SM25-002 (Fablok 5427/1962), photographed at the
Another photo of this machine, taken on
SM25 prototype side drawing by M.Ćwikła (source: SK vol.9/2001).
SM25-001, location and date unknown (looks like a factory photo). Photo from my collection.
Design of the first Polish diesel
locomotive with electric transmission, designated 1D, was completed in 1955
and prototype, with factory designation Ls300, was rolled out in 1956.
Production both for PKP (classed LWe55, later SM30) and industry
lasted until 1970 and totaled over 900 examples. SM30 has been widely used as
a light switcher, sometimes also with light local trains, despite being
neither modern nor entirely satisfactory. In particular, at an early stage it
was argued that hydraulic transmission was more suitable for light and medium
diesel locomotives. It was therefore decided to build such machine, as a
possible future replacement for SM30. In fact, attempts to produce light
diesel locomotives with hydraulic transmission were undertaken before the
war, but prototypes were not completed until September 1939. Hydraulic torque
converters were not manufactured in
Construction of the prototype with factory designation 9D (s/n 5030/1961, PKP class SM25), fitted with Voith L26/St/V-03 transmission gear, began at Fablok in January 1960 and was completed in mid-1961. Tests were performed between July and December 1961 and results were considered basically satisfactory. Reservations concerned mainly the prime mover: power was provided by the Wola 1DVSa/31 V12 unit rated at 350 hp, a slightly improved variant of the engine used in SM30, which was certainly obsolescent. More modern, medium speed diesel engines, more suitable for this type of transmission, were then still under development. There were also some remarks concerning several minor items of equipment, but new locomotive was obviously superior to SM30: tractive effort at startup increased from 7 960 to 13 800 kG despite only marginally higher power. Due to three axles in the C layout (power transmitted via an idle shaft and side rods) instead of Bo’Bo’ in SM30, axle load was higher (12.4 tonnes), despite slightly lower weight, but SM25 was still suitable for weak secondary tracks.
First prototype SM25-001 was
followed by SM25-002 (Fablok
5427/1962), accepted by PKP in December 1962, and SM25-003 (Fablok 5428/1963) in July 1963. All
three examples were based in Kraków and used mainly for switching. Their fate
was, however, doomed by the fact that no Polish manufacturer was then able to
produce hydraulic torque converters, which were very demanding from the
technological point of view, and import for series production was out of
question. Three SM25s spent most of their service lives awaiting spares,
which were always in short supply; no wonder, thus, that they were withdrawn
pretty soon. SM25-001 was written off in late 1970 and SM25-003 followed only
a few months later; it ended up in a gravel mine and was finally scrapped in
1976. SM25-002 was withdrawn from PKP service in late 1973 and handed
over to the SFA bus factory in Sanok, but it is not clear if it was
ever brought there. In September 1980 it was finally transferred to the
Next – and final – attempt to introduce hydraulic transmission in Polish diesel locomotives came in 1963, when two 750 hp Soviet TGM3s were purchased and their license production (55 examples) began at Fablok. These machines, designated SM15, were fitted with imported engines and transmission gears. They soon proved extremely unreliable and last of them survived in service only until 1978. Electric transmission thus remained the sole alternative and in 1966 prototype 401D light switcher appeared, with axle arrangement similar to that of SM25, but fitted with electric transmission (first and third driven axles with side rods). It finally entered production as 401Da (with more modern license-built Henschel engine), supplanting the obsolete SM30, but has never been ordered by PKP.
Main technical data
1) Master / articulated connecting rods.
References and acknowledgments
Detailed description can be found in the monographic article by Paweł Terczyński in SK vol.9/2001.