NSB Class 91

NSB Class 86
A heritage Class 86 on the Solør Line
In service	1938–96
Manufacturer	Strømmen
Constructed	1938–54 (Class 86) 1954–56 (Class 91)
Number built	38 (Class 86) 10 (Class 91)
Capacity	48–70
Operator(s)	Norwegian State Railways
Specifications
Car length	21,500 mm (70 ft 6 in)
Maximum speed	100 km/h (62 mph)
Weight	30.5 t (30.0 long tons; 33.6 short tons)
Prime mover(s)	2 × Rolls-Royce C6SFLH
Power output	312 kW (418 hp)
Track gauge	1,435 mm (4 ft 8 1⁄2 in)

NSB Class 86 (Norwegian: NSB type 86) is a class of diesel-hydraulic multiple units built by Strømmens Værksted for the Norwegian State Railways (NSB). Thirty-eight motor cars and thirty-one trailers were built between 1937 and 1954, split between six subtypes designated a through f. Class 91 was a further delivery of ten units that had a more comfortable interior and designed for regional trains. The trains had good accelearation and a maximum speed of 100 kilometres per hour (62 mph), which made them suitable for most unelectrified lines in Norway. As most of the network gradually became electrified, the class became increasingly used on branch lines.

The oldest units were originally equipped with MAN and DWK prime movers. Later models received prime moves from Hercules. From the 1960s, all trains not retired received two Rolls-Royce C6SFLH engines with a power output of 158 kilowatts (212 hp) each. The class was taken out of regular service in 1994 and retired in 1996. Thirteen motor units and nine trailers have been preserved by various heritage railways and museums in Norway and Denmark.

The oldest units were equipped with Maschinenfabrik Augsburg-Nürnberg (MAN) and DWK prime movers. The DWK engines in the a and c-series had a power output of 138 kilowatts (185 hp) each. The MAN engine in the b-series had a power output of 110 kilowatts (150 hp) each, while the d-series with DWK engines had a power output of 150 horsepower (110 kW) each. Later editions were originally equipped with two Hercules DFXH-F prime movers, each with a power output of 140 kilowatts (190 hp). The class was later retrofitted with two Rolls-Royce C6SFLH with a power output of 158 kilowatts (212 hp). The class had a diesel-hydraulic transmission, with fluid converters originally from Atlas. They had a weight of 30.5 tonnes (30.0 long tons; 33.6 short tons) and a maximum speed of 100 kilometres per hour (62 mph).