NZR J class (1939)

NZR J class
J 1211 being serviced before departure from Napier. Photo by Joseph Christianson
Type and origin Power type Steam Builder North British Locomotive Works, Glasgow, Scotland Build date 1939
Specifications Configuration: ​  • Whyte 4-8-2 Gauge 3 ft 6 in (1,067 mm) Wheel diameter 54 in (1.372 m) Wheelbase 34 ft 10 in (10.62 m) Length 66 ft 11 in (20.40 m) Adhesive weight 44.45 long tons (45.16 t; 49.78 short tons) Loco weight 68.55 long tons (69.65 t; 76.78 short tons) Tender weight 40.35 long tons (41.00 t; 45.19 short tons) Total weight 108.9 long tons (110.6 t; 122.0 short tons) Fuel type Coal Fuel capacity 6.0 long tons (6.1 t; 6.7 short tons) Water cap 4,000 imp gal (18,000 L; 4,800 US gal) Firebox:  • Firegrate area 39.0 square feet (3.6 m2) Boiler pressure 200 psi (1,400 kPa) Feedwater heater ACFI Heating surface 1,469 square feet (136.5 m2) Superheater: ​  • Heating area 283 square feet (26.3 m2) Cylinders 2 Cylinder size 18 in × 26 in (457 mm × 660 mm) Valve gear Baker
Performance figures Tractive effort 24,960 lbf (111.0 kN)
Career Number in class 40 Numbers 1200 - 1239 Locale All of New Zealand First run 1939 - 1940 Last run 1964 - 1967 Retired 1964 - 1971 Scrapped 1969 - 1971 Current owner Ian Welch, Steam Incorporated Disposition Three preserved, twelve rebuilt as JB, remainder scrapped

The NZR J class steam locomotives were a type of 4-8-2 steam locomotive used on the New Zealand Railway network. Built by the North British Locomotive Works, although designed to work on the lighter secondary lines the class was frequently used on main line express passenger trains as well as freight. The class first appeared in distinctive streamlining, which was later removed for maintenance reasons. The class should not be confused with the earlier 1874 J class. Three J's lasted until the end of steam on 26th October 1971.

The J Class were primarily designed to provide a mixed traffic locomotive more powerful than the Ab Class that was capable of running on the lighter secondary lines of the New Zealand Railways network, but was equally capable of running express passenger trains on the Main Trunk routes which were being operated by the larger K Class locomotives and the in-production K^A class & K^B classes. As the NZR workshops were already busy with the production of the K^A's & K^B's, the North British Locomotive Company were engaged to build the class of 40 locomotives. The J class incorporated a number of similar features with the contemporaneous K^A & K^B classes, such as roller bearing axles, hydrostatic lubrication and twin Westinghouse brake pumps; however they used bar frames instead of plate frames, and were equipped with Baker Valve gear instead of Walschaerts. They also featured a Vanderbilt tender, and were outshopped with distinctive bullet-nosed streamlining which bears similarity to the Norfolk and Western Railway class J (1941) and the later NSWGR 38 class.

The first 30 of the class were allocated to the North Island, with the last 10 allocated to the South Island for use on the hilly section between Dunedin and Oamaru. They were immediately placed into service on the main trunk routes in both islands in order to help move wartime traffic during World War II. Although used on freight trains as well, the class was well suited to high-speed running on the passenger trains of the era. Due to the war time conditions, the streamlining became burdensome for maintenance and the skyline casing, which was open at the top proved to be a trap for soot from the locomotive's exhaust. After a time, the skyline casing started to be removed from some examples of the class leaving them with just the bullet nose. The design was successful enough that NZR opted to build an improved variant called the J^A class in its Hillside workshops from 1946, and by 1950 enough J^A class had been introduced into service that the 10 South Island based J class locomotives were transferred to the North Island. From this time onwards the J class lost their streamlining, either all at once during overhaul or if the skyline casing had already been removed, then only the bullet nose with the headlight moved to the same position as adopted by the J^A class. Around this time also, some of the J class members had the twin Westinghouse pumps removed in favour of the Cross-compound pump used by the J^A class - but not all J class engines were fitted with this.