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#51
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On 07/04/2008 10:32, MIG wrote:
I'm sure I remember Peter Purves going into the Underground with a maintenance team for Blue Peter in the 1970s, and being shown a bank of twelve light bulbs "just in case". yes I remember that too, presumably 4 parallel sets of 3 lamps in series so the -240/+410 gives each lamp about 250V? |
#52
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On Apr 7, 9:43 pm, Andy Burns wrote:
On 07/04/2008 10:32, MIG wrote: I'm sure I remember Peter Purves going into the Underground with a maintenance team for Blue Peter in the 1970s, and being shown a bank of twelve light bulbs "just in case". yes I remember that too, presumably 4 parallel sets of 3 lamps in series so the -240/+410 gives each lamp about 250V? Current Rail Indicator Devices. Fixed CRIDs are now being installed on the headwall of many tube stations (small box with lights indicating 'On', 'Off', 'Failed'). |
#53
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#54
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On Mon, 7 Apr 2008 02:32:13 -0700 (PDT), MIG
wrote: On 7 Apr, 08:34, Stimpy wrote: On Sun, 6 Apr 2008 21:18:22 +0100, Matthew Geier wrote *Some one who regularly works on railway power systems may actually have in their kit a 'test lamp' for 750v supplies. IIRC, it's a bank of lamps "just in case" one or two lamps have blown I'm sure I remember Peter Purves going into the Underground with a maintenance team for Blue Peter in the 1970s, and being shown a bank of twelve light bulbs "just in case". (I also remember his reference to "the hiss of opening doors", despite there being no such thing till the D78 stock [or since?]. In those days the doors all opened silently and popped before closing.) They all hiss when the seals are worn (and the door motors aren't electric). |
#55
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#56
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On Apr 7, 10:15*pm, Charles Ellson wrote:
On Mon, 7 Apr 2008 02:32:13 -0700 (PDT), MIG wrote: On 7 Apr, 08:34, Stimpy wrote: On Sun, 6 Apr 2008 21:18:22 +0100, Matthew Geier wrote *Some one who regularly works on railway power systems may actually have in their kit a 'test lamp' for 750v supplies. IIRC, it's a bank of lamps "just in case" one or two lamps have blown I'm sure I remember Peter Purves going into the Underground with a maintenance team for Blue Peter in the 1970s, and being shown a bank of twelve light bulbs "just in case". (I also remember his reference to "the hiss of opening doors", despite there being no such thing till the D78 stock [or since?]. *In those days the doors all opened silently and popped before closing.) They all hiss when the seals are worn (and the door motors aren't electric). As I remember, in the 1938 to 1972 generations (that I was familiar with), the doors would open silently (apart from the rumble of movement). But they would pop before closing. The pop before closing might be accompanied by a hiss if they were worn, and it was pretty much as useful as bleepers for the punters, if unintentionally. The 1973 and C77 stock made very little noise when opening or closing (although I think there was still a delay before closing when the pop would have been). The D78 stock was very different (as mentioned in another reply), in that it hissed loudly and continuously during both opening and closing. The modern stock makes very little air-related noise at all. Anyway, whoever did the write-up for Blue Peter at the time obviously never travelled on the Underground and was trying to be poetic. |
#57
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In article M8OdnaePt_78GmfanZ2dnUVZ8sTinZ2d@plusnet, Andy Burns
scribeth thus On 07/04/2008 10:32, MIG wrote: I'm sure I remember Peter Purves going into the Underground with a maintenance team for Blue Peter in the 1970s, and being shown a bank of twelve light bulbs "just in case". yes I remember that too, presumably 4 parallel sets of 3 lamps in series so the -240/+410 gives each lamp about 250V? I thought an 'eff off size shorting bar was the best insurance;!... -- Tony Sayer |
#58
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On Tue, 8 Apr 2008 09:52:47 +0100, tony sayer
wrote: In article M8OdnaePt_78GmfanZ2dnUVZ8sTinZ2d@plusnet, Andy Burns scribeth thus On 07/04/2008 10:32, MIG wrote: I'm sure I remember Peter Purves going into the Underground with a maintenance team for Blue Peter in the 1970s, and being shown a bank of twelve light bulbs "just in case". yes I remember that too, presumably 4 parallel sets of 3 lamps in series so the -240/+410 gives each lamp about 250V? I thought an 'eff off size shorting bar was the best insurance;!... It doesn't work if one conductor rail is isolated from the source. Come to think of it, neither will the lamp which really needs to have a third connection to 0v to do the job properly. |
#59
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In article , Charles Ellson
scribeth thus On Tue, 8 Apr 2008 09:52:47 +0100, tony sayer wrote: In article M8OdnaePt_78GmfanZ2dnUVZ8sTinZ2d@plusnet, Andy Burns scribeth thus On 07/04/2008 10:32, MIG wrote: I'm sure I remember Peter Purves going into the Underground with a maintenance team for Blue Peter in the 1970s, and being shown a bank of twelve light bulbs "just in case". yes I remember that too, presumably 4 parallel sets of 3 lamps in series so the -240/+410 gives each lamp about 250V? I thought an 'eff off size shorting bar was the best insurance;!... It doesn't work if one conductor rail is isolated from the source. Come to think of it, neither will the lamp which really needs to have a third connection to 0v to do the job properly. Well one would short pos and neg to the running rail//s.. -- Tony Sayer |
#60
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On Tue, 8 Apr 2008 17:37:04 +0100, tony sayer
wrote: In article , Charles Ellson scribeth thus On Tue, 8 Apr 2008 09:52:47 +0100, tony sayer wrote: In article M8OdnaePt_78GmfanZ2dnUVZ8sTinZ2d@plusnet, Andy Burns scribeth thus On 07/04/2008 10:32, MIG wrote: I'm sure I remember Peter Purves going into the Underground with a maintenance team for Blue Peter in the 1970s, and being shown a bank of twelve light bulbs "just in case". yes I remember that too, presumably 4 parallel sets of 3 lamps in series so the -240/+410 gives each lamp about 250V? I thought an 'eff off size shorting bar was the best insurance;!... It doesn't work if one conductor rail is isolated from the source. Come to think of it, neither will the lamp which really needs to have a third connection to 0v to do the job properly. Well one would short pos and neg to the running rail//s.. That would be nearly the same as earthing of all phases on overhead lines (seven clamps/clips and a spider of cable) but not quite. The "box of eggs" is OK as long as someone looking at it realises that if someone working further down the track has left off (or chopped) the feed from one pole then the other could still be live if the supply was switched on. It seems more of a warning that trains could approach than of electrical safety; the FO short-circuit bar will stop the trains (other than diesel/battery/etc.) but the usual rule about treating anything as live unless it is obviously earthed seems to be the main defence. |
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