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TheSR class LN orLord Nelson class is a type of 4-cylinder4-6-0 steam locomotive designed for theSouthern Railway byRichard Maunsell in 1926. They were intended for Continental boat trains betweenLondon (Victoria) andDover harbour, but were also later used for express passenger work to the South-West of England. Sixteen of them were constructed, representing the most powerful (although not the most successful) Southern4-6-0 design. They were all named after famous admirals.[2]
The class continued to operate withBritish Railways until withdrawn during 1961 and 1962. Only one example of the class – the first engine,Lord Nelson itself – has been saved from scrapping. This has been seen running on mainline tours and preserved railways throughout Britain.
Although the improved”King Arthur" class 4-6-0 locomotives were capable of the heaviest expresspassenger work between London andSouth West England, there was a growth in demand for Continental traffic travelling viaDover andFolkestone. By the mid-1920s the Southern Railway Traffic Department wished to begin operating 500-long-ton (510 t; 560-short-ton) express trains on these routes during peak periods. These would require a more powerful locomotive, able to pull heavier loads at sustained speeds of 55 mph (89 km/h), so as not to impede the congested electrified lines around London. However, any enlargement of the existing 2-cylinder design was not possible due to weight restrictions imposed by the railway'sCivil Engineer.[3][4][5]
After examining the practice of other British railways, Richard Maunsell, theChief Mechanical Engineer, secured agreement for a 4-cylinder design, with an improvedboiler andBelpaire firebox. The drive would bedivided between the front coupled axle for the inside cylinders and the middle coupled axle for the outside cylinders giving better weight distribution and reducedhammer blow.[6] The new design was an inevitable compromise between the need for additional power and to keep the weight down to an acceptable limit.[citation needed]
There were two unusual features of the design: the first of which was the setting of the crank axles at 135°, rather than the standard 90° of other locomotive types. This design necessitated four sets of valve gear, and gave rise to eight beats per revolution, rather than the usual four, designed to give a more even draw on the fire and less chance of wheelslip when starting. The second difference was that fire grate was in two sections, the rear portion was horizontal and the front sloped away sharply.[7]
The prototype E850 namedLord Nelson was ordered fromEastleigh railway works in June 1925 but production proceeded slowly, at Maunsell's insistence, to ensure that the weight was kept to a minimum at every stage,[8] so the locomotive did not appear until August 1926. It was tested on a variety of duties over the next year, with sufficiently encouraging results for an initial order for ten more locomotives for delivery between May 1928 and April 1929 to be placed.[7] These were originally scheduled to be allocated toBattersea depot and fitted with 4,000 gallon 6-wheeled tenders suitable for the Continental ports. However, during construction, it was decided to equip half of the class with 5,000 gallon 8-wheeled tenders necessary for the longer West of England routes and to allocate them toNine Elms depot. A further batch of ten locomotives was ordered in 1928, before the previous batch had been delivered, but when it became apparent that theStock Market crash of 1929 would be likely to reduce the demand for Continental travel, this second order was reduced to five.[9]
The locomotives were all named after famousRoyal Navyadmirals, with the first of the class being namedLord Nelson. As a result, the rest of the locomotives belonged to theLord Nelson (LN) class.[10]
The performance of the new locomotives was mixed, depending upon the experience of the crew and the circumstances under which they were operating. At times it was no better than their smaller predecessors. Maunsell therefore undertook a number of experiments to try to improve the performance of the new locomotives. No. E859 was fitted with smaller 6 ft 3 in (1.905 m) driving wheels to see if this would improve performance over the heavily graded London-Dover line, but the difference was marginal. No. E860 was fitted with a longer, heavierboiler but once again with little improvement. The whole class however benefitted from the fitting ofsmoke deflectors during the late 1920s.[citation needed]
Maunsell was aware of the reputation for poor steaming enjoyed by the class and attempted to address it by the fitting of twinKylchapblastpipes to No. 860 in 1934.[11] However, the problem was ultimately solved byOliver Bulleid, Maunsell's replacement as Chief Mechanical Engineer of the Southern in 1938. He fitted larger diameter chimneys andLemaître multiple jetblastpipes, which effectively transformed their performance.[1] Thereafter the class was highly respected.[citation needed]
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For a period after its introduction to the Southern Railway network, theLord Nelson class held the title of "most powerful locomotive in Britain" – a claim based on itstractive effort.[12] The advanced design of the locomotive led to theGWR introducing theGWR 6000 Class in order to regain the title lost by theirGWR 4073 Class locomotives when theLord Nelsons were constructed.[1] The planned 500-ton trains never materialised, but the class was regularly used on 460 ton trains such as theGolden Arrow. After theSecond World War they were also frequently used on heavily laden Boat Trains betweenLondon Waterloo station andSouthampton docks.[13]
TheLord Nelsons were notoriously difficult for inexperienced crews to fire properly, due to their long firebox,[14] and specific crews who had proven experience in firing the locomotives were therefore allocated to them.[15] This was due to the relatively few locomotives in the class for crews to train on.[12] TheLMSRoyal Scot Class was loosely based on this design.[16]
The class was gradually superseded on top link expresses during the 1940s by growing numbers ofBulleid Pacifics,[12] although throughout the 1950s they were frequently called upon during peak periods or to deputise for failures.[22][page needed] The rebuilding of thePacifics in the late 1950s and their subsequent increased reliability rendered theLord Nelson surplus to operational requirements, and they were gradually phased out of service.[23] The entire class was withdrawn during 1961 and 1962.[1]
The Lord Nelson class was initially painted in Maunsell lined olive green, which later changed to a lighter shade in the mid-1930s. From 1938, some of the locomotives were painted in a semi-matt Malachite Green finish when Bulleid replaced Maunsell as CME of the Southern. During the war years, the locomotives were painted in wartime black livery, though retained the word "Southern" in yellow on the tender.[24] After the war, the livery was reverted to the Southern Railway Malachite Green standard with "Sunshine Yellow" lining on the boiler rings.[citation needed]
Numbers allocated to the locomotives were a variation ofLSWR practice and, being constructed at Eastleigh, were given the prefix "E" before the number to distinguish from the locomotives of other pre-grouping railway companies that also carried the same number.[25] In the case of theLord Nelson class the numbering ranged from E850 to E865. This was eventually superseded by numbers without the "E" prefix, becoming 850 to 865 from 1931.[26]
The initial livery applied following thenationalisation of the railways in 1948 was modified Southern malachite green and sunshine yellow with "British Railways" on the tender, and the Southern numbering system was temporarily retained with an "S" prefix (such as S850) until superseded by the British Railways numbering system.[27] The locomotives then carried British Railways Brunswick green livery with orange and black lining.[28] By this stage the locomotives were renumbered under standard British Railways procedure, from 30850 to 30865.[29]
The first engine built,(30)850Lord Nelson, has been preserved as part of theNational Railway Collection and has run on the national rail network.[30][31] As of 2020 it is based on theMid-Hants Railway. Its boiler certificate expired in 2015. It is now stored awaiting overhaul.[32]
