London Underground 1996 Stock

The London Underground 1996 Stock is a type of rolling stock used on the Jubilee Line. The trains were built by GEC Alsthom-Metro-Cammell and entered service in 1997. They are externally similar to the 1995 Stock used on the Northern Line.

The original 59 trains were initially built as 6-car trains. In 2005, an additional trailer car was added to lengthen each train to 7-cars and four additional 7-car trains delivered, bringing the total to 63 7-car trains.

 

 

History

---

The 1996 stock was ordered for the Jubilee Line Extension (JLE) opening, stretching from Green Park to Stratford. Initially, there was a plan to extensively refurbish the original 1983 Stock to match the 1996 stock in appearance and interior, including replacing single-leaf doors with double doors. However, this plan was deemed too costly and was abandoned. Construction delays of the JLE led to the 1996 stock being put into service on the existing Jubilee line, replacing the 1983 stock, before the JLE was completed. The first train was delivered in July 1996 and began service on 24 December 1997, with the last train entering service on 31 July 2001, although this was several months after the rest of the fleet.

 

 

The development of the 1995 and 1996 stocks occurred simultaneously. Alstom conducted the detailed design at its Washwood Heath and Rugby facilities, and the first six train sets were manufactured at Alstom's Barcelona factory based on the 1996 stock design. These early train sets underwent all type approvals. The 1995 stock was then produced in the Barcelona factory, followed by the remaining 1996 stock. Final assembly and equipping took place at Alstom's Washwood Heath facility on adjacent production lines.

Overview

---

The 1996 Stock has an identical exterior car body to the 1995 Stock, but the two rolling stocks have different interiors, seating layouts and cabs (designed by Warwick Design Consultants), traction packages and train management systems, and slight differences in tripcock geometry. 1995 Stock units use LED body-side lights, 1996 Stock units use filament bulbs. The most apparent difference is the bogie: 1996 Stock uses an Alstom bogie with a rubber suspension, 1995 Stock has AdTranz bogies with air suspension to cope with the arduous track conditions of the underground portions of the Northern Line.

The main technical differences arose because 1996 Stock was designed for "cheapest first cost", while 1995 Stock was designed for "life cycle cost", as Alstom had won the contract to act as the service provider and maintainer of this stock. Alstom subsequently won the maintenance contract for 1996 Stock, to be carried out at the new Stratford Market Depot in East London.

The 1996 Stock was delivered as six-car trains, with two three-car units coupled together, each consisting of a Driving Motor car (DM), a Trailer car (T) and an Uncoupling Non-Driving Motor car (UNDM). The standard train formation was DM–T–UNDM+UNDM–T–DM. Twelve later trailer cars had de-icing equipment; these are referred to as De-Icing Trailer cars (DIT).

Addition of seventh car

---

Following implementation of the Public-Private-Partnership (PPP) on the Underground in 2003, Tube Lines planned to increase capacity on the Jubilee line by extending trains to 7 carriages. This would increase train capacity by 17%. The 1996 Stock had been future-proofed with the ability to add a seventh car, with platforms already long enough for seven-car trains and the platform-edge doors at the Jubilee Line Extension stations had been built with extra space.

 

Tube Lines ordered 87 carriages (59 additional carriages for existing 6-car trains and 4 new 7-car trains) from Alstom in June 2003 at a cost of £150m. The new carriages were manufactured in Alstom's new factory at Santa Perpètua de Mogoda, Barcelona, Spain - as the original factory on the Barcelona seafront had been closed. All carriages were delivered to Stratford Market Depot by November 2005.

 

 

To allow for the existing trains to be modified, fewer Jubilee line services were run in December 2005 before the entire line was closed from 25 December for 5 days to allow the conversion to be completed. Work involved signalling alterations, signage and software modification to the platform-edge doors. The work was completed ahead of schedule and the line reopened two days early on 29 December. The four new trains subsequently entered service in Spring 2006.

There were various differences between the new and old cars at the time of introduction:

Following refurbishment, many of these differences are no longer visible. The step-plate on the new cars reads "Alstom 1996" for continuity reasons, but they feature the newer Alstom logo instead of the original GEC-Alsthom.

Traction control

---

The 1995 and 1996 stock have similar bodyshells and were both constructed by Alstom. However, they utilize different AC traction control systems. The control system on the 1995 stock is more modern than that of the 1996 stock, as the latter's design specification was 'frozen' in 1991.

The 1996 stock employs three-phase induction motors powered by a single-source inverter using a GTO (gate-turn-off) thyristor, which is derived from those on Class 465 Networker trains. In contrast, the 1995 stock uses Alstom's "Onix" three-phase Insulated Gate Bipolar Transistor drive.

 

 

Earlier London Underground stock, like most electric trains until the 1990s, utilized DC motors. These are now considered inefficient, partly because they are traditionally controlled by resistors, and partly because a 3-phase AC induction motor can offer higher specific power and volumetric power density. The brushes and commutator of a DC motor require regular maintenance, whereas an induction machine does not have these components.

However, in an AC motor supplied by a fixed-frequency supply, maximum torque can only be achieved when the resistance of the rotor windings matches the reactance. AC motors in industrial settings are typically operated at a constant speed, and large banks of resistors can be used during start-up to increase resistance and maintain torque if a wound-rotor machine is used. This would not be efficient in a small motor designed for stop/start operation.

Consequently, it was only with the invention of electronic control systems from the 1980s onwards that AC traction became viable for trains. The motor can be powered using an inverter, and by varying the inverter's output frequency, it is possible to keep the frequency of the currents in the rotor windings constant, and thus the reactance. (Note that reactance depends on frequency, whereas resistance is fixed.)

The GTO thyristor used on the 1996 stock achieves this by 'chopping' the supply voltage to drive a sinusoidal current in the motor windings (PWM), creating the characteristic audible whine associated with the stock and the Class 465 units that share its traction drive system. The noise timbre changes as the pulse length varies. The noise is produced by the switching frequency current ripple and the resulting torque pulsation experienced by the rotor of the induction machine.

More modern AC traction, such as that used in the 1995 stock, employs the IGBT (which essentially combines the MOSFET and the BJT), capable of operating at much higher switching frequencies than the GTO. The 'whine' effect is much less noticeable due to the higher switching frequency of IGBT drives.

Upgrades & Refurbishment

---

The trains were originally delivered with seats with a mauve and grey moquette. They formed the letter J for Jubilee (the Northern line's moquette formed the letter N). This was replaced in November 2005 with the new dark blue Tube Lines moquette with multi-coloured and multi-size hollow squares, introduced at the same time on the 1973 and 1995 stock. At the same time, the purple armrests were repainted blue to match the new seats.

From April 2012, all units received a refresh, with the new Barman moquette being introduced on all units, prior to the 2012 Olympics.

 

 

From 2014 onwards, the external LCD destination displays were replaced with LED units. The new units use orange text, instead of the original yellow.

Starting in 2017, the 1996 stock underwent refurbishment, some 20 years after first being introduced. New flooring was fitted, with contrasting colours and grooves in the doorways. All grab rails were repainted Jubilee line silver, and new wheelchair backboards were provided in some trailer cars. The interior turquoise blue panels were also repainted white. The external door open/close buttons were also plated over. The first refurbished train entered service on 23 February 2017, and the last one entered service in December 2019, which means that all trains have now been refurbished.

Automatic train operation

---

It had been intended to open the Jubilee Line Extension with an automatic train operation (ATO) system, however delays and technical difficulties meant that a conventional signalling system was hastily installed, and until 2011 the trains were always driven manually by the driver using a dead man's handle, also known as the Traction-Brake controller.

Eventually, from 2009 a new signalling system was installed by Thales, called SelTrac. Also known as Transmission-based train control, it allows the trains to be operated automatically, with the driver only responsible for opening and closing the doors, and initiating departure. The system uses inductive track loops, placed between the running rails, to communicate with the train. In order to operate with the new signalling system, all 1996 stock underwent modification, which included the installation of two Vehicle On Board Controllers (VOBC), and a new Train Operators Display (TOD) in the cab.

From the beginning of January 2011, ATO was introduced on a gradual basis, and since 26 June 2011, the line has been operated entirely under ATO. As a result, the peak service frequency was increased to 27 trains per hour in July 2011, and it has since been increased further to 30 trains per hour.