Editing LSWR N15 class (section)

==Operational details==
The N15&nbsp;class was intended to haul heavy expresses over the long [[South West Main Line|LSWR mainlines]] between [[London Waterloo railway station|Waterloo]], [[Weymouth railway station|Weymouth]], [[Exeter Central railway station|Exeter]] and [[Plymouth Friary railway station|Plymouth]].<ref name=Cockman /> Locomotives were changed at {{stnlnk|Salisbury}} before the upgrading of the South Western Mainline in 1922, when fast running through to Exeter was possible.<ref name=Bradley46>Bradley (1987), p. 46</ref> The Southern Railway's motive power re-organisation following the [[Railways Act 1921|Grouping]] of 1923 saw the class allocated to sheds across the network and used on {{stnlnk|Bournemouth}} to {{stnlnk|Oxford}} cross-country trains.<ref name=Bradley48>Bradley (1987), p. 48</ref> Operations were expanded to more restricted Central and Eastern section mainlines in 1925, and suitably modified class members hauled commuter and heavy boat trains from {{Stnlnk|London Victoria}} to {{Stnlnk|Dover Marine}} and expresses to {{Stnlnk|Brighton}}.<ref name=Cockman>Cockman (1980), p. 12</ref> In 1931, No.&nbsp;E780 ''Sir Persant'' hauled the inaugural ''[[Bournemouth Belle]]'' [[Pullman train (UK)|Pullman train]] from Waterloo to {{Stnlnk|Bournemouth West}}.<ref name=Bradley117>Bradley (1987), p. 117</ref>

In peacetime, the class was occasionally used on fast freights from [[Southampton Docks]], although it was common to see them at the head of freight and troop trains during the [[World War II|Second World War]]. Ten "Urie Arthurs" were transferred to the [[London and North Eastern Railway]] (LNER) in October 1942, and were based at Heaton shed for use on freight and occasional passenger trains in the north east and southern [[Scotland]].<ref name=Bradley55>Bradley (1987), p. 55</ref> They returned to the Southern Railway in July 1943 after the introduction of [[United States Army Transportation Corps]] [[USATC S160 Class|S160 class]] [[2-8-0]]s into service.<ref name=Bradley55 /> From 1945 the King Arthur class regularly deputised for [[SR West Country and Battle of Britain classes|Bulleid's new Pacifics]], which were experiencing poor serviceability due to mechanical failures. The entire class came into British Railways ownership in 1948: they could be found in most areas of the [[Southern Region of British Railways|Southern Region]] on medium-length expresses and stopping trains on the ex-LSWR mainline.<ref name=Bradley62>Bradley (1987), p. 62</ref>

===Smoke deflector experiments===
In 1926, the N15 class became the first in Britain equipped with [[smoke deflector]]s, with several designs tested.<ref name=Holcroft462-89>Holcroft (1942), pp. 462–489</ref><ref name=Swift-32>Swift (2006), p. 32</ref> Experiments were undertaken throughout 1926 and included the fitting of a curved plate above the smokebox of No.&nbsp;E753 ''Melisande'' to channel air from below the chimney to lift the exhaust above the locomotive when on the move.<ref name=Haresnape56>Haresnape (1983), p. 56</ref> Nos.&nbsp;E450 ''Sir Kay'' and E783 ''Sir Gillemere'' had air scoops attached to the chimney, whilst E772 ''Sir Percivale'' was fitted with large, square German-type smoke deflectors.<ref name=Haresnape55-59>Haresnape (1983), pp. 55–59</ref> Finally, No.&nbsp;E453 ''King Arthur'' was fitted with small, rectangular smoke deflectors fitted to the handrails on the smokebox sides.<ref name=Haresnape55>Haresnape (1983), p. 55</ref> The experiments produced mixed results, and Maunsell requested the assistance of the [[University of London]] in staging [[Wind tunnel|wind tunnel tests]] .<ref name=Bradley48 /> These resulted in a standard plate design (illustrated in the infobox), which was gradually fitted to the class from late 1927 onwards.<ref name=Swift-32 />

===Performance of the Urie batch and modifications===
Under LSWR ownership, the N15s were initially well received by crews, though the batch soon gained a reputation for poor steaming on long runs.<ref name=Clarke-49 /> Through running of the class into Exeter was stopped in favour of engine changes at Salisbury, and Urie attributed the problem to poor driving technique.<ref name=Bradley44 /> A series of trial runs changed this assumption, and demonstrated that steam pressure gradually decreased on the flat.<ref name=Clarke-49 /> The trials also revealed that the robust construction of the motion produced the heaviest [[hammerblow (railway)|hammerblow]] of any British locomotive class, and had caused cracked frames on the test locomotive.<ref name=Bradley43-44>Bradley (1987), pp. 43–44</ref>

Another criticism from locomotive crews concerned the exposed cab in bad weather, which necessitated the installation of a [[tarpaulin]] sheet over the rear of the cab and the front of the tender, restricting rearward vision.<ref name=Chadwick439-442>Chadwick (2005), pp. 439–442</ref> The [[Black Friday (1921)#The mining crisis, March 1921|1921 Coal Miners’ strike]] meant that two class members (Nos.&nbsp;737 and 739) were converted to oil-burning.<ref name=Bradley44 /> One of the modified locomotives subsequently caught fire at Salisbury shed, and both were reverted to coal firing by the end of the year.<ref name=Bradley44 /> When the LSWR was amalgamated into the Southern Railway in 1923, Urie had done little to remedy the shortcomings of the N15s, and it fell to his successor to improve the class.<ref name=Bradley44 />

When Maunsell inherited the design as CME of the Southern Railway, he began trials using the weakest N15 (No.&nbsp;742) in 1924.<ref name=Bradley46 /> The results indicated that better performance could be obtained by altering the steam circuit, valve travel and draughting arrangements, although the first two recommendations were deemed too costly for immediate implementation by the Locomotive Committee.<ref name=Bradley46 /> Eight extra King Arthur-type boilers were ordered from North British and fitted to N15s Nos.&nbsp;737–742 by December 1925 in an effort to improve steaming.<ref name=Bradley48 /> The remaining Urie boilers were fitted with standard Ross pop safety valves to ease maintenance.<ref name="Haresnape54" /> Maunsell also addressed draughting problems caused by the narrow Urie "stovepipe" chimney.<ref name=Clarke-49 /> The exhaust arrangements were modified on No.&nbsp;737 using the King Arthur chimney design and reduced-diameter [[blastpipe]]s.<ref name="Haresnape54" /> This proved successful, and all "Urie N15s" were modified over the period 1925–1929.<ref name=Swift-38>Swift (2006), p. 38</ref> The oil-burning equipment was refitted to Nos.&nbsp;737 and 739 during the 1926 [[1926 United Kingdom general strike|General Strike]] and removed in December of that year.<ref name=Bradley48 />

Beginning in 1928, all but No.&nbsp;755 had their [[Cylinder (locomotive)|cylinder]] diameter reduced from {{convert|22|in|mm}} to {{convert|21|in|mm}} when renewals were due, improving speed on flat sections of railway, but affecting their performance on the gradients west of Salisbury.<ref name=Clarke-50 /> No.&nbsp;755 ''The Red Knight'' was modified in 1940 by Maunsell's successor, [[Oliver Bulleid]] with his own design of {{convert|21|in|mm|adj=on}} cylinders and streamlined steam passages. This was married to a [[Lemaître exhaust|Lemaître]] multiple-jet [[blastpipe]] and wide-diameter chimney, allowing the locomotive to produce performances akin to the more powerful Lord Nelson class.<ref name=Bradley53>Bradley (1987), p. 53</ref> Four other N15s were so modified with four more on order, though the latter were cancelled due to wartime shortages of metal.<ref name="Haresnape60" />  The soft exhaust of the Lemaître multiple-jet blastpipe precipitated an adjustment to the smoke deflectors on three converted locomotives, with the tops angled to the vertical in an attempt to improve air-flow along the boiler cladding.<ref name="Haresnape60" /> This failed to achieve the desired effect, and the final two modified locomotives retained the Maunsell-style deflectors.<ref name=Bradley53 />

The final modifications to the "Urie N15s" involved the conversion of five locomotives (Nos.&nbsp;740,&nbsp;745,&nbsp;748,&nbsp;749 and 752) to oil-firing in 1946–1947.<ref name=Bradley57>Bradley (1987), p. 57</ref> This was in response to a government scheme to address a post-war coal shortage.<ref name=Bradley57 /> The oil tanks were fabricated from welded steel and fitted within the tender coal space.<ref name=Bradley57 /> After initial problems with No.&nbsp;740 ''Merlin'' were rectified, the oil-fired locomotives proved good performers on Bournemouth services.<ref name=Bradley57 /> A further addition to the oil-fired locomotives was electric headcode and cab lighting, which was retained when the engines reverted to coal-firing in 1948.<ref name=Bradley57 />

===Performance of the Maunsell batches and modifications===
The improved front-end layout applied to the first batch of "Eastleigh Arthurs" (Nos.&nbsp;E448–E457) ensured continuous fast running on flat sections of track around London, although their propensity for speed was sometimes compromised over the hilly terrain west of Salisbury.<ref name=Bradley51>Bradley (1987), p. 51</ref> The inside bearings of the Drummond "watercart" tenders proved problematic, as they were too small for the load carried and suffered from water ingress.<ref name="Haresnape55" /> The retention of the tall Drummond cab prevented use away from the Western section of the Southern Railway.<ref name="Haresnape55" /> Despite these problems, their operational reliability prompted the management to arrange the visit of No.&nbsp;E449 ''Sir Torre'' to the Darlington Railway Centenary celebrations in July 1925.<ref name=ObsBkRailways>Casserley (1952), p. 77</ref> No.&nbsp;E449 also recorded speeds of up to {{convert|90|mph|abbr=on}} on the South West Mainline near {{stnlnk|Axminster}} in 1929.<ref name=Bradley51 /> This proved that with the right components, Urie's original design could perform well.<ref name= Nock172 />

Despite the successful use of modified N15 components to rebuild Nos.&nbsp;E448–E457, the mechanically similar "Scotch Arthurs" proved disappointing when put into service from May 1925.<ref name=Bradley101 /> The performance of those allocated to the Eastern section was indifferent, and failed to improve upon the [[double-heading|double-headed]] ex-SECR [[4-4-0]]s they were to replace.<ref name=Bradley101 /> Reports of poor steaming and hot driving and tender wheel axleboxes were common from crewmen and shed fitters.<ref name=Bradley101 /> After investigation, the problems were attributed to poor workmanship during construction as the North British Locomotive Company underquoted production costs to gain the contract.<ref name=Bradley103>Bradley (1987), p. 103</ref>  Defects were found in boiler construction across the batch, and necessitated six replacement boilers, re-riveting, re-fitting of tubes and replacement of firebox stays.<ref name=Bradley103 /> The hot driving wheel axleboxes were caused by the main frames being out of alignment.<ref name=Bradley103 /> A 1926 report suggested that all affected locomotives should be taken to Eastleigh for repair.<ref name=Bradley103 /> Once repaired, the "Scotch Arthurs" proved as capable as the rest of the class in service.<ref name= Nock172 />

"Scotch Arthurs" Nos.&nbsp;E763–E772 received new tenders between 1928 and 1930 in a series of tender exchanges with the Lord Nelson and [[LSWR S15 class|LSWR S15]] classes.<ref name=Bradley109>Bradley (1987), p. 109</ref> This ensured that they could exchange their Urie {{convert|5000|impgal|L|sigfig=3|abbr=on}} bogie tenders with the {{convert|4000|impgal|L|sigfig=3|abbr=on}} Ashford design for use on the shorter Eastern section routes.<ref name=Bradley107 /> Whilst useful for the roster clerks at Battersea shed, any transfer to the Western section was hampered because of their shorter range.<ref name=Bradley107 /> By 1937, all had reverted to the Urie {{convert|5000|impgal|L|sigfig=3|abbr=on}} bogie tenders, though Nos.&nbsp;E768–E772 were attached to new Maunsell flush-sided tenders with brake vacuum reservoirs fitted behind the coal space.<ref name=Bradley109 /> These were again swapped with Maunsell LSWR-style bogie tenders fitted to the Lord Nelson class.<ref name=Bradley109 />

The second batch of "Eastleigh Arthurs" displaced the ex-[[SECR K and K1 classes|K class]] tanks and ex-[[LB&SCR H2 class|LBSCR H2 "Atlantic"]] [[4-4-2 (locomotive)|4-4-2]] locomotives on the {{stnlnk|Eastbourne}} and {{stnlnk|Bognor Regis}} routes respectively.<ref name=Bradley107 /> They were well liked by crews and used on this part of the network until the arrival of electrification.<ref name=Bradley118 /> No.&nbsp;E782 ''Sir Brian'' was used on the former [[Great Northern Railway (Great Britain)|Great Northern]] main line for performance trials against the SECR K and K1 class tanks following the [[Sevenoaks railway accident]] in 1927.<ref name=Pringle36>Pringle (1928), p. 36</ref> The tests were supervised by the [[London and North Eastern Railway]]'s CME, Sir [[Nigel Gresley]], who commented that the class was unstable at high speeds.<ref name=Pringle37>Pringle (1928), p. 37</ref> The instability was caused by motion hammerblow and exacerbated by irregularities in track-work.<ref name=Pringle36 /> This caused excessive stress to the axleboxes and poor riding characteristics on the [[footplate]].<ref name=Haresnape52>Haresnape (1983), p. 52</ref> Despite this, the class benefited from an excellent maintenance regime.<ref name=Bradley118>Bradley (1987), p. 118</ref>

Maunsell's successor [[Oliver Bulleid]] believed that there was little need to improve draughting on this series. However, reports of poor steaming with No.&nbsp;792 ''Sir Hervis de Revel'' gave him an opportunity to trial a Lemaître multiple-jet blastpipe and wide-diameter chimney on a Maunsell N15 in 1940.<ref name=Bradley123>Bradley (1987), p. 123</ref> This did not enhance performance to the extent of No.&nbsp;755 ''The Red Knight''.<ref name=Bradley123 /> Under British Railways ownership, the locomotive was re-fitted with the Maunsell chimney in March 1952 with no further problems reported.<ref>Bulleid, H.A.V. (1979) – for information on Oliver Bulleid's modifications.</ref> In another wartime experiment, Bulleid fitted No.&nbsp;783 ''Sir Gillemere'' with three thin "stovepipe" chimneys in November 1940.<ref name=Haresnape61>Haresnape (1983), p. 61</ref> These were set in a triangular formation to reduce visibility of exhaust from the air in response to attacks made by low-flying aircraft on Southern Railway trains.<ref name=Bradley123 /> The "stovepipes" were reduced to two,  producing a fierce exhaust blast that dislodged soot inside tunnels and under bridges.<ref name=Haresnape61 /> The experiment was discontinued in February 1941 and the locomotive re-fitted with a Maunsell King Arthur chimney.<ref name=Bradley123 /> The last experiment was with spark-arresting equipment in response to lineside fires caused by poor quality coal.<ref name=Bradley124>Bradley (1987), p. 124</ref> Nos.&nbsp;784 ''Sir Nerovens'' and 788 ''Sir Urre of the Mount'' were fitted with new wide-diameter chimneys in late 1947.<ref name=Bradley124 /> Test-trains showed mixed results and the trials were stopped in 1951 after improvements in coal quality and the fitting of internal smokebox spark-arrestors.<ref name=Bradley124 />

===Withdrawal===
The detail variations across the class meant the "Urie N15s" were placed into store over the winters of 1949 and 1952.<ref name=Bradley58>Bradley (1987), p. 58</ref> The Maunsell King Arthur examples were easier to maintain, and the large number of modern Bulleid Pacific and British Railways [[BR standard classes|Standard]] classes were able to undertake similar duties.<ref name=Clarke-48>Clarke (April 2008), p. 48</ref> The "Urie N15s" were brought into service during the summer months, although their deteriorating condition was demonstrated when No.&nbsp;30754 ''The Green Knight'' was withdrawn with cracked frames in 1953.<ref name=Bradley58 /> The slow running-down of the "Urie N15s" continued between 1955–1957, and several were stored prior to withdrawal.<ref name="Bradley62" /> The last three were withdrawn from service at Basingstoke shed, with No.&nbsp;30738 "King Pellinore" the final example to cease operation in March 1958.<ref name="Bradley62" /> All were broken up for scrap, though their names were given to 20 [[BR Standard Class 5]] locomotives allocated to the Southern Region between 1959–1962.<ref name="Bradley62" />

The Maunsell King Arthur class also faced a decrease in suitable work on the Central and Eastern sections following the introduction of BR Standard class 5MT and [[BR Standard Class 4 4-6-0]]s in 1955.<ref name=Bradley129 /> The gradual withdrawal of the "Urie N15s", H15s and [[SR N15X class|SR N15x]] classes presented an opportunity to replace the ageing Drummond "watercart" tenders fitted to Nos.&nbsp;448–457 with Urie {{convert|5000|impgal|L|sigfig=3|abbr=on}} bogie tenders.<ref name=Bradley129>Bradley (1987), p. 129</ref> This coincided with a 1958 programme to similarly change the {{convert|3500|impgal|L|sigfig=3|abbr=on}} Ashford tenders fitted to eight of the second batch "Eastleigh Arthurs".<ref name=Bradley130>Bradley (1987), p. 130</ref> The class remained intact until the completion of the [[Railway electrification in Great Britain|Eastern section electrification]] when 17 were made redundant in 1959.<ref name=Herring /> More withdrawals took place in 1960 when an increase in Bulleid Pacifics allocated to the Western section reduced available work.<ref name=Haresnape63>Haresnape (1983), p. 63</ref> The ranks thinned to 12 in 1961, and further withdrawals reduced the class to one, No.&nbsp;30770 ''Sir Prianius''.<ref name=Haresnape63 /> The class outlasted the newer – but less numerous – [[SR Lord Nelson Class|Lord Nelson]] class by one month when No.&nbsp;30770 was withdrawn from service at Basingstoke Shed in November 1962.<ref name=Herring /><ref>{{Cite web |url=http://www.brdatabase.info/locoqry.php?action=class&id=346005&type=S&page=fleet |title=LSWR/SR Urie "N15" Class 4-6-0 |website=www.brdatabase.info |access-date=23 May 2018 |url-status=live |archive-date=24 May 2018 |archive-url=https://web.archive.org/web/20180524083219/http://www.brdatabase.info/locoqry.php?action=class&id=346005&type=S&page=fleet}}</ref>

{|class="wikitable" style=text-align:center
|+ Table of withdrawals
! Year !! Quantity in<br />service at<br />start of year !! Number withdrawn !! Quantity<br />withdrawn !! Locomotive numbers
|-
| 1953 || 74 ||  1  ||  1 || align=left | 30754
|-
| 1955 || 73 ||  4  ||  5 || align=left | 30740/43/46/52 
|-
| 1956 || 69 ||  6  ||  11 || align=left | 30736–37/41/44–45/47
|-
| 1957 || 63 ||  8  ||  19  || align=left | 30739/42/48–51/53/55
|-
| 1958 || 55 ||  3  ||  22  || align=left | 30454,<br />30738/66
|-
| 1959 || 52 ||  17  ||  39  || align=left | 30449/52/55,<br />30767/76/78–80/84–87/89/92/97,<br />30801/05
|-
| 1960 || 35 ||  9  ||  48  || align=left | 30448/50/56,<br />30763/69/74–75/91/94
|-
| 1961 || 26 ||  14  ||  62  || align=left | 30453/57,<br />30764/68/71–72/77/83/90/99,<br />30800/02–03/06
|-
| 1962 || 12 ||  12  ||  74  || align=left | 30451,<br />30765/70/73/81–82/88/93/95–96/98,<br />30804
|-
|}