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A quick question ... when a train starts to pass a green or clear signal, at what point will the signal turn to red or danger (assumn a 1950s ~ 60s time frame)? I seem to remember that the guard had to also observe the green/clear signal that the driver had passed.

 

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Ian

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I'm sure more knowledgeable people will be along soon...  AFAIK If it is a semaphore signal it will go back to danger when the signaller puts the lever back.  If MAS it will go red when the next section is detected as occupied, whether or not the guard has seen it as a proceed aspect.

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In my own boxes most of the early colourlight return to danger as the last wheel passes over the block joint at the signal.

 

Ely North Junction early 1970s

 

45, 42 and 40* last wheel replace. 11, 19 and 20 first wheel replace. 40* = 40 is the distant for Chettisham. ENJ ncontrolled red to yellow. Chettisham controlled yellow to green. If 40 was at green as soon as the first wheel passed over the block joint between ENJ G track circuit and Chettisham D track (not depicted) the signal changed from green to yellow. When G track cleared the signal changed from yellow to red.

 

Earlier colourlight = last wheel replace. Newer = first wheel replace.....

 

The latter is causing me a slight problem on my layout. A train passing the signal restores it and i see a slight reduction in speed induced by the asymetric brake. I'm starting a program of conversion to last wheel replacement to overcome this. The track circuit relay and signal control relay both need extra contacts to do this. It's proving a proper trauma to fit this all in.

 

Edit to add.. Oops the above box diagram has 19 as a semaphore.

 

Ely North Junction mid 1970s

 

edit to edit the edit.. I can draw the last wheel replacement circuit for you in BS376 if that helps?.

Edited by LNERGE
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1 hour ago, Ian_H said:

A quick question ... when a train starts to pass a green or clear signal, at what point will the signal turn to red or danger (assumn a 1950s ~ 60s time frame)? I seem to remember that the guard had to also observe the green/clear signal that the driver had passed.

 

Thanks

Ian

It depends!

I don’t go back to the 50s so can’t comment on guards duties although I am aware of periscopes fitted to Mk1 stock for that purpose.

 

1 hour ago, H2O said:

AFAIK If it is a semaphore signal it will go back to danger when the signaller puts the lever back.

Correct, but The Stationmaster regularly reminds us of the rules that tell the signalman (this is 50s not 2020s!) must not put the signal back until the train has passed any facing points in the route.

 

1 hour ago, LNERGE said:

Earlier colourlight = last wheel replace. Newer = first wheel replace.....

Again, yes and no, but a good simple rule.

 

Automatic Signals (as they were known throughout the 20th century) have almost always been first wheel.  BUT the track circuit doesn’t start until somewhere between 100 yards and 1/4 mile beyond the signal depending on gradient and number of aspects (50/60s practice).

 

Controlled Signals depended on regional preferences and operating requirements.  Back in 50s and 60s steam was still prevalent and signals had to remain off until the cab had passed, including allowing for piloting or double heading.  So, for example, Reading (1965ish) had what was known as Second Track (which was also last wheel for a loco that wasn’t as long as the second track).  Shunt signals were last wheel as it was likely that trains would be propelling past and didn’t want to go back in the drivers face.

 

True last wheel was used where banking engines were used.  So much of Glasgow Central and Motherwell had last wheel for the Ravenscraig coal and ore trains which had the third loco at the back.  I seem to recall that last wheel might have been a general Scottish approach applied everywhere, but can’t be sure.


And 21st century, yes, first wheel unless specifically requested otherwise.

 

Signal replacement is a minefield so that takes right back to where I started: It Depends!

 

As a modeller, just rejoice that whatever you do will be difficult to be proven wrong!

 

Paul.

 

 

 

 

 

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A stop signal is not put back to ON until the rear lamp of the train has passed the stop signal and additionally has passed over any facing points to which that stop signal relates.

 

Why? because the Guard must pass a signal OFF (otherwise he puts the brake on) and the facing points are locked by the OFF signal and so are prevented from being moved beneath the train.

 

Things have changed now.

Edited by meil
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I’ve applied last wheel replacement to all the colourlights and motor operated semaphores in work I’ve done in 12inch to the foot stuff I’m involved with. It was a lesson learned from early on in doing this sort of thing. The first double headed steam service to pass one of my signals produced an outcry of reports of a signal restoring early. 

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And Semaphores still must not be put back until the train has passed clear of all points in the route that that signal protects...

 

Andy G

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16 minutes ago, uax6 said:

And Semaphores still must not be put back until the train has passed clear of all points in the route that that signal protects...

 

Andy G

I don't think that was strictly true in all cases ?

 

I can think of instances on single-line passing loops where there were trailing crossovers and/or siding connections in the route between the Home and the Starting signal. Once the first train had arrived clear into its loop you HAD to put back the Home, otherwise it would not have been possible to clear the Home at the other end for the second train to enter the other loop, even if the first train was still straddling the aforementioned trailing connections.

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3 hours ago, LNERGE said:

I can draw the last wheel replacement circuit for you in BS376 if that helps?.

 

If that is no bother or miniml bother for you then I would very much like to see the "Last wheel replacement circuit", thank you.

 

Ian

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Really depends on the location. In my model world, Moss Lane is first wheel replacement, as in when the signals overlap TC is struck it reverts to danger. Sutton Dock uses the same system we have at Immingham West where the signal doesn't revert to danger until the train hits the overlap of the next signal. It was done this way to facilitate propelled shunting movement. 

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To quote General Signalling Reg 4.3 Replacing a stop signal to danger:

 

You must replace a stop signal to danger:

  • as soon as the last vehicle of the train has passed the signal, or
  • where there are points facing to the movement, as soon as the last vehicle is clear of the points.

This can be over ruled by Signal Box Special Instructions of course.

 

Andy G 

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OK, what the rules actually said... (BR 1950 Rule book)

 

Rule 68 (a)

A distant Signal must be placed at Caution immeditely it is passed by a train.

A stop signal must must be placed at Danger immediately the last vehicle of a train has apssed it, except that

  • (i) at a junction the signal immediately in rear of and protecting such junction must be placed at Danger as soon as the last vehicle has cleared the junction points
  • (ii) where station yard working is in opeartion, and in all other cases where the absolute block system is not being worked to, the stop signal must must be placed at Danger immediately it is passed by an engine; where however there are facing points in advance of such signal the stop signal must not be placed at danger until the engine has passed over these points.
  • (iii) should a train be brought to a stand with its rear portion outside a stop signal the signal must be placed at danger.

...

Rule 68(c)

 

At certain places signals automatically go to danger before the whole of the train has passed.  When such signals are controlled by a signalbox the levers must be placed in the normal position in accordance with the preceding paragraphs.

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15 hours ago, LNERGE said:

A very quick sketch and literally a screen shot. I will try to answer any questions. 
 

31CF1085-2D14-44E5-BB05-7BBFC41962DB.jpeg.1ed1efd609d9934e5cae3cb77ff30b03.jpeg

Hi, thanks for that .... it's made me feel a bit stupid because I'm not at all sure what you've shown me:blush: I've gathered that 1 GR and B TSR are relay coils but it's not clear what the three circuits are doing and I'm not sure what the notations TR/TSR/GR are referring to, I'm assumming that the V and the inverted V are perhap contact points?

 

Ian

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TSR restores the signal and gives it a one shot feature. The lever needs to be placed normal after each train and pulled again once B track is clear. With GR energised and A track occupied the disengagement of the signal is delayed after B track occupies until A track clears. 

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23 hours ago, Michael Hodgson said:

OK, what the rules actually said... (BR 1950 Rule book)

 

Rule 68 (a)

A distant Signal must be placed at Caution immeditely it is passed by a train.

 

There is a very important reason for that rule which is rarely appreciated by non-professional railman. A distant signal can't be cleared until the interlocking proves that all the running signals to which it refers have been cleared. Mechanical interlocking works both ways, of course, so as long as the distant is off none of the running signals can be put back if an emergency occurs. With the distant put back once the train has passed it, the signalman isn't constrained from immediately putting back the running signals if the need suddenly arises. (I will leave the question of the constraints that running shunts impose on one side for now.)

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10 hours ago, Ian_H said:

Hi, thanks for that .... it's made me feel a bit stupid because I'm not at all sure what you've shown me:blush: I've gathered that 1 GR and B TSR are relay coils but it's not clear what the three circuits are doing and I'm not sure what the notations TR/TSR/GR are referring to, I'm assumming that the V and the inverted V are perhap contact points?

 

Ian

 

TR Track Relay (NB track circuit is energised when the track is unoccupied, so that it fails safe in the event of power cut etc)

TSR Track Stick Relay

GR  SiGnal Relay

 

BS376   part 2 ... abbreviations explained after a fashion, and it shows standard symbols as well

 

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwjG3OCLirr2AhW1oFwKHc23AEEQFnoECAQQAQ&url=https%3A%2F%2Fallcivilstandard.com%2F%3Fsmd_process_download%3D1%26download_id%3D5832&usg=AOvVaw0JA6g_TxGXORfuUs0kJg1S

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8 hours ago, Michael Hodgson said:

 

TR Track Relay (NB track circuit is energised when the track is unoccupied, so that it fails safe in the event of power cut etc)

TSR Track Stick Relay

GR  SiGnal Relay

 

BS376   part 2 ... abbreviations explained after a fashion, and it shows standard symbols as well

 

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwjG3OCLirr2AhW1oFwKHc23AEEQFnoECAQQAQ&url=https%3A%2F%2Fallcivilstandard.com%2F%3Fsmd_process_download%3D1%26download_id%3D5832&usg=AOvVaw0JA6g_TxGXORfuUs0kJg1S

Hi Michael,

 

Thank you for the link to BS 376, I did try to find a copy yesterday without success, I shall have a read over the followings days and see if I can lift my knowledge base from none existent to a basic understanding. Thanks once again.

 

Ian

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On 08/03/2022 at 19:07, RailWest said:

I don't think that was strictly true in all cases ?

 

I can think of instances on single-line passing loops where there were trailing crossovers and/or siding connections in the route between the Home and the Starting signal. Once the first train had arrived clear into its loop you HAD to put back the Home, otherwise it would not have been possible to clear the Home at the other end for the second train to enter the other loop, even if the first train was still straddling the aforementioned trailing connections.

Facing points.

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2 hours ago, Ian_H said:

Hi Michael,

 

Thank you for the link to BS 376, I did try to find a copy yesterday without success, I shall have a read over the followings days and see if I can lift my knowledge base from none existent to a basic understanding. Thanks once again.

 

Ian

Railway signalling circuits in this country are drawn in a fashion that isn't immediately obvious to those accustomed to reading ordinary electrical and electronic circuit diagrams.

 

Whereas most circuit diagrams have a collection of components scattered across the page, with a rats nest of lines connecting the various terminals toegther, that style would make it too difficult to see how it follows the required logical concepts of railway signalling.  Because of the need to understand fail-safe implications and to facilitate fault finding, it is perhaps more clearly expressed more like a series of IF ... THEN...ELSE... statements in a computer programming language.

Consequently the convention is that a series of separate lines are drawn across the page, from the power supply on the left, through any relevant fuses, relay/lever/switch contacts to each device (lamp, relay coil, signal repeater etc) being operated, on the right of the diagram with the electrical return at the right hand end. 

What confuses people is that you don't see all of the terminals of a single component, such as a relay, all drawn together in one place.  Each relay coil is shown by one of these lines, the lamps of the signal it controls are shown by another, quite possibly on another page.

 

The IRSE "green books" (published in the 1950s/60s and often still to be found on ebay) can be very helpful if you want to understand the basic technicalities of traditional signalling. 

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7 hours ago, RailWest said:

Sorry, but can you elaborate please, as I don't understand the comment :-)

 

Until the rear of the train has passed the signal and any facing points associated with the signal.

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On 08/03/2022 at 16:56, 5BarVT said:

Controlled Signals depended on regional preferences and operating requirements.  Back in 50s and 60s steam was still prevalent and signals had to remain off until the cab had passed, including allowing for piloting or double heading.  

The standard on the LMR when steam was still about was that the signal should be replaced by the first wheel hitting the track circuit 150 feet past it. Once steam had all gone the standard was changed to the first suitable joint between  5 feet and 65 feet beyond the signal. Of course there were instances where the colour light was a Block Section Starting Signal, in which case there wasn't always a track circuit beyond it. In this instance the signal would be 'Last Wheel' replaced by the berth track circuit going clear after it had been occupied by the train. Last wheel replacement was also used where banking was authorised and in circumstances where a train could be propelled past it during shunting. Other special controls were applied where permissive working was permitted e.g. stations like Birmingham New Street where platform signals were replaced by Last Wheel or by the second track circuit past the signal becoming occupied. This was to protect against the driver of the second train following the preceding train past the signal because it was held off by his train being on the berth track circuit when the first train left.

In areas with colour lights and full track circuiting replacing the signal as soon as the points were held by track circuit operated route locking until the train had passed over them the actual point of replacement didn't matter.

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