How Do You Add/Remove Coaches To A Train With Jacobs Bogies?

[Envoy]

If a ‘normal’ train has a defective coach, it can easily be removed. So, what happens when the train has Jacobs bogies - that is, bogies that link 2 coaches?

 

[TRAX]

Jacobs bogies are found on multiple unit trains, and multiple units are fix-formed, meaning you can’t remove coaches with the snap of a hand as you would do with a loco-hauled train, for various reasons: multiple units have their equipment spread on the different cars, so if you remove a coach, some equipment will be missing or reduced (anything from transformers to a pantograph, motors, or a compressor...); multiple unit software is built to handle a certain amount of vehicles: if you remove one, the software doesn’t understand its train anymore and needs reprogramming; removing a coach significantly alters the train performance: if you lose traction performance it may not be seen as a major problem, but you’ll also lose braking performance (which won’t necessarily be offset by the lighter weight due to the removed coach) and this can be an issue, especially if you have removed a motor car, causing the loss of a significant amount of regenerative braking power. There are other reasons but these are the main ones.

Removing the defective coach of a multiple-unit is basically unheard of - a vehicle can’t fail completely and fall dead abruptly; in most cases there’s one or two failures but the vehicle can still run with the rest of the train. If that vehicle really can’t be used due to safety concerns, the whole train is declared a failure and brought back to the depot. The operator should have at least one spare unit in the fleet to cover the loss of that unit.
I don’t think you’ve ever seen a Class 444 running with only four coaches, or a Class 323 with only two, aye ?

 

[dk1]

Simply need to jack the train up.

 

[PeterC]

Jacobs bogies are found on multiple unit trains, and multiple units are fix-formed, meaning you can’t remove coaches with the snap of a hand as you would do with a loco-hauled train, for various reasons: multiple units have their equipment spread on the different cars, so if you remove a coach, some equipment will be missing or reduced (anything from transformers to a pantograph, motors, or a compressor...); multiple unit software is built to handle a certain amount of vehicles: if you remove one, the software doesn’t understand its train anymore and needs reprogramming; removing a coach significantly alters the train performance: if you lose traction performance it may not be seen as a major problem, but you’ll also lose braking performance (which won’t necessarily be offset by the lighter weight due to the removed coach) and this can be an issue, especially if you have removed a motor car, causing the loss of a significant amount of regenerative braking power. There are other reasons but these are the main ones.

Are you saying that such a unit is never split for maintenance?

 

[TRAX]

Are you saying that such a unit is never split for maintenance?

For maintenance, yes. For revenue service, no.
I’ve edited my initial message to add some elements, have a look.

 

[pdeaves]

Fundamentally, the part without the bogie is held on jacks.

 

[TRAX]

For the reasons I’ve stated above, you can’t put a shortened train in service while one of its cars is receiving attention at the depot, so the whole unit stays at the depot. So you may as well leave the defective coach attached to the rest of the train while you perform the maintenance.

 

[MacCookie]

For the reasons I’ve stated above, you can’t put a shortened train in service while one of its cars is receiving attention at the depot, so the whole unit stays at the depot. So you may as well leave the defective coach attached to the rest of the train while you perform the maintenance.

It depends on the unit. Class 170s can happily potter about with the middle vehicle removed, or with an additional middle vehicle added. It’s a fairly rare occurrence due to the time taken to split and reform, but not impossible.

Cheers,
Ewan

 

[dk1]

On the 4-car 755s only coach B can be removed as the rest all do something. The only other part that can be removed is the power pack making it just an emu. The 12-cars are basically two 6-car emus & will be jacked up as half trains for bogie removal only.

 

[TRAX]

And MUs are usually jacked up as a whole. It makes workers’ and softwares’ lives easier.

 

[TRAX]

It depends on the unit. Class 170s can happily potter about with the middle vehicle removed, or with an additional middle vehicle added. It’s a fairly rare occurrence due to the time taken to split and reform, but not impossible.

Cheers,
Ewan

Yes it depends on the type of train, but in most cases each car has one or several roles so it needs to stay there - this is also for software and TMS reasons.

 

[swt_passenger]

Fundamentally, the part without the bogie is held on jacks.

I expect there’ll be some sort of accommodation bogie available as well, that can be rolled in under the jacked vehicle.

 

[TRAX]

I expect there’ll be some sort of accommodation bogie available as well, that can be rolled in under the jacked vehicle.

There you go: Picture copyright Thierry Llansades via Flickr

 

[swt_passenger]

There you go: View attachment 70861Picture copyright Thierry Llansades via Flickr

Cheers, just as you’d expect then. Panic over...

 

[Envoy]

Many thanks for your replies - and especially TRAX for the detailed information.

 

[Islineclear3_1]

And: dependent on depot and unit type, whilst some carriages are jacked up - bogies can be "dropped" into an inspection pit

 

[TRAX]

Many thanks for your replies - and especially TRAX for the detailed information.

You’re very welcome.

 

[Clip]

It depends on the unit. Class 170s can happily potter about with the middle vehicle removed, or with an additional middle vehicle added. It’s a fairly rare occurrence due to the time taken to split and reform, but not impossible.

Cheers,
Ewan

Does a class 170 have Jacob bogies as per this thread?

 

[edwin_m]

It depends on the unit. Class 170s can happily potter about with the middle vehicle removed, or with an additional middle vehicle added. It’s a fairly rare occurrence due to the time taken to split and reform, but not impossible.

Cheers,
Ewan

And some 321s were converted into 320s by removing one car. I think that was allowed for in the original design by having the minimum of equipment on that car, and building 320s to the identical design by omitting it.

It's not unknown for MUs to be re-formed, for example if two collide in the depot the undamaged ends might be combined into one unit, and there have been various Voyager re-forms after fires or other damage as well as MML re-forming most of its 222s. There was even a 313 that ran as a 2-car back in BR days (not on AC routes though!). But I agree it doesn't happen on a day-by-day basis, and separating Jacobs bogies probably doesn't add very much to the work needed to re-configure and test the modified unit.

 

[grumpyoldman01]

Can anyone explain exactly what a Jacobs bogie is, please?

Gresley built hundreds of articulated coaches for the LNER (did he also build some GNR and ECJS articulated coaches as well?) and the LMS TSO-twins of the 1930s immediately come to mind as examples of loco-hauled articulated vehicles from times past here in Great Britain, but they were just described as being articulated; moreover, I can never recall ever hearing any SNCF or Alsthom guys with whom I worked in the late 1980s/early-mid 1990s ever using the term Jacobs bogies for TGVs. The first time I heard the term - pronounced as Yack-obs - was by some Atranz guys in the very late 1990s, but I'm afraid I can't remember which rolling stock was being discussed at the time.

So do Jacobs bogies differ from "other" articulated bogies in some way? Or is it now just a generic term (like vacuum cleaners are often called Hoovers, irrespective of manufacturer)?

 

[TRAX]

Can anyone explain exactly what a Jacobs bogie is, please?

Gresley built hundreds of articulated coaches for the LNER (did he also build some GNR and ECJS articulated coaches as well?) and the LMS TSO-twins of the 1930s immediately come to mind as examples of loco-hauled articulated vehicles from times past here in Great Britain, but they were just described as being articulated; moreover, I can never recall ever hearing any SNCF or Alsthom guys with whom I worked in the late 1980s/early-mid 1990s ever using the term Jacobs bogies for TGVs. The first time I heard the term - pronounced as Yack-obs - was by some Atranz guys in the very late 1990s, but I'm afraid I can't remember which rolling stock was being discussed at the time.

So do Jacobs bogies differ from "other" articulated bogies in some way? Or is it now just a generic term (like vacuum cleaners are often called Hoovers, irrespective of manufacturer)?

The Jacobs term designates any bogie designed to be fitted between two cars of an articulated unit, as they are by definition and by design different than standard bogies.
If this is what you’re wondering, the Jacobs bogie is not a unique, licensed, and patented design that several manufacturers can use (as is the case for the Scharfenberg coupler for example). Any bogie designed to be fitted in an articulated configuration corresponds to the Jacobs principle and so is called that way.

 

[xc170]

What is the benefit of using jacobs bogies over the normal two bogies per coach design?

 

[TRAX]

What is the benefit of using jacobs bogies over the normal two bogies per coach design?

It makes the train cheaper and lighter as there are less bogies, and it’s safer because it reduces to almost zero the chances of the cars jackknifing and folding into each other in the case of an accident/derailment - compare the aftermath of the non-articulated ICE 1 derailment at Eschede with that of the articulated Eurostar derailment in northern France.
One bogie also takes up less space inside the train, as each car would need to accommodate only half of a bogie instead of a full one.

 

[pdeaves]

It makes the train cheaper and lighter as there are less bogies, and it’s safer because it reduces to almost zero the chances of the cars jackknifing and folding into each other in the case of an accident/derailment - compare the aftermath of the non-articulated ICE 1 derailment at Eschede with that of the articulated Eurostar derailment in northern France.
One bogie also takes up less space inside the train, as each car would need to accommodate only half of a bogie instead of a full one.

I believe there is also less track wear, but not in a 'half the bogies is half the wear' way as there will be a commensurate higher axle loading.

 

[talltim]

And MUs are usually jacked up as a whole. It makes workers’ and softwares’ lives easier.

Unless you drop it...

 

[grumpyoldman01]

The Jacobs term designates any bogie designed to be fitted between two cars of an articulated unit, as they are by definition and by design different than standard bogies.
If this is what you’re wondering, the Jacobs bogie is not a unique, licensed, and patented design that several manufacturers can use (as is the case for the Scharfenberg coupler for example). Any bogie designed to be fitted in an articulated configuration corresponds to the Jacobs principle and so is called that way.

Thanks for that clarification - if I understand you correctly, Gresley's Quad Art sets would have been described as being fitted with Jacobs bogies if the term had been in common use when they were built and used.

As I said in my earlier post, the first time I recall hearing the term was about 20 years ago; can you say why Jacobs bogies suddenly became the norm for describing a bogie fitted between two cars of an articulated unit?

 

[TRAX]

Thanks for that clarification - if I understand you correctly, Gresley's Quad Art sets would have been described as being fitted with Jacobs bogies if the term had been in common use when they were built and used.

Absolutely.

As I said in my earlier post, the first time I recall hearing the term was about 20 years ago; can you say why Jacobs bogies suddenly became the norm for describing a bogie fitted between two cars of an articulated unit?

It is named after Wilhelm Jakobs, a railway engineer.

 

[edwin_m]

It makes the train cheaper and lighter as there are less bogies, and it’s safer because it reduces to almost zero the chances of the cars jackknifing and folding into each other in the case of an accident/derailment - compare the aftermath of the non-articulated ICE 1 derailment at Eschede with that of the articulated Eurostar derailment in northern France.

Not really comparable. The derailed coach at Eschede struck a bridge pier, bringing down the bridge, and the rest of the train piled up against it. A similar problem with an articulated train might well have allowed it to deviate far enough from the track to do the same. But if that pier hadn't been there (or had included the sort of collision mitigation measures used on high speed lines) then the ICE would probably have come to a halt relatively harmlessly like the Eurostar did.

One bogie also takes up less space inside the train, as each car would need to accommodate only half of a bogie instead of a full one.

However you don't save one less than half the bogies, because the sections of an articulated train will be shorter than the coaches of an otherwise similar conventional train. This is because the distance between the bogie pivots is limited by how much the body "throws" inwards on curves, and a conventional coach extends beyond the bogie pivots a lot further than an articulated one can. The articulated bogies themselves are probably longer, and therefore heavier, than conventional ones. ​