NZR OB class

NZR OB class
Type and origin
Power type Steam
Builder Baldwin Locomotive Works
Serial number 9018, 9021
Build date 1888
Total produced 2
Specifications
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 long tons 6 cwt (76,800 lb or 34.9 t)
Locomotive weight 38 long tons 10 cwt (86,200 lb or 39.1 t)
Tender weight 19 long tons 2 cwt (42,800 lb or 19.4 t)
Fuel type Coal
Fuel capacity 3 long tons 10 cwt (7,800 lb or 3.6 t)
Water capacity 1,500 imp gal (6,800 l; 1,800 US gal)
Boiler pressure 165 lbf/in2 (1,138 kPa)
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 in × 20 in (406 mm × 508 mm)
Valve gear Stephenson
Valve type Slide valves
Performance figures
Tractive effort 15,177 lbf (67.51 kN)
Career
Operator(s) Wellington and Manawatu Railway
New Zealand Government Railways
Number(s) WMR 11, 12
NZR 455, 456
Locale Wellington - Longburn section
Retired 1931, 1929
Disposition Withdrawn

The OB 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 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survived to be one of the final operating locomotives of WMR heritage, along with NC 461 and UD 465, both of which were withdrawn in the same month.

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