SECR K and SR K1 Classes - Background

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 London Charing Cross 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. This resulted in frequent double-heading, adding to operational costs.

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. 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. 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.