SA3 coupler

The SA3 coupler is a type of railway coupling used mainly, but not exclusively, in Russia and other states of the former Soviet Union.

Railways in Russia used European (British) buffers and chain couplings from their inception. These couplings had three main limitations. Firstly the load was limited. Secondly, the couplings were not semi-automatic like the North American Janney AAR coupler. Thirdly, the buffers could get buffer-locked and cause accidents. Advantages and disadvantages of these couplings are intermediate between Janney AAR couplers and Scharfenberg couplers.

It took a while to find a replacement. One option was to copy the Janney AAR coupling, as Japan (1922), Australia (1915) and other countries were starting to do, or to devise something else. The Soviets were not afraid to copy, as they had imported many engines and engineers during the various five year plans. In the end they chose the SA3, although implementation was delayed by World War II.

The Willison coupler was patented by John Willison from Derby, England. It was registered in 1910, and approved in USA 1916, and in Germany. The company Knorr bought it and it started to be used in Germany for some heavy trains and some suburban trains in Paris. The Soviet Union needed a new coupler and decided to use this coupler.

In the late 1920s, the UIC had established a working group for the replacement of the chain link coupler, which restricts the efficiency of freight railroads in a major way. Many railroads ran prototypes. In Germany, coal trains with Scharfenberg couplers yielded unfavourable results in winter weather, other railroads did similar tests. But the UIC was not able to agree on one replacement. This failure of the UIC, which hampers freight operation in Europe even today, led to the decision by the Soviet Union to move forward without a standard being achieved in the talks.

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