British Rail Class 46

The BR Class 46 Peak was a class of fifty-six 1Co-Co1 diesel-electric locomotives built at BR Derby between 1961 and 1963, powered by the Sulzer 12LDA28 twelve-cylinder engine producing 2,500 hp. The Class 46 was the third and final member of the Peak family — after the Class 44 (ten locomotives, 2,300 hp) and the Class 45 (127 locomotives, 2,500 hp) — and differed from the Class 45 primarily in using Brush rather than Crompton Parkinson electrical equipment.

The Peak name derived from the original ten Class 44 locomotives being named after mountains: Scafell Pike, Helvellyn, Snowdon, and others. The Class 45s and 46s were not named in service, though several Class 45s were later named after regiments.

The 1Co-Co1 wheel arrangement gave the Peaks considerable adhesion for their power output, making them effective on both passenger and freight duties. The Class 46s were primarily allocated to the Midland Main Line from London St Pancras to Sheffield and Derby, working express passenger services and heavy freight.

The Class 46s were withdrawn between 1977 and 1984, somewhat earlier than the Class 45s. The arrival of the High Speed Train on the Midland Main Line made the Peaks redundant on their principal express duties. Four examples survive in preservation, including the notable D172 Ixion and 46035 Ixion which represent the naming tradition applied to this locomotive during preservation.