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SR West Country and Battle of Britain classes
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SR West Country and Battle of Britain classes
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" type 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.
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 1951, named after West Country resorts or Royal Air Force (R.A.F.) 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, 60 locomotives were rebuilt by British Railways during the late 1950s. The results were similar to the rebuilt Merchant Navy class. The classes operated until July 1967, when all the last steam locomotives on the Southern Region were withdrawn. Although most were scrapped, 20 locomotives are preserved on heritage railways in Britain.
The financial success enjoyed by the Southern Railway during the 1930s was based on the completion of its London suburban electrification scheme in 1929 and the subsequent electrification of the main lines to Brighton and the Sussex Coast and to Guildford and Portsmouth. Despite electrification plans, the Southern Railway's less heavily used lines in the West Country beyond Salisbury did not merit the cost. Lines in Devon and Cornwall were meandering, heavily graded, and although heavy with summer holiday traffic were lightly used during the winter months. The seasonality of railway traffic meant that the West Country branches were worked by the ageing T9 class 4-4-0 and the versatile N class 2-6-0 (Maunsell 2-6-0s), which could be better utilised on mixed-traffic services elsewhere. As a result, an order was placed with Brighton railway works in April 1941 for 20 passenger locomotives of a type to be determined.
During 1943, Bulleid began planning for the post-war locomotive requirements of the railway and identified the need for a stop-gap steam locomotive design for those main lines in South East England scheduled for electrification, had the Second World War not taken place. Although the new Merchant Navy class was available for the heaviest Continental expresses, the resumption of frequent passenger services over poorly maintained infrastructure, following the war, would require a lighter locomotive with wider route availability.
At the same time, there would be a continuing need for fast freight locomotives, capable of operating on both electrified and non-electrified routes, without impeding the intensive use of the system by passenger trains. Suburban electrification used electric multiple units, which had no equivalent freight design. Although Bulleid built two prototype electric locomotives in 1941, these were, as yet, unproven, and freight haulage would be undertaken by steam traction for the foreseeable future.
The detailed design work for the new mixed-traffic locomotives was undertaken at Brighton railway works where they were scheduled to be constructed. The earliest drawings were for a moderately sized 2-6-0 with similarities to the London and North Eastern Railway K4 class, which Bulleid had helped design for the West Highland Line when he was Nigel Gresley's assistant. However, such a design would have been inadequate for the Kent Coast lines, which required a powerful 2-6-2 or 4-6-0 class. It is not clear why the design was subsequently enlarged to become a smaller version of the Merchant Navy class 4-6-2 as the likely traffic requirement did not warrant such lavish provision, but the incorporation of components from that class enabled standardisation during wartime production difficulties.
In order to improve on the route availability of the Merchant Navy class with its 21-ton axle loading, the weight was reduced by 5 tons. This allowed the design to operate on routes where the Maunsell 2-6-0s were the largest permitted and came mainly from several changes:
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SR West Country and Battle of Britain classes
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" type 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.
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 1951, named after West Country resorts or Royal Air Force (R.A.F.) 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, 60 locomotives were rebuilt by British Railways during the late 1950s. The results were similar to the rebuilt Merchant Navy class. The classes operated until July 1967, when all the last steam locomotives on the Southern Region were withdrawn. Although most were scrapped, 20 locomotives are preserved on heritage railways in Britain.
The financial success enjoyed by the Southern Railway during the 1930s was based on the completion of its London suburban electrification scheme in 1929 and the subsequent electrification of the main lines to Brighton and the Sussex Coast and to Guildford and Portsmouth. Despite electrification plans, the Southern Railway's less heavily used lines in the West Country beyond Salisbury did not merit the cost. Lines in Devon and Cornwall were meandering, heavily graded, and although heavy with summer holiday traffic were lightly used during the winter months. The seasonality of railway traffic meant that the West Country branches were worked by the ageing T9 class 4-4-0 and the versatile N class 2-6-0 (Maunsell 2-6-0s), which could be better utilised on mixed-traffic services elsewhere. As a result, an order was placed with Brighton railway works in April 1941 for 20 passenger locomotives of a type to be determined.
During 1943, Bulleid began planning for the post-war locomotive requirements of the railway and identified the need for a stop-gap steam locomotive design for those main lines in South East England scheduled for electrification, had the Second World War not taken place. Although the new Merchant Navy class was available for the heaviest Continental expresses, the resumption of frequent passenger services over poorly maintained infrastructure, following the war, would require a lighter locomotive with wider route availability.
At the same time, there would be a continuing need for fast freight locomotives, capable of operating on both electrified and non-electrified routes, without impeding the intensive use of the system by passenger trains. Suburban electrification used electric multiple units, which had no equivalent freight design. Although Bulleid built two prototype electric locomotives in 1941, these were, as yet, unproven, and freight haulage would be undertaken by steam traction for the foreseeable future.
The detailed design work for the new mixed-traffic locomotives was undertaken at Brighton railway works where they were scheduled to be constructed. The earliest drawings were for a moderately sized 2-6-0 with similarities to the London and North Eastern Railway K4 class, which Bulleid had helped design for the West Highland Line when he was Nigel Gresley's assistant. However, such a design would have been inadequate for the Kent Coast lines, which required a powerful 2-6-2 or 4-6-0 class. It is not clear why the design was subsequently enlarged to become a smaller version of the Merchant Navy class 4-6-2 as the likely traffic requirement did not warrant such lavish provision, but the incorporation of components from that class enabled standardisation during wartime production difficulties.
In order to improve on the route availability of the Merchant Navy class with its 21-ton axle loading, the weight was reduced by 5 tons. This allowed the design to operate on routes where the Maunsell 2-6-0s were the largest permitted and came mainly from several changes:
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