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I will stand corrected on that point Keith. The actual distance between lens centres on a traditional head is about 10". The spacing of double yellow aspects should be 5x lens aperture radius. That gives a space of about 12" between the inner edges of the lens bezels. My guess based on photos is that VMS doesn't match this. Can anyone supply the actual measurements please?

is about 10". = 254 mm, with a lens diameter of 214. The VMS centre to centrre is a bit more at 269 mm but the apertures look to be rather larger than the traditional lenses. Drawings in here: Colour Light Signal.pdf

 

I have the Dorman sales literature but the file is to big to upload and none of the drawings in it are dimensioned anyway.

 

Somewhere I have drawings of traditional heads but can't find them today.

Regards

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Attached is the maintenance specifications for technicians working on the Dorman ILS drop down signals.

 

attachicon.gifimage.jpeg

 

To be very blunt I think that is absolutely atrocious and verging on downright dangerous.  'Liaise with the signaller ...'  is a total nonsense and runs contrary to any safety principle when writing any Instruction I have ever come across (or have written as a Rule or Instruction) for working on signalling equipment when the safety of train operations will be affected.  

 

A proper Instruction would say 'Before starting work you must obtain permission from the Signalman (or '...ler' if you so prefer) if it will be necessary to obscure or dismantle/lower the signal'.    What could be clearer - even the sooper dooper 'Plain English' PC mob couldn't moan about something that explicit and in this case the Instruction needs to be explicit - not some nonsense about 'liaising' when what is actually needed is permission to interfere with the safe working of the railway.  While it might well be in the Rule Book it also needs to be restated in an Instruction such as this - and this Instruction should also cross-refer to the relevant Rule.

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To be very blunt I think that is absolutely atrocious and verging on downright dangerous.  'Liaise with the signaller ...'  is a total nonsense and runs contrary to any safety principle when writing any Instruction I have ever come across (or have written as a Rule or Instruction) for working on signalling equipment when the safety of train operations will be affected.  

I like the paragraph which states-

 

Check any record cards for any entries since you last visited. Where alterations are being carried out, your SM(S) should have briefed you on the work and the effect on planned maintenance.

 

That is so 'woolly' as to be next to useless, what happened to the rules being straight forward "you must" or "you must not".

 

I suppose that when they carry out work on these things and there is a crash before or after they can use these 'guidelines' (they certainly are not instructions) as a get out cause to avoid prosecution!

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Like them or loath them the SMS (signal maintence specifications) have been around many years and I will see if I have a copy of my first set issued in the late 80's to compare to now.

There are another 5 pages in addition to the page I posted for maintence of just that one ILS style of signal and 6 hyperlinked specific tests dependant on type of service.

Below is the latest excerpt from the general instructions to staff in relation to work on in service equpment (apologies for poor quality of image).

post-7305-0-89813100-1469544928_thumb.jpeg

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Slightly OT but relating to movable signals, I remember (back in the early 80's) an apocryphal story of a signal (I think it was on the LT&S) that got knocked over in the dark during a track renewal and wasn't discovered for some hours after trains had started running again ...................

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is about 10". = 254 mm, with a lens diameter of 214. The VMS centre to centrre is a bit more at 269 mm but the apertures look to be rather larger than the traditional lenses. Drawings in here: attachicon.gifColour Light Signal.pdf

 

I have the Dorman sales literature but the file is to big to upload and none of the drawings in it are dimensioned anyway.

 

Somewhere I have drawings of traditional heads but can't find them today.

Regards

Thanks for that one Keith.

The VMS 4 aspect head using a conventional pattern of 4 separate units would look to be compliant with the Fig G7 on page 85 of Rail Industry Standard RIS-0737-CCS Signal Sighting Assessment Requirements which was published recently. http://www.rssb.co.uk/rgs/standards/RIS-0737-CCS%20Iss%201.pdf. This shows a radius of 105mm for the aspects and a spacing between yellows of 510mm +20/-10.

The document also shows a graph of sensitivity to lights of equal strength, where the maximum occurs in the green/yellow part of the spectrum.

(Incidentally that document has a lot of drawings of different signal configurations for both semaphore and colour ligh signals and route indicators. It would be very useful for modern image modellers along with http://www.rssb.co.uk/rgs/standards/GKRT0058%20Iss%201.pdf)

 

An interesting part of the VMS leaflet comes at the top of page 2 and regards the candlepower of the different coloured units. The Red and Green aspects have a minimum intensity of 850cd, whilst the yellow is 2600cd. This is exactly the problem encountered when we tried to introduce some LED signals in use overseas nearly 20 years ago. They were rejected on the basis that the yellow aspect was too bright.

 

The problem with the current Railway Groups Standards do not specify luminous intensity for products, the explanation being

"It is not appropriate to specify display element luminous intensity, size and contrast parameters because they would need to take account of all potential performance requirements and applications"

The guidance document on approvals states

"Excessive luminous intensity can cause discomfort, glare and make displays and indications difficult to read due to the ‘bleeding’ of the lights into each other. This is a particular problem if the appearance of the display is distinguished by any of the following:

a) The number of display elements (for example, a double yellow display).

.........."

Elsewhere it states that

"Simultaneously lit display elements of the same colour shall have a similar intensity"

 

This means that a product can be approved as long as the two units in a double yellow have the same intensity but they don't have to be the same intensity as the Red or green.

 

The RIS document warns against using signals of different intensity on a line as there are risks in over-reading and differences in distance perception. The RGS seems to totally ignore this in the sections I have read so far. The whole thing is a total minefield which i am afraid will only be resolved as have so many things in the past by an accident happening and some proper research into these new signals.

 

My head hurts and I haven't even considered the "dandelion" double yellow yet, but from pictures it doesn't look to be compliant with the RIS. 

 

 

 

 

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To be very blunt I think that is absolutely atrocious and verging on downright dangerous.  'Liaise with the signaller ...'  is a total nonsense and runs contrary to any safety principle when writing any Instruction I have ever come across (or have written as a Rule or Instruction) for working on signalling equipment when the safety of train operations will be affected.  

 

A proper Instruction would say 'Before starting work you must obtain permission from the Signalman (or '...ler' if you so prefer) if it will be necessary to obscure or dismantle/lower the signal'.    What could be clearer - even the sooper dooper 'Plain English' PC mob couldn't moan about something that explicit and in this case the Instruction needs to be explicit - not some nonsense about 'liaising' when what is actually needed is permission to interfere with the safe working of the railway.  While it might well be in the Rule Book it also needs to be restated in an Instruction such as this - and this Instruction should also cross-refer to the relevant Rule.

I suspect you will find plenty of other flaws in the SMS / SMTH / group standards if you went through them. In many ways it's a shame people such as yourself aren't around to get them corrected.

 

However it is worth remembering though that the whole SMS / SMTH is a direct result of the Clapham Junction crash in 87 and to a certain extent has allways suffered from being a retrospective work for most signalling kit. Though when it comes to newly introduced like fold down signals and suchlike these things should be correct from the beginning (mind you that hasn't stopped NR from installing them on a squadron basis while the SMS / SMTH is still being written).

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Slightly OT but relating to movable signals, I remember (back in the early 80's) an apocryphal story of a signal (I think it was on the LT&S) that got knocked over in the dark during a track renewal and wasn't discovered for some hours after trains had started running again ...................

There have been a few stories about signals 'moving', the best one was from the former Southern Region about one which slid down an embankment into somebodies back garden, unluckily (or luckily depending on your viewpoint) there was enough slack in the wiring for it to remain connected to the signalling systems and trains were whizzing past it without a care in the world and it was only when the house owner contacted BR and asked why he had a signal in his back garden, A few questions later about any plates with letters and numbers on it and it resulted in a line blockage and some very awkward questions about route knowledge for some drivers!

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I suspect you will find plenty of other flaws in the SMS / SMTH / group standards if you went through them. In many ways it's a shame people such as yourself aren't around to get them corrected.

 

However it is worth remembering though that the whole SMS / SMTH is a direct result of the Clapham Junction crash in 87 and to a certain extent has allways suffered from being a retrospective work for most signalling kit. Though when it comes to newly introduced like fold down signals and suchlike these things should be correct from the beginning (mind you that hasn't stopped NR from installing them on a squadron basis while the SMS / SMTH is still being written).

 

There probably are Phil if some of the things I have come across on NR in the last few years are any indication.  However a lot of the attitude goes back to the Rule Book and it, in my opinion, is an absolutely appalling document which repeatedly indicates a  total disconnect between those who write it and those who have to implement it together with a lack of even commonsense checking at source let alone full review before amendments are issued.  The Signalling Regulations seem to have been issued with a  greater emphasis on saving paper than on their practical application and the ease of learning them with many Regulations simply referring back to the SGI section rather than containing all relevant parts.

 

The most interesting - in a  not very nice way - disappearing signal I ever heard about was one at Reading which was, literally, blown up by some Irish fellahs in the days of teh last lot of 'troubles' in NI.  One helluva bang as it happebned and we heard it from two miles a way on the other side of town.

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