Ground signals and single track lines

nigelcliffe
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Ground signals and single track lines

Postby nigelcliffe » Sat Jan 03, 2015 8:46 pm

I've a signalling problem, and I've not been able to solve it, so does anyone know enough about prototype to be able to help ?

The local group's layout, Coldfair Green, was signalled by someone ages ago. Nobody can actually remember why some of the signals are there, though its clear that its probably over-signalled for an LNER or early BR obscure Suffolk branch line.

The diagram shows the current signalling. The semaphores are OK (I think), though they only control up traffic leaving the station. There is a signal on the platform road (H) and one on the goods yard line (Y). The goods line also has a shunt arm below the main arm, to permit working to the sidings further along the line (though the operation of the railway seems to often depart a train from the platform road to the sidings). And there is a signal after the sidings (Z) protecting the level crossing (X).
So far so, good (though perhaps the shunt signal isn't correct?).

Then the ground signals (rotating disc) are labelled A, B, C, D. Signals A and B are for down movements, and B is has a yellow ring to the red disc. Signals C, D control up movements. In running the line, A, B and C are passed by locomotives which may take either route at the turnout ahead. Only D has a trap point ahead of it, so there is only one route.

coldfair sigs.jpg
Coldfair Green current signalling



So, can anyone come up with a plausible explanation of the ground signals and their correct use ? I think I can explain B and D, but struggle with A and C.

Operationally, we do sometimes have two locomotives in the station. A train may be in the platform road whilst another arrives to either the loop or the goods yard. Or a locomotive might be in the loop or goods yard whilst a train arrives at the platform.
So, with that, can anyone suggest how we might rationalise the signalling.


- Nigel

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Noel
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Re: Ground signals and single track lines

Postby Noel » Sat Jan 03, 2015 9:38 pm

You do not say where the box is; I assume it is just the station side of the crossing, so that exit from the sidings can be controlled by hand or flag signals from the box? Notionally, there would be a home on the other side of the crossing for incoming trains. I am assuming that this is a bracket signal, which can be cleared for trains to enter the platform road or the loop or the goods yard, in view of your comments [although a single arm admitting trains to the platform road only is probably more likely]. As well as protecting the crossing, Z is presumably also the advanced starter, which all shunting must stay the station side of?

Ground disc B probably reads loop to platform road [I have not come across yellow rings before, but assume that this is a 'conditional' signal, i.e. you can pass it at danger to enter the spur straight ahead].
Ground disc C reads platform line to loop, assuming that only stock in the platform line is run round [but then B is probably unnecessary]. Or it might read to either road if it can be 'selected' whichever way the points are set. Otherwise there should probably be two discs. Similarly A would read to either road, for shunting movements.

The answers for others will depend on whether or not departures are possible directly from the yard or loop and whether shunting occurs over the crossing, I think.

Noel.
Regards
Noel

nigelcliffe
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Re: Ground signals and single track lines

Postby nigelcliffe » Sat Jan 03, 2015 10:08 pm

Thanks Noel.

Signal Box is at end of Platform, closer to Yard than Signal H, close enough to hand signal movements out of yard.

Yes, there would be an imaginary (off scene) home signal protecting the crossing for down traffic. I agree that reality was probably single arm for platform road. I need to check whether all of the timetable moves which bring a locomotive plus freight wagons directly to the yard roads are a locomotive plus stock (including brake van) returning from the sidings adjacent to Z (and thus a shunting move, rather than a train arriving).

Yes, treat Z as an advance starter, and all shunting is station side of that signal.

I read Ground B as you do. Treat the yellow as permission to pass (though with caution given the proximity of the buffers!).

Locos sitting ahead of Ground C will proceed along either route (Platform or Loop). Most working is to the Loop, but some operations are to the Platform. So, if it is a single disc, an interpretation is "proceed, no information on route". If this interpretation is correct, then presumably Ground A should be treated similarly, and set to "proceed" when a train arrives in either the platform or loop road ?
( And if the above paragraph is correct, then many of my questions may have been solved).

Departures do not happen from the loop - trains may be shunted from the loop to the platform road prior to departure.
Shunting is not done over the level crossing.

(Oh, and if relevant, the sidings adjacent to advanced starter Z have a ground frame which is released by a key brought from the signal box).



Thanks again for the reply

- Nigel

Chris Mitton
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Re: Ground signals and single track lines

Postby Chris Mitton » Sat Jan 03, 2015 10:10 pm

nigelcliffe wrote:I've a signalling problem, and I've not been able to solve it, so does anyone know enough about prototype to be able to help ?


Hi Nigel - I'm not a signal engineer but I do have some knowledge of Great Eastern practice (I assume Coldfair Green is GER - it certainly was last time I saw it) - doubtless the engineers on this forum will shoot me down but here goes.....I've got diagrams for several GER stations (Mildenhall, Saffron Walden, Framlingham, etc) and my own embryonic layout, Stowe Fen, is loosely based on Framlingham.

Firstly, I'm puzzled why there are only up semaphores. If there is ever a loco / train already in the station, there would need to be at least one down home to prevent an incoming train colliding with it. I would suggest a home on the far side of the level crossing (killing two birds with one stone), and maybe an inner home just before the loop entry (somewhere near ground signal A, possibly with A on the same post).

Secondly, the yellow signal - my understanding is that a GD with a yellow stripe / face instead of a red one indicated that it could be passed at danger provided the route set was not the one it authorised. This stems from an apparent general principle that no shunt signals were provided except to authorise a movement to or from a running line. Thus signal B would authorise a movement from loop to platform road, but could be ignored by a shunting movement into the end of the loop (loading dock or whatever it is). I can't quite see the point of this signal, unless goods trains are made up in the platform road, in which case it would let an engine shunt a wagon or two (or a brake van) onto the platform end ready to shunt onto the back of the train, under the authority of signal C. Signal C would also allow an engine release manoeuvre into the loop. Personally I would do away with both those - any movements there would be controlled by the train crew themselves or a shunter. I can't find any GER termini where there are shunt signals at the very end of the line.

Signal A would authorise a movement from the running line into the loop - in which case it would surely also be yellow so that an arriving train into the platform road could safely ignore it. I think it should be moved a bit in the up direction, ahead of the yard entry turnout, so it could also control yard entry - at present you haven't got any signal allowing entry to the yard! Alternatively, it could be two GDs, adjacent or vertically mounted on the same post. Obviously D would authorise exit from the loop, and as you observe must be red as it can only have one possible route.

The shunt signal on post Y, as you correctly observe, is a tad eccentric (so was most GER practice!) - it either needs to be echoed on post H, or, better, moved to a ground disc ahead of the entry to the sidings near Z - which I think would also be yellow so that departing trains could ignore it?

Don't forget that the three turnouts on the "main" line would all need FPLs!

Hope this (a) sounds plausible and (b) makes sense! {If I get time tomorrow and it would help, I'll draw a diagram....]

Regards
Chris

nigelcliffe
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Re: Ground signals and single track lines

Postby nigelcliffe » Sat Jan 03, 2015 11:03 pm

Thanks Chris, diagram would be helpful. We are ex GER on the line, you'll find the settlement on a map a few miles south of Leiston.

I'll think about what you've written.
A home signal for inbound trains may be useful, somewhere near the cut on the diagram (which is also a bridge, which may obscure some signals and thus dictate their placement).
Removing ground signals suits me, though I do have the rest of the team to convince. I've also got to look at the moves which don't arrive in the platform road. Some are new arrivals to the loop (platform road occupied), but I can't now remember(*) if the train which moves into the yard originates at the mill siding (adjacent to Z), and is thus may be seen as a shunting move within the station limits.

Yes, we do have facing point locks on the main line.


(* I spent much of today operating the layout in its "short" form, where the layout ends at the cut lines, so its not always apparent to an operator, or onlooker, where an incoming train originates. In its "long" form, the origin of a train is obvious. And the timetable is now in a storage crate in the workshop, so it will be tomorrow before I consider reading it again. ).


- Nigel

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grovenor-2685
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Re: Ground signals and single track lines

Postby grovenor-2685 » Sat Jan 03, 2015 11:34 pm

I agree with much of what has been said.
Release crossover, this could be worked by hand levers, most likely just a single lever ground frame rodded to both the crossover points, no need for any signals. The FPL on the points in the platform would be worked from the box and would be unlocked to allow local operation of the crossover and required locked again to release signals in or out of the platform.
Both the goods sidings at the station and the sidings near signal Z need trap points.
With signal Z acting as a limit of shunt and the sidings worked by key release frame there is no need for shunt ahead signals on H or Y as the main arm can be pulled off to allow trains up to Z for shunt moves. Clearing Z would need the token out and given to the driver.
Signal A could be moved back to the siding turnout and be cleared for all 3 routes, or there could be one at each of the point toes to reduce the distance engines running round need to go, more likely the former. It could have 3 discs, one for each route but since the crews would know where they were going one is really enough.
When the home is cleared for an arriving train, the best arrangement is for A to be pulled as well as it avoids a train passing a red and also helps with route holding as the home can be replaced as soon as passed while A keeps the points locked. However company practice varied on this and I don't know the GER practice specifically, you would need a locking table for a similar case to see.
I agree with a single arm home outside the level crossing so all trains arrive in the platform.
Regards
Keith

nigelcliffe
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Re: Ground signals and single track lines

Postby nigelcliffe » Sun Jan 04, 2015 9:48 am

Thanks for the comments,

here is another sketch, which I think covers the comments received so far.

coldfair sigs 2.jpg
revised coldfair green signalling


The changes are:
  • Remove ground signals at run-round cross-over
  • Show trap points and facing point locks (they are on the model, just absent from first diagram)
  • Show (off scene) down home signal beyond level crossing
  • Show position of signal box and ground frame (requiring locking key from signal box) at sidings
  • Remove shunt arm from signal to leave Yard (Y)
  • Show possible move of ground signal A

It would be awkward to move Ground Signal A, the new position would be under an over-bridge, so it would be restricted view and access. So that may prove impossible.
I have checked the timetabled movements, and the only move where a train arrives directly into the yard, is the return of a train which propels wagons to the sidings near Z, and then returns with other wagons collected at the sidings. This move is within the limits of the station outer home at Z.
Use of Ground Signal A should be "clear" to indicate to a train to proceed past it, into either the platform or loop. (And if it is re-sited, then proceed into any of platform, loop or yard).

Have I summarised this correctly so far ?

- Nigel

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grovenor-2685
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Re: Ground signals and single track lines

Postby grovenor-2685 » Sun Jan 04, 2015 10:44 am

Pretty much as discussed except the arrangements for the release crossover, ground frame and/or fpl, are not shown.
If the preferred position of signal A is under a bridge and out of sight, presumably for vistors/operators as it would be OK from a train crew viewpoint, then just provide an additional dummy signal at the toe of the yard points, there does need to be a signal there to shunt into the sidings, and the overbridge would prevent reliance on a green flag from the box.
Regards
Keith

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Noel
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Re: Ground signals and single track lines

Postby Noel » Sun Jan 04, 2015 11:09 am

As now drawn the release crossover is presumably operated directly from the box, which is OK. If not, it does need its own g/f as it is on a passenger line. I would suggest that it should be the main arm which is removed from the yard signal, or the whole thing replaced by a disc, either of which which would then be consistent in approach with the use of disc D at the loop exit.

Since the crossing, which I assume from its need for signal protection is a public road crossing, is so far from the box it will need a gatekeeper with suitable accommodation, since the signalman can't adequately supervise it. He or she will also need to be able to communicate with the signalman to confirm that the gates are closed, to allow the signalman to clear the home or starter, so will need his/her own railway telegraph pole like the box.

Noel
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Noel

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Will L
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Re: Ground signals and single track lines

Postby Will L » Sun Jan 04, 2015 11:21 am

If proof were ever needed that nothing is ever simple...

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grovenor-2685
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Re: Ground signals and single track lines

Postby grovenor-2685 » Sun Jan 04, 2015 12:05 pm

In my view operating the release crossover from the box without signals or track circuits is risky as the signalman will not be able to observe the clearances properly, the crossover should have a ground frame so the operator can see everything clearly when handsignalling the movement. The FPL being operated from the box keeps everything secure when arrivals and departures are signalled.
The signal, Y, out of the goods sidings could be a disc, short arm or full size arm as desired although the latter is only really likely if departures are regularly made direct from the sidings.
So far as the level crossing is concerned, I agree with Noel, its to far from the box for working by rodding so would have to be hand operated by a crossing keeper.
Keith

nigelcliffe
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Re: Ground signals and single track lines

Postby nigelcliffe » Sun Jan 04, 2015 12:34 pm

Thanks for the comments. I think I'm getting close to an understanding of correct operation.


The crossing does have its own crossing keeper's cottage, complete with telegraph communication to the box; its too far from the box to be operated directly (see various postings on Scaleforum, and photo of cottage in Finescale Review issue 2).

The run-round cross-over appears to need a facing point lock on the platform road (controlled from box) and a crew operated ground frame.

The Yard does have departures from the sidings, so full sized arm may be credible. But as any arm (full, shunt or ground signal) seems acceptable, I'll see what the rest of the Coldfair team say. Reducing from two to one arm may make things easier, though we might keep the double arm and put it as an GER oddity.

The extra ground signal to protect the yard entrance will have to be thought about, due to proximity of bridge. I take the point of the scale train crew being able to see it. But, as we do have signals which work, it would be nice to have them all working even if they are hard to see by operators and visitors.


- Nigel

John Duffy
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Re: Ground signals and single track lines

Postby John Duffy » Sun Jan 04, 2015 1:43 pm

If the platform FPL was operated from the box, then would the cross-over not also be operated from the box?

I can only really speak of the GNSR practise (whose interpretation of signalling rules was however somewhat idiosyncratic) but they operated four different methods of run-round release;
1) Operated entirely from the signal box
2) Operated independently (hand thrown levers)
3) Ground frame with electronic release from the signal box
4) Release bolt operated from the signal box, with hand thrown levers.

There also appears to be a mix of FPL fitted or not.

It seems as though there is a bit of scope for a local solution.

John

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grovenor-2685
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Re: Ground signals and single track lines

Postby grovenor-2685 » Sun Jan 04, 2015 3:14 pm


nigelcliffe
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Re: Ground signals and single track lines

Postby nigelcliffe » Sun Jan 04, 2015 3:48 pm

Thanks for that Keith, nice to know people liked the layout. We try to present things to a decent standard. Accuracy is a strange thing, with a fictional location the best that can be done is prototypically plausible.

- Nigel

Chris Mitton
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Re: Ground signals and single track lines

Postby Chris Mitton » Mon Jan 05, 2015 12:58 am

nigelcliffe wrote: Accuracy is a strange thing, with a fictional location the best that can be done is prototypically plausible. - Nigel

Hi Nigel
But that's the strength of fictional lines - you can always argue, as I do with my Stowe Fen (or will if it ever makes significant progress) that it's a 100% accurate replica of the railway that exists between your ears. Don't forget also the golden rule of bucolic GER branches - compliance with the Rule Book was inversely proportional to distance from the prying eyes of HQ.

More power to your elbow,
Regards
Chris

Terry Bendall
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Re: Ground signals and single track lines

Postby Terry Bendall » Mon Jan 05, 2015 7:17 am

grovenor-2685 wrote:Anyway you got good reviews from Marlow and Maidenhead


And nothing to do with this thread - sorry, but Coldfair Green, in an extended form, and with ground signals, will be one of the layouts at Scaleforum 2015. Just to whet your appetite, the next issue of Scalefour News will contain details of the other layouts on show and other details, as far as they are fixed at present.

Terry Bendall


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