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Ab Class
CLASS  Ab     4-6-2


Introduced:    1915 Number in Class:    141

Ab Class Register




Locomotive Specifications

Builders:
  1.   NZR Addington (38)
  2.   North British Locomotive Co., Glasgow, Scotland (83)
  3.   A & G Price Ltd., Thames (20)

Engine Weight:    
51.3 tons
Tender Weight:    33.4 tons Total Weight:    84.7 tons Adhesive Weight:    
29.9 tons
Length over Buffers:    
62' 5"
Total Wheelbase:    52' 6" Engine Wheelbase:    27' 1" Coupled Wheelbase:    
10' 0"
Tender Wheelbase:    
14' 0"
Driver Wheel Dia.:    54" Cylinders HP:    
Two - 17" x 26"
Cylinders LP:    
Grate Area:    33.0 sq ft Evaporative Area:    
1148 sq ft
Superheated Area:    
204 sq ft
Working Pressure:    
180 psig
Tractive Effort:    
20030 lbs f
Coal Capacity:    4.0 tons Oil Capacity:     Water Capacity:    
3500 gals

Remarks:     Introduced in 1915 to replace the 'A' class compounds on the heaviest duties, it was a simple superheated "Pacific" of novel appearance, a feature being the cylindrical Vanderbuilt tender. In their prime the 'Ab' class handled all principle express trains, and until the advent of the 'K's and 'J's they were also the standard class of main-line freight locomotive. The 'Ab' was a very successful engine performing well over a range of freight and passenger duties. For its relatively modest size, it is believed to have been the first locomotive in the world capable of developing one horsepower for every 100lb of engine weight. Ballast blocks and increased loading on the leading bogie and a reduction on the trailing bogie, meant some weight re-distribution on the coupled axles. Eleven more were rebuilt from 'Wab' class 1947 - 1957.

Preserved Locomotives
  Steam Inc.,    Ferrymead -     Ab 608,    NZR Addington #163/1915    Stored
  Mainline Steam,    Wellington -     Ab 663,    NZR Addington #188/1917    Operating
  Pleasant Point Railway,    Pleasant Point -     Ab 699,    A&G Price #94/1922    Operating
  Kingston Flyer,    Kingston -     Ab 778,    NZR Addington #235/1925    Operating
  Kingston Flyer,    Kingston -     Ab 795,    NZR Addington #252/1927    Operating
  Glenbrook Vintage Railway,    Auckland -     Ab 832,    North British #23190/1925    Awaiting Restoration



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