NZR Locomotive Types
Steam Locomotives
NZR used a wide range of steam locomotive types, particularly in its formative years. While every 'type' has one or two formal classification codes, not all of them have class names, however, there is one name in particular that has stamped its mark in history as being a pure New Zealand design and that is the "Pacific". Born from the need to develop more power from the existing narrow gauge "ten-wheeler" locomotives (4-6-0), NZR ordered 13 wide fire-box versions configured as a 4-6-2, which had never been tried before. These were over-all a successful locomotive, from which the A and W classes (and consequently sub-classes) evolved, which went on to become the work-horses of the mid-range engines for New Zealand up until the end of the steam era.
Locomotive classification is then a means of grouping engines of the same general characteristics, and while New Zealand experimented with a some early concepts (predominantly cylinder diameter, it soon adopted wheel configuration as a more practical method as that often dictated a locomotives function. Why the American method of describing these was adopted is unknown, but it is based on counting the number of wheels in each of group, with a standard locomotive usually having three groups of wheels; the ones driven by the pistons, commonly called the Drivers, and a group in front of those, and a group behind, usually referred to as leading and trailing trucks. The leading truck is quite important in stabilising the front end of the locomotive, guiding it more gently into curves. The trailing truck (if present) helps carry the load of the firebox which particularly with wide fireboxes that do not fit between the drivers, can fit above the smaller wheels of a trailing truck.
So a standard wheel arrangement is composed of three numbers and expressed in the following way: 4-6-2 for a 4 wheel leading truck, 6 driving wheels, and a single axle trailing truck , so 2 wheels. This corresponds to the "Pacific" class of locomotive.
There are additional letters that can follow the 3-number code and these are generally T for a Tank Engine or ST for a Saddle Tank engine, so we have 0-6-0ST for the F class saddle Tank engines.
There are other less common groups of engines of which NZR had two, the most well known are the Fairlie locos, of which two were the first 3ft 6in gauge locomotives in New Zealand, and later classified 'E'. They have two independent power units so end up with a 4-number code and in this case they are 0-4-4-0 representing no leading truck, 4 driven wheel followed by 4 more driven wheels, and no trailing truck. The 1906 E class was similarly notated although this was classified as a Mallet locomotive.
The final group to consider is the Garratt locomotives. Looking at them you can see that they look like two locomotives sharing a single large boiler, and that is exactly how they are notated, 4-6-2+2-6-4. you can see this as two groups of the 3-number code joined with a plus sign. When proven unsuccessful as a single locomotive, each power unit received its own boiler and became a G class Pacific, or 4-6-2.
The following table lists all the steam locomotive Types used in New Zealand in ascending order of by Driven axles, Front axles, Rear axles
| Wheel arrangement |
Type Name | NZR Classes | Total Number |
Continental Code |
|---|---|---|---|---|
| 0-4-0T | - | A, D, S(1876) | 15 | - |
| 0-4-0ST | - | A, D | 12 | - |
| 0-4-2T | - | H | 6 | - |
| 0-4-2ST | - | C | 15 | - |
| 0-4-4-0T | Fairlie | B, E | 10 | - |
| 2-4-0T | - | L | 10 | - |
| 2-4-2 | Columbia | K(1878) | 8 | - |
| 2-4-4 | - | Q(1879) | 13 | - |
| 4-4-0T | - | La | 3 | - |
| 4-4-0ST | - | G(1875) | 6 | - |
| 0-6-0T | - | F, M, Y | 95 | - |
| 0-6-2T | - | Fa, Fb | 20 | - |
| 0-6-4T | - | S(1882) | 7 | - |
| 2-6-0 | - | J(1875) | 32 | - |
| 2-6-2 | Prairie | N, Na, Nc, V | 29 | - |
| 2-6-2T | - | W, Wa, Wh | 16 | - |
| 2-6-4T | - | Wab, Wb, Wd, Wf, Ws | 101 | - |
| 2-6-6-0T | Mallet | E(1906) | 1 | - |
| 4-6-0 | 10 Wheeler | U, Ua, Ub, Uc, Ud | 49 | - |
| 4-6-2 | Pacific | A, Aa, Ab, Ad, G(1932), Q | 220 | - |
| 4-6-2+2-6-4 | Garrat | G(1929) | 3 | - |
| 4-6-4T | - | We, Wg, Ww | 73 | - |
| 2-8-0 | Consolidation | O, Oa, Ob, Oc | 10 | - |
| 2-8-0T | - | T | 6 | - |
| 2-8-4T | - | Wj | 1 | - |
| 2-6-2 | 12 Wheeler | B, Ba, Bc | 21 | - |
| 4-8-2 | Mountain | J(1939), Ja, Jb, X | 109 | - |
| 4-8-4 | - | K(1932), Ka, Kb | 71 | - |