NZR WW class

Last updated

NZR WW class
Ww644.jpg
WW 644 as preserved on the Glenbrook Vintage Railway in 2011.
Type and origin
Power typeSteam
Designer A. L. Beattie
Builder NZGR Hillside Workshops (50), Hutt Workshops (14)
Build date1913-1919
Total produced50 built new, 14 rebuilt from WG class at Hutt Workshops
RebuilderNZR Hutt Workshops, Hillside Workshops
Rebuild date1940-42,1950-60
Number rebuilt14 (from WG class), 12 (from WW class)
Specifications
Configuration:
   Whyte 4-6-4T
Gauge 3 ft 6 in (1,067 mm)
Driver dia.45 in (1.143 m)
Wheelbase 29 ft 7.5 in (9.03 m)
Length36 ft 11.5 in (11.26 m)
Adhesive weight 29.7 long tons (30.2 t; 33.3 short tons)
Loco weight51.5 long tons (52.3 tonnes; 57.7 short tons)
Fuel type Coal
Fuel capacity2 tons
Water cap.1,370 imp gal (6,200 L)
Firebox:
  Grate area16.9 sq ft (1.57 m2)
Boiler pressure180 lbf/in2 (1,241 kPa)
Heating surface526 sq ft (48.9 m2)
SuperheaterNZR
Cylinders Two, outside
Cylinder size 15.5 in × 22 in (394 mm × 559 mm)
Valve gear Walschaerts
Valve typeSlide valves (WW 565), piston valves (all locomotives)
Train brakes Westinghouse compressed air
Performance figures
Tractive effort 16,910 lbf (75.22 kN)
Career
Operators NZR
Number in class51
Numbers131, 449, 479-482, 486, 488-496, 556-561, 562 (later 667), 563-575, 638-647, 668-685
Nicknames"Bobtails"
LocaleAll of New Zealand
Delivered1913
Withdrawn1969
Preserved4
DispositionWithdrawn, four preserved
Ww Class steam locomotive NZR 131, 4-6-4T, Petone Workshops Ww Class steam locomotive NZR 131, 4-6-4T type, Petone Workshops ATLIB 288509.png
Ww Class steam locomotive NZR 131, 4-6-4T, Petone Workshops

The NZR WW class was a class of 4-6-4T tank locomotives that operated on the New Zealand national railway network. They were built for New Zealand Railways Department (NZR), and were the final development of the six-coupled tank engine in New Zealand, the penultimate class of tank locomotives to be built for NZR, and the first class of tank locomotives to be built with superheaters. [1]

Contents

Introduction

The WW class were based on the earlier WG class 4-6-4T tank locomotives, but with a reduced boiler pressure of 180psi and larger cylinders. [2] The initial batch comprising locomotives WW 556-575 were built at Hillside Workshops in 1913, and initially carried the WG classification before being reclassified as the WW class, the 'W' indicating that these locomotives were intended for suburban work in Wellington.

Following the success of the first 20 locomotives, Hillside delivered a further 30 locomotives, which were classified WW from new. A further 14 locomotives were rebuilt from the WG class at Hutt Workshops in two batches between 1940–42 and 1950-52. [3]

Although most of the class were built with piston valves, WW 565 was delivered with slide valves, which were not suited to superheated steam, leading to their replacement with standard piston valves.

In service

The WW class demonstrated to be extremely versatile in service, being capable of handling almost any task. Initially both Auckland and Wellington received allocations of these locomotives which were used in suburban passenger service and occasionally on goods work; later allocations saw engines of this class allocated to the West Coast at Westport and Greymouth. Here, the locomotives worked mostly on coal trains and occasionally hauled branch line passenger services.

During the early 1950s, the decision was made to fit new higher-pitched boilers with deeper fireboxes to four WG class locomotives, Nos. 479, 480, 486 and 488, as a trial when they were rebuilt to WW class specifications. This required a new type of smokebox saddle, cab and enlarged coal bunker. This alteration was deemed to be successful, adding an extra 100 sq. ft. of heating surface; [4] rather than rebuild the remaining six WGs due to the poor condition of their frames, NZR decided to rebuild 12 existing WW class locomotives, Nos. 571, 573-575, 644, 669, 672, 678-680, 683-684.

During the early 1960s, several of the WW class locomotives transferred from the North Island to Greymouth on the West Coast were altered to operate on the Rewanui Incline by the provision of 'trap-door' cowcatchers to clear the centre rail and additional air reservoirs on the tops of the side tanks. Following the removal of the centre rail in 1966, the locomotives' extra reservoirs were removed and the original brake pump was replaced by two larger pumps, one on each side of the smokebox. [5]

Withdrawal

The first member of the WW class to be withdrawn was WW 491, which was withdrawn from service in August 1955 for use as a sectionalised aid for apprentice training at Otahuhu Workshops. A further 43 locomotives were withdrawn by the first half of the 1960s, by which time the remaining 21 locomotives were in service in Auckland and on the West Coast. Further withdrawals were at a slower pace, with a final seven locomotives still in service on the West Coast at the beginning of 1969. [6]

Preservation

Four WW class locomotives have been preserved, all in the North Island of New Zealand. Three were rebuilt with higher-pitched boilers while the fourth retains its original low-pitched boiler:

In addition, Steam Incorporated also owned an original low-pitched WW boiler which had originally been fitted to WW 646. This boiler was purchased for industrial use at the Ford Motor Company plant in the Hutt Valley in the 1970s and was stored at Paekakariki until early 2015 when it was sold to MOTAT to aid the future restoration of WW 491.

See also

References

Citations

  1. Palmer & Stewart 1965, p. 122.
  2. Palmer & Stewart 1965, p. 102.
  3. Millar 2011, p. 304.
  4. Housego, C J (October 1970). "Eight Hundred Miles By Steam". Railway Magazine. p. 553. Retrieved 12 December 2016.
  5. Millar 2011, p. 305-06.
  6. Millar 2011, p. 305.
  7. "New Zealand Rolling Stock Register - Class WW".
  8. "NZ Steam - WW class register".

Bibliography