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SM31 (production model411D) is a Polish series ofdieselshunting locomotives used byPKP and industry.[1]
The SM31 class was designed forshunting heavy freighttrains in large freight stations, works andharbours. The design was elaborated inFablok in 1973, mainly on the basis ofSM42 locomotive. Production of this series lasted between 1976 and 1981, as well as between 1983 and 1985. In this periodPKP bought 167 units.[2] About 200 locomotives were produced in total, with the rest of them servicingPolish industry, chieflymining.[3] The first 2prototypes (SM31-001 and SM31-002) were sold to industrial works, and PKP's last locomotive was re-bought from an industrial user (SM31-170).[2]
As the main purpose of this series was shunting heavy freight trains, after its introduction PKP possessed shunters suited for all purposes. For extremely light trains mainlySM03 locomotives were used. Medium light trains were shunted bySM30 series, medium weight trains were left forSM42 engines. The last thing to be done was the introduction of heavy shunter able to work in severe climatic conditions, what did not happen beforeSM48 were brought to Poland.[1]
Today SM31 locomotives are mainly to be found onUpper Silesia railway tracks, pulling heavy freight trains from works tomarshalling yards inŁazy,Jaworzno,Szczakowa,Tarnowskie Góry andRybnik. Other engines are deployed at the stations ofŁódź,Nowy Sącz,Poznań,Szczecin andWrocław.[2]
SM31 is aCo-Co locomotive, what means it runs on twobogies, each equipped with threeaxles. Bogies are similar in construction to those used inSU45 andSU46 locomotives. This gives SM31 locomotive good performance on highland tracks.[2] Being a typical shunter, SM31 has a single crew compartment of the same height as the machine and electric compartments.[1]The engine (V8,compression-ignition) is in fact a developed version ofSM42 locomotive engine, with its total power increased by about 50%. The engine drives the main alternator, which powers six 196 kW (263 hp)traction motors.[1]
Trumna (En.:Coffin) – from locomotive's angular shape.[3]
