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K Class 4-8-4
CLASS  K    4-8-4

Introduced: 1932 Number in Class: 30

K Class Register

Locomotive Specifications

  NZR Hutt

Engine Weight:    
85.6 tons
Tender Weight:    50.0 tons Total Weight:    135.6 tons Adhesive Weight:    
54.25 tons
Length over Buffers:    
69' 8"
Total Wheelbase:    
61' 10"
Engine Wheelbase:    
34' 10"
Coupled Wheelbase:    
14' 3"
Tender Wheelbase:    
18' 2"
Driver Wheel Dia.:    54" Cylinders HP:    
Two - 20" x 26"
Cylinders LP:    
Grate Area:    47.7 sq ft Evaporative Area:    
1933 sq ft
Superheated Area:    
485 sq ft
Working Pressure:    
200 psig
Tractive Effort:    
30815 lbs f
Coal Capacity:    7.75 tons Oil Capacity:    1570 gals Water Capacity:    
5000 gals

Remarks:     In 1930 it became clear that the 'Ab' class Pacifics would have to be replaced on the heaviest and fastest trains in the North Island. The requirement was for a non-articulated locomotive developing 50 per cent more power. The design prompt resulted in the 'K' class and the massive boiler dictated that a 4-8-4 wheel arrangement would be necessary. It was a masterpiece of design, for within the restricted confines of the NZR loading gauge (maximum height above rail 11' 6"; maximum width 8' 6") was built a locomotive developing a tractive effort of 30,815 lb, yet having an axle loading of only 14 tons. Features of the 'K' were roller bearing axle-boxes on all axles, Commonwealth cast-steel firebox cradle and rear engine truck, power reversing gear, grease-lubricated floating bronze bushes on the side rods, twin Westinghouse air-compressors, a mechanical lubricator, and an air-operated firedoor. These magnificent locomotives had very little in the way of teething troubles and were extremely successful in passenger and freight work over difficult country. All K class engines were converted to oil burning bewteen 1947 and 1953.
The 1960s saw the introduction of diesel-electric main-line locomotives and the last K's were withdrawn in 1964.

Preserved Locomotives
  Museum of Transport and Technology,    Auckland -     K 900,     NZR Hutt #277/1932   Static Display
  Mainline Steam,    Wellington -     K 911,     NZR Hutt #288/1934   Stored Facebook Page