New Zealand Railways class N
The class N was introduced in a time when more and more American locomotives were built for the NZR, as the American designs were generally lighter and more flexible than the British ones. The N was a 2-6-2 that was intended for passenger and mail working. In 1885, six were delivered to the NZR by Baldwin. Two similar locomotives were built in 1891 for the Wellington and Manawatu Railway Company (WMR). The last four were again for the NZR and arrived in 1901. Later the WMR received four similar locomotives which were Vauclain compounds.
Originally, all were used on the North Island. In 1892, WMR No. 9 set a cape gauge speed record with 64.4 mph or 103.6 km/h. In World War I, the two WMR locomotives came to the Westland region of the South Island. All were withdrawn between 1926 and 1934. Although none were preserved, WMR No. 9 was one of the locomotives which had been buried in Bealey River. It was dug out between 2003 and 2006 and now, Steam Incorporated is restoring it.
Technical data
General
| Property | 1885 variant | 1901 variant |
|---|---|---|
| Built | 1885, 1891 | 1901 |
| Manufacturers | Baldwin | |
| Wheel arrangement | 2-6-2 (Prairie) | |
| Gauge | 1,067 mm (Cape gauge) | |
Dimensions and weights
| Property | 1885 variant | 1901 variant |
|---|---|---|
| Length | 15.29 m | |
| Wheelbase | 7.06 m | 6.73 m |
| Total wheelbase | 12.90 m | 12.48 m |
| Service mass | 29.7 t | 31.7 t |
| Adhesion mass | 22.9 t | 22.8 t |
| Total mass | 45.9 t | 49.9 t |
| Rigid wheelbase | 2.90 m | |
| Axle load | 7.9 t | 7.8 t |
| Water capacity | 22,731 l | |
| Fuel capacity | 7.6 t (coal) | |
Boiler
| Property | 1885 variant | 1901 variant |
|---|---|---|
| Grate area | 1.486 m² | |
| Firebox surface | 8.129 m² | 7.618 m² |
| Tube heating surface | 77.15 m² | 74.508 m² |
| Evaporative heating surface | 84.913 m² | 82.126 m² |
| Total heating surface | 84.9 m² | 82.1 m² |
Power plant
| Property | 1885 variant | 1901 variant |
|---|---|---|
| Driver diameter | 1,245 mm | |
| Boiler pressure | 9.3 bar | 13.8 bar |
| Expansion type | simple expansion | |
| Cylinders | two, 381 x 508 mm | |
Power
| Property | 1885 variant | 1901 variant |
|---|---|---|
| Power source | steam | |
| Estimated power | 261 kW (355 PS) | 298 kW (405 PS) |
| Starting effort | 46.9 kN | 69.4 kN |
Calculated values
| Property | 1885 variant | 1901 variant |
|---|---|---|
| Factor of adhesion | 1 : 4.79 | 1 : 3.22 |
| Optimal speed | 34 km/h | 26 km/h |
| Power-to-weight ratio | 8.8 kW/t | 9.4 kW/t |
| Heating Surface Equivalent | 125.9 m² | 120.2 m² |
| Cylinder volume/HSE | 1 : 919.87 | 1 : 963.54 |
| Adhesive weight/Total | 1 : 1.30 | 1 : 1.39 |
| Tractive force/Heating surface | 1 : 11.53 | 1 : 17.66 |
| Grate area/Heating surface | 1 : 57.14 | 1 : 55.27 |
| Firebox/Tube surface | 1 : 9.49 | 1 : 9.78 |