British Rail Class 48

The BR Class 48 was a small group of five Co-Co diesel-electric locomotives built by Brush Traction in 1965 as a variant of the Class 47, powered by the Sulzer 12LVA24 engine rather than the 12LDA28 used in the standard Class 47 fleet. The distinction was a consequence of Sulzer’s parallel development of two different twelve-cylinder engine families in the early 1960s: the 12LDA28 (a straight twelve-cylinder used in the Class 47) and the 12LVA24 (a V-form twelve-cylinder offering a different power–weight characteristic). BR ordered five locomotives with the LVA24 engine to evaluate its comparative performance against the standard LDA28 installation in identical operating conditions.

The five locomotives — D1702–D1706 — were delivered in 1965 and allocated to Bristol Bath Road depot for evaluation on Western Region services. The 12LVA24 produced 2,650 hp, marginally more than the standard 12LDA28-powered Class 47's 2,580 hp, but the evaluation concluded that the performance advantage did not justify maintaining a separate engine type in the fleet. Sulzer’s own development priorities also shifted during this period, and the 12LVA24 was not chosen for further BR orders.

In 1971 BR converted all five Class 48 locomotives to standard Class 47 specification, replacing the LVA24 engines with the standard LDA28 units and reclassifying the locomotives as Class 47s. The Class 48 ceased to exist as a distinct class after these conversions, and the five locomotives — renumbered into the standard Class 47 fleet — continued in service alongside the other 512 Class 47s until withdrawn in the normal course of fleet rationalisation. None was preserved as a Class 48, though one or more of the converted examples may survive as preserved Class 47s without specific acknowledgement of their Class 48 origin.