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topic: 2588Lack of Trap Points?
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posted: 3 Dec 2014 22:36

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Richard_Jones
 
Heswall - United Kingdom

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Hi,

I've got involved in yet another project! - Not sure yet whether it will turn into a complete layout, but at present it is planned as a diorama from the road overbridge to the end of the platforms....

My question is - shouldn't there be trap points on both the up & down mains at the respective ends of the platforms to prevent over-runs? - Wouldn't that be a basic BoT requirements, otherwise how did this joint GW & LNWR line get away with it?

undefinedundefined1763_031617_480000000.jpg1763_031617_480000000.jpg

posted: 3 Dec 2014 23:00

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Martin Wynne
 
West Of The Severn - United Kingdom

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Hi Richard,

Generally traps are provided only on Goods lines.

Passenger loops on single-track lines wouldn't normally have trap arrangements. Here for example is Rubery on the Halesowen Railway:

RuberyStnfromDownHome.jpgRuberyStnfromDownHome.jpg

© D J Norton. Image linked from this excellent site: http://www.photobydjnorton.com

Cue a space for a catalogue of exceptions: :)








Notice also in this pic the classic arrangement of yard access via a diamond crossing to ensure a trailing access into the yard instead of a facing connection. This is a very common arrangement, although often the the diamond would have a single slip added -- see the single-slip video. Not needed here because the diamond is so close to the end of the loop.

regards,

Martin.

posted: 3 Dec 2014 23:03

from:

Richard_Jones
 
Heswall - United Kingdom

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Hi Martin

Many thanks - the old adage - I learn something new every day

best wishes

Richard

posted: 4 Dec 2014 02:16

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Dave Summers
 
Urchfont, Devizes - United Kingdom

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But shouldn't the facing goods yard entry on the RHS of the sketch have some sort of FPL even if the operation of the set of points is key-controlled?
Dave

posted: 4 Dec 2014 07:47

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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Dave Summers wrote:
But shouldn't the facing goods yard entry on the RHS of the sketch have some sort of FPL even if the operation of the set of points is key-controlled?
Hi Dave,

I think you can safely assume that there would be a facing points lock there. It would be shown on the diagram on the ground frame which is released by the key.

This is the diagram for the signal box at the station only. The usual reason for providing a separate ground frame is that it is more than the 350 yards length limit for the rodding run from a signal box. It's odd that the actual position of the ground frame isn't shown.

regards,

Martin.

posted: 4 Dec 2014 08:47

from:

Phil O
 
Plymouth - United Kingdom

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I don't think that a FPL would be required as the key will be attached to the token and thus any passenger train will not be using the turnout in a reversed condition. The clue is, there is no advanced starter beyond the turnout.

I await being shot down in flames.

Phil

posted: 4 Dec 2014 10:38

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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Hi Phil,

It is a single-track line, so passenger trains running east to west will see it as facing points. The points need to be locked for that.

regards,

Martin.

posted: 4 Dec 2014 13:59

from:

Alan Turner
 
Dudley - United Kingdom

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Richard_Jones wrote:
Hi,

I've got involved in yet another project! - Not sure yet whether it will turn into a complete layout, but at present it is planned as a diorama from the road overbridge to the end of the platforms....

My question is - shouldn't there be trap points on both the up & down mains at the respective ends of the platforms to prevent over-runs? - Wouldn't that be a basic BoT requirements, otherwise how did this joint GW & LNWR line get away with it?

undefinedundefined1763_031617_480000000.jpg1763_031617_480000000.jpg


Have a look at Hampton Loade and Arley on the SVR. They don't have trap points on their loops either.

The trap function at the goods yard for your diagram is provided by the double slips.

regards

Alan

posted: 4 Dec 2014 18:34

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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Alan Turner wrote:
Have a look at Hampton Loade and Arley on the SVR. They don't have trap points on their loops either.
Hampton Loade:

2_041333_180000000.jpg2_041333_180000000.jpg

2_041334_030000000.jpg2_041334_030000000.jpg

Martin.

posted: 5 Dec 2014 08:07

from:

Phil O
 
Plymouth - United Kingdom

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Hi Martin

The crossover turnouts are noted as being Staff Key. The key provides the lock, a number of branch lines had loops and sidings and did not have signal boxes at those locations have an Annetts key as the token or attached to the token this unlocks the FPL lever to release the turnout.

I suspect that Eardington on the SVR now has this arrangement. The ESR has 4 of these, I will trawl through my photo's to see if I have a picture of the arrangement.

Cheers

Phil
Last edited on 5 Dec 2014 08:10 by Phil O
posted: 5 Dec 2014 12:55

from:

Phil O
 
Plymouth - United Kingdom

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The picture I promised earlier, unfortunately the picture is not as clear as they could be as I have culled it from some not very good video footage. 
undefinedundefined38_050745_020000000.png38_050745_020000000.png

This shows the arrangement at the siding at Merryfield Lane.
One lever has a lock on it which can only be released with the key on the token, once this lever has been reversed, the turnout lever can be reversed. On completion of shunting operations and all levers returned to normal, the token is removed from the lever lock and the turnout is now safely locked for normal passenger operations to resume. 

This operation regularly takes place at Bere Alston and Coombe Junction, where the turnout can be locked in either direction.

Cheers Phil



posted: 28 Feb 2015 10:21

from:

D Foster
 
United Kingdom

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There would appear to be two distinct issues here.

1.  Trap Points

2. FPLs

1.  Trap Points can be said to be extremely rare in Passenger Carrying Lines - that is the lines that carry trains with passengers in them.  This therefore does not apply to lines that are used by passenger carrying stock - so long as there are no passengers in the stock.  This "subtle" difference is extremely important to operation - as soon as there is one passenger on a train a whole bunch of conditions apply to that train.

When a set of trap points is to be installed in a Passenger Carrying Line there are two alternatives.

(a) there can be a 440 yard length of over-run track before a runaway gets dropped in the dirt.  This will allow a movement to approach the trap while it is in its Normal (trapping) position. Basically - this doesn't happen.

(b) When there is no 440 yard over-run the working rule will be that when a Passenger Carrying movement is going to approach the Trap Points they must be Reversed so that they do not trap any runaway movement into the dirt but deflect it out onto the open line beyond.  Clearly this means that the line through the Reversed Trap and beyond must be clear to receive any over-run.

Once a movement toward the Trap has been brought to a stand the Trap Points can be set to their Normal (trapping) position.  (This will then free-up the line that an over-run would run to). Just in case the movement that has come to a stand should start to move before the Trap has been reversed for it a trap in this situation will usually lead to somewhere relatively more safe - for example a sand trap.  There is an example of this situation on the ELR at Bolton Road station.

On Single Lines where Trains Carrying Passengers can pass opposing movements will have both Distants against them (often Fixed Distants).  This means that they should be approaching at a speed that will allow them to stop dead at the first Stop Signal.  Their "over-run" provision in this case will be all the way through the line ahead to where an opposing train should be behaving in the same way - which is likely to be 440 yards away.  (If an approaching movement were to be running at a speed that would result in it blowing right through and out the other end it would be disastrous for it to be tipped off by a set of Traps...  Although it is arguable that hitting an opposing movement head on might be more disastrous).

I would imagine that if a Signalman saw that an approaching train was going to run through when it should stop he might set the points at the far end (the loop points that would be Trailing) against the runaway so that the movement might be derailed by the blades being set against it.

However, in much reading of reports I have never seen one of a train running right through a passing place when it should stop.  (What happened at Abermule was a head-on out on the Single Line).

---

Trap Points are normally Required by the BoT, MoT and subsequent bodies between Non-Passenger Carrying Lines and Passenger Carrying Lines.

Cases where Traps are not so provided are extremely rare.  In the one instance that I am aware of (that I worked) the lack of a set of traps meant that the siding could not have anything left in it without an attendant with it the whole time.  I have no idea why that siding was the way it was - we never used it in my time.

---

Incidentally - in the Halesowen line picture the left-hand Running Line through the loop has a nice Catch Point before the diamond of the connection into the sidings.  This would be there to prevent anything from rolling wrong-direction from the loop.  This Catch Point is a Trailing Point for normal direction working through the loop and therefore has no need for a Facing Point Lock.  (If  - exceptionally - a movement Carrying Passengers were to be made wrong-direction through the left hand side of the loop  - as seen - these Catch Points would have to be Reversed - closed - and Clipped and Scotched with a green flag or lamp provided to authorise the wrong direction movement over them).  (It's so much easier to do everything "normal working"!)

Will come back on FPLs in a moment.

posted: 28 Feb 2015 10:49

from:

D Foster
 
United Kingdom

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Meanwhile...  2nd issue...

2. FPLs

The BoT, MoT etc Require all points that are normally Facing for movements Carrying Passengers to be fitted with Facing Point Locks.  This may be a mechanical FPL, a self-locking Point Mechanism (point motor) or a Clamp-Lock drive.  (Clamp Locks don't actually comply with the strict letter of the Requirements but they have been accepted practice for a few decades now - they do the necessary job).

Anywhere not normally being used for movements Carrying Passengers does not have to have an FPL.  This does not, however, mean that these places will not have FPLs.  The railway companies were and are free to install FPLs (or equivalent) anywhere they want - because they enhance safe operation.

For mechanical FPLs extra provision would historically tend to have only been at places with a very high amount of traffic - such as at the exit from very busy marshalling yards or MPDs. 

Increasingly power worked Facing points everywhere have tended to all be fitted with self-locking mechanisms - or clamp locks.  This has also spread to the use of self-locking mechanisms or Clamp locks in Trailing Connections.

Basically there is relatively little extra cost between either the point mechanism with or without the locking element.  In addition there is relatively little extra cost in providing Route Relay Interlocking (RRI) or Solid State Interlocking (SSI) that includes point locking.  This relative small difference in cost is balanced against the problems and costs that arise if/when any form of Wrong Direction movement with a train Carrying Passengers needs to be made if the points that become Facing do not have installed locking. 

Essentially - all non-locked points have to be Clipped, Scotched and flagged before a Passenger Carrying, Wrong Direction movement can be made - this includes dragging a failed train back.  With the massive reduction in manpower this has become nearly impossible - or, at best, involves a massive delay - and delays now incur penalties.  Because penalties are cumulative a single delay can easily be far greater than the cost of providing locking.

For the really modern scene there is also a strong trend to make all Passenger Carrying lines Bi-Directional.  This Bi-Di facility can be complete or as an reduced provision.  In either case it means that all connections become potentially Facing for Passenger Carrying movements - and therefore all the points get to be fitted and interlocked with FPL arrangements.

In addition - the development of larger and faster freight trains from the 1960s tended to mean that any Facing Points in non-Passenger lines increasingly became fitted with FPLs or self-Locking equipment.

The freight-lines at Arpley Junction (Warrington) have a set of Switched Diamonds with mechanical FPLs that are nicely visible from a road over-bridge.

posted: 28 Feb 2015 11:47

from:

JFS
 
United Kingdom

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D Foster,

Many thanks for a comprehensive account - well done!

Just to add that the requirement for 440 yards in rear of a trap on a passenger line might be modified "within station limits" ie where the signal protecting the open trap had a further stop signal in rear of it with a clear 440 yards overlap for acceptance purposes.

Personally, I have always felt that this is a good example of the "rules" getting the balance of risks completely wrong - and the Cowden accident proves the point. Here a simple "start against" mistake by a driver caused death and mayhem. Had a trap been provided, the outcome would have been a bit of disturbed ballast and one very red face. You could also say the same about SN109 at Paddigton - though there were more complicated issues in play there (like why was a Postman driving a train wrong line for 200 yards?)

Some of the consequences of this thinking are utterly bizarre. To take one example (which provides the rare exception of a trap in a passenger line). On the Down Middle at Exeter West, a trap point was provided with a zero overlap in rear of the Home signal. As you say, the requirement before accepting a train was to close the trap and lock the FPL. However, on the adjacent Down Main, no such trap was provided - the "protection" of the adjacent running lines being by mean of three detonators worked from lever 110!!!

(I should of course, say "is" rather than "was" in the sense that Exeter west Signal Box still exists - at the Crewe Heritage Centre)

Best wishes,

posted: 28 Feb 2015 12:05

from:

D Foster
 
United Kingdom

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Glad you liked it :-)

The 440yards with a Trap Point - where the road did not have to be set back out onto clear line - would be In Advance of the Trap. That is - there would be all that extra track for an errant move to trundle along before landing in the dirt... The alternative - when a Trap has been restored to Normal (open)is to use a sand trap.

The weird middle/junction line at Norton Bridge has a remarkably short Trap with sand trap at both ends. It is, however, extremely rare for anything to be held inside this length of line and I would assume that when anything is moving into it that the route is open across the junction and protected by Fixed Signals on the Up Fast.

Where there are platform loops or any other odd arrangements that have a Trap in a Passenger carrying line the connection(s) will be protected by Fixed Signals - with the principle that movements are not supposed to pass these at Danger. When movements are not clear to run through - which would include the road not being set for them anything moving on the through line should also be worked slowly and able to stop dead In Rear of the signal.
In practice it would be very unusual for anything on the through line to be moving toward the connection at the same time that another movement was approaching the trap made safe for it. All these movements would tend to be relatively slow. The detonators (co-acting with the signal) are there to give warning if anything does go wrong. The rather loud "BANG!" would have everyone making an emergency brake application before looking around to see what was occurring. (...and asking some slightly terse questions).
(A long time ago I was near a set of co-acting dets when they were hit... an extremely effective laxative...)

I don't think that Station Limits have any altering effect on the Requirement - there just isn't usually room in Station Limits for the companies to mess about providing an extra long Trap facility - so everything approaching the Traps does so with the Reversed.  This does impact on how movements are shuffled within Station Limits - the Signalman has to make decisions about what goes first.  Sometimes a movement toward the traps will get held for quite some time while other traffic passes on the through line - even though the approach to the trap is apparently clear.

It should be noted that this need to Reverse the traps only applies to the approach of movements Carrying Passengers.  Everything else - including ECS - can move toward the Traps when they are set Normal - which means that anything on the through line can pass at whatever speed is appropriate - even though a run-by could derail the non-Passenger Carrying movement.

Cowden was part of my old patch - it was more like Abermule - there were other issues involved.  (It wasn't me).
Last edited on 28 Feb 2015 12:18 by D Foster
posted: 28 Feb 2015 12:21

from:

JFS
 
United Kingdom

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I think we are fully agreeing here!

Just to mention that the dets at Exeter West are NOT co-acting - they have their own lever in the frame (and there is more than one set). Thus the detonator levers work exactly as if they were trap point levers - ie they are fully interlocked with the signals: the signals cannot be cleared until the dets are clear AND the dets cannot be replaced with the signal off.

I would be reluctant to call this arrangement "unique", but I have never heard of another example of a detonator lever being locked by a clear signal.

If you want to have a play with this go here:-

http://www.blockpostsoftware.co.uk/downloads.php

download and install the "Exter West" simulation - see how you get on accepting the first train offered!

All of which shows that a modeller COULD have an arrangement which never existed on the Real Thing but he/she would have to do a lot of justification of it!

posted: 28 Feb 2015 12:37

from:

D Foster
 
United Kingdom

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:-) :-) :-)

After 60 years with half of them on the railway I would NEVER say that a way of doing things couldn't, much less wouldn't (even if you'd think it couldn't) be done on the railway!

(One of my instructors managed to completely and permanently vanish a ferry-van...)

I still continue to turn up new varieties of equipment that I had never heard of almost weekly.

Talking of which... Anyone know what a "Track Bolt" is? It's not a P Way component but some sort of weird combination of depression bar in one track and an FPL type bolt in the adjacent track... LMS or LMR I think... Any ideas?

Thanks :-)

posted: 28 Feb 2015 12:54

from:

JFS
 
United Kingdom

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.. I don't suppose you have tried Google.... :-) :-)

posted: 28 Feb 2015 13:17

from:

D Foster
 
United Kingdom

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Google? What's Google?

Also tried Bing...

Loads and loads of bolt type thingies with screw threads on them... :-(

(Did fine a book you might be interested in but can't PM the link to you yet).

The beasty I'm looking for is extremely obscure - I have only caught a glimpse of an LMSR or LMR single A4 copy page of it - and (of course) can't recall where...



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