LSWR O2 Class

LSWR/SR O2
Number W24 Calbourne and vintage ex-SECR carriage on the Isle of Wight Steam Railway (c) Ron Strutt.
Type and origin Power type Steam Designer William Adams Builder LSWR Nine Elms Works Build date 1889–1895 Total produced 60
Specifications Configuration: ​  • Whyte 0-4-4T Gauge 4 ft 8 1⁄2 in (1,435 mm) standard gauge Driver dia. 58 in (1.473 m) Trailing dia. 37 in (0.940 m) Length 30 ft 8.5 in (9.360 m) Loco weight 48.40 long tons (49.18 t; 54.21 short tons) Fuel type Coal Fuel capacity 1.50 long tons (1.52 t; 1.68 short tons); later 3.25 long tons (3.30 t; 3.64 short tons) Water cap 800 imp gal (3,600 L; 960 US gal) Boiler pressure 160 psi (1.10 MPa) Cylinders Two, inside Cylinder size 17 1⁄2 in × 24 in (444 mm × 610 mm)
Performance figures Tractive effort 17,235 lbf (76.67 kN)
Career Operators London and South Western Railway, Southern Railway, Southern Region of British Railways Class LSWR: O2 SR: O2 Power class Isle of Wight: B BR: 0P Locale Great Britain Disposition One preserved, remainder scrapped

The LSWR O2 Class is a class of 0-4-4T steam locomotive designed for the London and South Western Railway by William Adams. Sixty were constructed during the late nineteenth century.

Adams was presented with the problem of a greatly increasing volume of commuter traffic experienced with the suburbanisation of London during the 1880s. This was exacerbated by the fact that there were few locomotive classes in the LSWR stable that could undertake commuter traffic at the desired level of efficiency. The LSWR therefore required a locomotive with attributes of power and compactness, with a small wheel size to gain acceleration on intensive timetables. Adams settled upon the 0-4-4T wheel arrangement to provide the basis of what was to become the O2 Class.

The second of William Adam's 0-4-4 designs, the O2 Class was a development of his previous T1 class of 1888. The brief behind the design was to create a locomotive capable of mixed-traffic operations, a characteristic dictated by the relatively small wheel diameter and smaller cylinders, effectively to replace the obsolete Beattie Well Tank. As a result, a compact locomotive with high route availability was produced, a factor that would be essential during the later career of the class.

Production began in 1889, with the first 20 being constructed at the LSWR's Nine Elms works. The success of the locomotive ensured that a second batch of 30 locomotives was ordered the next year. A final batch of ten was constructed by 1895.

The class was initially used intensively on London suburban services, but began to be replaced on these as early as 1897 by the introduction of the more powerful Drummond M7 and T1 classes. As a result, the O2s were cascaded to lighter services, and became distributed throughout the LSWR system, being of particular use on restricted branch lines due to their relatively low weight and short wheelbase.

All of the O2s survived to be taken into Southern Railway ownership after the Grouping in 1923. They continued to be used across the former LSWR network, however, electrification and the introduction of more modern types started to make them redundant. This allowed the Southern Railway to send the first 2 spare examples across to the Isle of Wight (see below). Other redundant mainland locomotives were withdrawn, with eight going in the 1930s, and four more in the 1940s.