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Norwegian State Railways type 31
Norway | 1915
27 produced
Type 31a No. 285 shortly after its withdrawal at Oslo
Type 31a No. 285 shortly after its withdrawal at Oslo
Ses

When the Bergen Railway was converted for higher axle loads, more powerful locomotives than the type 26 could be used there. This resulted in the type 31 with the same axle arrangement, but with a higher weight and boiler pressure. In 1915, two locomotives were initially built which, like the types 26a and 26b, had a four-cylinder engine with simple expansion.

Locomotive Magazine, August 1917

The high tractive power that could be achieved for a short period of time by this engine was used to push snow blowers on the Bergen Railway. In 1920, two more identical locomotives followed for the same purpose, which were also supplied by Thunes from Oslo and were designated together with the first two as type 31a.

Sectional drawing
Sectional drawing
Locomotive Magazine, August 1917

As with its predecessor, the majority of locomotives were built with compound engines in order to be able to maintain a similarly high tractive effort over a longer period of time. These locomotives, which were designated as Type 31b, were supplied by various manufacturers between 1923 and 1926 and took over the tasks of the type 26. They thus pulled different train types on the Bergen Railway until the Nohab diesel locomotives of the Di 3 type were introduced there in 1957 and 1958.

They were now distributed to other locations where there was no electrification or where diesel locomotives were not yet available. They spent their final years on branch lines that could withstand the weight of these locos. Only the four type 31a locomotives remained in service until the end of their lives in their traditional role as pusher locomotives for the snow blowers and were not put out of service until 1970.

Variant31a31b
General
Built1915-1926
ManufacturerThunes, NoHAB, Norsk Maskin Industri, Breda, Hamar Jernstøberi
Axle config4-8-0 (Twelve-wheeler) 
Gauge4 ft 8 1/2 in (Standard gauge)
Dimensions and Weights
Length58 ft 1 5/8 in61 ft 2 5/8 in
Wheelbase27 ft 8 11/16 in27 ft 9 7/8 in
Rigid wheelbase16 ft 4 7/8 in16 ft 6 1/16 in
Total wheelbase49 ft 8 7/16 in51 ft 7 5/16 in
Empty weight147,269 lbs156,748 lbs
Service weight165,346 lbs176,370 lbs
Adhesive weight123,238 lbs126,986 lbs
Total weight260,586 lbs271,609 lbs
Axle load30,865 lbs31,967 lbs
Water capacity5,283 us gal
Fuel capacity11,023 lbs (coal)
Boiler
Grate area32.3 sq ft
Firebox area128.1 sq ft
Tube heating area2,149.6 sq ft
Evaporative heating area2,277.6 sq ft
Total heating area2,277.6 sq ft
Variant31a31b
Power Plant
Driver diameter53.1 in
Boiler pressure174 psi186 psi
Expansion typesimplecompound
Cylindersfour, 16 1/8 x 23 5/8 infour, HP: 16 9/16 x 23 5/8 in
and LP: 24 13/16 x 23 5/8 in
Power
Power sourcesteam
Estimated power939 hp (700 kW)1,006 hp (750 kW)
Optimal speed17 mph24 mph
Top speed43 mph
Starting effort34,281 lbf26,563 lbf
with start valve31,876 lbf
Calculated Values
steam locomotive
express
passenger
freight
Von Borries compound
last changed: 02/2022
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