Why do so many trains have incompatible coupling systems?

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24Grange

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Why on earth were so many trains designed to have non-compatible couplings ( agreed not the reason for most of the delay in untangling the knitting). Do other railway systems across the world have the same issue - or is it just a byproduct of the way our privatisation worked?
 
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Mcr Warrior

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Why on earth were so many trains designed to have non-compatible couplings ( agreed not the reason for most of the delay in untangling the knitting).
Take it that a heavy duty tow-rope wouldn't suffice?! ;)

Tow rope.jpeg
 

Steve Harris

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Why on earth were so many trains designed to have non-compatible couplings ( agreed not the reason for most of the delay in untangling the knitting). Do other railway systems across the world have the same issue - or is it just a byproduct of the way our privatisation worked?
That's a good question, although under BR there were a few different couplings around (I'm looking at Pacers, 313's etc).
It would be a good idea to have a standard coupling. However, as you rightly point out , in this case, the knitting needed to be sortrd out to be able to move the train
 

Robertj21a

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Are couplers on all *new* stock now, finally, to a standard design ?

(I fear I know the answer)
 

LNW-GW Joint

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Why on earth were so many trains designed to have non-compatible couplings ( agreed not the reason for most of the delay in untangling the knitting). Do other railway systems across the world have the same issue - or is it just a byproduct of the way our privatisation worked?
My perception is that the GB railway is not completely standardised anyway, and then it is non-standard in global terms, or at least not in the main-stream.
That's things like platform height and curvature, and our relatively narrow gauge railway.
Manufacturers naturally want to produce vehicles which are not unique to any one market.
Couplers are also now high-tech devices, not just a physical way of joining trains as they once were, and standards have evolved rapidly in the last few decades as electronics has taken hold everywhere.
There's such a thing as TSI standards (Technical Standards for Interoperability) which were EU-wide and we still adhere to (and contributed to).
New trains conform to the most recent standards, or at least those that applied when the vehicle was certified, while the BR stock of the 1970s doesn't.
HS2 will give us another step-change in standards.
 

gimmea50anyday

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its not really the coupler that is the standard, its the electrical and electronic connections netween the trains that makes the compatibility.
Take for example SR 27 way cables. The actual coupling between units is standard buckeye. However, while most of the 400 series emus were compatible with each other and 73/1 and 33/1 they werent compatible with 73/0 which were wired to be compatible with the thumpers which used a different wiring setup although the plugs were the same! 455 use the same coupling principle, i.e MU jumpers at platform height avoiding shunters having to go on the track to connect and therefore avoid being near the juice rail, but the coupler is different, its a tightlock. (i think) now, they can theoretically couple to a 319 and electrically they should be the same, but 319s dont use platform height jumpers!

pendolino and voyagers are coupler compatible, one can rescue the other, however because the electrical systems are different along with the electronics, the train TMS etc they wont work in multiple, and this is a crucial why trains arent compatible. TMSs are different. meridians and voyagers use the same TMS, but because Virgin and Arriva have since specified their own unique differences to train running, the TMS will be programmed different to EMT/EMRs TMS thus rendering any software compatibility useless. Same with the desiro family. while the 350, 360, 450 and even 185 should theoretically couple and work in multiple, the differences in software on the TMS will mean the trains wont talk to each other. I believe such differences mean 350/2 cannot work with 350/4 although the /3 and /4 do and have worked together, Southern have the same issue within their fleets as there are issues with the 375, 377 and 379 fleets not talking to each other due to different TMS versions. So I understand things anyway, happy to be corrected if wrong.....

Its like going back to the humble class 47, the most non-standard of the standard type 4 locomotives in BRs fleet!
 

37057

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its not really the coupler that is the standard, its the electrical and electronic connections netween the trains that makes the compatibility.
Take for example SR 27 way cables. The actual coupling between units is standard buckeye. However, while most of the 400 series emus were compatible with each other and 73/1 and 33/1 they werent compatible with 73/0 which were wired to be compatible with the thumpers which used a different wiring setup although the plugs were the same! 455 use the same coupling principle, i.e MU jumpers at platform height avoiding shunters having to go on the track to connect and therefore avoid being near the juice rail, but the coupler is different, its a tightlock. (i think) now, they can theoretically couple to a 319 and electrically they should be the same, but 319s dont use platform height jumpers!

pendolino and voyagers are coupler compatible, one can rescue the other, however because the electrical systems are different along with the electronics, the train TMS etc they wont work in multiple, and this is a crucial why trains arent compatible. TMSs are different. meridians and voyagers use the same TMS, but because Virgin and Arriva have since specified their own unique differences to train running, the TMS will be programmed different to EMT/EMRs TMS thus rendering any software compatibility useless. Same with the desiro family. while the 350, 360, 450 and even 185 should theoretically couple and work in multiple, the differences in software on the TMS will mean the trains wont talk to each other. I believe such differences mean 350/2 cannot work with 350/4 although the /3 and /4 do and have worked together, Southern have the same issue within their fleets as there are issues with the 375, 377 and 379 fleets not talking to each other due to different TMS versions. So I understand things anyway, happy to be corrected if wrong.....

Its like going back to the humble class 47, the most non-standard of the standard type 4 locomotives in BRs fleet!

Another issue of coupler compatibility to consider... Even if every train in the country was electrically compatible, their construction may not be. Imagine if a 26 meter IET with its lengthy nose cone had a BSI coupler fitted (ignore electrical compatibility for now) and was attached to a 142 negotiating it's way around a depot - something is bound to foul somewhere!

That's obviously an extreme example but these things have their limits and often they may only be presented in certain conditions but my point is electrical compatibility isn't the only limiting factor. I guess BR designs followed similar trends, nowadays trains come in more extreme shapes and sizes, differing coupler lengths, distance between bogies and vehicle end, ride heights etc.
 

Taunton

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Take for example SR 27 way cables ... the same coupling principle, i.e MU jumpers at platform height avoiding shunters having to go on the track to connect and therefore avoid being near the juice rail
I often wondered how this worked, given that if a unit was connected from the platform, when it came to be disconnected it must have been a 50-50 chance that the platform was on the other side.
 

LSWR Cavalier

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Looks like a dichotomy between standardisation and improvement/progress.

I think it might be much better if things were standardised, only three systems? (Diesel, overhead electric, third-rail electric)
 

Robertj21a

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its not really the coupler that is the standard, its the electrical and electronic connections netween the trains that makes the compatibility.
Take for example SR 27 way cables. The actual coupling between units is standard buckeye. However, while most of the 400 series emus were compatible with each other and 73/1 and 33/1 they werent compatible with 73/0 which were wired to be compatible with the thumpers which used a different wiring setup although the plugs were the same! 455 use the same coupling principle, i.e MU jumpers at platform height avoiding shunters having to go on the track to connect and therefore avoid being near the juice rail, but the coupler is different, its a tightlock. (i think) now, they can theoretically couple to a 319 and electrically they should be the same, but 319s dont use platform height jumpers!

pendolino and voyagers are coupler compatible, one can rescue the other, however because the electrical systems are different along with the electronics, the train TMS etc they wont work in multiple, and this is a crucial why trains arent compatible. TMSs are different. meridians and voyagers use the same TMS, but because Virgin and Arriva have since specified their own unique differences to train running, the TMS will be programmed different to EMT/EMRs TMS thus rendering any software compatibility useless. Same with the desiro family. while the 350, 360, 450 and even 185 should theoretically couple and work in multiple, the differences in software on the TMS will mean the trains wont talk to each other. I believe such differences mean 350/2 cannot work with 350/4 although the /3 and /4 do and have worked together, Southern have the same issue within their fleets as there are issues with the 375, 377 and 379 fleets not talking to each other due to different TMS versions. So I understand things anyway, happy to be corrected if wrong.....

Its like going back to the humble class 47, the most non-standard of the standard type 4 locomotives in BRs fleet!
Very interesting, thanks for that.

I don't think I'll hold my breath for significant improvements!
 

AM9

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The fragmented design organisation in BR had many instances of the 'not invented here' mentality, often an unintentional legacy of pre-nationalisation rivalry. That has been perpetuated through some TOCs demanding that commercial manufacturers adhering to standards that relate to local practice even though some new stock only ever gets deployed in a single role.
The fact that the electronic systems aren't the same does not prevent the interfaces from being compatible. The aircraft industry has for years managed far more complex electrical interconnections in a far more aggressive environment that rail vehicle coupling, and they have been applied with a not very generous weight budget.
 

Domh245

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The fact that the electronic systems aren't the same does not prevent the interfaces from being compatible. The aircraft industry has for years managed far more complex electrical interconnections in a far more aggressive environment that rail vehicle coupling, and they have been applied with a not very generous weight budget.

I'm curious what those aircraft electrical interconnections are. I can't think of anything comparable to a rail vehicle coupling that is standardised or in an aggressive environment
 

edwin_m

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For train manufacturers there is a liability issue here. If new train B won't operate in multiple with existing train A then B's supplier will say it's because A doesn't exactly meet whatever spec they have been given. Unless there is a fully comprehensive loophole-free specification, and the customers insist on it, then this will continue to be a problem. It's probably getting worse too, as trains get more and more on-board systems that need to communicate through the couplers, and obviously older trains don't have any provision for the new ones.
 

Taunton

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I'm curious what those aircraft electrical interconnections are. I can't think of anything comparable to a rail vehicle coupling that is standardised or in an aggressive environment
Think of the Ground Power Unit that is towed out to supply electrical or compressed air power before the engines are started. All sorts of manufacturers of them around the world, and aircraft from all sorts of different aircraft builders and generations. But they all connect to everything. Just plug it in.

If you want a rail example, look at the USA AAR multiple-unit connection. Just about anything in the USA can be connected in multple, and driven from the front loco. Anything from a 1940s old switcher to a current all-electronic heavy haul one.
 

nlogax

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Whenever I see threads like this I'm ever more tempted to build a 'what couples / works with what' spreadsheet. However the research needed would probably take me years!
 

CBlue

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Think of the Ground Power Unit that is towed out to supply electrical or compressed air power before the engines are started. All sorts of manufacturers of them around the world, and aircraft from all sorts of different aircraft builders and generations. But they all connect to everything. Just plug it in.

If you want a rail example, look at the USA AAR multiple-unit connection. Just about anything in the USA can be connected in multple, and driven from the front loco. Anything from a 1940s old switcher to a current all-electronic heavy haul one.
I refer you to these comments regarding AAR from another thread:
How much of a list would you like;

It doesn't support voice communications.
It doesn't support any databus connections.
The implementations for 59, 66 and 67 are all slightly different.
It uses a connector that is not commonly available in the UK and has an exceedingly long lead time, with the cheap plastic versions for the housing only pushing four figures (that you can't even use out on the line).
It doesn't include some relatively sensible connections such as Brake Continuity for compatibility with other units.
It includes a "Control On" signal that is rather current limited and therefore limits the way that you can couple multiple locomotives together, and makes some very adventourous ill informed persons think it can do more than it actually can.

And I don't have my coupling standard to hand, but this is mainly off the cuff.

I've no inside/professional knowledge of the situation, but I suspect that this might be as far as it's got:

See https://en.wikipedia.org/wiki/Train_communication_network#Wire_train_bus

(The 'Chiltern' group of 68's - 68008 to 68015 - have AAR in addition, but that's primarily for compatibility with the DVTs - which had originally been equipped with AAR for use with the 67s...)

AFAIK, AAR 27 Wire control evolved from a propriety EMD system, which became a de-facto standard in North America due to the dominance of EMD in that market. Because it wasn't actually fully standardised, eventually the AAR got involved to try and make it so. Although you can in theory MU a 40 year old GP40 with brand new ET44AC, the differences in traction characteristics/wheelslip control between them wouldn't make it a particularly happy partnership, so you most often see the same 'generation' of locos used together in a consist to avoid that.

My interpretation is that like it or not, different stock won't talk to each other - and that it's nothing new. BR was running plenty of different stock around that couldn't talk to each other either.
 

swt_passenger

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I often wondered how this worked, given that if a unit was connected from the platform, when it came to be disconnected it must have been a 50-50 chance that the platform was on the other side.
The carriage working notices and a planned normal platform usage did try to avoid that, so sometimes a unit being coupled at a main terminus such as Waterloo would be listed to be connected on the “outside”.
 

Dunfanaghy Rd

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I often wondered how this worked, given that if a unit was connected from the platform, when it came to be disconnected it must have been a 50-50 chance that the platform was on the other side.
When I was at Southampton (many moons ago) when this happened it was a call to Eastleigh Panel, followed by a trip along the offside footboard to reach the jumper. I believe that Waterloo had permanent platforms for this eventuality.
Pat
 

swt_passenger

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When I was at Southampton (many moons ago) when this happened it was a call to Eastleigh Panel, followed by a trip along the offside footboard to reach the jumper. I believe that Waterloo had permanent platforms for this eventuality.
Pat
I remember they provided outboard platforms at Bournemouth for splitting and joining the 442s, only a short time before they were withdrawn…
 

nickw1

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its not really the coupler that is the standard, its the electrical and electronic connections netween the trains that makes the compatibility.
Take for example SR 27 way cables. The actual coupling between units is standard buckeye. However, while most of the 400 series emus were compatible with each other and 73/1 and 33/1 they werent compatible with 73/0 which were wired to be compatible with the thumpers which used a different wiring setup although the plugs were the same! 455 use the same coupling principle, i.e MU jumpers at platform height avoiding shunters having to go on the track to connect and therefore avoid being near the juice rail, but the coupler is different, its a tightlock. (i think) now, they can theoretically couple to a 319 and electrically they should be the same, but 319s dont use platform height jumpers!

It would have been interesting if 455s had been fully compatible with slam door units, we could then have seen things like VEP/455 lashups which would have had a quirky visual appeal. Potentially useful as well, as it would have allowed some first-class to be maintained on middle-distance commuter routes which saw EPBs (Cobham, Guildford stoppers, Alton, Reading, etc) while maximising seating - though at least some 455s would probably need toilets for this use. (That said, did EPBs have toilets? They - 2EPBs at least - went out as far as Alton for a time).
 

43096

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It would have been interesting if 455s had been fully compatible with slam door units, we could then have seen things like VEP/455 lashups which would have had a quirky visual appeal. Potentially useful as well,
Potentially useful? How about an operational and safety nightmare. How do you do door control from the VEP, including door interlock on the 455? That's before you get to different door close procedures and the risk of guards forgetting they had the other type of unit attached when dispatching.
 

swt_passenger

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Isn’t the “Schaku” or Dellner/Scharfenberg becoming the default mechanical coupling for new stock anyway? When RSSB did an explanatory paper about this around ten years ago, they basically saw the fleets dividing into existing regional DMUs all being BSI, and new EMUs and high speed DEMUs all going in the the Dellner/Scharfenberg direction.
 

Domh245

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Think of the Ground Power Unit that is towed out to supply electrical or compressed air power before the engines are started. All sorts of manufacturers of them around the world, and aircraft from all sorts of different aircraft builders and generations. But they all connect to everything. Just plug it in

Far as I can tell, there is a fairly standardised 3 pin arrangement for GPUs? That said, pure conductor (and pneumatic) connectors are a doddle with quasi-standard arrangements in many industries already, especially when you are happy to make the connections manually - especially when there's only a handful of inputs and outputs.

It's no comparison to a physical connector that has to automatically make/break tens of conductors, and maintain said connections over a range of movements. If all a trains coupler had to do was send 415v and air between units, it'd be fine - but they don't.

There's probably an argument that if we do standardise on a connector it should just send everything through one or two bus with a published communication protocol rather than using individual pins for everything.

Isn’t the “Schaku” or Dellner/Scharfenberg becoming the default mechanical coupling for new stock anyway? When RSSB did an explanatory paper about this around ten years ago, they basically saw the fleets dividing into existing regional DMUs all being BSI, and new EMUs and high speed DEMUs all going in the the Dellner/Scharfenberg direction.

It is a de-facto mechanical standard now (and pneumatic by merit of the connectors being in the coupler face rather than the box) though there's still some variance in terms of height I think?
 

swt_passenger

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It is a de-facto mechanical standard now (and pneumatic by merit of the connectors being in the coupler face rather than the box) though there's still some variance in terms of height I think?
Yes, height has been an issue as well hasn’t it, hence those various complicated thunderbird couplings. And guide horns that get in the way of electrical boxes…
 

nickw1

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Potentially useful? How about an operational and safety nightmare. How do you do door control from the VEP, including door interlock on the 455? That's before you get to different door close procedures and the risk of guards forgetting they had the other type of unit attached when dispatching.

I was talking about the theoretical case of 455s being compatible with VEPs and the like, in a parallel universe so to speak, rather than actually seriously suggesting that they should have been used together when it was already stated in the previous post that they were not compatible. Sorry if that was unclear.
 

skyhigh

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Yes, height has been an issue as well hasn’t it, hence those various complicated thunderbird couplings. And guide horns that get in the way of electrical boxes…
Different units definitely have them at different heights. The other issue is software of course- for example a 195 can rescue a 331 in an emergency, but the 331 has to be dead. If you can't get 2 units ordered at the same time from the same company for the same operator to be compatible, it's going to be an uphill struggle. Obviously it's a different situation in an emergency rescue to service work.
 

swt_passenger

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Different units definitely have them at different heights. The other issue is software of course- for example a 195 can rescue a 331 in an emergency, but the 331 has to be dead. If you can't get 2 units ordered at the same time from the same company for the same operator to be compatible, it's going to be an uphill struggle. Obviously it's a different situation in an emergency rescue to service work.
I’ve always assumed that software and wiring differences will continue. Being able to rescue a random unit by mechanical coupling is the only likely end result anyway.
 

Steven_G

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I would imagine that incompatibility is only an issue in rare circumstances.

How often do you need/want to mix stock?

I understand the issue from the perspective of breakdown recovery but not from timetabling
 

Taunton

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I’ve always assumed that software and wiring differences will continue. Being able to rescue a random unit by mechanical coupling is the only likely end result anyway.
But that is precisely where the major delays etc that make it into the media are happening, where one unit fails and is incapable of even emergency rescue just with coupling/air brake, by loco, other unit, or whatever.
 
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