, last of class, and only of class. I have found a photograph of it in the Scherbinka yard that supposedly dates to the early 1950s, shortly before it went for scrap."

Principal Dimensions by Steve Llanso of Sweat House Media

Locobase ID4818
RailroadSoviet State
CountrySoviet Union
Number in Class1
Road NumbersAA-20-1
Number Built1
Valve GearWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft / m)32.97 / 10.05
Engine Wheelbase (ft / m)56.92 / 17.35
Ratio of driving wheelbase to overall engine wheelbase 0.58
Overall Wheelbase (engine & tender) (ft / m)100.45 / 30.62
Axle Loading (Maximum Weight per Axle) (lbs / kg)44,092 / 20,000
Weight on Drivers (lbs / kg)308,560 / 139,961
Engine Weight (lbs / kg)458,435 / 207,943
Tender Loaded Weight (lbs / kg)275,500 / 124,965
Total Engine and Tender Weight (lbs / kg)733,935 / 332,908
Tender Water Capacity (gals / ML)11,620 / 44.02
Tender Fuel Capacity (oil/coal) (gals/tons / Liters/MT)24.20 / 22
Minimum weight of rail (calculated) (lb/yd / kg/m)73 / 36.50
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)63 / 1600
Boiler Pressure (psi / kPa)246.60 / 17
High Pressure Cylinders (dia x stroke) (in / mm)29.13" x 31.89" / 740x810
Tractive Effort (lbs / kg)90,034 / 40838.78
Factor of Adhesion (Weight on Drivers/Tractive Effort) 3.43
Heating Ability
Tubes (number - dia) (in / mm)138 - 2.75" / 70
Flues (number - dia) (in / mm)48 - 6.75" / 171
Flue/Tube length (ft / m)22.96 / 7
Firebox Area (sq ft / m2)595.40 / 55.33
Grate Area (sq ft / m2)129.20 / 12
Evaporative Heating Surface (sq ft / m2)4823 / 448.23
Superheating Surface (sq ft / m2)1873 / 174.07
Combined Heating Surface (sq ft / m2)6696 / 622.30
Evaporative Heating Surface/Cylinder Volume196.07
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation31,861
Same as above plus superheater percentage40,782
Same as above but substitute firebox area for grate area187,937
Power L125,954
Power MT1298.07

All material Copyright ©
Wes Barris