NZR R class

NZR R class
NZR R class on Jervois Quay, Wellington
Type and origin Power type Steam Builder Avonside Engine Co., England Build date 1878-79
Specifications Configuration: ​  • Whyte 0-6-4T Gauge 3 ft 6 in (1,067 mm) Driver dia. 36.5 in (0.927 m) Wheelbase 21 ft 10 in (6.65 m) Adhesive weight 20 long tons (20.3 t; 22.4 short tons) Loco weight 33 long tons (33.5 tonnes; 37.0 short tons) Firebox:  • Firegrate area 11.8 sq ft (1.10 m2) Boiler pressure 160 lbf/in2 (1,103 kPa) Heating surface 556 sq ft (51.7 m2) Cylinders Two, outside Cylinder size 12.25 in × 16 in (311 mm × 406 mm)
Performance figures Maximum speed 53 mph (85 km/h) Tractive effort 8,420 lbf (37.45 kN)
Career Operators New Zealand Railways Department Number in class 18 Disposition 1 preserved

The NZR R class was a class of early 0-6-4T single Fairlie steam locomotives operated by New Zealand's Railways Department (NZR) between 1879 and 1936.

In the 1870s New Zealand's railway network was a small, fragmented system of light railway lines built in rough country where short, steep grades and tight curves were common. The Fairlie type of steam locomotive was well-suited to working in such conditions. In 1872, the first Fairlie locomotives arrived from England, the E class. Gradually the number of these double-ended engines (known as Double Fairlies) grew to 10, and came to include the B class of 1874. There was still a need for orthodox engines with Fairlie manoeuvrability. The Avonside Engine Company of Bristol, England solved the problem by providing both the R and S classes of Single Fairlie engines; 18 of the former in 1878-79 and 7 of the latter in 1880-81. The R class locomotives were built at Avonside's Bristol factory and then shipped to New Zealand, with all entering service by early March 1880.

The locomotives quickly earned a good reputation for speed and manoeuvrability. On a trial run, Charles Rous-Marten timed one as running from Upper Hutt to Wellington, a distance of 20 miles, in 32.5 minutes despite a number of short delays amounting to three minutes; one section of two miles was covered at a maximum speed of 53 miles per hour. They were allocated to depots across the country, and during their working life operated almost all types of services from premier passenger trains to shunting tasks. As built, they could carry 716 gallons of water, but to allow them to operate over extended distances, some were later fitted with 900 gallon side tanks. All were reboilered during their lives to raise the boiler pressure from 130 to 160 pounds per square inch.