NZR Q class (1901)

NZR Q class
A NZR Q class locomotive
Power type	Steam
Builder	Baldwin Locomotive Works, Philadelphia, USA
Serial number	19202–19207 19248–19254[1]
Build date	1901
Configuration	4-6-2
Gauge	3 ft 6 in (1,067 mm) Cape gauge
Driver diameter	49.1 in (1.25 m)
Wheelbase	48 ft 4 in (14.73 m)
Length	55 ft 4 in (16.87 m)
Weight on drivers	30.7 long tons (31.2 t)
Locomotive weight	48.0 long tons (48.8 t)
Tender weight	24.1 long tons (24.5 t)
Locomotive & tender combined weight	72.1 long tons (73.3 t)
Fuel type	Coal
Fuel capacity	5.0 long tons (5.1 t)
Water capacity	1,700 imp gal (7,700 L)
Boiler pressure	200 psi (1,400 kPa)
Firegrate area	40 sq ft (3.7 m2)
Cylinders	Two
Cylinder size	16 × 22 in (41 × 56 cm)
Tractive effort	18,340 lbf (81.6 kN)
Locomotive brakes	Steam
Train brakes	Vacuum
Number in class	13
Number	338-350[1]
Locale	Auckland - Rotorua Oamaru - Dunedin
First run	1901-12-24
Retired	1957-12-07
Disposition	All scrapped

The NZR Q class was an important steam locomotive not only in the history of New Zealand's railway network but also in worldwide railways in general. Designed by New Zealand Government Railways' 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.

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.

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 A^B classes; in fact, later in life, they were re-boilered with A^B boilers.

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.

The members of this Q class should not be confused with the members of 1878's Q class. As all of the 1878 locomotives had been withdrawn by 1901, the classification was free to be used again.

References

1. ^ ^{a b} "Q Class 4-6-2 Register". http://www.trainweb.org/nzsteam/q462_reg.htm. Retrieved 2008-02-10. 

Further reading

• Heath, Eric, and Stott, Bob; Classic Steam Locomotives Of New Zealand, Grantham House, 1993

External links

• NZR Steam locomotives - Q class
• 1934 article on the development of the Pacific locomotive from The New Zealand Railways Magazine