Southern Railway U Class
Encyclopedia
The SR U class were 2-6-0
2-6-0
Under the Whyte notation for the classification of steam locomotives, 2-6-0 represents the wheel arrangement of two leading wheels on one axle, usually in a leading truck, six powered and coupled driving wheels on three axles, and no trailing wheels. This arrangement is commonly called a Mogul...

 (mogul) steam locomotives designed by Richard Maunsell
Richard Maunsell
Richard Edward Lloyd Maunsell held the post of Chief Mechanical Engineer of the South Eastern and Chatham Railway from 1913 until the 1923 Grouping and then the post of CME of the Southern Railway in England until 1937....

 for passenger duties on the Southern Railway (SR). The class represented the penultimate stage in the development of the Southern Railway’s mogul "family", which improved upon the basic principles established by GWR Chief Mechanical Engineer
Chief Mechanical Engineer
Chief Mechanical Engineer and Locomotive Superintendent are titles applied by British, Australian, and New Zealand railway companies to the person ultimately responsible to the board of the company for the building and maintaining of the locomotives and rolling stock...

 (CME) George Jackson Churchward
George Jackson Churchward
George Jackson Churchward CBE was Chief Mechanical Engineer of the Great Western Railway in the United Kingdom from 1902 to 1922.-Early career:...

 for Great Western Railway
Great Western Railway
The Great Western Railway was a British railway company that linked London with the south-west and west of England and most of Wales. It was founded in 1833, received its enabling Act of Parliament in 1835 and ran its first trains in 1838...

 (GWR) locomotives. The U class design drew from experience with the GWR 4300
GWR 4300 Class
The Great Western Railway 4300 Class is a class of 2-6-0 steam locomotive.- Overview :The class was introduced in 1911 to a G.J. Churchward design. 342 were built until 1932...

 and N classes, improved by applying Midland Railway
Midland Railway
The Midland Railway was a railway company in the United Kingdom from 1844 to 1922, when it became part of the London, Midland and Scottish Railway....

 ideas to the design, enabling the SECR to influence development of the 2-6-0 in Britain.

The U class was designed in the mid-1920s for production at a time when more obsolete 4-4-0
4-4-0
Under the Whyte notation for the classification of steam locomotives, 4-4-0 represents the wheel arrangement of four leading wheels on two axles , four powered and coupled driving wheels on two axles, and no trailing wheels...

 locomotives were withdrawn, and derived from Maunsell’s earlier SECR K (“River”) class 2-6-4
2-6-4
Under the Whyte notation for the classification of steam locomotives, a 2-6-4 locomotive has two leading wheels, six coupled driving wheels and four trailing wheels...

 tank locomotives. The first 20 members of the U class were rebuilds of the K class locomotives, one of which was involved in the Sevenoaks railway accident
Sevenoaks railway accident
The Sevenoaks railway accident 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 No 800 River Cray. Several passengers later...

. A further 20 U class locomotives were built in 1928 to fill the gap in cross-country and semi-fast express passenger services after the withdrawal of the K class. The design also continued the standardisation of the Southern Railway locomotive fleet by using parts designed to be interchangeable with other Maunsell-designed classes.

A total of 50 locomotives were built over three batches between 1928 and 1931, and the design formed the basis for the 3-cylinder U1 class of 1928. They were able to operate over most of the Southern Railway network, gaining the nickname "U-Boats" after the submarine warfare of the First World War, and continued to operate with British Railways (BR). The class saw continuous use until 1966, when all members of the U class were withdrawn from service. Four U class locomotives have been preserved on two heritage railways in the south of England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...

.

Background

The history of the U class is complex as it is linked to the fate of the 2-cylinder K (“River”) class 2-6-4 tank locomotives. The design work had for a new passenger 2-6-0 with 6 ft (1.83 m) driving wheels was complete by 1927, when the involvement of a K class locomotive in the Sevenoaks
Sevenoaks
Sevenoaks is a commuter town situated on the London fringe of west Kent, England, some 20 miles south-east of Charing Cross, on one of the principal commuter rail lines from the capital...

 rail crash presented an opportunity to bring forward construction of the class. The K class tank engines were the passenger counterpart to the N class 2-6-0 mixed-traffic design, and were noted for rough-riding over the cheaply-laid track of the former SECR. The class was withdrawn from service, and the inquiry that followed determined that the rough-riding contributed to the crash. Its recommendation was that the K class should be rebuilt to 2-6-0 tender locomotives, using tried and tested features used by Maunsell and his assistant, the former GWR engineer Harold Holcroft
Harold Holcroft
Harold Holcroft was a British railway and mechanical engineer who worked for the Great Western Railway , the South Eastern and Chatham Railway and the Southern Railway...

 on the N class.

The N class principles applied to the U class design aided mass production, and incorporated several features found on the GWR 4300 Class locomotives designed by Churchward. An order made in 1926 for a second batch of 20 K class locomotives was delayed until 1928, when the specification was revised to construct U class locomotives. It was intended to replace several elderly 4-4-0 classes within the former SECR's running fleet, and attempted to standardise and ease maintenance of locomotives by sharing parts with other Maunsell designs. The style of the new locomotive reflected the Midland Railway influence of another of Maunsell’s assistants, the ex-Midland Railway engineer James Clayton. The addition of a tender increased the operating range of the U class over its K class predecessors, and the wheel arrangement applied to the former K class locomotives improved the locomotive’s stability when operational.

Construction details

K class rebuilds

The rebuilding programme that followed the derailment of K class No. A800 "River Cray" at Sevenoaks began at Ashford works
Ashford railway works
Ashford railway works was in the town of Ashford in the county of Kent in England.-South Eastern Railway:Ashford locomotive works was built by the South Eastern Railway on a new site in 1847, replacing an earlier locomotive repair facility at New Cross in London...

 in June 1928. The work involved in converting a 2-6-4 tank engine to a 2-6-0 tender locomotive included the removal of the side water tanks, rear coal bunker and trailing axles, although the 6 ft (1.83 m) driving wheels, right-hand drive and N class–type boiler were retained. The aesthetic aspects inherited from the K class were the former Midland Railway engineer James Clayton’s contributions to the design, creating a simple, functional locomotive similar to the N class.

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
Henry Fowler
Henry Fowler may refer to:* Henry I of Germany , the Fowler, Duke of Saxony and King of the Germans*Henry Fowler * Henry Hartley Fowler, 1st Viscount Wolverhampton , British politician...

. Two designs of Maunsell tender were used, the straight-sided 3500 gallons (15,911.3 l) variety, and the larger 4000 gallons (18,184.4 l) 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
Brighton railway works
Brighton railway works was one of the earliest railway-owned locomotive repair works, founded in 1840 by the London and Brighton Railway in Brighton, England, and thus pre-dating the more famous railway works at Crewe, Doncaster and Swindon...

. The rapid turnaround was achieved as design work was already in place, and the rebuilding of existing locomotives was cheaper than building from scratch.

No. 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 No. 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 No. 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.

First production batch and differences with rebuilt locomotives

Construction of the delayed 1926 order for 20 K class locomotives began in 1928 after alteration to the U class specification. As a result of Harold Holcroft’s position as one of Maunsell’s assistants, the new-builds also displayed the Churchward GWR 4300 Class influence. The ideas applied to this class were already used on the N, N1 and K class rebuilds, including long-travel valves for fast running, Belpaire firebox
Belpaire firebox
The Belpaire firebox is a type of firebox used on steam locomotives. It was invented by Alfred Belpaire of Belgium. It has a greater surface area at the top of the firebox, improving heat transfer and steam production...

 and conical boilers, constructed at the North British Locomotive Works in Glasgow
Glasgow
Glasgow is the largest city in Scotland and third most populous in the United Kingdom. The city is situated on the River Clyde in the country's west central lowlands...

. The first of the production batch emerged from Brighton works in August 1928 and featured a tapered chimney and smokebox
Smokebox
A smokebox is one of the major basic parts of a Steam locomotive exhaust system. Smoke and hot gases pass from the firebox through tubes where they pass heat to the surrounding water in the boiler. The smoke then enters the smokebox, and is exhausted to the atmosphere through the chimney .To assist...

 snifting valve
Snifting valve
A snifting valve is an automatic anti-vacuum valve used in a steam locomotive when coasting. The word Snift imitates the sound made by the valve....

s, both of which were used on the K and N class locomotives.

The 20 locomotives of the first production batch were split equally between Brighton and Ashford works, and all were completed by December 1929. The production locomotives had a slightly different profile to the K class rebuilds and featured left-hand drive to improve the visibility of signals from the driver's side of the footplate. They also had higher running plates along the sides of the boiler than the rebuilds, which required larger wheel splashers to cover the tops of the driving wheels. Another variation was the flatter top to the dome covers, as the rebuilds retained the high N class type used on the K class.

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 Henry Fowler and the K class rebuilds. The rebuilds had Midland Railway-style double spectacle plates (the small window
Window
A window is a transparent or translucent opening in a wall or door that allows the passage of light and, if not closed or sealed, air and sound. Windows are usually glazed or covered in some other transparent or translucent material like float glass. Windows are held in place by frames, which...

s 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
Superheater
A superheater is a device used to convert saturated steam or wet steam into dry steam used for power generation or processes. There are three types of superheaters namely: radiant, convection, and separately fired...

 surface area was increased, and all were equipped with outside Walschaerts valve gear.

Second production batch and modifications

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. 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
Smoke deflectors
Smoke deflectors are vertical plates attached to the front of a steam locomotive on each side of the smokebox. They are designed to lift smoke away from the locomotive at speed so that the driver has better visibility unimpaired by drifting smoke....

 were fitted to the whole class from 1933 to prevent drifting smoke from obscuring forward vision. The smokebox
Smokebox
A smokebox is one of the major basic parts of a Steam locomotive exhaust system. Smoke and hot gases pass from the firebox through tubes where they pass heat to the surrounding water in the boiler. The smoke then enters the smokebox, and is exhausted to the atmosphere through the chimney .To assist...

 snifting valve
Snifting valve
A snifting valve is an automatic anti-vacuum valve used in a steam locomotive when coasting. The word Snift imitates the sound made by the valve....

s applied to the class by Maunsell were removed by his successor Oliver Bulleid
Oliver Bulleid
Oliver Vaughan Snell Bulleid was a British railway and mechanical engineer best known as the Chief Mechanical Engineer of the Southern Railway between 1937 and the 1948 nationalisation, developing many well-known locomotives.- Early life and Great Northern Railway :He was born in Invercargill,...

, who also fitted U1 class chimneys to improve the draughting.

Operational details and preservation

The U class was a reliable and economical design more than capable of attaining speeds in excess of 70 mph (31.3 m/s) as a result of being fitted with long-travel valves. They had high capacity, tapered boilers that promoted free steaming, and 6 ft (1.83 m) driving wheels that 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
Tonbridge
Tonbridge is a market town in the English county of Kent, with a population of 30,340 in 2007. It is located on the River Medway, approximately 4 miles north of Tunbridge Wells, 12 miles south west of Maidstone and 29 miles south east of London...

-Hastings
Hastings
Hastings is a town and borough in the county of East Sussex on the south coast of England. The town is located east of the county town of Lewes and south east of London, and has an estimated population of 86,900....

 line due to inadequate clearances in bridges and tunnels along the route. 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
Eastbourne
Eastbourne is a large town and borough in East Sussex, on the south coast of England between Brighton and Hastings. The town is situated at the eastern end of the chalk South Downs alongside the high cliff at Beachy Head...

-based No. 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
Blastpipe
The blastpipe is part of the exhaust system of a steam locomotive that discharges exhaust steam from the cylinders into the smokebox beneath the chimney in order to increase the draught through the fire.- History :...

. 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, Nos. 1625 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
BR standard class 4 4-6-0
The British Railways Standard Class 4 4-6-0 is a class of steam locomotives, 80 of which were built during the 1950s. Six have been preserved.-Background:...

 variety and replacement cylinders, which had become worn through intensive use. A few members of the class were given replacement locomotive frames with a shallower curve between the front buffer beam and smokebox at overhaul. During the early 1960s, the withdrawal of the aging T9 class designed by Dugald Drummond
Dugald Drummond
Dugald Drummond was a Scottish steam locomotive engineer. He had a career with the North British Railway, LB&SCR, Caledonian Railway and London and South Western Railway...

 saw the U class replacing them on services west of Exeter, though their large wheels offered little advantage on the steeper gradients the 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, whilst heavier passenger work was allocated to Bulleid’s Unrebuilt Light Pacifics, which were within weight restrictions imposed in this area. The U class represented one of the more unglamorous classes of passenger locomotive due to the fact that they were used mainly on mixed-traffic duties and secondary passenger duties between mainlines.

Withdrawals took place between 1962 and 1966, by which time the class was congregated around Guildford
Guildford
Guildford is the county town of Surrey. England, as well as the seat for the borough of Guildford and the administrative headquarters of the South East England region...

. The work for which they were designed was transferred to Bulleid’s newer ‘Pacific’ locomotives and electric motive power, making the U class surplus to requirements. Despite the entire class being sold for scrapping, four have survived into preservation, having been rescued from the Woodham Brothers scrapyard in Barry, Vale of Glamorgan, South Wales
South Wales
South Wales is an area of Wales bordered by England and the Bristol Channel to the east and south, and Mid Wales and West Wales to the north and west. The most densely populated region in the south-west of the United Kingdom, it is home to around 2.1 million people and includes the capital city of...

. The survivors are Nos. 1618 and 1638, both on the Bluebell Railway
Bluebell Railway
The Bluebell Railway is a heritage line running for nine miles along the border between East and West Sussex, England. Steam trains are operated between and , with an intermediate station at .The railway is managed and run largely by volunteers...

, and Nos. 31806 and 31625, based on the Mid-Hants Railway. No. 31806 is the only survivor of the K class rebuilds. However, the Maunsell Locomotive Society is considering 'un-rebuilding' their Bluebell-based U Class 1618 to K Class form, already having acquired the required trailing wheels.

Southern Railway

From 1928, the entire class was painted in Maunsell’s lined Southern Railway Olive green with yellow markings and "Southern" on the tender. During the Second World War, the U class was painted in wartime black livery with Oliver Bulleid
Oliver Bulleid
Oliver Vaughan Snell Bulleid was a British railway and mechanical engineer best known as the Chief Mechanical Engineer of the Southern Railway between 1937 and the 1948 nationalisation, developing many well-known locomotives.- Early life and Great Northern Railway :He was born in Invercargill,...

's Sunshine yellow lettering, and some were later painted in lined Malachite green
Malachite green
Malachite green is an organic compound that is used as a dyestuff and has emerged as a controversial agent in aquaculture. Malachite green is traditionally used as a dye for materials such as silk, leather, and paper...

 livery. The class was initially numbered in the Southern Railway's post-grouping system from A790–A809 for the K class rebuilds, and A610–A639 with the production batches. The "A" in the numbering system denotes Ashford, where the locomotive design had originated. Southern numbering policy was eventually rationalised, and final batch of 15 locomotives, built between 1932 and 1934, were numbered 1400–1414 without the "A" prefix. The other U class locomotives were subsequently renumbered to 1790–1809, and 1610–1639 at the same time.

British Railways

The entire class was absorbed by British Railways in 1948, and was given the Power classification 4P3F, denoting a mixed traffic locomotive.
Livery was initially similar to the Southern Railway, though with "British Railways" on the tender, and an "S" prefix to the Southern number. This was succeeded by the British Railways mixed-traffic lined black livery with red, cream and grey lining and the British Railways crest on the tender. The British Railways standard numbering system was used to replace the Southern Railway system, and the class was allocated the series 31790–31809 for the K class rebuilds, and 31610–31639 for the rest.

Further reading

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

External links

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