SR Class Q

SR Q class
541 at the Bluebell Railway 11 October 1992
Type and origin Power type Steam Designer Richard Maunsell Builder SR Eastleigh Works Build date 1938–1939 Total produced 20
Specifications Configuration: ​  • Whyte 0-6-0  • UIC C h2 Gauge 4 ft 8 1⁄2 in (1,435 mm) standard gauge Driver dia. 5 ft 1 in (1.549 m) Length 53 feet 9 1⁄2 inches (16.40 m) Width 8 ft 4 in (2.54 m) Height 12 ft 0 in (3.66 m) Loco weight 49 long tons 10 cwt (110,900 lb or 50.3 t) (55 short tons) Tender weight 40 long tons 10 cwt (90,700 lb or 41.1 t) (45 short tons) Total weight 90 long tons 0 cwt (201,600 lb or 91.4 t) (101 short tons) Fuel type Coal Fuel capacity 5 long tons (5.1 tonnes; 5.6 short tons) Water cap 3,500 or 4,000 imp gal (15,900 or 18,200 l; 4,200 or 4,800 US gal) Boiler pressure 200 lbf/in2 (13.79 bar; 1.38 MPa) Cylinders Two, inside Cylinder size 19 in × 26 in (483 mm × 660 mm)
Performance figures Tractive effort 26,160 lbf (116.37 kN)
Career Operators Southern Railway → British Railway (Southern Region) Class SR: Q Power class BR: 4F Numbers SR: 530–549 BR: 30530–30549 Withdrawn 1962–1965 Disposition One preserved, remainder scrapped

The Q Class, is a type of 0-6-0 steam locomotive designed by Richard Maunsell of the Southern Railway and constructed immediately prior to the Second World War, for use on medium-distance freight trains throughout the network. Twenty locomotives were built by Maunsell's successor, Oliver Bulleid, in 1938. The design was relatively old-fashioned and the class was soon afterwards eclipsed by Bulleid's own more powerful Q1 class. Nevertheless the locomotives performed adequately and reliably on the tasks for which they were designed until their withdrawal in 1965. Only one has survived, and is preserved on the Bluebell Railway.

The Southern Railway was primarily a passenger-carrying railway which used most of its resources to extend its electrified lines. There was a continuing need for steam freight locomotives however, although the Traffic Department preferred mixed traffic designs which could also haul passenger trains on the remaining non-electrified lines at peak periods. By the late 1930s the Southern Railway was adequately served with powerful mixed traffic locomotives of the S15 and N and N1 classes, but there was a need for a smaller freight locomotive with high route availability that could also undertake light passenger duties. This role had been performed by the ex-LSWR 'Jubilee' A12 0-4-2, which were approaching the end of their useful lives. During his last year as the Chief Mechanical Engineer (CME) of the Southern Railway Richard Maunsell decided on an inside-cylinder 0-6-0 tender locomotive to undertake this role, in what was to become the Q Class of 1938. This was a relatively ‘old-fashioned’ design for the late 1930s, although each of Britain’s major railways built locomotives of this pattern until the 1940s. The class nevertheless contained several ‘modern’ features such as a Belpaire firebox, superheater, and a side-window cab. It was the last Southern steam locomotive design before the Second World War, and represented the final design of Maunsell's career, as he retired due to ill-health in 1937.