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Interlocking of slip points

British signalling of the past (UK, excepting Northern Ireland)

Interlocking of slip points

Unread postby John Hinson » Sun Mar 5, 2017 1:33 pm

There were many different ways that double-slip points were linked to signal boxes but there is one way that has always puzzled me - it can be seen in this 1986 diagram of Penmaenmawr - https://signalbox.org/diagrams.php?id=1144 . This arrangement could never be described as common but examples were quite widespread until branch line and goods yard closures eliminated most of them.

My question relates to departures from the "Down Neck" or "Down Refuge Siding" (I have my suspicions those names are wrong) which actually use the same shunt signal. From the Neck you require to pull 12 & 11 points but from the Refuge you need 12, 11 & 10. So what is to stop you setting for a departure wrongly, and running-through and damaging 10 points?

One possibility would be that 10 points are trailable, I have seen trailable mechanical points elsewhere but they are rarely marked as such on diagrams.

Would the locking allow you to move 10 points if you realised an error had been made?

I am really asking for first-hand information rather than opinion, which is why I am asking about a late example. I don't know when it went, but satellite photographs suggest that area is now plain-lined.

John
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Re: Interlocking of slip points

Unread postby davidwoodcock » Sun Mar 5, 2017 2:08 pm

Looking at the diagram, I wondered why 15 wasn't "Y" but came to the conclusion that its locking requires 10 normal, and probably 11 and possibly 12, too, (although 12 would probably be dependent on the lie of 14, so perhaps 12 and 14 are interlocked instead), and that 15 had to be pulled off to allow access to neck or refuge siding as well as the main (and that, therefore, it may well have been normally left reversed during shunting).
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Re: Interlocking of slip points

Unread postby John Hinson » Sun Mar 5, 2017 4:01 pm

davidwoodcock wrote:Looking at the diagram, I wondered why 15 wasn't "Y" but came to the conclusion that its locking requires 10 normal, and probably 11 and possibly 12, too, (although 12 would probably be dependent on the lie of 14, so perhaps 12 and 14 are interlocked instead), and that 15 had to be pulled off to allow access to neck or refuge siding as well as the main (and that, therefore, it may well have been normally left reversed during shunting).

It certainly used to be yellow: https://433shop.co.uk/index.php?route=p ... ct_id=1394

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Re: Interlocking of slip points

Unread postby Mike Hodgson » Sun Mar 5, 2017 8:33 pm

That is a fairly big locking change if the only thing you wanted to alter was the colour of 15 disc. Was this part of a bigger job such as a frame replacement/relocking , if not why was it changed ? Was there concern that a train setting back into Down Refuge Siding was not protected by a yellow 15 if you have something in the Up Sidings, perhaps a refuged Up train? Maybe one of those spares 16-20 once worked a dolly nearer the double slip -in which case I am happier with 15 being yellow

I can understand the crossover between the Down Refuge Siding and the Down Neck being hand worked if it is mainly used for shunting. However, the nomenclature (if correct) suggests that wasn't the original purpose of the siding - which might have changed over time with traffic demands? If you want to refuge a Down train into the siding, you don't want to have to leave the box to work the hand point - it would be easier if 10 had once worked the crossover too, although that would interfere with shunting. So would that point have to be trailable too?

You said you had your doubts as to the Down siding names - with the layout as shown, I think I would be happier if those names and usages were simply transposed, but maybe not possible due to siding lengths etc
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Re: Interlocking of slip points

Unread postby davidwoodcock » Sun Mar 5, 2017 9:13 pm

Mike Hodgson wrote:You said you had your doubts as to the Down siding names - with the layout as shown, I think I would be happier if those names and usages were simply transposed, but maybe not possible due to siding lengths etc


According to the Old Maps site, the two sidings formed a terminal loop, so were effectively much the same length - and anything put in one could be run round using the other (subject to its being clear, of course).
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Re: Interlocking of slip points

Unread postby Sharpey » Sun Mar 5, 2017 9:40 pm

A similar situation existed at Stafford No. 4 into the Siding 1&2 / Down Sidings, I believe pretty much right up to when it closed although the sidings may have fallen out of use in the latter stages.

This involved mechanically worked 72B/C and 73 points as 3 parts of the double slip, 72 A being the Down Slow trailing end. the signal in this case covered the exit from all of the named sidings and was again Yellow. The other part of the arrangement was again a handpoint and was in the "Signal Engineers Siding" which had no signal to exit being entered past the yellow ground signal.

At one point during a track renewal project we looked at modifying this to a fully motored arrangement, but with locking and control alterations can of worms that that this opened and the finiancial implications this was deemed to be unecessary.
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Re: Interlocking of slip points

Unread postby Mark Lamb » Sun Mar 5, 2017 10:57 pm

Good evening John,

I can confirm that 10 points were lever worked, and not trailable. The normal operation at Penmaenmawr was for an empty stone train to arrive on the Up and stand behind 13 shunt signal. The road would then be set into the Refuge, and the train propelled through 10 points facing. Once inside, the loco would run-round via the Neck and then propel the empties into the Up Sidings for loading with ballast. (It could have set back into the Neck and run round via the Refuge, but this would involve uncoupling next to a running line, so I don't think it was done that way). Loaded trains - or light engines - left via 14 points. On the rare occasions that a train went westwards, it would leave via 10 trailing but this was unusual. I think a similar layout existed at Talacre, further along the coast.

With regard to your drawing, a plan I have (CS 3/75 - Provision of AWS) shows 25 signal still as a three-aspect with the top as an unlit auxillary, as you surmise. As to naming of lines: a copy of a 1968 plan shows the Neck next to the Up Main, with the Refuge beyond. On the Locking Diagram CL 50 - 150 (but pencil annotated "into use Dec 7th 1952"), the Neck is called as such, but what became the Refuge was originally called Refuge Siding. Finally, the locking for 10 requires 12 and 11, so if a mistake had been made it would be possible to change its lie once 8 was put back.

Mike - 16 and 20 were always spare; levers 17, 18 & 19 were associated with a 'traditional' goods yard at the Bangor end of the layout. Penmaenmawr employed a shunter (person!) in the Sidings, and all movements were under his authority.

Regards,

Mark
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Re: Interlocking of slip points

Unread postby Mike Hodgson » Mon Mar 6, 2017 12:23 am

Thanks Mark. I take it trains weren't often refuged there at least in more recent times, and the signalman would communicate with the shunter if they ever needed to be and he would set the hand points before a train was refuged or released
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Re: Interlocking of slip points

Unread postby John Hinson » Mon Mar 6, 2017 2:28 pm

Mark Lamb wrote:I can confirm that 10 points were lever worked, and not trailable. The normal operation at Penmaenmawr was for an empty stone train to arrive on the Up and stand behind 13 shunt signal. The ....
(snipped)


Mark - that is exactly the sort of answer I was after, but thought I was being too optimistic. Brilliant, thanks very much!

Although not the original matter being discussed I would like to get to the foot of whether 15 disc was always yellow before I update my diagram. I have found an undated sketch of the box diagram which is obviously later than my 1986 one as all running signals are colour-light. This shows 15 as yellow, so one of the two versions must surely be wrong!

I have found one of Norman Cadge's photographs which shows the track had been plain-lined there by 7/10/93. 2006 satellite images suggest the connections were replaced by single-lead connections at the other end of the sidings allowing direct arrivals and departures. The trackwork looks pretty unloved, even in 1993, so I don't suppose the lovely new pointwork saw much traffic.

Mention has been made above of Western Region practice and Talacre. In my experience, this arrangement was not at all common on the WR - the two common methods being working 10 and the "lower" (per the diagram) end of 11 from one lever, and providing two outgoing discs (e.g. Broadway: https://signalbox.org/diagrams.php?id=51 ). The other method was to make the equivalent of 10 hand-worked and to provide only one disc (e.g. Bilston Central: https://signalbox.org/diagrams.php?id=577 ). In fact, the latter is the commonest way to signal a double-slip in a yard couintry-wide, and was also in fact the way both of the double slips at Talacre were configured.

Best regards,

John
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Re: Interlocking of slip points

Unread postby beast66606 » Mon Mar 6, 2017 6:15 pm

I photographed most of the signals down the "coast" for several years starting from 1976/7 (running and shunts), unfortunately not readily to hand, but my memories of that signal are only as per your photo John - a stretched yellow.
Better to be thought a fool than to type a response that confirms it.

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Re: Interlocking of slip points

Unread postby Mark Lamb » Mon Mar 6, 2017 9:32 pm

I'm pretty certain that 15 was always a yellow disc from original commissioning in 1952 (following the Irish Mail collision of 1950), until recovered when the approaches to the yard were relayed in ?

The name and pull plates for the locking diagram for 1952 only refer to one disc at the exit from the yard, and though the lever colour is shown as red - as were all yellow discs that I met - all other levers are accounted for. So it must have been brought into use as a single disc, as it would have required two discs if red. My copy of a c.1968 plan, and the 1975 plan shows it as yellow too.

Though the yard was quite long, some of the sidings were close to the yard exit. As some shunting past 15 took place, a yellow disc was a logical choice.

Regards,

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Re: Interlocking of slip points

Unread postby davidwoodcock » Mon Mar 6, 2017 9:47 pm

Mark Lamb wrote:I'm pretty certain that 15 was always a yellow disc from original commissioning in 1952 (following the Irish Mail collision of 1950), until recovered when the approaches to the yard were relayed in ?


The equivalent signal prior to the 1950 accident was also a yellow disc (as per the accident report).
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Re: Interlocking of slip points

Unread postby John Hinson » Tue Mar 7, 2017 9:56 am

OK, thanks, all, - I accept that it was probably yellow throughout although I don't rule out conversion to a red plate either because no yellow ones were available for renewal (I worked at a box with three yellow discs on the diagram that were actually red for that reason) or a change after unintendedly running through 11 points (or in anticipation thereof). I expect I will find a late-period photograph eventually.

But I shall regard it as always yellow for now.

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Re: Interlocking of slip points

Unread postby StevieG » Tue May 9, 2017 11:42 am

FWIW John, over time I have seen one or two saved box diagrams, probably old enough to be at least GNR-era, which showed double-slip yard accesses apparently arranged and worked as per 'your' Penmaenmawr 10 - Baldock is the one that most readily springs to mind - whereas later LNE/BR(E) versions of the same place show the equivalents of P10 as changed to handpoints with the relevant levers then amongst the Spares.
BZOH

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