| Driving Wheels | 4ft 6ins |
| Weight | 109 tons |
| Boiler Pressure | 200psi |
| Cylinders | Outside – 18in x 26in |
| Tractive Effort | 24,960 lbf |
40 locomotives were built in 1939 by the North British Locomotive Company and became the J class. They were built by the North British Locomotive Company as the NZR workshops were already fully employed.
They were designed to provide a mixed traffic locomotive that was more powerful than the Ab class that was capable of running on the lighter secondary lines of the New Zealand Railways (NZR) network. They also had to be equally capable of running express passenger trains on main routes.
The J class incorporated roller bearing axles, hydrostatic lubrication and twin Westinghouse brake pumps.
They had bar frames instead of plate frames and were equipped with Baker Valve-gear. The locomotives were attached to Vanderbilt tenders and were outshopped with distinctive bullet-nosed streamlining.
The first 30 of the class in service 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 the Second Word War. 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 wartime 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 Ja class in its Hillside workshops from 1946.
This locomotive (J 1234) ran on the NZR from 1939 until 1971 after which it was stored at Dunedin until 1974.
In 1972 the locomotive was purchased by Steam Incorporated and transferred to their base at Paekakariki in 1974. It remained in a serviceable condition until 1992 when it was certified to run on the mainline network.
In 1998 the locomotive was leased to the Glenbrook Vintage Railway who used it until 2003 after which it was placed in store awaiting its return to Paekakariki.
The locomotive eventually returned to Paekakariki in 2016 where it was placed in store awaiting overhaul.
There are two other preserved J class locomotives built by the North British Locomotive Company.
• Works number 24534 – J 1211 Gloria
• Works number 24559 – J1236 Joanne
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Preserved British Steam Locomotives 