K Class Locomotive
From 1932 the New Zealand-designed and manufactured K class steam locomotive, with its derivatives the Ka and Kb classes, was the mainstay of New Zealand’s rail services until gradually superseded by diesel-electric locomotives, which were first introduced in 1955. Comparable in capacity with England’s LMS Railway class 8F goods engine, the last 71 K series locomotives were withdrawn in 1969.
Under the direction of the New Zealand Railways (NZR) Chief Mechanical Engineer P R Angus, the design team headed by R J Gard was required to produce a locomotive 50 per cent more powerful than prevailing NZR mainline mixed-traffic locomotives, that was able to work within limits far more stringent than almost any other railway had coped with at that time. A further design consideration was that the locomotives had to be produced in local railway workshops.
Building these large modern locomotives represented the highest achievement of mechanical engineering in New Zealand up to that time. The locomotives themselves enabled NZR to cope with increasing traffic, which reached a peak during World War Two.
The main design parameters were:
Tractive effort of around 30,000 pounds (lb)
Axle load not to be above 14 tons
Maximum height of 11 feet 6 inches
Maximum width of 8 feet 6 inches.
The resulting engine weighed 136 tons, had a tractive effort of 32,730 lb at 85 per cent of the boiler pressure, and an axle load right on the 14 ton limit. This achievement of a “quart in a pint pot” attracted considerable attention overseas. The design had been strongly influenced by contemporary South African practice. One of the notable features was the large grate, which at 47.7 square feet was described as almost the largest practicable for hand-firing by one man. Also notable was a booster engine under the cab of the six Kb class locomotives used in the South Island.
The first K, No. 900, is preserved on display at Auckland’s Museum of Transport and Technology (MOTAT). It was built at the NZR Woburn workshops, Lower Hutt, in 1932 and withdrawn from traffic in 1965.
The first Ka to enter service (No. 945) was also built at Woburn, in 1939, and withdrawn in 1967. It is preserved for working occasional excursion trains at Steam Incorporated’s museum at Paekakariki, near Wellington. Kb 968, the last of the series to run in revenue service, was built at the NZR Hillside workshops, Dunedin, in 1939 for South Island service and was withdrawn in 1969. It is being restored at Mainline Steam Trust, Sockburn, Christchurch, to work occasional excursion trains under lease from Ferrymead Railway, Christchurch.
IPENZ “Engineering to 1990” project
This item of New Zealand’s engineering heritage was recognised as part of the IPENZ “Engineering to 1990” project, which the Institution organised to help celebrate the country’s sesquicentenary in 1990.
K 900 is on display at Museum of Transport and Technology, Western Springs, Auckland.
Ka 945 is at Steam Incorporated, Paekakariki, where it is to be returned to service as resources permit.
Kb 968 is at Mainline Steam Trust, Sockburn, Christchurch, where it is to be restored to working condition.
At least three more engines exist:
K 917 is being restored at Plimmerton
Ka 935 is used intermittently at Silverstream, Hutt Valley
Ka 942 with air smoothed cowling, is in excursion train use based at Plimmerton.
Palmer, A N & Stewart, W W, Cavalcade of New Zealand Locomotives, Reed, 1965.
Lloyd, W G, Register of NZR Steam Locomotives, Otago Railway & Locomotive Society, Dunedin, 2002.
Additional image gallery details
K class steam locomotive, New Zealand Railways no 919, 4-8-4 type [circa 1935]. Godber, Albert Percy, 1875-1949: Collection of albums, prints and negatives. Ref: APG-0286-1/2-G. Alexander Turnbull Library, Wellington, New Zealand.
Ka class steam locomotive, New Zealand Railways no 946, 4-8-4 type [circa 1939]. Godber, Albert Percy, 1875-1949: Collection of albums, prints and negatives. Ref: APG-0284-1/2-G. Alexander Turnbull Library, Wellington, New Zealand.
Permission of the Alexander Turnbull Library, Wellington, New Zealand, must be obtained before any re-use of these images.