GS&WR McDonnell 2-4-0

Alexander McDonnell joined the GS&WR as locomotive superintendent in 1864, replacing John Wakefield.[3] McDonnell brought experience from the London & North Western Railway at Crewe and was impressed by the designs being produced by Beyer, Peacock & Company of Manchester at that time.[4] McDonnell used designs from Beyer Peacock as the basis for the GS&WR Class 101 0-6-0 goods locomotive which was to become the most numerous type in Ireland.[2] The Dublin to Cork express services were powered by Wakefield's 2-2-2 locomotives and McDonnell in 1968 again turned to Beyer-Peacock drawings to direct Inchicore to produce six passenger express 2-4-0 locomotives with 6-foot-6-inch (1.98 m) driving wheels and 16-by-22-inch (410 mm × 560 mm) cylinders for express passenger work.[2]

A smaller design suitable for secondary passenger duties with 5-foot-8-inch (1.73 m) wheels and 15-by-22-inch (380 mm × 560 mm) cylinders was produced from 1869. While McDonnell aimed for standardisation locomotives were sometimes included parts reclaimed from scrapped locomotives for economy reasons. Additional batches of both the express and secondary types were built with a number of variations.[2]

The larger 2-4-0 locomotives were all withdrawn before the start of the twentieth century,[5] Three of the lighter type built in 1873 survived until amalgamation to Great Southern Railways in 1925 though were withdrawn shortly thereafter in 1928.[6]

All the locomotives were constructed at Inchicore and utilised a maximum boiler pressure of 140 lbf/in² (0.97 MPa).[2]

McDonnell developed the lightweight 2-4-0 into the Kerry bogie 4-4-0 in 1877 with the addition of a swing-link bogie mechanism used in American practice.[8] Henry Ivatt later used the lightweight design as the basis for his 2-4-2T tank locomotives. The larger express passenger locomotive was a predecessor to the Aspinall GS&WR Class 52 and 60, which in turn led through to the Robert Coey 4-4-0 passenger locomotives.[9]