NZR A Class (1906)

NZR A Class (1906)

The A class were steam locomotives 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 locomotives, 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The A class locomotives initially operated express services, but in time they were superseded and were relegated to minor branch line services.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 Nonetheless, the A class survived almost to the end of steam in New Zealand, with the last one withdrawn in 1969. The final A class to be withdrawn was A 428.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.