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Post by ducatisti on Jun 23, 2008 12:23:11 GMT
Quick q (apologies to those who have already heard it)
The signal at the city end of West Finchley station has those little side aspects on it that allow it to be seen when the driver is close to it (Pigs Ears?). The signal is about a car-length from the end of the platform.
Two theories that we have come up with are
1) a relic of the 9-car trials, or
2) freight operations from High Barnet.
Can anybody shed any light?
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Post by Tubeboy on Jun 23, 2008 12:32:33 GMT
I think? they are called Arbour lights, the starter on the Northbound has them as well [A204].
I think the Southbound starter is NQX300, the next is NQ3, which is the last before the Mill Hill branch converges.
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Post by ducatisti on Jun 23, 2008 12:48:50 GMT
Sorry old chap, I don't understand your banter ;D
I thought arbour lights were the ones that said "you are turning left here" etc.
What I mean are the little holes (and presumably prisms and lenses and wotnot) that come off the aspects so that if you are drawn right up to the signal and so couldn't see the main aspects, you still can still see if it's red or green.
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mrfs42
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Post by mrfs42 on Jun 23, 2008 12:53:27 GMT
Not arbour lights - these definately (as in wot ducatisti is asking after) are pigs ears. www.trainweb.org/tubeprune/signalling3.htm Fig 1 JP14 which has both; if I remember the question from the other night correctly. Still thinking as to why the starter should be deliberately off the end of the platform by a car length. I've had a quick look through my perils for the early 70s and there are notes there for 'removal of 9 car starting signal' - but need to dig further into the pile - I've got the introduction of 9 car trains notice somewhere - but I really think that the 9 cars are a big of a red herring: I'm tending more towards a compromise with getting goods trains off Barnet well down the platform so trains could approach from Barnet or reverse at Woodside Park. You've presumably seen Harsig's diagrams which can be found here |
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Post by District Dave on Jun 23, 2008 12:54:48 GMT
You're correct in your description of them as 'pigs ears' - so named because of their appearance.
I don't know the specific location to which you refer, but many signals on the District have them. The idea is that they give you a view of the aspect when pulled right up to them - and for some station starter signals when you have to berth similarly close!
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Post by railtechnician on Jun 23, 2008 13:03:34 GMT
You're correct in your description of them as 'pigs ears' - so named because of their appearance. I don't know the specific location to which you refer, but many signals on the District have them. The idea is that they give you a view of the aspect when pulled right up to them - and for some station starter signals when you have to berth similarly close! Pigs ears are fitted to short range and long range colour light signal heads but not to tube type signal heads. |
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Post by Deleted on Jun 23, 2008 14:25:30 GMT
i asked this question 3 weeks ago to my bosses and the answer i got back was this:
when steam trains were around the front of the train would actually just pass the signal head and the driver if draw up to a red aspect would be roughly inline with it so they put these pig ears in to show what the main lense was showing
these are a pain to change in traffic as blowing a fuse (which could cause the signal to fail) is a very high risk so generally these are changed in engineering hours
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Post by ducatisti on Jun 23, 2008 16:54:13 GMT
Sounds likely to be the answer then.
I suppose that it was beyond the platform to stop passengers being inconvenienced by it
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Post by Deleted on Jun 23, 2008 17:35:54 GMT
these are a pain to change in traffic as blowing a fuse (which could cause the signal to fail) is a very high risk so generally these are changed in engineering hours I always thought the pigs ears were illuminated from the main bulb. |
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metman
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Post by metman on Jun 23, 2008 17:48:55 GMT
So did I! On the city sections of the met, there are also the same signals, except there are no hoods on the bulbs! I think most LU signals have pigs ears!
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Post by Deleted on Jun 23, 2008 19:09:39 GMT
these are a pain to change in traffic as blowing a fuse (which could cause the signal to fail) is a very high risk so generally these are changed in engineering hours I always thought the pigs ears were illuminated from the main bulb. So did I, until one day I came across a signal where the main green aspect had failed but the pigs ear was still lit. |
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Post by happybunny on Jun 23, 2008 19:35:16 GMT
Yeah when I was on the platform the starter had failed on P8 however the pigs ear remained working, it was the middle of winter, and the supervisor (a certain evil supervisor) insisted on me standing at the headwall as a handsignal man. I was there about ten minutes, then phoned the signal man and asked him to use platform 9 instead of 8 (it was off peak) which he was happy to do  I then disappeared |
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mrfs42
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Post by mrfs42 on Jun 23, 2008 19:54:32 GMT
I might be getting my signal designs confused here, but at some point there were 2 separate bulbs inside a signal head, the main aspect being frosted and the auxiliary being clear - I think the optical system for pigs ears was arranged to use the main filament only.
I know that the modern signals have single twin filament bulbs rather than twin single filament bulbs and these more modern signals have separate pigs ear blubs. I suppose that there is still a pay-off as the signal works at short range and isn't completely dead.
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Post by Deleted on Jun 23, 2008 23:14:59 GMT
the pigs ear bulb is lit from the transformer which also feeds the main bulb its parallerd off at the terminals
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Post by Deleted on Jun 23, 2008 23:21:38 GMT
in a short range the pigs ear is just lit by the actual main bulb itself
in a long range there is 2 seperate bulbs the main one for the main lense and a smaller bulb (looks like the bulb for a car indicator) its the pigs ear which is a pain to relamp in traffic as the terminals are bare and you have to gently remove it and carefully as the signal head is earthed so if the terminals touched the signal head it would blow the fuse by creating a dead short hope that explains it better
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Post by railtechnician on Jun 24, 2008 11:38:32 GMT
in a short range the pigs ear is just lit by the actual main bulb itself in a long range there is 2 seperate bulbs the main one for the main lense and a smaller bulb (looks like the bulb for a car indicator) its the pigs ear which is a pain to relamp in traffic as the terminals are bare and you have to gently remove it and carefully as the signal head is earthed so if the terminals touched the signal head it would blow the fuse by creating a dead short hope that explains it better Tell 'em about the little sliders with the bulbholders on the end that have a mind of their own as soon as the fixing nut is loosened and the forest of terminals on the LRCL multitap transformers! I'm sure the average person assumes it's all as simple as changing the light bulb in the average lounge bulbholder but easier because there is a fixed ladder! Don't mention the painted over rusted on cast iron signal head doors! I'm sure every lineman uses his safety belt these days :-) |
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Post by Tom on Jun 24, 2008 20:38:13 GMT
I might be getting my signal designs confused here, but at some point there were 2 separate bulbs inside a signal head, the main aspect being frosted and the auxiliary being clear - I think the optical system for pigs ears was arranged to use the main filament only. That's the tube tunnel head. The newer Howells Long Range Heads are to BR spec, and don't use pig's ears. These have hot strips on the lenses instead, which have the same effect. |
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Post by mrfs42 on Jun 24, 2008 23:33:37 GMT
Very much so - hot strips (even with the unusual Dorman LED type) make sighting so much easier - siting could be a completely different ballgame.  Sixty degrees, less IBJs...... ;D |
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Post by ducatisti on Jun 30, 2008 21:07:28 GMT
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Post by Deleted on Jun 30, 2008 23:02:55 GMT
Being the kind of bod that works with lighting equipment, I'm curious to know what is in a signal head. I've had a traffic signal in bits* on the bench and was particularly surprised by the size of it and that each aspect had a 12V transformer behind it. Just from looking at a railway signal head, it's clearly not the same beast... any info would be interesting. *N.B. it was a scrap one donated by a local signal manufacturer and not one I "found" in the high street! |
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Post by railtechnician on Jul 1, 2008 6:13:25 GMT
Being the kind of bod that works with lighting equipment, I'm curious to know what is in a signal head. I've had a traffic signal in bits* on the bench and was particularly surprised by the size of it and that each aspect had a 12V transformer behind it. Just from looking at a railway signal head, it's clearly not the same beast... any info would be interesting. *N.B. it was a scrap one donated by a local signal manufacturer and not one I "found" in the high street! Well the Long Range Colour Lights have lamp transformers which have tappings at 12v, 11v, 10v as I recall, the input being from a nominal 100v signal supply and on some lines lke the Met there is even battery back up for the red aspect IIRC. Working inside one can be an electrifying experience due to all the 1BA transformer terminals in a rather cramped space for each aspect. I can say that they weigh a ton literally and in the old days we would haul them up and down on a single wheel pulley precariously fitted to the end of a length of 2" GI air main with half a dozen men on the rope and a couple to stabilise the pole which was always liable to bend and sometimes did. The last time I can recall this technique being used was on WM 20/21 at Hanger Lane Junction several years ago now when renewing the signal post which was rusting away from the ground up. The short range heads have just bulbholders and porcelain terminal blocks as the aspects are fed 100v. But all signal heads are heavy, even those little 2 aspect tunnel ones. I recall having to change one at Stockwell about 30 years ago and it was about 100 yards down the tunnel. I was young and green then and the mechanical aids of today did not exist then except for the track trolley and we didn't have one handy. I learnt very quickly that shouldering such a signal head from street to tunnel location was a bad idea without padding! |
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I then disappeared 
