NZR OB class

NZR OB class
Power type	Steam
Builder	Baldwin Locomotive Works
Serial number	9018, 9021
Build date	1888
Total produced	2
Configuration	2-8-0
UIC classification	1′C n
Gauge	3 ft 6 in (1,067 mm)
Driver diameter	43 in (1.092 m)
Length	51 ft 3 in (15.62 m)
Weight on drivers	34 tons 6 cwt (76,800 lb or 34.8 t)
Locomotive weight	38 tons 10 cwt (86,200 lb or 39.1 t)
Tender weight	19 tons 2 cwt (42,800 lb or 19.4 t)
Fuel type	Coal
Fuel capacity	3 tons 10 cwt (7,800 lb or 3.5 t)
Water capacity	1,500 imp gal (6,800 l; 1,800 US gal)
Boiler pressure	165 lbf/in² (1.14 MPa)
Firegrate area	16.5 sq ft (1.53 m2)
Heating surface: Total	1,013 sq ft (94.1 m2)
Cylinders	Two, outside
Cylinder size	16 × 20 in (406 × 508 mm)
Valve gear	Stephenson
Valve type	Slide valves
Tractive effort	15,177 lbf (67.51 kN)
Career	Wellington and Manawatu Railway New Zealand Government Railways
Number	WMR 11, 12 NZR 455, 456
Locale	Wellington - Longburn section
Retired	1931, 1929
Disposition	Withdrawn

The O^B class was the first class of steam locomotives constructed by the Baldwin Locomotive Works for the Wellington and Manawatu Railway (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. 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 sufficiently different to warrant the separate O^B classification. No. 11 became O^B 455 and No. 12 became O^B 456, and they ended their days working around Napier. O^B 456 was retired in September 1929, and was followed in March 1931 by O^B 455, which had survived to be one of the final operating locomotives of WMR heritage, along with N^C 461 and edit] External links

• New Zealand Steam locomotives — O^B class
• Baldwin Steam Trust's page of Baldwin locomotives built for the WMR - includes O^B class
• Drawing of an O^B class locomotive from Derek Brown