DSER 20

{{short description|Irish class of locomotive}}

{{Use Irish English|date=March 2019}}

{{Use dmy dates|date=March 2019}}

{{Infobox locomotive

| name = DSER 20, 34 & 35

| image = Irish 4-4-2T (46518266611).jpg

| alt =

| caption = 457 (former DSER 35) at Bray

| powertype = Steam

| designer = Cronin

| builder = {{ubl|Grand Canal Street|Beyer, Peacock & Company}}

| ordernumber =

| serialnumber =

| buildmodel =

| builddate = 1911 & 1924

| totalproduction = 3

| rebuilder = Inchicore railway works

| rebuilddate = 1932–1951

| numberrebuilt =

| whytetype = 4-4-2T

| uicclass =

| driver =

| gauge = {{track gauge|Irish}}

| leadingdiameter = {{convert|3|ft|3|in|mm|abbr=on}}

| driverdiameter = {{convert|6|ft|1|in|mm|abbr=on}}

| coupleddiameter =

| trailingdiameter = {{convert|3|ft|39|in|mm|abbr=on}}

| tenderdiameter =

| minimumcurve =

| wheelbase =

| engine total =

| leading =

| drivers =

| coupled =

| trailing =

| tender total =

| tendertruck =

| tenderbogie =

| pivotcentres =

| wheelspacing =

| length =

| over couplers =

| over bufferbeams=

| width =

| height =

| frametype =

| axleload = {{convert|15.75|LT|MT}}

| leadingbogie/pony=

| coupled all =

| coupled 1 =

| coupled 2 =

| coupled 3 =

| coupled 4 =

| coupled 5 =

| coupled 6 =

| coupled 7 =

| coupled 8 =

| trail bogie/pony=

| tenderbogieload =

| tenderaxle =

| weightondrivers =

| locoweight = {{convert|61.5|LT|MT}}

| tenderweight =

| locotenderweight =

| tendertype =

| fueltype =

| fuelcap =

| watercap = {{convert|1700|impgal|abbr=on}}

| tendercap =

| sandcap =

| fireboxtype =

| firearea =

| boiler =

| boilertype =

| pitch =

| diameterinside =

| lengthinside =

| smalltubediameter=

| largetubediameter=

| boilerpressure = {{convert|160|lbf/in2|MPa|2|abbr=on}}

| safetyvalvetype =

| feedwaterheater =

| totalsurface =

| tubearea =

| archarea =

| fluearea =

| tubesandflues =

| fireboxarea =

| superheatertype =

| superheaterarea =

| cylindercount = 2

| cylindersize = {{convert|18|x|26|in|mm|0|abbr=on}}

| frontcylindersize=

| rearcylindersize =

| hpcylindersize =

| lpcylindersize =

| valvegear =

| valvetype =

| valvetravel =

| valvelap =

| valvelead =

| transmission =

| trainheating =

| locobrakes =

| locobrakeforce =

| trainbrakes =

| safety =

| coupling =

| maxspeed =

| poweroutput =

| tractiveeffort = {{convert|15920|lbf|kN|2|abbr=on|lk=on}}

| factorofadhesion =

| operator = {{ubl|Dublin and South Eastern Railway|Great Southern Railways|CIÉ Railways Division}}

| operatorclass = C2 (Inchicore)

| powerclass = K/HT

| numinclass = 3

| fleetnumbers = {{ubl|20, 34, 35|455-457}}

| officialname =

| nicknames =

| axleloadclass =

| locale = Ireland

| deliverydate =

| firstrundate =

| lastrundate =

| retiredate =

| withdrawndate = 1955-1959

| preservedunits =

| restoredate =

| scrapdate =

| currentowner =

| disposition = All scrapped

| notes = No. 20 as built

}}

The DSER 20 class was a class of three 4-4-2T locomotives operated by the Dublin and South Eastern Railway and later the Great Southern Railways and CIÉ.