3 Aspect Signals where to position on layout(N)

[Pierre Le Brun]

My intention is to position my 3 Aspect Signal somewhere near the turnout into the sidings. I have semaphore signals on both the main lines, not shown in photo. Any thoughts as to where I can position it? I know this won't be prototypical but I want to make use of it for my sidings. 

[Flying Pig]

Since it's a more modern-looking signal, I'd be inclined to swap it for one of the semaphores on the main lines, probably the one shown on the outer track ahead of the passenger train.  Then use the freed up semaphore on the inner track to protect the siding points, probably just in front of the loco.  I'm guessing there's a semaphore on the inner track, behind the camera?

 

Exit from the sidings would be controlled by a ground disc, which are very small in N and could be left out, though I see West Hill Wagon Works do a pack.

[DCB]

Generally  3 aspect colour lights are not compatible with semaphores.   UK Semaphores are 99.9% two aspect. Quite often two aspect  colour lights, either two lens or single lens were quite often substituted for semaphores on a one for one basis where sighting issues or "Modernisation" made them  suitable.            When 3 aspects came in they were generally automatic signals controlled by track circuits normally green when semaphores are normally red  and evenly spaced  as the old stations where signal boxes and the old semaphore signals  were located no longer existed.

[Flying Pig]

40 minutes ago, DCB said:

Generally  3 aspect colour lights are not compatible with semaphores.   UK Semaphores are 99.9% two aspect. Quite often two aspect  colour lights, either two lens or single lens were quite often substituted for semaphores on a one for one basis where sighting issues or "Modernisation" made them  suitable.            When 3 aspects came in they were generally automatic signals controlled by track circuits normally green when semaphores are normally red  and evenly spaced  as the old stations where signal boxes and the old semaphore signals  were located no longer existed.

 

There are still routes with absolute block sections controlled by semaphore mixed with track circuit block and colour lights.  So if the colour light is placed where I suggested - as a section signal reading into an area of colour light signalling - I think it should be fine. Someone will no doubt correct me if I'm wrong!

 

[The Johnster]

To follow on from DCB's and Flying Pig's comments, with which I fully concur; colour light signals in the UK during the green diesel period modelled here were of two fundamental types, firstly, and irrelevant to this discussion, 2-aspect semaphore replacements, very often distants with yellow & green aspects because of the frequent difficulty inherent in the long wire pulls of semaphore distants, which could be well over 440yards if a tunnel intervened.  Pulling off such a signal required considerable physical effort on the part of the signalman even if everything was in top working condition; any stiffness or wire stretching made it much worse.  Other examples were the GW searchlight signals used at Paddington, Bristol TM, and Cardiff General, direct replacements for semaphores to be read as if they were semaphores at night.

 

The second type is MAS (Mulitple Aspect Signalling controlled from a Panel Box), using three- or four-aspect automatic signals.  An automatic signal is one in which, by virtue of track circuiting, the passage of a train automatically sets the signal to red behind it, then as the train clears the next signal section (plus overlap), that is set to red and the original signal is set to single yellow.  As the train proceeds through further signal sections, the original signal then clears to double yellow in the case of a 4-aspect signal or green in the case of a 3-aspect.  Where anything more complex than a simple plain track signal section is involved, such as a junction, the signal is operated manually from the panel box.  In the case of trailing crossovers only occasionally used and similar installation, semi-automatic signals are used which are normally operated automatically by the passage of the trains, but can be manually overriden and worked from the panel. 

 

An automatic or semi-automatic MAS signal can be identifed by a plate on the post, a white rectangle with a black bar horizontally through the centre, 'semi' being printed above where applicable.   Manually controlled MAS signals have serial numbers on post-mounted plates with the prefixed ID initials of the relevant panel box, while automatic/semi automatics will be prefixed with the initials of the road they apply to, such as DM 123 for Down Main number 123 on that panel, or UR 456 for Up Relief 456 on that panel.

 

Your situation is that of a 'fringe box', where a manual semaphore operated block post borders the territory of an MAS system.  The MAS signal will be operated from the MAS panel and the semaphore box has equipment to 'describe' the train to the panel, which accepts it and clears the signal, which acts in principle as the semaphore box's starter or advance starter.  This would fit in well with DCB's suggestion of the 3-aspect signal replacing the semaphore post just this side of the bridge, and the semaphore being placed to protect the yard turnout just ahead of the D53xx. 

Edited March 23 by The Johnster

[SM42]

There is always the eierd and wonderful exception in the right circumstances. 

 

Kidderminster Junction's up home ( (KJ2 IIRC) was a 3 aspect colour light reading onto semaphores under absolute block signalling. 

 

However in your situation, the fringe box where the transition from absolute to track circuit block signalling occurs  makes sense,  swapping the semaphore for the colour light as previously suggested would be my solution too. 

 

Andy

[Michael Hodgson]

In a semaphore area, you could replace a distant signal with a 2-aspect Y/G, and the outermost starting singal with a 2-aspect R/G. 

This latter could be a 3-aspect if the next station had colour light signalling.

Furthermore, if a colour light signal had been provided there, the preceding stop signal (home signal) could be replaced with a 3-aspect.  This would show R to stop the train, Y to proceed, or G provided all of the other signals leading into the next section were off.

 

In simple terms, a green aspect in a semaphore area means you are clear all the way to the next signalbox; it's equivalent to having the Distant or any intermediate distant signals off, so it tells the driver that he can open up to line speed.  He can expect to see another distant at caution or yellow colour light before he encounters a stop signal at Danger.