NZR JB class

NZR J^B class

Type and origin Power type Steam Builder North British Locomotive Works, Glasgow, Scotland Build date 1939

Specifications Configuration 4-8-2 Gauge 3 ft 6 in (1,067 mm) Wheel diameter 54 in (1.372 m) Wheelbase 34 ft 10 in (10.62 m) Length 66 ft 11 in (20.4 m) Adhesive weight 44.45 long tons (45.16 t; 49.78 short tons) Loco weight 68.55 long tons (69.65 t; 76.78 short tons) Tender weight 40.35 long tons (41.00 t; 45.19 short tons) Total weight 108.9 long tons (110.6 t; 122.0 short tons) Fuel type Oil Fuel capacity 1,350 imp gal (6,100 L; 1,620 US gal) Water cap 4,000 imp gal (18,000 L; 4,800 US gal) Firebox:  • Firegrate area 39.0 sq ft (3.6 m^2) Boiler pressure 200 psi (1,379 kPa) Heating surface 1,469 sq ft (136.5 m^2) Superheater: ​  • Heating area 283 sq ft (26.3 m^2) Cylinders 2 Cylinder size 18 in × 26 in (457 mm × 660 mm) Valve gear Baker

Performance figures Maximum speed approx. 72 mph (116 km/h) Tractive effort 24,960 lbf (111.0 kN)

Career Number in class 12 Numbers 1200, 1203, 1205-06, 1213, 1218, 1224, 1228-30, 1233, 1239 Locale North Island of New Zealand First run 1939 - 1940 Last run 1964 - 1967 Retired 1964 - 1968 Scrapped 1964 - 1968 Disposition All scrapped.

The NZR J^B class steam locomotives were all originally members of the J class of 1939. Built by North British Locomotive Works, Scotland, they all initially burned coal and wore distinctive bullet-like streamlining.

Conversion to oil burning

After World War II the railways suffered problematic coal shortages, especially in the North Island. Approval was gained to convert 12 of the J class locomotives into oil-burners, to burn heavy fuel oil which was available in plentiful quantities at the time. The conversion saw the installation of a two-nossle burner in the firebox, removal of the grate and ashpan which was replaced with a firepan lined with bricks, shortening of the superheater tubes in the boiler, removal of the spark arrester in the smokebox, removal of the brick arch, addition of the related controls and gauges for the oil burning equipment, and the tender modified to carry an oil bunker and associated steam piping. Similar to the K and K^A Classes which were converted to oil burning at the same time, the J^B Class utilized a separate, removable tank which sat in the former coal space. However, the full-width coal bunker of the J-type's Vanderbilt tender was cut down so that the oil tank was visible at the sides, with distinctive vertical supports below. The conversion process generally coincided with the removal of the streamlining, but not always. Once converted, the locomotives were re-classified J^B in recognition of the conversion, however they retained their original J class numbers.

The J^B Class in service

In service the J^B class performed well, but did not distinguish themselves above the unconverted J class nor any of the other J variants. Some of the J^B Class received cross-compound Westinghouse pumps in place of the twin single-phase pumps, but others did not. The J^B Class only ever saw service in the North Island, as in the South Island coal supplies were plentiful. Some years after conversion to oil, the fuel oil being used became considerably dearer than the coal supplies then being sourced, and there was no longer a coal shortage. However re-conversion back to coal burning did not occur due to objections from the various railway Unions.

Withdrawal and disposal

Some members of the J^B Class were among the first of the J 4-8-2 types to be withdrawn, due to the faster wear and tear suffered by the locomotives as a result of oil burning. The last of the class was withdrawn from service by March 1968, by which time steam haulage in the North Island had essentially finished anyway.^[1] All of the class were scrapped, although many items from the locomotives were retained as spares for the other J type locomotives still in service in the South Island.

Preservation

No J^B class locomotives were preserved, although the tender from J^B 1203 is held by Steam Incorporated. In addition, preserved J class locomotive No. 1236 has been restored as a J^B class oil burner by its owners Mainline Steam, although this particular locomotive spent its entire NZR career as a coal-burning J Class.^[2] Preserved locomotive J 1211, also owned by Mainline Steam, has been converted to oil burning in the same manner as the J^B class, but has not been re-classified to reflect that change.

Class register

Key:	In service	On lease	Out of service	Preserved	Overhaul/Repair	Scrapped

Number	Builder	Entered service	Withdrawn	Notes
1200	North British	October 1939	July 1964
1203	North British	November 1939	October 1964	Tender held by Steam Incorporated.
1205	North British	November 1939	October 1967
1206	North British	November 1939	May 1965
1213	North British	December 1939	December 1967
1218	North British	January 1940	April 1967
1224	North British	February 1940	August 1967
1228	North British	March 1940	March 1968
1229	North British	March 1940	January 1965
1230	North British	March 1940	October 1964
1233	North British	March 1940	December 1967
1239	North British	March 1940	March 1968

References

1. Register of New Zealand Steam Locomotives, W.G. Lloyd
2. The Locomotives of the Mainline Steam Trust, by Graeme Moffatt

External links

• NZR Steam locomotives - J class (4-8-2)
• NZR Steam locomotives - J class (4-8-2)