1972 tube stock - drivers cab in the middle?

Discussion in 'London Underground' started by BanburyBlue, 18 Nov 2019.

  1. BanburyBlue

    BanburyBlue Member

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    Hi,

    Can someone tell me why there is an additional driver’s cab in the middle of a rake of 1972 tube stock?

    Ta.
     
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  3. Lewlew

    Lewlew Member

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    One "unit" of 1972 stock is made up of 4 cars.

    DM - T - T - DM
    Driving Motor / Trailer

    So it's two units joined together with 1 car removed to make one 7 car train. It's 7 cars because of platform lengths.

    The 3 car unit is formed of

    T - T - DM

    There is one 4 car unit that doesn't have a cab at one end, instead it has an UNDM - Uncoupling Non-Driving Motor (in other words, a motor car without a cab). This is formed from two units that had accidents and writing off a car (or multiple cars, can't remember) from each unit
     
  4. Dstock7080

    Dstock7080 Established Member

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    all 3-car units are formed:

    UNDM-T-DM
     
  5. Lewlew

    Lewlew Member

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    I actually wrote that first but got confused when I got to the 99 unit. Thanks
     
  6. bluegoblin7

    bluegoblin7 Member

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    So that’s the what, now for the why:

    When the 1972TS were procured, the practice of uncoupling during off peak hours still took place on the Underground, with shorter units running between the peaks allowing for increased maintenance time and decreased wear. This was a practice that had been around since the earliest days of electric traction, and (arguably!) didn’t finally die out until the Chesham shuttle ended in 2010.

    Which, of course, hints at another reason for shorter units that could be coupled together. Although not specifically relevant to the 72TS, several lines also operated self-contained shuttle services requiring shorter than full length trains - Aldwych, Ongar, Chesham and Woodford-Hainault all spring to mind. Indeed, the latter was assisted by the Victoria line’s 1967 stock being designed as four-car trains, despite being intended to always run as full length 8-car units. The design heritage of the 1972TS (essentially a manually-operated version of the 1967TS) gives some indication as to why this is also in ‘unit’ format.

    Finally, it is worth noting (although implied above it’s good to clarify things) that originally the middle cabs were fully operable as with the outer cabs. Refurbishments and new technology over the years has resulted in these not being upgraded to the same standard, and now cannot be used for passenger-carrying trains (on the Bakerloo some are maintained sufficiently to allow test running or stock transfers on the mainline, although I am not aware of any examples of this actually happening within the last decade).
     
  7. BanburyBlue

    BanburyBlue Member

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    Thanks - that was going to be the next question
     
  8. Lewlew

    Lewlew Member

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    Thanks for that @bluegoblin7

    With the last point about the middle cabs being used on the mainline, there are/were one or two with the fronts painted red (the rest being white) that were used to drag some units to Acton allowing the 4 car unit to return by itself to Stonebridge Park. This saved sending a whole 7 car train down as the whole lot would have had to have stayed there. But no idea when this was actually last done.
     
  9. bluegoblin7

    bluegoblin7 Member

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    Those trains retain their red fronts; as mentioned they haven’t been used for at least a decade. All recent transfers to Acton for life extension have been as complete seven cars (Stonebridge-Baker-Neasden-Harrow-Rayners-Acton)
     
  10. BanburyBlue

    BanburyBlue Member

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    So I’m probably stating the obvious, but I assume the 1972 stock weren’t originally planned for the Bakerloo? Based on the fact that platform lengths are for 7 car trains, and hence 2 units coupled together don’t fit!
     
  11. simple simon

    simple simon Member

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    The same type of train formation existed with the 1959 / 1962 tube stocks, the former had seven cars and the latter had eight cars (Piccadilly line / Central line), indeed the 4 + 3 format goes back to the Standard stock of the 1920's, which were also designed for uncoupling at quieter times. But these could also be used in different lengths, such as six cars on the Northern City line (and two cars off-peak).

    The Piccadilly line 1973 and Jubilee line 1983 tube stocks attempted to change this metric and go for slightly longer tube cars but with just six in a train (2x 3 car uinits). I am not sure that this has been a success, as overall train lengths are shorter and the Piccadilly could have done with the extra capacity. But the trains fit the platforms better. The Piccadilly line does have many 3 car units with drivers cabs at one end only and rudimentary shunting controls in the UNDM at the other end, this does add a little extra passenger capacity but only maybe 20 - 25 passengers per full length train (depending on how crush loaded they get). However there are some double cab units as the Aldwych service only needed 3 car trains.

    The Central line can take eight car trains because in the 1930's some platforms were lengthened. Ah, if only this could be done with other lines... money is an issue. Of course if a new line was built to siphon off some passengers then platform lengthening for longer trains would not be needed. Thats where Crossrail could help.
     
  12. bramling

    bramling Established Member

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    With a desire to go down to one man operation, reducing the train length was more or less essential at the time - as it is considered highly desirable for the driver’s cab side doors to be in the platform, and until relatively recently selective door opening was not mainstream.

    In crew operated days it was common for cabs to stop in the tunnel, and on lines like the Northern doors would be cut out by the press of a button - in some cases the motorman would cut out the front doors whilst at others the guard would cut out the rear doors. Under OPO none of this was desirable - although we did see some limited use of same for example on the Met at Euston Square or the District at Gloucester Road. It wasn’t uncommon to see doors open in the tunnel when the button press was forgotten.

    Now we have the luxury of automated SDO systems there is some viability to push the train lengths back out again, although this doesn’t resolve the problem of berth length at reversing locations where there may still be issues which need resolution - often at high cost.

    The prevalence of shorter trains happily coincided with a time when demand dropped, but could be said to have left us a slightly sour legacy in terms of capacity.
     
  13. philthetube

    philthetube Established Member

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    72 Stock doesn't have side cab doors, though the cab does need to be in the platform to allow mirrors and monitors to be viewed

    Does the third car on the three car units have a driving panel, I am pretty sure the ones on the Northern did.
     
  14. bluegoblin7

    bluegoblin7 Member

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    Shunting controls only, hidden away behind a panel.
     
  15. 100andthirty

    100andthirty Member

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    I'm sorry to report that the practice of uncoupling during the off-peak had ended by the time the 1972 tube stock was ordered. The 1972 mk1 tube stock was ordered for the Northern line, in a hurry when the reliability of the 1938 tube stock was poor and the line had been dubbed the "misery line". London Transport had only just been handed to the GLC to manage and the local politicians decided that "something must be done". The only tube stock that could be delivered quickly was a variant of the 1967 tube stock. In those days, the practice was to have the trains in two or more sections to facilitate dealing with faults by splitting out the defective unit for a good one. The Northern line needed 7-car trains and had to have "reversable units" as trains were routinely turned in the Kennington loop. The DM-T-T-DM-UNDM-T-DM configuration facilitated this in that the UNDM could couple to either end of a 4-car depending on the direction the UNDM was facing.

    This order was due to end before the production of the 1973 tube stock was due to start, and Metro-Cammell was threatening closure. As a result a further build of 1972 tube stock was authorised to fill the gap with the same configuration but with additional wiring for ATO for use on the Jubilee line when opened. They were initially deployed on the Northern line where the facility to reform the trains was useful.

    As the Bakerloo line has no facility to turn trains around, the middle cabs were largely decommissioned except to retain the ability to move the 4-car in depot. There is at least one set with a UNDM instead of the middle DM
     

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