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 "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 The classes operated until July 1967, when all the last steam locomotives on the Southern Region were withdrawn.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.
Background
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.
Design
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.
Weight reduction and reduced loading gauge
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:
- reduced overall length
- smaller boiler
- more fabricated assemblies
- smaller tender (West Country only)
Also the cab was reduced in width and remodelled to comply with reduced loading gauge over some routes.
Bulleid's features
thumb|right|alt=An almost solid disc (not spoked) locomotive wheel with a series of cast-in radial indentations and prominent round holes intended to reduce its weight.|The distinctive [[Bulleid Firth Brown wheels, seen here on 34072 257 Squadron]]
Based on the mechanical experience gained from the Merchant Navy locomotives, Bulleid incorporated his chain-driven valve gear into what became the new design. 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. 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.
Tender
thumb|34016 Bodmin taking water at [[Alton railway station|Alton]]
Bulleid designed a reduced capacity tender based upon the Merchant Navy version. It could carry water and of coal on a six-wheel underframe. It retained the BFB wheels and streamlining panels, or "raves", that gave the top of the tender a similar cross-sectional outline to carriages. 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 .
To ease maintenance and lubrication, panels of air-smoothed casing ahead of the cylinders were removed from 1952, and the front sanders were blanked off. 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.
Numbering and naming the locomotives
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 same time of nationalisation. His scheme was abolished by British Railways, which renumbered existing these 34001-34070 and new locomotives 34071-34110.
thumb|left|alt=A 'West Country' class enamelled metal nameplate and shield mounted on flat metal casing covering the locomotive's boiler. The nameplate comprises a scroll, and below this is a shield containing a picture of a coat-of-arms. A second scroll is below the shield, allowing identification as a member of the 'West Country class'.|Nameplate configuration 1:<br />West Country (34007 Wadebridge)
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. Several members of the class had only the nameplate and the "West Country Class" scroll, a gap being left where a crest would have been mounted. 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.
thumb|right|alt=A 'Battle of Britain' class enamelled metal nameplate and crest mounted on flat metal casing covering the locomotive boiler. The nameplate forms a representation of aircraft wings, with a small rectangle attached to the middle-lower edge allowing identification as a member of the 'Battle of Briain' class. Below this is an oval-shaped plate with a crest.|Nameplate configuration 2:<br />Battle of Britain (34081 92 Squadron)
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. 'Battle of Britain' nameplates incorporated the name of the locomotive with the class name below, in a design that resembled the wings of an aircraft. This was painted Air Force blue, though other colours were sometimes substituted for the same reasons as above. 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. The final two locomotives were Battle of Britain class, No. 34109 Sir Trafford Leigh-Mallory and No. 34110 66 Squadron. The result of the delay in completing was that the squadron crest for 66 Squadron was never made, as the manufacturer had retired during the intervening period. Thus 66 Squadron was the only Battle of Britain class member not to have a crest.
Operational details
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. By the winter of 1945, there was a more pressing need for them on Kent Coast services. The class also began to be used on Continental Boat Trains to and from Dover and Folkestone once these were resumed in 1946. Later batches were used on cross-country services such as the Brighton to Bournemouth, Cardiff and Plymouth trains or the Somerset and Dorset Joint Railway trains from Bournemouth to Wells and Bath.
Because of the good route availability the locomotives could be used on non-electrified lines between London and Brighton. These included the Oxted Line, and occasionally the Bluebell Line between East Grinstead and Lewes, where they were also used for freight and parcels traffic, and excursion trains over electrified lines. Thus the original intention for the West Country class locomotives to work in South West England and the Battle of Britain class in Kent, Hampshire, Sussex and Surrey was never operationally practical and both classes were to be found all over the network.
Performance of the unrebuilt locomotives
thumb|34067 Tangmere working a [[Poole-Cardiff charter train west of Bath on 11 June 2011]]
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.
- 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 Wootton 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.
Lewisham railway disaster
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.