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Kb Class
CLASS  Kb    4-8-4

Introduced: 1939 Number in Class: 6

Kb Class Register

Locomotive Specifications

  NZR Hillside

Engine Weight:    
94.8 tons
Tender Weight:    52.9 tons Total Weight:    147.7 tons Adhesive Weight:    
56.0 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:    
1984 sq ft
Superheated Area:    
485 sq ft
Working Pressure:    
200 psig
Tractive Effort:    
30815 lbs f
Coal Capacity:    7.5 tons Oil Capacity:     Water Capacity:    
5000 gals

Remarks:     The 'Kb' class is essenially a 'Ka' class fitted with a trailing truck two-cylinder booster engine, able to be cut in at low speed, giving an increase in tractive effort, for starting, of 6,000 lbs f. They were used on the Midland Line between Springfield and Arthur's Pass between 1939 and 1968 in freight train service. The booster enabled the 'Kb' to haul 550 ton westbound freight trains - twice the load for an 'Ab'. Like the 'Ka' the earlier models of 'Kb' had the streamilne shrouding, later discarded when the feedwater heater was replaced with an exhaust steam injector. The 'Kb' remained a coal-burner throughout its life.

Preserved Locomotive
  Mainline Steam,  Middleton, Christchurch -     Kb 968,     NZR Hillside #351/1939   Restoring