Class 645A 2-12-4T (2017)

During the second decade of the 21st century the lack of a modern tank locomotive for semi-fast and suburban passenger haulage made itself increasingly felt. The most recent previous design in this category was the class 434F 4-8-4T of 1986, and the one before that Ketterik's notoriously unsuccessful 533A 2-10-4T of 1968. Numerous voices were saying that Artur Gorote was devoting too much effort to heavy freight engines which, although necessary to enable the RSR to play its part in the Europe-wide rail freight network, were hardly suitable for more mundane domestic duties. Hence the 645A shown above. The need for smart acceleration from frequent station stops was met by small driving wheels, for which the Withuhn inside coupling rods eliminate the problem of balancing, and three-stage compound expansion. The high and medium-pressure cylinders are under the smokebox. The medium pressure-exhaust is resuperheated before passing to the low-pressure cylinders under the coal bunker. There is just enough room between the front bottom edge of the firebox and the inside cranks to route the steam pipes to the rear cylinders. An alternative 4-12-2T scheme had to be rejected for this reason. The long wheelbase is helped through curves by a Krauss-Helmholtz bogie at the front end. The second and fifth coupled axles have no sideplay. The third and fourth pair of driving wheels also have no sideplay, since the axles are cranked for the inside coupling rods, and thus are without flanges. The fifth pair of driving wheels have narrower flanges. Thus the engine is guided in each direction by three axles in all. The locomotive is fitted with piston valves and Walschaerts valve gear. Whether this portends the end of poppet valves remains to be seen.

The first two locomotives were delivered in February 2017 and allocated to Plizif shed, from where they were tried on the exacting Bevice suburban network with its closely-spaced stations and tight schedules. On stopping trains they exceeded expectations but on semifast work they tended sometimes to be somewhat short of steam. Every station stop affords a short respite, even if only of a few minutes, to regain full steam pressure. On a longer run, however, the boiler gradually falls behind demand. Gorote's solution was simple - a larger boiler. The result was the 645B shown below.

The larger-boilered engines were an immediate success and no problems with shortage of steam have been experienced with them, even on such long runs as the northern circuit between Tupfdu Rulauriku and Fetihl. Their performance has been equally impressive on the mountainous route between Nadskehla and Spenocek. A total of sixty of these engines were constructed. The two initial 645As were rebuilt to class 645B when their boilers came due for replacement.