The 101s were by far the most numerous class of
locomotive (diesel or steam) ever to run in
Ireland with 111 being built between 1866 and 1903. The great majority were built by the
GS&WR at
Inchicore Works, though the construction of some examples was contracted out to
Beyer, Peacock & Company (12) and
Sharp, Stewart & Company (8). The design is attributed to
Alexander McDonnell, although evidence points to him developing the design from drawings supplied from
Beyer, Peacock and Company of Manchester, England. McDonell appears to have utilised the drawings and produced a number of
hybrids where parts were salvaged from a number of withdrawn locomotives from various builders; the
class 101 Inchicore Works creating locomotives broadly to the Beyer Peacock design from the withdrawn locomotives. The first three locomotives from Inchicore, Nos. 112 (June 1866), 113 (December 1866), and 118 (May 1867) are considered hybrids; recent analysis seems to indicate all nine Inchicore builds to No. 115 in October 1869 to be
hybrid builds. Eight Beyer Peacock built Class 101 were built between May 1867 and March 1868. Inchicore built Nos. 155 and 156 with short wheelbases ( less between the second and third axles, as per Nos. 114 and 115) in 1871 before commencing new builds of
standard locomotives with No. 159 in September 1871. Locomotive superintendents
John Aspinall (1883),
Henry Ivatt (1886), and
Robert Coey (1896) continued to build the standard 101, with few modifications until 1899. The original locomotives had cylinder sizes of , a boiler pressure of giving a tractive effort of . Modifications to new builds and respective fitting to older locomotives used a cylinder size of with boilers which could be pressurized to achieving an increased tractive effort of Coey followed this in 1902/03 with the final 12 locomotives that differed by having the enlarged boiler and a modified cab. These were initially designated the 200 class but were brought into the 101 Class when rebuilds of earlier locomotives were equipped with the same boiler. In 1925 the GS&WR were amalgamated with other railway companies whose territories did not extend into
Northern Ireland to form
Great Southern Railways (GSR), the GS&WR and Inchicore Works being the dominant party in the new concern. The 101 class generally kept to operating in the former GS&WR territory, the exception being the ex
Dublin and South Eastern Railway area where the locomotive stock was in poor condition due to under investment, civil war losses, and the inadequacy of
Canal Street Works. Members of the 101 class (among others) were therefore drafted in to assist commuter and other services for the DSER. Locomotive superintendents Bazin and Harty in 1929 and 1934 introduced fifteen locomotives of the
700 (J15a)and 710 (J15b) classes which were in some respects direct developments of the 101 class. They were in many ways little better, and the 710 class in particular somewhat worse, than the latest rebuilt versions of the 101 class with superheated belpaire boilers.
D&BJR In 1872 the
Dublin and Belfast Junction Railway (D&BJR) bought two locomotives from Beyer Peacock that were identical to those originally supplied to the GS&WR. On amalgamations these were to pass to the
Northern Railway of Ireland in 1875 as Nos. 40 and 41 and before absorption into the
Great Northern Railway in 1876, becoming designated Class "D". Reputed as "fine steaming engines" they were both given rebuilds 1888 and 1914 before being finally withdrawn in 1937 and 1934 respectively, the longest surviving D&BJR locomotives. ==Services==