Локомотивы Bulleid Light Pacific: West Country и Battle of Britain

Class of 110 three cylinder 4 6 2 locomotives

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. 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. The results were similar to the rebuilt Merchant Navy class. The classes operated until July 1967, when the last steam locomotives on the Southern Region were withdrawn.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.

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. 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. 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.

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 It gained notoriety because it was difficult to access when things went wrong and, in tandem with the fast moving Bulleid steam reverser, could cause irregular valve movements. As with the Merchant Navies, the class soon gained the nickname "Spam Cans", due to the resemblance to the distinctive tin cans in which "SPAM" was sold. The gauges had fluorescent markings and were illuminated by ultra violet light. This enabled clearer night time vision of the boiler steam pressure gauge and the brake pipe vacuum pressure gauge whilst eliminating dazzle, making it easier for the crew to see signals along the track. As an aid to the fireman, a treadle used steam pressure to open the firehole doors, where the coal is shovelled into the firebox. The inner and outer Belpaire firebox was also smaller than the Merchant Navy class also constructed using welded steel. The cylinders were smaller at .

Bulleid designed a reduced capacity tender based upon the Merchant Navy version. It could carry water and of coal on a six wheel underframe. From this batch onwards, traction was improved by the addition of steam sanding to the front driving wheel, with covers added to protect the motion from sand falling from the filler pipes. A third batch of twenty five was ordered and designated the Battle of Britain class. These were identical to the West Country class and the new designation was purely concerned with giving the locomotives names that befitted their intended allocation to the Eastern Section. In March 1949, British Railways ordered a final 20 from Brighton works despite a pressing need for smaller tank locomotives. This imbalance was rectified by building forty one examples of the LMS Fairburn 2 6 4T for the Southern Region. Two of the front route indicator irons (of which there are five) were originally located on the smoke deflectors, which meant that the indicator discs stood proud of the casing. This necessitated a trial relocation to the smokebox door at the three and nine o'clock positions on No. 21C109 Lyme Regis, and fitted as standard from No. 21C118 Axminster onwards. Over the next decade the revised design was fitted to existing members of the class. Another modification was the reduction of boiler pressure to to reduce maintenance costs. but these were never used on this duty and the cab was widened to 9 feet (3 m) on the British Railways batch. The tenders of Nos. 21C166–21C170 were fitted with TIA ("Traitement Integral Armand") chemical feed water equipment that precipitated scale forming constituents in the hard water of southern England into a non adhesive mud that could be cleared using a manual "blow down" valve. This equipment was retrospectively fitted to earlier members of the class. In 1948 the tender design was enlarged to provide a water capacity of The resultant "cut down" tender included new, enclosed storage for fire irons and glass spectacle plates to protect the crew from flying coal dust when running tender first. When the rebuilding programme (see below) was halted in 1961, further modifications were made to the unrebuilt locomotives. The most notable was on No. 34064 Fighter Command, which was fitted with a Giesl ejector in 1962 on the grounds that a desired spark arrestor would "suffocate" an ordinary blastpipe. Following some adjustment, the ejector improved smoke deflection and fuel consumption, allowing it to steam well with low grade coal. As a consequence of the positive experience with No. 34064, preserved No. 34092 City of Wells was similarly fitted in the mid 1980s.

Bulleid employed the same idiosyncratic numbering scheme that he had used for the Merchant Navy class, beginning at No. 21C101 and reaching No. 21C170 at the time of nationalisation. His scheme was abolished by British Railways, which renumbered existing these 34001 34070 and new locomotives 34071 34110. The first 48 members of the class were named after places in the West Country served by its trains or close to its lines. This represented a publicity success due to many of the locomotives being able to visit their namesake areas. Many 'West Country' locomotives sported an additional plaque with the coat of arms of the town or region the locomotive was named after. This plaque was mounted on the casing between the gunmetal locomotive nameplate and the West Country Class scroll, above the middle driving wheel. The background of the nameplate was usually painted red, though sometimes examples could be found in black if the locomotive works undertaking overhaul of the engine could not locate the correct colour paint. Once it became clear that the locomotives would be used further afield than the West Country, a decision was made to name the remainder after RAF squadrons, airfields, commanders and aircraft that had participated in the Battle of Britain over Kent, Surrey and Sussex. An enamelled crest of the aircraft, personality or squadron was placed below the nameplate, in the same position as the West Country class equivalent. The first locomotives constructed by British Railways were of the Battle of Britain class, but the naming policy reverted to the West Country for Nos. 34091–34108. Thus 66 Squadron was the only Battle of Britain class member not to have a crest.

The original intention was to base the first batch of locomotives at Exmouth Junction depot at Exeter for use on the West of England Main Line to Salisbury and Plymouth, and secondary lines to Barnstaple, Bude and other holiday resorts in Devon and Cornwall.

As with the Merchant Navy class, they could generate great power using mediocre quality fuel, due largely to Bulleid's excellent boiler. They also ran smoothly at high speed, but they were also beset with the same technical problems of their larger sisters. These may be summarised as follows:
Adhesion problems. The lighter loading on their driving axles meant that they were even more prone to wheelslip than the Merchant Navy class, requiring very careful control when starting a heavy train. Once underway they were noted for their free running, excellent steam production and rapid turn of speed. The fires were also attributed to oil overflowing from axlebox lubricators onto the wheels when stationary, to be flung upwards into the boiler lagging in service. Restricted driver visibility due to the air smoothed casing and soft steam exhaust from the multiple jet blastpipe. The exhaust problem was never adequately resolved, and smoke continued to beat down onto the casing while moving, obscuring the driver's vision.

On 29 October 1959, locomotive No. 34020 Seaton was hauling a passenger train that overran signals and was derailed by trap points at , Hampshire. On 20 February 1960, locomotive No. 34084 253 Squadron was hauling a freight when it overran signals at and was derailed, falling down an embankment and onto its side. The tender was recovered on 24 February and the locomotive on 28 February. On 12 December 1960, locomotive No. 34022 Exmoor was hauling a passenger train that overran signals and was derailed by trap points at St Denys. Two people were injured. On 11 April 1961, locomotive No. 34040 Crewkerne was in a head on collision with an electric multiple unit at Waterloo station, London after the latter overran signals. One person was killed and fourteen were injured. On 2 September 1961, locomotive No. 34045 Ottery St Mary was derailed by trap points at , Hampshire. On 23 November 2013, locomotive No. 34067 Tangmere was hauling a passenger excursion when it suffered a mechanical failure whilst approaching Winchfield in Hampshire at about 40 mph (64 km/h). The right hand valve gear connecting rod partly detached and dropped down onto the track. Some damage was done to the track but there were no injuries. On 7 March 2015, locomotive No. 34067 Tangmere was hauling a charter train that overran a signal at Wooton Bassett, Wiltshire. The train's operator, West Coast Railway Company was banned from running trains on the British railway network as a consequence of this incident. On 24 July 2017, locomotive No. 34070 Manston was involved in a collision with BR Standard Class 4 2 6 4T locomotive no 80104 outside Swanage station on the Swanage Railway. Nobody was injured in the incident but damage was caused to both locos.

Restricted driver visibility was mentioned in the report on the disastrous Lewisham rail crash on 4 December 1957 outside St John's railway station, in which 90 people were killed and 173 injured. The driver of No. 34066 Spitfire had failed to see one yellow and one double yellow "caution" signal in foggy conditions and was travelling too fast to stop when he saw a red signal, and the train crashed into the back of a stationary local train. Members of the class were later fitted with Automatic Warning System equipment, a recommendation of the incident report; fitting of trackside equipment was already underway, but priority had been given to routes equipped with semaphore signals, not electric "colour light" signals as at Lewisham. The report on the disaster indicated that it was necessary, with the signals concerned being on the right hand side of the train and because of the limited visibility from the left hand side of a steam locomotive, for either the fireman to observe those signals (but with the driver being responsible for asking him to do so) or for the driver to cross over the footplate from his left hand driving position to observe them from the other side. In the event, the driver did neither, and neither driver nor fireman looked out for the aspect of the signals. The report ascribed blame to the driver, but recommended that the class be fitted with wider windscreens to improve visibility, noting that, in fog with less than 80 yards of visibility, the three signals involved would not be visible at all from the driver's side of the footplate; however, it noted that, even from a Schools class locomotive with its much smaller boiler, it was unlikely that these signals could have been seen from the driver's side in the dense foggy conditions of the incident. The report did not suggest that poor lifting of smoke obstructed visibility.

The rebuilding solved most of the maintenance problems whilst retaining the excellent features of the original design. Repair costs were reduced by up to 60%, and coal consumption was reduced by up to 8.4%. However the Walschaerts valve gear made the rebuilds heavier and prone to hammerblow on the track, a complaint that was not evident with the original design.

Livery was Southern Railway malachite green with "Sunshine yellow" horizontal lining. A circular cast brass plate with a red background on the smokebox door featured the word "Southern" and the date of manufacture. Bulleid advocated a continental style of numbering, basing this upon his experiences at the French branch of Westinghouse Electric before the First World War, and his tenure in the Railway Operating Division (R. O. D.) during that conflict. The Southern Railway number adapted the UIC classification system where "2" and "1" refer to the number of un powered leading and trailing axles respectively, and "C" refers to the number of driving axles, in this case three. However, since "21C" was the prefix already used by the Merchant Navy class, the suffix "1" was added; these locomotives carried numbers that started "21C1" followed by the individual two digit identifier. In December 1953 they were reclassified 7P 5FA, the "A" denoting brake power when used on unfitted (non vacuum braked) goods trains. The rebuilt locomotives retained this classification until all received the classification of 7P6F between November 1957 and November 1961. The locomotives were turned out in British Railways Brunswick green livery with orange and black lining with the British Railways crest on the tender side, after their first overhaul under new ownership. This was unlike the Merchant Navy class, which was initially turned out in British Railways experimental express passenger blue livery. By this stage, the Southern Railway built locomotives were re liveried and renumbered from 34001–34070. The cab side was given a representation of the medal and its ribbon, which was displayed until the engine was withdrawn from service and scrapped in the late 1960s. The original nameplate and crest were recovered and displayed in the entrance hall of ROC Headquarters at RAF Bentley Priory until 1996 when they were transferred to the RAF Museum at Hendon. Another locomotive that featured a second crest was 34067 Tangmere, which was given the airfield's crest for the cab side, as it did not feature on the nameplate crest.

The class in both unrebuilt and rebuilt forms has been the subject of divergent opinions. The steam raising ability of their boilers represented an advance in British steam technology. Their light axle loading also meant widespread use over the Southern network, and they were capable of fast running. Despite these successes, the number of innovations introduced at the same time made the class unreliable and difficult to maintain. A great deal of money was wasted on resolving the problems of a class designed for duties that could have been undertaken by cheaper 2 6 2 or 4 6 0 mixed traffic locomotives. Hornby Dublo produced diecast metal "rebuilt" West Countries in the 1960s, and those became Triang Wrenn, and ultimately Wrenn Railways. Wrenn produced air smoothed versions and rebuilt versions, right through to their demise (and subsequent sale to Dapol) in the early 1990s. Hornby manufactures ready to run rebuilt and un rebuilt examples of the class and caters for all the major detail variations. Graham Farish and Dapol produce ready to run models in N gauge.