GNRI Class Q

{{Short description|Great Northern Railway of Ireland 4-4-0 passenger steam locomotive class introduced 1899}}

{{Use dmy dates|date=April 2017}}

{{Use British English|date=April 2017}}

{{Infobox locomotive

|name = GNR(I) Q class

|powertype = Steam

|image = Whitehead Railway Museum - geograph.org.uk - 6289771 (cropped).jpg

|caption = GNR(I) No. 131 in the shed at Whitehead, 2019

|designer = Charles Clifford

|builder = Neilson, Reid & Co. (9),
North British Locomotive Co. (2),
Beyer, Peacock & Co. (2)

|ordernumber =

|serialnumber =

|buildmodel =

|builddate = 1899–1904

|totalproduction = 13

|rebuilder =

|rebuilddate =

|numberrebuilt =

|whytetype = 4-4-0

|uicclass = 2′B n2 (later 2′B h2)

|gauge = {{Track gauge|5ft3in|lk=on}}

|leadingdiameter =

|driverdiameter = {{convert|6|ft|7|in|m|3|abbr=on}}

|minimumcurve =

|wheelbase =

|length =

|width =

|height =

|axleload =

|weightondrivers =

|locoweight = {{long ton|49|4}}

|tenderweight =

|locotenderweight =

|tendertype =

|fueltype =

|fuelcap =

|watercap =

|tendercap =

|sandcap =

|boiler = {{convert|4|ft|6|in|m|2|abbr=on}} diameter

|boilerpressure = {{convert|175|psi|MPa|2|abbr=on}}

|feedwaterheater =

|firearea =

|tubearea =

|fluearea =

|tubesandflues =

|fireboxarea =

|totalsurface =

|superheatertype =

|superheaterarea =

|cylindercount = Two, inside

|cylindersize = {{convert|18|x|26|in|mm|0|abbr=on}}
later {{convert|18.5|x|26|in|mm|0|abbr=on}}

|valvegear =

|valvetype =

|valvetravel =

|valvelap =

|valvelead =

|transmission =

|maxspeed =

|poweroutput =

|tractiveeffort = {{convert|16755|lbf|kN|2|abbr=on}}

|factorofadhesion =

|trainheating =

|locobrakes =

|locobrakeforce =

|trainbrakes =

|safety =

|operator = GNR(I) → UTA & CIÉ

|operatorclass =

|powerclass =

|numinclass =

|fleetnumbers = 120-125, 130-136

|officialname =

|nicknames =

|axleloadclass =

|locale =

|deliverydate =

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|withdrawndate =

|preservedunits = No.131

|restoredate =

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|currentowner =

|disposition = One preserved, remainder scrapped

}}

The GNR(I) Q Class 4-4-0 steam locomotives of the Great Northern Railway (Ireland) (GNR) were mainly used on cross-border mixed traffic duties between Dublin and Belfast, as well as the "Derry Road" between {{rws|Portadown}} and Derry. It was designed for the GNR under the auspices of Charles Clifford and built by Neilson, Reid and Company, North British Locomotive Company and Beyer, Peacock and Company. The Q Class is slightly smaller than the GNR class S 4-4-0 {{Cite web |url=http://www.rpsi-online.org/locomotives/loco171.htm |title=Great Northern Railway (Ireland) "S" Class 4-4-0 No. 171 "Slieve Gullion" |access-date=4 May 2006 |archive-url=https://web.archive.org/web/20060505180811/http://www.rpsi-online.org/locomotives/loco171.htm |archive-date=5 May 2006 |url-status=usurped }} but powerful enough to haul a rake of eight or more carriages.

Faster running was achieved with the addition of superheated boilers and widened cylinders (under the supervision of G.T. Glover in the 1920s, and sometimes known as Qs class). In 1932 a two coach newspaper train hauled by No. 135 covered Howth Junction to Drogheda at a start-to-stop average speed of {{convert|67.06|mph|abbr=on}}, the fastest run in Ireland achieved with a steam locomotive on a scheduled train Journal of the Irish Railway Record Society vol 5, No 24, p103