The reference for locomotives and railcars


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New Zealand Railways classes J, JA and JB
New Zealand | 1939 | 91 produced
Historical Railway Images / flickr

The NZR class J of 1939 was designed to pull both express and freight trains on branch lines, but also be fast enough for use on main lines. They had a 4-8-2 wheel arrangement and were built with partial streamlining, which was later removed. The JB class was created by converting twelve class J locomotives to burn oil.

After 40 class J locomotives that were built at North British in 1939, 51 of the improved class JA were built between 1946 and 1956. These had no streamlining and were partly built in the NZR Hillside works. The 16 locomotives built in Scotland had oil firing. The intended area of operation now only included express trains.

J<sup>A</sup> 1271 in September 2012 while crossing the Otaki River
JA 1271 in September 2012 while crossing the Otaki River

The JA was the last class of steam locomotives that the NZR purchased. Diesel railcars and locomotives had already being introduced at the time the last ones were delivered. Although they were too large for some branch lines, they could also hold their own against heavier locomotives on main lines. Although the speed limit for express trains in New Zealand was 55 mph (89 km/h), they are said to have regularly reached well over 70 mph (113 km/h). Many survived until the end of the steam age on the NZR in 1971. Today ten remain, several of which are operational.

ManufacturerNorth BritishNorth British, Hillside
Axle config4-8-2 (Mountain) 
Gauge3 ft 6 in (Cape gauge)
Dimensions and Weights
Length66 ft 11 in
Wheelbase34 ft 10 in
Fixed wheelbase14 ft 3 in
Service weight153,552 lbs154,784 lbs
Adhesive weight99,567 lbs
Total weight243,937 lbs244,159 lbs
Axle load25,761 lbs
Water capacity4,804 us gal
Fuel capacity13,440 lbs (coal)
Power sourcesteam
Estimated power1,100 hp (820 kW)
Optimal speed26 mph
Starting effort26,520 lbf
Power Plant
Driver diameter54 in
Boiler pressure200 psi
Expansion typesimple
Cylinderstwo, 18 x 26 in
Grate area39 sq ft
Evaporative heating area1,469.5 sq ft
Superheater area283 sq ft
Total heating area1,752.5 sq ft
Calculated Values
steam locomotive
secondary line
last changed: 12/2023

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