NZR A class (1906)
Encyclopedia
The A class were steam locomotive
s built in 1906 with a 4-6-2
wheel arrangement
for New Zealand
's national railway network, and described by some as the most handsome engines to run on New Zealand rails. The class should not be confused with the older and more obscure A class of 1873
. They were designed by the New Zealand Railways Department
's Chief Mechanical Engineer, A. L. Beattie
and his Chief Draughtsman, G. A. Pearson to replace less powerful locomotives struggling with increasing loads on the South Island Main Trunk Railway
, and in anticipation of the traffic volumes that would be created upon the completion of the North Island Main Trunk Railway.
The first four had Stephenson valve gear
inside and Walschaerts valve gear outside, while the following 53 had just Walschaerts. They were initially de Glehn compound locomotive
s, but complications with the compounding led to their being superheated
and then converted to two-cylinder simple locomotives. Performance of the engines did not suffer and they operated extensively in both islands.
The first eight locomotives were built at New Zealand Railways Department
's Addington Workshops
, the rest by A & G Price
of Thames
. The final 30, constructed between 1910 and 1914, had a number of small differences from the original design and they were initially classified as the AD class. In 1916 they were reclassified A. One member of the class, A 409 was a shade lighter in weight than the other A's.
The A class locomotives initially operated express services, but in time they were superseded and were relegated to minor branch line services. Such large locomotives often looked out of place pulling insignificant rural trains on uneconomic lines that were liable to be closed. Nonetheless, the A class survived almost to the end of steam in New Zealand, with the last one withdrawn in 1969. The final A class to be withdrawn was A 428. It was saved by the Weka Pass Railway
rail preservation society, and is the only fully operational member of the class left. A 423 has been preserved by private owners; recently relocated to the Glenbrook Vintage Railway
, it is kept as a static exhibit, pending restoration to operational condition.
Two other classes based on similar designs were the AA
and AB
classes. The AB class went on to become New Zealand's most prolific locomotive class.
Steam locomotive
A steam locomotive is a railway locomotive that produces its power through a steam engine. These locomotives are fueled by burning some combustible material, usually coal, wood or oil, to produce steam in a boiler, which drives the steam engine...
s built in 1906 with a 4-6-2
4-6-2
4-6-2, in the Whyte notation for the classification of steam locomotives, represents the wheel arrangement of four leading wheels on two axles , six powered and coupled driving wheels on three axles, and two trailing wheels on one axle .These locomotives are also known as Pacifics...
wheel arrangement
Wheel arrangement
In rail transport, a wheel arrangement is a system of classifying the way in which wheels are distributed beneath a locomotive.. Several notations exist to describe the wheel assemblies of a locomotive by type, position, and connections, with the adopted notations varying by country...
for New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
's national railway network, and described by some as the most handsome engines to run on New Zealand rails. The class should not be confused with the older and more obscure A class of 1873
NZR A class (1873)
The A class was the second class of steam locomotive ordered to work on New Zealand's national railways. It should not be confused with the more numerous A class 4-6-2 tender locomotives of 1906. Initially ordered by the Public Works Department for use in the construction of lines, the A class...
. They were designed by the New Zealand Railways Department
New Zealand Railways Department
The New Zealand Railways Department, NZR or NZGR and often known as the "Railways", was a government department charged with owning and maintaining New Zealand's railway infrastructure and operating the railway system. The Department was created in 1880 and was reformed in 1981 into the New...
's Chief Mechanical Engineer, A. L. Beattie
A. L. Beattie
Alfred Luther Beattie , typically referred to as A. L. Beattie, was a pioneering locomotive engineer. Born in Yorkshire, England, he gained fame as the Chief Mechanical Engineer of the New Zealand Railways Department between 1900 and 1913...
and his Chief Draughtsman, G. A. Pearson to replace less powerful locomotives struggling with increasing loads on the South Island Main Trunk Railway
South Island Main Trunk Railway
The Main North Line between Picton and Christchurch and the Main South Line between Lyttelton and Invercargill, running down the east coast of the South Island of New Zealand, are sometimes together referred to as the South Island Main Trunk Railway...
, and in anticipation of the traffic volumes that would be created upon the completion of the North Island Main Trunk Railway.
The first four had Stephenson valve gear
Stephenson valve gear
The Stephenson valve gear or Stephenson link or shifting link is a simple design of valve gear that was widely used throughout the world for all kinds of steam engine. It is named after Robert Stephenson but was actually invented by his employees....
inside and Walschaerts valve gear outside, while the following 53 had just Walschaerts. They were initially de Glehn compound locomotive
Compound locomotive
A compound engine unit is a type of steam engine where steam is expanded in two or more stages.A typical arrangement for a compound engine is that the steam is first expanded in a high-pressure cylinder, then having given up heat and losing pressure, it exhausts directly into one or more larger...
s, but complications with the compounding led to their being superheated
Superheater
A superheater is a device used to convert saturated steam or wet steam into dry steam used for power generation or processes. There are three types of superheaters namely: radiant, convection, and separately fired...
and then converted to two-cylinder simple locomotives. Performance of the engines did not suffer and they operated extensively in both islands.
The first eight locomotives were built at New Zealand Railways Department
New Zealand Railways Department
The New Zealand Railways Department, NZR or NZGR and often known as the "Railways", was a government department charged with owning and maintaining New Zealand's railway infrastructure and operating the railway system. The Department was created in 1880 and was reformed in 1981 into the New...
's Addington Workshops
Addington Workshops
The Addington Railway Workshops was a major railway facility established in the Christchurch suburb of Addington in May 1880 by the New Zealand Railways Department. The workshops were previously in Carlyle Street and closed in 1990.-Description:...
, the rest by A & G Price
A & G Price
A & G Price Limited is an engineering firm and locomotive manufacturer in Thames, New Zealand, established in 1868. In 2004 a precision formed yacht keel division was formed to make the Maximus canting keel...
of Thames
Thames, New Zealand
Thames is a town at the southwestern end of the Coromandel Peninsula in New Zealand's North Island. It is located on the Firth of Thames close to the mouth of the Waihou River. The town is the seat of the Thames-Coromandel District Council....
. The final 30, constructed between 1910 and 1914, had a number of small differences from the original design and they were initially classified as the AD class. In 1916 they were reclassified A. One member of the class, A 409 was a shade lighter in weight than the other A's.
The A class locomotives initially operated express services, but in time they were superseded and were relegated to minor branch line services. Such large locomotives often looked out of place pulling insignificant rural trains on uneconomic lines that were liable to be closed. Nonetheless, the A class survived almost to the end of steam in New Zealand, with the last one withdrawn in 1969. The final A class to be withdrawn was A 428. It was saved by the Weka Pass Railway
Weka Pass Railway
The Weka Pass Railway is a New Zealand heritage railway based in Waipara, North Canterbury. It is operated on a 12 km length of the former Waiau Branch railway between Waipara and Waikari. The railway is operated by an incorporated society whose members come from all walks of life and are largely...
rail preservation society, and is the only fully operational member of the class left. A 423 has been preserved by private owners; recently relocated to the Glenbrook Vintage Railway
Glenbrook Vintage Railway
The Glenbrook Vintage Railway is a steam railway in Glenbrook, New Zealand. One of New Zealand's premiere rail heritage sites, it is not a museum as such, but rather a fully self-supporting, operating steam railway, built almost entirely by volunteer labour...
, it is kept as a static exhibit, pending restoration to operational condition.
Two other classes based on similar designs were the AA
NZR Aa class
The AA class consisted of ten steam locomotives built to operate on New Zealand's national rail network. Built to a similar design to the A class of 1906, they had a wheel arrangement of 4-6-2 and were suited to hauling freight services. Ordered and built in 1914, all ten entered service in New...
and AB
NZR Ab class
The NZR AB class was a class of 4-6-2 Pacific tender steam locomotive that operated on New Zealand's national railway system. Originally an improvement on the 1906 A class, 141 were built between 1915 and 1927 by NZR's Addington Workshops, A & G Price Limited of Thames, New Zealand, and North...
classes. The AB class went on to become New Zealand's most prolific locomotive class.
External links
- Information on the preserved A class locomotives from the Weka Pass Railway: A 423 and A 428
- A new engine at the Addington Workshops, 1906 (photo)