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 named after rivers flowing within the Southern Railway's operating area
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 (10.922 m) Length 43 ft 6+1⁄4 in (13.265 m) Height 12 ft 11+3⁄8 in (3.947 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Career Power class SR: A Number in class 21 Official name River class Nicknames Rolling Rivers Locale Great Britain Withdrawn 1927 Disposition All rebuilt to SR U class or SR U1 class 1 rebuild surviving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. 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 Charing Cross 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 cheap, 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, with freight locomotives on the Great Central Railway setting the only precedent for this wheel arrangement. The 2-6-4 wheel arrangement allowed for a long 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 design used a "Bissel bogie" leading axle and a plain trailing bogie, both fitted with leaf spring suspension. 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 Dover Marine, 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 coupled wheelbase between the rear and centre driving wheels was reduced from that used on the mechanically identical N class to 7 ft 9 in (2.362 m) to accommodate the bogie.

The K class incorporated Churchward design principles, and included the use of a Belpaire firebox instead of a round-topped version, a regulator located in the smokebox, 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. 790 was trialled for defects, and no more class members were constructed until 1925.

In 1922 a proposal for 10 K class locomotives was put forward. A trial non-stop run between London Cannon Street and Folkestone Harbour by No. 790 and a 300-ton (300-tonne) train had proved the water capacity of the side tanks to be insufficient for such runs. Holcroft suggested that 2-6-0 tender locomotives should be built instead, and he produced a diagram of this type, with 6 ft 0 in (1.829 m) driving wheels. Holcroft's immediate superior, Clayton, refused to pass this suggestion on to Maunsell.

The newly formed Southern Railway ordered a batch of 19 K class locomotives eight years after the prototype entered service. By January 1925 Ashford Works had manufactured parts for 20 K class locomotives. The assembly of these locomotives had been delayed by the need for Ashford to concentrate on repair work. On 14 January 1925 Maunsell ordered No. 790 to be overhauled and trialled on the Central section. As the locomotive proved suitable for the operating conditions of this section it was decided to proceed with the assembly of the K class parts by outside contractors.

Construction was divided between Armstrong Whitworth of Newcastle (Nos. A791–A799) and Brighton railway works (Nos. A800–A809). All boilers were constructed by the North British Locomotive Company and were stored at Woolwich Arsenal prior to despatch to Armstrong Whitworth and Brighton. The 9 locomotives that Armstrong Whitworth built 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, whilst the 10 Brighton locomotives only had vacuum for the SECR stock on the Eastern section. There were detail differences between the production locomotives and the prototype, the main being the provision of laminated springs to the bogie and leading axle, relocation of the regulator to the dome and an increase in superheater area.

K1 class

To increase the route availability of the K class, in 1925 the Southern Railway authorised the construction of a 21st 2-6-4 tank at Ashford works, with a revised cylinder arrangement. The modifications were based upon those applied to N class No. 822 in 1922, although it retained the 6 ft 0 in (1.829 m) driving wheels and shorter wheelbase of the K class. A larger-diameter chimney to that used on the K was utilised, and this was given a burnished top. Smaller-diameter "outside" cylinders were fitted (16 in (406.400 mm) bore; the K class had 19 in (482.600 mm)), with an additional ("inside") cylinder between the frames: the resulting prototype three-cylinder "K1" was narrower than the K class and hence 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. Despite this, the boiler had to be raised by 3 in (76 mm) above the "inside" gear for clearance purposes, raising the centre of gravity on the locomotive.

The main visual difference between the K and K1 classes was at the front end: the K1 incorporated a slab-front above the front buffer beam to house the third cylinder and associated Holcroft valve gear assembly. The K1 prototype emerged from Ashford works as No. A890, and underwent trials from 1 December 1925 before entering regular service.

Naming the locomotives

The K class 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 rivers found 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 No. A890 was named River Frome. The names were displayed on a rectangular brass nameplate fitted to the water tank sides.

K and K1 class construction history

Year	Batch	Quantity	SECR/SR numbers	Notes
1917	SECR (Ashford Works)	1	790
1925	SR (Armstrong Whitworth)	9	A791–A799	Class was named during construction, and this batch was fitted with dual air and vacuum braking
1926	SR (Brighton Works)	10	A800–A809	Production contracted out to Armstrong Whitworth and Brighton Works due to repair commitments at Ashford
1925	SR (Ashford Works)	1	A890	Prototype three-cylinder K1 class. No more K and K1 class locomotives built

Operational details

The K class was intended to haul the SECR's Kent expresses, and was trialled between Charing Cross, Tonbridge, Canterbury East and Folkestone East. The Southern Railway's motive power re-organisation following the Grouping of 1923 expanded the class for operations over the Central section. The Westinghouse-fitted Armstrong Whitworth batch allowed use on the air-braked Eastbourne and Brighton expresses and service trains to Portsmouth. The vacuum-braked Brighton batch was run-in on the Portsmouth route in preparation for operating the Redhill-Reading line, the class regularly hauling the daily Birkenhead-Dover through train. The K1 was mainly rostered to haul the early evening express from Cannon Street to Dover Marine.

Performance of the tank locomotives

The K class proved successful on well-maintained track. They were capable of high speeds on express passenger duties, although success was limited by the lower 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 Central and Eastern sections, crews complained that the locomotives rolled heavily and unpredictably on the cheaply-laid track of the former SECR and LBSCR networks, leading to their nickname, "Rolling Rivers".

The K1 was slightly faster and more powerful than the K class, but was noted for particularly poor riding characteristics, derailing twice between 1925 and 1927. These derailments were attributed to the slightly higher centre of gravity of the boiler on the K1.

Sevenoaks disaster

The K and K1 classes suffered from stability problems when travelling at speed over points and curves. The locomotive would initially roll (briefly lean heavily) to one side, followed by several further rolls of gradually reducing amplitude, combined with a side-slipping movement. Several minor derailments of members of the class culminated in the serious derailment of No. A800 River Cray at Sevenoaks, Kent, in August 1927, caused by a combination of a surge in the water tanks and the flanges of the locomotive's lead driving wheels mounting the rail at speed due to poor quality track-work. The locomotive was hauling a Cannon Street to Deal express with a Pullman carriage when it derailed at 55 mph (89 km/h) in a cutting. Several carriages were flung against a road bridge, injuring 40 and killing 13 passengers.

In the days following the accident, two K and K1 class engines were trialled on the London and North Eastern Railway’s (LNER) Great Eastern Railway mainline under the supervision of that company’s CME, Nigel Gresley. This was to gain an unbiased review of the riding qualities. Locomotives No. A803 (K) and No. A890 (K1), and King Arthur class No. E782, were tested on the well-maintained LNER line between Huntingdon and St. Neots in October 1927, where few problems were found with locomotive stability. On runs between Kings Cross and Potters Bar with the LNER's dynamometer car, No. A890 was recorded at a top speed of 83 miles per hour (134 km/h) and A803 at 79 miles per hour (127 km/h), with no problems in riding. When these engines returned from the LNER, further trials were carried out on the Southern Railway's Western section main line near Woking. These were terminated by the Southern Railway’s Operating Department, as the riding of the locomotives at speeds near 70 miles per hour (110 km/h) rendered the locomotives unsafe. The management of the Southern Railway realised that to have any success in operating the K class tanks, vast stretches of track would require upgrading. With the prospect of storing 20 locomotives whilst the necessary upgrading took place, the management recommended the class be fully withdrawn from service. To recoup the expense of constructing the engines, Maunsell was given permission to rebuild them to the new SR U class 2-6-0 tender engine design in 1928.

Rebuilding

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

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 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 water tanks, rear bogie and coal bunker were removed. The straight-sided 3,500 imperial gallons (15,911 L) variant 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. None of the rebuilds retained their names.

Performance of the rebuilt locomotives and withdrawal

As members of the U and U1 classes, rebuilds were used mainly on mixed-traffic as well as secondary passenger duties on lines between the main routes. They were used all over the Southern Railway network, but were little-used over the steep track gradients west of Exeter. The smaller-wheeled N class was preferred amongst crews for the same duties, 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. From 1955 a few were given replacement frames at overhaul: these had a shallower curve between the front buffer beam and the smokebox.

Withdrawals took place between 1962 and 1966, by which time the class was based at Guildford shed. 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.

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, after the war, 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.

Operational assessment and preservation

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

Despite their reputation for poor riding, the K and K1 classes were mechanically reliable and capable of hauling expresses at high speeds on well-maintained track, which meant that they could have been useful additions to the Southern Railway's suburban commuter fleet. This eventuality was prevented by the railway's Central section electrification scheme, poor track condition and the increasing size and weight of the rolling stock, which meant that there were fewer duties suitable for heavy passenger tank locomotives in 1928. The lack of a suitable role for both classes was considered when the decision was made to rebuild them as U/U1 tender engines following the Sevenoaks disaster. In rebuilt form they continued to operate until the 1960s, and were capable of attaining speeds in excess of 70 mph (110 km/h) with a greater degree of stability.

One K class rebuild has survived: No. A806 River Torridge – converted to U class No. 1806 – 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.

References

Bibliography

• Bradley, D.L.: Locomotives of the South Eastern and Chatham Railway (London: Railway Travel and Correspondence Society, 1961)
• 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
• Holcroft, H.: Locomotive Adventure: Fifty Years With Steam (Ian Allan: London, ND)
• 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

• Fryer, Charles: Railway Monographs No.1: The Rolling Rivers (Sheffield: Platform 5 Publishing, 1993) ISBN 1872524397
• Grayer, Jeffery: "Scuppering the "U-Boats"" in Robertson, Kevin: The Southern Way Issue No.7 (Corhampton: Noodle Books (July 2009)), pps. 60-65. ISBN 978 1 906419 17 2.
• Nock, O.S.: Great Locomotives of the Southern Railway (Guild Publishing/Book Club Associates, 1987) pp. 98-102,115,132-137,154-160. CN 5587
• Robertson, Kevin, ed.: "Scuppering the "U-Boats" - Years Earlier" (The Southern Way Issue No. 7: Corhampton, Noodle Books (July 2009)), pps. 66-67. ISBN 978 1 906419 17 2.

See also

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

External links

• Southern e-group page