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Modbury - Signalling Diagram (Mark II)

Posted by Ian Smith , 04 January 2015 · 1,169 views

Over the Christmas period I have been giving further thought to the signalling diagram for Modbury, and its associated Locking Chart.

I really want to get this as sensible/accurate as possible because it is my intention to use the signals to allow power to be provided/denied to the various track sections, effectively engines will only get power if the correct signal(s) have been Cleared to allow entry into the section.

To this end, I have come up with the following :
Attached Image

I still have a few items to iron out, which hopefully I can do by referring to prototypical GWR Signal Diagrams. For instance a train given "Shunt Ahead" rights in the Down (to the left) direction, would a ground disc be provided by turnout (5) to allow the train to come back into the Down platform (especially since the turnout is beyond the road over bridge)? Similarly, I have provided a ground disc (11) by turnout (12) but can't decide which side of the track it would be sited - it is there to allow access into the Goods Yard/Up Loop by trains shunting in the Down (from the right) direction.

I have also been giving consideration to the method of wiring the connections to the Signal Actuators (Memory Wire). Luckily, I have the Model Railway Constructor articles on the P4 North London Group's "Bodmin" layout, where they have described the utilisation of relays to facilitate the type of operation that I want to achieve.

To this end, I have taken their ideas and produced an example wiring diagram for a short section of track with a couple of signals which I will now develop into a full wiring diagram once all of my track work has been laid (I have provided a fews comments for myself when I come back to this in a few months) :
Attached Image

Hopefully the diagrams are large enough for interested parties to read!

I look forward to receiving further comments (critical or otherwise)

Ian
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Looks pretty good. I will have a look and see if I can find some examples of stations where they have the same sort of layout.

Don

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queensquare
Jan 05 2015 11:36
Happy New year Ian. Looks terrifying, way beyond me that stuff:-)) Jerry

Looks pretty good. I will have a look and see if I can find some examples of stations where they have the same sort of layout.

Don

Don,

Thank you.  The early layout of stations on the DN&S seems similar to my layout of having a diamond to access the goods loop and sidings, but as yet I have been unable to locate a signalling diagram for places like Highclere/Burghclere.

 

Happy New year Ian. Looks terrifying, way beyond me that stuff:-)) Jerry

Happy New Year to you too Jerry.  I have to admit that I've read and re-read the Bodmin articles so many times now I think I could recite them in my sleep!!  I'm a bit of an electrical numpty really, but I felt that it was something I needed to get to grips with if I was going to fulfil my requirement of using the signalling to operate the layout.  The really tricky bit is going to be making the lever frame and mechanical interlocking that I eventually want to employ!! :-)  (Although to an extent that is almost a future enhancement)

 

Ian

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The Stationmaster
Jan 05 2015 13:58

Ian,

 

Following what seem to have been usual GWR practice there would be no need for a disc at 5 as it is in effect 'plain line' for a shunt back through No 10 crossover (to pull 10 would require 5 reverse as would the Shunt Ahead subsidiary).

 

11 is something rather different and I'm really going to try to get to its purpose before anything else.  However if it was provided (read on) it would be co-located with the running signal (13) with both at the point toe on probably the left of the line and point 12 would havea  lock bar through teh point instead of lying in rear of the point toe.

 

But more important is the purpose of 11.  Normally the yard would be shunted by an Up train as it is a trailing move and, similarly to the other end in some respects the disc would be at the toe of 7 as it would require 12 reverse to release it - thus ensuring 12 is effectively 'plain line' for such moves and therefore doesn't need a ground signal.  However you seem to want to shunt the yard with a Down train which means running round - a signalled move - then picking up off the rear of the Down loop (could be handsignalled) then setting back off the Down Loop towards the right (therefore needs a ground signal) then reversing towards either the yard - a disc at 12 requiring both 12 & 7 reverse (and potentially - depending on period) a double disc with the other arm reading to the Up Loop requiring 12 reverse and locking 7.

 

Hope this helps rather than confuses or confounds.

 

Mike

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nick_bastable
Jan 05 2015 18:41

A neat looking workable ( is there such a word ?) solution

 

As a thought have you considered a logic ( arduino ) solution ?  if the points / signals are servo driven it will drive them via interface shields as can the track  power via a relay shield, The   advantage been it can be tested section by section and reprogrammed if it fails to respond quite how you thought

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Pannier Tank
Jan 05 2015 19:07
Very nice drawings, I wonder what package you used?

Ian,

 

Following what seem to have been usual GWR practice there would be no need for a disc at 5 as it is in effect 'plain line' for a shunt back through No 10 crossover (to pull 10 would require 5 reverse as would the Shunt Ahead subsidiary).

 

11 is something rather different and I'm really going to try to get to its purpose before anything else.  However if it was provided (read on) it would be co-located with the running signal (13) with both at the point toe on probably the left of the line and point 12 would havea  lock bar through teh point instead of lying in rear of the point toe.

 

But more important is the purpose of 11.  Normally the yard would be shunted by an Up train as it is a trailing move and, similarly to the other end in some respects the disc would be at the toe of 7 as it would require 12 reverse to release it - thus ensuring 12 is effectively 'plain line' for such moves and therefore doesn't need a ground signal.  However you seem to want to shunt the yard with a Down train which means running round - a signalled move - then picking up off the rear of the Down loop (could be handsignalled) then setting back off the Down Loop towards the right (therefore needs a ground signal) then reversing towards either the yard - a disc at 12 requiring both 12 & 7 reverse (and potentially - depending on period) a double disc with the other arm reading to the Up Loop requiring 12 reverse and locking 7.

 

Hope this helps rather than confuses or confounds.

 

Mike

Mike,

 

Thank you very much once again for your comments.  I'm trying to digest them now!!

 

What your comments have done is provide me with food for thought on how a station such as mine might have actually been operated in reality.  Reading through your comments both on this iteration and its previously less considered incarnation, what I am picking up is that it would be usual for the yard to be shunted by an UP train.  If this were the case would it be sensible to assume that any wagons destined for Modbury on DOWN trains would simply be detached and shunted over the crossover (10) and be deposited in the Goods Loop for an UP train to deal with later?  Of course in reality I presume that a horse or man power would be utilised to haul (for example) a cattle wagon dropped off in the loop by a DOWN train into the cattle dock siding.

 

 

But more important is the purpose of 11.  Normally the yard would be shunted by an Up train as it is a trailing move and, similarly to the other end in some respects the disc would be at the toe of 7 as it would require 12 reverse to release it - thus ensuring 12 is effectively 'plain line' for such moves and therefore doesn't need a ground signal.  However you seem to want to shunt the yard with a Down train which means running round - a signalled move - then picking up off the rear of the Down loop (could be handsignalled) then setting back off the Down Loop towards the right (therefore needs a ground signal) then reversing towards either the yard - a disc at 12 requiring both 12 & 7 reverse (and potentially - depending on period) a double disc with the other arm reading to the Up Loop requiring 12 reverse and locking 7.

 

 

On the assumption that the yard will only be shunted by UP trains, what I am now inferring from your comments is that my siting of Ground Disc 11 would be incorrect and should instead be moved to the toe of 7 (I had already assumed that 12 reversed would release it).  If that is the case, would 11 Cleared give access ONLY to the Goods Loop (and sidings) or would it also be used to allow the engine (and possibly wagons retrieved from the yard) back down the UP Loop to the remainder of an UP train left in the platform?  Or would I need another Ground Disc to cover that move?

 

Thank you once agin for your assistance.

 

Ian

Very nice drawings, I wonder what package you used?

 

Both the Signalling Diagram and the Wiring Diagram were both drawn with Inkscape.  Not an ideal tool for the wiring diagram as when you move something you then have to go back and re-connect any lines that were previously connected to the bit that was moved (and any "hop-overs" have to be put in manually too).

A neat looking workable ( is there such a word ?) solution

 

As a thought have you considered a logic ( arduino ) solution ?  if the points / signals are servo driven it will drive them via interface shields as can the track  power via a relay shield, The   advantage been it can be tested section by section and reprogrammed if it fails to respond quite how you thought

Nick,

I did consider servos for the points and signals but decided in the end to use memory wire.  We (well, Andy) has used servos for the signals on St Ruth and I think that the jury is still out, we have quite a few glitches that usually mean that Andy has to get under the boards to sort out at exhibitions, I don't think that I would want to use them for points for that reason (although I know others are perfectly happy with them).  Being an old-fashioned kind of guy I intend to stick with DC, and I really, really want to build a fully interlocked mechanical locking frame with proper levers rather than a whole load of fancy lights and switches (somehow it seems more in keeping with an Edwardian layout) :-)

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Pannier Tank
Jan 05 2015 20:26

Both the Signalling Diagram and the Wiring Diagram were both drawn with Inkscape.  Not an ideal tool for the wiring diagram as when you move something you then have to go back and re-connect any lines that were previously connected to the bit that was moved (and any "hop-overs" have to be put in manually too).

Thank you for your reply; you've done a nice job.

Hi Ian, I can't add anything here but just wanted to thank you and Mike for this instructive discussion, including the signalling and the UP/DOWN shunting issues.

I do think it's a wise choice to stick with mechanical point & signal control. A few years back I got seduced by the servo control idea (using MERG boards for cost saving) but found it unreliable/glitchy and have managed to rescue the situation on my latest layout by converting the servos to stall type units. I shall return to easy/simple/cheap mechanical means on any future layout.

 

Izzy

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richbrummitt
Jan 06 2015 14:07

What I understand of the final diagram appears to be more complicated than it needs to be. I also aim to achieve what you set out out to. I built the S4 lever frames and ordered the interlocking from Modratec (without the lever part of the frame). The latter is still to be built but getting my head around the sigscribe (see Modratec website) program was, for me, much easier than trying to build the most compact interlocking that I could. Once interlocked the task of providing power to only those sections that should have it was achieved more simply, and I could dispose of the three and four pole double throw switches previously linked to each switch. From memory there were enough auxiliary contacts on the turnout motors to route the power to the appropriate track. No relays required.

What I understand of the final diagram appears to be more complicated than it needs to be. I also aim to achieve what you set out out to. I built the S4 lever frames and ordered the interlocking from Modratec (without the lever part of the frame). The latter is still to be built but getting my head around the sigscribe (see Modratec website) program was, for me, much easier than trying to build the most compact interlocking that I could. Once interlocked the task of providing power to only those sections that should have it was achieved more simply, and I could dispose of the three and four pole double throw switches previously linked to each switch. From memory there were enough auxiliary contacts on the turnout motors to route the power to the appropriate track. No relays required.

Richard,

I too have recently downloaded a copy of the Sigscribe program.  I've only used it a little and am trying to get to grips with it.  What I do like is that when I have finalised my signalling I will be able to "play signalman" to test that I have got the locking right.  I didn't realise that Modratec could provide just the locking frame, I assumed that you would have to but the lever frame too - this may not be a problem as I haven't yet decided whose lever frame to use (or make my own), although I always liked the look of the S4 one and prefer it to the look of the Modratec one.

Ian

Ian I have had a look and found two layouts where the access to the yard from the down crosses over the up line. Wheatly and Dymock. Both are in the OPC book Great Western Stations volume 2 by R Clark. There are plans and signalling for both. Dymock has the added complication of the down line also being signaled for up movements. Wheatly was originally Broad Gauge and has an extra crossover from the up to the goods loop  which actually cuts across the other forming a scissors type effect.

Don

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richbrummitt
Jan 12 2015 14:11

Richard,

I too have recently downloaded a copy of the Sigscribe program.  I've only used it a little and am trying to get to grips with it.  What I do like is that when I have finalised my signalling I will be able to "play signalman" to test that I have got the locking right.  I didn't realise that Modratec could provide just the locking frame, I assumed that you would have to but the lever frame too - this may not be a problem as I haven't yet decided whose lever frame to use (or make my own), although I always liked the look of the S4 one and prefer it to the look of the Modratec one.

Ian

 

I think I've got the whole 'frame' but no levers. It did reduce the cost somewhat until it got stopped for Royal Mail to add duties and their disproportionate handling charge. Howard (Mr Modratec) was incredibly helpful and saved me a lot of work headaches. 

Ian I have had a look and found two layouts where the access to the yard from the down crosses over the up line. Wheatly and Dymock. Both are in the OPC book Great Western Stations volume 2 by R Clark. There are plans and signalling for both. Dymock has the added complication of the down line also being signaled for up movements. Wheatly was originally Broad Gauge and has an extra crossover from the up to the goods loop  which actually cuts across the other forming a scissors type effect.

Don

Don,

 

Andy of the Midland Group has leant me his (West Country) copy of "Signal Box Diagrams" published by the Signalling Record Society.  I have been looking at places like Gara Bridge and Bampton which have similar layout diagrams to my own (albeit with single slips instead of my preferred diamond).  What is nice is that some of the stations have associated locking charts, and a few even have lever leads too (the descriptions on the levers themselves which detail what levers have to be pulled before the labelled one).  I have all 4 of the Great Western Stations volumes and have found examples where the crossover to the goods loop is over a diamond so I'm happy that my original plan has some semblance of reality!

 

 

I think I've got the whole 'frame' but no levers. It did reduce the cost somewhat until it got stopped for Royal Mail to add duties and their disproportionate handling charge. Howard (Mr Modratec) was incredibly helpful and saved me a lot of work headaches. 

 

Richard,

Thanks for that.  When I come to installing a lever frame and interlocking I will probably contact Modratec.  For the time being I will have to use electrical switches on the control panel (when I get around to building it) as I don't think I will have time to do a "proper" control panel before Expo2015!

 

Ian

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richbrummitt
Jan 14 2015 14:11

The plan reminds me of Thame somewhat, which I believe is in vol 3.

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