Absolute Blocks at a Pre-Group Terminus

[Lacathedrale]

I'm building a Minories station based on late 19th Century LNWR ex-LCDR SE&CR practise, and hoping to include some signalling on the layout. Cyril Freezer detailed his view of the signalling for Minories in his book Model Railway Signalling:

 

 

However, I am looking to model beyond the platform home signals (1) and shunt signal (5) depicted in his diagram, as my layout will have a train-length curve between the throat of the station and the fiddle yard.

 

I'm not sure which main line is better for the station's block section to extend into. Without further information, I believe the breakdown of block sections would look like this:

 

A. Station Signalbox Block extends onto up Main

 

 

I have made the following assumptions, please let me know if I'm mistaken!

 

1. Due to the location of the two sidings, extending the block onto the Up Main makes the most sense, so the signal boxes do not have to negotiate a 'shunt into forward section' every time.
2. The length of the block section and the provision of an advanced starter is to provide a full train length for the station pilot to shunt into.
3. Because the advanced starter is present, there's no need for a limit of shunt board on the up Main, since a shunt signal from the two red sidings would only permit movements up to that section signal anyway.
4. Cyril Freezer's signal gantry with the calling on arms would work for light-engine movements from the fiddle yard, but another shunt signal for backing movements from the Up Main into the platform roads by the station pilot will be required.

 

Blue (FY) sending a train to the station:

A

1. Blue starter and Red home/distant signals are at danger by default
2. Blue sends the relevant call to attention and train bell code, which are acknowledged by repeating by Red.
3. Red sets 'line clear' which in modern times would unlock the red home and distant signals - but just by following rules in earlier periods - and sets route and signals.
4. Blue signal box may now pull off its starter signal, and the Red distant signal may come off due to slotting if pulled by Red in the previous step.
5. Blue signalbox sends a 'train entering section' bell code as it passes the starter.
6. Red  acknowledges by repeating the bell code and sets commutator to 'train on line'.
7. Blue restores their starter to danger after the train is clear.
8. After train is clear, Red restores his home/distant to danger and sends 'train out of section' bell code to blue.
9. Blue acknowledges by repeating bell code.
10. Red sets the commutator to 'normal', and the process can start again.

 

I'm not 100% on the order of operations in the last few items, and what they block or permit, or are blocked by - it would be easy to make sweeping statements but I just don't know even after all the bloody books I've read!

 

EDIT: I will put together a more detailed signalling diagram in due course for review, but for now I'm mostly focused on the location of the block sections and the handing of trains between them!

 

 

Edited December 16, 2021 by Lacathedrale

[Michael Hodgson]

Several subtleties come to mind ...

 

• Limit of shunt board would not be provided there anyway - if a shunt ahead signal is provided or the driver is authorised to shunt beyond starting signal  he may only proceed as far as necessary for the shunt (ie train length) unless the starter is cleared.  Limit of Shunt boards are usually for shunts in the wrong direction.
• Distant and stop signals on the same post - semaphore  distant is mechanically slotted with stop arm, so that you cant't have distant off unless stop arm is also off.  this means when your blue starting signal is put back, distant will automatically also drop back even though its levers is still reversed.  Likewise the signals on the opposite line.
• Those signals are (traditional practice) only  put back after the whole train has passed the signal, because the Guard used to be required to observe the signal and should (in theory) apply emergency brake, because if he sees it going back too early it may indicate an emergency.  The rule that Firemen and Guards should observe signals was a theoretical safeguard against a driver asleep at the controls (not very common on steam locos!) , but ineffective as the view from a passenger brake van was too limited and whenever a driver did pass a signal at danger, the Guard always claimed that he was sorting parcels or inspecting a ticket or writing his journal at the time.  However this requirement does not apply to modern practice where colour lights are restored as soon as the first axle enters the next track circuit; the fiction that Guards spend the journey squinting out of a ducket to observe signals has been removed from the rules.
• In addition to that, in the case of signals protecting points (which applies to the Home Signal) it may only be put back to Danger after the whole of the train has cleared those points.  This is to safeguard the signalman from being over-enthusiastic and changing those points under the train in preparation for the next movement (the signal still being off will keep the points locked)  In practice here the train will have just come to a stand in the platform.  Particularly on a single line it would take a few moments for him to go back into the box having been outside collecting the staff/token,
• Turning the block to Train on Line is part of the acknowledgment of Train Entering Section.  A few pre-group companies didn't repeat the 2 beats - the movement of the block indicator constituted the acknowledgment.
• The whole of the train has to have passed the box before Train Out is sent, because otherwise the signalman can't see the tail lamp.  There are special rules where trains don't pass the box.  For example at Loughborough on the preserved Great Central, an inspector advises him that the train has arrived complete.  The Guard would give a hand signal where a train is shunted into a siding without passing the box.  In modern practice, some places have Tail Light Cameras (CCTV)
• I'm not sure that there's any specific rule about it, but most signalmen never send Train Out until they've put the Home Signal back.  It's certainly considered a good habit to get into, as it protects the rear of the train in the platform if a second train is accepted without thinking.   
• The block is not supposed to be turned back to Normal until the box in rear acknowledges the 2-1 signal, though in practice the acknowledgment is immediate since he will already be standing by the instrument because he's only just acknowledged the Call Attention code sent for it.

Edited December 6, 2021 by Michael Hodgson

[Lacathedrale]

Limit of Shunt - makes sense. Since we have the up main, there's no need for the shunter to use the down main.

Re: slotting - so the red distant is released by the red home signal, but also slotted with the blue starter signal?

Re: setting the home back to danger - for our purposes then, this means that the train should be past the signal box and essentially in a platform road before the home is re-set.

Updated the list of tasks to swap the train out and home signal re-setting, and adding the acknowledgement of Train Out by Blue.

 

Does 'Train on Line' lock any signals for either box?

If 'Normal' locks the Blue starter and Red home/distants, what's to stop the Blue starter from already being in the wrong position?

[Jeremy Cumberland]

5 hours ago, Lacathedrale said:

Blue (FY) sending a train to the station:

1. Blue starter and Red home/distant signals are locked at danger by default
2. Blue sends the relevant call to attention and train bell code, which are acknowledged by repeating by Red
3. Red sets 'line clear' which unlocks the red home and distant signals, and the blue signal box may pull off its starter signal.
4. Blue signalbox sends a 'train entering section' bell code, which is acknowledged by repetition, and re-sets their starter to danger after the loco is clear
5. Red signalbox sets 'train on line', and when it passes he re-sets his home/distant to danger
6. As train fully passes the red signalbox, he sends 'train out of section' bell code to blue, sets the commutator to 'normal' which locks the signals and can start again.

 

Would late nineteenth century practice have had such interlocking between block instruments and signals? The starter may well have a line clear release (in step 3, Red sets line clear which allows Blue to pull off his starter signal), but that would be all, surely?

 

Red can pull off his home signal at any time the route is set so far as the interlocking is concerned, and he can pull off the distant as well, if the home is clear, although the distant won't show clear because of the slotting, not till Blue clears his starter.

 

Red won't set his home to danger till the train has passed over the points (or he shouldn't do, at any rate - I expect this was in the rule book, at least in respect of facing points), and there is no reason for him to set the distant to danger till he is ready to set the home to danger. He will (or ought to, and it is difficult to imagine why he might not) set the home to danger before sending out of section and setting the instrument back to normal, but there is no interlocking to enforce this.

[bécasse]

The only shunt signals that you need are those protecting the exit from sidings on to a running line and these were required by law. Otherwise the LNWR was extremely parsimonious in the provision of shunt signals relying instead on hand signals from the signalman to the driver. This gradually changed in the early years of the 20th century but even then non-legal shunt signals were usually only provided where sighting between signal box and driver was difficult. Cyril got it largely right except that signal 4 would have been a ground signal, not a ringed arm on a post, and signal 5 would not have existed, moves being authorised by hand signal. The ground signals that you require at the exits from the two sidings would have been the pre-1915 rotating-head types, kits for which are sold by Wizard Models - GS004/1: LNWR Rotating Head Ground Signal Kit (pack of 2).

 

One other thing to remember if you are including distant signals is that they would have been fishtailed but painted red, not yellow, in LNWR days.

 

 

Edited December 6, 2021 by bécasse

[Michael Hodgson]

25 minutes ago, Lacathedrale said:

 

Re: setting the home back to danger - for our purposes then, this means that the train should be past the signal box and essentially in a platform road before the home is re-set.

Updated the list of tasks to swap the train out and home signal re-setting, and adding the acknowledgement of Train Out by Blue.

 

Does 'Train on Line' lock any signals for either box?

If 'Normal' locks the Blue starter and Red home/distants, what's to stop the Blue starter from already being in the wrong position?

 

25 minutes ago, Lacathedrale said:

 

Re: slotting - so the red distant is released by the red home signal, but also slotted with the blue starter signal?

 

 

"Released by" is a technical term meaning you can't pull a lever until ...

"Slotted" means that although the lever in one box may be pulled, the signal won't move until the associated lever in the other box is also pulled.  Either lever can be the first one pulled.  The signal arm is connected to a weighted arm resting loosely via a T-piece on top of and between two more arms with counterweights on them 0n the same spindle.  Pull the lever in one box, ones of the arms drops.  The signal doesn't move because the  T piece is still resting on the other.  once the second lever is pulled and its arm also drops, the weight on the middle arm drops with the T piece - easier to see in this diagram I found online

 

 

25 minutes ago, Lacathedrale said:

Does 'Train on Line' lock any signals for either box?

If 'Normal' locks the Blue starter and Red home/distants, what's to stop the Blue starter from already being in the wrong position?

There is a subtle difference in terminology,  Train on line does not lock any signals, rather Line Clear releases them. 

 

The rules are there to prevent the starter being off when the block isn't at Line Clear.  The signalman should have put the lever back after the last train passed it.  He is supposed to very that the arm also went back - either by looking out of the window, or at an electrical repeater it it's out of sight.  If he forgets or doesn't bother, the signal will still be off.  Even if he remembers to send Train entering section, the block will be changed to train on line, but the signal will remain off until either he replaces the lever or in some cases a mechanism may restore it automatically when the track in advance of the signal becomes occupied.  This usually happens automatically for colour lights, but relatively few semaphores were fitted with automatic restorers. 

 

The rules require that the signalman restore signals to danger as soon as the whole train has passed, subject to the proviso about it also having to pass pointwork where applicable.  It becomes instinctive to clear up signals as a train passes - in practice an experienced signalman would do this without thinking about it and if he was caught out by finding the block in the wrong position or a lever locked when he wasn't expecting it, he would suddenly stop in his tracks asking himself what he's done wrong.  His faith in the system is such that he trusts the equipment and has to convince himself it's not down to (his own) human error when equipment doesn't behave as he expects. 

 

 

 

7 minutes ago, Jeremy C said:

Would late nineteenth century practice have had such interlocking between block instruments and signals? The starter may well have a line clear release (in step 3, Red sets line clear which allows Blue to pull off his starter signal), but that would be all, surely?

 

Red can pull off his home signal at any time the route is set so far as the interlocking is concerned, and he can pull off the distant as well, if the home is clear, although the distant won't show clear because of the slotting, not till Blue clears his starter.

 

Red won't set his home to danger till the train has passed over the points (or he shouldn't do, at any rate - I expect this was in the rule book, at least in respect of facing points), and there is no reason for him to set the distant to danger till he is ready to set the home to danger. He will (or ought to, and it is difficult to imagine why he might not) set the home to danger before sending out of section and setting the instrument back to normal, but there is no interlocking to enforce this.

No, in the nineteenth century more reliance was placed on signalmen following rules.  The "controls" such as line clear release came in later, and minor lines were slow to get them - they continued to have what was called "free block", which meant safety was more reliant on strict adherence to procedures.

 

The rule requiring signals to be put back promptly was No 68 (in the 1950 BR book - though rule numbers changed in certain other editions).  That includes putting the Distant back to Caution (not called "Danger", since the mid 1920s when the arms and levers were painted yellow) as soon as he can see the whole train has passed it.  In practice he might not be able see it until the train is closely approaching.  However previous box's starter should already have been put back when the train past him, so where the distant is slotted the arm will have gone back on and the box in advance is usually just restoring his lever to correspond with it.

[Lacathedrale]

Thank you Michael - the simple logic of the block indicators (as opposed to releasing levers) makes sense fairly directly to me. I have edited the order of actions in the original point

 

becasse - parsimonous or no, I think I would like to include the relevant shunt signals as per Buckingham they can also be used as section and controller swtches? Obviously I'm not at that stage yet though...

[Siberian Snooper]

I would put the box on the other side, as this gives the bobby a better view of the approach lines.

 

 

[Lacathedrale]

@Siberian Snooper - not a bad shout, not least because then you could see into the box instead of it being a plain wall!

[Lacathedrale]

I have put together a notional signalling plan for the layout, it seems to make sense to me - can I ask for a sanity check from those in the know?

 

 

1-4 - Platform Starters

5-8 - Platform Shunt signals

9 - Ground signal for Loco pocket

10 - Advanced Starter

 

11-15 Throat points (with 11 and 14 controlling crossovers)

16 - Trap for Loco pocket

 

21 - Shunt signal for moves from down main to platforms/pocket

18-20 - Calling on signals

22-24 - Platform homes

25 - Distant

 

A few notes:

• Platform shunt signals are a signature of the prototype I'm modelling, despite the extravagance
• P4 is departure only, so it does not factor on the home gantry
• I am deliberately avoiding the inclusion of facing point locks for simplicity's sake - but if I were to include them, it looks like only half of crossover 11, and turnouts 12 and 13 would require them?
• The distant on the up main is non-functional, the double-track leading directly to a fiddle yard with no further block sections.

If this is OK, I will start drafting a locking table.

 

Edited December 15, 2021 by Lacathedrale

[Lacathedrale]

As I look at it, I wonder if 25 should be an outer home instead of a distant? or a section signal for the proceeding box with a slotted distant?

[Jeremy Cumberland]

16 would be worked off 15, as you seem to have realised by 16 being spare.

 

For FPLs, you've missed the down side of 14. [Edit: Sorry, I meant the up side. I see from your note to 21 that down is away from your station].

 

I wouldn't have thought 25 would want to be an outer home since you are unlikely to want to use the down line for shunting. If the next box is close enough to use the same post for its starter, this may affect what you do with 10.

 

Does the existance of all those platform shunt signals on your prototype indicate that the next box is indeed only a short distance away, the platform starters are the section signals, and your 10 is in fact the next box's home signal?

Edited December 15, 2021 by Jeremy C

[Lacathedrale]

Yes that's right - the next signalbox on the prototype is very close - about two hundred yards if I remember rightly! 

 

 

I've coloured and lettered the track to aid in block switching but that's not all that relevant for this discussion except to highlight the following:

 

W - within block for this box

V - within block for adjacent box

 

25 - Distant signal for this box

 

97 - Distant signal for adjacent box (essentially fixed)

98 - Home signal for adjacent box (controlling access to FY)

99 - Starter signal for adjacent box (controlling access from FY)

 

I tried to write up a locking table but I feel just all kinds of stupid whenever I try, so I think I'm going to eschew physical interlocking on the related layout for now...

 

Edited December 15, 2021 by Lacathedrale

[5BarVT]

12 hours ago, Lacathedrale said:

I tried to write up a locking table but I feel just all kinds of stupid whenever I try, so I think I'm going to eschew physical interlocking on the related layout for now...

That may be because you’re trying to put too much on!

In real life, there would be locking between quite a few of the points e.g. 14 locks 15N and vv, but you don’t need that for a model.  So the only point to point locking I would put on is between 11 and 12.

Obviously, each signal locks the points necessary for its route (and the converses).

You don’t need to lock signals against other signals that require a different point setting (this saves a lot of locking), so there is no locking between the entrance signals and the exit signals as they want 14 different ways.

Thus the only signal to signal locking is Main/call-on (same platform) coming in, Main/shunt going out, and both main and shunt against 21.

21 is the horrible one (!) as it has conditional locking.  It could be simplified significantly by making 21 a triple disc (3 levers) reading to (using track id)  cd; ab; loco.  That gets rid of any conditional locking as each pair (cd, ab) has nothing to lock beyond the split and the split points are just locked ‘both ways’.

Paul.

Edited December 16, 2021 by 5BarVT
Mistakes that shouldn’t have been made.

[Lacathedrale]

Paul, I think I just fundamentally don't understand how are drawing your conclusions I've read alot of books about interlocking but it just doesn't seem to settle. I have tried about four times now to write this down and it just gets me more and more in circles.

 

Surely 12 would be released by 11, rather than locking it normally? Or have I got my terms mixed up - I assume 'normal' is the black route on the diagram. Assuming that is the case, then I figure the signal interlocking is as follows:

 

1 is released by 11 and locks 5, 9, 14, 15

2 locks 6, 9, 14, 15

3 is released by 13, 14, and locks 7, 9, 12

4 is released by 14 and locks 8, 9, 12, 13

Shunt signals as above

 

22 is released by 11, 12 and locks 14

23 is released by 13, and locks 12, 14

24 locks 12, 13, 14

Calling on signals as above

 

[5BarVT]

11 hours ago, Lacathedrale said:

Surely 12 would be released by 11, rather than locking it normally? Or have I got my terms mixed up - I assume 'normal' is the black route on the diagram.

Mea culpa, no you haven’t got your terms mixed up, I had it in my head that 11 lay the opposite way.  It’s slightly unusual for a crossover to lie like that, but not unknown.  I would probably have made 12 the crossover and 11 the single end, but I’ll work with how you’ve shown it for continuity.

14 hours ago, Lacathedrale said:

 

I’ve also noticed that I need to add point to point locking between 14 and 15 to prove the trapping protection for the loco spur when a passenger train departs.

 

14 locks 15, 15 locks 14.
 

This is your locking from above, bold is added, underlined is removed.  Don’t underestimate yourself, it is a good first attempt.

 

1 is released by 11 and locks 5, 9, 14, 15, 21

2 locks 6, 9, 11, 14, 15, 21

3 is released by 13, 14, and locks 7, 9, 12, 21

4 is released by 14 and locks 8, 9, 12, 13, 21

Shunt signals as above (swapping 1 for 5, 2 for 6 etc)

if I add signal 9:

9 is released by 15, locks 21

From that you will see that 1 and 2 lock 15 but 9 is released by 15 so the lock is already there indirectly.  Likewise, 9 doesn’t lock 14 as that is already there indirectly because 15 locks 14.

 

22 is released by 11, 12 and locks 14 

(If you don’t have the point to point locking 12 released by 11 then yes.  However, if 12 is released by 11 then 12R proves 11R so 22 only needs to be released by 12.  This is the sort of stuff that causes brain ache in big frames!)

23 is released by 13, and locks 12, 14

24 locks 12, 13, 14

Calling on signals as above

I’ll now add 21 . . .

21 locks 14bw, (15bw w. 14N), (11bw w. 14N and 15N), (11N,12N, 13bw, w.14R)

11N w.14R is something I would apply in real life, but could be omitted on a model.

 

Told you 21 would be horrible! :-)

 

Paul.

[bécasse]

Given that this is an LNWR layout, the two ends of 11 and 12 should all be separately worked points. The LNWR frequently worked the points at either end of even a simple crossover separately and I don't think that there can be any doubt that that is what they would have done here.

[Lacathedrale]

Hi Becasse, I'm sorry - the prototype has changed to ex-LCDR SE&CR, hence the comment about ringed shunt signals - sorry!

[The Stationmaster]

15 hours ago, Lacathedrale said:

Yes that's right - the next signalbox on the prototype is very close - about two hundred yards if I remember rightly! 

 

 

I've coloured and lettered the track to aid in block switching but that's not all that relevant for this discussion except to highlight the following:

 

W - within block for this box

V - within block for adjacent box

 

25 - Distant signal for this box

 

97 - Distant signal for adjacent box (essentially fixed)

98 - Home signal for adjacent box (controlling access to FY)

99 - Starter signal for adjacent box (controlling access from FY)

 

I tried to write up a locking table but I feel just all kinds of stupid whenever I try, so I think I'm going to eschew physical interlocking on the related layout for now...

 

You seem to be a bit confused about the blocks (by which I assume you mean block sections?).  W is not a block (section) as it is within Station Limits for this 'box.  

Block (section) V is controlled by this box - i.e. the box works the block instrument which controls that block but access to the block is protected by a signal (99) worked from the adjacent 'box  

Similarly block (section) Y is controlled by the adjacent box  and what was originally signal No.10 at this bopx protects the entrance to that block section.

 

By making signal 10 a signal worked from the other box you have created considerable complexity in the working because the block section would effectively commence at the platform starting signals as they are the only signals which protect the entrance to that section.  Thus a massive amount of shunting is going to have to take place in the section.  Even if the section is short it makes much more operational sense for what was its signal 10 to remain worked by this box.  a compromise in the model world would be to make signal 10 slotted by the adjacent box which then makes the block section no motre than the thickness of the signal post but saves a lot of block signalling work for shunting movements - thus your original assumption No.1 was the correct one

Edited December 16, 2021 by The Stationmaster

[Lacathedrale]

@Stationmaster I particularly wanted to permit shunting on the down main, so I should revert 98 to an Advanced Starter on lever 10? I want to ensure that V is under control of the next box, and W is under the control of this box.

 

The coloured sections and letters are DC blocks, rather than signal blocks - no correlation to interlocking at all except for my own reference (i.e. pulling signal 1 energises DC sections E,R,T,W)  - sorry for the confusion!

 

1 hour ago, 5BarVT said:

From that you will see that 1 and 2 lock 15 but 9 is released by 15 so the lock is already there indirectly.  Likewise, 9 doesn’t lock 14 as that is already there indirectly because 15 locks 14.

 

Paul, this line here is just wonderful. I wish I had the ability to juggle the indirect locking!

 

1 hour ago, 5BarVT said:

21 locks 14bw, (15bw w. 14N), (11bw w. 14N and 15N), (11N,12N, 13bw, w.14R)

 

Can I confirm that 21 Locks:

• 14 Both ways, and
• with 14N, locks 15 Both ways, and
• with 14N and 15N, locks 11 Both ways, and
• with 14R, locks 11N, 12N and 13 Both ways

Edited December 16, 2021 by Lacathedrale

[Nick C]

1 hour ago, The Stationmaster said:

By making signal 10 a signal worked from the other box you have created considerable complexity in the working because the block section would effectively commence at the platform starting signals as they are the only signals which protect the entrance to that section.  Thus a massive amount of shunting is going to have to take place in the section.  Even if the section is short it makes much more operational sense for what was its signal 10 to remain worked by this box.  a compromise in the model world would be to make signal 10 slotted by the adjacent box which then makes the block section no motre than the thickness of the signal post but saves a lot of block signalling work for shunting movements - thus your original assumption No.1 was the correct one

Wouldn't the signal marked '99' be slotted by this box as well, as an outer home? Otherwise you wouldn't be able to accept a train without having the route already set through to the platform, potentially locking up the entire throat as soon as the incoming train enters the previous section.

[5BarVT]

8 hours ago, Nick C said:

Wouldn't the signal marked '99' be slotted by this box as well, as an outer home? Otherwise you wouldn't be able to accept a train without having the route already set through to the platform, potentially locking up the entire throat as soon as the incoming train enters the previous section.

Yes, but with the section as short as it is, is that going to be a big problem?

Paul.

[5BarVT]

Deleted ‘cos I messed up the quote!

Edited December 16, 2021 by 5BarVT
Deleted ‘cos I messed up the quote.

[5BarVT]

9 hours ago, Lacathedrale said:

 

Can I confirm that 21 Locks:

• 14 Both ways, and
• with 14N, locks 15 Both ways, and
• with 14N and 15N, locks 11 Both ways, and
• with 14R, locks 11N, 12N and 13 Both ways

You can and it does!

Paul.

[5BarVT]

9 hours ago, Lacathedrale said:

Paul, this line here is just wonderful. I wish I had the ability to juggle the indirect locking!

Thank you.

I have had a number of years to practice and I can still get it wrong.

:-)

Paul.