| NZR AB class | |
|---|---|
| Preserved AB 778 hauling the Kingston Flyer | |
| Power type | Steam |
| Builder | NZGR Addington Workshops (38) North British Locomotive Company (83) A & G Price Limited, Thames (20) |
| Build date | 1915–1918, 1921–1927 |
| Total produced | 141 |
| Configuration | 4-6-2 |
| Gauge | 3 ft 6 in (1,067 mm) Cape gauge |
| Driver diameter | 54 in (1.372 m) |
| Wheelbase | 52 ft 6 in (16.00 m) |
| Length | 62 ft 5 in (19.02 m) |
| Locomotive weight | 51.3 long tons (52.1 tonnes) |
| Tender weight | 33.4 long tons (33.9 tonnes) |
| Locomotive & tender combined weight |
84.7 long tons (86.1 tonnes) |
| Fuel type | Coal |
| Fuel capacity | 4.0 long tons (4.1 tonnes) |
| Water capacity | 3,500 imp gal (16,000 l; 4,200 US gal) |
| Boiler pressure | 180 lbf/in² (1.24 MPa) |
| Firegrate area | 33 sq ft (3.1 m2) |
| Heating surface: Total |
1,148 sq ft (106.7 m2) |
| Superheater area | 204 sq ft (19.0 m2) |
| Cylinders | Two, outside |
| Cylinder size | 17 × 26 in (432 × 660 mm) |
| Top speed | 60 mph (97 km/h) |
| Tractive effort | 20,030 lbf (89.10 kN) |
| Career | NZR |
| Number | 608–838 |
| Locale | All of New Zealand |
| First run | October 1915 |
| Withdrawn | 1963–1969 |
| Preserved | 7 (608, 663, 699, 745, 778, 795, 832) |
| Current owner | Kingston Flyer, Mainline Steam, Pleasant Point Museum and Railway. |
| Disposition | Withdrawn, Preserved |
The NZR AB class was a class of 4-6-2 Pacific tender steam locomotive that operated on New Zealand's national railway system. Originally an improvement on the 1906 A class, 141 were built between 1915 and 1927 by NZR's Addington Workshops, A & G Price Limited 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 ten were rebuilt from the tank version of the AB – the WAB class – between 1947 and 1957, while another two North British-made locomotives were built, but were lost in the wreck of the SS Wiltshire in May 1922.
Reputedly the first engine able to generate one horsepower for every 100 pounds of weight, the AB class was efficient and versatile, and the engines were easy to maintain and operate. Members of the class worked almost every part of the New Zealand rail network, and were used for both freight and passenger trains. The AB class was easily able to pull an express passenger train at speeds of 100 km/h (62 mph), or haul 700-tonne goods trains on easy grades. They, along with the earlier 'F' class, were known as the 'Maids of all work'.
A distinctive feature of the AB class's design is their Vandebuilt tenders, which gave them their cylindrical back. Several features of the class, notably their boilers, were used on other NZR locomotives.
The AB class were superseded on principal express trains and heavy freight trains by the K class of 1932 and the J class of 1939, and were relegated to secondary duties. However they were still to be seen running relief expresses during the busier parts of the year. The majority of the class was withdrawn from NZR services during the 1960s, as diesel traction replaced steam, with a few members of the class lasting to the end of steam itself in 1971. Two were retained to operate the Kingston Flyer, possibly New Zealand's most famous heritage railway. The Flyer has now passed into private ownership and it is still run by AB 778 and AB 795. Five more have been preserved by various other preservation societies.
The WAB class of 1917 was essentially a tank locomotive version of the AB class.
Contents |
Seven members of the AB class have been preserved.
| Key: | In service | Out of service | Auckland Transport service | Preserved | Overhaul | Scrapped |
|---|
| Number | Builder | Introduced | Withdrawn[n 1] | Current status | Notes |
|---|---|---|---|---|---|
| 608 | NZR Addington | October 1915 | October 1967 | Undergoing restoration | NZRLS on lease to Steam Incorporated, Paekakariki. |
| 663 | NZR Addington | December 1917 | July 1969 | Operational and mainline certified | Preserved, Mainline Steam, Plimmerton. |
| 699 | A & G Price | August 1922 | March 1968 | Operational | Preserved, Pleasant Point Museum and Railway. |
| 745 | North British Loco. | July 1922 | January 1957 | Awaiting restoration | Preserved, Taranaki Steam Locomotive Trust (Taranaki Flyer Society). |
| 778 | NZR Addington | September 1925 | July 1969 | Operational | Preserved, Kingston Flyer. |
| 795 | NZR Hillside | May 1927 | July 1969 | Operational | Preserved, Kingston Flyer. Originally built as a Wab class locomotive. |
| 832 | North British Loco. | July 1925 | December 1967 | Awaiting restoration | MOTAT on lease to Glenbrook Vintage Railway, Auckland. |