Leads on GWR levers especially ground disks

[Junctionmad]

Can someone explain generally how the GWR and perhaps BR(WR) arrived at the text on the leads specifically in relation to disk signals, I generally have the text for the running signals worked out , but as yet struggle to arrive at leads for the ground disks 

 

thanks 

 

dave 

[The Stationmaster]

Later examples usually seemed to read 'Disc at [point number] then below the line the lead numbers which could be followed by a second horizontal line and 'OR' before a second list of lead numbers (or even more lists for multi route discs).

[Junctionmad]

Thanks , were the lead numbers other points on the route , and was the “ or” list , the leads that applied when the lever was reversed ?

 

For example , could you pick a disk here and suggest how the lead for the lever plate was constructed

 

 

Thanks

Edited April 13, 2018 by Junctionmad

[Junctionmad]

I’m still a bit confused here’s a few images of leads

 

Would someone “decode “ these in relation to the lever normal and reversed ( obviously I can follow the purely text ones !)

 

How come the “ down main home “ had lead numbers as well

Thanks

Edited April 13, 2018 by Junctionmad

[RailWest]

In simple terms:-

 

The number at the top is the number of the lever.

The text is the description of the item that it controls. If that is a point, then the extra text below the 'bar' tells you to what it leads when reversed.

The list of 'lead' numbers tells you what other levers need to be pulled first in order to release 'this' lever.

The 'OR' provides alternatives lead lists where conditional locking applies (eg a shunt disc reading for more than one route etc)

 

In the case of '2' Down Main Home then it may be the case that there is a FPL ahead, or perhaps more than one route to the next signal, so a point which may or may not be reversed etc.

[HAB]

For example , could you pick a disk here and suggest how the lead for the lever plate was constructed

 

 

 

24

Disc at 23

23

OR

21,23

OR

19,21,23

 

Not sure I understand what you are finding difficult here?

 

Cheers,

[Junctionmad]

More reading has illumated some things my understanding are the leads mentioned are where the relevant levers had to be reversed in the frame , normal not being mentioned

 

“ or” referring to an alternative route again where the relevant levers had to be reversed

 

I do notice common signals like starters don’t generally have leads described , was this because the route was with all levers normal or simply expediency ? , surely any fpls had to be reversed to lock , would these not have been on the starters leads

[Junctionmad]

24

Disc at 23

23

OR

21,23

OR

19,21,23

 

Not sure I understand what you are finding difficult here?

 

Cheers,

Thanks , I’m beginning to appreciate the format , my understanding is the lead numbers purely referred to levers that had to be reversed in the frame ?

 

It’s not a subject I had considered recently

[HAB]

.. perhaps I understand your misunderstanding now since you talk about Normal or Reversed...

 

The "Lead" plates denote which levers LEAD in other words they read "Before you can pull this lever, you must pull these...  OR  these... OR these.  etc no levers being "normal" are ever mentioned nor is there any reference to the lever in the R position.  Hence why you will often see NIL.  To take your plate for 16 FPL.  This reads that before you can pull 16, you must pull either NIL OR 17.  Why say that? Because 16 locks 17 either way (N or R).

 

Hope that is clear.

[HAB]

Here is a nice one from Exeter West This is taken from my signalbox simulation programme - the real one has fewer abbreviations!

 

[Junctionmad]

.. perhaps I understand your misunderstanding now since you talk about Normal or Reversed...

 

The "Lead" plates denote which levers LEAD in other words they read "Before you can pull this lever, you must pull these... OR these... OR these. etc no levers being "normal" are ever mentioned nor is there any reference to the lever in the R position. Hence why you will often see NIL. To take your plate for 16 FPL. This reads that before you can pull 16, you must pull either NIL OR 17. Why say that? Because 16 locks 17 either way (N or R).

 

Hope that is clear.

My understanding of frame terminology was a lever pulled is also referred to as “reversed “ in the frame , therefore the leads mentioned only refer to levers that must be reversed , ie “ pulled “ , the assumption being leads not mentioned are because the levers are normal in the frame

 

( for example I’ve seen leads that just mention the FPL lever , the assumption must that the point lever is in the normal position in the frame and it’s the fpl that must be pulled , ie leads don’t mention levers that don’t have to be pulled ( even if they are subsequently locked )

 

Am I right here ?

Edited April 13, 2018 by Junctionmad

[Junctionmad]

I presume the text only leads refer to the two routes , ie when the Lever is normal and when it’s reversed

 

Ie “ up goods running loop facing | up main , the first when the lever is normal and the 2nd when it’s reversed

 

In this case , how come no lead numbers are mentioned ? , is this assumed

[HAB]

Correct except the (possibly) the last bit.

 

The "text only" plate is not a "lead", it is just a "description".  So it just says this is the point from the G loop towards the main without necessarily implying which way the lever works - you would have to at the diagram to understand exactly what what that meant.  Since there are no numbers, there are no "Leads", which means it can be pulled provided the other levers which lock it are all normal - nothing else needs to be reversed first.

 

It is pretty difficult to reverse engineer a diagram or the locking just from the descriptions because they are so general or abbreviated.  They are intended just as an aide memoire to a busy signalman who actually already knew the layout pretty well.

 

Cheers,

[The Stationmaster]

I presume the text only leads refer to the two routes , ie when the Lever is normal and when it’s reversed

 

Ie “ up goods running loop facing | up main , the first when the lever is normal and the 2nd when it’s reversed

 

In this case , how come no lead numbers are mentioned ? , is this assumed

 

Because it's a point lever and no other levers need to be pulled before it in order to release it.

 

In the example leads you posted pictures of the lead for 16 is slightly different because it is the FPL for 17 and bolts it both ways - hence 'Nil' OR 17.  But in thise case No. 16 lever will lock No.17 in either position (i.e. either at normal or at reverse) hence if 17 is to be reversed to change the route it has to be pulled before 16 because if 16 is pulled first 17 would be locked at normal.

More reading has illumated some things my understanding are the leads mentioned are where the relevant levers had to be reversed in the frame , normal not being mentioned

 

“ or” referring to an alternative route again where the relevant levers had to be reversed

 

I do notice common signals like starters don’t generally have leads described , was this because the route was with all levers normal or simply expediency ? , surely any fpls had to be reversed to lock , would these not have been on the starters leads

 

As far as Starting Signals are concerned it depends entirely on where they are and their purpose - in some situations they will definitely have leads because points need to be reversed and an FPL bolted in order to release the signal lever in the interlocking to allow the signal to be cleared.  

 

In most cases (but not all!) Section Signals are unlikely to be led by any other lever but depending on the date when the lever lead was renewed it might well state 'Line Clear'  as the lead because the signal is released by Line Clear being pegged on the block instrument for the section in advance.

[The Stationmaster]

Correct except the (possibly) the last bit.

 

The "text only" plate is not a "lead", it is just a "description".  So it just says this is the point from the G loop towards the main without necessarily implying which way the lever works - you would have to at the diagram to understand exactly what what that meant.  Since there are no numbers, there are no "Leads", which means it can be pulled provided the other levers which lock it are all normal - nothing else needs to be reversed first.

 

It is pretty difficult to reverse engineer a diagram or the locking just from the descriptions because they are so general or abbreviated.  They are intended just as an aide memoire to a busy signalman who actually already knew the layout pretty well.

 

Cheers,

Agreed but I once knew an extremely competent Locking Engineer who could do a full frame mechanical locking test solely off the 'box diagram and the lever leads (although he invariably had the locking chart and electrical control table not far away to use as a double check) but I have seen him test locking alterations entirely off lever leads.

[HAB]

Agreed but I once knew an extremely competent Locking Engineer who could do a full frame mechanical locking test solely off the 'box diagram and the lever leads (although he invariably had the locking chart and electrical control table not far away to use as a double check) but I have seen him test locking alterations entirely off lever leads.

 

Ah! We might might both have known the same chap!  But such people are a breed apart from the rest of us!

[RailWest]

A caution on FPLs.....

 

Practice in the UK varied as to whether FPLs stood normally 'out' (ie you pulled the lever to lock the point) or normally 'in' (ie you pulled the lever to unlock the point). Some companies (such as the GWR) favoured the former, others favoured the latter; it was not unknown also to have both methods used in the same frame!

 

Even where the normally 'out' method was used, if the frame was simply a ground-frame that was normally locked-up 99% of the time and only released as/when required, if there happened to be one of more FPLs in its layout then they might be done by the normally 'in' method instead (presumably just to keep the frame 'tidy' most of the time).

[Grovenor]

Ah! We might might both have known the same chap!  But such people are a breed apart from the rest of us!

Testing from the leads would not work unless the leads are thoroughly checked first, who is to say there is no error in the lead plates? On the other hand a principles tester would be expected to test from the box diagram, after checking its the updated version, then the test proves both the interlocking and the locking table and allows for any discrepancy to be investigated. In theory the locking table would have been checked and approved and hence should be error free, but in practice that is not always so, hence the principles tester gives another opportunity to find errors.

Regards

[micknich2003]

Testing from the leads would not work unless the leads are thoroughly checked first, who is to say there is no error in the lead plates? On the other hand a principles tester would be expected to test from the box diagram, after checking its the updated version, then the test proves both the interlocking and the locking table and allows for any discrepancy to be investigated. In theory the locking table would have been checked and approved and hence should be error free, but in practice that is not always so, hence the principles tester gives another opportunity to find errors.

Regards

Here's an example of a wrongly drawn locking chart. I have worked in or know of signalboxes that had incorrectly engraved lever plates or descriptions.

[TheSignalEngineer]

I used to do some frame tests after alterations. I would set each move in turn based on what I expected from the Signal Box Diagram, having previously checked that it matched the approved signalling plan. As each lever was pulled I would check that any confliction created was locked. I used an assistant to mark off what I had tested to the locking chart and to check that the lever plates matched what i had called out as I set the move.

 

Other people I worked with on locking maintenance started with a blank locking chart and wrote down what they had tested as they did it. After that they would cross check their sheet with the office record locking chart.

[The Stationmaster]

Ah! We might might both have known the same chap!  But such people are a breed apart from the rest of us!

 

Who smoked a particular brand of menthol cigarettes - a careful wheeze to help when he'd accepted a cig from somebody else but they didn't like his idea of a nice cigarette.  My biggest achievement in mechanical signalling (don't forget I was an operator who was well into signalling) was when John checked a locking chart I had drawn up for a 'box at a preservation site, with some quite complex locking including a king lever, and he signed it off as 'correct'.  Lovely fellah.

[Junctionmad]

Thanks folks , most illuminating

[5BarVT]

Lovely fellah.

Agreed.

I learnt what I know about frame testing from him.

Paul.