SM83

SM53
SM53 in Holtegata on the Briskeby Line in 1971
Interior of an original trailer, with the conductor's seat to the left
In service	1952–2000
Manufacturer	Høka Hägglund
Family name	Mustang
Constructed	1952–58
Refurbishment	1985–91 (SM83)
Number built	58
Number scrapped	42
Fleet numbers	204–253
Capacity	116
Operator(s)	Oslo Sporveier
Line(s) served	Oslo Tramway
Specifications
Car body construction	Steel
Car length	14,700 mm (580 in)
Width	2,500 mm (98 in)
Doors	3
Maximum speed	60 km/h (37 mph)
Weight	16.9 t (16.6 long tons; 18.6 short tons)
Prime mover(s)	Hägglund MBL 10
Power output	180 kW (240 hp)
Electric system(s)	600 V DC overhead line
Track gauge	Standard gauge

SM53, originally designed MBO and colloquially known as Høka, were a class of 58 trams and 50 trailers built by Høka and Hägglund for Oslo Sporveier. Part of the Hägglund Mustang family, the units were used on the Norway's Oslo Tramway from 1952 until 2000. The 14.7-meter (48 ft) long and 2.5-meter (8 ft 2 in) wide trams weighed 16.9 tonnes (16.6 long tons; 18.6 short tons). They had four motors providing a combined power output of 180 kilowatts (240 hp), allowing for a top speed of 60 kilometers per hour (37 mph).

The first series of thirty trams in 1950, with delivery in 1952 and 1953. These were designated MBO50. The next order was for new bodies for used Class SS units. The eight motor units were designated MO and nicknamed Chickens, while the twelve trailers were designated TO. These twin-axle units proved unsuccessful and Oslo Sporveier therefore took deliver of more MBO units. The next batch of twelve MBO55 units were delivered in 1957 and the final batch of eight were designated MBO56 and delivered in 1958. These were built for use on the Lambertseter Line, but were found unsuitable for use on light rail service and later moved back to the streets. From 1985 to 1991 eleven units were rebuilt with new cabs, interior and fronts, and designated SM83. Retirement of the class started in 1980 with Chickens. The series were gradually replaced, with the last SM53 units being taken out of service in 1997. The last SM83 were taken out of use in 2000.

At the end of the Second World War Oslo Sporveier had a fleet of 331 trams, of which only the 46 Gullfisk trams were modern bogie-constructions. The remaining were twin-axle and limited in capacity. Oslo Sporveier needed more and newer matériel and considered several options. More Gullfisk were considered, but their aluminum bodies were found to be unsuitable, they had issues with cracks in the bogies and their electrical system was prone to faults. They were design with entrance through the middle door, which had during the high usage during the war proven to be inefficient and often led to two conductors being needed for each car. By then flow-through units with a stationary conductor had become common. There were also significant developments within controllers and 300-volt motors. As such additional orders for Gullfisk were discarded.