NZR Ja class

NZR J^A class

JA 1271 with excursion consist climbing the Opapa incline

Type and origin Power type Steam Builder NZR Hillside Workshops, Dunedin (35) North British Locomotive Works, Glasgow, Scotland (16) Build date 1946–1956

Specifications Configuration 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 11.5 in (20.41 m) Adhesive weight 44.45 long tons (45.16 t; 49.78 short tons) Loco weight 69.1 long tons (70.2 t; 77.4 short tons) Tender weight 40.35 long tons (41.00 t; 45.19 short tons) Total weight 109.45 long tons (111.21 t; 122.58 short tons) Fuel type Coal (Hillside) Oil (North British) Fuel capacity 6.0 long tons (6.1 t; 6.7 short tons) coal 1,350 imp gal (6,100 L; 1,620 US gal) oil 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 None: Fitted with Davies & Metcalfe Exhaust Injector Heating surface 1,469 square feet (136.5 m2) Superheater: ​  • Heating area 283 square feet (26.3 m2) Cylinders Two Cylinder size 18 in × 26 in (457 mm × 660 mm)

Performance figures Maximum speed 70 mph (110 km/h) Tractive effort 24,960 lbf (111.0 kN)

Career Number in class 51 Numbers 1240 – 1274 (Hillside) 1275 – 1290 (North British) Locale All of New Zealand First run 1947 – 1956 (Hillside) 1952 (North British) Last run 16 November 1971 Retired 1967–1971 Scrapped 1969–1972 Disposition 7 preserved, 44 scrapped

The NZR J^A class were a type of 4-8-2 steam locomotive used on the New Zealand railway network. The class was built in two batches, with the second batch possessing some differences from the first. The first batch was built at Hillside Workshops in 1946–56 and the second batch by the North British Locomotive Works in 1951. To distinguish between the batches, locomotives are identified by their maker.

The J^A class was the last class of steam locomotive built both for and by NZR – Hillside J^A 1274 was the last steam locomotive ever built by NZR, and the North British J^As were the last steam locomotives built overseas for the NZR.

The class had relatively short lives of between 12 and 24 years, as they succumbed to dieselisation. Nine J^As lasted until the end of steam on 26 October 1971.

The class were an improved version of the J class locomotives. Unlike the J class, which were built overseas by the North British Locomotive Company in Glasgow, Scotland, the new class were instead constructed by NZR's Hillside Workshops in Dunedin. However, much of the components, such as the bar frames, were still sourced from North British as Hillside lacked the means to construct such a frame.

Some of the more notable improvements from the J class were the use of the Westinghouse cross-compound pump; Ashton double pressure gauge; the Sellars injector in the cab; steam for the pump was taken from a manifold in the cab and not an outlet on the steam dome; combined gauges in the cab; and roller bearings on the driving and connecting rods. However, the first two J^As produced, No.'s 1242 and 1243, did not have roller bearings on any of the rods, and on the rest of the locomotives numbered in the 124X range, roller bearings were only present at the connection between the driving and connecting rods and not on the other wheels. The "all rolling bearing JA... 1265 to 1270" were assigned by Linwood locomotive depot to the South Island Limited wherever possible between 1952 and 1968, the fastest being 'legendary' JA 1270, scrapped in mid 1969, requiring only minimal repair after running into an unaligned turntable pit. In most other respects however, the class was virtually identical to the earlier J class, although the J^A class was never fitted with bullet-nose streamlining.