British Rail Derby Lightweight

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.
Body framing was extruded and riveted together. Paneling 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.
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 and Harrogate services from 14 June 1954. Subsequent units were introduced onto services in West Cumbria, Lincolnshire, Norfolk, Newcastle to Middlesbrough, Edinburgh to Glasgow 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 an outstanding success, helping to reduce the operating costs of branchlines. Initially they also attracted many more passengers. Between February and October 1956 on the London Midland, they carried 800,000 more passengers than steam 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). 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 The last units were withdrawn from normal traffic in 1969.
Table of orders and numbers
Lot No.	Type 	Diagram	Qty	Fleet numbers	Notes
30084 	Driving Motor Brake Second (DMBS) 	501 	8 	E79000–79007 	ER Power Twin sets
30085 	Driving Motor Composite with lavatory (DMCL) 	507 	8 	E79500–79507 	ER Power Twin sets
30123 	Driving Motor Brake Second (DMBS) 	503 	13 	M79008–79020 	LMR Power-Trailer sets
30124 	Driving Trailer Composite with lavatory (DTCL)	509 	13 	M79600–79612 	LMR Power-Trailer sets
30126 	Driving Motor Brake Second (DMBS) 	504 	13 	M79021–79033 	LMR Power-Trailer sets
30127 	Driving Trailer Composite with lavatory (DTCL)	505 	13 	M79613–79625 	LMR Power-Trailer sets
30177 	Driving Motor Brake Second (DMBS) 	504 	13 	M79034–79046 	LMR Power-Trailer sets
30178 	Driving Trailer Composite with lavatory (DTCL)	505 	13 	M79250–79262 	LMR Power-Trailer sets
30192 	Driving Motor Composite (DMC) 	502 	5 	E79508–79512 	ER 4-car sets
30193 	Driving Motor Second (DMS) 	508 	5 	E79150–79154 	ER 4-car sets
30194 	Trailer Brake Second with lavatory (TBSL) 	517 	5 	E79325–79329 	ER 4-car sets
30195 	Trailer Second with lavatory (TSL) 	518 	5 	E79400–79404 	ER 4-car sets
30201 	Driving Motor Brake Second (DMBS) 	633 	7 	M79143–79149 	LMR Power-Trailer sets
30202 	Driving Trailer Composite with lavatory (DTCL)	642 	7 	M79663–79669 	LMR Power-Trailer sets
30235 	Driving Motor Brake Second (DMBS) 	633 	9 	M79118–79126 	LMR Power-Trailer sets
30236 	Driving Trailer Composite with lavatory (DTCL)	509 	9 	M79639–79647 	LMR Power-Trailer sets
30240 	Driving Motor Brake Second (DMBS) 	633 	10 	M79127–79136 	LMR Power-Trailer sets
30241 	Driving Trailer Composite with lavatory (DTCL)	509 	10 	M79648–79657 	LMR Power-Trailer sets
30240 	Driving Motor Brake Second (DMBS) 	527 	4 	E79137–79140 	ER Power-Trailer sets
30241 	Driving Trailer Composite with lavatory (DTCL)	631 	4 	E79658–79661 	ER Power-Trailer sets
30246 	Driving Motor Brake Second (DMBS) 	633 	2 	M79141–79142 	LMR Power-Trailer sets
30247 	Driving Trailer Composite with lavatory (DTCL)	642 	1 	M79662 	LMR Power-Trailer sets
30321 	Driving Motor Brake Second (DMBS) 	633 	13 	M79169–79181 	LMR Power-Trailer sets
30322 	Driving Trailer Composite with lavatory (DTCL)	511 	15 	M79670–79684 	LMR Power-Trailer sets
30324 	Driving Motor Brake Second (DMBS) 	633 	5 	M79184–79188 	LMR Power Twin sets
30325 	Driving Motor Composite with lavatory (DMCL) 	509 	5 	M79189–79193 	LMR Power Twin sets
30380 	Driving Motor Brake Second (DMBS) 	514 	1 	M79900 	Single car unit; 61 seats
30387 	Driving Motor Brake Second (DMBS) 	515 	1 	M79901 	Single car unit; 52 seats
==Formations==
Four different sorts of formation were created from the 217 cars built of this type, as follows:
===Power Twins===
Qty	DMBS + DMCL 	 	DMBS + DMCL
8 	79000 + 79500	to	79007 + 79507
5 	79184 + 79189	to	79188 + 79193
===Power Trailers===
Qty	DMBS + DTCL 	 	DMBS + DTCL
26 	79008 + 79600	to	79033 + 79625
13 	79034 + 79250	to	79046 + 79262
24 	79118 + 79639	to	79141 + 79662
1 	79142 + 79684	 	
7 	79143 + 79663	to	79149 + 79669
13 	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 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.
==Powertrain==
===Power Twins 79000+79500 to 79007+79507===
*Engine: Two BUT (Leyland) 125 bhp
*Transmission: Hydraulic, Lysholm-Smith (Leyland) torque converter
*Coupling code: Red triangle
===Remainder of the fleet===
*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==
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.
Vehicle Nos.	Vehicle Nos.	Location 	Comments 	In Service 	Departmental Nos.	Departmental Nos.
DMBS 	DTC 	Location 	Comments 	In Service 	DMBS 	DTC
79018 	79612 	Ecclesbourne Valley Railway	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 	—
==See also==
*British Rail BEMU – a power-trailer two car EMU based on the Derby Lightweight DMU design.
Category:Derby Works locomotives
Category:United Kingdom
Category:British Rail locomotives
Category:British Diesel Locomotives
Category:Diesel trainsets