As a Swede my English is not perfect. I just used the wrong word. By biggest I meant the size in length. And that russian engine Stalin A-20 (2-14-4) didn´t manage any curved tracks and points so it never made it into production.
"STALIN'S ENGINE: THE AA20-1. 1934
This notorious design was built at Lugansk Works, emerging in December 1934. [1] It became famous as the largest non-articulated locomotive in Europe, and in particular for having the most coupled axles in the world. A few countries produced 12-coupled designs, but nobody else tried 14. It was intended for heavy haulage on light (78 lb/yd) rails, with a modest loading of 20 tons per axle, on the Moscow-Donbass route. (The "20" in AA-20 refers to 20 tonnes per axle) It successfully made a publicity trip to Moscow in Jan 1935, but never entered service. No details are available of trial runs.
It was clear (though never publicly admitted) that the AA20 was a complete disaster. It spread the track, wrecked every set of points it passed over, and derailed almost every time it moved. Steaming was poor, and the locomotive too powerful for existing couplings and too long for the turntables.
After 1935 it was stored for 25 years at the Shcherbinka test facility and finally scrapped in 1960.
[1] Bell, writing in 1946, states that construction began as a 2-14-4 at the Krupp works in Essen, to a Soviet design, but was then transferred to Lugansk, where a leading bogie replaced the pony truck.
In (unsuccessful) attempts to get the AA-20 round curves, the middle three axles had flangeless wheels, and universal joints were include in the coupling rods between first and second, and sixth and seventh, axles."
The above article is cut out from ..." LOCO LOCO..."
