Editing GWR 4073 Class (section)

{{Short description|Class of 171 four-cylinder 4-6-0 locomotives}}
{{Use dmy dates|date=April 2024}}
{{Use British English|date=May 2013}}
{{Infobox locomotive
| name = GWR 4073 ''Castle'' class
| powertype = Steam
| image = File:GWR_4079_Pendennis_Castle_Didcot_Railway_Centre_4th_March_2023.jpg
| caption = 4079 ''Pendennis Castle'' at Didcot Railway Centre in 2023
| designer = [[Charles Collett]]
| builder = GWR / BR [[Swindon Works]]
| builddate = 1923–1950
| ordernumber = Lots 224, 232, 234, 280, 295, 296, 303, 310, 317, 324, 357, 367, 375
| totalproduction = 171
| gauge = {{Track gauge|ussg|allk=on}}
| whytetype = {{whyte|4-6-0}}
| uicclass = 2′C h4
| leadingdiameter = {{convert|3|ft|2|in|m|3|abbr=on}}
| driverdiameter = {{convert|6|ft|8+1/2|in|m|3|abbr=on}}
| minimumcurve = {{convert|8|chain|ft m}} normal,<br/>{{convert|7|chain|ft m}} slow
| length = {{convert|65|ft|2|in|m|2|abbr=on}} over [[buffer (rail transport)|buffers]]
| width = {{convert|8|ft|11|in|m|3|abbr=on}}
| height = {{convert|13|ft|4+1/2|in|m|3|abbr=on}}
| axleload = {{long ton|19|14}}<br/>{{convert|19|LT|14|lcwt|ST|disp=output only}} full
| weightondrivers = {{long ton|58|17}}<br/>{{convert|58|LT|17|lcwt|ST|disp=output only}} full
| locoweight = {{long ton|79|17}}<br/>{{convert|79|LT|17|lcwt|ST|disp=output only}} full
| tenderweight = {{long ton|47|6}}<br/>{{convert|47|LT|6|lcwt|ST|disp=output only}} full
| fueltype = [[Coal]]
| fuelcap = {{ubl|Churchward tender: {{convert|7|LT|t ST|1|abbr=on}}|Collett/Hawksworth tender: {{convert|6|LT|t ST|1|abbr=on}}}}
| watercap = Churchward tender: {{ubl|{{convert|3500|impgal|abbr=on}}|Collett/Hawksworth tender: {{convert|4000|impgal|abbr=on}}}}
| boilerpressure = {{convert|225|lbf/in2|MPa|2|abbr=on}}
| firearea = {{convert|29.36|sqft|m2|abbr=on}}
| boiler = GWR Standard No. 8{{sfnb|Champ|2018|p=320}}
| tubearea = {{ubl|{{convert|1857.7|sqft|m2|abbr=on}} (Collett)|{{convert|1799.5|sqft|m2|abbr=on}} (Hawksworth)}}
| fireboxarea = {{ubl|{{convert|162.7|sqft|m2|abbr=on}} (Collett)|{{convert|163.5|sqft|m2|abbr=on}} (Hawksworth)}}
| superheatertype = {{ubl|14-element "Swindon" (Collett)|21-element (Hawksworth)}}
| superheaterarea = {{ubl|{{convert|262.6|sqft|m2|abbr=on}} (Collett)|{{convert|295.0|sqft|m2|abbr=on}} (Hawksworth)}}
| cylindercount = Four (two inside, two outside)
| cylindersize = {{convert|16|x|26|in|mm|0|abbr=on}}
| valvegear = {{ubl|Inside cylinders: [[Walschaerts valve gear|Walschaerts]]|Outside cylinders: derived from inside cylinders via rocking bars.}}
| valvetype = [[Piston valve (steam engine)|Piston valves]]
| tractiveeffort = {{convert|31625|lbf|kN|2|abbr=on|lk=on}}
| operator = {{ubl|[[Great Western Railway]]|[[British Rail]]ways}}
| fleetnumbers = 4073–4099; 5000–5099; 7000–7037.
| powerclass = {{ubl|[[Great Western Railway Power Classification|GWR: D]]|BR: 7P}}
| axleloadclass = [[Great Western Railway Weight Classification|GWR: Red]]
| locale = [[Great Western Main Line]]
| withdrawndate = May 1950 to December 1965
| disposition = Eight preserved, remainder [[scrap]]ped
}}

The '''4073''' or '''Castle Class''' are [[4-6-0]] [[steam locomotive]]s of the [[Great Western Railway]], built between 1923 and 1950.{{sfnb |Nock |1980 |p=11}} They were designed by the railway's Chief Mechanical Engineer, [[Charles Collett]], for working the company's express passenger trains.<ref>{{Cite news |last=Bestwick |first=Alex |date=2024-01-08 |title=The history of GWR's 'Castle' Class, from design to preservation {{!}} The Railway Magazine |url=https://www.railwaymagazine.co.uk/27116/the-history-of-gwrs-castle-class-from-design-to-preservation/ |archive-url=http://web.archive.org/web/20240613212147/https://www.railwaymagazine.co.uk/27116/the-history-of-gwrs-castle-class-from-design-to-preservation/ |archive-date=2024-06-13 |access-date=2024-12-26 |language=en-GB}}</ref> They could reach speeds of up to {{cvt|100|mph}}.{{sfnb|Black|2017|p=45}}