Terminal Locking Rail

[ozzyo]

My understanding is that fouling bars are a generic term, the OPs picture is a clearance bar used to indicate to the signalman, that a loco is standing clear of the point. Fouling bars used to lock FPLs , I believe are known as facing point locking bars. , certainly in signal engineering docs I've read

 

Sorry mate but I think that you have some of your reply wrong.

If that is a clearance bar it would have to be over a loco length (approx. 70') from the point, due to the fact as soon as the first wheel flange is on the depression bar it is moved down and the circuit is made in the switch that is connected to the depression bar. As you can see the depression bar is about one or two sleepers from the toe of the point. So if what you say is correct the front wheel of the loco could be on the depression bar with all of the other wheels on the point!

 

The depression bar that the OP is talking about is the type that are normally used in bay platforms or loco release roads, as these can sometimes be a bit unreliable on track circuits the depression bar is an aide to the track circuit and also shows that the bay/platform is not fully clear. But could still be used under a calling on signal? 

 

The fouling bars that are used on facing points, are a bit different in use. In that the wheel flange does not normally come in contact with it. When the signalman wants to unlock a facing point he has to first get all his signals correct, then he has to unlock the point that is protected by the fouling bar this is worked by the same lever in the box as the facing point lock. When he pulls the lever to unlock the point the fouling bar moves in an arc to about rail head hight or above this is to prevent the point been unlocked when,

a) a train is going over the point, the fouling bar has to be long enough to be able to reach between the last wheel on the leading bogie and the first wheel on the trailing bogie, or

b )  when a train is stood with a wheel or more above the fouling bar.  

 

HTH

 

OzzyO.

[kenw]

My understanding is that fouling bars are a generic term, the OPs picture is a clearance bar used to indicate to the signalman, that a loco is standing clear of the point. 

These are depression bars, to indicate the presence of a train in the platform, either instead of, or supplementing, track circuits, as previous replies, and nothing to do with the points.

They were common in bay / terminal platforms, irrespective of them having engine release points or not. Newcastle had them on most, or all, bays before the 1990 resignalling, and none of these bays had release crossovers.

Also, in the OP picture, an engine standing on the bar still wouldn't necessarily be clear of the points, and post #4 says they're locally worked by hand anyway, (so from a ground frame), so there's no need to indicate to the signaller that an engines clear of the points

[The Stationmaster]

I'm getting rather hacked off with some of the stuff appearing in this thread so let's try and get it straight once and for all.  Some signal engineering sources (including some IRSE documents  - which doesn't come as a surprise having seen some I was sent for correection some years ago) seem to use the term 'fouling bar' to refer to just about any sort of bar which serves a detection purpose.  In reality bars were used for three different jobs, viz -

 

1.  Facing Point Lock(ing) Bars which were used to prevent a facing point coming unlocked while a movement was very closely approaching or passing through the point.  The bar would be situated either between the protecting stop signal and the point toe or actually through the point on whichever (or both) routes needing to be locked and in the latter situation could ether be on the running face or the outside edge of the rail.  They were normally rising bars - i.e. to unlock the FPL they bar had to lift and withdraw the lock bolt.

It is possible - but I cannot say with any certainty - that depression bars might have been used for this purpose in early power signalling schemes.

Facing Point Lock(ing) Bars were replaced by track circuits running through the point which they locked and that track circuit locked the lever which operated the FPL bolt.

 

2.  Clearance Bars would be found in advance of the trailing (toe) end of a facing point and were used to prove that a train had completely passed clear of the Fouling Point of that point.  A rising bar could conceivably be used in such a situation but equally an electric depression bar (as illustrated earlier in this thread) could be used.  Again, replaced by track circuiting.

 

3. Fouling Bars these were used in rear of a trailing point and were provided to - as the name implies - detect something which was standing foul of the other line trailing through that point and might well be used where a train had passed a [protecting signal - an excellent example, at Preston, could be seen recently in Dave F's photographic thread.  Again it seem depression bars were normally used and logically would be much simpler to arrange than a mechanical rising bar.

 

So techically we have two sorts of bar - a depression bar (usually operating an electric circuit) where the wheels of a vehicle/engine or whatever depress the bar from its normal position.  And a  rising bar - principally (exclusively?) used with facing point locks but perhaps also as a Clearance Bar where the bar is lifted by the operation of a lever in the controlling signalbox and the presence of a wheelset prevents it being raised and thereby keeps other equipment (e.g. a facing point lock bolt) locked.

 

Depression bars were also liberally used by some Companies/BR Regions simply to detect the presence of a vehicle etc in terminal platform stop block ends where poor rail conditions made track circuits unreliable - a very common situation on earlier power signalling schemes but particularly those of the 1930s and late '40s/early '50s.

 

So the equipment component is either a rising bar - or as this thread started - a depression bar.  The function is that of either simple detection of vehicle presenece (as this thread started) or as a Facing Point Lock(ing) Bar, or as a Fouling Bar, or as a Clearance Bar.

[Ron Heggs]

I'm getting rather hacked off with some of the stuff appearing in this thread so let's try and get it straight once and for all.  Some signal engineering sources (including some IRSE documents  - which doesn't come as a surprise having seen some I was sent for correection some years ago) seem to use the term 'fouling bar' to refer to just about any sort of bar which serves a detection purpose.  In reality bars were used for three different jobs, viz -

 

1.  Facing Point Lock(ing) Bars which were used to prevent a facing point coming unlocked while a movement was very closely approaching or passing through the point.  The bar would be situated either between the protecting stop signal and the point toe or actually through the point on whichever (or both) routes needing to be locked and in the latter situation could ether be on the running face or the outside edge of the rail.  They were normally rising bars - i.e. to unlock the FPL they bar had to lift and withdraw the lock bolt.

It is possible - but I cannot say with any certainty - that depression bars might have been used for this purpose in early power signalling schemes.

Facing Point Lock(ing) Bars were replaced by track circuits running through the point which they locked and that track circuit locked the lever which operated the FPL bolt.

 

2.  Clearance Bars would be found in advance of the trailing (toe) end of a facing point and were used to prove that a train had completely passed clear of the Fouling Point of that point.  A rising bar could conceivably be used in such a situation but equally an electric depression bar (as illustrated earlier in this thread) could be used.  Again, replaced by track circuiting.

 

3. Fouling Bars these were used in rear of a trailing point and were provided to - as the name implies - detect something which was standing foul of the other line trailing through that point and might well be used where a train had passed a [protecting signal - an excellent example, at Preston, could be seen recently in Dave F's photographic thread.  Again it seem depression bars were normally used and logically would be much simpler to arrange than a mechanical rising bar.

 

So techically we have two sorts of bar - a depression bar (usually operating an electric circuit) where the wheels of a vehicle/engine or whatever depress the bar from its normal position.  And a  rising bar - principally (exclusively?) used with facing point locks but perhaps also as a Clearance Bar where the bar is lifted by the operation of a lever in the controlling signalbox and the presence of a wheelset prevents it being raised and thereby keeps other equipment (e.g. a facing point lock bolt) locked.

 

Depression bars were also liberally used by some Companies/BR Regions simply to detect the presence of a vehicle etc in terminal platform stop block ends where poor rail conditions made track circuits unreliable - a very common situation on earlier power signalling schemes but particularly those of the 1930s and late '40s/early '50s.

 

So the equipment component is either a rising bar - or as this thread started - a depression bar.  The function is that of either simple detection of vehicle presenece (as this thread started) or as a Facing Point Lock(ing) Bar, or as a Fouling Bar, or as a Clearance Bar.

 

Mike

 

Thanks for this comprehensive explanation of the various 'bars' and their uses

 

Cheers

 

Ron

[Siberian Snooper]

I'm getting rather hacked off with some of the stuff appearing in this thread so let's try and get it straight once and for all.  Some signal engineering sources (including some IRSE documents  - which doesn't come as a surprise having seen some I was sent for correection some years ago) seem to use the term 'fouling bar' to refer to just about any sort of bar which serves a detection purpose.  In reality bars were used for three different jobs, viz -

 

1.  Facing Point Lock(ing) Bars which were used to prevent a facing point coming unlocked while a movement was very closely approaching or passing through the point.  The bar would be situated either between the protecting stop signal and the point toe or actually through the point on whichever (or both) routes needing to be locked and in the latter situation could ether be on the running face or the outside edge of the rail.  They were normally rising bars - i.e. to unlock the FPL they bar had to lift and withdraw the lock bolt.

It is possible - but I cannot say with any certainty - that depression bars might have been used for this purpose in early power signalling schemes.

Facing Point Lock(ing) Bars were replaced by track circuits running through the point which they locked and that track circuit locked the lever which operated the FPL bolt.

 

2.  Clearance Bars would be found in advance of the trailing (toe) end of a facing point and were used to prove that a train had completely passed clear of the Fouling Point of that point.  A rising bar could conceivably be used in such a situation but equally an electric depression bar (as illustrated earlier in this thread) could be used.  Again, replaced by track circuiting.

 

3. Fouling Bars these were used in rear of a trailing point and were provided to - as the name implies - detect something which was standing foul of the other line trailing through that point and might well be used where a train had passed a [protecting signal - an excellent example, at Preston, could be seen recently in Dave F's photographic thread.  Again it seem depression bars were normally used and logically would be much simpler to arrange than a mechanical rising bar.

 

So techically we have two sorts of bar - a depression bar (usually operating an electric circuit) where the wheels of a vehicle/engine or whatever depress the bar from its normal position.  And a  rising bar - principally (exclusively?) used with facing point locks but perhaps also as a Clearance Bar where the bar is lifted by the operation of a lever in the controlling signalbox and the presence of a wheelset prevents it being raised and thereby keeps other equipment (e.g. a facing point lock bolt) locked.

 

Depression bars were also liberally used by some Companies/BR Regions simply to detect the presence of a vehicle etc in terminal platform stop block ends where poor rail conditions made track circuits unreliable - a very common situation on earlier power signalling schemes but particularly those of the 1930s and late '40s/early '50s.

 

So the equipment component is either a rising bar - or as this thread started - a depression bar.  The function is that of either simple detection of vehicle presenece (as this thread started) or as a Facing Point Lock(ing) Bar, or as a Fouling Bar, or as a Clearance Bar.

Mike,

 

Two questions, did the GW use them and how were they shown on a signal box diagram?

[The Stationmaster]

Mike,

 

Two questions, did the GW use them and how were they shown on a signal box diagram?

The GWR very definitely used Facing Point Lock(ing) bars of course (as did all Companies as they were a legal requirement) but the way they were shown on 'box diagrams changed over the years - in fact the final Reading Drawing Over style for a facing Point Lock on a 'box diagram was similar to a shortened version of the BS376 drawing symbol for a Facing Point Lock(ing) Bar even when there wasn't one.  The example below is actually on the SDR but is drawn more or less in the final Reading style.

 

I haven't come across a clear example of the GWR using Fouling Bars although that obviously doesn't mean they didn't use them - just that I have yet to find any clear evidence ( I say clear evidence because there is a published photo of a depression bar at Leamington North where its purpose is not absolutely clear).

 

The Company definitely used depression bars as Clearance Bars in at least one location as photographic evidence exists (Leamington North again - where there was also a depression bar seemingly in use as a Facing Point Lock(ing) Bar).

 

I have yet to see any evidence of the GWR using depression bars in terminal platforms - I can't recall them at any of the 1930s locations and various diagrams I can find for the three main schemes doesn't indicate that they were present in any of them and I've never seen them in any photos of the pre 1914 GWR power installations but the last of those had gone before I started to get interested in signalling.  The LMS & LNER seem to have been the main users of them as far as my own observations are concerned.

 

[Siberian Snooper]

Thanks for the info Mike.

[Trog]

I think the original design use of the rods used to produce the stainless zig zag strips was welding sheets of armour plate together.