NZR A class (1906)

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NZR A class (1906)
Power type Steam
BuilderAddington Workshops, A & G Price
Build date1906
Total weight81 tons
Number in class57
Preserved2 (423, 428)

The A class was a steam locomotive built in 1906 with a 4-6-2 wheel arrangement for New Zealand's national railway network. It should not be confused with the older and more obscure A class of 1873. With all members of the original A class retired, the 'A' designation was re-used for these locomotives, described by some as the most handsome engines to run on New Zealand rails. The A class was designed by the New Zealand Railways Department's Chief Mechanical Engineer, A. L. Beattie, and his Chief Draughtsman, G. A. Pearson. They were built to replace less powerful locomotives struggling with increasing loads on the South Island Main Trunk Railway, and also in anticipation of the traffic volumes that would be created upon the completion of the North Island Main Trunk Railway.

The first four had both Stephenson valve gear inside and Walschaert valve gear outside, while the following fifty-three solely used Walschaert valve gear. The A class were initially de Glehn compound locomotives, but complications with the compounding led to the locomotives being superheated and then converted to two-cylinder simple locomotives. Performance of the engines did not suffer and they operated extensively on both islands.

The first eight A class locomotives were built at the New Zealand Railways Department's Addington Workshops, while the rest were built by A & G Price of Thames. The final thirty, constructed between 1910 and 1914, were built with a number of small differences to the original design and they were initially classified as the AD class. However, in 1916, they were reclassified as members of the A class.[1]

Although the A class initially operated express services, they were superseded with time and served their final days working on minor branch services. Such large locomotives often looked out of place pulling insignificant rural trains on lines that were in dire economic straits and approaching closure. Nonetheless, the A class survived almost to the end of steam in New Zealand, with the last one retired in 1969. The final A class to be retired was A 428 and it was saved by the preservation movement; today, it is the only fully operational member of the A class. One other member of the class has been preserved but kept as a static exhibit. It may be returned to operational condition in the future.

Two other classes built for New Zealand's railways based on similar designs were accordingly similarly categorised as the AA and AB classes. The AB class went on to become New Zealand's most prolific locomotive class.

See also

External links

  • Information on the preserved A class locomotives from the Weka Pass Railway: A 423 and A 428