The British Rail Derby Lightweight diesel multiple units, were the first such trains to be built en-masse for British Railways. The units were built at BR's Derby Works from 1954 to 1955. The units were built in various formations, including 12 power-twin 2-car units, 84 power-trailer 2-car units, four 4-car units, and two single car units.
Body framing was extruded and riveted together. Panelling was welded into continuous sheets and riveted to the frame. Luggage racks were light alloy. The floors had 2 layers of flameproof hardboard, covered with linoleum. To reduce noise and condensation, the inside structure and undersides were sprayed with asbestos. Lighting was by 60-watt, 24-volt lamps charged by belt driven dynamos. Heating was oil fired. Standard mild steel bogies ran on Timken roller bearings.[1]
Contemporaneous with these units was the unique Battery Electric Multiple Unit.
The first units were introduced on services around the West Riding of Yorkshire, namely Leeds to Bradford and Harrogate services from 14 June 1954.[2] Subsequent units were introduced onto services in West Cumbria, Lincolnshire, Norfolk, Newcastle to Middlesbrough, Edinburgh to Glasgow[3] and, later, Birmingham to Sutton Coldfield, Bletchley to Buckingham and Banbury, and East London lines services. They were also the last units to run on the Anglesey Central Railway which closed to public traffic in 1964.
These units were extremely successful, helping to reduce the operating costs of branchlines and also attracting many more passengers when new. They carried 800,000 more passengers on the London Midland Region between February and October 1956 than steam did in the same period of 1955. The largest increase was 434% (4,772 passengers) on the Buckingham-Banbury line (from 13 August), followed by Birmingham-Lichfield 178% (from 5 March), Bury-Bacup 152% (from 6 February), Llandudno-Blaenau Ffestiniog 39% (from 5 March) and Manchester-Buxton 38% (from 8 October).[4]
Due to their success, British Railways ordered many more DMU vehicles from various builders over the next decade, thus helping to eliminate steam locomotives. However, as these units were non-standard compared to other later DMU vehicles, they were subject to early retirement. The last units were withdrawn from normal traffic in 1969.
Four different sorts of formation were created from the 217 cars built of this type, as follows:
79683 was left over as a spare DTCL, and took the place of 79649 in 1957, when this was converted into a special saloon on diagram 565. It was later renumbered 999510 in the departmental saloon series and was eventually scrapped in 1981.
In 1962 three of the power twin units were converted to power trailer units, when 79191–79193 were rebuilt as DTCL vehicles and renumbered 79633–79635.
A number of cars from these units were subsequently transferred to departmental (non-revenue earning) use after withdrawal from normal service:
Thanks to their extended life in departmental service, one 2-car unit and a single car unit survive in preservation on the Ecclesbourne Valley Railway, the former following a high-profile campaign.
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