SECR K and SR K1 classes

SECR K & SR K1 (River) classes
The prototype K class No. 790 (later named River Avon) under SECR ownership. The class was eventually named after various rivers found within the Southern Railway's operating area in 1925
Type and origin Power type Steam Designer Richard Maunsell Builder K: Ashford Works (1), Brighton Works (10), Armstrong Whitworth (9) K1: Ashford Works (1) Build date 1917, 1925–1926 Total produced K: 20 K1: 1 Rebuilder Ashford Works (797–802, 805, 890) Brighton Works (803–804, 806–809) Eastleigh Works (790–796) Rebuild date 1928 Number rebuilt 21
Specifications Configuration: ​  • Whyte 2-6-4T Gauge 4 ft 8+1⁄2 in (1,435 mm) Wheelbase 35 ft 10 in (10.92 m) Length 43 ft 6+1⁄4 in (13.27 m) Height 12 ft 11+3⁄8 in (3.95 m) Axle load K: 18.50 long tons (18.80 t) Adhesive weight K: 52.75 long tons (53.60 t) Fuel type Coal Fuel capacity 2.50 long tons (2.54 t) Water cap. 2,000 imp gal (9,100 L; 2,400 US gal) Boiler pressure 200 psi (1.38 MPa) Cylinders K: Two, outside K1: Three Cylinder size K:19 in × 28 in (483 mm × 711 mm) K1: 16 in × 28 in (406 mm × 711 mm) Valve gear K: Walscharts K1-outside: Walschaerts inside: Holcroft
Performance figures Tractive effort K: 23,866 lbf (106.2 kN)
Career Power class SR: A Number in class 21 Official name River class Nicknames Rolling Rivers Locale Great Britain Withdrawn 1927 Disposition All rebuilt to SR U class or SR U1 class 1 rebuild surviving

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). The Southern Railway (SR) K1 class was a three-cylinder variant of the K class, designed in 1925 to suit a narrower loading gauge. Both classes were built between 1917 and 1925, and were among the first non-Great Western Railway (GWR) types to use and improve upon the basic design principles established by GWR Chief Mechanical Engineer (CME) George Jackson Churchward. The K class was based on the GWR 4300 class, improved with Midland Railway concepts.

The K class was mechanically similar to the contemporary SECR N class 2-6-0 mixed-traffic locomotives and influenced future 2-6-4 development in Britain. The class was the earliest large-scale use of the 2-6-4 wheel arrangement in Britain. Production began towards the end of the First World War, and the first K class rolled out of Ashford Works in 1917, three years after design work was completed. The class replaced obsolete 4-4-0 passenger locomotives as part of the SECR's fleet standardisation.

Twenty-one K and K1 class locomotives were built between the First and Second World Wars. They operated over the Eastern section of the Southern Railway network and were were given the names of various 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. Both classes were rebuilt as SR U class and SR U1 class 2-6-0s (respectively) following the 1927 Sevenoaks railway accident. They continued in service with British Railways (BR) until the last was withdrawn in 1966. One K class rebuild is preserved on the Watercress Line in Hampshire and is currently under overhaul.

Background

Three factors dictated the type of locomotive that could operate specifically on the South Eastern and Chatham Railway (SECR): the heavy passenger train loadings, poor track quality, and weak, lightly-built bridges. An increasing number of passengers used the SECR to reach the ferries crossing the English Channel at Dover and Folkestone, stretching the capabilities of existing infrastructure. 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. Conventional track ballast has irregular shapes that "lock" together to keep the track in place, whereas the smooth pebbles used by the LCDR failed to prevent track movement under strain. The economies in construction meant that only locomotives with low axle loadings could operate safely over the track. These restrictions meant that the SECR was unable to follow a coherent locomotive strategy that reduced costs and increased locomotive serviceability. The railway’s Operating Department had to use mismatched classes of underpowered and obsolete 4-4-0 and 0-6-0 locomotives because they could operate within the restrictions imposed by the infrastructure. The Department also contended with increased passenger and freight traffic between London and the Kentish coast, with frequent double-heading adding to operational costs.

Richard Maunsell was appointed CME of the SECR in 1913, following the retirement of Harry Wainwright due to ill health. Wainwright left a legacy of competent but unspectacular locomotives that struggled to cope with the increased train lengths and loadings. Maunsell had taken stock of the situation by designing the N class 2-6-0, which gave the SECR a capable mixed-traffic locomotive. There was still a requirement to progressively replace obsolete passenger engines with designs that could cope with the heavy boat trains. New designs had to take the aforementioned infrastructure restrictions into account whilst improving on previous performance. The response to the criteria was to become Maunsell's K class 2-6-4 tank engine.

Design and construction

The K class was designed by Maunsell in 1914 to provide a modern express passenger locomotive that could be used on the main lines of Kent. Intended to replace several obsolete 4-4-0 types, the K class was the second step in the SECR's standardisation programme. Maunsell enlisted the help of former GWR engineer Harold Holcroft to design a tank locomotive with 2-6-4 wheel arrangement that would allow the class to operate at high speeds on the poor-quality track in north Kent.

The 2-6-4 concept was not in common use at this time, as other locomotive designs worked on the suburban railways for which the type was to become synonymous. The 2-6-4 wheel arrangement allowed for a longer wheelbase with leading axle to permit greater stability at speed on track curves, which had constrained the size of locomotives operating on the SECR. A longer locomotive could also accommodate a larger boiler than a 4-4-0, giving the K class sufficient power to avoid double-heading of locomotives on heavier trains. The trailing bogie permitted the use of a large coal bunker that was capable of sustaining the locomotive over the run between London and Dover, and side water tanks of 2,000 imp gal (9,100 L; 2,400 US gal) capacity were used, negating the need for a tender.

The K class incorporated Churchward design principles, and included the use of a Belpaire firebox instead of a round-topped version, long-travel valves for free running at high speeds, a sharply tapered boiler, and a right-hand driving position. These features are attributed to Holcroft, who had worked on the GWR 4300 class and the N class.

Another of Maunsell's assistants, James Clayton, brought simpler and more functional Midland Railway influences to the design such as the shape of the cab. Innovations added by Maunsell's team included greater superheating surface area, the location of the boiler water top feed inside a dome-like cover, outside Walschaerts valve gear, and parts that could be shared with similar locomotive classes to reduce maintenance costs.

K class locomotives

As with the N class, production of the K class was delayed by the outbreak of the First World War. Assembly began towards the end of the war and the first, No. 790, emerged from Ashford Works in August 1917, preceding the earlier N class design into service by one month. Following entry into traffic on the SECR, No. 810 was trialled for defects, and no more class members were constructed until 1925. The newly formed Southern Railway ordered a batch of 19 K class locomotives eight years after the prototype entered service. Construction was divided between Armstrong Whitworth (Nos. A791–A799), and Brighton railway works (Nos. A800–A809), making a class total of 20 locomotives.

K1 class

To increase the route availability of the K class, the Southern Railway authorised the construction of a 21st 2-6-4 tank at Ashford works with a revised cylinder arrangement in 1925. The modifications to the cylinder arrangement was based upon those given to N class No. 822 in 1922. This engine was given smaller-diameter "outside" cylinders and a new "inside" cylinder during construction to create the prototype three-cylinder SR N1 class 2-6-0, which could work on routes with restricted loading gauge. This locomotive used Holcroft’s compact variant of the Gresley conjugated valve gear to drive the "inside" cylinder. The new 2-6-4 was classified K1 and used the same valve gear, allowing it to meet the route availability specification.

The main visual difference between the K and K1 classes was at the front end. A slab-front was incorporated above the front buffer beam to house the third cylinder and associated valve gear assembly. Otherwise, the K1 retained the 6 ft (1.83 m) driving wheels and general layout of the K class, and emerged from Ashford works as No. A890. The new locomotive underwent trials before entering regular service in December 1925.

Naming the locomotives

The prototype operated without a name until 1925, when the Southern Railway’s publicity department decided to name all express passenger locomotives. The locomotives constructed in 1925 were named after various rivers within the Southern Railway’s operating area, and the class became known collectively as the River class. The first-completed Southern Railway K class No. A791 was named River Adur whilst the former SECR prototype was given the name River Avon. The K1 class locomotive also had a name in the river theme, becoming No. A890 River Frome.

K and K1 class Construction History

Year	Batch	Quantity	SECR/SR numbers	Notes
1917	SECR	1	790
1925	SR	19	A791–A809	Class was named when this batch was under construction
1925	SR	1	A890	Prototype three-cylinder K1 class. No more K and K1 class locomotives built

Rebuilding

For a detailed examination of the K and K1 classes in rebuilt form, see: SR U class and SR U1 class.

When in service, the K and K1 classes suffered from stability problems when travelling at speed over points and curves. This culminated in the serious derailment of No. A800 River Cray at Sevenoaks, Kent, caused by a combination of a water surge in the tanks and poor quality track-work. The locomotive was hauling a Cannon Street to Deal express with a Pullman carriage when it derailed in a cutting and hit a road bridge, killing 13 passengers. The locomotive crew survived, and the K class was trialled on the Great Eastern mainline following the accident, which found few problems with locomotive stability on well-kept track. The management of the Southern Railway decided not to take any further risks with the class, and recommended the class be withdrawn from service. Withdrawals came before the results of the trials were published, and the engines were rebuilt to Maunsell’s new SR U class 2-6-0 tender engine design in 1928.

The rebuilding of locomotives was cheaper than relaying track, and the 2-6-4 wheel arrangement was no longer used for passenger locomotives by the Southern Railway. The only later use of the type was on the SR W class tank locomotives, which were restricted to freight operations around London. Rebuilding took place at Ashford, Brighton and Eastleigh railway works between March and December 1928, where the side water tanks, rear bogie and coal bunker were removed. The straight-sided 3,500 imperial gallons (15,911 L) variety of Maunsell tender was attached, allowing a greater operational range for the locomotives. The solitary K1 class locomotive became the three-cylinder SR U1 class prototype following similar conversion.

Operational details and perservation

For location details and current status of the preserved (rebuilt) locomotive, see: List of K and K1 class locomotives.

When rebuilt, the K class was incorporated into the U class. This is one of the rebuilds in British Railways service, No.31803 at Bournemouth. As K class locomotive No. A803, it was named River Itchen

The K class proved successful on well-maintained track, as evidenced by the trials undertaken on the Great Eastern mainline. The class was capable of high speeds on express passenger duties, although the success was limited by the low storage capacity of tank locomotives, which meant the K and K1 classes were prone to water shortages on the long Kent Coast routes, and precluded them from working on the former London and South Western Railway (LSWR) routes west of London. On the Southern Railway's Eastern section, crews complained that the locomotives rolled heavily and unpredictably on the cheaply-laid track of the former SECR network, leading to their nickname, "Rolling Rivers". The K1 locomotive was noted for particularly poor riding characteristics, as it derailed twice between 1925 and 1927.

When rebuilt to the new U/U1 tender engine designs in 1928, the K and K1 classes continued to serve the Southern Railway, and were capable of attaining speeds in excess of 70 mph (110 km/h). The rebuilds were used all over the network, but were little-used over the steep track gradients west of Exeter. This was because the smaller-wheeled N class was popular amongst crews, as high-speed running was rare away from the main lines in the West Country. Heavier passenger work was allocated to Bulleid’s Unrebuilt Light Pacifics, which were within weight restrictions in this area.

The 21 rebuilt locomotives entered British Railways service in 1948 and from 1955, a few members of the rebuilds were given replacement locomotive frames at overhaul, which had a shallower curve between the front buffer beam and smokebox. As members of the U and U1 classes, rebuilds represented one of the more unglamorous classes of passenger locomotive due to the fact that they were used mainly on mixed-traffic as well as secondary passenger duties between mainlines.

Withdrawals took place between 1962 and 1966, by which time the class was congregated around Guildford. Work was taken over by Oliver Bulleid’s Light Pacifics, and the electrification of much of the former Southern Railway network was imminent, making all the 2-6-0s surplus to requirements from 1963. The final rebuild was withdrawn from service in June 1966. One K class rebuild has survived: No. A806 River Torridge was converted to U class No. 1806, which was rescued from Woodham Brothers scrap yard in Barry, Vale of Glamorgan, South Wales in October 1976 for use on the Watercress Line. It was restored to ex-British Railways condition as No. 31806 and is currently under overhaul.

Livery and numbering

SECR and Southern Railway

The K class prototype was painted in an unlined dark grey livery with white lettering and numbering. This Maunsell grey livery was introduced by the SECR as a wartime economy measure. On grouping in 1923, the SR replaced the liveries of the constituent companies with a standard sage green livery (the colour being that previously used by Urie on the LSWR) with black and white lining, primrose yellow numbering and "Southern" on the tender. From 1925, the K and K1 classes were repainted in a darker olive green livery, introduced by Maunsell, with plain white lining and primrose yellow markings. When rebuilt into the U and U1 classes, the locomotives were repainted in the olive green livery with "Southern" added to the tender tank. This was carried into the Second World War when labour shortages meant that many U class locomotives were painted in plain black, with the result that by 1945 all the class were running in black. The livery was reverted to olive green when overhauls were due.

The class prototype was initially numbered 790, with the rest following consecutively with a prefix "A" to denote a locomotive designed for the former SECR. The system of prefixes had been adopted by the SR to distinguish between locomotives with identical numbers acquired from different companies, and the K1 class became No. A890 when built in 1925. This system was replaced from 1928 by a renumbering of all locomotives into one sequence, in which the K class rebuilds became Nos. 1790–1809, and the K1 class rebuild became No. 1890.

Rebuilds in British Railways service

The K and K1 classes were absorbed by British Railways as part of the U and U1 classes in 1948, which were given the BR power classification 4P3F. The locomotives at first retained their Southern Railway livery, but with "British Railways" on the tender. Those locomotives that had light repairs prior to 1950 had an "S" prefix added to the Southern number. From 1949 to 1950, the U and U1 class locomotives were repainted in the British Railways mixed-traffic lined black livery with red, cream and grey lining and the British Railways crest on the tender. Numbering was changed to the British Railways standard numbering system: the series 31790–31809 was allocated to the K class rebuilds, and 31890 to the K1 class.

References

Bibliography

• Casserley, H.C.: 'End of the Maunsell moguls—the Southern maids-of-all-work' (Railway World: 1966, 27), pps. 436–440)
• Clarke, Jeremy: 'The locomotives of R.E.L. Maunsell, Part 3: The 'Mogul' family – SECR' (Steam World, 2008 (248)), pp. 38–41
• Clarke, Jeremy: 'The locomotives of R.E.L. Maunsell, Part 4: The 'Mogul' family – SR' (Steam World, 2008 (249)), pp. 54–57
• Haresnape, Brian: Maunsell Locomotives – a pictorial history (Ian Allan Ltd, 1977), ISBN 0711007438
• Herring, Peter: Classic British Steam Locomotives (Abbeydale Press: London, 2000) Section "U Class" ISBN 1861470576
• Ian Allan ABC of British Railways Locomotives, winter 1958–59 edition
• Langston, Keith: British Steam Preserved: Illustrated Comprehensive Listing of Ex-British Railways Steam Locomotives (Horncastle: Morton's Media Group Ltd., 2008)
• Longworth, Hugh: British Railway Steam Locomotives: 1948–1968 (Oxford Publishing Company: Oxford, 2005) ISBN 0860935930
• Middlemass, Tom: 'The "Woolworths" — Woolwich Arsenal's tentative entry into main line locomotive building' (Backtrack, 1990 (4)), pp. 148-54
• Scott-Morgan, John: Maunsell Locomotives (Ian Allan Publishing: Hinckley, 2002), ISBN 0711028729

Further reading

• Bradley, D.L.: 'Locomotive history of the South Eastern and Chatham Railway' (Railway Correspondence and Travel Society, 1980), pp. 66–82 and pp. 115–121

See also

• List of SECR K and SR K1 class locomotives
• SR U class
• SR U1 class

External links

• Southern e-group page