GSR Class 670

On the amalgamation of the Dublin and South Eastern Railway (DSER) into the GSR in 1925 the former was found to be short of operational working motive power due to Irish Civil War, maintenance backlog and proportion of stock being life expired.[1]^:129–131 In the interim locomotives from outside the DSER area were used to cover the shortfall.

The commuter services to the south of Dublin were best served by a tank engine. The GSR chose not to continue with any DSER designs but created the GSR Class 850 design incorporating several modern features with a single example being built. The acute motive shortage was resolved by this 1933 design by A.W. Harty. It incorporated the modern type Z boiler used successfully elsewhere but many other features were considered conservative and retrospective compared to the class 850 and in practice they were more difficult to access for repairs and maintenance.[1]^:266–267

Harty also produced the GSR Class 710 which was a related design but with a tender.[1]^:266–267

The locomotives almost served exclusively on the Dublin—Bray—Greystones passenger commuter services, though they were also scheduled to work the Wexford Mail from Bray to Westland Row and once at least one of the class was noted in Wexford. They were noted for having some difficulty with timekeeping. A 1948 report noted their shortcomings but also noted they were essential for the suburban services they worked.[1]^:266–268

In 1934 two of the locomotives suffered read end collision damage at Bray. On repair their bunker was extended into the cab increasing coal capacity by about half a ton.[1]^:266–268

The carried standard GSR grey livery and painted side numbers from new, acquiring a CIÉ lined green passenger livery with repaints from 1948 onwards.[1]^:266–268

There is a detailed O Gauge model of engine 670 in the Fry model railway collection.[1]^:380