London Underground 1996 Stock
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| 1996 Stock | |
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| Manufacturer | Alstom |
| In Service | 1997-present |
| Lines Served | Jubilee |
| Length per car | 17.77m |
| Width | 2.629m |
| Height | 2.875m |
| Maximum Speed | 100 km/h (62 mph) |
| Weight | DM 30.0 tonnes UNDM 27.1 tonnes T 20.9 tonnes |
| Stock Type | Deep-level tube |
The fleet of 1996 Stock running on the London Underground's Jubilee Line is currently the second-most modern on the network (confusingly, the 1995 Stock on the Northern Line was delivered later than the 1996 Stock).
The 1996 Stock was bought to support the opening of the Jubilee Line Extension (JLE), which runs from Green Park to Stratford. However, delays in the JLE's opening meant that 1996 Stock was introduced, completely replacing the existing fleet of 1983 Stock, between Christmas Eve 1997 and July 1998 - over a year before the JLE was opened. The existing trains (1983 stock) were originally planned to be refurbished with the same exterior and interior as the new stock (1996 stock) even with double doors, but the cost proved prohibitive.
Both the 1996 Stock and the similar 1995 Stock found on the Northern Line were built by Alstom in Birmingham, The 1995 and 1996 stock have different seating layouts and cab designs. Other differences include different traction packages (Alstom ONIX system on 1995 Northern Line stock), Train Management Systems, slight differences with Tripcock geometry and the use of LED bodyside lights on the 1995 Northern Line Tubestock while 1996 Tubestock uses filament bulbs. The main technical differences occurred due to the fact that the Jubilee Line 1996 Tubestock was designed as "Cheapest first cost" for LUL, while the 1995 Northern Line Tubestock was designed for "Life Cycle Cost" as Alstom had won the contract to act as service provider and maintainer of this stock. Alstom subsequently won the maintenance of the Jubilee Line 1996 stock to be carried out at Stratford Market depot in East London.
The 1996 Stock is operated mainly with a dead man's handle at the driver's right hand. When the train is stopped the top of the handle is turned away from the position in which the driver holds it. To depart the driver turns the top of the handle and pushes the red lever forward. The trains were originally designed for automatic train operation as on the Victoria and Central Lines, although this will not be enabled until a signalling upgrade in some years' time (estimated for completion by 2009).
The original seat covers were a mauve and grey moqette. They formed the letter 'J' for Jubilee (also the Northern Line's moquete forms the letter 'N') during November 2005 the old cars were refurbished and these seat covers were replaced with the new dark blue Tube Lines moquette. This features multi-coloured and multi-size hollow squares. The new cars were ordered with this moquette. The Piccadilly Line's 1973 Stock also has this moquette. The armrests were purple but have been repainted blue to match the new seat covers. However, the new (mark 2) trains delivered in late 2005 were still carrying the old internal layout as of June 2006.
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[edit] Addition of seventh car
During early 2005 London Underground announced that it would be adding a seventh car to the trains of the existing Jubilee Line fleet, and also adding four new complete trains. So from December 25, 2005, the line was closed for completion of the seventh-car conversion, including signalling alterations and software modification to the platform edge doors on the JLE. The original plan was to hot-wire two cars so that the onboard computer would 'see' them as one car, but this proved not to be necessary. The platforms were already long enough for seven-car trains throughout the line, and the JLE platform edge doors had been built with space for a seventh car. The line was scheduled to close for five days, but the work by Alstom and Tube Lines was completed ahead of schedule, enabling the line to re-open two days early.
There were various differences between the new and old cars at the time of introduction:
- Amber Passenger information displays (PIDs) instead of red
- Black vestibule floor instead of grey
- Yellow strip on door seal
- Better fitted seat covers
- The ridged vestibule floor extends the width of the car
Many of these are likely to change as the old cars undergo refurbishment. The new cars are numbered 96601 to 96725 (odd numbers only). The door seal on the new cars still states '1996', because of the national production rules.
Following the introduction, an upgrade to the passenger information system has been introduced, resulting in next station announcements playing on approach to stations.
A simple way of noticing if you are in a new carriage is the noise of the doors sliding, it being quieter on the new stock. If you are in a new train, there is a noticeable difference of volume from the traction motors, again this is quieter on the new stock.
[edit] Traction control
1995 stock and 1996 stock have similar bodyshells and were both built by Alstom. However, they use different AC traction control systems. The control system on the 1995 stock is more modern than the 1996 stock, reflecting the fact that the latter's design spec was 'frozen' in 1991.
The 1996 stock uses three-phase induction motors fed from a single-source inverter using a GTO (gate-turn-off) thyristor, derived from those on Class 465 Networker trains. The 1995 stock, for comparison, uses Alstom's "Onix" three-phase Insulated Gate Bipolar Transistor drive.[1].
Earlier London Underground stock, like most electric trains until the 1990s, used DC motors. These are now regarded as inefficient, partly because they are traditionally controlled by resistors, and partly because a 3-phase AC induction motor can provide the same power at less size and mass.
However, in an AC motor, maximum torque can only be achieved when the resistance of the rotor windings equals the reactance. AC motors in an industrial setting tend to be operated more or less continuously and therefore large banks of resistors can be used on start-up to raise resistance and maintain torque. This would not be efficient in a small motor designed for stop/start operation.
As a result, it was only the invention of electronic control systems from the 1980s onwards that made AC traction viable for trains. The motor can be supplied using an inverter, and by varying the inverter's output frequency it is possible to keep the frequency of the currents flowing in the rotor windings constant, and hence the reactance (while resistance remains fixed).
The GTO thyristor used on 1996 stock achieves this by 'chopping' out short pulses of current, creating the characteristic audible whine associated with the stock and with the Class 465 networker trains that share its traction control system. The noise timbre changes as the pulse length changes. The noise is produced by the oxygen in the air vibrating as the magnetic field changes (oxygen is magnetic whereas nitrogen is not).
Modern AC traction, such as the 1995 stock, uses the IGBT (which is actually an amalgamation of a MOSFET and a transistor), which can switch very large currents very rapidly without damage. The 'whine' effect is far less noticeable.
[edit] Notes
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