British Rail Classes 44 - 46
The British Railways type 4 diesel locomotives were designed and built as part of the 1955 modernisation plan. The London Midland and Scottish (LMS) railway produced two diesel locomotives, numbered 10000 and 10001. These were to a very similar design, but contained English Electric traction equipment.
In 1959 the first BR type 4 emerged from Derby Locomotive Works numbered D1. This locomotive had Crompton Parkinson electrical equipment and a Sulzer 12LDA28 diesel engine. The huge plate bogies carried four axles of which three were driven; the leading axle was a pony axle intended to spread the weight of the locomotive. A further nine locomotives were built to this design (D2 - D10), all were designated class 44. They were all named after famous British Mountains, hence the term 'Peaks' which was applied not just to the first ten but the whole range.
The next series of locomotives were the class 45s, starting at D11. These were essentially uprated and slightly modified versions of their predecessors, with the Sulzer 12LDA28B diesel engine and uprated Crompton Parkinson electrical equipment. Construction of the 126 class 45s was shared between Derby and Crewe Works.
The final series was the Class 46, numbered D138 - D193, outwardly identical to Class 45 they had Brush electrical equipment.
Initially all of the 'Peaks' heated passenger trains by means of an onboard steam boiler fuelled by diesel fuel. 50 Class 45s were modified to Electric Train Heat (ETH), which entailed the fitting of an additional generator and removal of the steam heating boiler. These were designated Class 45/1 and spent much of their working lives on services to and from London St. Pancras.
The introduction of a computerised numbering system on BR in 1976 saw the 44s renumbered in order to 44001 - 44010 and the 46s to 46001 - 46056.
The 45s were renumbered completely at random becoming 45001 - 45077 and 45101 - 45150.
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