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Modbury - Signalling Diagram

Posted by Ian Smith , in Signalling 04 December 2014 · 1,015 views

2FS GWR
Tonight I have been trying to finalise the signalling diagram for my fictional GWR through station Modbury.

Below is the diagram that I have come up with. Hopefully it is a realistic representation of what the GWR would have provided for my Edwardian modelling period of c. 1906.

All being well others who are better informed than myself will be able to provide guidance to any errors that I may have made. The main query I would have is whether the turnout on the main line at the right of the diagram would be signalled in some way for shunting movements into the goods loop and sidings?

Attached Image

Any comments welcome (I haven't assigned lever numbers yet)

Ian

(Edited 5/12/14 to replace original PNG file with a JPG version)
  • Like x 6





Hi Ian,

 

It looks like a good start to me but I'd think that your best bet is to search out locations that have comparable track layouts and operating needs (e.g. your back siding with no headshunt space) and copy from there. I'm not too familiar with how things might have differed in Edwardian times. Given your track construction, you really need to think even further back in time and then understand what would and would not have been updated. Maybe you have an opportunity for some more antiquated signalling kit to go with your baulk road track.

 

I reckon your up home is too close to your station though - if that's the only home signal in that direction then I'd have thought it should be outside the loop point and FPL with some room for error if a train doesn't quite manage to come to a halt at the signal (AKA the clearing distance). The clearing distance also applies to the down home, but I guess you can claim 'not to scale' for your diagram there.

 

Regards, Andy

One more small issue is that a diagram should show points so that it's clear what is the normal position. Your main line is mostly OK in this regard but things go a bit awry on the goods loop - for example the point that would switch trains out of the yard and onto the diamond crossing should be 'normal' so that trains are directed into the goods shed. I think there is a similar issue with the middle one of the three points at the right hand end of the plan.

 

Hand worked points don't have a 'normal' so would be drawn on the real thing with the two lines joining together rather than 'missing each other'... although if your point control mechanism on the model does have a normal you might want to depart from prototype drawing practice there.

 

Regards, Andy

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The Stationmaster
Dec 04 2014 22:55

Pretty good and no really worrying errors which is a great start.  But it does possibly need some GWification (if layout space and 'roominess' allows) plus some notes on things relevant to teh period you are modelling.

 

 

1. It might just be a matter of the way it is drawn but the Up Home should be at the toe of the points or in rear of the facing point locking bar for those points.  Equally the Down Home needs to be similarly positioned in relation to its facing point and point locking bar.

 

2. I think to make the track layout a little more realistic it might be useful to turn the diamond into a single slip thus creating a crossover between the Up & Down loop lines - so you would need an extra ground signal to go with that alteration.

 

3. Depending on the distance between the connections I would also be inclined to provide an additional stop signal to protect the trailing connection in the lower loop - the GWR tended to be rather prolific with stop signals in that respect. 

 

4. Similarly I could see a situation where a further stop signal is provided on the Up loop to protect the connection from the sidings - however here again you need to think about avoiding a forest of signals so providing this one really depends on the lengths you have to play with for your loops.  Technically the absence of this signal makes the matter of block working acceptances potentially a little bit awkward but the Up Starter could double for it in that respect

 

5. Now the interesting question of of signaling the yard connections at the right hand end.  Firstly the exit signal from the yard would have been required to be a semaphore (complete with a  ring on the arm) and not a shunting signal at that time - it being slightly different from going the other way, however there were ground shunting signals used for such connections in contemporaneous installations and the choice is yours.  More interesting is shunting back in and here you need to apply a little bit of lateral thinking to understand how it would be signalled - the shunting would be carried out by a  train travelling from left to right, i.e an Up train, therefore the connection where the loops become the single line is bound to be set for the upper (Up) loop for the train to arrive ready to shunt and while it shunts - so no need for a ground shunting signal.  However the next point, which effectively is the connection from the Upt loop to the sidings would have a ground shunting signal because it s a trailing point in the Up loop - I hope that makes sense.

Mike's response is comprehensive as usual. One thing I would query is whether there would be a shunt signal to allow the train to draw forward of the advanced starter to shunt into the back siding. The siding turnout is quite close to the end of the loop. In many case there would be more room between that turnout and the end of the loop to allow the siding to be shunted without passing the advanced starter.

 

Don

I reckon your up home is too close to your station though - if that's the only home signal in that direction then I'd have thought it should be outside the loop point and FPL with some room for error if a train doesn't quite manage to come to a halt at the signal (AKA the clearing distance). The clearing distance also applies to the down home, but I guess you can claim 'not to scale' for your diagram there.

 

Regards, Andy

Andy,

Thank you.  Positioning of Up Home is erroneous, I should have been a little more diligent on it's placing.  My excuse is that the Up Starter, Loop entry turnout and it's associated FPL are all off scene as the bridge will be the scenic break.  I will however correct my drawing when I add the lever numbering.  It is my eventual intention to provide a lever frame for the layout, and although off scene, the levers for these items will be provided as I will be using the "virtual signal" to electrify the up loop (at least as far as the Up Starter).

I also see what you mean about the diagram showing turnouts in their "Normal" position, I will also correct that.

 

 

Pretty good and no really worrying errors which is a great start.  But it does possibly need some GWification (if layout space and 'roominess' allows) plus some notes on things relevant to teh period you are modelling.

 

 

1. It might just be a matter of the way it is drawn but the Up Home should be at the toe of the points or in rear of the facing point locking bar for those points.  Equally the Down Home needs to be similarly positioned in relation to its facing point and point locking bar.

 

2. I think to make the track layout a little more realistic it might be useful to turn the diamond into a single slip thus creating a crossover between the Up & Down loop lines - so you would need an extra ground signal to go with that alteration.

 

3. Depending on the distance between the connections I would also be inclined to provide an additional stop signal to protect the trailing connection in the lower loop - the GWR tended to be rather prolific with stop signals in that respect. 

 

4. Similarly I could see a situation where a further stop signal is provided on the Up loop to protect the connection from the sidings - however here again you need to think about avoiding a forest of signals so providing this one really depends on the lengths you have to play with for your loops.  Technically the absence of this signal makes the matter of block working acceptances potentially a little bit awkward but the Up Starter could double for it in that respect

 

5. Now the interesting question of of signaling the yard connections at the right hand end.  Firstly the exit signal from the yard would have been required to be a semaphore (complete with a  ring on the arm) and not a shunting signal at that time - it being slightly different from going the other way, however there were ground shunting signals used for such connections in contemporaneous installations and the choice is yours.  More interesting is shunting back in and here you need to apply a little bit of lateral thinking to understand how it would be signalled - the shunting would be carried out by a  train travelling from left to right, i.e an Up train, therefore the connection where the loops become the single line is bound to be set for the upper (Up) loop for the train to arrive ready to shunt and while it shunts - so no need for a ground shunting signal.  However the next point, which effectively is the connection from the Upt loop to the sidings would have a ground shunting signal because it s a trailing point in the Up loop - I hope that makes sense.

 

Mike,

Thank you (I was hoping that you would see this blog entry and comment upon it).  

  1)  See reply to Andy above re the Up Home.  

  2)  As I'm modelling Baulk Road I felt that the diamond was a better bet than a single slip (and would probably be a lot easier to build in 2mm!!)  I will have to have a trawl through my "library" to see if my decision is a justifiable one.

  3)  I'm not quite sure what you mean there.  Do you mean a stop signal immediately before the Down Platform by the signal box (before the crossover)?

  4)  The distance between the diamond and the goods loop turnout at the up end of the Up Loop is unfortunately not as long as I would have ideally liked, although it will be about 20" or so minimum (250 scale feet), so I will have a look to see whether I could fit a further stop signal at that point.  Out of interest would such a signal be sited between the Up Loop and the Goods Loop?

  5)  I had assumed that the exit from the yard/Goods Loop would be controlled by the catch point (or is it a trap?) and it's associated point disc (I was going to provide one of the old rotating point discs showing green circle or red square here).  Your description of the shunting movement makes perfect sense (as does the need for a ground signal at the Up Loop/Goods Loop turnout.  I would assume this ground signal would be positioned outside the turnout (rather than within the loop if you see what I mean) as a reversing train would hide it if it were between the Up and Down loop tracks, is this assumption correct?

 

 

Mike's response is comprehensive as usual. One thing I would query is whether there would be a shunt signal to allow the train to draw forward of the advanced starter to shunt into the back siding. The siding turnout is quite close to the end of the loop. In many case there would be more room between that turnout and the end of the loop to allow the siding to be shunted without passing the advanced starter.

 

Don

 

Don,

I have drawn a shunt ahead arm on the Advanced Starter signal post to allow such a shunting movement (although at the resolution of the image you may have missed it).  It may be necessary to move the Advanced Starter further along the track (there is about 1 foot of plain track before the scenic break).

 

 

I will re-draw my diagram taking on board all of your comments and re-post again.

 

Ian

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richbrummitt
Dec 05 2014 13:22

Personally I would stick with a diamond. 

 

Mike,

 

I have modified my original diagram taking on board your comments, the revised diagram is shown below.  I've also put a Templot diagram of my whole layout so the you can better see the distances involved (each green square is 6" (~ 75'0" to scale).

 

Modbury Signal (2)

 

modbury
 
Although I have added a ground signal on the Up Loop to Goods Loop divergence, would there have been another one on the Main to Up Loop (the one with the FPL)?
 
Thank you for your help.
 
Ian

My comment relates to the Dummy which controls exit from the goods loop to the down main. This should be a yellow dummy. This has a yellow strip and shows a yellow aspect when ON and a green when OFF.

 

This can be passed when the crossing to the connect to the goods loop and the down loop is set to allow trains to shunt into the goods shed or adjacent siding and Up or Down trains pass. This is called a Lock-in. The second point controlling access to the goods shed and middle would be controlled by an hand lever. Thus the signalman does not have to pull of the dummy when shunting is in progress in the yard, only when access to the Down loop is required.

 

Many GWR lines had bi-directional signalling at such stations on the Up line, to allow through workings to pass whilst a Down freight trains was being shunted, with the brake van and several wagon in the down loop. These trains could be accepted by the signaller into the section provided the Up line was clear.

 

Without the bi-directional signalling only Up trains can be accepted during a Lock-in situation. The latter is defined when the locomotive and part of the train are in the goods loop and sidings, with the points set to the Up loop with or without part of the train in the Down loop.

 

If an Up train is fully in the Goods loop and sidings an Up or Down train can be accepted. I hope the above helps.

 

I also think that the access points to the Back siding would be further along the loop to allow it to be shunted in Lock-in mode.

 

Lisa

Including a slip on the diamond to create a crossover is quite common on the GWR. It saves  having to use the end turnout. I assume the down start could not be pulled off without gaining line clear from the next box so running forward would need some arrangement. Whereas a crossover would only involve the box.

Don

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John lewsey
Dec 05 2014 23:46
Hi Ian it should make an attractive scene with that lovely gentle curve Regards John

Many passing loops on the GWR system that had bi-directional operation on one loop also had the option of switching out the signal box, when not required.

 

This was controlled with a King lever, this allowed the the signaller to pull off both the Down and Up signals at the same time. Electrically the block instruments were also linked to bypass the switched out boxes instruments.

 

There were special bell codes that the signaller in the box to be switched out used to both the boxes on both sides, which had to be recipricated before switch out. Before the switch out could be started both sections and the loop had to be unoccupied.

 

Lisa

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