Editing LSWR N15 class (section)

{{Short description|Class of 74 two-cylinder 4-6-0 locomotives}}
{{Featured article}}
{{Use dmy dates|date=December 2023}}
{{Use British English|date=December 2013}}
{{Infobox locomotive
| powertype = Steam
| name = LSWR N15&nbsp;class<br />SR King Arthur class<ref name="Swift-84–91">Swift (2006), pp. 84–91</ref>
| image = Waterloo King Arthur' geograph-2635554-by-Ben-Brooksbank.jpg
| imagesize = 320
| alt = A steam locomotive waiting with its train at a station
| caption = 30453 ''King Arthur'' at Waterloo
| designer = {{unbulleted list|[[Robert Urie]]|[[Richard Maunsell]] ''(redesign)''|[[Oliver Bulleid]] ''(modifications)''}}
| builder = {{unbulleted list|SR [[Eastleigh Works]] (44)|[[North British Locomotive Company|North British Locomotive Co.]] (30)}}
| builddate = 1918–1927
| totalproduction = 74
| whytetype = {{whyte|4-6-0}}
| uicclass = 2′C h2
| gauge = {{Track gauge|uksg|allk=on}}
| leadingdiameter = {{convert|3|ft|1|in|m|3}}
| driverdiameter = {{convert|6|ft|7|in|m|3}}
| length = {{convert|66|ft|5+3/4|in|m|2}}
| locoweight = {{bulleted list|{{Long ton|80|19|lk=on}} for numbers 448–452 and 763–792
|{{Long ton|79|18}} for numbers 453–457
|{{Long ton|81|17}} for numbers 793–806}}
| fueltype = [[Coal]]
| fuelcap = {{Long ton|5|0}} ''(Urie outside-frame bogie tender)''
| watercap = {{unbulleted list|{{convert|5200|impgal|L|sigfig=3|abbr=on}}<br />&emsp; ''(Urie outside-frame bogie tender)''|{{convert|5000|impgal|L|sigfig=3|abbr=on}}<br />&emsp;&emsp; ''(Maunsell bogie tender)''|{{convert|4500|impgal|L|sigfig=3|abbr=on}}<br />&emsp;&emsp; ''(Drummond bogie tender)''|{{convert|4300|impgal|L|sigfig=3|abbr=on}}<br />&emsp;&emsp; ''(Drummond "watercart" tender)''|
{{convert|3500|impgal|L|sigfig=3|abbr=on}}<br />&emsp;&emsp; ''(Six-wheel tender)''}}
| cylindercount = Two, outside
| cylindersize = {{unbulleted list|{{convert|22|×|28|in|mm|abbr=on}}<br />&emsp;&emsp; ''(Urie batch – as built)''|{{convert|21|×|28|in|mm|abbr=on}}<br />&emsp;&emsp; ''(Urie batch – as modified)''|
{{convert|20+1/2|×|28|in|mm|abbr=on}}<br />&emsp;&emsp; ''(Eastleigh/Scotch batches)''}}
| boilerpressure = {{unbulleted list|{{convert|180|psi|MPa|2|abbr=on|lk=on}}<br />&emsp;&emsp; ''(Urie batch)''|{{convert|200|psi|MPa|2|abbr=on}}<br />&emsp;&emsp; ''(Eastleigh/Scotch batches)''}}
| tractiveeffort = {{convert|26245|lbf|kN|2|lk=on|abbr=on}}<br />&emsp;&emsp; ''(Urie batch unmodified)''<br />{{convert|23900|lbf|kN|2|lk=on|abbr=on}}<br />&emsp;&emsp; ''(Urie batch as modified)''<br />{{convert|25320|lbf|kN|2|lk=on|abbr=on}}<br />&emsp;&emsp; ''(Maunsell Batches)''
| operator = [[London and South Western Railway]],<br />[[Southern Railway (UK)|Southern Railway]], <br />[[British Rail]]ways
| operatorclass = {{unbulleted list|''LSWR:'' N15|''SR / BR:'' King Arthur}}
| powerclass = {{unbulleted list|''LSWR / SR:'' A|''BR:'' 5P}}
| nicknames = ''Eastleigh Arthurs'', ''Scotch Arthurs'', ''Scotchmen''
| withdrawndate = 1953 (1), 1955–1962
| locale = [[Southern Region of British Railways|Southern Region]]
| preservedunits = [[SR N15 class 777 Sir Lamiel|SR No.&nbsp;777]]
| disposition = One preserved, 2 boilers preserved, remainder scrapped
}}

The '''LSWR N15 class''' was a British 2–[[Cylinder (locomotive)|cylinder]] [[4-6-0]] express passenger [[steam locomotive]] designed by [[Robert Urie]]. The class has a complex build history spanning three sub-classes and ten years of construction from 1918 to 1927. The first batch of the class was constructed for the [[London and South Western Railway]] (LSWR), where they hauled heavy [[express passenger train]]s to the south coast ports and further west to [[Exeter]]. After the [[SR Lord Nelson class|Lord Nelsons]], they were the second biggest 4-6-0 passenger locomotives on the Southern Railway. They could reach speeds of up to 90&nbsp;mph (145&nbsp;km/h).<ref>{{cite web |title=30777 – Sir Lamiel |url=https://www.gcrailway.co.uk/the-railway/locomotives/30777-sir-lamiel/ |website=Great Central Railway |access-date=1 November 2020 |archive-date=8 November 2020 |archive-url=https://web.archive.org/web/20201108140844/https://www.gcrailway.co.uk/the-railway/locomotives/30777-sir-lamiel/ |url-status=live }}</ref><ref>{{cite web |title=N15 4-6-0 LSWR Urie & SR Maunsell King Arthur 30448 – 30457, 30736 – 30755 & 30763 – 30806 |url=https://preservedbritishsteamlocomotives.com/n15-4-6-0-lswr-urie-sr-maunsell-king-arthur-30448-30457-30736-30755-30763-30806/ |website=Preserved British Steam Locomotives |date=20 June 2017 |publisher=WordPress.com |access-date=1 November 2020 |archive-date=5 October 2020 |archive-url=https://web.archive.org/web/20201005142526/https://preservedbritishsteamlocomotives.com/n15-4-6-0-lswr-urie-sr-maunsell-king-arthur-30448-30457-30736-30755-30763-30806/ |url-status=live }}</ref>

Following the [[Railways Act 1921|grouping of railway companies]] in 1923, the LSWR became part of the [[Southern Railway (UK)|Southern Railway]] (SR) and its publicity department gave the N15 locomotives names associated with [[Arthurian legend]]; the class hence becoming known as '''King Arthurs'''.<ref name=Nock172>Nock (''British Steam Locomotives'': 1983), p. 172</ref> The [[chief mechanical engineer]] (CME) of the newly formed company, [[Richard Maunsell]], modified the Urie locomotives in the light of operational experience and increased the class strength to 74 locomotives. Maunsell and his Chief Draughtsman [[James Clayton (engineer)|James Clayton]] incorporated several improvements, notably to the [[steam circuit]] and [[valve gear]].

The new locomotives were built over several batches at [[Eastleigh Works]] and [[North British Locomotive Company|Glasgow]], leading to the nicknames of "Eastleigh Arthurs", "Scotch Arthurs" and ''Scotchmen'' in service.<ref>{{cite book |last1=Maidment |first1=David |title=The Urie and Maunsell Cylinder 4-6-0s |date=2016 |publisher=Pen & Sword Books Limited |location=Barnsley, United Kingdom |isbn=9781473852532 |page=66 |url=https://books.google.com/books?id=ufq0DQAAQBAJ |access-date=1 November 2020 |archive-date=19 October 2021 |archive-url=https://web.archive.org/web/20211019205815/https://www.google.com/books/edition/The_Urie_and_Maunsell_Cylinder_4_6_0s/ufq0DQAAQBAJ?q |url-status=live }}</ref> The class was subjected to smoke deflection experiments in 1926, becoming the first British class of steam locomotive to be fitted with [[smoke deflectors]]. Maunsell's successor, [[Oliver Bulleid]], attempted to improve performance by altering [[Steam locomotive exhaust system|exhaust]] arrangements. The locomotives continued operating with [[British Rail]]ways (BR) until the end of 1962. One example, [[SR N15 class 777 Sir Lamiel]], is preserved as part of the [[National Collection]] and can be seen on mainline [[railtour]]s.