NZR X class

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NZR X class
Type and origin
Power typeSteam
BuilderNZR Addington Workshops
Build date1908 - 1909, 1913 - 1915
1943 - 1949 (rebuild)
 • Whyte4-8-2
Gauge3 ft 6 in (1,067 mm)
Driver dia.45 in (1.143 m)
Length56 ft 9.75 in (17.32 m)
Adhesive weight46.7 long tons (47.4 t; 52.3 short tons) (original)
45.6 long tons (46.3 t; 51.1 short tons) (rebuild)
Loco weight66.7 long tons (67.8 t; 74.7 short tons) (original)
66.6 long tons (67.7 t; 74.6 short tons) (rebuild)
Tender weight27.3 long tons (27.7 t; 30.6 short tons) (original)
28.55 long tons (29.01 t; 31.98 short tons) (rebuild)
Total weight94.0 long tons (95.5 t; 105.3 short tons) (original)
95.15 long tons (96.68 t; 106.57 short tons) (rebuild)
Fuel typeCoal
Fuel capacity4.0 long tons (4.1 t; 4.5 short tons) (original)
5.0 long tons (5.1 t; 5.6 short tons) (rebuild)
Water cap2,200 imp gal (10,000 L; 2,600 US gal)
 • Firegrate area
37.1 square feet (3.4 m2) (original)
37.5 square feet (3.5 m2) (rebuild)
Boiler pressure230 psi (1,586 kPa) (original)
215 psi (1,482 kPa) (rebuild)
Heating surface2,066 sq ft (191.9 m2) (original)
1,185 sq ft (110.1 m2) (rebuild)
 • Heating areaNone (original)
168 square feet (15.6 m2) (rebuild)
Cylinders2 high pressure + 2 low pressure (original)
4 high pressure (rebuild)
High-pressure cylinder13.5 in × 22 in (343 mm × 559 mm)
Low-pressure cylinder22 in × 22 in (559 mm × 559 mm)
Performance figures
Maximum speed30 mph (48 km/h)
Tractive effort26,620 lbf (118.4 kN) (original)/ 31,150 lbf (138.6 kN) (starting)
29,500 lbf (131 kN) (rebuild)
Number in class18
LocaleNorth Island Main Trunk
First run1909
Last run1957
Current ownerFeilding & Districts Steam Rail Society (1)
DispositionWithdrawn, one preserved

The NZR X class was a pioneering class of eighteen 4-8-2 steam locomotives designed by A. L. Beattie that operated on the national rail network of New Zealand. In 1908, a heavy and powerful locomotive was required to haul traffic on the newly completed mountainous central section of the North Island Main Trunk Railway, and as a logical progression of the 4-6-2 Q class design, the 4-8-2 wheel arrangement was created for the X class.


When the first X was completed in 1908 at NZGR's Addington Workshops in Christchurch, it was the very first 4-8-2 locomotive built in the world. The 4-8-2 design went on to be popular in the United States and was nicknamed the "Mountain" type; one theory suggests this name stems from the mountainous terrain that inspired the X's design, while another suggests the Chesapeake and Ohio Railway first coined the name in reference to its 4-8-2s of 1911 that were built to operate in the Allegheny Mountains.

The X class initially operated as the freight counterpart of the passenger A class, but they struggled to operate at speeds higher than 50 km/h (30 mph). They were built as de Glehn compound locomotives, but during the 1940s, most of the class were converted to simple, superheated locomotives. This increased their power but did not prolong their lives and most were officially withdrawn from service on 2 March 1957, though a few had been taken out of service earlier and two were sold to the Ohai Railway Board (ORB) that operated a private industrial line at the end of the Wairio Branch.

Class register[edit]

Key: In service On lease Out of service Preserved Overhaul or repair Scrapped
Number Builder Entered service Withdrawn Notes
439 NZR Addington 9-1-1909 2-3-1957 Converted to 4-cylinder simple, 6-1949
440 NZR Addington 25-3-1909 2-3-1957 Converted to 4-cylinder simple, 7-1948
441 NZR Addington 10-5-1909 2-3-1957
442 NZR Addington 10-7-1909 4-3-1944 Converted to 4-cylinder simple, 6-1943. In Use Ohai Railway Board 1944-1968. Preserved at Feilding and District Steam Rail Society
443 NZR Addington 1-12-1909 2-3-1957 Converted to 4-cylinder simple, 7-1947
444 NZR Addington 3-2-1910 2-3-1957 Converted to 4-cylinder simple, 12-1949
445 NZR Addington 24-5-1910 26-5-1949
446 NZR Addington 30-4-1910 6-12-1946 Converted to 4-cylinder simple, 12-1946. In Use Ohai Railway Board 1946-1959.
588 NZR Addington 14-10-1913 2-3-1957 Converted to 4-cylinder simple, 5-1951
589 NZR Addington 11-11-1949 6-1949
590 NZR Addington 27-1-1914 2-3-1957
591 NZR Addington 17-3-1914 2-3-1957 Converted to 4-cylinder simple, 12-1950
592 NZR Addington 22-6-1914 2-3-1957 Converted to 4-cylinder simple, 10-1950
593 NZR Addington 3-9-1914 2-3-1957 Converted to 4-cylinder simple, 6-1950
594 NZR Addington 31-10-1914 2-3-1957 Converted to 4-cylinder simple, 5-1945
595 NZR Addington 3-12-1914 2-3-1957
596 NZR Addington 26-1-1915 2-3-1957 Converted to 4-cylinder simple, 12-1949
597 NZR Addington 1-4-1915 2-3-1957


The ORB locomotive, X 442, survived and has passed into the hands of railway preservation enthusiasts. It is currently located at the depot of the Feilding and District Steam Rail Society. Two X class boilers are held by Mainline Steam.


  • Heath, Eric, and Stott, Bob; Classic Steam Locomotives Of New Zealand, Grantham House, 1993

External links[edit]