London Underground 1972 Stock

The London Underground 1972 Stock is a type of rolling stock used on the London Underground. The units were originally ordered to make up the shortfall in trains on the Northern Line's 1959 Stock fleet, but they are currently used on the Bakerloo Line. Following the withdrawal of the Class 483 EMUs in 2021, the 1972 Stock are now the oldest EMUs in passenger service in the United Kingdom. A total of 63 seven-car trains were built in two separate batches.

 

 

Construction

---

A total of 441 cars were built by Metro-Cammell at Washwood Heath, in two batches: 30 Mark I units, and 33 Mark II units. Both are seven-car formations.

In the early 1970s, the 1938 Tube stock on the Bakerloo Line and Northern Line was life-expired and due for replacement. Tentative designs for a new Northern line fleet were abandoned when the go-ahead was given for the Piccadilly Line to be extended to Heathrow Airport. This required a totally new fleet of trains to replace the 1959 stock then in use. The plan was made to transfer the 1959 trains to the Northern, to allow the worst of the 1938 stock there to be scrapped, but there were only 76 1959 stock trains, and the Northern line needed more than that to operate. Originally, it was planned to refurbish around 30 of the 1938 trains, but this was scrapped in favour of 30 new trains of the 1972 Mark 1 Tube stock.

 

 

The 1972 Tube stock was ordered in a hurry, so there was no time to create a new design; the trains were based on the 1967 Stock on the Victoria Line. Although almost identical looking, the 1972 trains were conventionally operated with a guard and door controls in the rear car, and were not compatible with 1967 Tube stock. In later years some surplus 1972 Mark 1 cars were adapted to run with the 1967 trains on the Victoria line, being coupled in the middle due to the lack of ATO equipment.

A further 33 trains of 1972 Tube stock were ordered to provide service on the Northern line. The 1972 Mark 2 stock had slightly different interiors with a dark blue seating moquette, unlike the red and grey on the earlier 1967 and 1972 cars. The biggest external difference was that the doors were painted red, with a London Transport roundel on the side of the carriages, rather than the Johnston lettering.

The 1972 Mark 2 trains first operated on the Northern line alongside the 1972 Mark 1 trains. From the late 1970s, they were gradually transferred to the Bakerloo line and operated alongside the 1938 Stock until they began operating on the Jubilee Line when it opened in 1979. With the introduction of the first batch of 1983 stock on the Jubilee line in 1984, half of the 1972 Mark 2 trains were displaced back to the Northern line. After the introduction of a second batch of 1983 Stock on the Jubilee in 1987, all 1972 Mark 2 trains on the Jubilee and Northern lines were gradually converted to OPO and transferred to the Bakerloo line to displace the 1959 stock, where they remain in service.

In 1989, several Northern line Mark 1 units were painted in experimental liveries, and three trains were internally refurbished, before the refurbishment work was stopped because of the decision to order a new fleet. 3227 and 3518 were painted with blue doors and a white body, 3204 and 3522 were painted with a blue and white body, and 3202 and 3523 were painted in what would become a corporate livery. The earlier 1972 Mark 1 stock on the Northern line was replaced by 1995 Stock in 1999. After being withdrawn from the Northern line, a few cars of 1972 Mark 1 stock were converted to run with 1967 and 1972 Mark 2 stock in service on the Victoria and Bakerloo lines.

 

 

A further two trains were converted to be compatible with the Mark II type, and these now run on the Bakerloo line. One ex-Northern line set (3229) was based at the now-closed Aldwych station, for use in films until being sent to Ealing Common Depot in November 2021 and then Ruislip depot a month later. Another Mark 1 unit in a trial livery was sent to Acton Works to be used for shunting. One three-car unit (unit 3511) used to reside at Hainault depot until October 2018, where cars 4511 and 3411 had moved to Acton Works. The cab of unit 3511 had been fused onto unit 3538 following collision damage.

The 1972 trains are formed of seven-car sets and have a total of 268 passenger seats. After withdrawal from the Northern Line, five four-car units (units 3201, 3208, 3211, 3212 and 3230) were considered for use on the Waterloo and City line. The objective was to supply the Central line with extra 1992 stock. This never happened and the trains were sent to Mayer Perry or CF Booth of Rotherham to be scrapped.

Technical details

---

The 1972 Stock features a robust construction with a welded steel underframe, riveted aluminium frame, and aluminium alloy panelling. The exterior of the units was refurbished and painted in the London Underground corporate red, white, and blue livery. The stock rides on 4-wheel symmetrical plate frame bogies, which are constructed through a combination of welding and riveting. These bogies are equipped with wheels that have a diameter of 31 inches when new.

Coupling between units is facilitated by the London Underground Automatic Wedgelock system, while semi-permanent tray couplings are used between cars within a unit. The traction system consists of an A.E.I. Traction pneumatic single camshaft resistance controller, which operates with series and parallel grouping and includes two stages of weak field. The stock uses Brush LT115 axle-hung, nose-suspended motors with a 16/65 gear ratio, with four motors per driving motor car and one motor per driving axle. Each bogie has two motors connected in permanent series.

 

 

For air compression, the stock is fitted with either Reavell TBC38Z or Westinghouse 3HC43 reciprocating compressors, with one compressor located on each trailer. The braking system includes rheostatic brakes on driving motor cars and air-operated brake blocks on all cars. The service braking system employs a combination of rheostatic and staged electro-pneumatic (e.p.) braking with mercury retarders. Rheostatic braking handles all braking at low brake rates and low passenger loads, with air brakes on trailers and motor cars activated as the rate and load increase. Emergency braking is managed by e.p. and Westinghouse automatic air brakes, while the parking brake is an automatic spring-applied, air-released system.

The auxiliary power supplies include one A.E.I. Traction Motor-Alternator-Rectifier (MG3007) per trailer car. Additionally, two out of three trailers are equipped with a Sepsa static converter, which provides power for saloon ventilation fans, cab air conditioning, and charges an additional battery fitted to the UNDM in a 3-car unit.

Main lighting in the stock consists of 115V AC fluorescent tubes of various lengths: 12x5ft, 4x4ft, 4x2ft, and 4x’D’ tubes, with a slightly reduced number on driving motor cars. These lights are driven by inverters and powered by a 115V AC supply. Emergency lighting is provided by two of the 4ft tubes in each car, which are fed from a 50V DC supply, and all 2ft tubes in cars within 4-car units are similarly powered.

Refurbishment

---

The fleet was refurbished between 1991 and 1995 by Tickford at Rosyth Dockyard. From 2016 to 2018, the fleet was again refurbished at Acton Works to enable the trains to remain in service until their forecast replacement date of 2035. The class received the Class 499/2 designation on British Rail's TOPS system to operate on the Bakerloo line north of Queen's Park.

Future replacement

---

In the late 1990s, the Labour government initiated a public–private partnership (PPP) to reverse years of underinvestment in London Underground. Under the PPP contract, Metronet (the private consortium responsible for the Bakerloo line) would order new rolling stock for the Bakerloo line. This would take place following the delivery of 2009 Stock and S Stock trains, with an order for 24 new Bakerloo line trains. These would have entered service by 2019. However, Metronet collapsed in 2007 after cost overruns, and the PPP ended in 2010.

In the mid 2010s, TfL began a process of ordering new rolling stock to replace trains on the Piccadilly, Central, Bakerloo and Waterloo & City lines. A feasibility study showed that new-generation trains and resignalling could increase capacity on the Bakerloo line by 25%, with 27 trains per hour.

In June 2018, the Siemens Mobility Inspiro design was selected. These trains will have an open-gangway design, wider doorways, air conditioning and the ability to run automatically with a new signalling system. TfL could only afford to order Piccadilly line trains at a cost of £1.5bn. However, the contract with Siemens includes an option for 40 trains for the Bakerloo line in the future. This would take place after the delivery of the Piccadilly line trains in the late 2020s. Based on a November 2021 paper, due to a lack of funding, this might not happen until the late 2030s or early 2040s, when the trains would be 60 to 70 years old — likely double their design life. Since the withdrawal of the Class 483 on the Isle of Wight, the 1972-stock trains have become the oldest non-heritage trains running in the United Kingdom.