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Home signal position relative to FPL lock bar





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#1 Dave Holt

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Posted 02 April 2012 - 19:20

Is there a set position or distance for a home signal relative to a facing-point-lock lock bar? Or is the signal just positioned relative to the point blades, ignoring the lock bar? In this case, is there a minimum distance the signal has to be ahead of the point blades?
My model is an ex-LNWR single track branch terminus (based on Delph), set in the mid 1950's and the point & FPL is where the run-round loop and entrance to the goods yard split off the running line, so line speed is low. The signal is a bracket, with the main arm for the platform road and a subsidiary arm for the loop/yard diverging route.
Any advice would be most welcome.

Dave.

Edited by Dave Holt, 02 April 2012 - 19:22 .


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#2 The Stationmaster

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Posted 02 April 2012 - 19:32

Practice probably varied between Companies but logically the signal would be fairly close to the toe of the switch - we had one at our branch junction (albeit reading in what would normally be the wrong direction but regularly used for passenger train movements) which was as near level with the switch toes as made no difference.

Best advice is to look through pics of LNW/LMS on exLNW lines and see what you can pick out as any sort of theme.

#3 micknich2003

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Posted 02 April 2012 - 19:36

The signal must be in rear of the lock bar. Otherwise, if a train was stood at the signal, it would prevent the signalman from working the "FPL" lever. This is of course the purpose of the "Lock Bar", it can't be raised with a train stood on it, and thus ensures the points can't be moved under a train. Today, a track circuit does the samething.
See the bracket signal on the Down Line attached ex Hull & Barnsley Rly. Mick.

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#4 Grovenor

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Posted 02 April 2012 - 19:37

Dave,
The lock bar is there to prevent the points being moved ahead of or under the train after the signal is replaced, ie for route holding if the signalman is a bit quick on his signal replacement. As such the bar should occupy most of the space between signal and points. I thought your plan already showed the signal effectively at the end of the bar?
If the signal is brought up close to the point tips then the lock bar can either be omitted (on grounds of low speed and right under the bobby's nose, and being a single line no reason why he would want to move the points) or would have to be fitted to the points themselves either as an outside bar or fitted to the switch blades.
Do none of your photos show the area between signal and points?
Regards
Keith

#5 The Stationmaster

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Posted 02 April 2012 - 19:43

The lock bar was a legal requirement unless the points were worked from a ground frame - nothing to do with the position of the signalbox.

And of course the lock bar need not be in rear of the point toes - all it had to be was in advance of the signal and, of course, suitably positioned to lock the FPL.
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#6 TheSignalEngineer

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Posted 02 April 2012 - 23:00

The lock bar was normally 50'6" long. As splitting the bar along the point switches was expensive and an absoulte s** to maintain, it was usual on LM lines to find the signal about 60' from the toe of the facing points to give space for the bar. If there was a trailing connection between the Home signal and the facing points, e.g. a mainline crossover, the toes of the points would be far enough apart to fit in a full length bar, otherwise split bars on the trailing switches were needed.
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#7 Dave Holt

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Posted 03 April 2012 - 10:40

Thank you all for the helpful comments. I think I'll go for the 60 feet from the point blades, as per The Signal Engineer's suggestion.
The reason for my doubts, is that in reality, there weren't any signals at Delph at the period in questions - it was one engine in steam - but a bit limited in operation for a model! So I've assumed that signals were re-introduced right at the end of the LNWR era to allow a more intensive service.

Regarding the end of the lock bar nearer the point blades, the diagrams in the S4 Soc manual show the bar coming to the sleeper gap nearest the toe of the blades. This means the bar went past the track joint between the stock rail and the plain track, making access to the fish-plates (for greasing/gap adjustment) rather awkward. Was this the case, or should the bar be beyond the track joint?

Thanks again,

Dave.

#8 Steve Taylor

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Posted 03 April 2012 - 18:03

Dave - just had a hunt through and found pics of the locking bar arrangement at Goathland ........ the rail joint is behind the bar. Pics to follow

#9 Grovenor

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Posted 03 April 2012 - 18:26

making access to the fish-plates (for greasing/gap adjustment) rather awkward.

Not really a big issue, just put the nuts on the outside so the bar does not get in the way of the spanner. The bolts will pull out below the bar and the plate drop off downwards. Anything more than loosening for an inspection and grease will probably nean taking the lock bar off anyway.
Regards
Keith

#10 Steve Taylor

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Posted 03 April 2012 - 18:39

Posted Image
is that any good?
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#11 buffalo

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Posted 03 April 2012 - 18:49

Not really a big issue, just put the nuts on the outside so the bar does not get in the way of the spanner...

I always thought that was standard practice everywhere, but then I saw twa_dogs' photo, so maybe not?

Nick

#12 Dave Holt

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Posted 04 April 2012 - 09:53

Thanks again for the responses - all very instructive...why did I only ever look at locos for all those years?
The NYMR photo is most helpful, thanks very much..safely stored for future reference!

Dave.

#13 Jol Wilkinson

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Posted 04 April 2012 - 18:09

May I pick up on this thread and ask what happens in the case of one facing turnout immediately following another and there isn't sufficient distance for a proper length locking bar?

#14 micknich2003

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Posted 04 April 2012 - 19:14

The bars would be placed on the switches. Similarly, with a single or double slip the Lock Bar would be placed on the outside edge of the runing rail. Mick Nicholson.

May I pick up on this thread and ask what happens in the case of one facing turnout immediately following another and there isn't sufficient distance for a proper length locking bar?


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#15 kevinlms

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Posted 06 April 2012 - 01:01

The signal must be in rear of the lock bar. Otherwise, if a train was stood at the signal, it would prevent the signalman from working the "FPL" lever. This is of course the purpose of the "Lock Bar", it can't be raised with a train stood on it, and thus ensures the points can't be moved under a train. Today, a track circuit does the samething.
See the bracket signal on the Down Line attached ex Hull & Barnsley Rly. Mick.


What an interesting diagram. What is an 'electric fouling bar', I'm presuming its an earlier version of a track circuit?

Kevin Martin

#16 micknich2003

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Posted 06 April 2012 - 08:45

What an interesting diagram. What is an 'electric fouling bar', I'm presuming its an earlier version of a track circuit?

Kevin Martin


Not an early version of a track circuit but it does much the same. In the most basic form a train or engine etc stood on the bar would depress it and work an indicator of some sort in the signal box and thus inform the signalman the line was blocked. As a refinement, the electrical circuit could be made to work various lever locks etc. Mick Nicholson.
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