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Post by tube10 on May 9, 2006 18:03:49 GMT
What type of trip arms are used for controlling the underground train speed?
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Post by c5 on May 9, 2006 19:24:37 GMT
At terminus stations where the line stops (like Wimbledon), there are Speed Controlled Trainstops, also known as "Sleeping Policeman" at track level that on lower once the train is at the correct speed, say 5mph. It does this by timing the approach section.
There is no stop signal associated with this trainstop.
So if the train is going too fast for the timing section, the train will be "tripped" in the same way as Passing a Signal at Danger.
Hope this anwers your question fairly well.
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Post by Deleted on May 9, 2006 19:27:29 GMT
The trainstops used to control the speed of the train are referred to as "blind" trainstops, or "policemen".
These trainstops are commonly located on dead-end platform tracks or tracks where the signal in advance of an approaching train has a compromised or short overlap. They were put in place following the Moorgate crash of 1975, and are designed to force a driver to slow down when approaching a dead end, or a signal that, if passed at danger, could have trains approach too closely to one another with the risk of collision. They can also be used in other instances which vary from site to site.
These trainstops are attached to a timer which is actuated when a specific track circuit is de-energised by the presence of a train. When the train starts the timer, it must reach the next track circuit in the sequence after the timer has expired; if it does, then it has reduced speed correctly and the blind trainstop will lower. If the train actuates the next track circuit before the timer expires, it is going too fast and the trainstop will stay up, thus causing the train to be tripped.
A variant of the policeman is referred to as a timing signal; this type of signal has three aspects and is commonly associated with a standard two-aspect signal. It works as follows, when the main signal is red:
- when the main signal is red, the timing signal is red and its trainstop is up
- when a train approaches and actuates a track circuit, a timer starts and the timing signal displays both a red and a yellow aspect
- when the train actuates the next track circuit after timer expiration, the trainstop lowers and the timing signal changes to yellow
- the train can now pass the timing signal safely and approach the main signal.
When the main signal is green, the timing signal also changes to green and the trainstop lowers. When the overlap in advance of the main signal is no longer compromised, the timing signal can clear immediately to yellow if the main signal is red.
This type of signal can be independently cleared alongside the main signal, and is commonly used to provide a signalman control over the overlaps for a signal. They are used in all four platforms at Earls Court for that purpose.
fx: stampede of T/Ops and signalman and AETs...
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Post by c5 on May 9, 2006 19:36:21 GMT
That sounds more or less right on to me OneKea. They also work off their own timmim circuits rater than track circuits, me thinks  For the last bit, I think you talking about Draw Up signals, which generally are Automatic- Treated as Semis signals used to (as you say) slow trains down. They are provided when the fouling point for a set of points is close to another Signal. At (uses Edgware Road C&H as an easy example) all platforms apart from pfm2 w/b have draw-ups because the Staters are close to the pints they are protecting.  I think the expertise of a T.O. is needed! |
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Post by Deleted on May 9, 2006 19:53:54 GMT
That sounds more or less right on to me OneKea. They also work off their own timmim circuits rater than track circuits, me thinks What a relief  That's the part I'm a bit unsure about - I know some of them use track circuits and timers, but I think others use induction rails and yet others might even use other weird stuff! For the last bit, I think you talking about Draw Up signals, which generally are Automatic- Treated as Semis signals used to (as you say) slow trains down. They are provided when the fouling point for a set of points is close to another Signal. At (uses Edgware Road C&H as an easy example) all platforms apart from pfm2 w/b have draw-ups because the Staters are close to the pints they are protecting. Of course. I couldn't think of the name "draw-up signal" for some strange reason. And you are correct, of course - Edgware Road C&H is another fine example of draw-up signals. I think the expertise of a T.O. is needed! Where's BAET and citysig! |
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Post by c5 on May 9, 2006 19:58:38 GMT
That sounds more or less right on to me OneKea. They also work off their own timmim circuits rater than track circuits, me thinks What a relief That's the part I'm a bit unsure about - I know some of them use track circuits and timers, but I think others use induction rails and yet others might even use other weird stuff! Of course. I couldn't think of the name "draw-up signal" for some strange reason. And you are correct, of course - Edgware Road C&H is another fine example of draw-up signals. I think the expertise of a T.O. is needed! Where's BAET and citysig! I forgot to say that Draw Up signals can be easily identified by having extra 0's added to ther ID, ie signal EC12 would become EC120 and EC4 would become EC400. citysig isn't a T.O. but he might know a tad more |
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Post by Deleted on May 9, 2006 20:19:18 GMT
your right most of the time draw up signals do indeed have a extra 0 on the end
inductor rails are part of speed control but its rare these days for half of them to work as due to the lack of parts if the train fails the inductor or the inductor simply is not working then it depends on the site how the ' get out ' circuit works either by the means of that particular track being down for either 4 1/2 secs or 15 secs or operate a special circuit which is called a delta which simply is a track circuit within a track circuit
other forms of speed control usually found at junction signals is the approach track has to be proved down (no time delay)
whitechapel uses the old form of slugging a trainstop which is controlling the speed by the means before the arm goes down the air has to feel a bit of pipe first then when its full up theres another pressure to release the arm to the lowered or off position
not all drawn up signals are treated like semi's the first one that springs to mind is the one in the w/b platform in cannon street think its number is A8400 could be wrong on the number though
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Post by russe on May 10, 2006 1:19:05 GMT
I'm trying to get my head around these timing signal things. Would I correct in assuming that timing signals and draw-up signals are used as an 'inner home' function (as opposed to starters)?
Russ
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Colin
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Post by Colin on May 10, 2006 5:45:31 GMT
This type of signal can be independently cleared alongside the main signal, and is commonly used to provide a signalman control over the overlaps for a signal. They are used in all four platforms at Earls Court for that purpose. They are only used in platforms 1 and 3 at Earls Court - platforms 2 and 4 do not have draw ups I'm trying to get my head around these timing signal things. Would I correct in assuming that timing signals and draw-up signals are used as an 'inner home' function (as opposed to starters)? Russ No, draw up's are not home signals - they are normally used to protect junctions where the last signal does not provide a full speed overlap. There are exceptions, like A8400 at Cannon Street westbound- though I suspect that particular one is to allow a train to draw up in the platform while a train is standing at EG1, the Mansion House westbound home signal. |
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Post by citysig on May 10, 2006 6:18:59 GMT
I think the expertise of a T.O. is needed! Where's BAET and citysig! citysig isn't a T.O. but he might know a tad more Yes thank you C5. Mr OneKea is right off my Christmas card list for casting such an insult ;D As I am but a humble signalman, most of the technical stuff I leave to my colleague Harsig, who, despite also being officially just a humble signalman, knows quite a bit more than I do. I can change the spark plugs, air filter and do an oil change, whereas my colleague can do the full engine strip down - if you see what I mean ;D Having said all that, from what I can see above, most of it has been covered. Basically, as has already been mostly said, draw-ups and the like are placed to protect what lies beyond - be that a limited overlap, junction or end of the line. C5, strangely enough platform 2 used to have a draw-up heading west (OP500) only used following a main line shunt from OP8). They got rid of it under the re-signalling. The same re-signalling which tied everything else down but let this particular move lose ;D |
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Post by Deleted on May 10, 2006 9:12:07 GMT
spot on colin
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Post by Deleted on May 10, 2006 9:19:32 GMT
starters can have timing sections A840 at cannon street (w/b starter) has 2 timing sections one 4 1/2 sec and one 15 sec for example depends on the site really
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Post by Deleted on May 10, 2006 9:20:44 GMT
I think the expertise of a T.O. is needed! Where's BAET and citysig! citysig isn't a T.O. but he might know a tad more Yes thank you C5. Mr OneKea is right off my Christmas card list for casting such an insult ;D Hey! I thought it was a compliment.... As I am but a humble signalman, most of the technical stuff I leave to my colleague Harsig, who, despite also being officially just a humble signalman, knows quite a bit more than I do. I can change the spark plugs, air filter and do an oil change, whereas my colleague can do the full engine strip down - if you see what I mean ;D Having said all that, from what I can see above, most of it has been covered. Basically, as has already been mostly said, draw-ups and the like are placed to protect what lies beyond - be that a limited overlap, junction or end of the line. C5, strangely enough platform 2 used to have a draw-up heading west (OP500) only used following a main line shunt from OP8). They got rid of it under the re-signalling. The same re-signalling which tied everything else down but let this particular move lose ;D Why would they get rid of it? |
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Post by marty on May 10, 2006 9:29:29 GMT
Anne Elk Brackets Miss Brackets: Spot on Chris Colin |
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Post by citysig on May 11, 2006 10:44:14 GMT
Why would they get rid of it? I thought the same. A program of installing various speed control signals, increasing overlaps and generally tying everything down and they get rid of one of the original pieces of protection in that platform. However, as part of the same program it became impossible to have trains moving in such a way that safety would be infringed. They got rid of the signal and associated government of the trains but replaced it with different locking. |
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