| NZR UD class | |
|---|---|
| Power type | Steam |
| Builder | Baldwin Locomotive Works |
| Build date | 1904 |
| Total produced | 2 |
| Configuration | 4-6-0 |
| Gauge | 3 ft 6 in (1,067 mm) |
| Driver diameter | 4 ft 10 in (1.47 m) |
| Locomotive weight | 39.5 long tons (40.1 t) |
| Tender weight | 27.4 long tons (27.8 t) |
| Fuel type | Coal |
| Water capacity | 2,400 imp gal (11,000 l; 2,900 US gal) |
| Tender capacity | 5 long tons (5.1 t) |
| Boiler pressure | 185 psi (1.28 MPa) |
| Firegrate area | 16.1 sq ft (1.50 m2) |
| Cylinders | 2 |
| Cylinder size | 16.5 × 22 in (420 × 560 mm) |
| Number in class | 2 |
| Retired | 1929 |
The NZR UD class was a class of two 4-6-0 steam locomotives built by the Baldwin Locomotive Works in 1904 for the Wellington and Manawatu Railway Company. Two locomotives were built.
Weighing 39.5 tons with a tender of 27.4 tons, they could haul express trains easily at 50 miles per hour (80 km/h) in suitable parts of the country. With huge (for the period) 58 inches (1,473 mm) coupled driving wheels, a working steam pressure of 185 pounds per square inch (1,276 kPa), and 16.5 inches (419 mm) diameter cylinders with 22 inches (559 mm) piston strokes, the handsome "Ud"s were more than capable of making up lost time with mile-a-minute runs as recalled with pride by old Manawatu railway employees.
However, fast and powerful as they were the "Ud"s were unable to survive the standardisation program between 1925 and 1935 and were written off in 1929.