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D Stock

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London Underground D Stock

The D Stock was introduced into passenger service from January 1980 and is the principal stock used for services on the District Line.  Remember that some District services are operated by C Stock borrowed from the Hammersmith and Circle Lines.   This page looks at the D Stock in some detail.  Most of the photos were supplied by District Dave.


D Stock - Design - Cab and Controls - Equipment - New Moquette - New Paint Job

D Stock

D Stock dd.jpg (31014 bytes)The first train of D Stock (Click on the image for the full size view of a D Stock at Ealing Common Depot by District Dave) entered service on the District Line on 28th January 1980.  The stock was built to replace the CO/CP and R Stocks then operating on the District.  There are a total of 75 x 6-car trains of D Stock.  Its official title is D78 Stock, the 78 indicating the year it was originally expected that the stock would enter service.

The trains were built by Metro-Cammell (now Alstom) in Birmingham and were towed by rail to the London Underground depot at West Ruislip.  They were then towed by CO/CP pilot units to Ealing Common where they were commissioned before entering service.  Tubeprune was involved in the commissioning of these trains.

D Stock interior.JPG (72981 bytes)D Stock interior

Click on the image for the full size view and description.



D Stock exterior.JPG (73262 bytes)D Stock exterior

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The D Stock is basically a surface stock version of the Piccadilly Line's 1973 Tube Stock.  It is formed into 3-car units which are usually coupled in pairs to provide a 6-car train.  The standard 3-car unit has a cab at one end and an uncoupling position (no cab) at the other end.  The units were designed with 65 units facing west and 65 units facing east.  Trains are formed by coupling units back to back.  A further 20 units were built with cabs at both ends to provide some flexibility in forming trains while single ended units were in maintenance.  Some of these were used as 3-car trains on the East London Line between April 1985 and May 1987.  At that time, the lower service levels on the District released some spare stock for the East London Line.  The current fleet is capable of providing 75 x 6-car trains.

The outer cars of each unit are equipped with traction control and motors and the middle cars are trailers.  The standard train 6-car train formation is therefore DM - T - UNDM + UNDM - T - DM.  A double ended 3-car unit is DM - T - DM.  These DMs have automatic couplers to allow coupling to UNDMs, whereas the single-ended DMs just have emergency mechanical couplers.  DM cars have 44 seats, Trailers and UNDMs have 48.  A full load, as classified by London Underground, is 1150 seated and standing passengers on a 6-car train.  The tare weight of the train is 144 tons.

Cars are numbered 7000-7129 (DMs), 7500-7539 (DMs in double-ended units with automatic couplers), 8000-8129 (UNDMs) 17000-17129 (trailers in single-ended units) and 17500-17538 (even numbers only for trailers in double-ended units).  The trailers are numbered to match the DMs in the unit in which they reside because they receive their 630 volt DC supply from that DM car.

Car Weight Seats Equipment
DM 27.4 tons 44 Cab Shoes Traction Package Emergency coupler¹ Motor Alternator   Batteries
T 18.4 tons² 48     Fan MA     Compressor  
UNDM 26.1 tons 48 Shunting controller Shoes Traction Package Auto coupler Motor Alternator   Batteries
¹Auto-coupler on double-ended DM cars.   ²Trailer in double-ended unit weighs 19.04 tons

Each car has four doorways on each side with a single leaf sliding door at each position.  The doorway opening is smaller than the traditional London Underground double doorway.  This was done to save money on door equipment but it means that the doorway is 1067mm (3ft 6ins) wide instead of 1372mm (4ft 6ins).  This slows the loading of the cars at busy stations.  At the time the stock was built, passenger numbers were declining on the Underground and were about 65% of the level today.  Nowadays, double doors would be more efficient.

D Stock cars barrier.JPG (42583 bytes)One very visible modification of the D Stock, which has also been applied to other lines, is the provision of inter-car safety barriers (Click on the image for the full size view and description.).   These first appeared on the Piccadilly Line in 1997 and were a response to the occasional accidents where passengers - usually those suffering from the effects of alcohol or drugs - have fallen between cars.  The barriers are made of black canvas and are hung on brackets fitted to the outer corners of the car body.  They are coupled between cars on sprung attachments to allow transition on curves without creating a gap or tearing.  They have become a maintenance problem.

D Stock bogie 1.jpg (85875 bytes)The D Stock has been fitted with new bogies (Click on the image for the full size view and description.) supplied by Adtranz (now Bombardier) of Derby.  These bogies are the flexible frame design also supplied for the 1995 Tube Stock on the Northern Line.  The original bogies were of an H frame design with welded box members and were a constant source of trouble because of fractures and derailments.  The problem with them was because LU track is not properly maintained and the construction of the bogie was too rigid to handle the track deformations which often occur around the system.  There were a number of derailments caused by wheel unloading on critical sections of track.  It is hoped that the new bogies will remove this risk.

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Cab and Controls

D Stock Desk.jpg (82802 bytes)D Stock Cab Control Desk

Click on the image for the full size view and labels.


The D Stock cab arrangement was a completely new design for London Underground.  It resulted from a suggestion by a driver that the existing controls were poorly laid out and induced fatigue.  The desk was arranged so that gauges were easily readable, the power/brake controller was operated by the right hand, heat did not get into the driver's eyes and the telephone handset was easily operated.  Any driver on the District Line will quickly tell you that the D Stock cab layout is a lot better than that of the C Stock, which is also used on sections of the District.

D stock Nearside Panel.jpg (68744 bytes)D Stock nearside control panel

Click on the image for the full size view and description.


At the outer end of each UNDM car, there is a shunting control cabinet which is used to allow the unit to be driven from the non-driving end at reduced speed in the depot.  The cabinet contains a set of miniaturised controls for selection of direction speed and braking.  There is also a whistle and an air gauge.  The cabinet is normally kept locked behind a panel on the left side of the car end panel.

D Stock Shunting Control Panel.jpg (38006 bytes)D Stock shunting controls.   These are similar to the original set up provided on the 1973 Tube Stock.  Of course, the ''73  panel has been replaced to allow an end window to be inserted as part of the refurbishment design.

Click on the image for the full size view and description.

There have been some modifications to the stock since it entered service.  When the trains first entered service, they were fitted with a forced ventilation system which was powered by fans mounted in the roof behind two long ventilator channels.  A special Fan Motor Alternator was provided on each trailer to drive them at 230 volts AC.  The fans were supposed to recirculate air inside the cars and it was calculated that this would provide sufficient ventilation to give a comfortable temperature inside the cars.  During the first summer of operation (1980), it quickly became apparent that this was not the case.  The interiors of cars became uncomfortably hot and stuffy, the problem being exacerbated by the use of passenger door control.  Passengers only open the doors required by them to enter or leave the car so, along the outer sections of line, some cars could run for several stations without any of the doors being opened.  In sunny weather, the interior temperature could rise to uncomfortable levels.

D Stock offside Panel.jpg (52261 bytes)D Stock offside control panel

Click on the image for the full size view and description.


The first modification was the introduction of a POGO switch.  This was a Passenger Open/Guards Open switch which allowed trains to operate with the passenger door opening facility withdrawn.  The doors would all open under the control of the guard when he operated the passenger open buttons in the cab.  This helped to cool down cars in the summer months.  Passenger open was restored in the winter.  The second was a new ventilation system and opening windows at some positions along each car.  The ventilation grilles along the car ceiling were reversed and a new type of fan fitted.  Car 7108 was delivered from the builders in June 1982 with these modifications as a trial and it was decided to modify the whole fleet.  The unit with car 7108 was returned to Metro-Cammell and all three cars (7108-17108-8108) were modified, together with the last unit to be built (8129-17129-7129) which was delivered in June 1983, exactly four years after the first unit was delivered to Ruislip.  The modifications to the fleet were completed in January 1985.

Shortly after the trains entered service, there were complaints about the lack of external grab handles to assist passengers boarding and alighting.  LU was against providing these at the time because they disrupted the cleaning  process as a train passed through the automatic washing machine.  However, handles were added at one doorway on each side of each car.   However, they had to be removed in 1990, after cases of hooligans being killed when they tried to hang onto the handles while the train was moving.

D Stock Cab wall No1 side.jpg (62124 bytes)D Stock offside rear cab wall

Click on the image for the full size view and description.


The original set up for the trains was for two-person operation.  The guard occupied the rear cab and controlled the doors from there.  The trains were converted to OPO in 1985.  The conversion consisted of minor switching modifications to the trains but required the installation of train radio and mirrors and CCTV cameras on stations.

3-car D Stock double-ended units provided the service on the East London Line between April 1985 and May 1987.  They became available because of the reductions in service introduced all over the Underground in the mid-1980s.  Their use on the ELL allowed the release of A Stock for conversion to OPO.  The D Stock was also converted at this time and the units on the ELL began OPO in service from May 1985.

D Stock Tower Hill Bay rd.JPG (36155 bytes)D Stock entering Tower Hill bay road on a Wimbledon reverser.

Click on the image for the full size view.

The door controls include Passenger Door Control (PDC) and Selective Reopen.  With passenger door control, the train operator can release the door controls so that passengers can open the door where they located while other doors remain closed.  It was popular with passengers during the winter but the poor ventilation of the D Stock made the inside of cars unpleasant at times, so PDC was not used during the summer.  Selective Reopen allows the train operator to reopen the doors on a car where a door has failed to close, without opening the doors on other cars.  This allows an obstruction to be cleared without the risk of further delay due to other passengers attempting to board the train.  At present, PDC is not used because there have been some incidents of misuse by passengers.

D StockTms.jpg (58562 bytes)The cab has a Train Management System (click on the image on the left for full size view and description) which monitors the operation of the essential equipment on the train.  The TMS box is mounted to the right of the end door and angled so that the display can be seen by the driver.  The TMS has a failure display light for each car.  If an item of equipment fails on that car, the car light is illuminated together with a light to indicate which item of equipment.  There are also isolating switches provided to allow the defective equipment to be switched out of operation.

The TMS was fitted as part of a programme of engineering improvements carried out on the D Stock during the years 1995-96.  The TMS replaced an earlier version of monitoring system called a Train Equipment Panel.   During the programme the trains were also equipped with "Correct Side Door Enable" (CSDE), to prevent the train doors being opened on the wrong side of the train.

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The D Stock is equipped with DC traction motors using a single, pneumatically driven camshaft for resistance control.  The traction circuit is arranged in a classic series-parallel configuration with weak field control.  Each of the two motor cars in a 3-car unit has four motors, giving 66% axles motored.  The two motors on one bogie are permanently connected in series.   The D Stock motors are type LT 118, built by Brush and drive the axle through a gear ratio of 17:75.  The low voltage traction control circuits are duplicated and arranged so that one set of control circuits operates one motor car whilst the other set operates the other motor car.  This set-up ensures that a low voltage control circuit failure will not disable the train.  Only 50% of control will be lost.

D Stock Power Schematic.gif (27781 bytes)Equipment schematic of D Stock showing simplified layout of systems.

Click on the image for the full size view and description.

Each 3-car unit has a single Westinghouse 3HC43 air compressor, except for the double ended units which have two compressors.   LU has a rule which requires that trains must only be allowed to operate in service with two functioning compressors.  The double-ended D Stock units can therefore be used as a 3-car train, as they were   on the East London Line.  Every car has a main reservoir supplied through the main line pipe.  Flow cut-off valves are provided each side of the intermediate semi permanent couplers on each unit.  The valves ensure that air pressure is preserved on each car even if the hose bursts.

Each motor car has a motor alternator (MA) providing 230 volts AC at 850Hz for auxiliary services.  The two MAs on a 3-car unit supply half the lighting on the unit, arranged so that all the lights down one side of the train are fed from one end and the other half from the other end.  This means that only 50% of the car lights are lost when the motor car supplying the MA passes over a current rail gap.  The MA recharges the battery on each motor car at 50 volts DC and supplies the control circuits at that voltage.  The D Stock also has an additional motor alternator supplying 230 volts at 50Hz for the unit's saloon ventilation fans.  This machine is mounted under the trailer car and runs when required by the temperature setting of the ventilation equipment.

D Stk Ecmdt 2.jpg (32669 bytes)D Stock at Ealing Common depot.

Click on the image for the full size view and description.

The D Stock is equipped with three braking systems - a spring applied parking brake, the Westcode electro-pneumatic brake and a dynamic brake.  The spring applied parking brake is automatic.  It will apply blocks to the motored axles if there is no brake cylinder air and main reservoir pressure falls below a pre-set level.  The only snag with it is that if main reservoir air is lost on a car or unit, the cars with SAPB applied have to be dragged with brakes applied.   The wheels will turn but you shouldn't go too fast for fear of overheating them.

The Westcode brake is an electrically controlled pneumatic 7-step brake system.  Only four steps are used on LU versions of the brake but the pneumatics are controlled by a 7-step relay valve on each car.   Using a combination of three control wires, the valve can provide seven levels of braking according to the wires which are de-energised.  If all wires are de-energised, or control supply voltage is lost, full emergency braking is called for.   The brake operates in conjunction with the dynamic brake.  The traction motors are used as generators to provide a rheostatic brake the train.  The energy produced is dispersed as heat in on-board resistors.  A blending system allows the rheostatic brake to provide the required level of braking on the motor cars with the Westcode air brake acting on trailers as necessary.  When the train reaches about 20 mi/h, the rheostatic brake starts to fade and the air brake takes over to provide the full braking effort required.

D Stock at Oly.jpg (61875 bytes)D Stock at Olympia

Click on the image for the full size view and description.

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D Stock lifted.jpg (68286 bytes)D Stock lifted in Ealing Common Depot

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The D Stock is now London Underground's most reliable stock, occasionally reaching 35,000 kms between service failures during some months.  The average yearly performance is close to 19,000 kms between failures but it is improving.  The difference is due to wild swings in the monthly performance.   The good performance is partly a result of the age of the stock, now 20 years, which is considered mature, partly because it is well understood by the operators and maintainers and partly because it has had a number of modifications to get better reliability.  It is also a design which had much of the equipment first tried on the Piccadilly Line, where it went through a shakedown period before modified versions were supplied for use on the D Stock.

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New Moquette

Since February 2002, more and more D Stock trains have been appearing in service with a new moquette.  It looks to Tubeprune as if it was designed by a pizza chef.  What do you think?  Photos by District Dave.

D Stock new uphol gen.jpg (82939 bytes)General view of the new seat covering in D Stock

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D Stock new uphol close.jpg (43560 bytes)Close up of the new moquette in D Stock

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New Paint Job

D stock 8008 - RB.jpg (49812 bytes)D Stock trailer car 8008 in trial repainting as seen at Ealing Common earlier this year.  Photo by Ray Bennett.

Click on the image for the full size view.

The D Stock is the only stock in passenger use on LU which has not been repainted into the corporate red, white and blue.  The stock was not part of the refurbishment programme in the early 1990s because it was considered not old enough to be done until after the rest of the fleet.  Since the completion of the rest of the fleet, money has not been available to do the work.

Over the last two years, a 3-car unit (7008 - 17008 - 8008) has been going through a trial refurbishment at Acton Works.  The result was shown to the public at Wimbledon at the end of January and the unit entered service a few weeks later. 

The three cars have been repainted in the corporate colours and one car, the trailer has been internally refinished with new upholstery and some cosmetic work.  The result - incorporating some District green and the new pizza flavoured upholstery - is pretty dreadful.  Tubeprune hopes that a professional designer will be called in to do a decent design before the refurbishment of the rest of the stock.

It is strongly rumoured that work on the rest of the fleet will start after the PPP contracts have been signed and that it will be carried out at Ilford.


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