One lever, two signals

[Reorte]

Looking at a diagram for Kirkby Stephen East (the junction box on the closed station on the Stainmore line, not the Settle-Carlisle one) there are a few levers that appear to operate two signals, e.g. "South Siding Down or To Tebay", the signals themselves (two dolls next to each other) being labelled "14A and 14B". How did this work? I'm assuming that which signal went off would depend on how the relevant points were set. That particular one only has one set of points after it, but others have more - presumably the interlocking would require a valid complete route, or just depend on the next points? And could all of this be arranged mechanically?

[bécasse]

A device called a selector, linked to the relevant points, determines which of the two signals will go off when lever 14 is pulled. Similarly, the interlocking will incorporate some conditional interlocking (again determined by the N/R position of the relevant points) so that the appropriate complete route is locked (and conflicting routes locked out) when the lever is pulled.

 

Only certain types of mechanical interlocking, most notably tappet locking, could provide conditional interlocking, but if the interlocking was suitable or could be made so, the use of selectors was a convenient way of providing extra signalling functionality when no spare levers remained and extending the frame would have been at best expensive or at worst impractical.

[5BarVT]

2 hours ago, bécasse said:

Similarly, the interlocking will incorporate some conditional interlocking (again determined by the N/R position of the relevant points) so that the appropriate complete route is locked (and conflicting routes locked out) when the lever is pulled.

Yes for selection through facing points.

If the selection is which of two discs at trailing points then it can be done without conditional locking, just ‘both ways’ on the trailing points.

See Helston 1956 (twist frame before the 58 tappet frame went in) lever 4.

Paul.

[The Stationmaster]

Arranging it mechanically was actually very simple.    The wire which worked the two selected signals ran from one signal to the other and between the two it ran round a horizontal pulley wheel.  The pulley wheel was set on a base plate which could slide to and fro and this baseplate was pulled by the wire from the signal box.   Thus when the signal lever was pulled the pulley wheel moved and the wire to the two signals was pulled.  At a facing point the wire to each signal ran through a detector which only allowed the wire to that signal to operate if the point was correctly set for the route from that signal.  Thus when the pulley wheel was pulled only the wire to the two signals could also move as the other was stopped by the detector.  No doubt other types of selector mechanism probably existed but they all worked on the same basic principle where the position of the point determined which signal could clear

 

I don't have a photo of a selector but the one below shows a detector where you can see the notch which when  the point is set aligns with a notch in the other detector slide which is in the route of the signal wire.  If the two notches do not align the signal wire cannot move and the signal will not operate.

 

[LNERGE]

Here's one i made earlier..

 

[LNERGE]

I have another to do soon. 5 is selected by 8 and 10 disc reads both ways.. Conflicting notches to watch out for.

 

Edited August 3, 2022 by LNERGE

[Nick C]

On 03/08/2022 at 17:11, LNERGE said:

I have another to do soon. 5 is selected by 8 and 10 disc reads both ways.. Conflicting notches to watch out for.

 

What's the difference between the different track circuit markings there (the '[' by the shunt signals and '-' by the running signal)? Would I be right in thinking that the loop and single line are not track circuited but the platform road is?

 

I wonder if there were examples of more than two arms being selected off a single lever - or even more confusing, selected arms off a push-pull lever...

[Titanius Anglesmith]

1 hour ago, Nick C said:

 

I wonder if there were examples of more than two arms being selected off a single lever - or even more confusing, selected arms off a push-pull lever...

Yes there were, eg 20’s lever at West Thurrock Junction 

 

https://signalbox.org/~SBdiagram.php?id= 1221

[micknich2003]

Here is a typical text book drawing. Of interest, the arrangement can also be adopted to work the other way round, ie one signal worked off either of two levers.

 Raynor Wilson in his c1900 tome illustrates a means of working 7 (From memory) signals from the same lever.

[micknich2003]

The attached Drawing shows examples of "Selected Signals", plus also a few other long forgotten bits of mechanical equipment

[5BarVT]

On 05/08/2022 at 16:10, Nick C said:

selected arms off a push-pull lever...

Yes, Loco Yard GF at Sheffield Park on the Bluebell Railway.  Four signals operated by one lever.  To add more complication, two of the signals are also slotted.

Paul.

P.S. Thanks to St.Enodoc for linking the box diagram on his thread, without which I wouldn’t have been able to quote this example.

Edited August 7, 2022 by 5BarVT
Acknowledgement

[DavidBird]

On 03/08/2022 at 11:43, The Stationmaster said:

Arranging it mechanically was actually very simple.    The wire which worked the two selected signals ran from one signal to the other and between the two it ran round a horizontal pulley wheel.  The pulley wheel was set on a base plate which could slide to and fro and this baseplate was pulled by the wire from the signal box.   Thus when the signal lever was pulled the pulley wheel moved and the wire to the two signals was pulled.  At a facing point the wire to each signal ran through a detector which only allowed the wire to that signal to operate if the point was correctly set for the route from that signal.  Thus when the pulley wheel was pulled only the wire to the two signals could also move as the other was stopped by the detector.  No doubt other types of selector mechanism probably existed but they all worked on the same basic principle where the position of the point determined which signal could clear

 

 

If you're ever up in The Highlands, we've 2 pairs on the Strathspey Railway.  One pair of these are the signals at the south end of Aviemore station which gives access from NR onto the SR.  They are operated by the ground frame, and so all the workings are easily visible from the station platform, the only difference from Mike's description being the pully is mounted on and operated by channel rodding rather than a baseplate pulled by wire.

Edited August 9, 2022 by DavidBird

[Reorte]

Thanks for the explanations, I'd assumed that this was something that would have had to have somehow been arranged in the locking, but it appears to be rather less complicated than that (and something to bear in mind if I ever do model the bit I was looking at; it's one of those "now what could I do with this?" ponderings).

[DavidBird]

 

11 hours ago, DavidBird said:

 

If you're ever up in The Highlands, we've 2 pairs on the Strathspey Railway.  One pair of these are the signals at the south end of Aviemore station which gives access from NR onto the SR.  They are operated by the ground frame, and so all the workings are easily visible from the station platform, the only difference from Mike's description being the pully is mounted on and operated by channel rodding rather than a baseplate pulled by wire.

 

Here seen during istallation, the floating pulley wheel mounted on the channel rodding, crank to the lever frame and the point detectors for the facing point beyond.

 

 

Here after installation, the pulley wheel with chain, the ends of the chain are attached to the wires to the point detector, the return wires from the detector to the signals passing over the whole assemby to the signals seen in the background.  Also note the detector boxes on the GF, which interface with the NR Inverness signalling centre.

Yes, it was a very wet day that day! Two of us ended up being tentpoles for a piece of tarpaulin to shelter the innards of the dis-box from the worst of the weather as it was being wired up!

 

 

And the signals that are both controlled from the GF lever 5, the main arm reads to the platfrom and the small arm to the loop, depending on the setting of the points.  Formerly from Forres.

 

 

For more see here

http://ontrackatstrathspey.blogspot.com/2019/03/s-progress-at-aviemore-1617-march-2019.html

https://signallingstrathspey.blogspot.com/search?updated-max=2020-05-20T17:03:00%2B01:00&max-results=7&start=10&by-date=false

[Michael Hodgson]

1 hour ago, DavidBird said:

Yes, it was a very wet day that day! Two of us ended up being tentpoles for a piece of tarpaulin to shelter the innards of the dis-box from the worst of the weather as it was being wired up!

 

That sounds like the Aviemore I know and love !  Except it's usually snow when I visit little brother at Xmas/Hogmanay.

[LNERGE]

3 hours ago, DavidBird said:

 

 

Here seen during istallation, the floating pulley wheel mounted on the channel rodding, crank to the lever frame and the point detectors for the facing point beyond.

 

 

Here after installation, the pulley wheel with chain, the ends of the chain are attached to the wires to the point detector, the return wires from the detector to the signals passing over the whole assemby to the signals seen in the background.  Also note the detector boxes on the GF, which interface with the NR Inverness signalling centre.

Yes, it was a very wet day that day! Two of us ended up being tentpoles for a piece of tarpaulin to shelter the innards of the dis-box from the worst of the weather as it was being wired up!

 

 

And the signals that are both controlled from the GF lever 5, the main arm reads to the platfrom and the small arm to the loop, depending on the setting of the points.  Formerly from Forres.

 

 

For more see here

http://ontrackatstrathspey.blogspot.com/2019/03/s-progress-at-aviemore-1617-march-2019.html

https://signallingstrathspey.blogspot.com/search?updated-max=2020-05-20T17:03:00%2B01:00&max-results=7&start=10&by-date=false

A nice robust looking job. 

[5BarVT]

8 hours ago, DavidBird said:

 

Not interlocked with the gates I see!

(Greetings to Mr M (S&T Engineer) from a former colleague.

Paul.

[The Stationmaster]

16 hours ago, 5BarVT said:

Not interlocked with the gates I see!

(Greetings to Mr M (S&T Engineer) from a former colleague.

Paul.

An interesting area - as that is almost certainly not a statutory level crossing there would have been no legal reason to interlock the crossing with any signals.  

 

However if I were today carrying out an operational safety audit of the line and taking also into account contemporary views of the Railway Inspectorate plus what the ORR nowadays regard as what constitutes 'a level crossing' I would be proceed as follows:-

1.  I would need to see and review all the relevant risk assessments which should take int account various factors such as frequency of use of the crossing,  potential frequency of a collision between a rail movement and all classes of crossing user, potential consequences of any such collision (the latter will obviously be well into the red area).

2.  Having seen the risk assessment I would then wish to examine all the relevant published Instructions regarding the use and operation of the crossing and the involvement of the signal box, Signalman, and crossing users.  Regrettably the photo, in addition to showing conflicting signal/gate target indications, suggests that such Instructions as do exist do not take account of potential risk or are not being correctly applied and might need to be supplemented by some sort of physical control (e.g. interlocked gate stops etc, etc).

3.  It would be helpful to also see the railway's training plan and their methods for holding records of staff competency (e.g in relation to any Instructions for the safe operation of this crossing)

4.  I would advise such measures as should be introduced to reduce risk potential to such a level as to be as low as reasonably practicaablel (ALARP).

 

I would however also advise the railway that, as I no longer carry any professional indemnity insurance, my audit and advice would be o na purely non-professional basis in order to give them an idea of what they should be doing to reduce risks at. this location to the lowest reasonably practicable level.