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Generic Signalling

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Posted (edited)

Signalling discussions often get bogged down in talk of blocks, bell codes, homes and distants as if actually operating ten miles of busy mainline.

So, keeping it relevant, what is the minimum signalling required for a layout to be prototypical?

Is it as simple as

1. stop signal to indicate diverging routes ahead (can be assumed offscene, if not too far back from the diverging routes)

2. stop signal to start a movement from a terminus/onto a converging route/onto a single line

3. stop ground signal on final exit from sidings/goods loop

4. stop ground signal each direction on a trailing crossover

5. no signals on simple continuing lines (not modelled for long enough for blocks, homes, distants, etc to become relevant)

(everything else can be reduced to the seven elements in bold - a facing crossover is a diverging route, a diamond crossing is a diverging and a converging route, more complex goods yards are two or more sidings/goods loop, level crossings are continuing lines)

So a through station with routes diverging then converging again and a single fan of sidings could require just starters and one ground signal operated from a signal cabin nearby. Or a through station with continuing lines, a single fan of sidings and a trailing crossover could require just three ground signals operated from a nearby ground frame.

Simplest of all a through station with just continuing lines requires no signals at all, though if you model a signal cabin or level crossing there does need to be a stop signal somewhere nearby as a nod to the homes and distants nonsense.

Edited by NIR
add converging and crossover and continuing and single and level crossing

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It would depend on the track plan, NIR, and the use. If it was a busy passenger station, that’s one thing, but a goods yard could be a ground frame only with no signals.

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Posted (edited)
5 hours ago, jhb171achill said:

It would depend on the track plan, NIR, and the use. If it was a busy passenger station, that’s one thing, but a goods yard could be a ground frame only with no signals.

I'm just seeing if it reduces to some rules of thumb for trackplan and use, coming up with some generic situations like 'diverging route', 'terminus', 'sidings/loop' instead of talking technical terms like 'home' and 'distant' which seem fairly irrelevant. In your examples a busy passenger station is 1 and 2 in my terms, needing lots of splitters and starters, and a goods yard is 3, potentially needing just one ground signal on the final exit.

Edited by NIR

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Posted (edited)
On ‎4‎/‎10‎/‎2019 at 5:54 PM, NIR said:

Simplest of all, a through station with continuing lines requires no signals at all, though if you model a signal cabin or level crossing there does need to be a stop signal each direction somewhere nearby as a nod to the homes and distants nonsense.

So in a nutshell, in a model you need to signal the routes not signal the flows.

Signalling of flows (the blocks, homes and distants stuff) can be mimicked by having proper separation between trains on the layout - by not having them run on each others tails, by not running them right up to a conflicting route simultaneously and by using the late clearance of stop signals to check their speed before they negotiate points.

Edited by NIR
add level crossing

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Just a thought with continuous lines  a major feature of a few years ago was the level crossing manually controlled with gate protecting signals.  On a simple layout just a level crossing, keepers small house and small holding alongside, a small 2 lever ground frame for the two signals , the closing of gates and clearing of signals to herald the passing of the train  would allow a trainspotting layout.    

With the proliferation of electronics a motorised set of gates and signals such a layout is achievable. but it is the signals that are important to the action.

Yes NIR you signal routes nor flow - but as importantly it is the signals that stop movement- protecting the active route that are required.  Correctly placed shunting signals at yard exit points  and crossovers maketh the layout for me.  Plus now the supply of parts to more effective model rodding will lift a layout more than DCC and lights and sound!

Robert  

 

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Posted (edited)
On ‎4‎/‎13‎/‎2019 at 8:00 AM, Robert Shrives said:

Just a thought with continuous lines  a major feature of a few years ago was the level crossing manually controlled with gate protecting signals.  On a simple layout just a level crossing, keepers small house and small holding alongside, a small 2 lever ground frame for the two signals , the closing of gates and clearing of signals to herald the passing of the train  would allow a trainspotting layout.    

Yes, if you want to model the usual run of homes and distants you can just drop them in somewhere far away from everything else, maybe at a level crossing or a remote refuge siding.

 

Edited by NIR

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I've been thinking of generic signalling of loops on a single line, crossing being one of the few signalled flows wholly visible on a layout.

1. Bidirectional passing loop - splitting stop signal with arms of equal height before each entry, stop signal before exit at both ends (6 signals with 8 arms!)

2. Up/down passing loop - stop signal before each entry reading only to one side, stop signal before exit at opposite ends (4 signals with 4 arms, trap points before each exit at opposite ends allow running straight into the loop but this may be deprecated for passenger working)

3. Non-passenger loop - splitting stop signal before each entry with lower arm reading to dedicated goods-only line (or stop signal plus ground signal reading to dedicated goods-only line), trap points at both ends of dedicated goods-only line, stop signal (or ground signal) before exiting dedicated goods-only line at both ends (4 signals with 6 arms or 2 signals with 2 arms)

4. Non-passenger loop (ground frame only) - as 3 above but no stop signals just ground signals, non-passenger trains 'shut in' on dedicated goods-only line by token

All signals are placed at the toe of the entry point or before the fouling point at the exit (or at toe of trap point if fitted). For 1 and 2 non-crossing trains run straight through but crossing trains are both brought to a halt at the signal controlling entry to the loop before each pulling forward into the loop (except see 2 above). For 3 and 4 the non-passenger train is slowed then runs onto the goods-only line, the crossing train then runs straight through.

Edited by NIR

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I've also been thinking about shunting on a single line, shunting being another of the few signalled flows wholly visible on a layout.

Generally speaking, shunting can take place freely within the 'station limits' between the home (the first signal) and the starter (the last signal) in each direction of a single signal cabin. The position of these signals rarely coincide in each direction, which is not a problem on double lines but on single lines creates two different 'station limits' on the one line.

The simple but hard to find answer is that, on a single line, shunting can take place freely between the home signals in each direction of a single signal cabin. Which makes sense, this is the furthest extent a signalman can be sure of denying entry - his starters, even if lying beyond the homes in the opposite direction, are irrelevant to oncoming trains as they are facing the other way.

There are no 'shunt limits' on a single line, that concept only applies when shunting wrongway on a double line. On a single line a shunting movement can go as far as is necessary, even beyond the home signal if the next signalman is made aware of when the movement begins and ends or if the movement follows in the wake of a train departing in that direction.

So it's something you don't need to give a lot of thought to. You can shunt a single line however you like so long as you keep oncoming movements from either direction well away using the signalling until the shunt is finished. This is the one time you can properly chase a train!

Edited by NIR

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