how to interpret this diagram?

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jon price
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how to interpret this diagram?

Postby jon price » Mon Jan 28, 2019 10:07 am

The attached is a portion of a signalling diagram from Anderson and Fox, Chester to Holyhead Railway. I'm guessing the standard format is being used so there is no key to the diagrams in the book, but this isn't an area I know about. The home signal pulled by lever no3 on the down main I understand. No 2 lever I assume pulls the distant signal, but the home signal on the same post is fixed in the on position. I can't understand what is going on with No13. The position of the number, from looking at the other diagrams in the book, indicates that the lever pulls both the home and the distant signal, but I an not clear why the distant has a shadow in the off position. Any suggestions?
P1280172.JPG

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Tim V
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Re: how to interpret this diagram?

Postby Tim V » Mon Jan 28, 2019 10:29 am

The signal above Number 2 is the advanced starter for the box in rear.
13 is above the distant for the box in advance and slots the distant signal for that box.

Slotting is a means that you can't have a distant off, while the signal above is on.
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Re: how to interpret this diagram?

Postby John Palmer » Mon Jan 28, 2019 10:44 am

Difficult to be sure without sight of more of the diagram, but it seems that the un-numbered stop signal above 2 may be a starting signal for the box in rear. The 'shadowed' off position of the other distant indicates that it is slotted with the box in advance, and if already pulled by that box will clear when the starting signal above it is pulled. Both of these suggestions are consistent with the notion that these are two boxes in close proximity.

<Edited to add: two minds with but a single thought.>

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jon price
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Re: how to interpret this diagram?

Postby jon price » Mon Jan 28, 2019 11:01 am

this is Box 2 diagram (which is to the right of the image) Box 1 is to the left. So does this mean there will be signal control cable from signal 13 post in both directions (home to Box 2, distant to Box 1) and from signal post 2 in both directions (distant to box 2, home to box 1)?

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Re: how to interpret this diagram?

Postby John Palmer » Mon Jan 28, 2019 2:35 pm

Yes, and the slotting mechanism will ensure that if the stop signal above the distant is restored to a 'stop' aspect having previously caused the distant below to display a 'clear' aspect, the distant too will be restored to 'caution' without further intervention on the part of the signalman to whose stop signals it applies.

The mechanics of the slotting arrangement are extensively illustrated in an LMS Society monograph, accessible here: http://www.lmssociety.org.uk/monologues/M09.pdf

In the case of the down direction, the truncated view of the diagram suggests that there may be an additional distant signal located 1219 yards in rear of No.2's Home signal (3). This may be located beneath another of No.1's signals and thus will need to be similarly slotted.

If 13 is No.2's home signal then it is also taking the role of starting signal controlling admission to the No.2-No.1 block section in the up direction.

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Re: how to interpret this diagram?

Postby jon price » Mon Jan 28, 2019 3:22 pm

Excellent info, thanks very much for the link to the LMS soc monograph. Now I know what I am looking at I can browse through photos of signal posts until I have worked out what should be happening on my 1906 LNWR posts. I will be depicting the 3 and 13 posts as part of a short section of the Chester to Holyhead on the embankment behind Connah's Quay, no signal boxes, and only about 100 yards of track, but the signal posts are smack in the middle so need to be properly dealt with.

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grovenor-2685
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Re: how to interpret this diagram?

Postby grovenor-2685 » Mon Jan 28, 2019 3:48 pm

Note that all Distant signals fitted below stop signals are slotted as standard and this is not specifically shown on the diagrams, as for signal 2.
Where the slotting is specifically shown by the shadow as on signal 13 it means that the distant concerned relates to two boxes and thus needs two distant levers to be pulled as well as the stop signal.
Effectively a triple slot and there will be two wires and balance levers for the distant as well as the one for the stop signal.
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Re: how to interpret this diagram?

Postby jon price » Mon Jan 28, 2019 4:57 pm

So I just reached an understanding of how the standard system worked and can now interpret the drawing of Webb's system in LNWR Portrayed, and LNWR Signalling but now Keith has kindly upped the ante by explaining what the real meaning of No13 is.

Webb's system has two weight arms in a bracket, operating through a third arm. Would it be possible to stack two of these mechanisms to cope with the particular requirements that Keith has explained? Or would there simply be three weight arms operating through a fourth arm? This would suggest an additional different sized bracket casting which might be at odds with Webb's mania for standardisation.

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Re: how to interpret this diagram?

Postby grovenor-2685 » Mon Jan 28, 2019 11:07 pm

Either of those options and probably more, afraid I don't know details of specific LNWR examples, or any others really.
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Re: how to interpret this diagram?

Postby Noel » Tue Jan 29, 2019 3:43 pm

Accepting John Palmer's identification of the Down signals, which I do, then 13 cannot really be anything but No.1 box's Up starter. It can't refer to the distant, as this leaves the home above controlled by another box, which can only be No.2 from the geography of the diagram, which is not possible if the distant below it belongs to No.1 box. Equally, it is not slotted by No.2 box [theoretically possible], as no slot is shown. The distant below 13, therefore, belongs to No.2 box, again from the geography.

Why then is the slot for the distant below 13 specifically identified, when that for 2 is not? As we do not know the conventions used, this could be a) because the distant is operated by two boxes [which cannot include No.1 box] or b) because the distant is indirectly controlled by No.1 box via 13. The number of signal wires present will differ depending on which is right, as will the presence of one or two slots. If Jon can show us the home signal above 2 on the No.1 box diagram, [which will also show 2] then we can check the convention and hopefully clarify how many wires and slots.
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Re: how to interpret this diagram?

Postby grovenor-2685 » Tue Jan 29, 2019 3:46 pm

Why then is the slot for the distant below 13 specifically identified, when that for 2 is not? As we do not know the conventions used, this could be a) because the distant is operated by two boxes [which cannot include No.1 box]

Yes, which is what I tried to say above! Sorry if it was not clear. I have found a bit more info in one of the IRSE Green booklets which I will scan shortly.
Rgds.

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Noel
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Re: how to interpret this diagram?

Postby Noel » Tue Jan 29, 2019 4:02 pm

grovenor-2685 wrote:Why then is the slot for the distant below 13 specifically identified, when that for 2 is not? As we do not know the conventions used, this could be a) because the distant is operated by two boxes [which cannot include No.1 box]

Yes, which is what I tried to say above!


I can't speak for anyone else, Keith, but I had understood you. I just felt that there was at least one other possibility which should be considered...
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jon price
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Re: how to interpret this diagram?

Postby jon price » Tue Jan 29, 2019 4:52 pm

no 13 belongs to No2 box. The distant appears to be No1 box lever 36. In most cases the number is specifically next to the signal, but in a few cases the number appears between the signals on the post. In the case of No2 box 14 for example this can only mean that both signals were pulled by lever No14. I thought this should therefore also apply to the two signals at 13. I didn't post the full diagrams before as I am only interested in the two posts at 3 and 13, but here they are now.
P1290174.JPG

P1290175.JPG

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Re: how to interpret this diagram?

Postby John Palmer » Tue Jan 29, 2019 6:56 pm

I found Keith's explanation very lucid, and the conclusion I drew from it is that the distant beneath Connah's Quay No.2 up starting signal was effectively triple slotted by CQ No.2 and CQ No.1 and Shotton, which is the next block post beyond CQ No.1, and that it was because this distant related both to CQ No.1's AND Shotton's signals that its 'shadow' aspect was represented, in contrast to the other slotting arrangements. That makes sense because it's a short section between CQ No.1 and Shotton. I had not appreciated the reason for showing the 'shadow' aspect and I'm grateful to Keith for enlarging my knowledge in this respect.

However, I'm puzzled by the full diagrams, between which there seem to be some inconsistencies. CQ No.1 is shown as having two up line distants: 35 and 36. I take it 35 is the distant beneath CQ No.2's starting signal (13) as well as being the distant for Shotton. CQ No.1's lever 36 apparently works a further distant located beneath what must presumably be CQ No.2's up home signal, yet there is no representation of it on the CQ No.2 diagram where the home appears as a co-acting arm (14 on the CQ No.2 diagram). Additionally, this seems to be inconsistent with the convention adopted on the CQ No.1 diagram of showing all distant signals mounted beneath that box's stop signals.

I note that where there are multiple distant signals to be pulled for the passage of a train they are each controlled by separate levers. Am I correct in thinking that the reasons for this are keeping the pull required within the signalman's physical capability and providing for independent adjustment of the wire tension? Are there any other reasons for such independent control?

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Re: how to interpret this diagram?

Postby grovenor-2685 » Tue Jan 29, 2019 9:50 pm

John Palmer wrote:I found Keith's explanation very lucid, and the conclusion I drew from it is that the distant beneath Connah's Quay No.2 up starting signal was effectively triple slotted by CQ No.2 and CQ No.1 and Shotton, which is the next block post beyond CQ No.1, and that it was because this distant related both to CQ No.1's AND Shotton's signals that its 'shadow' aspect was represented, in contrast to the other slotting arrangements. That makes sense because it's a short section between CQ No.1 and Shotton. I had not appreciated the reason for showing the 'shadow' aspect and I'm grateful to Keith for enlarging my knowledge in this respect.

The starter no 13 has the slotted distant below it, and now we see more of the arrangement my conclusion is that the signalling has been modified at some stage and the two distants shown as worked by CQ1 nos 35 and 36 have been combined into one by the slot so that both 35 and 36 have to be pulled (as well as CQ2 no 13) to get the distant off. Probably done this way to avoid a locking change in CQ1, although no obvious reason why 36 could not just have been made spare. if we had the Shotton diagram as well then it might be clearer.

However, I'm puzzled by the full diagrams, between which there seem to be some inconsistencies. CQ No.1 is shown as having two up line distants: 35 and 36. I take it 35 is the distant beneath CQ No.2's starting signal (13) as well as being the distant for Shotton.

35 cannot be the distant for shotton as it would then need a slot. shown shadowed, from a Shotton lever, essential so it can be interlocked with the Shotton stop signals. I think its just the requirement to include a distant on every stop signal of the box in rear that is within the braking distance of the home concerned. Note that on the down CQ2 no 2 is the distant arm on CQ1 starter no 3, this was not clear on the original partial diagram.

CQ No.1's lever 36 apparently works a further distant located beneath what must presumably be CQ No.2's up home signal, yet there is no representation of it on the CQ No.2 diagram where the home appears as a co-acting arm (14 on the CQ No.2 diagram). Additionally, this seems to be inconsistent with the convention adopted on the CQ No.1 diagram of showing all distant signals mounted beneath that box's stop signals.

See above, I think this has been modded at some time, the arm may well have been under 14 but has been replaced by the slot on the arm under 13.

I note that where there are multiple distant signals to be pulled for the passage of a train they are each controlled by separate levers. Am I correct in thinking that the reasons for this are keeping the pull required within the signalman's physical capability and providing for independent adjustment of the wire tension? Are there any other reasons for such independent control?

I would think that is correct.
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Re: how to interpret this diagram?

Postby grovenor-2685 » Tue Jan 29, 2019 10:04 pm

Herewith the promised scan. The relevant text is on the left hand page. Taken from IRSE green booklet No 10, mechanical signalling Equipment.
For LQ signals the arm drive has to be reversed to use push rods, not pull wires.
Slots.jpg

Slots.pdf
(593.63 KiB) Downloaded 25 times

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Re: how to interpret this diagram?

Postby jon price » Tue Jan 29, 2019 10:29 pm

Thanks for the multiple slot depiction Keith. I can now consider how to depict this.

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Re: how to interpret this diagram?

Postby John Palmer » Wed Jan 30, 2019 1:17 am

If CQ No.1's distant 35 is not slotted with a Shotton lever, then why does it appear shadowed on the CQ No.2 diagram? In this case it is a distant relating to the signals of only one box (CQ No.1, not CQ No.1 plus Shotton), and in that respect follows the standard arrangement of a distant below a stop signal, for which, according to the convention, the slotting shadow is not drawn even though the slot is present.

Or would it be more accurate to say that the convention is to draw a slotting shadow for any distant that is controlled by at least two levers in addition to the slot for the stop signal above, irrespective of whether those distant levers are in one box or in different boxes?

It would certainly be helpful to see the Shotton diagram too.

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Re: how to interpret this diagram?

Postby jon price » Wed Jan 30, 2019 11:16 am

Ah Shotton. In fact there is no signal box there (no turnouts), although there appear to be signals (although none of the photos match the diagrams), so these signals would appear to be pulled by 5, 11, 54 and 60 at Queensferry box, and 1, 33 and 29 at Connah's Quay No1. The most obvious fly in the ointment is that on the Queensferry diagram the signals for the down slow and fast are shown as home, but their likely counterparts on Connah's Quay No2 are Distant
P1300176.JPG

P1300178.JPG

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Re: how to interpret this diagram?

Postby grovenor-2685 » Wed Jan 30, 2019 11:58 am

Or would it be more accurate to say that the convention is to draw a slotting shadow for any distant that is controlled by at least two levers in addition to the slot for the stop signal above, irrespective of whether those distant levers are in one box or in different boxes?

Correct.
The most obvious fly in the ointment is that on the Queensferry diagram the signals for the down slow and fast are shown as home, but their likely counterparts on Connah's Quay No2 are Distant

I see no issues here, CQ1 no 1 is the down fast distant, the down slow distant is fixed so no lever no.
Queensferry nos 5 and 11 are the down starters and are not on the same post as the CQ1 distants.

On the up where the slotting question arose, Queensferry up distants 60 and 54 are below the CQ1 starters 33 and 29 so no link back to CQ2.
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Re: how to interpret this diagram?

Postby John Palmer » Wed Jan 30, 2019 1:27 pm

grovenor-2685 wrote:
Or would it be more accurate to say that the convention is to draw a slotting shadow for any distant that is controlled by at least two levers in addition to the slot for the stop signal above, irrespective of whether those distant levers are in one box or in different boxes?

Correct.

Thanks, Keith, that makes better sense to me.

Shotton's lack of a box is a bit of a puzzle. Here is an extract from the Railway Magazine's 'Gradients of the British Main-line Railways' 1947 edition, suggesting that there was a block post at Shotton:
Part Chester Holyhead GP.jpg
There is also a mark for Connah's Quay No.1, with '(UP)' appended, but that doesn't make much sense since CQ No.1 clearly controls both up and down lines.

And here is an extract from the 25" Ordnance Map, 1909-1910 revision, on which I have attempted to correlate the 'S.P.' markings with the diagrams in this thread:
Shotton 25 inch extract.jpg
There remains a query about the posts between the Shotton footbridge and the nearby Great Central bridge. I don't think these can be the Queensferry up home signals, but there is no trace on the plan of a box to control them at Shotton.

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Re: how to interpret this diagram?

Postby grovenor-2685 » Wed Jan 30, 2019 3:48 pm

Shotton's lack of a box is a bit of a puzzle. Here is an extract from the Railway Magazine's 'Gradients of the British Main-line Railways' 1947 edition, suggesting that there was a block post at Shotton:

There does not seem to be any reason for a block post at Shotton, the Queensferry - CQ1 section is already short so it would not add any line capacity.
I don't think the gradient diagram distinguishes between stations with or without block posts. The extra SP on the ordnance map is probably just some other post or a simple error.
Rgds

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Re: how to interpret this diagram?

Postby John Palmer » Thu Jan 31, 2019 1:06 pm

The 'Gradients' book is inconsistent in its approach to which locations are to be marked and which are not - e.g. the scanned extract I posted includes a marker for Connah's Quay No.1 box, but makes no attempt to identify separately multiple boxes at short distances from each other.

I don't disagree about the absence of any obvious reason for a further block post at Shotton, but as it happens the OS plan is not in error. Near the foot of the page at http://www.6g.nwrail.org.uk/northwalesstations.htm you will find a photograph of Shotton Low Level said to date from the late 1930s with the signals marked on the OS plan clearly present. These are the ones I have marked '??' on the extract from the 25 inch plan.

So what signals are these? They are located closer to CQ No.1 than to Queensferry, but neither post is carrying a distant for Queensferry signals. The left hand arm is ringed. Is it remotely possible that these are Queensferry's nos. 56 and 59, and that the ringed arm reads over the Queensferry Up Fast to Up Slow crossover? Although it seems unlikely to be the explanation, I raise this possibility because, whilst I can find a mark on the 25 inch plan that probably accounts for Queensferry 50 and 53, there is no obvious marking on the plan for 56 and 59 in the position in which you would expect to find them.

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Re: how to interpret this diagram?

Postby Noel » Thu Jan 31, 2019 4:28 pm

John Palmer wrote: The left hand arm is ringed. Is it remotely possible that these are Queensferry's nos. 56 and 59, and that the ringed arm reads over the Queensferry Up Fast to Up Slow crossover? Although it seems unlikely to be the explanation, I raise this possibility because, whilst I can find a mark on the 25 inch plan that probably accounts for Queensferry 50 and 53, there is no obvious marking on the plan for 56 and 59 in the position in which you would expect to find them.


If you follow the map as far as it goes, there are signal posts marked just before the crossover on the approach to Queensferry, which is a mile away from Shotton, so these are probably 56/59, I would suggest. [Incidentally, what is signal 50?] The map shows SPs [presumably plural] so, given the gradient up to Queensferry, and the presence of the station, are these Queensferry outer homes post dating the diagram, put there so that trains can be accepted past CQ No2's starters into Shotton station even if the clearing point beyond Queensferry's homes is fouled?
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Re: how to interpret this diagram?

Postby John Palmer » Thu Jan 31, 2019 7:27 pm

Your eyes are obviously better than mine!

I had picked out a mark for what I took to be Queensferry's 50 and 53 prior to my previous post, but yours prompted me to take a closer look at the 25 inch ordnance plan. It was only then that I saw a smaller than usual mark in the right place for 56 and 59. I've shown these on the attached extract:
Queensferry Up Homes.jpg
This also makes sense of the 'S.Ps' annotation on the plan indicating plural signal posts.

If you want to provide for admission of trains into the Shotton Up Slow platform when Queensferry can't accept it, surely the simpler solution is to provide CQ No.1 with advanced starting signals exactly where the questioned signals are located? Since the need for such a provision is only going to apply to the slow line, is there any compelling reason in such a case for doing nothing more than re-siting CQ No.1's existing Up Slow starting signal (29) to the east end of the Shotton platform?


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