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. In Britain in particular the Pacific type locomotives were developed to an extremely fine locomotive of which the "Flying Scotsman" was the first steam locomotive to break the 100m/h (160km/h) barrier in 1932, and the Mallard also a Pacific class, which reached a top speed of 126m/h (202km/h) a few years later. These were the pinnacle of British locomotive engineering, all based on the Pacific 4-6-2 design originating from New Zealand.
Locomotive classification is then a means of grouping engines of the same general characteristics, and while New Zealand experimented with an earlier classification based predominantly cylinder diameter, it soon adopted wheel configuration as a more practical method as that often dictated a locomotives function. There are two classification systems used, the American and the Continental. Why the American method was adopted in New Zealand is unknown, but it is based on counting the number of wheels in the groups that make up a loco. 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 at speed. 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 be placed 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 those used in New Zealand are 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, which was also a very successful New Zealand locomotive.
There are other less common groups of engines of which NZR had two, the most well known are the Fairlie locomotive, of which two were the first 3ft 6in gauge locomotives in New Zealand, and later classified 'E'. They have two independent power units on separate bogies, 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. NZR 1906 experimental E class was similarly notated although this was classified as a Mallet locomotive due to among other things, only one power being on a bogie, the other being fixed to the locomotive chassis.
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.
With the Continental System here are two styles for steam engines, the original that counts axles in each group rather than wheels as in the American system, and the newer method which also caters for diesels and electric locomotives. It uses a letter system to denote driven axles where B, C, D, E, and F stand for 2, 3, 4, 5, and 6 consecutive driven axles, and numbers represent idling axles i.e. 1, 2, 3 represent a sequence of idling axles in a group. To differentiate Diesel and a Steam loco's, the Diesel loco's are either Bo or Co for 2 or 3 driven axles in a bogie, there are no 4 driven axle examples. Returning to our Pacific class example, it would be written as 2C1 and the F class as C.
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 | - |