The OB class was the first class of steam locomotives constructed by the Baldwin Locomotive Works for the Wellington and Manawatu Railway Company (WMR) in New Zealand. The class consisted of two locomotives ordered in 1888, and they entered service in September of that year as WMR No.'s 11 and 12.[1]

NZR OB class
Wellington and Manawatu Railway 11, circa 1904
Type and origin
Power typeSteam
BuilderBaldwin Locomotive Works
Serial number9018, 9021
Build date1888
Total produced2
Specifications
Configuration:
 • Whyte2-8-0
 • UIC1′C n
Gauge3 ft 6 in (1,067 mm)
Driver dia.43 in (1.092 m)
Length51 ft 3 in (15.62 m)
Adhesive weight34 long tons 6 cwt (76,800 lb or 34.9 t)
34 long tonshundredweight (34.9 t; 38.4 short tons)
Loco weight38 long tons 10 cwt (86,200 lb or 39.1 t)
38 long tons 10 hundredweight (39.1 t; 43.1 short tons)
Tender weight19 long tons 2 cwt (42,800 lb or 19.4 t)
19 long tons 2 hundredweight (19.4 t; 21.4 short tons)
Fuel typeCoal
Fuel capacity3 long tons 10 cwt (7,800 lb or 3.6 t)
3 long tons 10 hundredweight (3.6 t; 3.9 short tons)
Water cap.1,500 imp gal (6,800 L; 1,800 US gal)
Firebox:
 • Grate area16.5 sq ft (1.53 m2)
Boiler pressure165 lbf/in2 (1,138 kPa)
Heating surface1,013 sq ft (94.1 m2)
CylindersTwo, outside
Cylinder size16 in × 20 in (406 mm × 508 mm)
Valve gearStephenson
Valve typeSlide valves
Performance figures
Tractive effort15,177 lbf (67.51 kN)
Career
OperatorsWellington and Manawatu Railway
New Zealand Government Railways
NumbersWMR 11, 12
NZR 455, 456
LocaleWellington - Longburn section
Retired1931, 1929
DispositionWithdrawn

When the WMR and its locomotive fleet was acquired by the government and merged into the national New Zealand Railways (NZR) in 1908, the two locomotives were considered to be similar to the O class but with enough differences to warrant the separate OB classification. No. 11 became OB 455 and No. 12 became OB 456, and they ended their days working around Napier. OB 456 was retired in September 1929, and was followed in March 1931 by OB 455, which had survived to be one of the final operating locomotives of WMR heritage, along with NC 461 and UD 465, both of which were withdrawn in the same month.

Notes

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References

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  • Millar, Sean (2011). The NZR Steam Locomotive. Wellington: New Zealand Railway and Locomotive Society. ISBN 978-0-908573-89-9.
  • Palmer, A. N.; Stewart, W. W. (1965). Cavalcade of New Zealand Locomotives. Wellington: A H. & A W. Reed. ISBN 978-0-207-94500-7.
  • Stewart, W. W. (1974). When Steam was King. Wellington: A. H. & A. W. Reed Ltd. ISBN 978-0-589-00382-1.