GNR Small Boiler Single

The GNR Small Boiler Singles refers to the series of 2-2-2 and 2-4-0 express locomotives designed by Patrick Stirling and built at Doncaster Works for the Great Northern Railway from around 1866 to 1876, before his celebrated 8-foot Single of 1870 and during the transitional period when Stirling was establishing his design philosophy at Doncaster. These earlier Stirling designs used smaller boilers and driving wheels than the famous 8-foot Singles that followed, and are distinguished from the larger 1870–1895 series by the absence of the 8 ft 1 in driving wheel that defined the later class.

Patrick Stirling had taken over from Archibald Sturrock as GNR Locomotive Superintendent in 1866 and immediately began replacing the eclectic mixed fleet he inherited with his own standardised designs. His early GNR express engines in the late 1860s used 7 ft or 7 ft 6 in driving wheels — still large by contemporary standards — and the domeless boiler arrangement that would become his trademark throughout his career. These smaller-boiler singles gave Stirling the operational experience on the GNR main line that informed his decision to go larger still with the celebrated 8-footer of 1870.

The small-boiler Singles were progressively superseded by the 8-foot Singles as the larger class demonstrated its superiority, and later rebuilt or withdrawn. None survives in preservation; the GNR Stirling express tradition is represented entirely by the celebrated No. 1 (8-footer, 1870) at the National Railway Museum in York.