| NZR AB class |
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| Specifications |
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Configuration:
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| • Whyte | 4-6-2 |
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| Gauge | 3 ft 6 in (1,067 mm) |
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| Driver dia. | 54 in (1.372 m) |
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| Wheelbase | 52 ft 6 in (16.00 m) |
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| Length | 62 ft 5 in (19.02 m) |
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| Loco weight | 51.3 long tons (52.1 tonnes; 57.5 short tons) |
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| Tender weight | 33.4 long tons (33.9 tonnes; 37.4 short tons) |
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| Total weight | 84.7 long tons (86.1 tonnes; 94.9 short tons) |
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| Fuel type | Coal |
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| Fuel capacity | 4.0 long tons (4.1 tonnes; 4.5 short tons) |
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| Water cap. | 3,500 imp gal (16,000 L; 4,200 US gal) |
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| Firebox: | |
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| • Grate area | 33 sq ft (3.1 m2) |
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| Boiler pressure | 180 lbf/in2 (1.24 MPa) |
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| Heating surface | 1,148 sq ft (106.7 m2) |
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Superheater:
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| • Heating area | 204 sq ft (19.0 m2) |
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| Cylinders | Two, outside |
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| Cylinder size | 17 in × 26 in (432 mm × 660 mm) |
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| Performance figures |
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| Maximum speed | 60 mph (97 km/h) |
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| Tractive effort | 20,030 lbf (89.10 kN) |
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| Career |
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| Operators | NZR |
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| Numbers | 608–838 |
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| Locale | All of New Zealand |
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| First run | October 1915 |
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| Withdrawn | 1963–1969 |
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| Preserved | 7 (608, 663, 699, 745, 778, 795, 832) |
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| Current owner | Kingston Flyer, Mainline Steam, Pleasant Point Museum and Railway, Museum of Transport and Technology, Ferrymead Railway, Rimutaka Incline Railway Heritage Trust. |
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| Disposition | Seven preserved, two lost in a shipwreck off Great Barrier Island in 1922, remainder scrapped. |
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The NZR AB class was a class of 4-6-2 Pacific tender steam locomotive that operated on New Zealand's national railway system for New Zealand Railways (NZR). Originally an improvement on the 1906 A class, 141 were built between 1915 and 1927 by NZR's Addington Workshops, A & G Price of Thames, New Zealand, and North British Locomotive Company, making the AB class the largest class of steam locomotives ever to run in New Zealand. An additional eleven were rebuilt from the tank version of the AB – the WAB class – between 1947 and 1957. Two North British-made locomotives were lost in the wreck of the SS Wiltshire in May 1922.
