NZR K class (1932)

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 K class of 1877-78, the first American-built engines to arrive in New Zealand.

History

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 A^B 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 K^A and K^B 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 by reducing travel from the original 8 inches to  7 ¹⁄₄ inches, 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 K^A and K^B 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 K^A class.

As time went on members of the K class gained improvements and additions from the K^A 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. Some of the class were rebuilt with new frames in 1955-57 but most of the class were in storage by 1961 and the decision was made that year the class would receive no more A grade overhauls, other than K 911. 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 until 1975 when it was replaced by D^F 1301. It was then transported to the main MOTAT site and placed at the Rail Pavilion in the company of A^B 832, F 180 Meg Merrilies, J 1236, W^W 491, and diesel-electric locomotive D^A 1400. It has remained on display at MOTAT since then, initially in the open but later under a shelter roof.

Physically, K 900 retains its original boiler, tender and plate frame, the latter showing evidence of extensive welding repairs due to the weak nature of the original construction. It appears much as it was when withdrawn, with the recessed K-style headlight, but with a K^A style funnel and a cross-compound pump with twin air reservoirs mounted under the front compressor shields. There are plans to move the locomotive to the Westen Spring Railway for storage, but possibly also to restore the locomotive to working order.

NZR converted three locomotives - 911, 917, and 921 - in 1967 for use as stationary boilers at Hutt Workshops. They continued in this use until 1988 when the boiler house was removed and the hulks were auctioned off. Ian Welch of the Mainline Steam Heritage Trust purchased K 911, the most complete of the hulks, while Steam Incorporated purchased K 917, paired with the tender from K 928, as a potential spare boiler for K^A 945. No buyer was found for K 921, which had been paired with the tender from K^A 939, and it was later scrapped although the tender and inner firebox went to and other parts, including driving wheels, were acquired by Steam Inc.

It was announced in 2013 that K 911 will be the next major restoration project at Mainline Steam's Wellington depot at Plimmerton. K 911 retained its cylinders, and was noted shortly after purchase in 1998 at their temporary Gracefield depot as having been stripped down for overhaul. This was put on hold prior to the move to Plimmerton, at which point the boiler was lowered back onto the overhauled frames for storage. Some of its parts were borrowed for use on K^A 942, then under restoration at the Glenbrook Vintage Railway in South Auckland.

K 917 has been stored at Steam Incorporated's Paekakariki depot since its arrival in 2001. It is heavily stripped and comprises the driving wheels, replacement 'heavy' frame from the 1950s, boiler and smoke box, and the tender from K 928. There are no current plans to restore this locomotive to working order.

Class register

Resource

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

References

External links

• New Zealand Steam Locomotives - Class K