NZR J class (1939)

The NZR J class steam locomotives were a class of locomotive used in New Zealand. Following the success of the K class on NZR main lines, there was an urgent need for a modern, powerful locomotive capable of running over secondary lines laid with lighter rails. Thus a new "Mountain" 4-8-2 type locomotive was designed and classified by NZGR as the new class J. The 40 locomotives were all built by North British Locomotive Works, Scotland. They should not be confused with the members of 1874's J class, the first tender locomotives to operate in New Zealand. 30 Js were initially allocated to the North Island, the other 10 to the hilly Dunedin-Oamaru section in the South Island where with Wab tank banker engines they provided extra power for wartime freight and passenger loads. By 1950 with a large number of Hillside JA in service the South Island allocation of J and Wab tanks had been returned to Auckland.

The class had a notable appearance with the boiler being partly streamlined after the style of the New Haven Railroad's J400 class, and was also similar to the Norfolk and Western Railway class J and the NSWGR 38 class. The J class incorporated all the latest ideas of the K^A class but a noteworthy departure was the use of the Baker valve gear. The tender was of the Vanderbilt type.

Twelve J class locomotives were converted to oil burning and reclassified as J^B class, and the bullet nose streamlining was gradually removed. In 1962 ten J were transferred back to the South Island to replace the A class on the steep Greymouth-Otira section and another 6 Js were transferred in the mid 1960s to the SIMT. Some J class locomotives were reboilered with boilers transferred from the first North Island JA withdrawals in 1964-66 and others from the remainder of 12 JA boilers supplied by North British in 1954 for the construction of the last ten Hillside JA. The first reboilered J was used on the Otira route while the rest were reboilered in 1967. J 1236 was refitted with JA 1281's boiler,^[2] and second NI JA boiler was approved for refitting to a J in mid 1967,^[3] 2 spare JA boilers were supplied with the delivery of the boilers, from North British, Glasgow for the last 10 JA to Hillside in 1953-54 and there was some swapping of boilers between JAs 1240 receiving JA 1255 boiler and J 1200 driving wheels in 1966 ^[4] The three J engines that were used with the JA class on the South Island Limited in its last years in 1969-70 and later preserved were effectively a new 'JC' class with JA boilers and North Island JA tenders, reconstructed for coal rather than oil supply and had North Island JA trailing trucks, under the cab. The original J had been mainly freight and banking engines on the NIMT and had only powered a few provincial passenger trains, the Opua Express, the Auckland- New Plymouth night express and the Tanetua express. J 1211 and J1234 with JA 1267 were the usual engines on the fast South Island Limited on the Christchurch-Oamaru section, in its last year, their 'JC' conversion having made them NZRs final mainline steam flyers.

JB class

The NZR J^B class steam locomotives were all originally members of the NZR J class of 1939. Built by North British Locomotive Works, Scotland, they all initially burned coal and wore distinctive bullet-like streamlining. 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.^[5] 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.^[6] 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.

Preserved Locomotive List

• J 1211 - Mainline Steam.
• J 1234 - Steam Incorporated.
• J^B 1236 (converted from J class to J^B class) - Mainline Steam.

Class register

References

External links

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