SŽD Class AA20

Soviet Railways Class AA20
А. Андреев (Andreyev), the only 4-14-4 locomotive ever built
Technical specifications
Manufacturer(s)	Voroshilovgrad Locomotive Factory
Build date	1934
Total produced	2 (Originally, though only one was finished due to the production of the Soviet Union's Powerful FD Class)
Classification	AA20
Rail gauge	5 Foot
Valve gear	Walschaerts
Cylinders	Two, outside
Bore stroke	740 mm × 810 mm (29.13 in × 31.89 in)
Firegrate area	12 m2 (130 sq ft)
Fuel type	Steam (Cheap Coal & Normal Water)
Heating area	174 m2 (1,870 sq ft)
Performance figures
Maximum speed	43mph (or 70km/h)
Tractive effort	320 kN (71,940 lbf)
Service information
Years in-service	1934-1935
Running numbers	AA20-1
Scrapped	1960
Disposition details
Preserved	Not Preserved
Disposition	Scrapped in 1960

The SŽD Class AA20 is the only steam locomotive with a 4-14-4 wheel arrangement. It was labelled and numbered as the "AA20-1". It was built by Krupp and modified by the Voroshilovgrad Locomotive Factory in Luhansk, Ukraine and it was delivered to the Soviet Union when its construction was completed.

Beginning

In the early 1930s, a group of Soviet Engineers travelled to the United States of America where they saw the 9000 Class 4-12-2 Steam locomotives, and they took massive interest in the design, They decided to try the idea and enlarge it into a locomotive with 14 coupled driving wheels.

Once the design was officially approved by the Soviet Government, official construction had began for two examples by Krupp in Germany. But due to the factory producing the Soviet's more powerful FD Class of 2-10-2s, only one was completed and it had began its life as a 4-14-2, That locomotive was eventually taken to the Voroshilovgrad Locomotive Factory in Luhansk, Ukraine, where it was given a two-axle trailing bogie, thus making it a 4-14-4.

Flaws

Unlike the successful Union Pacific 9000 Class 4-12-2s, however, the AA20-1 failure in design.

Due to the long length of the locomotive's wheelbase, it caused the tracks to bend, which made the locomotive prone to derailing constantly on the tracks due to its weight. It also broke points and switches as it passed over as it would also bend the track outwards. It was also too big for turntables and sometimes broke couplers due to its immense power. It also was prone to steaming problems, due to it using low-quality coal for a large boiler.

The Soviet Union tried to limit the derailing problem by removing the flanges on the three middle driving wheels, and adding side-to-side motion abilities on the front and rear axles. However, these changes were futile.

Ending

The AA20-1 made a publicity trip to Moscow in 1935. A few decades later, it was then put into storage at the Shcherbinka test facility where it rested in storage for until it was quietly scrapped in 1960, though this was not stated publicly.

However, its record of being the largest non-articulated steam locomotive in the world would soon be lost after the Pennsylvania Railroad Class S1 was built.

Trivia

• Regarding Technical Specifications, the AA stood for Andrey Andreyev, and the 20 denoted it's 20-ton axle load.
• The AA20 holds two records: the first being the largest number of coupled axles on a locomotive, and the second being the longest rigid frame locomotive in Europe.
• The Union Pacific Railroad had built and used 4-12-2 locomotives of the "9000" type, referred to as the "Union Pacific" class, as they were the only railroad to use them. The 4-14-4 wheel arrangement could be viewed as an expansion of that type.

Gallery

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WheelArrangement 4-14-4.svg