GS&WR Class 400

The GS&WR 400 class, also known as CIE class B2 and B2a, was a class of ten 4-6-0 steam locomotives built for the Great Southern and Western Railway between 1916 and 1923 for express passenger duties on the Dublin to Cork main line. Designed under Locomotive Superintendent Edward Watson, they were the only four cylinder locomotives in Ireland and proved unreliable at first. A batch of three improved examples was built at the railway's Inchicore works in 1921, and two further batches of three were built and supplied by Armstrong Whitworth in 1922 and 1923, with a larger tender; the second of those batches had saturated boilers that later needed conversion to superheated boilers. Between 1927 and 1937 the seven survivors were rebuilt from four cylinders to two, which made them far more reliable, and the last two were withdrawn in 1961.