nicklawford Wrote:When I joined the industry - on the Jubilee line - I was astounded to discover the north end of the Jubilee Line has mechanical interlockings (Westinghouse ''V'' frames). Not only the Jubilee, but a significant proportion of the entire London underground. In trying to understand why, a number of IRSE technical papers yield a lot of information.
Anyway the list of papers I found useful are in IRSE Proceedings as follows:
When I was new to the industry I went on a visit to the new Piccadilly line control centre (I think). Having been on BR for a bit I was well aware that plenty of mechanical interlockings left (a certain deputy chief of the Western Region and FIRSE told his graduates in 1981 that by the year 2000 there would be none left- that prediction turned out to be way off the mark!). What was suprising to me thought was at one end of the room there were computers (not sure quite what from memory perhaps PDP11s, certainly "filing cabinet" type), these drove outputs that seemed to be combined by some form of diode logic (I recall vertical busbars one side of a frame, horizontal busbars the other linked across as appropriate by big chunky diodes- reminded me of the capaictor discharge system I had implememented on a model railway for controlling the right combination of points having selected a route). Further down the room it was electic valves controlling compressed air that then physically operated the frame (and I think the locking was still purely mechanical). Seemed to go back from mid 1980s to mid 1880s as one walked down the room; someone who knows may say that it is still like that now. Of course one advanatage is that when there is a failure, then the trains can be kept running by taking the "air of the frame" and a person operating the rotating levers directly.
Re the IRSE papers; don't forget that, thanks to the Australians, you can purchase for an extremely reasonable sum (I think
PJW