Signalling question.

[simon b]

Hi all, I need a little help with signalling an unusual section of track layout please. I've got a terminus platform line that has a siding diverging to a milk dock about a third of the way along its length. This siding can only be accessed when there is no train standing on the platform line, and is probably going to be worked with a ground frame as opposed to the signal box. 

 

In my mind as the milk siding joins the platform line well before the platform  starter signals, and it isnt a running line, it doesn't need its own exit signal? The ground frame would still need to be unlocked by the signal box anyway, so that should be enough protection I would think?

[simon b]

I should also say the only thing using the siding is milk tanker wagons, there would never be a loco "shut in" so to speak. There wouldn't be enough room to do that.

[Rivercider]

I am no signalling expert, so won't comment on details, but it might be important to have more information.

Which railway built and operated the station, and when is it set as signalling arrangements might vary over time,

 

cheers 

[simon b]

1 minute ago, Rivercider said:

I am no signalling expert, so won't comment on details, but it might be important to have more information.

Which railway built and operated the station, and when is it set as signalling arrangements might vary over time,

 

cheers 

Good point, thanks. 

 

Station was built by the LCDR and maybe the LBSCR, but its set in the late 1960's to early 1970's. Still using the steam era track and signals, but with blue diesels.

[RailWest]

A quick sketch would help a lot to have a better understanding :-)

 

Why do you think it would be on a GF rather than worked from the SB?

[simon b]

2 hours ago, RailWest said:

A quick sketch would help a lot to have a better understanding :-)

 

Why do you think it would be on a GF rather than worked from the SB?

 

Had a quick go in paint, it doesn't show the entire layout but just that platform road. I assumed a ground frame as it seems a similar situation to a loco release crossover between two platfrom roads, alot of those were hand worked even at larger stations.

 

 

The platform line is the outermost of three platform roads, which run into an overall roof. The milk dock line diverges just before the lines go under the roof, so the milk dock is outside the main building.

 

Edited April 19 by simon b

[5BarVT]

2 hours ago, RailWest said:

A quick sketch would help a lot to have a better understanding :-)

 

Why do you think it would be on a GF rather than worked from the SB?

A GF is the easiest way to implement it as it needs no other signalling (#): GF normal, operates as any other platform road; GF released, shunter in control of the platform.

# - slightly more tricky if the shunter needs to go out beyond the starting signal due to insufficient length between the point and signal.

Paul.

[Jeremy Cumberland]

30 minutes ago, 5BarVT said:

# - slightly more tricky if the shunter needs to go out beyond the starting signal due to insufficient length between the point and signal.

Am I right in thinking that the ground frame would need to be interlocked with the platform starter?

 

Obviously the ground frame is interlocked with the home signal.

[simon b]

1 hour ago, 5BarVT said:

A GF is the easiest way to implement it as it needs no other signalling (#): GF normal, operates as any other platform road; GF released, shunter in control of the platform.

# - slightly more tricky if the shunter needs to go out beyond the starting signal due to insufficient length between the point and signal.

Paul.

 

Thanks, that's what I thought the operation might be like. The idea I had for it was an 08 to trip 2 or 3 milk tanks into the dock and depart again light engine, so in theory it shouldn't need to shunt past the platform starter. However if it did need to go out past the starter would it require a shunt ahead signal below the platform starter, or be done by some other method?

 

1 hour ago, Jeremy Cumberland said:

Am I right in thinking that the ground frame would need to be interlocked with the platform starter?

 

Obviously the ground frame is interlocked with the home signal.

 

I would need to be able to use the platform starter to depart from the milk dock, as the rear of the train might not clear the points.

[Michael Hodgson]

There would obviously have to be a trap.

[simon b]

1 hour ago, Michael Hodgson said:

There would obviously have to be a trap.

Quite right, which leads me on to another question.

 

How many levers in the ground frame, 2 or 3? I assume a release lever of some sort, then a lever to throw the points, but would the trap point be on the same lever or separate?

[Innerhome]

I think the answer in part depends on how busy your terminus is - ie if it's a two track main line the siding would probably be fully signalled - if it's a relatively quiet rural terminus then the ground frame solution would be fine - as Michael Hodgson says you do need a trap point. I've had a quick look through a couple of the George Pryer signalbox diagrams books - couldn't find anything which was a direct replica - but Pulborough - sidings joining up loop - has a ground signal before the points on the platform line plus ground signal for the move into the sidings plus ground signal from the sidings - ie 3 in total (and the point has a facing point lock). Also Worthing West - in this case has a ground frame to control dock sidings joining the up loop - with the ground frame controlling ground signals from/to the dock lines with various slotting from the main signal box. The signalling record society has a large number of diagrams on it if you think of a similarish location to your layout which might help.

So I think it can be as simple or as complicated as you like - and you may wish to apply rule number one !!  

[RailWest]

The trap would be on the same lever as the entry point. The FPL would need a lever. It is arguable whether or not the FPL lever could act as the release, or that would require its own lever. Given that the GF would be worked by a guard or shunter 'on the spot' in a position where he could give hand signals, then I would questions whether any shunt signals would be necessary. Depends in part perhaps on the imagined date of installation.

[Michael Hodgson]

5 minutes ago, simon b said:

Quite right, which leads me on to another question.

 

How many levers in the ground frame, 2 or 3? I assume a release lever of some sort, then a lever to throw the points, but would the trap point be on the same lever or separate?

It would be on the same lever - effectively two points aranged as a crossover, with one etrack just leading to the dirt.

 

3 minutes ago, Innerhome said:

I've had a quick look through a couple of the George Pryer signalbox diagrams books - couldn't find anything which was a direct replica - but Pulborough - sidings joining up loop - has a ground signal before the points on the platform line plus ground signal for the move into the sidings plus ground signal from the sidings - ie 3 in total (and the point has a facing point lock). Also Worthing West - in this case has a ground frame to control dock sidings joining the up loop - with the ground frame controlling ground signals from/to the dock lines with various slotting from the main signal box. The signalling record society has a large number of diagrams on it if you think of a similarish location to your layout which might help.

So I think it can be as simple or as complicated as you like - and you may wish to apply rule number one !!  

My initial reaction to this thread was that the layout sounded imporbable, but there's a prototype for most things if you look hard enough!

I also thought it more likely to be worked by the box - the reason for GFs on engine run round loops is that there's often too far from the box for the permitted length of point rodding run.  Agreed it needs an FPL, could presumaby be worked by release lever if there's a GF, separate lever in box otherwise - it would only need to lock the point when it's normal, not into the siding.

[simon b]

Thanks for your input gentlemen, the closest example of such a situation I can find is Baker street on the Met railway. That had a very similar arrangement for the Chiltern court coal siding.

 

This isnt a busy terminus station, more urban backwater than Waterloo. So if we say a 3 lever ground frame with a release lever, a facing point lock lever, and then the points themselves, that should cover it? I'm guessing I'd need a "limit of shunt" board on the platform starter signal post too?

[RailWest]

>>>>I'm guessing I'd need a "limit of shunt" board on the platform starter signal post too?...

 

No :-) The signal is your limit of shunt. LoS boards are for wrong-direction movements in locations where otherwise there would be no signal.

[simon b]

1 hour ago, RailWest said:

>>>>I'm guessing I'd need a "limit of shunt" board on the platform starter signal post too?...

 

No :-) The signal is your limit of shunt. LoS boards are for wrong-direction movements in locations where otherwise there would be no signal.

 

Thanks, I'm still learning about how some of these things are used! 

[Grovenor]

7 hours ago, Jeremy Cumberland said:

Am I right in thinking that the ground frame would need to be interlocked with the platform starter?

 

Obviously the ground frame is interlocked with the home signal.

The ground frame needs to be locked normal for any move entering the platform so that would be home signal or any shunt signal giving access. Once a train has arrived in the platform the shunter can be given the ground frame release and do the shunting.

No need to lock the platform starter as its not conflicting and may be needed in case the train needs to pass the signal before the tail end has cleared the siding.. The shunter will need to put the ground frame back to normal or any subsequent arrivals will be locked out.

 

If the points were operated from the signal box then it would be usual for the starter to lock the points in either position for route holding. But this doesn't work with a GF and its the shunter on the ground who has the responsibility for not moving the points under a train.

Edited April 19 by Grovenor

[simon b]

4 hours ago, Grovenor said:

The ground frame needs to be locked normal for any move entering the platform so that would be home signal or any shunt signal giving access. Once a train has arrived in the platform the shunter can be given the ground frame release and do the shunting.

No need to lock the platform starter as its not conflicting and may be needed in case the train needs to pass the signal before the tail end has cleared the siding.. The shunter will need to put the ground frame back to normal or any subsequent arrivals will be locked out.

 

If the points were operated from the signal box then it would be usual for the starter to lock the points in either position for route holding. But this doesn't work with a GF and its the shunter on the ground who has the responsibility for not moving the points under a train.

 

Thanks for the explanation on how such a layout would be operated, it helps me plan the shunting sequence to get everything where it needs to be.

 

Just so I understand things fully a train cannot arrive directly into the siding as the ground frame must be locked to clear the signal into the platform, but a train can depart from the siding directly as the platform starter is not interlocked with the groundframe.

 

It's certainly going to be an involving task when it comes time for the milk train arrival, as the full sequence involves a runaround move using the other two platforms before it gets to this one. The fun part will be trying to do it all between the local passenger traffic.

[DCB]

The signalling problem comes from the illogical track layout.      I would expect the milk dock point to be operated from the signal box, locked in the straight position when either starter or home signals are off.   But I would not expect the station to have a milk dock.  Milk was typically dealt with at passenger platforms, loaded and especially unloaded., off peak in London.  It was a fairly quick operation, rolling churns around on their edges prior to going to tankers.
The dock would never have a "Train" enter, just a few wagons propelled in.  "Dock" platforms are often higher than the 3ft passenger platform maximum to make loading vans easier.; 

[simon b]

6 hours ago, DCB said:

The signalling problem comes from the illogical track layout.      I would expect the milk dock point to be operated from the signal box, locked in the straight position when either starter or home signals are off.   But I would not expect the station to have a milk dock.  Milk was typically dealt with at passenger platforms, loaded and especially unloaded., off peak in London.  It was a fairly quick operation, rolling churns around on their edges prior to going to tankers.
The dock would never have a "Train" enter, just a few wagons propelled in.  "Dock" platforms are often higher than the 3ft passenger platform maximum to make loading vans easier.; 

 

It's not really a problem, more of a puzzle that I needed the rules confirming before I play.

 

The milk dock as I call it is outside of the main station, it isnt connected to the station concourse at all. There is a milk bottling plant besides the station just like there used to be at Vauxhall, except I've given it a dedicated unloading siding as opposed to blocking a platform in the terminus. Some shunting is required to run around the train, and get the brake coach/van out of the way so the tanks can be propelled into the dock.

 

[simon b]

I had another look around and I think I've found a similar prototype for the track layout at Banbury station. 

 

The down platform relief line had what appears to be an un-signaled trailing connection to a pair of sidings about half way along it's length, there was a 3 lever ground frame provided even though the signal box is only at the platform end. Am I correct in thinking thinking this would be worked in the same way 5BarVT describes a few post's ago?   https://www.roscalen.com/signals/Banbury/South.htm

Edited April 20 by simon b

[Jeremy Cumberland]

The platform points look to be operated from the box, and this ground frame works one end of the single slip (the end nearest the platform) and the far siding points.

 

It looks like it's electrically locked from the signalbox, with a backlock on lever 1 (GF release). One of the buttons on the left will be to lift the backlock once the the signaller has pulled the appropriate lever in the box. I expect the other button sounds a buzzer in the box, requesting the ground frame to be released.

 

Lever 1 is half blue, implying an FPL, but I can't see one, and it's not on the lead. Perhaps blue has another meaning I am not aware of.

 

Lever 3 is spare.

[simon b]

1 hour ago, Jeremy Cumberland said:

The platform points look to be operated from the box, and this ground frame works one end of the single slip (the end nearest the platform) and the far siding points.

 

It looks like it's electrically locked from the signalbox, with a backlock on lever 1 (GF release). One of the buttons on the left will be to lift the backlock once the the signaller has pulled the appropriate lever in the box. I expect the other button sounds a buzzer in the box, requesting the ground frame to be released.

 

Lever 1 is half blue, implying an FPL, but I can't see one, and it's not on the lead. Perhaps blue has another meaning I am not aware of.

 

Lever 3 is spare.

 

Thanks, I found a picture of the signal box diagram after a search. Would the third spare lever originally have been to throw the points marked as (3) on the diagram? 

 

 

[Jeremy Cumberland]

6 minutes ago, simon b said:

 

Thanks, I found a picture of the signal box diagram after a search. Would the third spare lever originally have been to throw the points marked as (3) on the diagram? 

 

 

Ah, it looks like I was mistaken then, and that lever 2 works the platform points (and the far end of the slip). As you say, lever 3 worked the near end of the slip and the far siding points, but has now been taken out of use.

 

There's no need for an FPL since the platform is only signalled for movements in the trailing direction.