SR N class

Infobox Locomotive
powertype=Steam
name = SR N classHaresnape, section: "N class"]

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caption = BR N class number 31871 at Plymouth 1948 in early BR livery
designer = Richard Maunsell
builder = SECR/SR Ashford Works
builddate = 1917–1934
whytetype = 2-6-0
gauge = RailGauge|ussg
leadingsize = 3 ft 1 in (0.94 m)
driversize = 5 ft 6 in (1.89 m)
length = 57 ft 10 ins (17.4 m)
weight = 103 tons 12 cwt (105.1 tonnes)
fueltype = Coal
fuelc

waterc

cylindercount = Two, outside
cylindersize = 19 × 28 in (483 × 710 mm)
boilerpressure = 200 lbf/in² (1.38 MPa)
tractiveeffort = 26,035 lbf (115.80 kN)
valvegear = Walschaerts
railroad = South Eastern and Chatham Railway, Southern Railway, British Railways
railroadclass = SECR / SR: N
BR: 4P5F
retiredate = 1962–1966
numinclass = 80
disposition = One preserved, remainder scrappedThe SR N class were 2-6-0 (mogul) steam locomotives designed by Richard Maunsell for mixed-traffic duties, initially on the South Eastern and Chatham Railway (SECR), and latterly on the Southern Railway. A highly standardised class of locomotive, the N class had a long period of conception, delayed by the First World War in 1914, and was not introduced until 1917, three years after the original design.

Several members of the class were manufactured as kits of parts at the Royal Arsenal, Woolwich, and given the nickname "Woolworths". Able to operate over most of the Southern Railway network after grouping in 1923, the N class survived until 1966, when all had been withdrawn from service. Only a single example has been preserved.

Background

The class was a respone to the South Eastern and Chatham Railway's requirement for a sturdy mixed-traffic locomotive with high route availability on its network. The design was a replacement for the elderly classes that were still present in this railway's running fleet, resulting in a requirement for standardisation and ease of maintenance. This had to be married to the ability for the new locomotive to operate over the lightly laid trackwork on the SECR, and as a result, the 2-6-0 wheel arrangement was settled upon. The design was to have mass production in mind, and the result was the two-cylinder N class.Middlemass, ("Backtrack": 4), pp. 148–154]

Construction history

Designed in 1914 by Richard Maunsell as a modern solution to the problems the SECR experienced with ageing and unspectacular mixed traffic designs, the N class' production was delayed by the outbreak of the First World War.Haresnape, section: "N class"]

Production finally began towards the end of the war with number 810 emerging from Ashford works in July 1917. The new locomotive showed a heavy Swindon influence, as GWR engineer Harry Holcroft had been recruited by the SECR as Maunsell's assistant. The locomotives were superheated and were equipped with Walschaerts valve gear.Clarke (Steam World, 2008 (248)), p. 38]

Standardisation of the SECR's locomotive fleet was a key consideration due to the various mismatched classes already under that railway's control, which placed an unnecessary burden on its financial resources. Herring, pp. 120–121] Effective standardisation of locomotive parts meant that the design was successful when trialled, and the Ministry of Supply ordered several of the class to be constructed at the Royal Arsenal, Woolwich, after the war, earning the locomotive the nickname "Woolworths".

The British government's interest in the standardisation potential of the N class stemmed from an early attempt to nationalise the railways, although this idea was soon abandoned in favour of grouping the railways into the "Big Four" from 1923.

The ease of construction through the manufacturing of prefabricated components at Woolwich meant that many were available for purchase at the time of Grouping, and several were sold to Ireland and the Metropolitan Railway. The class was readily adopted by the newly formed Southern Railway, and 50 were assembled at Ashford. Reynolds, pp. 155-156] The first 65 built were equipped with the standard right hand drive characteristic of Ashford works. The success of the design, spawned the ill-fated SECR K Class 2-6-4Ts which used the front end and boiler of the N design.

Final batch and further modifications

The final batch of 15 locomotives were constructed between 1932 and 1934. These had various detail differences to the "Woolworth" batches, the major alteration being the adaptation of the design to encompass the Southern's adopted left-hand drive standard. Reynolds, p. 156]

Further detail differences were the implementation of U1 class components, such as the dome and chimney, which were of a lower profile than the original N design. These locomotives were also equipped with 4,000 gallon (18,160 litre) tenders, and sported a step on the footplate, the area of the boiler backplate being lower than that of the tender fall&ndashplate.Clarke (Steam World, 2008 (248)), p. 39]

From 1933, the entire class was supplied with smoke deflectors, and although originally equipped with smokebox-mounted snifting valves, these were removed by the end of the Second World War. The batch constructed after 1930 was also equipped with front steps when built; those built earlier did not encompass this refinement until later in their careers.Clarke (Steam World, 2008 (248)), p. 38]

Operational details and preservation

The N class proved to be an ideal workhorse equally adept at undertaking passenger or freight traffic, from semi&ndashfast passenger duties to pick&ndashup goods. Number A866 was put on display at the British Empire Exhibition at Wembley from May to November 1925, as Southern Railway 866. Locomotive number 822 was built as the prototype three-cylinder version to be known as the N1 class. The N class was subjected to many trials, with number 1850 being fitted with J. T. Marshall valve gear in 1933–34."Locomotive, Railway Carriage and Wagon Review" (44, 1938), pp. 373–376] This was a short&ndashlived trial, as it was soon reverted to standard Walschaerts gear.

Before nationalisation, government-backed locomotive fuelling trials meant that 1831 was converted to oil burning during 1947 and converted back in 1948.Haresnape, section: "N class"] Their heavy usage began to show, as from 1955 until 1961, 29 of the class had to be re-cylindered due to wear. Frames were occasionally replaced but generally, only the front end was re-conditioned, where outside steampipes were fitted to the new cylinders. Another source of operational miscellany was that from 1957, some of the class began to receive British Railways Standard Class 4 chimneys, one such example being number 31412.Casserley, p. 440]

The N class was a robust, reliable locomotive design that eventually saw use throughout the Southern network. They had high capacity, tapered boilers that enabled free steaming, and small coupled wheels that delivered considerable tractive effort, ensuring that the class performed well when hauling heavy loads during the Second World War.Casserley, p. 437] Their high route availability when undertaking this role meant that the class migrated from the SR Eastern section to work additionally on the Central and Western sections, and in their British Railways (Southern Region) days continued to perform well on passenger and goods duties in the West Country.Casserley, pp. 436–440] Withdrawals occurred between 1962 to 1966, and only a single member of the class has been preserved, British Railways number 31874, and after many years' service is in store on the Mid-Hants Railway pending overhaul.

Livery and numbering

SECR and Southern Railway

When grouping occurred in 1923, the liveries sported by the constituent companies were standardised. The N class was initially painted in Urie LSWR Green, and ran in this guise throughout the 1920s, with yellow numbering and "Southern" on the tender. From 1931, the class was repainted in Maunsell lined Southern Railway Olive Green, once again with yellow markings.Clarke (Steam World, 2008 (248)), p. 38]

Upon the outbreak of the Second World War in 1939, locomotive numbers 1413 and 1850 were painted Olive Green with no lining due to the inevitable cutbacks on labour. Others were released in wartime black when their overhauls became due.Haresnape, "N class] However, some of the locomotives (numbers 1821/25/47/78 & 1403) had, by 1941 acquired a new Maunsell Green livery, though received the new Bulleid gilt lettering; these were also unlined due to wartime constraints. All N class locomotives had been painted black by the end of the war.Haresnape, section: "N class"] Two locomotives, numbers 1817 and 1854, received Bulleid's Malachite Green livery in 1946 with yellow and black lining and "Sunshine Yellow" lettering replacing the gilt.Haresnape, section: "N class"] Numbering was also a highly complex issue, a reflection of the initial slow pace of production. Ashford works had constructed a mere 15 locomotives numbered from 810–824 by December 1923, which were numbered under SECR parlance. The Royal Arsenal batch of 50 locomotives purchased by the newly formed Southern Railway from 1923 were numbered from A825–A875.Haresnape, section: "N class"]

The letter "A" reflected the post-grouping practice of the Southern to denote the engine's place of origin within the pre-grouping (SECR in this case) number. This helped to prevent confusion with locomotives of similar numbers also acquired from other pre-grouping railway companies. The "A" in this case denotes Ashford, where the Woolwich batch was assembled from a series of kits. Southern numbering policy was eventually rationalised, and from 1928, the locomotives were renumbered 1810 to 1875.Haresnape, section: "N class"] The final batch of 15 locomotives, built between 1932 and 1934, were numbered 1400–1414 without the "A" prefix.

Post-1948 (nationalisation)

The class was absorbed by British Railways in 1948, and were given the British Railways Power classification 4P5F. Livery was initially as 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 and white lining, and the British Railways crest on the tender.Banks, p. 66] Numbering was under the British Railways standard system, and were allocated the series 31810–31875 for the earlier locomotives, and 31400–31414 for the final 15."Ian Allan ABC", 1958–59]

Footnotes

Bibliography

*Banks, Chris: BR Locomotives 1955 (Oxford Publishing Company: Oxford, 2001), ISBN 0860935604
*Casserley, H.C.: 'End of the Maunsell moguls—the Southern maids-of-all-work' ("Railway World": 1966, 27), pp. 436–440
*Clarke, Jeremy: 'The locomotives of R.E.L. Maunsell, Part 3: The 'Mogul' family – SECR' ("Steam World", 2008 (248)), pp. 38–41
*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
*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", Vol. 4, No. 4), pp. 148–154
*Reynolds, W.J.: The Maunsell moguls ("S.R. Railway Magazine", 1943, 89), pps. 155–8; 199–202; 279–82
*'SOME "improved" locomotive valve gears' ("Locomotive, Railway Carriage and Wagon Review": 44, 1938), pp. 373–376

Further reading

*Kirkland, R.K. 'The Woolwich Moguls- A locomotive family' ("Trains Illustrated": 1951, 4), pps. 134–137

External links

* [http://www.maunsell.org.uk/virtual%20shed/oddments/marshall.htm Number 1850 and the Marshall valve gear]