NZR Q class (1901)

The NZR Q class was an important steam locomotive class not only in the history of New Zealand's railway network but also in worldwide railways in general. Designed by New Zealand Government Railways' (NZR) Chief Mechanical Engineer A. L. Beattie and ordered from the Baldwin Locomotive Works in 1901, they were the first locomotives in the world to be built with the wheel arrangement of 4-6-2. This wheel arrangement came to be known as the Pacific type after the voyage the completed locomotives had to make across the Pacific Ocean to New Zealand. A few instances of the 4-6-2 wheel arrangement are known to have existed prior to 1901, but these were all reconstructions of locomotives that were originally built with a different wheel arrangement, thereby making the thirteen members of the Q class the first "true" Pacifics in the world. The Pacific style went on to become arguably the most famous wheel arrangement in the world.[2]

Not to be confused with NZR Q class (1878).

NZR Q class
Builder's photo of NZR Q class locomotive
Type and origin
Power typeSteam
BuilderBaldwin Locomotive Works, Philadelphia, USA
Serial number19202–19207
19248–19254[1]
Build date1901
Total produced13
Specifications
Configuration:
​
 • Whyte4-6-2
Gauge3 ft 6 in (1,067 mm)
Driver dia.49.1 in (1.247 m)
Wheelbase48 ft 4 in (14.73 m)
Length55 ft 4 in (16.87 m)
Adhesive weight30.7 long tons (31.2 t; 34.4 short tons)
Loco weight48.0 long tons (48.8 t; 53.8 short tons)
Tender weight24.1 long tons (24.5 t; 27.0 short tons)
Total weight72.1 long tons (73.3 t; 80.8 short tons)
Fuel typeCoal
Fuel capacity5.0 long tons (5.1 t; 5.6 short tons)
Water cap.1,700 imp gal (7,700 L; 2,000 US gal)
Firebox:
 • Firegrate area		40 sq ft (3.7 m2)
Boiler pressure200 psi (1,379 kPa)
Heating surface1,683 sq ft (156.4 m2)
CylindersTwo
Cylinder size16 in × 22 in (406 mm × 559 mm)
Loco brakeSteam
Train brakesAir
Performance figures
Tractive effort18,340 lbf (81.6 kN)
Career
Number in class13
Numbers338-350[1]
LocaleAuckland - Rotorua
Oamaru - Dunedin
First run1901-12-24
Retired1957-12-07
DispositionAll scrapped

Design

The Q class's design stems from the requirement for a locomotive similar to the UB class with the inclusion of a wide firebox to burn poor quality lignite coal from the South Island and the Waikato. Originally plans to equip the new locomotives with a Wootten Firebox would have seen the "Camelback" configuration adopted.

Operation

In operation, the locomotives proved to be satisfactory rather than brilliant and they suffered from occasional gear problems. They were soon displaced from the most important and difficult work by members of the A and AB classes; in fact, later in life, they were re-boilered with AB boilers. An improved slightly larger 'Q' type was ordered from Baldwins in 1914, but classified AA due to their dimensions similar to the A class.

In a 1902 trial of various locomotives between Invercargill and Gore, the Q class with large fire-grate area "gave the most efficient results" of the larger locomotives.[3]

Withdrawal

They saw out their final years working in Otago and the West Coast and the last Q class locomotive was retired in 1957. No examples of the class were preserved.

See also

References

Citations
  1. "Q Class 4-6-2 Register". Retrieved 10 February 2008.
  2. Palmer & Stewart 1965, p. 79.
  3. "Engine Trials Invercargill-Gore". AJHR D6, 1903 on Papers Past. 1903.

Bibliography
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.