Signal Box Diagrams

[sem34090]

Morning all!

 

When planning out signalling for a layout, I have a tendency to draw it out like this:

I find it quite enjoyable drawing these up. Now, these ones are for a club layout (which has yet to be signalled) and I've yet to draw up a proper one for my own layout.

 

Basically my two questions are:

 

1. Have I made any serious errors with the drawing? As in, are there any conventions for such diagrams that I have missed or simply misinterpreted?
2. Have I made any serious technical errors? Be it incorrect use of Track Circuits, misplacement of Distant Signals, or anything to similar effect.

 

As will probably be obvious, the two boxes shown would be controlling opposite ends of the same station. The track has already been laid on this layout, so that cannot be changed.

[dpgibbons]

I don't know how the SR did it, but latter-day GWR signalling policy required splitting distants (eg 10,12) only if the diverging route (ie the loop) had a speed limit in excess of 40mph.

[iands]

Would there be a need to provide distant arms on the platform starting signals, e.g. 1, 4, 6 and 18?

[meil]

The only distant signal required is 12 in the lower diagram.

 

If the section is short then possibly 1 in the top diagram but this would relate to the section in advance and would be slotted.

[bécasse]

You seem to be able to route down trains into the up loop without any provision within the up loop for preventing them going any further. It would be a very unlikely provision during most of the semaphore era anyway - the most likely arrangement would be to have no facing crossover at the approach in the down direction and then a long trailing crossover on the up side so down terminating trains would offload in the down loop, continue empty in the down direction and then reverse back over the long trailing crossover into the up loop. There would probably have been a layover siding (with a run round loop for loco hauled trains) if terminating trains normally spent any great time before returning.

[St. Simon]

Hi,

 

Here is a copy of the now withdrawn standard on Signal Box Diagrams, Panels and VDUs

 

GKGN0525 Iss 1.pdf

 

It is available on the RSSB Website.

 

Simon

[beast66606]

3 hours ago, iands said:

Would there be a need to provide distant arms on the platform starting signals, e.g. 1, 4, 6 and 18?

 

No but there is a requirement for distant arms under the main line route of signals 3/16/20 and 9/11

 

The splitting distants at both ends should be replaced by a single distant arm.

 

Some numbers are missing - South Up Loop

 

If a shunt is permitted at South to run wrong line along the down then a limit of shunt is required outside the home.

 

The points next to the up yard need traps.

 

North box would probably have been an early casualty.

[sem34090]

8 hours ago, dpgibbons said:

I don't know how the SR did it, but latter-day GWR signalling policy required splitting distants (eg 10,12) only if the diverging route (ie the loop) had a speed limit in excess of 40mph.

I had wondered about this - The splitting distants only went in because someone suggested to me they ought to be there! I wasn't convinced, personally!

4 hours ago, iands said:

Would there be a need to provide distant arms on the platform starting signals, e.g. 1, 4, 6 and 18?

I had wondered this too.

4 hours ago, meil said:

The only distant signal required is 12 in the lower diagram.

Right...

4 hours ago, meil said:

If the section is short then possibly 1 in the top diagram but this would relate to the section in advance and would be slotted.

Noted.

3 hours ago, bécasse said:

You seem to be able to route down trains into the up loop without any provision within the up loop for preventing them going any further.

My bad - Need a stop board at the end then.

3 hours ago, bécasse said:

It would be a very unlikely provision during most of the semaphore era anyway

The layout is completely fluid in era (it actually serves as the club's test track) and this movement actually happens quite a lot.

3 hours ago, bécasse said:

- the most likely arrangement would be to have no facing crossover at the approach in the down direction and then a long trailing crossover on the up side so down terminating trains would offload in the down loop, continue empty in the down direction and then reverse back over the long trailing crossover into the up loop. There would probably have been a layover siding (with a run round loop for loco hauled trains) if terminating trains normally spent any great time before returning.

That does sound most likely, but the track layout cannot be altered - for one thing it's not my layout!

1 hour ago, St. Simon said:

Hi,

 

Here is a copy of the now withdrawn standard on Signal Box Diagrams, Panels and VDUs

 

GKGN0525 Iss 1.pdf 1.42 MB · 6 downloads

 

It is available on the RSSB Website.

 

Simon

I've a printed copy of this somewhere, but I can't remember where so thank you!

1 hour ago, beast66606 said:

 

No but there is a requirement for distant arms under the main line route of signals 3/16/20 and 9/11

So... 

1 hour ago, beast66606 said:

The splitting distants at both ends should be replaced by a single distant arm.

I already thought this.

1 hour ago, beast66606 said:

Some numbers are missing - South Up Loop

I'll have a look.

1 hour ago, beast66606 said:

If a shunt is permitted at South to run wrong line along the down then a limit of shunt is required outside the home.

Yes, there does!

1 hour ago, beast66606 said:

The points next to the up yard need traps.

Again they do.

1 hour ago, beast66606 said:

North box would probably have been an early casualty.

And yes, it would. I was working off of the supposed length of the rodding runs - the platform can take at least 12 MK1s.

[sem34090]

Here are the revised diagrams, based on how I've interpreted the above!

And after the abolition of 'North 'box -

 

[Grovenor]

Distant 10 should be slotted, same as 1.

What is the Up Yard used for?

Edited August 22, 2019 by Grovenor

[sem34090]

The up yard is used for pretty well anything. Sometimes for goods use, other times for stabling. As it's a test track (this layout) it has no set purpose.

 

I'll add the second slot later, though in actuality such things will end up mattering little as it will be a single frame for the whole lot. From a prototypical accuracy standpoint, however, I will do it.

[clachnaharry]

I don't see the need for calling on arm 21. Calling on arm 22 makes sense for signalling trains down trains into the up loop to access the yard.  Signal 20, however, has no function whatsoever as far as I can see.

 

What is elevated disc 6 for?

[sem34090]

No.21 is primarily for EMU operations, allowing sets to be joined in the platform (I'm recalling Barnham and, latterly, Horsham here - The latter being an example of two portions joining after traversing the same route.) It's also to permit a locomotive not already stored in the Down Siding to be brought onto the rear of a loco-hauled train already in the platform to take it out the other way (there isn't really an option to run round without using the main line, which I'm told is unadvisable). No.22 is actually serving the same purpose for the Up Loop, No.20 obviously being used when the loop is unoccupied.

 

No.6 is to allow a movement from the Up Loop onto the Down Line in order to allow a unit (probably not a loco hauled train, though it could be) to reverse into the Down Loop and thus (if the train had previously been travelling in the up direction from Bogham Road) return from whence it came.

 

I think, anyway - These explanations might not be valid.

 

 

[iands]

34 minutes ago, Grovenor said:

Distant 10 should be slotted, same as 1.

What is the Up Yard used for?

Would Distant 10 need to be slotted? Isn't this Elmchester North's Distant for No. 9 Home signal? If Elmchester South had a Distant (for Elmchester South No. 5 Home signal) wouldn't it be located under the arm of Elmchester North's No.9 signal?

[sem34090]

Yes, that's what I originally thought! I suppose a distant under EN9 might make sense. I'll see what the general consensus is!

Edited August 22, 2019 by sem34090

[Flying Pig]

1 hour ago, iands said:

Would Distant 10 need to be slotted? Isn't this Elmchester North's Distant for No. 9 Home signal? If Elmchester South had a Distant (for Elmchester South No. 5 Home signal) wouldn't it be located under the arm of Elmchester North's No.9 signal?

 

North's distant 10 would be slotted to act also as an outer up distant for South.  South's inner distant should be slotted under North's up main home 9, as indicated by beast66606 above, but there is insufficient braking distance from this signal to South's home, hence the need for an additional distant signal.

 

The same applies in the down direction: North's down inner distant should be slotted under South's down main home 3, again as beast66606 indicated.

 

The distant arms will be clear only when the corresponding stop arms at both boxes are clear to allow a non-stop run through.  They are not required for trains taking diverging routes as these will always be controlled by holding the relevant home signal at danger and will never run through under clear signals.

 

It's much simpler once North is abolished as the whole station becomes "station limits" and only the outer distants are required.

[sem34090]

I will amend the 'old' diagrams, but given the real thing will be one frame I think it's best to stick with the 'new' diagram.

[RailWest]

On the North box 8/9 seem a long way away from poitns 5 without any form of route holding.

 

On the South box 9 seems to work 3 FPLs, one on the Down line and two on the Up line. That's going to screw you up nicely when you need 9 'in' for movement on the Down line, but 9 'out' at the same time for shunt moves on the Up !

[beast66606]

signalling by committee

 

Good luck - I'm out.

[sem34090]

39 minutes ago, RailWest said:

On the North box 8/9 seem a long way away from poitns 5 without any form of route holding.

That's because of the tunnel. The points are almost in the tunnel mouth in reality, so there is barely room for a signal post, even if sighting wasn't a problem (you could have repeaters for that). The diagram doesn't make that clear, not helped because of where I sited the North 'box!

39 minutes ago, RailWest said:

On the South box 9 seems to work 3 FPLs, one on the Down line and two on the Up line. That's going to screw you up nicely when you need 9 'in' for movement on the Down line, but 9 'out' at the same time for shunt moves on the Up !

I hadn't thought of that - I shall amend it. The way I saw it was that the only movement with those points in the reverse position would be for trains going to/from the down line to/from the up loop. It's the only signalled movement. Therefore I had it that either all those points had to be reversed, with 9 out, or they all had to be normal (also with 9 out).

[Nick C]

On 22/08/2019 at 19:58, RailWest said:

On the South box 9 seems to work 3 FPLs, one on the Down line and two on the Up line. That's going to screw you up nicely when you need 9 'in' for movement on the Down line, but 9 'out' at the same time for shunt moves on the Up !

 

Plus in prototype practice, unless the frame was relocked after the track circuits were put in, you'd not have a single lever operating three FPLs (and thus three fouling bars), unless you had a seriously strong signalman!

 

You've got 28 as up yard GF release, but then 26 operating both ends of the crossover in the up yard. I'd expect 26 to operate the catch point, 27 to be a conventional red shunt on the long crossover, and all the points in the yard to be handpoints - you don't need the box controlled crossover as you've got the catch point to protect the up loop. The box diagram would then probably not include all the details of the yard as well.

 

You've also got an FPL on the leftmost end of the crossover 7/8, but no signalled facing moves over it?

[RailWest]

>>>Plus in prototype practice, unless the frame was relocked after the track circuits were put in, you'd not have a single lever operating three FPLs (and thus three fouling bars), unless you had a seriously strong signalman...

 

Fortunately they were strong men in North Devon, as there were two 'triples' at Ilfracombe - 16 and 18 :-)

[sem34090]

Ouch...

 

And I thought that 16, 17 and 18 (16 and 18 Being the FPLs with fouling bars - Each lever working only one FPL. 17 works both points.) at Medstead are tough...

 

Mind you, I think that's more to do with the wear on the frame and the change in gradient along the rodding runs.

[Compound2632]

On 22/08/2019 at 03:55, sem34090 said:

The track has already been laid on this layout, so that cannot be changed.

 

The moral of this, as of many similar threads, is: work out the signalling before you lay the track. 

 

I appreciate that it may be difficult to convince club members of this but one does have to ask, is the purpose of the layout to replicate prototype practice or simply to provide members with a test track? 

[sem34090]

Primarily the latter, really. Certainly it seems like they were envisaging it as a test track, but one that looks nice if people come to visit or we have an open day. The plan was, and I expect still is, to use automatic Train Tech colour lights throughout, but I'm hoping that by having a reasonable plan in place and being willing to build the signals I can convince them to allow some controlled semaphores, given the purpose is ostensibly to train club members in the operation of layouts (subtle differences between that and prototype practice) and some layouts have controlled semaphores!