NZR UB class

The NZR U^B class were a series of Ten Wheelers built by American manufacturers for New Zealand Railways around the start of the twentieth century. Two batches were built by Baldwin in 1898 and 1901. The earlier batch of engines had slide valves and inside Stephenson motion, the later had piston valves and Walschaerts valve gear, as well as a higher boiler pressure.

Alco engines

Two additional locomotives were obtained in 1901 from ALCO, one each from Brooks and Richmond.

The Brooks locomotive was heavier with attendant increase in tractive effort, and had a larger grate. This locomotive was very popular with crews. This locomotive was dumped on the Oamaru foreshore.
The Richmond locomotive had less evaporative heating surface but included a superheater. Boiler pressure was lower and tractive effort was marginally lower.

The locomotives were initially assigned to Dunedin to Christchurch expresses and were reassigned as newer power replaced them. The last assignment for the class was on the West Coast Region.