The RSR's most notorious incline may have been the one at Rovniebera, but the most severe was the short connecting line from Kannohpio to Arnogčo, with a ruling gradient of 1 in 39. The early promise of the Hagans type of articulated locomotive was sufficient, despite well-publicised maintenance problems, to convince the RSR to try one on this particularly difficult line. Not one to do things by halves, Karel Belčamin ordered this, the largest Hagans ever built, from Henschel in 1904. The RSR's generous axle loadings allowed the reciprocating mechanism and frames to be made sufficiently robust to keep the engine out of the shops for a reasonable time. The Hagans drive did indeed work well, but the articulated chassis seemed to do its utmost not to follow the track. After putting up with this and other annoyances for a while, Belčamin had the engine rebuilt in 1907 into a rigid-framed tandem compound 4-8-2T, class D7. In this form the engine lasted until 1915. The 1 in 39 gradient had to wait until the coming of the class E1 0-10-0s in 1911.