Air-operated cab doors

[Deleted]

Do air-operated cab doors have their own door engines? Or do they share the engine of the saloon door they are closest to?

[Deleted]

They must have their own, as they can be left open while on the move, as long as the interlock is cut out...

[solidbond]

The only stock that shares any door engines between doors is the 73 stock. All other stock have independent door engines for each door. However, if you mean door valves, then most stock prior to the D stock share door valves between doors. Stock which have the ability to open doors independently of one another have separate door valves for each door. Cab doors are ALWAYS independent of the saloon doors, as there are many reasons why a cab door would need to be opened without opening a saloon door!

[jamesb]

At Leytonstone recently, I saw a Central Line train with just the first and last set of double doors closed, i.e. the ones adjacent to the cab doors at the front and back of the train.

Is this to keep the driver warm? Or was something wrong with them?!

[Deleted]

could be Selective Door Open Enabled [on the quiet, probably]

[jamesb]

Ah, maybe that was it. It just looked odd since it was just one set of doors closed at each end of the train, so caught my eye!

[Deleted]

jamesb said:

At Leytonstone recently, I saw a Central Line train with just the first and last set of double doors closed, i.e. the ones adjacent to the cab doors at the front and back of the train.

Is this to keep the driver warm? Or was something wrong with them?!

I saw a similar thing at Barking on a D one chilly winter morning for one of the first few trains out, and was eternally grateful to the op for keeping me warm[ish] while we waited to depart. I'm guessing it's the same use of SDO on the sly?

edit: it was something weird like every other door, rather than just the first and last, can SDO do that or was it some other kind of magic? The doors worked fine every other stop back to Bow

[towerman]

Selective close on C stock works on the principle of having one set of door valves per car fitted with a rectifier so when T/op selects selective close button and then opens the doors,it sends an AC feed through the open wire which only one pair of door valves per car will recognise.

[solidbond]

towerman said:

Selective close on C stock works on the principle of having one set of door valves per car fitted with a rectifier so when T/op selects selective close button and then opens the doors,it sends an AC feed through the open wire which only one pair of door valves per car will recognise.

Almost, but not quite It is the CLOSE circuit that has the rectifiers on the door valves, with one door valve, which works three of the four doorways, having the rectifier, while the other does not. Thus, if the selective close button is pressed, it sends an AC supply to the door valves, which the rectifier converts to DC and closes those doors, but the other door valve ignores (since it is expecting a DC supply) This is basically how selective CLOSE works on most stock from the C stock through to the D stock. Don't ask me about any of that new-fangled plastic stuff though ;D ;D

As to the end doors on trains remaining closed, that sounds like the driver used the end-door cut out buttons.switches to prevent the leading or rear doors from opening. C stock can only cut out the leading doors (and it would be the three doors closest to the driving cab) whilst D stock can have both the front and rear doors cut out, which would leave the first/last two doors closed.