U 2-6-0 SR Maunsell 31610 – 31639 & 31790 – 31809

U1

U2.jpg

 

 

Power Classification 4MT reclassified 4P3F in 1954
Introduced 31790 – 31809 – 1917 – 1925, rebuilt 1928

31610 – 31639 – 1928 – 1934

Designer Maunsell
Company SR
Weight – Loco 31790 – 31809 – 63t 0cwt

31610 – 31639 – 62t 6cwt

               Tender 31790 – 31809 – 40t 10cwt

31610 – 31639 – 42t 8cwt

Driving Wheels 6ft 0ins
Boiler Pressure 200psi superheated
Cylinders Outside – 19in x 28in
Tractive Effort 23,865lbf
Valve Gear Walschaert (piston valve)

The class represented the penultimate stage in the development of the Southern Railway’s mogul 2-6-0 locomotives, which improved upon the basic principles established by GWR Chief Mechanical Engineer (CME) Churchward for Great Western Railway (GWR) locomotives. The U class design drew from experience with the GWR 4300 and N classes, improved by applying Midland Railway ideas to the design, enabling the SECR to influence development of the 2-6-0 in Britain.

When Maunsell produced his first 2-6-0 tender engine number 810 (N class) in 1917, he also built a corresponding 2-6-4T engine number 790 (K class). The 2-6-4T was intended for express duties on the SECR main line. After the Second World War another nineteen appeared in 1925 and an additional engine (890) was fitted with three cylinders and was known as the K1 class. The whole class was named after rivers and were thus known as the River class.

The K class proved successful on well-maintained track. It was capable of high speeds on express passenger duties, although their use 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 many of the former London and South Western Railway (LSWR) routes west of London. The need to save weight meant that compromises were made in some aspects of the design. The boiler size was constrained by the SECR’s axle-loading restrictions, with the result that the design’s full steaming potential was not realised. The failure to capitalise upon a larger boiler would also affect Maunsell’s subsequent 2-6-0 classes, as they were given the same boiler despite their lower axle-loadings.

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 rolling was in part caused by the type of coil suspension and steadying springs used on the Bissel truck and bogie axles, which caused adverse springing on poor track. These were modified in later batches, with limited success. The rough-riding was also attributed to the frames, which were of insubstantial construction to save weight. The bracing proved incapable of counteracting the stresses applied to the frames when travelling at speed and caused excessive vibration on the footplate at higher outputs.

The K1 prototype was slightly faster and more powerful than the K class, and gave a smoother ride at low speeds. It was also found to have a wider route availability due to the smaller outside cylinders. However, the Holcroft valve gear proved to be difficult to maintain in everyday service. This locomotive was also noted for particularly poor riding characteristics at high speed, derailing twice in 1927. The first derailment occurred at Borough Green & Wrotham, near Maidstone on 31 March, when the flanges of the lead coupled wheel mounted the rails at 60 mph. The second derailment was at Bearsted on 20 August, when the lead driving wheel mounted and completely dropped off the rails at 40 mph, derailing the train and causing serious damage to the track. These derailments were attributed to the slightly higher centre of gravity of the boiler on the K1. Although the official reports of these accidents blamed the poor quality of the track, a group of directors sought to have both classes banned from use on passenger services, but were overruled by the Southern Railway’s Chairman of the Board of Directors, Everard Baring on grounds of cost.

In August 1927 800 River Cray was derailed at speed at Sevenoaks, with disastrous results (see accidents and incidents below for details).

In the days following the accident, two K and K1 class engines were trialled on the London and North Eastern Railway’s (LNER) Great Northern mainline under the supervision of that company’s CME, Nigel Gresley, to gain an unbiased review of their riding qualities. Locomotives A803 (K class) and A890 (K1 class), and King Arthur class 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 a top speed of 83mph was achieved by A890 with A803 managing 79mph, with no problems in riding. When these engines returned from the LNER, the Southern Railway’s General Manager, Sir Herbert Walker ordered further trials to be led by Sir John Aspinall on the 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 80 miles per hour rendered the locomotives unsafe. The instability of A890 at speed was attributed to the helical springs on the Bissel truck and bogie.

The 1928 accident inquiry did not attach blame to the Southern Railway for track maintenance or locomotive performance issues, and noted that the prototype had run for eight years over the same stretch of line without complaint. However, it identified the Brighton batch and A890 as being more susceptible to rolling on sharp curves with weak rail joints, although the entire class operated without incident on the former LBSCR network. The management of the Southern Railway realised that to have any success in operating the K class tanks on other parts of the network, 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. This decision also reduced the adverse publicity generated by the accident. However, many of the components discarded during the rebuilding process would later be re-used on another 2-6-4 tank locomotive designed to haul heavy freight on short trips: the 3-cylinder W class of 1932.

31790-31809 were rebuilt from K class 2-6-4Ts in 1928 at Eastleigh (31790-31796), Ashford (31797-31802) and Brighton (31803-31809). They all formerly carried river names.

The rebuilt locomotives were given a tender and a re-designed cab that bore a strong resemblance to those featured on designs by Henry Fowler. Two designs of Maunsell tender were used, the straight-sided 3,500 gallons variety, and the larger 4,000 gallon design used on later batches of the N class with inward-sloping raves to prevent coal spillage. The first rebuild was No. A805 River Camel, which also became the first U class locomotive into service in March 1928, three months before the first production locomotive under construction at Brighton. The rapid turnaround was achieved as design work was already in place, and the rebuilding of existing locomotives was cheaper than building from scratch.

A805 was put on performance trials prior to work commencing on rebuilding of the rest of the class at Brighton and Eastleigh works. The rebuilds lost their names because of the bad publicity attached to the River class after the 1927 crash, and the heavily damaged A800 was the last member of the K class to be rebuilt to U class configuration in December 1928. The unique 3-cylinder River tank, K1 class A890 River Frome was also rebuilt to the general U class specification, becoming the prototype of Maunsell’s 3-cylinder U1 class derivative in June 1928.

The first of the production batch emerged from Brighton works in August 1928 and featured a tapered chimney and smokebox snifting valves, both of which were used on the K and N class locomotives.

31610-31639 were built new although they had originally been ordered as 2-6-4Ts and work had begun on the first ten of these, but they were all delivered as 2-6-0s.

In common with the N, N1 and K class locomotives, the Midland Railway influence of Clayton showed in the placement of locomotive fittings on the production batch, as the water top-feed into the boiler was located inside a dome, whilst the cab area was a modified version of those on the 0-6-0s of Fowler and the K class rebuilds. The rebuilds had Midland Railway-style double spectacle plates (the small windows on the front face of the cab) left over from the K class cabs, whereas the production versions had one each side of the boiler. Such modifications were becoming typical of the Southern Railway’s attempt to produce a fleet of standardised locomotives. However, all members of the U class were to vary from GWR practice, as the superheating surface area was increased, and all were equipped with outside Walschaerts valve gear.

The second batch of ten new-build U class locomotives was constructed between February and May 1931 when more obsolete locomotives were withdrawn from service. The first five of this batch were sent to Battersea Park shed for use on Central Section express services while Nos. A635 to A639 went to Redhill for the Reading line services and Sunday excursions to the Sussex coast.

This brought the total of new-build locomotives to 30, and the total number of operational U class engines to 50. The new batch also featured detail differences from the rest of the class, such as the arrangement of the footsteps at the front of the locomotive, though continued to use the standard left-hand drive cab layout to improve the driver’s forward vision from the cab. Smoke deflectors were fitted to the whole class from 1933 to prevent drifting smoke from obscuring forward vision. The smokebox snifting valves applied to the class by Maunsell were removed by his successor Oliver Bulleid, who also fitted U1 class chimneys to improve the draughting.

The U class was a reliable and economical design more than capable of attaining speeds in excess of 70 mph as a result of being fitted with long-travel valves. They had high capacity, tapered boilers which promoted free steaming, and 6 ft driving wheels which allowed fast running over long distances. They were distributed more widely than their N class counterparts, although one drawback in operating the class was the size of the cylinders and cab, which meant the U class was out of gauge for the Tonbridge-Hastings line due to inadequate clearances in tunnels along the route. (The U1 class were built specifically to work this line). Otherwise, their go anywhere nature earned them the nickname of U-Boats, and crews praised their abilities to achieve what they were designed to do.

The Southern Railway operating department undertook trials to improve fleet efficiency. When built, Eastbourne-based A629 was fitted with an experimental pulverised fuel burner of German design; the experiment was terminated when a minor explosion was caused by the powdered coal coming into contact with sparks thrown from the blastpipe. The experiment also proved that pulverised coal was a false economy, as much of the fine dust was sucked through the chimney without combustion taking place. The locomotive was returned to normal coal burning in 1935. In 1947 the class became a test-bed for a government-backed scheme regarding fuelling arrangements in anticipation of a coal shortage. Two of the class, 625 and 1797, were converted to oil burning, with more set to follow suit; but the project was abandoned and the two oil burners were reverted to coal-firing before this could take place.

All members of the class entered British Railways service in 1948, and from 1955 23 of the U class received chimneys of the British Railways Standard Class 4 variety and replacement cylinders, which had become worn through intensive use. A few members of the class were given replacement frames at overhaul with a shallower curve between the front buffer beam and smokebox. During the early 1960s, the withdrawal of the ageing T9 class designed by Drummond saw the U class replacing them on services west of Exeter, though their large wheels offered little advantage on the steeper gradients that characterised this part of the railway network. The favoured form of 2-6-0 motive power west of Exeter was the smaller-wheeled N class, while heavier passenger work was allocated to Bulleid’s Unrebuilt Light Pacifics, which were within the weight restrictions imposed in this area. The U class represented one of the less glamorous classes of passenger locomotive due to the fact that they were used mainly on mixed-traffic and secondary passenger duties.

Number in Service.

Built

Withdrawals No. in Service
BR Numbers Quantity
1917 31790

  1

  1

1925 31791-99

  9

10

1926 31800-09

10

20

1928 31610-21

12

32

1929 31622-29

  8

40

1931 31630-39

10

50

1932-61

50

1962

  2

48

193

14

34

1964

24

10

1965

  6

  4

1966

  4

  0

  • 31610-19 and 31800-09 were built at Brighton
  • 31620-39 and 31790 were built at Ashford
  • 31791-99 were built by Sir W G Armstrong Whitworth & Co Ltd.
  • 31790-809 were rebuilds of K class 2-6-4Ts whilst 31610-39 were new builds.
  • 31790 was withdrawn from service in May 1965 whilst based at Guildford.
  • The last four were withdrawn from service at Guildford in 1966. 31809 in January, 31803 in March and 31639 and 31791 in June.

Allocation of locomotives in service as at 1st of January.

Depot

1948 1955 1960

1965

Basingstoke

  5

  2

  2

Bournemouth

  3

  1

Eastleigh   7

16

Exmouth Junction

  3

Faversham

  3

  3

Fratton

  1

  6

Guildford

13

12 20

10

Higher Green

  1

Nine Elms

  5

  3

  5

Reading South

  6

Redhill

  3

Salisbury

  5

  3

Yeovil Town

  6

  9

  7

50

55 50

10

Accidents and Incidents

  • The Sevenoaks railway accident, involving a K class 2-6-4T occurred, on 24 August 1927 between Dunton Green railway station and Sevenoaks railway station. The Southern Railway’s afternoon express from Cannon Street to Deal left London at 5pm, in charge of River Class tank engine 800 River Cray. Several passengers later recounted that from time to time the train seemed to roll excessively on fast curves. As it passed through Pollhill Tunnel at 60 mph the rocking became violent and the train derailed past Dunton Green railway station. Unfortunately, the line at that point is in a cutting which is spanned by a bridge carrying Shoreham Lane. The cab of the locomotive struck the bridge and the engine was turned it on its side across the cutting. The leading coaches piled up against it, killing 13 and injuring many more.
  • On 25 May 1933, a passenger train was derailed at Raynes Park, London, coming to rest foul of an adjacent line. Locomotive 1618, hauling a passenger train, was in a side-long collision with it. Five people were killed and 35 were injured. The cause of the accident was the failure to implement a speed restriction on a section of track that was under maintenance.
  • On 14 November 1949, a rake of carriages was left foul of an adjacent line at Bournemouth Central station, Hampshire. Locomotive 31624 collided with them and was derailed. One person was injured.
  • On 18 November 1962, locomotive 31816 was derailed at Tipton Yard, Eastleigh, Hampshire.

Preservation

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