Locking problem

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Locking problem 01/07/2020 at 19:54 #128752
grahamj42
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AN53 (Liverpool South Parkway down fast starter) locks points 48 both ways. This doesn't seem right and causes delays when a down train from Hut's Cross crosses an up train for Weaver Junction.

The problem existed in the pre-loader V5 version.

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Locking problem 01/07/2020 at 20:15 #128753
GeoffM
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Agreed, that doesn't look right. Mantis 30959.
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Locking problem 01/07/2020 at 22:45 #128757
CGP
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It may be the Route Holding principle from the old Allerton Junction mechanical interlocking? To quote an old BRB Training Manual on mechanical interlocking

"Levers operating stop signals next in advance of trailing points operated from the same box should, when operated, lock such point levers in either position, unless the locking will unduly interfere with traffic movements for which there is adequate space between the signals and the points concerned"

Hope this helps

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Locking problem 02/07/2020 at 04:07 #128772
headshot119
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grahamj42 in post 128752 said:
AN53 (Liverpool South Parkway down fast starter) locks points 48 both ways. This doesn't seem right and causes delays when a down train from Hut's Cross crosses an up train for Weaver Junction.

The problem existed in the pre-loader V5 version.
Graham, it's accurate to the mechanical locking, AN53 off did indeed lock the points both ways.

"Passengers for New Lane, should be seated in the rear coach of the train " - Opinions are my own and not those of my employer
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Locking problem 02/07/2020 at 06:23 #128774
GeoffM
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I forgot that was a mechanical box!
SimSig Boss
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Locking problem 02/07/2020 at 14:15 #128793
grahamj42
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Thanks everybody. I should have done more research to see whether Allerton was still a mechanical box.

A note in the manual would be nice.

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Locking problem 02/07/2020 at 16:21 #128806
jc92
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grahamj42 in post 128793 said:
Thanks everybody. I should have done more research to see whether Allerton was still a mechanical box.

A note in the manual would be nice.
from the manual (under one touch routes)
"With the exceptions of Ditton, Edge Hill and Lime St, all of the signal boxes in the area are mechanical boxes, operated by a standard lever frame."

"We don't stop camborne wednesdays"
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Locking problem 02/07/2020 at 21:46 #128836
Steamer
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CGP in post 128757 said:
It may be the Route Holding principle from the old Allerton Junction mechanical interlocking? To quote an old BRB Training Manual on mechanical interlocking

"Levers operating stop signals next in advance of trailing points operated from the same box should, when operated, lock such point levers in either position, unless the locking will unduly interfere with traffic movements for which there is adequate space between the signals and the points concerned"

Hope this helps
What was the logic behind this? The only benefit I can see is preventing a signaller moving the trailing points under a passing train- but in any case, the points in question are locked by a track circuit? It does seem to add a lot of operational headaches to a layout.

grahamj42 said:
A note in the manual would be nice.
Note added to warn about AN53 back locking.

"Don't stress/ relax/ let life roll off your backs./ Except for death and paying taxes/ everything in life.../ is only for now." (Avenue Q)
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Locking problem 03/07/2020 at 09:46 #128852
kbarber
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Steamer in post 128836 said:
CGP in post 128757 said:
It may be the Route Holding principle from the old Allerton Junction mechanical interlocking? To quote an old BRB Training Manual on mechanical interlocking

"Levers operating stop signals next in advance of trailing points operated from the same box should, when operated, lock such point levers in either position, unless the locking will unduly interfere with traffic movements for which there is adequate space between the signals and the points concerned"

Hope this helps
What was the logic behind this? The only benefit I can see is preventing a signaller moving the trailing points under a passing train- but in any case, the points in question are locked by a track circuit? It does seem to add a lot of operational headaches to a layout.

I think it derives from the regulatory requirements (probably written when the regulator was still the Board of Trade). These things often ended up staying in the requirements long after the need for them had gone. (And of course - though I'm aware this wasn't the case at Allerton, which I believe was an LMR installation at the time of electrification - boxes often lasted a long time and relocking of frames tended to be done rather sparingly, given the skill needed of a locking fitter and the disruption to traffic while the interlocking was disarranged.)

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Locking problem 03/07/2020 at 10:39 #128859
clive
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Steamer in post 128836 said:
CGP in post 128757 said:
It may be the Route Holding principle from the old Allerton Junction mechanical interlocking? To quote an old BRB Training Manual on mechanical interlocking

"Levers operating stop signals next in advance of trailing points operated from the same box should, when operated, lock such point levers in either position, unless the locking will unduly interfere with traffic movements for which there is adequate space between the signals and the points concerned"

Hope this helps
What was the logic behind this? The only benefit I can see is preventing a signaller moving the trailing points under a passing train- but in any case, the points in question are locked by a track circuit? It does seem to add a lot of operational headaches to a layout.
It predates track circuiting being common and the concept of sectional route locking.

On a pure mechanical layout, you need some way to prevent points between two signals being moved under the train or as the train approaches them. Facing points will have a lock that includes a fouling bar, so you put the FPL lock in the locking for the signal in rear and require that signal to stay off until the train has reached the last facing points. But trailing points might well not have a FPL. So a reasonable approach is to keep them locked when the signal in advance is clear, because that's when a train could go over them at speed, making a derailment more likely if they're moved.

Once you've got track circuits you can track-lock the points, but that doesn't prevent them being moved as a train is approaching them at speed. For that, you need sectional locking that holds the points while any track circuit between the signal in rear and the points is occupied, plus a timeout on the signal in rear being replaced. That's what we get on relay and SSI interlockings and we're all used to it in SimSig. If it's fitted to a mechanical box, the SBSI can always override the general rule.

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Locking problem 03/07/2020 at 10:53 #128860
Stephen Fulcher
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As an example, Banbury South has all the points on the Up Main backlocked by BS5 signal even after the track circuiting and sectional locking was electrically applied. It was never removed because of the cost involved, and was a menace as the points exiting the Up Goods were also in the Up Main clearing point so you couldn’t accept another train from the North until the goods train was long gone. As a result some Signalmen used to let freights out of the loop upto a red at BS5 (Which was a fair way away) and then normalise the points behind the train before pulling 5.
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Locking problem 03/07/2020 at 12:13 #128868
jc92
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Exeter west has the same arrangement with 52,53 and 54 points on the down goods which are locked by 122 (the down main section signal) as they aren't track circuited and the system therefore can't prove its safe to move them until 122 has been returned to danger.

As Stephen says, sometimes putting a train out to 122 at danger is the better option if an up train is approaching to prevent delaying it while a slow moving goods clears 122 which is a fair distance away from the box.

"We don't stop camborne wednesdays"
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Locking problem 03/07/2020 at 13:09 #128871
Andrew G
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jc92 in post 128868 said:
Exeter west has the same arrangement with 52,53 and 54 points on the down goods which are locked by 122 (the down main section signal) as they aren't track circuited and the system therefore can't prove its safe to move them until 122 has been returned to danger.

As Stephen says, sometimes putting a train out to 122 at danger is the better option if an up train is approaching to prevent delaying it while a slow moving goods clears 122 which is a fair distance away from the box.
There is an alternative.

53 isn't back locked by 122 but is locked by a Track Circuit. If you put 53 AND 43 back after train has passed you will find 52 and 54 are no longer back locked by 122.

Last edited: 03/07/2020 at 13:09 by Andrew G
Reason: None given

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Locking problem 04/07/2020 at 01:29 #128954
grahamj42
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jc92 in post 128868 said:
Exeter west has the same arrangement with 52,53 and 54 points on the down goods which are locked by 122 (the down main section signal) as they aren't track circuited and the system therefore can't prove its safe to move them until 122 has been returned to danger.

As Stephen says, sometimes putting a train out to 122 at danger is the better option if an up train is approaching to prevent delaying it while a slow moving goods clears 122 which is a fair distance away from the box.
This has been bugging me since I bought the Exeter West simulation as it blocks the up passenger lines. It seems ironic in that the down goods train passes directly in front of the box.

I did once find the technique Andrew G describes, but forgot to write it down.

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Locking problem 04/07/2020 at 01:36 #128955
jc92
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grahamj42 in post 128954 said:
jc92 in post 128868 said:
Exeter west has the same arrangement with 52,53 and 54 points on the down goods which are locked by 122 (the down main section signal) as they aren't track circuited and the system therefore can't prove its safe to move them until 122 has been returned to danger.

As Stephen says, sometimes putting a train out to 122 at danger is the better option if an up train is approaching to prevent delaying it while a slow moving goods clears 122 which is a fair distance away from the box.
This has been bugging me since I bought the Exeter West simulation as it blocks the up passenger lines. It seems ironic in that the down goods train passes directly in front of the box.

I did once find the technique Andrew G describes, but forgot to write it down.
I was passed to work the box and I've never picked up on that one! Much appreciated Andrew.

"We don't stop camborne wednesdays"
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