British Rail Derby Lightweight

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.

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 The last units were withdrawn from normal traffic in 1969.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 Commons

• History of the Derby Lightweights