SR West Country and Battle of Britain classes

SR unrebuilt West Country/Battle of Britain classes[1]
34103 Calstock in 1962
Type and origin Power type Steam Designer Oliver Bulleid Builder SR/BR Brighton Works (104) BR Eastleigh Works (6) Build date 1945–1951 Total produced 110
Specifications Configuration: ​  • Whyte 4-6-2 (Pacific) Gauge 4 ft 8+1⁄2 in (1,435 mm) standard gauge Leading dia. 3 ft 1 in (0.940 m) Driver dia. 6 ft 2 in (1.880 m) Trailing dia. 3 ft 1 in (0.940 m) Length 67 ft 4.75 in (20.54 m) Loco weight 86 long tons (87.4 t; 96.3 short tons) Fuel type Coal Fuel capacity 5.00 long tons (5.1 t; 5.6 short tons) Water cap. 4,500 imp gal (20,460 L; 5,400 US gal) Firebox: ​  • Grate area 38.25 sq ft (3.55 m2) Boiler pressure 280 psi (1.93 MPa) Cylinders 3 Cylinder size 16.375 in × 24 in (416 mm × 610 mm)
Performance figures Tractive effort 31,046 lbf (138.1 kN)
Career Operators Southern Railway British Railways (Southern Region) Class SR / BR: Light Pacifics Power class BR (January 1949): 6MT BR (December 1953): 7P5F BR (November 1957): 7P6F Numbers SR: 21C101 – 21C170 BR: 34001–34110 Locale Great Britain Withdrawn 1963–1967 Disposition 60 rebuilt (see below); 10 preserved, 40 scrapped

The SR West Country and Battle of Britain classes, collectively known as Light Pacifics or informally as Spam Cans, or "flat tops", are air-smoothed 4-6-2 Pacific steam locomotives designed for the Southern Railway by its Chief Mechanical Engineer Oliver Bulleid. Incorporating a number of new developments in British steam locomotive technology, they were amongst the first British designs to use welding in the construction process, and to use steel fireboxes, which meant that components could be more easily constructed under wartime austerity and post-war economy.^[2]

They were designed to be lighter in weight than their sister locomotives, the Merchant Navy class, to permit use on a wider variety of routes, including the south-west of England and the Kent coast. They were a mixed-traffic design, being equally adept at hauling passenger and freight trains, and were used on all types of services, frequently far below their capabilities. A total of 110 locomotives were constructed between 1945 and 1950, named after West Country resorts or Royal Air Force (RAF) and other subjects associated with the Battle of Britain.

Due to problems with some of the new features, such as the Bulleid chain-driven valve gear, sixty locomotives were rebuilt by British Railways during the late 1950s.^[3] The results were similar to the rebuilt Merchant Navy class.^[4] The classes operated until July 1967, when the last steam locomotives on the Southern Region were withdrawn. Although most were scrapped, twenty locomotives are preserved on heritage railways in Britain.