NZR K class (1932)

NZR K class (1932)
NZR K class (1932)
K900 on static display at MOTAT. Photo: Hayden Booth
Power type Steam
Builder NZR Hutt Workshops
Build date 1932 - 1936
Configuration 4-8-4
Gauge 3 ft 6 in (1,067 mm) Cape gauge
Driver diameter 54 inches (1.37 m)
Wheelbase 61 ft 10.5 in (18.9 m)
Length 69 ft 8 in (21.2 m)
Width 8 ft 6 in (2.6 m)
Height 11 ft 6 in (3.5 m)
Weight on drivers 54.25 long tons (55.12 t)
Locomotive weight 85.6 long tons (87.0 t)
Tender weight 50.0 long tons (50.8 t)
Locomotive & tender
combined weight
135.6 long tons (137.8 t)
Fuel type Coal (original)
Oil (converted 1947 - 1953)
Fuel capacity 7.75 long tons (7.87 t) coal
1,570 imp gal (7,100 L) oil
Water capacity 5,000 imp gal (23,000 L)
Boiler pressure 200 psi (1,400 kPa)
Firegrate area 47.7 square feet (4.4 m2)
Heating surface:
1,933 square feet (179.6 m2)
Superheater area 485 square feet (45.1 m2)
Cylinders Two
Cylinder size 20 × 26 in (51 × 66 cm)
Tractive effort 30,815 pounds-force (137.1 kN)
Number in class 30
Number 900 - 929
First run 1932
Preserved 3
Disposition Withdrawn, 3 preserved

The NZR K class of 1932 was a class of mixed traffic 4-8-4 steam locomotives that operated on New Zealand's railway network. The locomotives were developed following the failure of the G class Garratts. The class should not be confused with the much earlier Rogers K class of 1877-78.



The three G class locomotives were introduced by the New Zealand Railways Department (NZR) in response to increased tonnages, especially on the mountainous, demanding North Island Main Trunk Railway. However, various faults led to their swift withdrawal from service and NZR still needed a large and powerful type of locomotive. It decided to develop a conventional rather than articulated locomotive, to avoid a repeat of the G class failure.

Initially conceived as a 4-8-2 locomotive, the K class was to be at least 50% more powerful than the AB class, and due to New Zealand's narrow gauge track and limited loading gauge, the power had to be very carefully compressed into an area smaller than would usually be used for such a locomotive.

Constructed at Hutt Workshops, the class utilised plate frames, partial mechanical lubrication, Franklin butterfly firehole doors, and roller bearings on all but the trailing bogie. The class had a distinctive appearance when first outshopped, with a pressed smokebox front and the headlight jutting out forward of the top of the smokebox. This latter feature was soon changed at the insistence of one of the Railway’s Board of Management – instead it was sunken flush into the smokebox, which required some modification and changed the aesthetic look of the class quite markedly.

K 919 was given an ACFI feedwater heater system as a trial, a feature that was continued on the subsequent KA and KB classes.

In service

Upon entering service the class were used on heavy freight and express passenger trains. The K class were best known for spectacular running on the mountainous parts of the North Island Main Trunk in the central North Island and on the Marton - New Plymouth Line around Wanganui. In particular they took over from the X class locomotives which had been used particularly on the Raurimu Spiral.

While generally reliable, trouble at first was encountered with the long-travel Walschaerts valve gear, and with the plate frames. While the valve gear problems were largely solved, the plate frames continued to crack especially in the region of the firebox. While many repairs were undertaken to fix the frames, this problem was only solved by replacing the frame with the new design constructed for the KA and KB classes. This was only done as the replacement was required; as a result not all of the class received the new frames.

After the Second World War, a coal shortage occurred and NZR converted a large number of locomotives to oil burning. The K class were a prime candidate due to the large size of the grate. The conversion process was concurrent with that of the KA class.

As time went on members of the K class gained improvements and additions from the KA class, and some locomotives had the Westinghouse cross-compound pump added in place of the original twin single-phase pumps.

Withdrawal and disposal

In 1954, main line dieselisation began and progressively displaced the K class, especially as the DA class was introduced from 1955. Withdrawal began in 1964, and all members exited service by 1967. Three of the class were retained by Hutt Workshops for use as stationary boilers, replacing three Garratt boilers from the G class. These 3 heavily stripped members lasted in such use service until 1988 when they were auctioned off.

Preserved locomotives

K 900 was donated to MOTAT, and prior to being delivered to the MOTAT site, it was put on display outside Sims Pacific Metals. Since that time it has sat on display at MOTAT, and only recently a shelter to protect it was erected. It appears much as it was when withdrawn, with the recessed K-style headlight, but with a KA style funnel and a cross-compound pump.

The three locomotives retained by Hutt Workshop were Ks 911, 917, and 921. When they were auctioned in 1988, K 911 was bought by Ian Welch for Mainline Steam, K 917 was bought by Steam Incorporated, and K 921 was scrapped with some parts retained for use by the other two.

List of locomotives

Key: In Service Leased to ARTA Withdrawn Preserved Under Repair Scrapped
Number Builder Entered service [1] Withdrawn [1] Notes
900 NZR Hutt Preserved MOTAT. On static display, retains original frame.
901 NZR Hutt
902 NZR Hutt
903 NZR Hutt
904 NZR Hutt
905 NZR Hutt
906 NZR Hutt
907 NZR Hutt
908 NZR Hutt
909 NZR Hutt
910 NZR Hutt
911 NZR Hutt Purchased 1988 by Ian Welch for Mainline Steam. Under restoration.
912 NZR Hutt
913 NZR Hutt
914 NZR Hutt
915 NZR Hutt
916 NZR Hutt
917 NZR Hutt Purchased by Steam Incorporated, 1988. Boiler designated as spare for KA 945. Currently stored.
918 NZR Hutt
919 NZR Hutt Fitted with ACFI feedwater equipment.
920 NZR Hutt
921 NZR Hutt Scrapped 1988, parts divided between Steam Incorporated and Mainline Steam
922 NZR Hutt
923 NZR Hutt
924 NZR Hutt
925 NZR Hutt
926 NZR Hutt
927 NZR Hutt
928 NZR Hutt
929 NZR Hutt


  • Heath, Eric, and Stott, Bob; Classic Steam Locomotives Of New Zealand, Grantham House, 1993
  • Stott, Bod; A Locomotive reborn: the Ka 945 story, Southern Press, 1986


External links

Wikimedia Foundation. 2010.

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