Built: 1960 by GM, La Grange Illinois works USA.
15 of these Bo-Bo locomotives were delivered to CIE in 1961, designated as the B Class, and first carried an unusual grey & yellow livery, quickly superseded by black & tan colours after 1962.
The 121s were the first GM locos to work on the Irish Rail system, and had an US style 'switcher' loco appearance with one single cab. The 121s ran bonnet first on trial, but after an accident early in their career they then ran cab front almost all the time. The locos displaced CIE steam engines entirely from mainline services, mainly to Cork, Sligo and Galway. In the mid-1970s, the class were fitted with multiple operation, with additional hand rails on the side walkways. In later years their passenger duties included operating suburban and cross country Mk3 push-pull trains. The last remaining 121 Class locos Nos.124 & 134 were withdrawn from service in March 2008. Both have been preserved by the ITG and RPSI respectively.
Max Speed: 77mph Weight: 64tons Length: 12.15m
Fitted for multiple operation with other GM locos (141+181)