Deleted
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Post by Deleted on Sept 20, 2005 22:24:42 GMT
I was just wondering.
The middle i do believe is the neg and the one on the outside pos.
Do have to be on both rails to kill you or just one?
And do the rails have enough power as in signaling currents to kill you?
It's just a while ago one of my mates who is stupid and ridiculous said he was walking on the tracks near Upminster B stood on the running rail not the power rail and got a shock?
A few of my mates have been on LU rails in the past and have come close to being killed either by rails or by train.
I tell them never to go up there as it is suicide!
And if they do and i can't stop them which i can't i tell them to look take their sweet time and not to step on any rail.
I know some regulations for working track side as i do have a PTS for EOR but could it really shock you?
Cheers
James
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Tom
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Post by Tom on Sept 20, 2005 22:32:23 GMT
Either current rail to earth has the potential to kill you. Likewise the running rails can be raised to a lethal voltage at certain times.
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Colin
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Post by Colin on Sept 21, 2005 0:15:48 GMT
Perhaps next time they do it, you would be kind enough to inform the British Transport Police on 0800 405040 (or 999 if emergency). Myself and my colleauges do not appreciate this stupidity, nor do we have any desire to be involved in the hororific scenario of a one under.  To add to the answer for your question, the running rails are 'track circuited', albiet at a low voltage. Basically ALL rails are live.  |
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Post by Deleted on Sept 21, 2005 0:30:21 GMT
Ok fine,
But i don't know if they are doing it!
When they say come across the track i stop them then.
All i see is death on the tracks.
But still i don't think they do it any more really.
I think they have had one too many close shaves if you know what i mean.!
And yeah i bet it does cause you trouble like whole sections of line down for hours on end.
But hey i don't do it and i don't talk to them much anymore.
If i remember about a year ago i came out of UB station and went to the indian for a curry about 20 mins later a one under happened the ambulence went right into the station.
The day after i asked my freindly station supervisor wahat had happened.
Aparently the guys head smashed into the cab don't know if its true though?
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Colin
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Post by Colin on Sept 21, 2005 0:41:05 GMT
eorjames- Please don't take my post too much to heart!  I put up the BTP number so that everyone will know it (it's for the whole country BTW). I just wanted all readers of this forum to appreciate the severity of a few tw*ts actions, and that they can report such activity easily. P.S. you can think tw*ts means twits, though i'm thinking of a different word. |
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Deleted
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Post by Deleted on Sept 21, 2005 18:00:14 GMT
Let me just point out at this stage that tresspassing on the railway is breaking the law, and also can be very very dangerous and in some cases fatal.
I dont particually want to see people messing around on a railway. It is not big nor is it cool.
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Deleted
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Post by Deleted on Sept 21, 2005 19:47:01 GMT
Hey ok guys.
I don't like it i don't see the point of it.
I think their a bunch of wa*kers for doing it.
But i don't have a mobile phone, when they have done it in the past i go to the station and tell the guy there!
Whats so great about a bunch of metal and death anyways.
Cheers
james
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Tom
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Post by Tom on Sept 21, 2005 21:23:19 GMT
To add to the answer for your question, the running rails are 'track circuited', albiet at a low voltage. Basically ALL rails are live. Low? I remember getting 180v off a track circuit once. And of course as it's the current that kills, some of the track circuits with very low voltages are the nastiest around... |
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Post by igelkotten on Sept 23, 2005 10:31:13 GMT
And don't forget, if you are on a third-rail raiwlay wich uses the running rails as earth return, you can have some very, very nasty potentials in the running rails themselves, depending on circumstances.
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Colin
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Post by Colin on Sept 24, 2005 15:10:51 GMT
Low? I remember getting 180v off a track circuit once. And of course as it's the current that kills, some of the track circuits with very low voltages are the nastiest around... I know you can get negative earths, current return, etc. I was merley thinking of LUL tracks under normal circumstances. I thought our track circuits were around 5 volts (?), good job we have places like this with people in the know!!. |
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Post by q8 on Sept 24, 2005 15:16:09 GMT
Regarding current rails and a little off-topic. Why do they still insist on having a centre negative on LUL when the Glasgow subway, Moscow Metro and others run perfectly well with running rail return?
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Post by Deleted on Sept 24, 2005 15:29:06 GMT
Because of the immense cost of reconstructing the track circuits, signalling equipment and track furniture to ensure that the cast iron tunnels do not become a return path for the traction current.
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Tom
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Post by Tom on Sept 24, 2005 19:16:47 GMT
I know you can get negative earths, current return, etc. I was merley thinking of LUL tracks under normal circumstances. I thought our track circuits were around 5 volts (?), good job we have places like this with people in the know!!. Normally they're in the 5-30v range. Fault conditions are something else though, if an open circuit develops the capacitors keep charging and if you get a belt then it hurts. Traction earths both positive and negative can have some interesting effects too... |
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Post by q8 on Sept 24, 2005 23:42:19 GMT
Now to query TOK's answer. I am told that an insulated cable on the runs connected to the running rails as an earth will do just that by making sure the return current goes back to the sub in the same way as the negative rail does.
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Post by Deleted on Sept 25, 2005 5:00:10 GMT
In response to Q8, in the tubes it is not unknown for a short to develop between the positive rail and the cast iron tunnel. This would bring a 3-rail system to a halt, but with the 4-rail system the outer rail becomes 0 volts, the centre one becomes -660 volts, and the trains keep going.
LU needs a 4-rail system because it is the only railway that runs through tiny cast iron tunnels.
There's probably no reason for District and Met to have 4 rails these days, except that it means that tube trains can run over these lines.
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Post by q8 on Sept 25, 2005 5:56:36 GMT
I am at a loss really to see how a short can occur between the positive and the tunnel lining when the bottom of the latter is concreted for about 2ft up the sides. Anyway I have seen that current rails can be encoated in insulating plastic on all except the running surface which would substatially reduce such occurences.
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Deleted
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Post by Deleted on Sept 25, 2005 9:42:01 GMT
I bow to Q8's superior knowledge of how things are arranged these days.
In the early days, the tubes were not concreted and shorts did occur. Indeed, when the Bakerloo first opened the shorts were so frequent that the polarity was reversed: centre was live and outside was return.
Maybe nowadays it's just inertia. And the immense cost of removing the centre rails, bonding the running rails, changing the track circuits so that they are not affected by the return traction current, etc., etc., etc.
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Tom
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Post by Tom on Sept 25, 2005 13:08:19 GMT
Shorts can occur indirectly through the earthing arrangements in use.
Both the positive and negative are referenced to earth (in this case one of the running rails) via bleed resistors for traction earth detection. This same rail is used as an earth reference for track circuits and is connected to the tunnel lining, at least on the Bakerloo and Victoria lines.
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