Signalling and 140mph running

[captainbigun]

Anyway re the transformers I am aware they are interchangeable but if you check you will find that the original transformers used on the 86/1 was of the type being developed for the 87s. I do not recall the reason or the history beyond that - old age means some things like this get forgotten over time

Hmm, there's no paperwork or documentary evidence from BR or GEC to support this that I've seen. We have a lot of history on the locos eminating back to commisioning with BR. What I do know is that there were only 37 87 type transformers built. The additional two were a subsequent build. Not that they were changed much in the days pre-push/pull.

 

[Old Timer]

Hmm, there's no paperwork or documentary evidence from BR or GEC to support this that I've seen. We have a lot of history on the locos eminating back to commisioning with BR. What I do know is that there were only 37 87 type transformers built. The additional two were a subsequent build. Not that they were changed much in the days pre-push/pull.

Maybe the 86/1 transformers were moved into the 87 and the 86s had their original ones back ?

Now a question if I may be so bold ?

Does modern rolling stock work along the 1980s style brake TDM (Train wire 13), et al ?

And does it run through the brake controller in the rear cab still ?

 

[captainbigun]

Does modern rolling stock work along the 1980s style brake TDM (Train wire 13), et al ?

And does it run through the brake controller in the rear cab still ?

I can only speak up to 91s/Mk3/Mk4/DVT era. Beyond that your into the wonderful world of Pendos and other units. The modern Desiro/xxxStar etc families will use their own flavour of control, though the usual suspects (Knorr Bremse etc) will feature.

Something that is interesting, the new Siemens 380s use an all new control system communication bus. It's an industrial IP (technically speaking ethernet) derivative called PROFINET. So train wires has become, well, train wire (technically 8 of them I know!).

 

[Old Timer]

Thank you, Old Chap.

I am very grateful for the input.

 

[captainbigun]

Specifically on Pendos I'm told that there are 6 steps of braking, however in theory you could hold inter-notch and achieve proportional brake. The control is via PWM.

 

[Old Timer]

That explains why it FELT as if they had proportional brakes at times. !

 

[90019]

I've never really understood why they have notched braking on trains anyway. It seems a bit odd as it must surely limit how precise the braking can be?
I would've thought non-notched braking would make more sense as there would be more accurate control of the brakes?

 

[CarterUSM]

I've never really understood why they have notched braking on trains anyway. It seems a bit odd as it must surely limit how precise the braking can be?
I would've thought non-notched braking would make more sense as there would be more accurate control of the brakes?

That is something that has puzzled me also, never heard a satisfactory answer either.

 

[Pumbaa]

I was under the impression 390s had CBT - much like every other piece of modern stock manufactured by Alstom and Siemens? Bombardier have a standard piece of kit fitted throughout their products, with a three-step brake.

 

[Old Timer]

That is something that has puzzled me also, never heard a satisfactory answer either.

The answer as given to me back in the 1980s was that a three-step brake in addition to allowing OMO enabled a considerable saving to be made on brake pads.

Previously every Driver drove as they felt appropriate and the braking techniques ranged from light and gentle to hard and rapid. You could sometimes tell the Driver by the way the train handled.

Of course late and hard braking meant that brake pads wore out much quicker, and the brake discs were prone to cracking from being overheated.

Of course much of this also had to do with the need to introduce a coupling system that removed the need for a shunter, as well as the fact that sliding door stock brought with it the difficulty of interfacing the door interlocks into the train braking system, which was why some units only lost traction when the door interlock was lost.

So a combination of factors came together at about the same time. Moving from proportional systems to the three-step was quite a step (pardon the pun) as no longer would the Driver judge where to apply the brake, the technique now became one of selecting the appropriate marker point at which a Step 1 or 2 brake application would bring the train to a stop at the required place (signal or station).

The early units also did not have the ability to completely destroy the air. Step 3 was (if I recall correctly) a 60 psi application. Emergency did not destroy any more air it simply guaranteed that a Step 3 brake application was made by means of the train wires being short-circuited through the brake controller.

Of course another benefit that electronic braking brought about was the ability to operate single manned because there was no need for the Guard to prove the air brake by carrying out a brake continuity test unlike a conventional DMU/EMU following an attachment/detachment.

With the then Westcode systems, train wire 13 or 4 depending upon the stock was a continuous circuit running from the brake controller in the leading cab back to the brake controller in the rear cab and thence back to the leading cab. This "proved" train continuity, as well as proving that the brake controller was in the Off position. This replaced the previous vacuum or air brake pipe.

In an emergency the Guard could apply the train brake by moving the brake controller in the rear cab, thus breaking the continuity in the train wire.

LIke the previous braking systems, the communication cord was provided but unlike those previously, because it broke the train wire, it brought about a complete irreversible emergency brake application, why was in itself a big problem as the Driver could no longer control the stopping point of the train.

I believe that in later builds of rolling stock, the train wire or its modern equivalent is now also interlocked with the doors, and of course it no longer brings about an irreversible brake application, as far as I know

 

[CarterUSM]

The answer as given to me back in the 1980s was that a three-step brake in addition to allowing OMO enabled a considerable saving to be made on brake pads.

Previously every Driver drove as they felt appropriate and the braking techniques ranged from light and gentle to hard and rapid. You could sometimes tell the Driver by the way the train handled.

Of course late and hard braking meant that brake pads wore out much quicker, and the brake discs were prone to cracking from being overheated.

Of course much of this also had to do with the need to introduce a coupling system that removed the need for a shunter, as well as the fact that sliding door stock brought with it the difficulty of interfacing the door interlocks into the train braking system, which was why some units only lost traction when the door interlock was lost.

So a combination of factors came together at about the same time. Moving from proportional systems to the three-step was quite a step (pardon the pun) as no longer would the Driver judge where to apply the brake, the technique now became one of selecting the appropriate marker point at which a Step 1 or 2 brake application would bring the train to a stop at the required place (signal or station).

The early units also did not have the ability to completely destroy the air. Step 3 was (if I recall correctly) a 60 psi application. Emergency did not destroy any more air it simply guaranteed that a Step 3 brake application was made by means of the train wires being short-circuited through the brake controller.

Of course another benefit that electronic braking brought about was the ability to operate single manned because there was no need for the Guard to prove the air brake by carrying out a brake continuity test unlike a conventional DMU/EMU following an attachment/detachment.

With the then Westcode systems, train wire 13 or 4 depending upon the stock was a continuous circuit running from the brake controller in the leading cab back to the brake controller in the rear cab and thence back to the leading cab. This "proved" train continuity, as well as proving that the brake controller was in the Off position. This replaced the previous vacuum or air brake pipe.

In an emergency the Guard could apply the train brake by moving the brake controller in the rear cab, thus breaking the continuity in the train wire.

LIke the previous braking systems, the communication cord was provided but unlike those previously, because it broke the train wire, it brought about a complete irreversible emergency brake application, why was in itself a big problem as the Driver could no longer control the stopping point of the train.

I believe that in later builds of rolling stock, the train wire or its modern equivalent is now also interlocked with the doors, and of course it no longer brings about an irreversible brake application, as far as I know

That is the most informative answer i've had yet, and i thank you for it. Though i can still occasionally tell who is driving my train by their braking technique ! Anyway, sorry to add to the topic drift, and i admit to knowing nowt about running over 100mph anyway.

 

[TomBoyRacer]

That is the most informative answer i've had yet, and i thank you for it. Though i can still occasionally tell who is driving my train by their braking technique ! Anyway, sorry to add to the topic drift, and i admit to knowing nowt about running over 100mph anyway.

I remember reading in traction a year or so ago that one of the 87s had an 86 transformer - or was it the other way round...? I think i might have chucked the magazine now but it was an excellent article. I've always been fascinated by TDM. Perhaps this might be worth continuing on another thread but I always wanted to know what the various combinations where.

 

[Bill EWS]

I remember when BR used to talk about the costs involved for every 10 mph increase of the maximum line speed and while the HST's were designed to run up to 150mp the cost of updating the signaling and track work costs was quite prohibitive. I would think that +20% increase still stands and only becomes worthwhile when building a brand new line such as HST1 and 2.

I am very much for concentrating on increasing line speeds up to 125mph wherever possible to increase the performance of the present expresses. I have also mentioned previoulsy of the possibilty of having a reserve of power boost that would get trains to get up to 125 mph as quickly as possible. there is a terrible waste of space and time with the present railway that could be taken advantage of. However, HS2 will still be welcome and probably very neccessary in the near future.

 

[captainbigun]

I remember reading in traction a year or so ago that one of the 87s had an 86 transformer - or was it the other way round...? I think i might have chucked the magazine now but it was an excellent article. I've always been fascinated by TDM. Perhaps this might be worth continuing on another thread but I always wanted to know what the various combinations where.

Of the exported 87s at least 3, possibly more had 86 transformers. 3 87s (18, 27 and 31) carry transformers with faults, all will be cut. A further two spares also carried faults and were cut.

TDM best discussed elsewhere, it's a subject in its own right.

 

[E&W Lucas]

AFAIK, the only place in the UK with the "flashing greens" is Stoke Bank. That arrangement gives you the extra signal section to stop, which is pretty much what you would require for 140 vice 125 running (please see O L Eigh's post above).

There's a very good practical reason why this has never been attempted in service. Neither a 91 nor HST could attain 140 uphill with a full rake, and there's too much slower moving traffic about for it to be a realistic prospect downhill.

Considering that UK railways largely run on Victorian infrastructure, 125 is quite an achievement!

 

[Invincibles]

This is all quite interesting, and while it is a shame that there will never be fast running on the traditional infrastructure is it possible that a spare aspect will be put in to the building of new lines (particularly HS2 but maybe any Stafford by pass were that to happen) that would permit much faster running than was technically possible at the time the lines were built?

I am thinking a sort of "the next signal will be the aspect before the aspect before red so get down to a more traditional line speed" kind of thing. That would alleviate the need to do the full break within one section in most cases?

 

[ralphchadkirk]

I am thinking a sort of "the next signal will be the aspect before the aspect before red so get down to a more traditional line speed" kind of thing. That would alleviate the need to do the full break within one section in most cases?

So a double yellow then? In 4 aspect signalling that's the signal before the signal before the red.

 

[notadriver]

AFAIK, the only place in the UK with the "flashing greens" is Stoke Bank. That arrangement gives you the extra signal section to stop, which is pretty much what you would require for 140 vice 125 running (please see O L Eigh's post above).

There's a very good practical reason why this has never been attempted in service. Neither a 91 nor HST could attain 140 uphill with a full rake, and there's too much slower moving traffic about for it to be a realistic prospect downhill.

Considering that UK railways largely run on Victorian infrastructure, 125 is quite an achievement!

I would think a class 91 set would attain near 140 before climbing the bank. But as you say time savings would be minimal. I think Britain is the only country that allows trains to run above 100 mph without cab signalling or speed control.

 

[E&W Lucas]

I would think a class 91 set would attain near 140 before climbing the bank. But as you say time savings would be minimal. I think Britain is the only country that allows trains to run above 100 mph without cab signalling or speed control.

When 140 trials were carried out, it was with a 91 at each end of the set. All academic anyway. HMRI will not allow running at anything above 125, without in cab signaling.

 

[ainsworth74]

I am thinking a sort of "the next signal will be the aspect before the aspect before red so get down to a more traditional line speed" kind of thing.

You mean 4-aspect signalling as found in many places on the network already:

Signal Aspects

 

[Metroland]

Apart from the 7 second sighting distance rule we have with traditional signalling, the main issue in the UK is the traffic mix.

Even at 125mph, trains reach junctions very quickly. To cross a freight train on a level junction across a set of 125mph running lines the approaching HST needs to be some 10-15 miles away, else it will get checked.

In Europe there is much more grade separation.

You can of course run at 125mph on 2 and 3 aspect signalling. 3 aspect signalling is in place on the northern ECML and GWML, all cleared for 125mph. 2 aspect is in parts on the cross country network. So introducing extra aspects is only part of the equation and comes back to why you have 3 and 4 aspect signalling in the first place - which is overall capacity and traffic mix.

With more being squeezed out of the ECML, WCML and GWML, I'd be surprised if you ever see more than 125mph with the need to share tracks with slower freight, regional and commuter trains. It won't be until we get HS2 there will be a true high speed network.

 

[TGV]

AFAIK, the only place in the UK with the "flashing greens" is Stoke Bank.

They're in place for more than just that - a long section between Helpston and Grantham has/had it fitted.

 

[anonymous0101]

Apart from the 7 second sighting distance rule we have with traditional signalling, the main issue in the UK is the traffic mix.



You can of course run at 125mph on 2 and 3 aspect signalling. 3 aspect signalling is in place on the northern ECML and GWML, all cleared for 125mph. 2 aspect is in parts on the cross country network. So introducing extra aspects is only part of the equation and comes back to why you have 3 and 4 aspect signalling in the first place - which is overall capacity and traffic mix.

I don't know much about signalling but - are you sure 125 mph is permitted under 2 and 3 aspect signalling sections? AFAIK 125 mph sections are always 4 aspect signalled?

 

[Old Timer]

The type of MAS is not a factor, it is the maximum line speed that is the criteria which drives braking distance required and thus from that the signal spacing that will be needed.

A 125mph train can brake within the 100mph braking curve, which was the original requirement for trains to operate above 100mph.

Thus provided that the three aspect signals are spaced sufficiently to provide the requisite braking distance, then 125mph running is permitted.

The authorisation of maximum linespeed was transferred from the Permanent Way Engineer to the Signalling Engineer some years back.

 

[Metroland]

I don't know much about signalling but - are you sure 125 mph is permitted under 2 and 3 aspect signalling sections? AFAIK 125 mph sections are always 4 aspect signalled?

Yep, GMML west of Reading is mostly 3 aspect, with some 2 aspect signalling near box tunnel. The ECML is 3 aspect north of Newcastle.

110mph sections with 2 aspect signalling are Berks and Hants west of Castle Cary, Tackley - Yarnton lane between Banbury and Oxford, and around Church Fenton on the Leeds-York line.

There's also some 100mph line with semaphores, notably south of Stirling in Scotland, and some 100mph single track: the Highland main line and the Cotswold line, for example.

As Old Timer points out, long as you get at least a yellow before the red, you can go at the full 125mph.

 

[DaveNewcastle]

AFAIK, the only place in the UK with the "flashing greens" is Stoke Bank.

They're in place for more than just that - a long section between Helpston and Grantham has/had it fitted.

I think you're both referring to the same stretch, although only the northern few miles are actually the Bank as it climbs out of the West Glen Valley towards Stoke tunnel (and then down into Grantham).

 

[TGV]

I think you're both referring to the same stretch, although only the northern few miles are actually the Bank as it climbs out of the West Glen Valley towards Stoke tunnel (and then down into Grantham).

Yes, exactly - the Stoke Bank is only a short stretch of the Peterborough to Grantham section, but the flashing greens operate on most of that distance including the short stretch known as Stoke Bank.

 

[The Planner]

Even at 125mph, trains reach junctions very quickly. To cross a freight train on a level junction across a set of 125mph running lines the approaching HST needs to be some 10-15 miles away, else it will get checked.

Thats a hell of a junction margin !! Depends on the junction speed, distance between signals, double red protection, speed of the freight etc etc... its not as cut and dried as your example.

 

[notadriver]

Does anyone know if the recommended 50 percent braking rule applies to high speed trains, or do they have to brake harder?

 

[Old Timer]

does anyone know if the recommended 50 percent braking rule .....

? ? ? ?