GWR 2021 Class

{{Use dmy dates|date=February 2018}}

{{Use British English|date=February 2018}}

{{Infobox locomotive

| name = GWR 2021 Class

| image = Berkeley Road station geograph-2566416-by-Ben-Brooksbank.jpg

| caption = No. 2080 at Berkeley Road station 1948

| alt =

| powertype = Steam

| designer = George Armstrong

| builder = Wolverhampton, GWR{{sfn|le Fleming|1958|p=E50}}

| ordernumber = Lots: D3, F3, G3, H3, J3, K3, L3, M3{{sfn|le Fleming|1958|p=E50}}

| serialnumber = Works Nos: 625–764{{sfn|le Fleming|1958|p=E50}}

| buildmodel =

| builddate = {{Start date|1897}} – 1905{{sfn|le Fleming|1958|p=E50}}

| totalproduction = 140{{sfn|le Fleming|1958|p=E50}}

| rebuilder =

| rebuilddate =

| numberrebuilt =

| whytetype = {{whyte|0-6-0|ST}}{{sfn|le Fleming|1958|p=E50}}

| uicclass =

| gauge = {{Track gauge|uksg|allk=on}}

| driverdiameter = {{convert|4|ft|1+1/2|in|m|3|abbr=on}}{{sfn|le Fleming|1958|p=E50}}

| wheelbase = {{convert|7|ft|4|in|m|2|abbr=on}} + {{convert|7|ft|4|in|m|2|abbr=on}}, total {{convert|14|ft|8|in|m|2|abbr=on}}{{sfn|le Fleming|1958|p=E50}}

| length = {{convert|30|ft|1|in|m|2|abbr=on}} over buffers{{sfn|Whitehurst|1973|p=152}}

| width = {{convert|8|ft|2|in|m|2|abbr=on}}{{sfn|Whitehurst|1973|p=152}}

| height = {{convert|11|ft|10+3/8|in|m|2|abbr=on}}{{sfn|Whitehurst|1973|p=152}}

| frametype = {{plainlist|

• Type: Inside{{sfn|le Fleming|1958|p=E5}}
• Length: {{convert|25|ft|8|in|m|2|abbr=on}}
• Width: {{convert|7|ft|7|in|m|2|abbr=on}}{{sfn|Whitehurst|1973|p=152}}}}

| axleload = {{long ton|13|12+3/4}}
({{convert|13|LT|12+3/4|Lcwt|t ST|1|abbr=on|disp=output only}}) full{{sfn|le Fleming|1958|p=E50}}

| weightondrivers =

| locoweight = {{long ton|40|13+3/4}}
({{convert|40|LT|13+3/4|Lcwt|t ST|1|abbr=on|disp=output only}}) full {{sfn|le Fleming|1958|p=E50}}

| tenderweight =

| locotenderweight =

| tendertype =

| fueltype = Coal

| fuelcap =

| watercap = {{convert|1000|impgal|abbr=on}}{{sfn|le Fleming|1958|p=E50}}

| tendercap =

| sandcap =

| boiler = GWR 2021{{Cite book|last=Champ|first=Jim |title=An Introduction to Great Western Locomotive Development |year=2018|publisher=Pen & Sword Transport |isbn=978-1-4738-7784-9|location=Barnsley |oclc=1029234106 |ol=26953051M |page=319 }}

| pitch = {{Convert|6|ft|0+3/4|in|abbr=on}}{{sfn|le Fleming|1958|p=E50}}

| diameterinside = Barrel: {{Convert|10|ft|0|in|abbr=on}}
Outside diameter: {{Convert|3|ft|9+7/8|in|abbr=on}} and {{Convert|3|ft|9|in|abbr=on}}

| boilerpressure = {{convert|150|lbf/in2|MPa|2|abbr=on}}{{sfn|le Fleming|1958|p=E50}}

| feedwaterheater =

| firearea = {{convert|14.5|sqft|m2|abbr=on}}{{sfn|le Fleming|1958|p=E50}}

| tubearea = {{convert|926.25|sqft|m2|abbr=on}}{{sfn|le Fleming|1958|p=E50}}

| fluearea =

| tubesandflues =

| fireboxarea = {{convert|92.5|sqft|m2|abbr=on}}{{sfn|le Fleming|1958|p=E50}}

| totalsurface = {{convert|1018.75|sqft|m2|abbr=on}}{{sfn|le Fleming|1958|p=E50}}

| superheatertype =

| superheaterarea =

| cylindercount = Two, inside

| cylindersize = {{plainlist|

• Diameter: {{convert|16+1/2|in|mm|0|abbr=on}}
• Stroke: {{convert|24|in|mm|0|abbr=on}}{{sfn|le Fleming|1958|p=E50}}}}

| frontcylindersize =

| rearcylindersize =

| hpcylindersize =

| lpcylindersize =

| valvegear =

| valvetype =

| valvetravel =

| valvelap =

| valvelead =

| transmission =

| maxspeed =

| poweroutput =

| tractiveeffort = {{convert|16830|lbf|kN|2|abbr=on}}{{sfn|le Fleming|1958|p=E50}}

| factorofadhesion =

| trainheating =

| locobrakes = Steam{{sfn|le Fleming|1958|p=E11}}

| locobrakeforce =

| trainbrakes =

| safety =

| operator = Great Western Railway
British Railways

| operatorclass = 2021

| powerclass =

| numinclass = 140

| fleetnumbers = 2021–2160{{sfn|le Fleming|1958|p=E50}}

| officialname =

| nicknames =

| axleloadclass =

| locale = Western Region

| deliverydate =

| firstrundate =

| lastrundate =

| retiredate =

| withdrawndate = 1944–57{{sfn|Whitehurst|1973|pp=21-23}}

| preservedunits =

| restoredate =

| scrapdate =

| currentowner =

| disposition = All scrapped

| notes =

}}

{{Infobox locomotive

| name = GWR 2101 Class (differences from 2021 Class)

| axleload = {{long ton|14|6}}
({{convert|14|LT|6|Lcwt|t ST|1|abbr=on|disp=output only}}) full{{sfn|le Fleming|1958|p=E51}}

| locoweight = {{long ton|41|0}}
({{convert|41|LT|0|Lcwt|t ST|1|abbr=on|disp=output only}}) full{{sfn|le Fleming|1958|p=E51}}

| boiler = {{plainlist|

• Outside diameter: {{Convert|3|ft|10|in|abbr=on}} and {{Convert|3|ft|9|in|abbr=on}}{{sfn|le Fleming|1958|p=E51}}}}

| boilerpressure = {{convert|165|lbf/in2|MPa|2|abbr=on}}{{sfn|le Fleming|1958|p=E51}}

| firearea = {{convert|14.7|sqft|m2|abbr=on}}{{sfn|le Fleming|1958|p=E51}}

| tubearea = {{convert|958.32|sqft|m2|abbr=on}}{{sfn|le Fleming|1958|p=E51}}

| fireboxarea = {{convert|95.81|sqft|m2|abbr=on}}{{sfn|le Fleming|1958|p=E51}}

| totalsurface = {{convert|1054.13|sqft|m2|abbr=on}}{{sfn|le Fleming|1958|p=E51}}

| tractiveeffort = {{convert|18515|lbf|kN|2|abbr=on}}{{sfn|le Fleming|1958|p=E51}}

| operatorclass = 2101

}}

The GWR 2021 Class was a class of 140 {{whyte|0-6-0|ST}} steam locomotives. They were built at the Wolverhampton railway works of the Great Western Railway between 1897 and 1905. 1897 was the very year of George Armstrong's retirement, so it is uncertain if the design should be attributed to him or to his superior at Swindon, William Dean.

In fact the 2021s were simple enlargements of the Armstrong-designed 850 class of 1874. The changes were fundamentally confined to a longer wheelbase to permit fitting of a larger firebox.