SM25

 

 

SM25-002 (Fablok 5427/1962), photographed at the Railway Museum in Warsaw in May 2001.

 

 

Another photo of this machine, taken on May 25, 2005.

 

 

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 Poland and had to be purchased abroad; the choice fell on Austrian J.M.Voith A.G., one of leading European companies in this field.

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 Railway Museum in Warsaw and still can be seen there as a sole surviving example of this class.

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

 

No.

Parameter

Unit

Value

1.

Years of manufacture

-

1960 – 1963

2.

Total built / used in Poland

-

3 / 3

3.

Axle arrangement

-

C

4.

Transmission type

-

hydraulic

5.

Design maximum speed

km/h

60

6.

Prime mover type

-

1DVSa/31

7.

Engine rating

kW/hp

257 / 350

8.

Bore X stroke

mmXmm

150 X180 / 186.71)

9.

Number of cylinders

-

12

10.

Number of electric engines

-

-

11.

Rated output of electric engines

kW

-

12.

Main reduction gear ratio

-

-

13.

Diameter of drivers

mm

850

14.

Total weight

kg

37 400

15.

Axle load

T

12.4

16.

Axle base

mm

4 200

17.

Overall length

mm

8 644

18.

Maximum width

mm

3 150

19.

Train heating

-

-

20.

Brake type

-

Knorr

 

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.