Articulation in the UK

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ChristopherJ

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Why is articulation not used more extensively in modern UK railway vehicles? It's almost now a standard design concept for European rail models. I would of thought manufacturers would be positive at the opportunity to reduce the RA of their products by the use of shared bogies.

Some examples of articulated rail vehicles in Europe;

Alstom AGV
Alstom Coradia
Alstom TGV
Bombardier AGC
Bombardier Spacium 3.O6
Stalder FLIRT
Siemens Desiro (not the UK model)

The only models of railway vehicles that I can think of that use articulation in the UK are the Class 373 TGV-TMST and the WIA car carrier wagons.



 
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317666

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Most modern UK Trams, and the DLR stock, are articulated. I'm a little surprised that the new London Underground S Stock or the Class 378s aren't articulated, as they have walk-through gangways.
 

anthony263

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I think Alstom proposed articulation for the new EMU they proposed for Thameslink but it was rejected by the DFT although I cant remember the reason given
 

HSTEd

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In the UK loading gauge the articulation causes all sorts of issues because the whole length of the vehicle is the pivot length between the bogies.
Additionally maximum axle loads in the UK are actually higher than many of the countries on the continent.

Perhaps we will see articulation if the AGV is used to derive the HS2 CC stock.
 

ChristopherJ

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Forgot to mention that previously the APT was also articulated!

Surely as well as the advantage of reduced distributed weight, the use of articulation also means lower maintenance costs? Two shared bogies must be cheaper to maintain than four independent bogies, yes?
 

fgwrich

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In the UK loading gauge the articulation causes all sorts of issues because the whole length of the vehicle is the pivot length between the bogies.
Additionally maximum axle loads in the UK are actually higher than many of the countries on the continent.

Perhaps we will see articulation if the AGV is used to derive the HS2 CC stock.
I think Alstom proposed articulation for the new EMU they proposed for Thameslink but it was rejected by the DFT although I cant remember the reason given
I think it was rejected, much to Alstoms supprise, because of the minimum / maximum axles loading issue, and for being just too radical to what the Dft wanted.
 

Liam

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I thought Class 378's were articulated? If they aren't articulated, what are they?
 

causton

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I thought Class 378's were articulated? If they aren't articulated, what are they?
They are... just not in the way the OP means!

If you look at the pictures upthread, you will see 2 carriages (or 2 wagons) share the same bogie (frame with the wheels on) - other than those most UK stock has 2 bogies on each carriage and then 2 bogies on the next one completely seperate, whereas with articulation the bogie connects the two carriages together*

*E&OE
 

Liam

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They are... just not in the way the OP means!

If you look at the pictures upthread, you will see 2 carriages (or 2 wagons) share the same bogie (frame with the wheels on) - other than those most UK stock has 2 bogies on each carriage and then 2 bogies on the next one completely seperate, whereas with articulation the bogie connects the two carriages together*

*E&OE
Ahhhhh... I see....:lol:

Doesn't this type of articulation restricts the length of the coaches? I mean in a normal coach the bogies are a little towards the centre of the carriage, so there is some 'cutting' on the inside of corners, and also some over swing on the out side of corners, whereas with articulated trains, the carriage is all cutting in on each corner.

I suppose that more of each coach is available for seating though.
 

jopsuk

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Surely bogie-sharing articulation increases axle weight? Still got the same weight of train, but have just over 50% of the axles.

the LNER was an early dabbler in it though- I think there's still a couple of "Quad Art" rakes in use on heritage railways?
 

sprinterguy

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the LNER was an early dabbler in it though- I think there's still a couple of "Quad Art" rakes in use on heritage railways?
Gresley was quite a big proponent of the use of articulated carriages as far as UK applications are concerned, with not just the "Quad-Art" and "Quint-art" suburban sets but also the articulated twins and triplets used on the Silver Jubilee and Coronation trainsets. There were a few other examples too.
--- old post above --- --- new post below ---
Ahhhhh... I see....:lol:

Doesn't this type of articulation restricts the length of the coaches? I mean in a normal coach the bogies are a little towards the centre of the carriage, so there is some 'cutting' on the inside of corners, and also some over swing on the out side of corners, whereas with articulated trains, the carriage is all cutting in on each corner.
Yep, the centre throw is increased for articulated vehicles. The carriages of the APT-P were 21.2 metres long, which is quite lengthy for an articulated vehicle even for European Intercity standards, while the Eurostars, which are designed around the standard TGV carriage length of 18.7 metres, had gauging problems on the tight curves around Newcastle as the distance between bogie pivot centres is over 2 metres greater than the 16 metres of a mark 3 carriage.
 

LNW-GW Joint

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I think it was rejected, much to Alstoms supprise, because of the minimum / maximum axles loading issue, and for being just too radical to what the Dft wanted.
As I recall the Network Rail model for measuring track forces penalises articulated vehicles and therefore running costs would have been higher.
I think this was the reason the Alstom bid was uncompetitive, rather than a DfT technical decision.
 

John55

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Articulation was quite popular in the UK in the late 30s as both the LMS and the LNER were building vehicles which were articulated.

The LNER built the high speed trains for the streamliners as well as the awful suburban quint and quad-arts.

The LMS built significant numbers of articulated twins for excursion use I think as well as the Royal Scot trains of 1940 (which for obvious reasons never entered service as such) and the 3 car DMU of 1938.

The LMS articulation for the Royal Scot train and the DMU was different to the early LMS and LNER design as the coach bodies were pivoted from a stretcher bar which rested on top of the bogie and stuck out beyond the bogie. This meant the coach body was supported in more or less conventional position and so the coach swept through a normal area without the need to use short coaches.

This form of articulation was almost used on the 1938 EMUs for the Wirral electrification but the design work was not finished in time.

I have read that one of the weaknesses of the APT, which used a system like the later LMS design, was the amplification effect of the long stretcher across and over the bogie ends. This lead to a poor ride and possibly added to the travel sickness problems which affected the initial use of the APT.
 

route:oxford

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Yep, the centre throw is increased for articulated vehicles. The carriages of the APT-P were 21.2 metres long, which is quite lengthy for an articulated vehicle even for European Intercity standards, while the Eurostars, which are designed around the standard TGV carriage length of 18.7 metres, had gauging problems on the tight curves around Newcastle as the distance between bogie pivot centres is over 2 metres greater than the 16 metres of a mark 3 carriage.
Ok, so how short would an articulated carriage, that was say 2.73m wide have to be in order that it could travel within the same gauge as a Mk3 coach?

Could the end coaches, perhaps, be longer?

So say, in a matched quad/triplet...

19m-17m-17m-19m or 19m-17m-19m
 

Yew

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It could be easier to guage a train that uses standard carriages, but with only one door and vestibule per carriage. Having internal doors between the saloon and the vestibule, and between the saloon and the corridor connection to the next vestibule. Porviding the space savings of articulation, but witout the need to have shorter carriages, higher axle loads, or expensive reguaging. If a wider corridor connection is needed,(for example for evacuating wheelchairs) then system similar to S stock could be used.
 

Schnellzug

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For a moment I thought this thread was about the Sex Pistols. :|
:roll:

Actually, yes, the LNER used this a lot, didn't they. There's a splendid Quad-Art set on the North Norfolk.
 

John55

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Ok, so how short would an articulated carriage, that was say 2.73m wide have to be in order that it could travel within the same gauge as a Mk3 coach?

Could the end coaches, perhaps, be longer?

So say, in a matched quad/triplet...

19m-17m-17m-19m or 19m-17m-19m
That would depend on the form of articulation used. But as a guide the 373 intermediate cars are 18.7m long.
 

142094

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Tyne and Wear Metro does it quite successfully, although it is a shame the line where you can see it at its best is not for revenue service.
 

TGV

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Very few maintenance facilities have the ability to lift an entire unit, only a single vehicle at a time. Therefore there are maintenance issues beyond those of cost.

O L Leigh
Not as big an issue as you think. We do maintenance on TGVs and rarely lift them. In fact, most of the depots don't have a lift, they are bogie-dropped instead.

The main advantages of articulation are:

- Improved stability especially at very high speeds
- A much more rigid formation which is advantagous in case of a derailment. Compare any TGV derailment to Grayrigg, Ufton or many others and you can see the difference. The TGVs remain upright and inline with the occasional exception of the power cars which have conventional couplers and bogies.
- Lower noise inside the passenger compartment as no seats are over the bogie and indeed the whole articulation structure is above vestibules or toilets.
- Fewer axles and wheelsets to maintain.

Disadvantages:
- For all intents and purposes the sets are permanently connected. You *can* take a trailer out of the set, but it is a mammoth job. So not much flexibility - if one trailer has a major fault, the whole set is stood down. *EDIT: which may be what O L Leigh was referring to above?*
- Gauging as has already been mentioned - the centre throw is usually quite large given the long pivot centre dimension.
 
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HSTEd

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Would the power cars be stood down as well or can they be moved around? (if one set has a trailer fault and another set has power car faults, would they be swapped)
 

The Snap

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Very few maintenance facilities have the ability to lift an entire unit, only a single vehicle at a time. Therefore there are maintenance issues beyond those of cost.

O L Leigh
Other than Longsight, where else in the UK has this facility?
 

talltim

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TGV power cars are actually coupled to the sets by conventional screw coupling and use buffers. I was amazed when I found out
 

jopsuk

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doesn't Northam (Siemens/SWT) have a full-unit lift facility? Or possibly Eastleigh? I'd be surprised if the Crossrail, Thameslink and IEP new depots don't get them as well.
 

Class377/5

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doesn't Northam (Siemens/SWT) have a full-unit lift facility? Or possibly Eastleigh? I'd be surprised if the Crossrail, Thameslink and IEP new depots don't get them as well.
Thameslink deports require them as trains won't be spilt up very often during their working lives.
 

O L Leigh

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Disadvantages:
- For all intents and purposes the sets are permanently connected. You *can* take a trailer out of the set, but it is a mammoth job. So not much flexibility - if one trailer has a major fault, the whole set is stood down. *EDIT: which may be what O L Leigh was referring to above?*
Not quite, no. But it is an issue obviously.

The other thing linked to the centre-throw issue is that to provide a train of equivalent length of a 4 car unit using articulation may require the train to be 5 or possibly even 6 cars in length. The subsequent saving in bogies and wheelsets is therefore reduced and perhaps without any additional increase in interior capacity (UK platform heights do not permit low-floor alternatives).

I can see the argument for articulation on high-speed trains such as the TGV, but for regular MU services the advantages are not so pronounced. The additional stability that it offers isn't really going to be noticeable at UK linespeeds. Likewise the safety argument is not particularly pressing. The idea is that we don't fall off the road or bump into each other, and the number and severity of incidents proves that.

BTW, Clacton depot has the facility to lift an entire 4 car EMU.

O L Leigh
 

LE Greys

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One of the first LNER experiments, the restaurant triplets that ran in the Flying Soctsman, were definitely shorter than the convenional coaches. I once tried modelling them (never got beyond drawings) and it turned out that the distance between pivots was the same as on conventional Gresley coaches, so effectively the ends had been cut off. It's very nocieable on photographs. Gresley used the reduced end-throw as a means to widen the gangways, making it easier to get food from the kitchen seciton in the middle to diners at either end.
 

ChristopherJ

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TGV power cars are actually coupled to the sets by conventional screw coupling and use buffers. I was amazed when I found out
That must be the business end of either a 1st generation TGV-PSE or 2nd generation TGV-Atlantique.

Eurostars of the third generation (TGV-TMST) use a Sharfenberg coupler on the inner of the power cars, as shown in the photo below.

http://www.railwayscene.co.uk/fetchimage.php?imgref=1436

Not want to go OT but whilst searching for that photo I came across this image - a TGV power car hauling a freight wagon! Must be coupled using the screw coupling you have mentioned... Judging by the matching livery it may be an adapter/match wagon?

http://images-00.delcampe-static.net/img_large/auction/000/147/615/662_001.jpg
 
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