Braking issue on Caledonian Sleeper causes train to "run away" at Edinburgh

Sponsor Post - registered members do not see these adverts; click here to register, or click here to log in
R

RailUK Forums

TimboM

Established Member
Joined
12 Apr 2016
Messages
3,663
That's a regenerative brake. Rheostatic braking is nothing to do with the overhead line supply. Plenty of rheo brakes on diesels.
A lack of overhead power supply has everything to do with the rheo brake not working on a 92 (and I'd imagine any other electric loco).

Yes, rheostatic braking is when the energy is dissipated via heat and regenerative is when it's returned to the overhead AC supply (92s can do both incidentally, but only passed for rheo braking on NR metals). However, the rheo brake requires all manner of other components to be working which will be shut down if the loco isn't receiving any power.

For the resistive braking to work (rheo or regenerative) the traction converters (and all their associated cooling mechanisms) have to be working to convert the 3 phase AC from the traction motors (working as alternators) to DC.

Then for rheo braking there's the brake resistors which generate huge amounts of heat - each of the two "brake stacks" on a 92 is rated at 2.5MW (same as 830 three-bar electric fires to get an idea of the heat being produced). These resistors are cooled by dedicated fans - these are serious bits of kit driven by hefty motors and the loudest fans you hear on a 92.

If the pan has dropped, the loco is receiving no power - the traction converters won't therefore operate, nor will all the key components to operate or cool 5 MW of brake resistors. Hence pan dropped/no OHLE power = no rheo brake working.
 
Last edited:

TimboM

Established Member
Joined
12 Apr 2016
Messages
3,663
Ah - this goes some way to satisfying my intrigue from back in the thread as to why RAIB mentioned 92s *not* providing regenerative braking.
From what I could make it was only included as part of RAIB's background explanation of some of the technicalities involved. I couldn't see any real relevance of that little factoid to the incident.
 

O L Leigh

Established Member
Joined
20 Jan 2006
Messages
4,346
Location
In the cab with the paper
Because its not exactly unusual for multiple working systems to be connected to multiple locomotives simultaneously is it?
That kind of being the point.
But that is not the use to which they are currently being put. @TimboM has kindly confirmed the suspicion I'd been harbouring that there is a difference between two locos being directly connected to each other in order to work in multiple and two locos being attached to the same rake of Cally Sleeper Mk5s.
 

big all

On Moderation
Joined
23 Sep 2018
Messages
826
Location
redhill
But that is not the use to which they are currently being put. @TimboM has kindly confirmed the suspicion I'd been harbouring that there is a difference between two locos being directly connected to each other in order to work in multiple and two locos being attached to the same rake of Cally Sleeper Mk5s.
your wording seems to suggest you thinks there is a possible danger or very bad working practice with this particular combination off locos or stock ??

in general bodges dont get into operational practices as they tend not to be safe
we need to remember we have highly skilled responsible railwaymen keeping things safe
in general railwaymen are off a breed and will quickly weed out unsafe working as it goes against the grain
 

Bald Rick

Veteran Member
Joined
28 Sep 2010
Messages
13,623
I would also add to your comments ref swiss cheese hole alignments the fact that the signaller wasn't otherwise engaged because I assume if he was then he wouldn't have been able to set a straight route through Edinburgh Waverley station and out the other end because the driver wouldn't have got through to him - it wasn't a GSMR emergency call according to the report so wouldn't get higher priority over other calls.
Agreed, and that’s what I meant by “signaller was able to action”
 

MotCO

Established Member
Joined
25 Aug 2014
Messages
1,341
Having read all the responses so far, I have seen a lot of discussion about how much should be fail-safe built-in as opposed to being in procedures for staff to follow.

I write as someone not associated with the railways, so please excuse any naivity in this post. I assume that all staff, whether drivers, train managers, fitters have a series of procedures to follow, and my concern is not to over-burden these staff such that an error could slip in. On the other hand, I am not advocating fully automating all procedures or introducing fail-safe measures on everything - a comment made earlier suggested that having so many checking systems meant that there were more things which could fail, either delaying the train or forcing a cancellation. The trick is to ensure that this equilibrium is somehow kept in balance, and for deciding who should arbitrate when the equilibrium is in danger of being upset.
 
Joined
7 Aug 2011
Messages
207
I boarded the sleeper from a bay at Aberdeen, but I've only done Aberdeen on CS once so no idea if that's normal or not.
I (think) I've always arrived on 6S in Aberdeen, one of the through platforms. This allows the loco to run around via 6N and 7 to take it away to the depot.
 

jfowkes

Member
Joined
20 Jul 2017
Messages
363
your wording seems to suggest you thinks there is a possible danger or very bad working practice with this particular combination off locos or stock ??

in general bodges dont get into operational practices as they tend not to be safe
we need to remember we have highly skilled responsible railwaymen keeping things safe
in general railwaymen are off a breed and will quickly weed out unsafe working as it goes against the grain
While railways are a much safer industry than most, recent incidents show that even railway staff are at risk of slipping into unsafe working practises.
 

O L Leigh

Established Member
Joined
20 Jan 2006
Messages
4,346
Location
In the cab with the paper
your wording seems to suggest you thinks there is a possible danger or very bad working practice with this particular combination off locos or stock ??
No, not as such. There's just a quirk of incompatibility that needs to be kept in mind when coupling and uncoupling these trains. Unlike the Nightstar, the Cally Sleeper is not intended for "top and tail" multiple working so the instances of two locos attached to the same train should be limited to splitting the portions, and even that situation is not necessary and can be avoided. It's one of those situations where Option A (going away and redesigning everything to make it robust enough to cope with extremely unlikely situations incurring unknown costs and delays) was less preferable to Option B (don't have more than one loco attached to the 61 way connection at a time).

in general bodges dont get into operational practices as they tend not to be safe
we need to remember we have highly skilled responsible railwaymen keeping things safe
in general railwaymen are off a breed and will quickly weed out unsafe working as it goes against the grain
While railways are a much safer industry than most, recent incidents show that even railway staff are at risk of slipping into unsafe working practises.
Both statements are true, which is why processes and procedures need to be clear and unambiguous so that their intent is clear and they are easy to follow. The new wording for the Rule Book that the RAIB wants the RSSB to consult on will achieve this.
 

Bletchleyite

Veteran Member
Joined
20 Oct 2014
Messages
57,064
Location
"Marston Vale mafia"
No, not as such. There's just a quirk of incompatibility that needs to be kept in mind when coupling and uncoupling these trains. Unlike the Nightstar, the Cally Sleeper is not intended for "top and tail" multiple working so the instances of two locos attached to the same train should be limited to splitting the portions, and even that situation is not necessary and can be avoided. It's one of those situations where Option A (going away and redesigning everything to make it robust enough to cope with extremely unlikely situations incurring unknown costs and delays) was less preferable to Option B (don't have more than one loco attached to the 61 way connection at a time).
My question would be how did this fundamental error get in the design? I work as an IT consultant, and a key part of my job is identifying things that while the customer didn't put them in the spec would, if not fixed, cause problems. This is a classic example of that, and could easily have been "designed out".

"The customer didn't spec it" is the sign of a company that just builds what they're told without thinking - a bad company.
 

HSTEd

Veteran Member
Joined
14 Jul 2011
Messages
11,594
No, not as such. There's just a quirk of incompatibility that needs to be kept in mind when coupling and uncoupling these trains. Unlike the Nightstar, the Cally Sleeper is not intended for "top and tail" multiple working so the instances of two locos attached to the same train should be limited to splitting the portions, and even that situation is not necessary and can be avoided. It's one of those situations where Option A (going away and redesigning everything to make it robust enough to cope with extremely unlikely situations incurring unknown costs and delays) was less preferable to Option B (don't have more than one loco attached to the 61 way connection at a time).
Except this situation was apparently common enough that special procedures are required to prevent it from happening.

Not being able to connect two locomotives to the Cally Sleeper rake at once is a definite reduction in flexibility, especially in unusual situations where crew may be stressed by delays etc etc. It can lead to situations like the one that arose, when people are handling jumper connections at times when no coupling has occurred.

Procedural control is inherently less preferable to non procedural control.
 
Last edited:

O L Leigh

Established Member
Joined
20 Jan 2006
Messages
4,346
Location
In the cab with the paper
My question would be how did this fundamental error get in the design? I work as an IT consultant, and a key part of my job is identifying things that while the customer didn't put them in the spec would, if not fixed, cause problems. This is a classic example of that, and could easily have been "designed out".

"The customer didn't spec it" is the sign of a company that just builds what they're told without thinking - a bad company.
I think "designed in" would not be the most accurate description of what happened, but rather that it wasn't clear which standard applied when specifying the BPICs used on the Mk5s (RAIB Paras 104-108). The BPICs have been/are being modified to bring them closer to compliance (Paras 122-124) which should also make the venting more audible should the BPICs ever be left in the wrong position again (as described in Paras 58-59), something that would have got the shunter's attention.

Except this situation was apparently common enough that special procedures are required to prevent it from happening.

Not being able to connect two locomotives to the Cally Sleeper rake at once is a definite reduction in flexibility, especially in unusual situations where crew may be stressed by delays etc etc. It can lead to situations like the one that arose, when people are handling jumper connections at times when no coupling has occurred.

Procedural control is inherently less preferable to non procedural control.
Should there be a problem? No perhaps not. But any issues with single loco working aside, does it really matter?

I'm sure it would be lovely to have the flexibility to have a second live loco attached, but the Cally Sleeper is intended only to work with one loco at a time so any issues about attaching a second are really not that much of a worry. It is only "common enough" in the sense that the train is split at Carstairs, but the instructions for that have now been updated to ensure no further foul-ups while ensuring only one loco at a time on the 61 way connections, so the situation is resolved.

You may not like procedural controls and feel that they are inferior, but this is only one very very minor example of the huge numbers of procedural controls that make up daily operations on the railway. It is neither unusual for railstaff to have to implement these nor strange for us to confront them.
 

O L Leigh

Established Member
Joined
20 Jan 2006
Messages
4,346
Location
In the cab with the paper
@Bletchleyite - Apologies. I though you were referring to the BPICs, but on reflection I can see now that you weren't

I think you might be better placed to answer your own question than I, as I imagine that the answer lies in how far CAF and their contractors can be held liable for the problem. If the issue is with their own kit then clearly it's down to them, but if the problems are with the pre-existing (but now redundant…?) equipment installed in the Cl92s 25+ years ago then I'm not sure how far they can be held liable.

It may be that these locos will be due a further modification, possibly including the isolation or removal of the remote multiple-working equipment from their Nightstar days, leaving only those circuits necessary for Cally Sleeper operation on the 61 way connection.
 

jfowkes

Member
Joined
20 Jul 2017
Messages
363
I think you might be better placed to answer your own question than I, as I imagine that the answer lies in how far CAF and their contractors can be held liable for the problem. If the issue is with their own kit then clearly it's down to them, but if the problems are with the pre-existing (but now redundant…?) equipment installed in the Cl92s 25+ years ago then I'm not sure how far they can be held liable.
If the issue is a fundamental one with the Cl92s, that still leaves questions about the design of the Mk5 with regard to placement of the BPIC relative to the connector and the possibility of accidental operation, and the design of procedures to avoid/identify such an occurrence.

In my mind the question about whether it was possible to design around the 61-way connector issue is somewhat irrelevant, because you're going to need to disconnect/connect the loco from the carriages at some stage anyway, regardless of design. That risks accidentally operating the BPIC and that risk wasn't identified at design stage. The question is how "severe" that oversight was.
 

O L Leigh

Established Member
Joined
20 Jan 2006
Messages
4,346
Location
In the cab with the paper
Yes I agree that the 61 way connection is not entirely relevant to this incident, and I referenced this a few days ago. The only pertinence it has is that, under the old coupling and uncoupling procedures at least, the instruction was to plug this jumper in last after the brake test was done.

The RAIB report covers BPICs in sufficient detail that I don't think I need to keep adding to it. If there was any oversight it was in the lack of clarity as to precisely which standards applied but that work will be/has been carried out to bring them closer to compliance, as I mentioned above.
 

MotCO

Established Member
Joined
25 Aug 2014
Messages
1,341
I'm sure it would be lovely to have the flexibility to have a second live loco attached, but the Cally Sleeper is intended only to work with one loco at a time so any issues about attaching a second are really not that much of a worry.
Are there no instances where a second loco needs to be attached? E.g., where railhead conditions are so poor a second loco is required, or where a loco has failed and a Thunderbird has been added on to get the train moved.
 

O L Leigh

Established Member
Joined
20 Jan 2006
Messages
4,346
Location
In the cab with the paper
Are there no instances where a second loco needs to be attached? E.g., where railhead conditions are so poor a second loco is required, or where a loco has failed and a Thunderbird has been added on to get the train moved.
Not so much due to poor rail conditions, but in the event of a failure certainly. In fact there are already instances where the set has two locos attached to the train, such as ECS into Euston, but in those instances the second loco is "dead in train", as has already been discussed. The issue is not that there can't be a second loco attached to the train, but that it should not be connected to the 61 way connection.
 

doningtonphil

Member
Joined
18 Aug 2014
Messages
76
I can't see anything wrong with the BPIC itself (edit - since read the report in full - and yes, that's shambolic) but it could have been designed with sophistication. Coupler front faces can have inductive switches that detect a 'coupled' coupler and ICs can have microswitches, have a signal discrepancy between those and you can literally design alarm bells to ring! It's a safety critical system on a modern train after all...
The existing coupling cocks used throughout the UK rail network are designed like that for a reason. The vent hole that opens up when closed (which would have vented the locomotive brake pipe thus making it obvious there is an issue) is 'massive' on the standard cock. You would certainly have known about it if you had accidentally closed it, the compressor wouldn't have beaten it (especially as the air passes through a relatively small choke in the Driver's Brake Controller anyway) and it is orientated to be push down to open. All key design issues, designed for a reason, that were missed by fitting the cock they did.

The cause of the incident is that we are still using obsolete air brakes where an isolating valve can be closed without being easily detectable?

Or using items which don't match what is already fitted throughout the rail network - for good reason (see above)

If it's inherently safe and reliable how was closing a single valve able to so completely defeat the system with no apparent way for the train crew to tell this?

The placement of the valve was a problem, but the existance of a single valve that can potentially kill hundreds with very little that can be done to detect something wrong is something of a glaring safety issue.
By fitting equipment that isn't fit for purpose or designed to do the job it is supposed to be doing

That is the issue with rail vehicles being built by people from all over that don't understand why things are done the way they are done in the UK. I am fairly sure that a UK manufacturer wouldn't have thought of installing the right coupling cocks.

The report appears to state that the first passenger alarm was effective but that the 10s delay in brake application didn't provide confidence to the Train Manager that it had worked so he used a second alarm. This is another design failing - the alarm should have provided some positive indication to the user that it had been effective.

I'm sure there's a reason for the time delay but it's not immediately obvious to me why that would be.
I think the reason for the delay has been answered. However you have to remember the 'passcom' is more of a passenger convenience device. Back in the day the Guards Compartment would have had a great big meaty Emergency valve that would have 'stopped the train on a sixpence'.

One of the recommendations already mentioned.

And they also now using the Glasgow loco to split the trains, which makes the order simpler. You only need to go between the Edinburgh Loco and the Coaches once (I think)



There is mention in the report that they will change the valve to one with a bigger vent - this should make it more obivous in the cab that there is a problem.

(The compressor could keep up with the vent leak)

I wondered if the vent could be fitted with a whistle - so it goes with a bit more whoosh when opened. So you hear it.
If you accidentally close a standard red coupling cock which is still full of air, you WILL know about it (it's also pretty difficult to do!

There was mention of of the driver restricting his brake test because of the Rheo brake potentially waking the passengers. Apparently, back in the day, Sleepers were run with the Rheo isolated for just that very reason.

People have mentioned the fact that if the train brake had been applied during coupling then not of this would have happened. It has been mentioned to me that it takes a brave soul to go and lie down on the rails amongst a train being held on JUST the loco Straight Air Brake - which isn't fail safe!
 

Re 4/4

Member
Joined
30 Jun 2018
Messages
63
Location
Bristol
I have noticed in the past that all SBB stock, whether LHCS or MU, has a clearly visible brake status display.
We had an incident back in the early 2000s (I think) where a BPIC was left closed (among other things) on a works train and the driver and shunter got killed after they noticed it couldn't brake on a mountain downhill stretch. The best the signaller could do was route it into a buffer stop occupied by another works train.

Technically that movement was BLS not SBB I think though, but any safety learning would have been shared.
 

Clansman

Established Member
Joined
4 Jan 2016
Messages
2,152
Aberdeen depending upon which platform it is booked to use.
Usually used to be 6S to let the loco run around via 6N and 7S, and take the set out ECS from the front and reverse into Clayhills already in formation for the next service. Somehow there's been an increase in them using platform 4 and reversing out instead, since the Mk5s came in. Any reason for this?
 

BRX

Established Member
Joined
20 Oct 2008
Messages
2,528
I certainly agree with all the comments about procedural measures vs. designed-out measures - it's always preferable to design out the potential issue rather than mitigate it with procedural stuff.

And I see a pattern of generally poor design with these coaches, evident from all the non-safety critical problems with them.

One thing that seems strange to me is that it is necessary for anyone to get on the track at all (which inherently presents safety risks). I'd have thought that once you'd gone with Dellner couplers, then you'd try and make all the other stuff accessible from the platform side or the gangway end. Is there a particular reason that the ETS jumpers and the 61-way jumper could not be located higher up?

Maybe the answer is that the arrangement on the loco, where the Dellner has to be lifted into position, means that someone has to go onto the track to do that, and once that's a given, why bother trying to relocate the other stuff.

But the whole setup reeks of design compromise - the kind of thing where perhaps someone, at some point in the process, should have said, wait a minute, do we need to rethink this whole thing from the start? It's a familiar scenario to me, and one that often occurs when you have a lot of people involved in designing something, and also when it is being done in a rush. You start out with a basic concept that makes sense, and then when you work out the details you find that certain things don't actually work in line with the concept, and it gets compromised, eventually to the point where it just doesn't make sense any more. And at this point you should go back to the beginning and rethink the basic concept.

In this case I can see that the starting point was to use an automatic coupler to simplify operations. But the end result is, as far as I can see, no simplification to operations at all. I understand that this is because it was realised that the Dellner system could not cope with the large number of electrical connections needed. So was there a point at which the Dellner system could have been abandoned, and an alternative automatic coupling system used, one which could do all the electrical stuff too, which would avoid anyone having to go on the track and fiddle around in awkward positions? I don't know the answer to that, but I can imagine it's possible that there could have been a different system, but these realisations happened at a late stage in the process where people didn't want to delay things with a rethink.

@Bletchleyite is right - good design doesn't mean just following the specs in the brief but pointing out, at early stages, things that haven't been thought about, and suggesting changes to the spec if it allows an overall better design outcome.

Probably it isn't fair to blame things all on CAF - it appears that they were probably being briefed by an inexperienced 'customer' and that this must be part of the story.
 

jfowkes

Member
Joined
20 Jul 2017
Messages
363
Even if there was an autocoupling system that handled air, ETS, all the 61 way stuff and whatever else is required, I presume that would have needed a lot of work to interface it with the legacy kit on the Cl92, which itself adds risk and cost and a continued maintenance burden. At some point I guess it's easier to just get some people to do the things.
 

O L Leigh

Established Member
Joined
20 Jan 2006
Messages
4,346
Location
In the cab with the paper
I certainly agree with all the comments about procedural measures vs. designed-out measures - it's always preferable to design out the potential issue rather than mitigate it with procedural stuff.

And I see a pattern of generally poor design with these coaches, evident from all the non-safety critical problems with them.

One thing that seems strange to me is that it is necessary for anyone to get on the track at all (which inherently presents safety risks). I'd have thought that once you'd gone with Dellner couplers, then you'd try and make all the other stuff accessible from the platform side or the gangway end. Is there a particular reason that the ETS jumpers and the 61-way jumper could not be located higher up?

Maybe the answer is that the arrangement on the loco, where the Dellner has to be lifted into position, means that someone has to go onto the track to do that, and once that's a given, why bother trying to relocate the other stuff.

But the whole setup reeks of design compromise - the kind of thing where perhaps someone, at some point in the process, should have said, wait a minute, do we need to rethink this whole thing from the start? It's a familiar scenario to me, and one that often occurs when you have a lot of people involved in designing something, and also when it is being done in a rush. You start out with a basic concept that makes sense, and then when you work out the details you find that certain things don't actually work in line with the concept, and it gets compromised, eventually to the point where it just doesn't make sense any more. And at this point you should go back to the beginning and rethink the basic concept.

In this case I can see that the starting point was to use an automatic coupler to simplify operations. But the end result is, as far as I can see, no simplification to operations at all. I understand that this is because it was realised that the Dellner system could not cope with the large number of electrical connections needed. So was there a point at which the Dellner system could have been abandoned, and an alternative automatic coupling system used, one which could do all the electrical stuff too, which would avoid anyone having to go on the track and fiddle around in awkward positions? I don't know the answer to that, but I can imagine it's possible that there could have been a different system, but these realisations happened at a late stage in the process where people didn't want to delay things with a rethink.

@Bletchleyite is right - good design doesn't mean just following the specs in the brief but pointing out, at early stages, things that haven't been thought about, and suggesting changes to the spec if it allows an overall better design outcome.

Probably it isn't fair to blame things all on CAF - it appears that they were probably being briefed by an inexperienced 'customer' and that this must be part of the story.
I think that you infer rather a lot about the design and build process that none of us can actually know. Whether the design was rushed or subject to lack of planning or foresight is something that we shall never know.

However, these trains are not brand new standalone products that can be subject to entirely new standards. They have to be made to work within the current standards for things like ETS and braking, and as such there is only a certain amount of leeway the designer and customer can expect before their product starts to fall outside of the standards.

The issue with the auto-coupler is not so much the number of connections but rather the need for a fully automatic system to carry the ETS as well as any control or communication circuits. The electrical connector block that you see on the Delner couplers of MUs is not rated to carry that sort of voltage (RAIB Para 98). As such, there was always going to be a need for someone to go between the train and loco and plug these connections in. I would also question whether or not it is actually any safer to have raised the position of the jumper connectors. I know that the Southern had a particular safety concern that caused them to have their jumper connectors at windscreen height, but I would question if it's safer to have your shunter on the ground plugging stuff in or balanced on a stepboard.

It is certainly possible for locos to use fully automatic couplers. ROG have some Cl37s with various drophead auto-couplers that they use when moving EMUs around. It's not impossible that the Cally Sleeper could have taken a similar route. Clearly you would need to have some sort of electrically controlled pneumatic brake with a main air supply and an electrical brake continuity circuit, as staying with the two pipe system would still require operation of the BPICs at either end of the train in order to vent the brake pipe to secure the train and to carry out the brake continuity test.

The downside of such an arrangement is that suddenly this train becomes non-standard, which is the sort of thing that normally provokes howls of derision from the members of this forum who see interoperability as some sort of Holy Grail. At present the Cally Sleeper can be hauled by ANY loco by means of a coupler adapter, but using auto-couplers and an electrically controlled pneumatic brake means that you either have to have a compatible loco or a translator vehicle to go on each end. Given the issues discovered with the 61 way connector, it's probably a good thing they didn't take this route, as controls over how and when you go about plugging in a jumper is a good way of ensuring that two locos are not connected at the same time.
 

edwin_m

Veteran Member
Joined
21 Apr 2013
Messages
19,162
Location
Nottingham
I get the impression the original intention was to feed everything through the autocoupler but it turned out to be too difficult.

Putting the jumpers higher up would be incompatible with existing ETS jumpers so would need longer ones. And connecting either type of jumper unless there are platforms both sides would involve standing on a footstep and potentially falling in a trackside environment where there are various other hazards.
 

Nottingham59

Member
Joined
10 Dec 2019
Messages
61
Location
Nottingham
What I find odd about the RAIB report is that there is no further discussion of this point in para 62: "because the coaches were new, and the air systems were well sealed, there was virtually no leakage and the pressure remained at 5 bar throughout the journey, keeping the brakes released."

It seems to me that because the air systems were so well sealed, that the braking system was no longer fail-safe - in the sense that the coaches did not need to be pneumatically connected to the locomotive for the brakes to stay released. And yet that is the assumption behind the philosophy of the continuous brake pipe.

The simplest and most reliable way round this particular problem might be to introduce a some leakage via a tiny air vent in the brake pipe in every coach, so that if the pipe were not actively pressursed then the brakes would soon apply themselves. (I would make the vent adjustable, so that after a few years, when the air pipes started to leak anyway, the vent could be closed down so the whole braking system was not undermined by unnecessary leakage.)

Which leads me onto another question: is the any other stock on the system where the brake pipes are likely to be so well sealed that they are no longer fail-safe through the same mechanism?
 

Attachments

Tim_UK

Member
Joined
9 Jan 2019
Messages
76
The simplest and most reliable way round this particular problem might be to introduce a some leakage via a tiny air vent in the brake pipe in every coach, so that if the pipe were not actively pressursed then the brakes would soon apply themselves. (I would make the vent adjustable, so that after a few years, when the air pipes started to leak anyway, the vent could be closed down so the whole braking system was not undermined by unnecessary leakage.)
And there may be very simple way to do this.


Turn around the existing brake cock so the vent is on the train side of the valve.

So when the valve is shut, it leaks air out of the train pipe. Just a little bit. At the moment it leaks air out of the locomotive side. The RAIB report states that the locomotive compressor was easily able to keep up with the mini vent. So there will be a little bit of air leaking out of the back of the train, all the time.

But in the event that a train ends up with the valves shut on both ends, the air will leak of out the pipe (eventually).

Does that make sense?
 

edwin_m

Veteran Member
Joined
21 Apr 2013
Messages
19,162
Location
Nottingham
If the air pipes are leaky then if the train divides, the brakes will leak off more quickly on the part no longer connected to the loco. If this happens before crew can apply handbrakes or chocks then it is at risk of rolling away.
 

Top