NZR JB class

NZR JB class
Power type	Steam
Builder	North British Locomotive Works, Glasgow, Scotland
Build date	1939
Configuration	4-8-2
Gauge	3 ft 6 in (1,067 mm) Cape gauge
Wheel diameter	54 in (1.4 m2)
Wheelbase	34 ft 10 in (10.6 m)
Length	66 ft 11 in (20.4 m)
Weight on drivers	44.45 long tons (45.16 t)
Locomotive weight	68.55 long tons (69.65 t)
Tender weight	40.35 long tons (41.00 t)
Locomotive & tender combined weight	108.9 long tons (110.6 t)
Fuel type	Oil
Fuel capacity	1,350 imp gal (6,100 L)
Water capacity	4,000 imp gal (18,000 L)
Boiler pressure	200 psi (1,400 kPa)
Firegrate area	39.0 square feet (3.6 m2)
Heating surface: Total	1,469 square feet (136.5 m2)
Superheater area	283 square feet (26.3 m2)
Cylinders	2
Cylinder size	18 × 26 in (46 × 66 cm)
Valve gear	Baker
Top speed	approx. 72mph
Tractive effort	24,960 lbf (111.0 kN)
Number in class	12
Number	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Disposition	Withdrawn; 0 preserved.

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

None of the J^B Class were Preserved. However, 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.

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)