Soviet State 4-14-4 Locomotives in Russia

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."