NZR A class (1906)
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| Type and origin | |
|---|---|
| Power type | Steam |
| Builder |
Addington Workshops (8), A & G Price (50) |
| Build date | 1906–1914 |
| Total produced | 58 |
| Specifications | |
|---|---|
| Configuration: |
|
| • Whyte | 4-6-2 |
| Driver dia. | 54 in (1.372 m) |
| Length | 57 ft 2 in (17.42 m) |
| Adhesive weight | 33 long tons 2 cwt (74,100 lb or 33.6 t) |
| Loco weight | 51 long tons 0 cwt (114,200 lb or 51.8 t) 55 long tons 0 cwt (123,200 lb or 55.9 t)(simple) |
| Tender weight | 25 long tons 10 cwt (57,100 lb or 25.9 t) |
| Fuel type | Coal |
| Fuel capacity | 4 long tons 0 cwt (9,000 lb or 4.1 t) |
| Water cap | 1,700 imp gal (7,700 L; 2,000 US gal) |
| Firebox: • Firegrate area |
30 sq ft (2.8 m2) |
| Boiler pressure | 225 psi (1,551 kPa) (as coumpound) 190 psi (1,310 kPa)(simple) |
| Heating surface | 1,724 sq ft (160.2 m2) |
| Cylinders | 2 HP, 2 LP |
| Cylinder size | 18 in × 22 in (457 mm × 559 mm)(simple) |
| High-pressure cylinder | 12 in × 22 in (305 mm × 559 mm) |
| Low-pressure cylinder | 19 in × 22 in (483 mm × 559 mm) |
| Performance figures | |
|---|---|
| Tractive effort | 17,000 lbf (76 kN) (as compound) 20,060 lbf (89.2 kN)(simple) |
| Career | |
|---|---|
| Operators | NZGR |
| Withdrawn | 1954–1969 |
| Preserved | Two: 423, 428 |
| Disposition | Two preserved, remainder scrapped |
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 Baldwin Q had established the Pacific as the way forward for Express passenger locomotives, but the C.M.E decided that greater efficiency was needed. The new locomotives were therefore designed as compounds. The Vauclain system had proved ineffective in New Zealand so the type attributed to Frenchman Alfred de Glehn was adopted.
The first four had Stephenson valve gear inside and Walschaerts valve gear outside, while the following 53 had just Walschaerts. The first eight locomotives were built at New Zealand Railways Department's Addington Workshops, the rest by A & G Price of Thames. The first twenty-seven were built with intercepting valves allowing full simple operation. This feature was later removed from all but the first four, and the last thirty were built without and classified as AD until 1915.
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