SR Merchant Navy class

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SR Merchant Navy Class
Official Southern Railway photograph of 21C1 Channel Packet as built, 1941.
Type and origin Power type Steam Designer Oliver Bulleid Builder SR Eastleigh Works Build date 1941–1949 Total produced 30
Specifications Configuration: ​  • Whyte 4-6-2 (Pacific) Gauge Template:4ft8.5in Length 69 ft 8 in (21.85 m) Fuel type coal Fuel capacity 5 tons (5.1 tonnes) Water cap. 5,000 imp gal (22,730 L; 6,000 US gal) Boiler pressure 280 psi (1,931 kPa) Cylinders 3 Cylinder size 18 in × 24 in (416 mm × 610 mm)
Performance figures Tractive effort 37,513 lbf (166.86 kN)
Career Locale Great Britain

Horse feces

The SR Merchant Navy Class, also known as Bulleid Pacifics, Spam Cans or Packets, was a class of air-smoothed 4-6-2 Pacific steam locomotives designed for the Southern Railway of the United Kingdom by Oliver Bulleid. The Pacific design was chosen in preference to several others proposed by Bulleid. The first members of the class were constructed during the Second World War, and the last of the 30 locomotives in 1949.

Incorporating a number of new developments in British steam locomotive technology, the design of the Packets was among the first to use welding in the construction process; this enabled easier fabrication of components during the austerity of the war and post-war economies. The locomotives featured thermic syphons and Bulleid's controversial, innovative chain-driven valve gear. The class members were named after the Merchant Navy shipping lines involved in the Battle of the Atlantic, and latterly those which used Southampton Docks, an astute publicity masterstroke by the Southern Railway, which operated Southampton Docks during the period.

Due to problems with some of the more novel features of Bulleid's design, all members of the class were rebuilt by British Railways during the late 1950s, losing their air-smoothed casings in the process. The Packets operated until the end of Southern steam in July 1967. A third of the class has survived and can be seen on heritage railways throughout Great Britain.

Background

The gestation of the Merchant Navy Class Pacifics began in 1938, when Sir Eustace Missenden, the Director of the Southern Railway, realised that the company lagged behind in terms of pioneering locomotive design. Oliver Bulleid, who had been brought in from the LNER to replace Richard Maunsell as Chief Mechanical Engineer (CME) believed that it was time for the Southern to modernise the locomotive fleet. This was because the company's newest locomotive design was the 0-6-0 Q Class, influenced by Victorian design principles. Bulleid's first suggestion was for an eight-coupled locomotive with a 4-8-2 wheel arrangement, although this was quickly modified to a 2-8-2, equipped with a Helmholz "Bissel-Bogie" – a system already successfully applied on the Continent. The Bissel-Bogie comprised a pivoted frame, similar to that of a bogie, supporting a leading pair of carrying wheels and the front pair of driving wheels. In a curve, the radial movement of the carrying wheel was compensated by the leading coupled wheel sliding laterally over to the opposite side, hence reducing wear and improving ride quality. However, both proposals for eight-coupled locomotives were resisted by the Southern Railway's Chief Civil Engineer, so a new 4-6-2 Pacific design was settled upon instead. The new design was intended for express passenger and semi-fast work in Southern England, though it had to be equally adept at freight workings due to the nominal 'mixed traffic' classification Bulleid applied to the class for them to be built during wartime. Administrative measures had been put in place by the wartime government preventing the construction of express passenger locomotives due to shortages of materials and a need for locomotives with freight-hauling capabilities. Classifying a design as 'mixed traffic' neatly circumvented this restriction.

Design features

The distinctive Bulleid-Firth-Brown wheels, seen here on 35010 Blue Star. Note the balance weight on the lower right, a feature not present on the MNs as-built.

The Merchant Navy Class design was originally intended to use gear-driven valve gear, though space restrictions within the frames and wartime material shortages led Bulleid to design his novel chain-driven valve gear. This component was unique amongst British locomotive design practices. It gained a bad reputation because it could cause highly irregular valve events, a problem compounded by the fast-moving Bulleid steam reverser. The entire system was located in a sealed oil bath, another unique design, providing constant lubrication to the moving parts. Despite the benefits, its inaccessible location within the frames meant difficulties when things went wrong. A number of other features were unusual when compared to other contemporary designs. The inner firebox was constructed with Bulleid's revolutionary use of welding, as opposed to the rivetting that was more common practice. This made for cheaper construction and easier maintenance, whilst thermic syphons were implemented to improve water circulation between the boiler and the top of the firebox (the 'crown'). Maximum boiler pressure was higher than any other British regular service locomotive at 280 psi.

The boiler was enveloped by Bulleid's air-smoothed sheet steel casing, whilst the locomotive sat on the unusual Bulleid-Firth-Brown wheels, which were lighter, yet stronger than the spoked equivalent. The air-smoothed casing was not regarded as streamlining, demonstrated by the extremely flat front end, but as an aid to cleaning the locomotive with a carriage washer, representing another attempt to reduce labour during the post-war period. Electric lighting was also provided, supplied by a steam-powered generator fitted below the footplate. The tender could carry 4,500 imperial gallons (20,460 L; 5,400 US gal) of water and featured streamlined panels, or "raves", that gave the top of the tender a similar cross-sectional outline to the carriages hauled by the locomotive.

Close attention was paid to the ergonomics of the driving cab which was designed with the controls required for operation grouped according to the needs of both fireman and driver, thus promoting safe operation. As an aid to the fireman, a steam-operated treadle was provided that used steam pressure to open the firehole doors (where the coal is shovelled into the firebox). Modification was also made to the air-smoothed casing surrounding the smokebox after reports were made of drifting smoke obscuring the locomotive crew's vision ahead. Initially, the only form of smoke deflection was a narrow slot in front of the chimney, intended to enable air to lift the smoke when the locomotive was travelling. This proved inadequate because of the relatively soft exhaust blast that came from the multiple-jet blastpipe, which failed to be caught by the air flow. After several trials, the air flow was increased by extending the casing roof over the front of the smokebox to form a cowling whilst side smoke deflector plates were also incorporated into the front of the air-smoothed casing. The latter added to the poor visibility from the footplate and the expedients combined never fully solved the smoke drift problem.

During the brief time they operated under the Southern Railway, further modifications were applied to the class, such as the redesign of the footplate spectacle plates. These are the small windows on the front face of the cab, which were redesigned to an angled profile, a feature to be seen on all Bulleid-designed locomotives post-nationalisation. They had been introduced in Britain in 1934 with the Gresley-designed Cock o' the North. Originally, the spectacle plates of the Bulleid Pacifics were at the conventional right-angle to the direction of the locomotive, and offered limited vision ahead along the air-smoothed casing. The Southern-built batches also had variations in the material used for the air-smoothed casing with a change from sheet steel to an asbestos compound, forced upon the manufacturer by wartime expediency. This resulted in several class members having a horizontal strengthening rib running down the length of the casing.

Construction history

The Southern Railway initially constructed ten Packets at Eastleigh Works: the first to be completed in March 1941 was number 21C1 Channel Packet. A second batch followed, beginning in 1944 with 21C11 General Steam Navigation, and culminating with 21C19 French Line C.G.T. in September 1945. These were equipped with 5,100-imperial-gallon (23,190 L; 6,120 US gal) tenders. The final ten engines in the class were constructed after the nationalisation of the railways in 1948. This meant that they never carried Southern Railway numbers. The British Railways batch had detail differences to previous versions, the most significant being the tender, which had an increased water capacity of 6,000 imperial gallons (27,280 L; 7,210 US gal).

The Merchant Navy Class spawned the design and construction of the West Country and Battle of Britain Classes, from 1945, a lighter version of the same locomotive with consequently increased route availability. These were required for use on the Southern's "Withered Arm" west of Exeter, as the heavier Merchant Navy Class locomotives were banned from this section due to weight restrictions.

Naming the locomotives

Nameplate configuration of Merchant Navy (35005 Canadian Pacific)

The Southern Railway considered naming the locomotives after victories of the Second World War, to the extent that a mocked-up nameplate River Plate was produced. In the event, when early successes for the British proved few and far between, the chairman of the Union Castle Line suggested naming them after shipping companies which had called at Southampton Docks in peacetime. This idea resonated in 1941 because the shipping lines were heavily involved in the Atlantic convoys to and from Britain during the Second World War.

A new design of nameplate was created, featuring a circular plate with a smaller circle in the centre. The inner circle carried the colours of the shipping company on a stylised flag, on an air force blue background. Around the outer circle was the name of the locomotive, picked out in gilt lettering. A horizontal rectangular plate was attached to either side of the circular nameplate, with "Merchant Navy Class" in gilt lettering. This acted as a class plate, as indicated on the nameplate photograph, right.

During their operational career, the class gained several nicknames; the most obvious, Bulleid Pacific, simply denoted the designer and wheel arrangement. The colloquial name Spam Can arose from their utilitarian appearance, enhanced by the flat, boxy air-smoothed casing, and the resemblance of this to the distinctive tin cans in which SPAM was sold. The nickname Packets was also adopted by locomotive drivers, as the first member of the class was named Channel Packet.

British Railways engines

The final batch of ten locomotives constructed after the nationalisation of Britain's railways never carried a Southern Railway number. The British Railways standard numbering system placed this batch in the series 35021–35030, with all locomotives completed at Eastleigh between 1948–1949.

Rebuilding

BR Rebuilt Merchant Navy Class
Rebuilt 35024 East Asiatic Company at Exeter St Davids, 1962 with Atlantic Coast Express headboard.
Type and origin Power type Steam Designer R. G. Jarvis after Oliver Bulleid Builder SR Eastleigh Works Build date 1956–1960 Total produced 30
Specifications Configuration: ​  • Whyte 4-6-2 (Pacific) Gauge Template:4ft8.5in Length 71 ft 7 in (21.85 m) Fuel type coal Fuel capacity 5 tons (5.1 tonnes) Water cap. 6,000 imp gal (27,280 L; 7,210 US gal) Boiler pressure 250 psi (1,724 kPa) Cylinders 3 Cylinder size 18 in × 24 in (457 × 610 mm)
Performance figures Tractive effort 33,495 lbf (148.99 kN)
Career Locale Great Britain

Between 1956 and 1960, British Railways rebuilt the entire class to a more conventional design by R. G. Jarvis, adopting many features from the BR 'Standard' locomotive classes that had been introduced. The air-smoothed casing was removed and replaced with conventional boiler cladding, and the chain-driven valve gear was replaced with Walschaerts valve gear, whilst the boiler pressure was reduced from 280 to 250 psi. The first to be released from Eastleigh was 35018 British India Line in 1956. The final example, 35028 Clan Line, was completed in 1960. The rebuilt Merchant Navy Class was also to influence the design of the future rebuild of 60 Light Pacifics.

As a result of the implementation of Walschaerts valve gear, the rebuilts were prone to hammerblow on the track caused by the additional weights incorporated to balance the outside valve gear, an issue that had not arisen with the self-balanced arrangement of the original locomotives.

The rebuilt locomotives were scrapped relatively soon after their rebuilding; some engines such as 35014 Rotterdam Lloyd were withdrawn as early as 1964. The last few engines in traffic survived until the end of steam on the Southern Region in the summer of 1967.

Operational details

The utilisation of welded steel construction and several innovations that had not previously been seen in British locomotive design meant that the class earned Bulleid the title 'Last Giant of Steam'. The constant concern for ease of maintenance and utility had not previously been seen on locomotives of older design, whilst their highly efficient boilers represented the ultimate in British steam technology, the hallmark of a successful locomotive design. The locomotives were largely successful, though their heavier axle loading meant that they were banned from certain areas of the Southern Railway, and later, the British Railways Southern Region network. The locomotives were often prone to wheelslip, and required very careful driving when starting a heavy train from rest, but once into their stride they were noted for their free running, excellent steam production and being remarkably stable when hauling heavy expresses.

A perennial problem with the un-rebuilt Merchant Navy Class locomotives lay with the leaks from the oil bath onto the wheels that in turn splashed oil onto the boiler lagging in service. Once saturated with oil, the lagging attracted coal dust and ash which provided a combustible material, and as a result of the heavy braking of the locomotives, sparks would set the lagging on fire underneath the air-smoothed casing. The local fire brigade would invariably be called to put the fire out, with cold water coming into contact with the hot boiler, causing stress to the casings. Many photographs show an un-rebuilt with "cockled" (warped) casings, a result of a lagging fire.

The exhaust problem was never adequately resolved, and continued to beat down onto the air-smoothed casing when the engine was on the move, obscuring the driver's vision from the cab. The rebuilts were provided with LMS-style smoke deflectors and the lack of air-smoothed casing also helped reduce the problem.

Livery and numbering

Southern Railway

Livery was Southern Railway Malachite Green with Sunshine Yellow horizontal lining and lettering. All class members that operated during the Second World War were eventually repainted in Southern Railway Wartime Black livery, with green-shaded 'Sunshine' lettering. However, this was reverted back to Malachite Green livery upon the ending of hostilities.

21C1 Channel Packet originally had an inverted horseshoe on the smokebox door, indicating its Southern origin, however, locomotive crews believed this to be unlucky. A resultant re-design meant that this became a roundel, the gap being filled by the date and place of construction, therefore acting as a builder's plate. The background was painted red. Early members of the class had cast iron numberplates and gilt 'Southern' plates on the tender, however these were subsequently replaced by transfers.

Bulleid advocated a continental style of locomotive numbering, based upon his experiences at the French branch of Westinghouse Electric before the First World War, and those of his tenure in the rail operating department during that conflict. The Southern Railway numbers followed an adaptation of the UIC classification system where "2" and "1" refer to the number of unpowered leading and trailing axles respectively, and "C" refers to the number of driving axles – in this case three. All the locomotives of Pacific wheel arrangement therefore carried the prefix 21C, followed by the number in the group.

Post-1948 (nationalisation)

After nationalisation in 1948, the locomotives' initial livery was a slightly modified Southern Malachite Green livery, where "British Railways" replaced "Southern" in Sunshine Yellow lettering on the tender sides. The Bulleid numbering system was temporarily retained, with an additional "S" prefix, such as S21C1. The second livery carried was the British Railways Experimental Express Passenger Blue with red or white lining, and this was in use until 1952. From then on, the locomotives carried the standard British Railways Brunswick Green livery with orange and black lining and the British Railways crest on the tender tank sides. This standard livery was perpetuated after rebuilding. From 1949, the locomotives were renumbered under the British Railways standard system in the series 35001–35030.

Preservation

Many of the class have survived into preservation thanks to the unusual practice at Barry Scrapyard in South Wales, where steam engines bought from British Railways for scrapping were stored rather than immediately cut up. One engine, 35028 Clan Line, was bought by the Merchant Navy Locomotive Preservation Society direct from British Railways in 1967, and has since been regarded as the 'flagship' of the class. A third of the Packets have survived into the preservation era, although it is very likely that many will never steam again, with only three having been restored to working order thus far. This is because the class is too large and heavy for use on most of today's heritage railways. As the entire class was rebuilt from 1956 onwards, no Merchant Navy Class locomotives exist in as-built condition. Other relics of the class have survived in the guise of locomotive nameplates and smokebox number plates, which were taken from their locomotives towards the end of steam on the British Railways Southern Region in the 1960s. As a result, many exist in private collections, and several have been seen at auction, selling for several thousands of pounds.

Preserved Merchant Navy Class locomotives

Number 35010 Blue Star on Static display awaiting restoration at the Colne Valley Railway

• 35005 Canadian Pacific, Watercress Line (Mid-Hants Railway)
• 35006 Peninsular & Oriental S. N. Co., Gloucestershire Warwickshire Railway
• 35009 Shaw Savill, Watercress Line (Mid-Hants Railway)
• 35010 Blue Star, British Enginemen's Steam Preservation Society, Colne Valley Railway
• 35011 General Steam Navigation, RAF Binbrook
• 35018 British India Line, South Coast Steam, Portland
• 35022 Holland-America Line, Southall, London
• 35025 Brocklebank Line, soon to be moved to Southern Locomotives Ltd. base at Sellindge, Kent
• 35027 Port Line, (Sold 2003 for private ownership) Stored pending overhaul at Southall, London
• 35028 Clan Line, Stewarts Lane, London
• 35029 Ellerman Lines, National Railway Museum (sectioned to show internal workings of a steam locomotive)

For location details of the preserved locomotives, see: List of SR Merchant Navy Class locomotives

References

• Bulleid, H. A. V.: Bulleid of the Southern (Hinckley: Ian Allan Publishing, 1977) ISBN 071100689X
• Bulleids in Retrospect, Transport Video Publishing, Wheathampstead, Hertfordshire
• Burridge, Frank: Nameplates of the Big Four (Oxford Publishing Company: Oxford, 1975) ISBN 0902888439
• Creer, S & Morrison, B: The Power of the Bulleid Pacifics (Oxford Publishing Company: Oxford, 2001) ISBN 0860930823
• Chapelon, A : La Locomotive à Vapeur (English ed., transl. Carpenter George W.); Camden Miniature Steam Services, Somerset U.K. (2000) ISBN 0953652300
• Day-Lewis, S: Bulleid, Last Giant of Steam (London: George Allen & Unwin, 1964) P. 186
• Harvey, R. J.: Bulleid 4-6-2 Merchant Navy Class (Locomotives in Detail series volume 1) (Hinckley: Ian Allan Publishing, 2004), ISBN 0711030138
• Herring, Peter: Classic British Steam Locomotives (Abbeydale Press: London, 2000) Section "Merchant Navy Class" ISBN 1861470576
• Hicks, Bryan: 'A Southern Calling' Part Two (Steam World: 244, October 2007)
• Ian Allan ABC of British Railways Locomotives, winter 1958–59 edition
• Morgan, John Scott: The Story of the Q1s (KRB Publications: Bishop's Waltham, 2003) ISBN 0954485912
• The Railway Magazine (January, 2007)

Further reading

• Ian Allan ABC of British Railways Locomotives, winter 1962–63 edition
• Morrison, B: The Power of the Merchant Navies (Oxford Publishing Company: Oxford, 2007) ISBN 0860936074
• Reed, B: “Merchant Navy Pacifics” Loco Profile series 22, page 231 (Profile publications, Berkshire, England, 1972)

See also

• List of SR Merchant Navy Class locomotives

External links

• Bulleid Society–Merchant Navy information
• Southern e-group–Merchant Navy information