Position of Signals relative to Track?

[Tallpaul69]

Hi All you signaling experts,

 

Can anyone point me in the direction of any diagrams that show the minimum distance standards that the GWR (and WR) used between signal posts and track for both semaphores and colour lights?

 

Many thanks

Paul 

[kitpw]

...try this link on RMWeb for starters....

 

 

Kit PW

[Tallpaul69]

1 hour ago, kitpw said:

...try this link on RMWeb for starters....

 

 

Kit PW

Thanks,

The above seems to suggest that 5ft from the OUTSIDE edge of the nearest rail would be a reasonable rule of thumb for modelers.

However, this seems to be the semaphore standard, I am not sure if this holds for colour light signals?

Cheers

Paul

[The Stationmaster]

17 hours ago, Tallpaul69 said:

Thanks,

The above seems to suggest that 5ft from the OUTSIDE edge of the nearest rail would be a reasonable rule of thumb for modelers.

However, this seems to be the semaphore standard, I am not sure if this holds for colour light signals?

Cheers

Paul

The structure clearances applied to any structure irrespective of what they were although the dimensions of the structure also came into it.   Colour light signals on the Western certainly seemed to be no differently sited in clearance terms from the semaphore signals except they were almost invariably on the left hand side of the line to which they applied (sometimes GPLs weren't on the left but that too was unusual).

 

The big difference with colour lights was the height of the red aspect above rail level which was highly standardised with very few exceptions - 12'6" for a straight post and 17'6" for a.bracket or gantry mounted signal head.  The only exception to the latter was in the case of the very few signals mounted on former semaphore  bracket or gantry structures such as at Slough or Oxford.

[St Enodoc]

18 hours ago, Tallpaul69 said:

Thanks,

The above seems to suggest that 5ft from the OUTSIDE edge of the nearest rail would be a reasonable rule of thumb for modelers.

However, this seems to be the semaphore standard, I am not sure if this holds for colour light signals?

Cheers

Paul

Only if your track gauge is to scale! Better to measure from the centre line in my opinion. In 00 I aim for a clearance of 30mm from the centre line on straight track, which isn't far from a scale 5ft from the outer edge of the nearest rail of P4 track.

[TheSignalEngineer]

4 hours ago, St Enodoc said:

Only if your track gauge is to scale! Better to measure from the centre line in my opinion. In 00 I aim for a clearance of 30mm from the centre line on straight track, which isn't far from a scale 5ft from the outer edge of the nearest rail of P4 track.

OK on an undersize gauge. I remember a colleague telling me of a job he went on in Pakistan. The design specified a distance from track centre for OHLE structures. Trouble was they used the dimension copied from a drawing intended for standard gauge track but the line was 5'6" gauge. Stopped riders hanging on the outside though. 

 

Back on topic, the old Board of Trade Requirements  Clearance Diagram specified a desirable distance from the track centre to the face of any structure was 7' 8" or 30.66mm at 4mm scale. The absolute minimum was to have a post at 4' 5 3/4 " from the running edge which is 6' 10" from the track centre line, so 27.33mm at 4mm scale. Allowance was made for cant and end/side throw due to curvature.

If a signal is placed in the interval between two tracks the minimum passing clearance is 18" from the bodywork to the structure.

This is the drawing as it appeared in the 1950 edition of the Requirements. 

[St Enodoc]

3 hours ago, TheSignalEngineer said:

OK on an undersize gauge. I remember a colleague telling me of a job he went on in Pakistan. The design specified a distance from track centre for OHLE structures. Trouble was they used the dimension copied from a drawing intended for standard gauge track but the line was 5'6" gauge. Stopped riders hanging on the outside though. 

 

Back on topic, the old Board of Trade Requirements  Clearance Diagram specified a desirable distance from the track centre to the face of any structure was 7' 8" or 30.66mm at 4mm scale. The absolute minimum was to have a post at 4' 5 3/4 " from the running edge which is 6' 10" from the track centre line, so 27.33mm at 4mm scale. Allowance was made for cant and end/side throw due to curvature.

If a signal is placed in the interval between two tracks the minimum passing clearance is 18" from the bodywork to the structure.

This is the drawing as it appeared in the 1950 edition of the Requirements. 

Thanks Eric. Your colleague's designer obviously forgot (or never knew) the relationship between the structure gauge and the load gauge...

 

The Blue Book is the source of my 30mm dimension and of much other useful information besides (mine is also the 1950 edition). An important thing to remember, of course, is Note 1 at the top - especially with the sorts of curves we use on model railways, which is why I stressed "straight track" in my earlier post.

[TheSignalEngineer]

6 minutes ago, St Enodoc said:

An important thing to remember, of course, is Note 1 at the top - especially with the sorts of curves we use on model railways, which is why I stressed "straight track" in my earlier post.

My modelling is done from first principles i.e. a couple of pencils fixed to a coach to trace out the side and end throw.

In the days before laser measurement the real railway even used similar  methods even down to a frame covered in expanded polystyrene blocks being used to find the minimum size of the Widened Lines tunnels at Kings Cross. Later in that area when I had to put in some extra signals i had to put a co-acting head ground mounted in the 6 foot on a tight curve. A Class 319 was parked on each line in turn and a plumb line used to determine if the envelope where the head needed to go was big enough, which it was by about 2" more than the minimum clearance. 

[St Enodoc]

Polystyrene blocks or similar are still used when verifying the rolling stock outline.

 

i use your pencil method to set out such things as platform edges  but I use the standard dimensions for things like signals, structures and bridge holes.

[Michael Hodgson]

Don't forget most of the GWR was once 7' 1/4" gauge.  Its structures presumably had to have greater clearance from the centre line than other companies.  Most signals would post-date gauge conversion though.

[The Stationmaster]

A big difference - readily visible in various places on the GWR network was what happened to the six foot following the end of the broad gauge especially in the vicinity of station platforms or pointwork near to station platforms.   In these locations the six foot was wider than normal because the critical dimension was the station platform side clearance - and this continued to be obvious in many places as platforms were raise of their faces were rebuilt. and of course it can still be seen today in some places on the recently electrified parts of the former GWR.

 

What this meant for signals was that it created room to place them in the six foot where that was advantageous for sighting because the normal clearances were still achievable.   Hence it was not unusual to find signals in the 6 foot (and not necessarily because the GWR was a right hand drive railway) - for example the signal post which can be glimpsed in the picture below was there because the six foot was the only place in which it could be properly sighted - it would not be properly visible if situated on the station platform.

 

[BWsTrains]

On 08/01/2021 at 04:04, The Stationmaster said:

A big difference - readily visible in various places on the GWR network was what happened to the six foot following the end of the broad gauge especially in the vicinity of station platforms or pointwork near to station platforms.   In these locations the six foot was wider than normal because the critical dimension was the station platform side clearance - and this continued to be obvious in many places as platforms were raise of their faces were rebuilt. and of course it can still be seen today in some places on the recently electrified parts of the former GWR.

 

What this meant for signals was that it created room to place them in the six foot where that was advantageous for sighting because the normal clearances were still achievable.   Hence it was not unusual to find signals in the 6 foot (and not necessarily because the GWR was a right hand drive railway) - for example the signal post which can be glimpsed in the picture below was there because the six foot was the only place in which it could be properly sighted - it would not be properly visible if situated on the station platform.

 

 

This is the "lost" photo AFAIK. It was of interest in these parts as I revisit the best location for my starters in a "between the tracks" situation on UH.

 

 

Edited February 29 by BWsTrains