NZR K class (1932)

NZR K class (1932)

K 900 on static display at MOTAT, Auckland.

Type and origin Power type Steam Builder NZR Hutt Workshops Build date 1932 - 1936

Specifications Configuration 4-8-4 Gauge 3 ft 6 in (1,067 mm) Driver dia. 54 inches (1.372 m) Wheelbase 61 ft 10.5 in (18.86 m) Length 69 ft 8 in (21.23 m) Width 8 ft 6 in (2.59 m) Height 11 ft 6 in (3.51 m) Adhesive weight 54.25 long tons (55.12 t; 60.76 short tons) Loco weight 85.6 long tons (87.0 t; 95.9 short tons) Tender weight 50.0 long tons (50.8 t; 56.0 short tons) Total weight 135.6 long tons (137.8 t; 151.9 short tons) Fuel type Coal (original) Oil (converted 1947 - 1953) Fuel capacity 7.75 long tons (7.87 t; 8.68 short tons) coal 1,570 imp gal (7,100 L; 1,890 US gal) oil Water cap 5,000 imp gal (23,000 L; 6,000 US gal) Firebox:  • Firegrate area 47.7 sq ft (4.4 m2) Boiler pressure 200 psi (1,379 kPa) Heating surface 1,933 sq ft (179.6 m2) Superheater: ​  • Heating area 485 sq ft (45.1 m2) Cylinders Two Cylinder size 20 in × 26 in (508 mm × 660 mm)

Performance figures Tractive effort 30,815 lbf (137.1 kN)

Career Number in class 30 Numbers 900 - 929 First run 1932 Preserved 3 Disposition Withdrawn, 3 preserved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 K class of 1877-78, the first American-built engines to arrive in New Zealand.

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.