LSWR S15 class

During the First World War, the LSWR management wished to address the requirement for a modern, standard heavy freight locomotive to work from London's freight yards to the southwest of England. Robert Urie used this opportunity to develop his recent H15 class design further, applying the 4-6-0 locomotive concept to a purpose-built freight design built to order number S15. It was this order number that gave the class the name "S15". == Construction history ==

The S15 class were all built by Eastleigh Works in three discrete batches between February 1920 and December 1936. First batch – Urie 1920–21 This was the third design by Robert Urie for the LSWR. The outline was made during the First World War, and incorporated lessons learned from the operation of his H15 class, a design that was to provide the basis for future standardisation on the LSWR. To economise on maintenance, the S15 class had interchangeable components that could be used on a similar design, the N15 class passenger locomotive, which had the same overall appearance. The only other major difference was the smaller diameter of the driving wheels. Smaller diameter wheels gave better traction, essential for a fast freight locomotive. When the modifications were trialled in service, it became evident amongst locomotive crews that Maunsell had taken a sound design and made it better, achieving a consistent locomotive capable of undertaking all the tasks for which it was intended. Second batch – Maunsell 1927–28 Maunsell's modifications included increasing the boiler pressure from to , and the reduction of the cylinder bore by half an inch. The footplate was also modified for operation on the Southern's new composite loading gauge, and differed from previous batches in having the Ashford-style cab, which was usually fitted to LBSCR locomotives. Fifteen locomotives of this revised design were built in 1927, and some were given six-wheeled tenders for use on the Southern Railway's Central section. The standardisation measures undertaken by both Urie and Maunsell were soon vindicated by the fact that tenders and other parts were swapped with those of other classes on the Southern Railway when locomotives were under overhaul. This modification was a feature that became common to most Maunsell-influenced designs. == Operational details ==

After modification by Maunsell, the S15 class was regarded by locomotive crews as an excellent goods engine best known for working heavy night express goods trains between Exeter, Southampton and Nine Elms. The S15s were also very capable passenger engines, being able to deputise in situations where there was a shortage of passenger locomotives during peak holiday periods. In order to increase maintenance efficiency, all Urie S15 locomotives (which had the lower boiler pressure) were concentrated at the Southern Railway's London freight depot at Feltham. This yard also featured the Maunsell S15s, which were allocated to Exmouth Junction, Hither Green and Salisbury, demonstrating the "go anywhere" nature of the class. Despite the design being only a year newer, the S15s outlasted their N15 King Arthur class counterparts because of their dual freight/passenger abilities, though they were retired between 1962 and 1966 as part of the British Railways Modernisation Plan. Maunsell S15 number 30837 became the final member of the class in operation, returning to Feltham in January 1966 to work a farewell rail tour. ==Accidents and incidents==

• In the summer of 1946, locomotive No. 502 was hauling a freight train that overran signals and was derailed by trap points at Wallers Ash, Hampshire. == Preservation ==

Seven S15s have been preserved, two Urie examples and five by Maunsell, which can be seen at several heritage railways around the country. All the surviving members of the class were purchased from Woodham Brothers scrapyard in Barry, Vale of Glamorgan, South Wales. Currently only 499 and 830 have yet to steam in preservation. Of the five others that have run in preservation 825, 828 and 841 have all operated on the main line at certain points, though 825 has only run between Grosmont & Whitby. == Livery and numbering ==

LSWR and Southern Railway Under LSWR ownership, the S15s were painted in the late LSWR dark Holly Green livery, with the same black and light green lining applied to most of the LSWR's freight designs. Gilt lettering and numbering was located on the tender and cabside respectively. The initials "LSWR" were located on the tender. The first Southern Railway livery continued that of the LSWR, but with the number displayed on the tender. However from 1925, a darker Olive-type green was substituted, and the entire class was so painted. Nos. 496–515 were built between 1919 and 1921, and Nos. 823–837 were delivered from Eastleigh during 1927 and 1928 and a further 10 locomotives, No.838–847, were authorised in 1931. British Railways After a period in British Railways transitional livery the entire class was painted in British Railways Goods Black livery with no lining, the numbering located on the cab-sides and the British Railways crest on the tender sides. Numbering was initially as per Southern Railway with an "S" prefix, but the locomotives were eventually re-numbered under the British Railways standard numbering system according to batch. They were numbered in the series of 30496–30515 for the Urie locomotives, 30823–30837 for the second batch, and 30838–30847 for the third batch. ==References==