Signalling for a GWR BLT

[john dew]

Hi Dave

 

I hope you will forgive me for posting here.....but its aimed primarily at you.....I know how much you admire GWR BLTs If you are not comfortable with me blundering in let me know and I will get it moved to Signalling .

 

I dont want to bore you with the detail.....it can be found in my layout topic.......but, by way of background, the branch is part of a larger (unbuilt) layout centred around a major station (Granby ....think Chester/Wrexham) and was devised to conceal the storage yard and provide me with an operating plank while I learned how to use RR&Co.

 

The branch (Cynwyd.......not the real Cynwyd) is complete now (signalling excepted) and it has become clear it has a lot more operating potential than I originally envisaged.....what is more the way I have developed the back scene justifies a higher traffic level.

 

To give you an idea of traffic there will be 10 daily passenger trips to the terminus...........sometimes the engine will run around at Cynwyd other times it will continue on to a mythical terminus in the branch storage , an autotrain will provide a connection for the secondary branch 8 times a day. There will be a daily Pick Up Goods (both ways) and a weekly Cattle Train, there will be a large Brewery to be serviced. Finally coal trains will pass through Cynwyd on their way to and from the colliery to the main line.....hopefully I will use RR&Co to bank the full load up the incline to the main

 

The track is all laid.....I know I should have put a trap in the coal siding......the signals will initially be cosmetic although I would like to have some working eventually.....cosmetic or not I would like them to be correct.

 

So heres the signal plan

 

 

 

Questions......starting at the Right hand side or clockwise

 

[1] The junction with the two branches is right under the road bridge and extremely close to the points for the loop and bay.........so the three arm down home that I have inserted is pretty meaningless do I have to have three arms on each of the advanced homes (I assume they would just be homes then) or would a branch have an indicator board?

 

[2] Similarly how do I indicate the road from the up starters.....or do I need to?

 

Note: I believe need the shunt ahead arms and the use of advanced starters and homes so that the locos can run around

 

[3] Passenger trains will not be using the loop so I assume I can control it with ground signals?

 

[4] I omitted a ground signal for the coal siding.....I now realise I need one

 

[5] Should entrance/exit to/from the Goods Yard be controlled by Ground Signal or Backing Arm and Siding Signal?

 

Note Sidings within the yard are controlled by hand levers

 

[6] Do I need another box at the junction between the branch and the colliery branch .....it is a scale 750 yards from the station box and because of the curve in the track not visible

 

If that were the case obviously I would change the signal names

 

I hope this isnt too complex and I havent made too many fundamental blunders.

 

Help and advice will be much appreciated

 

Kind Regards from Vancouver

[beast66606]

Hi John,

 

Answering your questions .,

 

1 - as you suggest, the home signals protecting the junction would each have 3 arms and the one near the points would go

 

2 - you can provide a shunt ahead signal on the platform end but with the goods yard as well I would suggest that one of the lines would have a starter so that engines can shunt around within the control of the signal box.

 

3 - yes or miniature armed signals.

 

4 - yes, one to get in and one to get out !

 

5 - again (as 3) discs or miniature arms would be fine, wouldn't use a backing signal, these were rare in the grand scheme of things

 

6 - Yes you would need another box, the mechanical limit is 350yds so it's too far for the station box, it would be very unusual for a junction to not have any form of passing loop though ...

 

hth

[john dew]

Hi John,

 

Answering your questions .,

 

2 - you can provide a shunt ahead signal on the platform end but with the goods yard as well I would suggest that one of the lines would have a starter so that engines can shunt around within the control of the signal box.

 

 

6 - Yes you would need another box, the mechanical limit is 350yds so it's too far for the station box, it would be very unusual for a junction to not have any form of passing loop though ...

 

hth

 

Thanks Dave.....sorry I didnt spot this sooner its been quite difficult to access RMWeb!

 

Thats exactly what I wanted......much appreciated....thanks for taking the time

 

If I may 2 follow ups.....everything else is very clear

 

Under 2 when a train leaves the bay or station platform through the respective Up Starter do I need to indicate which of the two roads the points are set for after the bridge or would that be linked to the starter ie it is sufficient for the signalman to pull the starter off (?) and set the road

 

Secondly......passing loop at the junction................I was hoping I could get away with the relief loop in the station?

 

Again many thanks

 

 

 

 

 

 

 

 

[The Stationmaster]

If you are going to signal it to GW standards (and some things are also dependent on the period you are modelling/when the signalling was installed you need to modify things a bit from somw of Beast's answers.

 

Firstly coming in from the right hand end GW practice once they began to do away with repeating splitting Home Signals would have been as you originally drew it - single arm off each line and then a 3 way splitter. (it was done that way to save signal arms/levers and simplify facing point locking prior to the track circuiting era).

 

Miniature arms served a very specific purpose on the GWR but they did use a shortened (3ft) version of a standard arm in some situations where the northern companies used a miniature arm.

 

If the loop line is used to cross trains then it would need running signals (short arms with goods line 'rings' on the arm) and if those signals dated from pre WWI you could safely use miniature arms (GW type to signal the route into the sidings), for later installation a co-located ground disc would be the most likely although there were instances where a short arm (again with a ring in these locations) was used.

 

As you have a junction splitting just beyond the road bridge by the signal box you do need splitting signals - in this case the junction looks close enough to have the splitting arms on the platform starters. As Beast suggested, with the amount of shunting likely to be going on a Shunt Ahead arm would be unusual at these signals - there would almost certainly be an Advance Starter on at least one of the lines beyond the junction.

 

The access to the colliery branch would most likely be worked by a ground frame but again this depends on the period - the GW closed a lot of signalboxes working that sort of connection in the period between the wars sometimes keeping the signalbox structure (and part of the original lever frame) but working as a ground frame. If you are modelling Pre-Grouping it would be reasonable to have it as a signalbox but by the late 1920s such 'boxes were being closed wherever possible.

 

hope that helps a bit more.

[Karhedron]

[3] Passenger trains will not be using the loop so I assume I can control it with ground signals?

One small note, although it may not have been common practice, it was not forbidden for passenger train lines to use ground signals. A good example was Marlow where the bay platform was controlled by a ground signal. This bay was frequently used by the local auto-train particularly in the summer when the main platform would often be taken up with excursion trains attending the regatta.

[The Stationmaster]

One small note, although it may not have been common practice, it was not forbidden for passenger train lines to use ground signals. A good example was Marlow where the bay platform was controlled by a ground signal. This bay was frequently used by the local auto-train particularly in the summer when the main platform would often be taken up with excursion trains attending the regatta.

 

Not exactly 'forbidden' but if there was a regular movement then a running signal should be provided and if there wasn't one a number of special precautions were necessary.

 

Incidentally 'a regular movement' could be counted in all sorts of ways (usually the most convenient one to avoid spending money on signal alterations) but a good guide would be that if it was in the Working Timetable then it should be properly signalled or if it was a regular feature of special working then it should be properly signalled. But there was always the 'out of sight, out of mind' clause of course.

 

Incidentally crossing loops with one line signalled for freight only use were quite common on the GWR. Not at all common were passenger train crossing loops where only one line of the two had a platform.

[beast66606]

Firstly coming in from the right hand end GW practice once they began to do away with repeating splitting Home Signals would have been as you originally drew it - single arm off each line and then a 3 way splitter. (it was done that way to save signal arms/levers and simplify facing point locking prior to the track circuiting era).

 

Mike - there is no room (on the model) for this arrangement which is why I agreed with Johns suggestion to lose the single homes and make the pair protecting the junction splitters but in the real world I would have gone down your suggested route.

 

Miniature arms served a very specific purpose on the GWR but they did use a shortened (3ft) version of a standard arm in some situations where the northern companies used a miniature arm.

 

Thats what I mean by miniature arms, GWR minis as opposed to proper ones

 

The access to the colliery branch would most likely be worked by a ground frame but again this depends on the period - the GW closed a lot of signalboxes working that sort of connection in the period between the wars sometimes keeping the signalbox structure (and part of the original lever frame) but working as a ground frame. If you are modelling Pre-Grouping it would be reasonable to have it as a signalbox but by the late 1920s such 'boxes were being closed wherever possible.

 

That's what i was going to suggest B)

[john dew]

Thanks for all the comments guys........a few supplementaries

 

 

Mike - there is no room (on the model) for this arrangement which is why I agreed with Johns suggestion to lose the single homes and make the pair protecting the junction splitters but in the real world I would have gone down your suggested route.

 

 

Now you have me worried...........did this never happen in the prototype where two routes converged just before a bridge and immediately after the bridge there were three possible routes/platform faces? (Right to to left in the diagram)

 

 

Going the other way (left to right) the starters on the platforms have to indicate the two separate roads after the bridge?

 

 

 

 

 

Thats what I mean by miniature arms, GWR minis as opposed to proper ones

 

 

For greater certainty.....on the relief loop I control that with signal posts and short arms with circles

 

 

 

Thank you for putting me right on the difference between starters and shunt ahead.......just to be certain I understand.......if a loco moves forward from a starter the following loco moves are controlled by the signal box whereas with a shunt ahead...they are not......provided the loco moves within the station limits

 

Finally thank you for the comment about the 350 yards mechanical limit. I had 700 yards in my mind (dredged from somewhere) but stupidly had forgotten the box is in the middle of the block

 

 

Once again the help is much appreciated

 

Kind Regards from Vancouver.....where if we dont get snow soon we will have a problem.........the Olympics start in 2 weeks!!

[The Stationmaster]

Thanks for all the comments guys........a few supplementaries

 

Now you have me worried...........did this never happen in the prototype where two routes converged just before a bridge and immediately after the bridge there were three possible routes/platform faces? (Right to to left in the diagram)

 

1. Don't worry - there's probably a prototype for it somewhere. What I suggested would be the usual approach as it simplifies some of the locking but distance and sighting and selective comnpression all come into as well hence Dave's reply to my comment.

 

2. The critical bit is to have signals that match the moves you are going to make on the track layout, slightly less critical (having achieved the first part) is to make it look believable and not over-signal or overcrowd the scene.

 

 

Going the other way (left to right) the starters on the platforms have to indicate the two separate roads after the bridge?

 

Again this depends on distance and the era in which the signals were erected. For example - quoting an exactly similar situation (albeit with an underbridge instead of an overbridge) at Frome Middle pre 1930s there was a single signal from each platform line (Main and Bay) reading to a splitting signal at the junction (the 'box was then called Frome South, but no matter). From 1935, with track circuiting added through the junction, the platform starters both became splitting signals and the original junction splitting signal went.

 

 

On the other hand Bodmin General, with only 90 yards between the signals, never had track circuits and retained a sepaerate splitting signal at the junction points until all the signalling was removed.

 

What you need to do, especially with GWR signalling, is get your era right to make it more believable.

 

 

For greater certainty.....on the relief loop I control that with signal posts and short arms with circles

 

Good idea, but make sure you only use them on the goods loop and not on any signal reading to it from a passenger line - the latter error is one of the most common I see on GWR signalling on layouts.

 

 

Thank you for putting me right on the difference between starters and shunt ahead.......just to be certain I understand.......if a loco moves forward from a starter the following loco moves are controlled by the signal box whereas with a shunt ahead...they are not......provided the loco moves within the station limits

 

Once again the help is much appreciated

 

Hmm, not quite got it John. Station Limits ends at the Starting/Advanced Starting Signal (best regarded using the modern term 'Section Signal') - i.e the signal which controls entry to the block section in advance.

 

When the Section Signal is cleared it indicates (assuming there is no accompanying handsignal given by the Signalman) that the line is clear to the Home Signal of the next 'box in advance. When a Shunt Ahead is lowered it only indicates that the train/movement is authorised to pass the signal in order to go as far as is necessary to carry out a shunt which cannot be wholly accomodated within Station Limits, and taht the movement must return within (i.e in rear of the signal) as soon as practicable and before the running signal will be cleared to allow it to proceed towards the 'box in advance.

 

Hope that clarifies