SECR/SR N class[1] | |||||||||||||||||||||||||
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File:BR Class N 31871 Plymouth 1948.jpg N class No. 31871 at Plymouth in 1948, painted in early British Railways livery | |||||||||||||||||||||||||
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The SECR N class were 2-6-0 (mogul) steam locomotives designed by Richard Maunsell for mixed-traffic duties on the South Eastern and Chatham Railway (SECR) in 1917, and were also constructed by the Southern Railway (SR) between 1923 and 1934. As the first non-Great Western Railway (GWR) locomotive to use and improve upon the basic principles established by GWR Chief Mechanical Engineer (CME) George Jackson Churchward, the class represents an important stage in the development of the British steam locomotive.[2] The N class was based on the GWR 4300 Class, improved by applying Midland Railway ideas to the design.[3] The Ns were mechanically similar to their contemporary SECR K class 2-6-4 passenger tank engine counterparts, and influenced future 2-6-0 development in Britain.
N class production was delayed by the outbreak of the First World War in 1914. It was not until 1917, three years after the original design was completed, that the first member of the class was built at Ashford works. The design was intended to replace several classes of elderly 0-6-0 locomotives and was an initial step in the SECR fleet's standardisation, using parts designed to be interchangable with future classes. Some members of the class were assembled from kits of parts made at the Royal Arsenal, Woolwich, leading to the class's nickname of "Woolworths".
A total of 80 locomotives were built in three batches between the First and Second World Wars, and the design formed the basis for the 3-cylinder N1 class of 1922. They were able to operate over most of the Southern Railway network after grouping in 1923, and continued to operate with British Railways (BR) until 1966, when the last was withdrawn from service. One N class locomotive has been preserved on the Watercress Line.[4]
Background
The new locomotive was designed prior to the K class passenger tank locomotive in 1914 to address the SECR's requirement for a sturdy mixed-traffic locomotive with high route availability on its network.[5] It was intended to replace several elderly 0-6-0 classes within the SECR's running fleet, and attempted to standardise and ease maintenance of locomotives by sharing parts with other Maunsell designs.[5] The style of the new locomotive reflected the Midland Railway influence of one of Maunsell’s assistants, the ex-Midland Railway engineer James Clayton.[6]
Maunsell also enlisted the help of the former GWR engineer Harold Holcroft, who had been recruited by the SECR as another of Maunsell's assistants. At Holcroft’s suggestion, the new locomotive was to be of the 2-6-0 wheel arrangement, allowing it to operate over the lightly laid track-work of the SECR, whilst allowing an increased size of the boiler to that of the 0-6-0s.[2] This also allowed the design to have sufficient power to negate the costly procedure of double-heading 0-6-0 locomotives to haul trains.[5] To aid mass production, the new locomotive incorporated many features previously found on the successful GWR 4300 class, representing the first use of the Churchward design principles outside of the GWR.[5] The addition of a tender to the N class design increased its operating range over that of its K class tank engine counterpart.[6]
Design details and construction history
First SECR batch
Designed in 1914 by Maunsell as a modern solution to problems experienced by the SECR with increasingly obsolete mixed traffic designs operating on poorly laid track-work, production of the N class was delayed by the outbreak of the First World War. Production began towards the end of the war with No. 810 emerging from Ashford works in September 1917, a month after the first of the K class 2-6-4.[5] As a result of Holcroft’s position as one of Maunsell’s assistants, the new locomotive displayed several Churchward influences, making them similar to the GWR 4300 class.[1] These ideas included the use of a Belpaire firebox instead of the previously used round-topped version, long-travel valves for free running up to 70 mph (110 km/h), a sharply tapered boiler and finally right-hand drive, all of which featured on Maunsell’s K class locomotives.[6]
The similarity with Churchward locomotive practice ended there, as Midland Railway influences could be found with the placement of the locomotive fittings, as the water top-feed into the boiler was located inside a dome, whilst the cab area bore a strong resemblance to those featured on designs by Henry Fowler.[6] These aesthetic aspects of the locomotive were James Clayton’s contributions to the creation of a simple, functional locomotive.[7] The new locomotives also varied with an increased amount of superheating surface area, and were equipped with outside Walschaerts valve gear.[8] After entering traffic, No. 810 was run in and trialled over a period of three years before the construction of 14 further locomotives between 1920 and 1923. The entire first batch of the N class was built at Ashford works, and were all equipped with Maunsell’s 3,500-imperial-gallon (15,911 L) tenders.[1]
Second "Woolworth" batch
Because of the various mismatched classes already under the SECR's control, the standardisation of the SECR's locomotive fleet was a key consideration as the status quo placed an unnecessary burden on its meagre financial resources.[9] The cheap manufacture of N class locomotive parts and its streamlined steam passages made it a successful design when trialled, and the Ministry of Supply ordered several of the class to be constructed at the Royal Arsenal, Woolwich after the end of the First World War. This was a measure for retaining staff at a time when munitions production was being run down following First World War, earning the class the "Woolworths" nickname.[5] Fabrication of the boilers was contracted out to the North British Locomotive Company because of limited production capacity at Woolwich and the SECR's own locomotive works, and were delivered for allocation to a kit of parts.[6]
The construction of prefabricated components at Woolwich meant that 100 complete kits of parts were available for purchase from the government at the time of grouping, and 26 were sold to the Great Southern and Western Railway of Ireland, whilst six went to London Transport's Metropolitan Railway, where they were converted into tank engines.[5] The rest of the kits at Woolwich remained unsold, and were later used as the basis of future classes of Maunsell locomotives.[10] Another aspect of the British government's interest in the N class came from a proposal to nationalise the railways, which would have required a standard locomotive fleet to promote economies in maintenance and production.[6] The proposal was abandoned in favour of grouping the railways into the "Big Four" from 1923 under the Railways Act 1921.[5] As a result of this, the class was readily adopted by the newly formed Southern Railway, and 50 of the Woolwich kits were purchased from the government and assembled at Ashford works between June 1924 and August 1925.[11] The 65 N class locomotives now operating on the Southern Railway were equipped with the standard right-hand drive characteristic of Ashford works. The success of the 2-cylinder design spawned the 3-cylinder N1 class locomotive. This illustrated the "family" nature of the Maunsell moguls where in 1922, the kit of parts for what was to become N class No. 822 was altered to form the N1 class prototype by adding a third cylinder between the frames.[5]
Final Southern Railway batch and further modifications
The final batch of 15 locomotives was constructed between July 1932 and January 1934.[6] These had various detail differences to the first 15 and the "Woolworth" batch, the major alteration being the adaptation of the design to encompass the Southern Railway's newly adopted left-hand drive standard.[12] Further detail differences included the addition of U1 class components such as the dome and chimney, which were of a lower profile than the original N design, increasing route availability on routes with low bridges and tunnels.[5]
The new locomotives were equipped with 4,000-imperial-gallon (18,184 L) tenders, resulting in a step on the footplate caused by the boiler backhead being slightly lower than the tender fall-plate that connected the tender and cab floors.[7] The locomotives constructed after 1930 were supplied with steps on the front buffer beam below the smokebox; the earlier locomotives were not provided with this refinement until overhauled later in their careers.[8] From 1933, the entire class was fitted with smoke deflectors, and although originally equipped with smokebox-mounted snifting valves, these were removed by Oliver Bulleid at the end of the Second World War.[11]
Operational details and preservation
By developing Churchward’s design principles and combining them with the best practices from other railways, the N class provided an important step forward for the British 2-6-0 concept, creating a capable workhorse equally adept at hauling passenger or freight traffic.[5] Whilst the class began the SECR’s, and latterly the Southern Railway’s "family" of standardised moguls and 2-6-4 locomotives (which included the K and K1, N1, U, U1 and W classes), the N class also provided the inspiration for future 2-6-0 designs, such as the LMS Hughes Crab of 1926.[11]
The quality of the design inspired the Southern Railway to put No. A866 on public display at the British Empire Exhibition at Wembley from May to November 1925.[5] One drawback in operating the class was the size of the cylinders and cab, which meant that the N class was out of gauge for the Tonbridge-Hastings line due to inadequate clearances in bridges and tunnels along the route.[13] Otherwise, their high route availability when undertaking the mixed-traffic role meant that the class migrated from the Southern Railway's Eastern section to work on the Central and Western sections, where a robust and reliable locomotive design such as the N class was to see use throughout the Southern Railway era.[11] The class had high capacity, tapered boilers that promoted free steaming, and small 5 ft 6 in (1.68 m) driving wheels that delivered considerable tractive effort, ensuring that the class performed well when hauling heavy loads during the Second World War.[14]
Whilst the original design was ideal for the Southern Railway, the N class was subjected to equipment trials, with No. 1850 being fitted with J. T. Marshall valve gear between 1933 and 1934.[15] This revealed little improvement over the standard Walschaerts type, and the locomotive was reverted to the original configuration to ease maintenance. Before nationalisation in 1948, government-backed locomotive fuelling trials were made in anticipation of a post-war coal shortage, and No. 1831 was converted to oil burning in 1947, until reverted to coal-firing when the crisis failed to materialise in 1948.[1] Under British Railways, the class was reclassified from 4MT to 4P5FB in 1953, with "B" representing the old Southern Railway power classification for its locomotives.[16] Their heavy usage under British Railways is evident, as between 1955 and 1961 29 of the class were re-cylindered due to excessive wear.[5] Frames were occasionally replaced but generally, only the front end was re-conditioned when outside steam pipes were fitted to the replacement cylinders, visible behind the smoke deflectors.[5] Another source of miscellany was that from 1957, some of the class, such as No. 31412, began to receive British Railways Standard Class 4 chimneys to improve draughting.[4]
In their British Railways (Southern Region) days, the N class performed well on passenger and goods duties in the West Country.[17] Withdrawals from service occurred between 1962 and 1966, when the N class' work was taken over by Oliver Bulleid’s Light Pacifics, and the electrification of much of the former Southern Railway network was imminent. Only a single member of the class has been preserved, British Railways No. 31874, which was rescued from the Woodham Brothers scrapyard in Barry, Vale of Glamorgan, South Wales.[16] One of the "Woolworth" batch, this locomotive was purchased and restored for use on the Mid-Hants Railway from 1977, and is currently stored pending overhaul.[4]
Livery and numbering
SECR and Southern Railway
When grouping occurred in 1923, the liveries sported by the constituent companies were standardised.[11] The N class was initially painted in Maunsell SECR grey with white lettering and numbering, a wartime standard livery.[1] This was changed to LSWR Sage green after the grouping, with yellow numbering and "Southern" on the tender. From 1931, the class was repainted in Maunsell's lined Southern Railway Olive green, again with yellow markings.[8] With the outbreak of the Second World War in 1939, locomotive Nos. 1413 and 1850 were painted Olive green with no lining due to the cutbacks on labour.[11] Others were released in wartime black when their overhauls became due.[1] Some of the locomotives (Nos. 1821/25/47/78 & 1403) had acquired a Maunsell-style green livery in 1941 with Bulleid gilt lettering; these were also unlined due to wartime constraints.[11] All N class locomotives were painted black by the end of the war.[1] Two locomotives, Nos. 1817 and 1854, received Bulleid's Malachite green livery in 1946 with yellow and black lining and "Sunshine Yellow" lettering replacing the gilt.[1]
Numbering was also complex, reflecting the initial slow pace of production.[11] Ashford works constructed 15 locomotives for the SECR, numbered from 810–824 between August 1917 and December 1923.[11] The Royal Arsenal batch of 50 locomotives purchased by the newly formed Southern Railway from 1923 were numbered from A825–A875.[1] The letter "A" reflected the post-grouping practice of the Southern Railway to denote the engine's place of origin within the pre-grouping (SECR in this case) number.[11] This helped to prevent confusion with locomotives of similar numbers that the Southern Railway acquired from other pre-grouping railway companies. The "A" in this case denotes Ashford, where the Woolwich batch was assembled from the series of kits, whilst the SECR batch was renumbered in the same format. The Southern Railway numbering policy was eventually rationalised, and from 1928 the locomotives were renumbered from 1810 to 1875.[1] The final batch of 15 locomotives, built between 1932 and 1934, were therefore numbered 1400–1414 from new.[1]
British Railways
The class was absorbed by British Railways in 1948, and were initially given the British Railways Power classification 4MT.[18] Livery was initially similar to that of 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.[19] Numbering was under the British Railways standard numbering system, and were allocated the series 31810–31875 for the earlier locomotives, and 31400–31414 for the final 15.[18]
References
Notes
- ^ a b c d e f g h i j k Haresnape, section: "N class"
- ^ a b Casserley, p. 436
- ^ Scott-Morgan, p. 18
- ^ a b c Casserley, p. 440
- ^ a b c d e f g h i j k l m n Middlemass, (Backtrack: 4), pp. 148–154
- ^ a b c d e f g Clarke (Steam World, 2008 (248)), p. 40
- ^ a b Clarke (Steam World, 2008 (248)), p. 39
- ^ a b c Clarke (Steam World, 2008 (248)), p. 38
- ^ Herring, pp. 120–121
- ^ Scott-Morgan, p. 4
- ^ a b c d e f g h i j Reynolds, pp. 155-156
- ^ Reynolds, p. 156
- ^ Clarke (Steam World, 2008 (248)), p. 41
- ^ Casserley, p. 437
- ^ Locomotive, Railway Carriage and Wagon Review (44, 1938), pp. 373–376
- ^ a b Langston, p. 108
- ^ Casserley, p. 439
- ^ a b Ian Allan ABC, 1952–53
- ^ Banks, p. 66
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: 27, 1966), 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
- 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
- Ian Allan ABC of British Railways Locomotives, winter 1958–59 edition
- Reynolds, W.J.: 'The Maunsell moguls' (S.R. Railway Magazine, 1943, 89), pps. 155–8; 199–202; 279–82
- Scott-Morgan, John: Maunsell Locomotives (Ian Allan Publishing: Hinckley, 2002), ISBN 0711028729
- '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