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GWR Signals and where they go?

gwr signals semaphore shunting signal backing signal siding signal ground disc great western railway 4mm oo gauge




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#1 dantimmy

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Posted 02 December 2011 - 17:30

Hi can anyone help me with this dilemma?

I have only just got into 4mm model railways in the last six months up till then it was no more than a day dream (for when I found the time and cash). Because a few grandparents worked on the GWR and coming from an area with a ex-GWR mainline terminus I decided to model my own GWR line.

I am starting with a small branchline that hopefully in the future will connect to a mainline allowing me to run almost anything I want. The station I have dreamt up is double track with sidings and a goods yard. Up till now I have found most of the things I need on the internet however I am really struggling with signals.

I vaguely understand the way stop,distant, starters work but I'm a little confused with where ground discs are placed. Are they required to be facing both ways etc. Upon buying "Modellers' guide to the Great Western Railway" I have discovered more signals, such as the shunting signal and backing signal. What is the purpose of these signals? Below I have drawn them on paint just in-case anyone else is in my shoes.
gwr signals.jpg

Below is a quick mock up on paint of the current plan for this layout.
map1.jpg

Any advice on how to place semaphores would be great.

Many thanks
Dantimmy
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#2 The Stationmaster

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Posted 02 December 2011 - 17:37

Dantimmy the first thing is to get the track layout looking right if at all possible as it is then much easier to signal in something akin to a prototype manner. The thing which stands out like a sore thumb on your layout sketch is the facing crossover at the left end of the Platform 1 which would have been very unusual on the real thing in the 1930s.

I'll come back to the signals later this evening as I'm off out now but the one with the 'S" on the arm is a Shunt Ahead signal, not a 'shunting' signal and has a special purpose (which will be explained).

#3 Gordon A

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Posted 02 December 2011 - 18:28

A trap point to stop runaway wagons from the sidings fouling the main line.
and just to complicate matters you may need some ground signals.

Gordon A
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#4 The Stationmaster

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Posted 02 December 2011 - 20:49

I think we'll start by tackling the various signals you have drawn (rather nicely). The arguably important ones are the Stop Signal and Distant Signal at the top of your list. The stop signal form - with variations - is used also for other purposes (e.g. with a ring on the face of the arm) so it has some variation but the distant signal is out on its own and more or less unique in its use and in many cases really unlikely to be seen on a model railway in its lone form in the way you have drawn. But it could very easily be seen in its lower arm form where it is mounted below a stop signal arm - for reasons which I'll come back to.

But first the stop signal. It serves the very important purpose of indicating to a Driver that he must stop his train at it and proceed no further until it is lowered (the GWR being a user of signals where the arm goes downwards, in the lower quadrant, to indicate 'clear'). And because it means stop when the arm is horizontal - as you have drawn it - it is used to protect things, to stop a train going where it should not go (as long as the Driver obeys the signal).
There are several things it needs to, and is used to, protect with the most obvious being points because they can be set for another route or to permit another, conflicting, movement.
Its next use (some might say its most important use) is to control the entrance to the block section between the signal box which operates it and the next signalbox in advance meaning that it could be controlling the entrance to and protecting several miles of railway or, more so in older times, possibly a mere few hundred yards. In this use it is known as the 'Section Signal' - because it controls entry to the block section.

The other use you need to know about is the Home Signal (a term which many people, erroneously use to refer to a stop signal). Although the name might vary (e.g. Home. or Outer Home) basically the first signal which a train reaches at the advanced end of a block section will include the words 'Home Signal' somewhere in its title. This signal might also be protecting points - in fact it usually is (or was before a track layout was rationalised) but it also serves a couple of critically important operational uses.
The first of these, as part of the block signalling system and enforcing the space separation between trains, is that it is the place from which the 'Clearing Point' is measured - this is the part of the line under his control which a Signalman must ensure is clear of any other train or obstruction with points correctly set before he is allowed to 'accept' a train under the Block Signalling Regulations from the signalbox in rear.
Thus the Section Signal controls the entrance of trains to a block section and a Home Signal marks the end of the block section.
The second critical thing which a Home Signal does is to mark the commencement of 'Station Limits' - these go from the outermost Home Signal to the Section Signal. Station Limits is an important piece of operating terminology and has nothing at all to do with the presence or otherwise of a station; every signal box which has a Home Signal and then a separate Section Signal applying to the same line in the same direction will have Station Limits.

Thus stop signals separate a block section and Station Limits (apart from their other role of protecting points etc) and in this respect they act as the boundary between sections of railway where different things are permitted, e.g propelling is permitted in Station Limits but not (in normal working) in a block section); in days gone all trains passing through a block section had to have a brakevan - but one wasn't need in Station Limits. These differences and the setting of the boundary between the two types of railway can influence the positioning of stop signals just as much as the presence of pointwork.

I'll stop 'for questions' here for the time being.
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#5 dantimmy

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Posted 02 December 2011 - 21:47

let me see if i got this right:

Gordon - I need a trap point to derail any runaway wagons from the sidings so they don't interfere with the mainline?

and stationmaster:

stop signals can be referred to as sectional signals (protects the entrance to a block section) and home/outer home signals (protect the exit of the block section) Both of these can be used to protect points and station limits is the area between the home signal and next sectional signal. Is that correct? When you mentioned propelling within station limits, what do you mean exactly, sorry if this seems a tad blond.

#6 dantimmy

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Posted 02 December 2011 - 21:48

map1.jpg

#7 beast66606

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Posted 02 December 2011 - 22:38

The trap (not catch to be correct) should derail trains leaving the sidings (without authorisation) - if you have room make the point to the line at the back of platform 2 a double slip and introduce a head shunt, (more prototypical anyway), this can also act as a trap then.

Like this

dantimmy.jpg

#8 Grovenor

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Posted 02 December 2011 - 22:43

Or, without the headshunt (it was quite common to shunt from the running line) and with the original crossover reversed.
map2.jpg
Keith

#9 The Stationmaster

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Posted 02 December 2011 - 22:47

let me see if i got this right:

Gordon - I need a trap point to derail any runaway wagons from the sidings so they don't interfere with the mainline?

and stationmaster:

stop signals can be referred to as sectional signals (protects the entrance to a block section) and home/outer home signals (protect the exit of the block section) Both of these can be used to protect points and station limits is the area between the home signal and next sectional signal. Is that correct? When you mentioned propelling within station limits, what do you mean exactly, sorry if this seems a tad blond.

You're getting there except it is Section, and not sectional.

Propelling means the vehicles being moved are in front of the engine moving them, i.e. they are pushed and not hauled (pulled).

The next installment wil be tomorrowl

Edited by The Stationmaster, 02 December 2011 - 22:51 .


#10 dantimmy

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Posted 03 December 2011 - 10:19

Or, without the headshunt (it was quite common to shunt from the running line) and with the original crossover reversed.
map2.jpg
Keith


Due to space I think I'll go with this one. What is the purpose of the small line directly right of platform 2 on the sidings? I this the trap point?

dantimmy

#11 beast66606

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Posted 03 December 2011 - 11:03


Due to space I think I'll go with this one. What is the purpose of the small line directly right of platform 2 on the sidings? I this the trap point?

dantimmy


Yes, it's the trap, be wary of overdoing it, two crossovers is a luxury. The no headshunt arrangement would generally be used on a quieter line, as it blocks the running line during shunts.

Frequently local yards were serviced by trains from one direction only, the traffic could even pass on a service to "the junction" (right to left on your plan), be remarshalled and then return on a service which allows easier access to the yard (left to right on your plan) - removing the need for two crossovers.

#12 dantimmy

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Posted 03 December 2011 - 11:40


Yes, it's the trap, be wary of overdoing it, two crossovers is a luxury. The no headshunt arrangement would generally be used on a quieter line, as it blocks the running line during shunts.

Frequently local yards were serviced by trains from one direction only, the traffic could even pass on a service to "the junction" (right to left on your plan), be remarshalled and then return on a service which allows easier access to the yard (left to right on your plan) - removing the need for two crossovers.


sorry but thats really confused me

#13 beast66606

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Posted 03 December 2011 - 12:52

Which bit ?

#14 dantimmy

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Posted 03 December 2011 - 14:45

"Frequently local yards were serviced by trains from one direction only, the traffic could even pass on a service to "the junction" (right to left on your plan), be remarshalled and then return on a service which allows easier access to the yard (left to right on your plan) - removing the need for two crossovers. "

this part...

#15 Gingerbread

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Posted 03 December 2011 - 15:05

It's a bit like trying to turn right on a busy road - it's probably easier to continue to the next roundabout, go round it and come back, so that the difficult right turn becomes an easy left turn (vice versa if you live in one of those odd countries that drive on the wrong side of the road).

In this case it is going to be difficult for a train travelling from right to left to shunt in the yard - so it will go on to another station where it can "turn round", then come back from left to right. This makes it much easier - it will only block the left to right line while shunting, rather than both.

David

#16 beast66606

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Posted 03 December 2011 - 16:55

As David says,

Sectional Appendices (for prototype locations) often had (well the proper company - LMS -ones did :P ) entries like "Cattle traffic for Rockborough* to be handled by down trains only"

*Mythical

#17 Grovenor

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Posted 03 December 2011 - 18:51

That said, if you want to do run round moves then you need to keep two crossovers, if not then the crossover to keep is the one nearer the platform, it was always preferred to keep the points close together and where the signalman could clearly see them.
Regards
Keith

#18 dantimmy

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Posted 03 December 2011 - 21:17

thanks everyone I think I will keep both for the time being, just got to decide on which semaphores go where.
dantimmy

#19 The Stationmaster

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Posted 03 December 2011 - 21:48

Right we'll move on to the next signal - the Distant Signal. The reason for this one is fairly simple to understand once you appreciate that trains take quite a long way to stop, even in the days of steam an express could take well over 1,000 yards (or even 1,000 metres) to pull up to a stand depending on its speed, load and theh gradient. Thus the Dtiver needed an advance warning of what would face him when he got to a Home Signal - would he have to stop or would the signal be 'off' (railwayese for 'clear')? And it wasn't just the Home Signal because it might still be necessary to stop at the Section Signal or any other stop signal between teh Home Signal and the Section Signal.

Thus the role of the distant signal evolved as the thing which gave the Driver that advance information he needed to slow his train, or keep running at speed. If he finds the distant at caution he will expect to find the Home Signal at danger and can adjust his speed accordingly. But to take account of the fact that other stop signals on his line might also be at danger the distant signal can only be cleared when all the stop signals which apply to that line at a signalbox have been cleared for the train. The Driver is thus told by the distant signal taht he has a clear run at the next signalbox.

But what all this means is that normally the distant signal will be a long way in rear of the Home Signal - it has to be in order to create sufficient braking distance when it's at caution. Which in turn means that you will rarely realistically see a lone distant signal on a model railway - even if our braking distances are far, far, shorter than the real thing.

But what we could realistically expect is a situation where there is a short block section and the distant signal for the next signalbox would be among the stop signals fore the 'box immediately in front of us. To avoid confusion we then have a 'lower arm distant signal' where it is mounted on the same post as a stop signal but lower down the post (hence lower arm). And to get the necessary braking distance there might be a lower arm distant below several (or all) successive stop signals at a signalbox.

The pic below shows a lower arm distant although in this case it is 'Fixed At Caution' which means that it can only ever show a caution indication - but it's still a lower arm distant signal.

The next instalment will look at subsidiary signals - which you can find mounted below a stop signal.

IMGP7007.jpg
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#20 dantimmy

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Posted 04 December 2011 - 12:11

this is all starting to make sense now. So in my layout I would only have distant signals to warn locomotives of the situation ahead (up/down the line from the actual visable layout). And they would be mounted below a stop signal, as in the picture?

#21 The Stationmaster

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Posted 04 December 2011 - 12:14

this is all starting to make sense now. So in my layout I would only have distant signals to warn locomotives of the situation ahead (up/down the line from the actual visable layout). And they would be mounted below a stop signal, as in the picture?

It all depends on your layout. If it is as per the sketches which have developed above you wouldn't have room for distant signals. But you could quite legitimately add lower arm distants for the next signalbox.

#22 dantimmy

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Posted 04 December 2011 - 16:45

Thats what I was thinking. So why do the GWR use additional signals and what are the reasons behind ground discs and their use?
dantimmy

#23 The Stationmaster

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Posted 04 December 2011 - 23:32

Thats what I was thinking. So why do the GWR use additional signals and what are the reasons behind ground discs and their use?
dantimmy

The next section will now be on Monday (lack of timeshare on the 'puter tonight alas) and as I've said will deal with subdisary signals. Then the section after that will deal with shunting/ground disc signals/dummies/whatever else folk call 'em (but always 'dummies' on the Western).
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#24 The Stationmaster

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Posted 05 December 2011 - 23:44

Regrettably we have just had a power cut and I lost the half completed post for 'Subsidiary Signals' and to be honest am in no mood to chance my arm with it again tonight (we also had a power cut last night but it was in the small hours but I'm still wary of getting another and throwing the mains circuit board at the first passing S&SE van I see). So tonight's edition will be delayed until tomorrow - sorry.

#25 dantimmy

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Posted 06 December 2011 - 12:23

Regrettably we have just had a power cut and I lost the half completed post for 'Subsidiary Signals' and to be honest am in no mood to chance my arm with it again tonight (we also had a power cut last night but it was in the small hours but I'm still wary of getting another and throwing the mains circuit board at the first passing S&SE van I see). So tonight's edition will be delayed until tomorrow - sorry.


No problem mate, hope everything gets sorted soon












Also tagged with one or more of these keywords: gwr, signals, semaphore, shunting signal, backing signal, siding signal, ground disc, great western railway, 4mm, oo gauge