- British Rail Derby Lightweight
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British Rail Derby Lightweight 
Derby Lightweight power car no. 79018 on display at Bewdley on the Severn Valley Railway on 15 October 2004, as part of the Railcar 50 event. This vehicle has been restored to its original condition using a grant from the Heritage Lottery Fund, and is preserved at the Midland Railway - Butterley.In service 1954-1969 Manufacturer BR's Derby Works Number built 219 vehicles Formation 1, 2 & 4 Car Formations Operator British Rail Specifications Maximum speed 62 mph Weight 27 tonnes power car Traction system Mechanical Engine(s) Two BUT (AEC) 125 bhp except BUT (AEC) 150 hp for single units Multiple working ■ Yellow Diamond Gauge 1,435 mm (4 ft 8 1⁄2 in) Standard gauge 
Derby Lightweight trailer no. 975008 (79612) on display at Bewdley on the Severn Valley Railway on 15th October 2004, as part of the Railcar 50 event. This vehicle has yet to be restored to original condition, and is preserved at the Midland Railway - Butterley.
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, and four 4-car units. The two single car units were originally built as a two-car unit and then split two years later when demand came about. Contemporaneous with these units was the unique Battery Electric Multiple Unit.
Contents
Operations
The first units were introduced on services around the West Riding of Yorkshire, namely Leeds to Bradford services. Subsequent units were introduced onto services in Cumbria, Lincolnshire, Norfolk, and Birmingham to Sutton Coldfield, Bletchley to Buckingham and Banbury, and East London lines services.
These units were an outstanding success, helping to reduce the operating costs of branchlines. As such, 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 The last units were withdrawn from normal traffic in 1969.
Formations
Four different sorts of formation were created from the 217 cars built of this type, as follows:
Power Twins
DMBS DMCL DMBS DMCL 79000 + 79500 to 79007 + 79507 79184 + 79189 to 79188 + 79193
Power Trailers
DMBS DTCL DMBS DTCL 79008 + 79600 to 79033 + 79625 79034 + 79250 to 79046 + 79262 79118 + 79639 to 79141 + 79662 79142 + 79684 79143 + 79663 to 79149 + 79669 79169 + 79670 to 79181 + 79682
Four Car Units
DMS TBSL TSL DMC 79150 + 79325 + 79400 + 79508 79151 + 79326 + 79401 + 79509 79152 + 79327 + 79402 + 79510 79153 + 79328 + 79403 + 79511 79154 + 79329 + 79404 + 79512
Single Car Units
DMBS 79900 79901
79683 was left over as a spare DTCL, and took the place of 79649 in 1957, when this was converted into a special saloon. 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.
Powertrain
Power Twins
- Engine: Two BUT (Leyland) 125 bhp
- Transmission: Hydraulic, Lysholm Smith (Leyland) torque converter
- Coupling code: Red triangle
Others
- Engine: Two BUT (AEC) 150 bhp
- Transmission: Mechanical
- Coupling code: Yellow diamond
Departmental Use
A number of cars from these units were subsequently transferred to departmental (non-revenue earning) use after withdrawal from normal service:
- 79018 + 79612 were rebuilt as an ultrasonic test train based at Reading, numbered 975007 + 975008. Replaced by unit 901001.
- 79900 was rebuilt as test coach "Iris", based at Bletchley, numbered 975010. Later transferred to the BR Research Division at the Railway Technical Centre at Derby, for its last few years in traffic, it was repainted into original BR Green livery. Replaced by unit 901002.
- 79185 was taken into departmental use for brake trials, numbered 975012. It was scrapped in 1970.
- 79250 and 79252 were taken into departmental use as staff messrooms, numbered 975013 and 975014. They were scrapped in 1978 and 1982 respectively.
- 79649, the inspection saloon mentioned above, took its place in the departmental series as 999510.
Preservation
Derby Lightweight single car unit no. 79900 fully restored to passenger carrying standard again after being former test car IRIS. The unit now resides on the Ecclesbourne Valley Railway running regular passenger diagrams.Thanks to their extended life in departmental service, one 2-car unit and a single car unit survive in preservation, the former following a high-profile campaign.
Vehicle Nos. Location Comments In Service Departmental Nos. DMBS DTC DMBS DTC 79018 79612 Midland Railway - Butterley Used as ultrasonic test train. Part Restored/Not In Service 975007 975008 79900 - Ecclesbourne Valley Railway Used as test coach "Iris". Regularly in Passenger Service 975010 - External links
Media related to British Rail Derby Lightweight at Wikimedia CommonsDiesel multiple units of the United Kingdom First generation units: First Generation
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(pre-TOPS):British United Traction · Derby Lightweight · Metro-Cammell · Railbus · GWR Railcars · LMS Railcars
Second generation units: Diesel-electric units: Southern Railway designations: Families Categories:- British Rail diesel multiple units
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