The SECR K class was a type of 2-6-4 tank locomotive designed in 1914 by Richard Maunsell for express passenger duties on the South Eastern and Chatham Railway (SECR), which operated between London and south-east England. The Southern Railway (SR) K1 class was a three-cylinder variant of the K class, designed in 1925 to suit a narrower loading gauge. They were among the first non-Great Western Railway (GWR) types to use and improve upon the basic design principles of power and standardisation established by GWR Chief Mechanical Engineer (CME) George Jackson Churchward. The locomotives were based on the GWR 4300 class, improved by the Midland Railway's ideals of simplicity and ease of maintenance.Scott-Morgan (2002), p. 18
The K class was designed to be mechanically similar to the SECR N class 2-6-0 mixed-traffic locomotives. The class was one of the earliest to use the 2-6-4 wheel arrangement in Britain.Casserley (1966), p. 436 Production began towards the end of the First World War, and the prototype rolled out of Ashford Works three years after design work was completed due to wartime production constraints. The class replaced obsolete 4-4-0 passenger locomotives in an SECR fleet standardisation programme.
Twenty-one locomotives were built: twenty K class (two cylinders) and one K1 class (three cylinders), the first in 1917 and the remainder between 1925 and 1926. They operated over the Eastern section of the Southern Railway network and were given the names of rivers, being referred as the River class from 1925. Crews referred to the K and K1 classes as "Rolling Rivers" because of their instability when travelling at speed. They were rebuilt as 2-cylinder SR U class and 3-cylinder SR U1 class 2-6-0s (respectively) following a railway accident at Sevenoaks, Kent in 1927. They continued in service with British Railways (BR) until the last was withdrawn in 1966. One K class rebuild (No. 31806) used to be preserved on the Mid Hants Railway, but since 2014, it is now preserved on the Swanage Railway in Dorset and still operational today.
Background Three factors dictated the type of locomotive that could operate on the South Eastern and Chatham Railway (SECR): the heavy passenger train loadings; the poor track quality; and the weak, lightly built bridges. On the lines of the former London, Chatham and Dover Railway (LCDR) – inherited by the SECR in 1899 – beach pebbles had been used for ballast instead of conventional ballast, which has irregular shapes that lock together to keep the track in place. These economies in construction meant that only locomotives with low axle loadings could operate safely over the track. The SECR was therefore unable to follow a coherent strategy to reduce the number of locomotive types inherited from the two constituent railways. Despite increased passenger and freight traffic between and the Kentish coast during the first decades of the 20th century, the Operating Department had to use mismatched classes of underpowered and obsolete 4-4-0 and 0-6-0 locomotives, which could operate within the restrictions imposed by the infrastructure.Whitehouse & Thomas (2002), p. 50 This resulted in frequent double-heading, adding to operational costs.Whitehouse & Thomas (2002), p. 51
Richard Maunsell was appointed CME of the SECR in 1913, following the enforced retirement of Harry Wainwright, who had left a range of competent but unspectacular locomotive classes that struggled to cope with the increased train lengths and loadings.Whitehouse & Thomas (2002), p. 49 Maunsell reviewed the situation and planned to introduce six standard classes – using only two boiler designs – which would work the entire traffic of the railway.Bradley (1980), pp. 66–67 The first of these was the N class 2-6-0, which gave the SECR a capable mixed-traffic locomotive. For the express passenger design that could cope with the heavy boat trains, Maunsell wanted to enlarge the existing L class 4-4-0 with Walschaerts valve gear and an enlarged superheater, but this design would have resulted in a too heavy axle loading. Maunsell's newly recruited assistants, G.H. Pearson and Harold Holcroft from the Great Western Railway at Swindon and James Clayton from the Midland Railway at Derby, had recently been involved in the design of large passenger tank engines and persuaded him to use the 2-6-4 wheel arrangement, which would allow the class to operate at high speeds on the poor-quality track in north Kent.
Design and construction The 2-6-4 wheel arrangement was not in common use in Great Britain at this time, as many railway companies operated routes that required locomotives with greater fuel capacity, or short branch lines that necessitated smaller locomotives. The 2-6-4 tank engine design had only been used once before for standard gauge locomotives in Britain, on the Great Central Railway's 1B class freight locomotives of 1914.Bradley (1961), p. 52 However, the configuration was ideal for the SECR, because of its shorter mainlines, and allowed for a long wheelbase with a leading axle to permit greater stability at speed on track curves. The tightness of the curves on the former LCDR mainlines had constrained the size of locomotives operating on the SECR, as they had been hastily erected during the nineteenth century to compete with those of the South Eastern Railway (SER). The longer locomotive could also accommodate a larger boiler than a 4-4-0, giving sufficient power to avoid double-heading of locomotives on heavier trains.
The K class design used a "Bissel bogie" leading axle and a plain trailing bogie. The trailing bogie permitted the use of a large coal bunker that was capable of sustaining the locomotive over the run between London Charing Cross and , and side water tanks of capacity were used, negating the need for a tender. The coupled wheelbase between the rear and centre driving wheels was reduced from that used on the mechanically identical N class to to accommodate the bogie.Bradley (1961), p. 53 The cab was fully enclosed, although the set of four small front spectacle plates (the windows on the front face of the cab for forward visibility) were the same as those used on the N class.
The K class was designed by Maunsell's team in 1914 as part of his proposed standardisation programme following the N class, but the designs were not shown to the railway directors until early 1915 to enable all six designs to be shown at once. The design incorporated the principles of power and reliability established by George Churchward, using a Belpaire firebox that sloped downwards towards the cab instead of a round-topped version, a regulator located in the smokebox, long-travel valves for free running at high speeds, a sharply tapered and domeless boiler, and a right-hand driving position.Middlemass (1990), pp. 148–154 The inclusion of these features is attributed to Holcroft, Maunsell's personal assistant, who had worked on the GWR 4300 class and the N class.Haresnape (1983), pp. 34–36 James Clayton, Maunsell's Chief Locomotive Draughtsman, brought simpler and more functional Midland Railway influences to the design, such as the shape of the cab and the drumhead-type smokebox, which sat on a saddle that was of wider diameter than the fully lagged and clad boiler.Rowledge (1976), p. 8 The latter was fitted with Ross pop safety valves and pressed to .
Other innovations by Maunsell's team included greater superheating surface area, locating the boiler water top feed inside a dome-like cover with external clackboxes and water feed pipes mounted on either side, outside Walschaerts valve gear, and parts that could be shared with similar locomotive classes to reduce maintenance costs.Clarke (February 2008), p. 38 The firebox was narrower towards the rear and featured a continuously sloping grate, whilst the ashpan was fitted with front and rear damper doors, the latter adjusted to clear the rear driving axle. The lower part of the coal bunker incorporated a water tank of capacity. This was connected to two side tanks by two rectangular pipes on either side of the locomotive that also formed supports for the cab footplate.Rowledge (1976), p. 10
K class In January 1915 Maunsell received authority to build six examples, but, as with the N class, production was delayed due to the use of the Ashford works for wartime armaments manufacture. Assembly began in 1917 and the first, No. 790, emerged in July of that year. It was based at Bricklayers Arms depot,Bradley (1980), p. 69 preceding the earlier N class design into service by one month.Railway Engineer (1923), pp. 140–143 Further construction was deferred until after Ashford had caught up with the maintenance backlog caused by the war.
Ten more locomotives were ordered by the SECR from Ashford works in June 1920, and to speed delivery the construction of frames, cylinders and side tanks was subcontracted to the Royal Arsenal at Woolwich. However, further severe delays at Ashford caused by the backlog of repair work meant that the boilers had to be supplied by the North British Locomotive Company.Bradley (1980), p. 70 Construction of these locomotives had not begun by 1 January 1923, when the Railways Act 1921 merged the SECR with other railways in southern England to form the Southern Railway.
Maunsell was appointed CME of the newly formed Southern Railway in 1923, and inherited the 1920 SECR order for ten K class locomotives. The order was still outstanding in 1924, although most of the component parts had been made. On 14 January 1925, Maunsell ordered No. 790 to be overhauled and trialled on the Central section.Holcroft (1965), pp. 145–147 As the locomotive proved suitable for the operating conditions of this section, the Southern Railway's Locomotive Committee proceeded with the assembly of the K class parts using outside contractors.Bradley (1980), p. 116 Nine sets of parts (Nos. A791–A799) were conveyed to Armstrong Whitworth for assembly and the finished locomotives delivered in May and June 1925. These were dual-fitted with vacuum and Westinghouse (air) brakes for use with the former London, Brighton and South Coast Railway (LBSCR) rolling stock on the Central section. Other differences from the prototype included the relocation of the regulator to the dome and an increase in superheater area. The tenth set of parts was retained by Ashford and used for the first member of the K1 class later that year.
In May 1925 Maunsell ordered a further ten locomotives from Brighton works (Nos. A800–A809), which only had vacuum brakes for the SECR stock on the Eastern section. They were delivered between July and December 1926. This group had modified suspension on the bogie and leading axle, in an attempt to address complaints from the crews of rough riding experienced with earlier members of the class. A further 20 members of the class were ordered in March 1926 (ten each from Ashford and Brighton works), despite strong reservations expressed by the Operating Department concerning "the wisdom or desirability of placing so many large passenger tanks in service".Bradley (1980), p. 71 These were allocated the numbers A610–A629, and work had begun on building the frames and cylinders when the order was cancelled following an accident at Sevenoaks in 1927 involving locomotive No. A800. These numbers were later allocated to the first production batch of U class locomotives.
K1 class