Great Western Coffee Shop

No, I'm not turning into a saddo with a kagool......

My very first W&S trip a year ago, the steward told me they could not pass through Birmingham New Street if the DVT was leading and the loco was on the back.

On Monday, after I gave up on the wifi and three wasnt working, I got chatting to someone who has an interest in railways.  We got diverted via new street (and stopped) due to cable theft at thame bridge.  I commented, oh we can do that cos the DVT is on the back........

So he went and clarified with the guard and apparently if the DVT is leading, it can go through new street but they have to alert the signaller first as it limits the platforms it can pass through since there is a danger of clipping.

No, as a lay person, trains and carriages are on tracks - they really have little control over what they do unless they derail.  So surely any point on the train is equally in danger of clipping a platform regardless of which end is leading.

My spatial reasoning has been challenged (which admittedly is not difficult) and I was wondering if the panel can enlighten me?

No, I'm stumped. Those DVTs used to work in and out of New Street all the time before they were replaced with Voyagers and Pendos. I wasn't aware they were restricted to particular platforms but maybe they were.

I really don't understand the one way good/other way bad thing though. I'd have thought that the DVT was either out of gauge for certain platforms (in which case no go) or it would be OK!

At the western side of New Street platforms 9-12 have some tight curves at the ends where the tracks converge on the tunnels, so I assume the clearance concerns are over there, hence the need to alert the signaller, even if it does seem a bit odd the restriction apparently applies one way but not the other. Certainly can never recall being on an InterCity or Virgin working with an 87/90+DVT set that strayed over to that part of the station, they always used the longest, straightest platforms in the centre and east of the station, as do the Pendolinos now.

Was reassured on Saturday while travelling to Manchester to see that the finest New Street traditions were being maintained, with a platform change announced at the exact moment our train was just pulling in on the adjacent island, so we were all trying to get down the stairs while those who had got off were coming up. Genius.

Makes sense, but still doesn't explain two things: (a) why a DVT will fit one way but not the other or (b) why W&S couldn't just be routed through on a connection that didn't involve the sharper curves. Am I right in thinking that there are centre roads at BHM that could be used for a train to run through without any risk of platform contact...?

The W&S workings that run via New Street in the normal course of things - remember FA's train was diverted - seem to be booked to use platform 6 or 8, I can't remember exactly which it was the last time I was using W&S.

I don't think the centre roads are passed for trains carrying passengers, they're really more sidings that happen to have access at both ends. Even if you could use them, they are often occupied by a 'hot spare' XC Voyager or an LM DMU or EMU also on standby. The W&S trains stand in a platform and are dispatched by the station staff even though the doors are kept locked.

Why on earth would a train need to be dispatched from a station where the doors are not opened? Seems like madness to me - how have so many 20th century operating rules/practices survived into the 21st century?

Yes it was - but I remember vividly being told by the crew a year ago they cannot pass through New street if the DVT is leading.  And some of their paths do pass through there when needed not just on diversions - they then go out to tame bridge!

So no one seems to have an answer......

Because it is possible for someone on the station to attempt to open a door.  Obviously the door would not open but it would be on the catch and when spotted further down the line would require an emergency stop and the door locking out of use until it could be checked to make sure nothing is wrong with it.  If the train is despatched from the platform then you can be sure all of the doors are properly closed.

If the train had all automatic doors then the despatch requirement would not be needed

what you said yourself was 
Hence what I said about the sharply curved sections of the western platforms, which I am sure, is the issue and explains why they have to tell the signaller if the DVT is at the front so the trains are sent up 1-8, which are straighter.


Which was what I mean by

The signallers know those are coming and they have a booked route though the station as a result, which would avoid any issue over what way round the train is and the places the clearances are too tight.

Doesn't answer the question as to why the clearences are too tight. I thought a DVT was basically a go anywhere vehicle.

Also empty stock trains if nor running DOO will be dispatched as usual by dispatch staff and guard, if no dispatch staff the guard will self dispatch, also if a train comes to a stand at a platform or part of a platform the guard will dispatch...this is relevant to HST/Loco hauled only where as super tm said there is a possibility of a door on the catch incident occouring

Clearly not. It's also pretty clear in which part of New Street there is likely to be a problem, hence why you have to alert the signalbox.

I have stumbled across a Network Rail document on route clearance of stock used in East Anglia and under the Mk3 heading, the DVTs are specifically excluded, see http://www.networkrail.co.uk/browse%20documents/baseline%20capability/gauge%20capability,%20route%20availability/anglia%20route/table%20d3_gauge%20capability_coaching%20stock_anglia%20route.pdf suggesting that they have to be separately passed. Perhaps not surprising when they are shorter than a standard Mk3 (61ft 9in v 75ft) and have different bogies, with fairly hefty yaw damping arrangements.

I understand this bit..............but.......

NO ONE HAS EXPLAINED 

why if the DVT is leading the signallers need to know but if its trailing, they don't!

Presumably because the bit that sticks out that they are worried about isn't sticking out at the awkward spots when the DVT is running the other way round, hence no clearance problem.

If I take a fixed cuboid and pass it along a fixed track with fixed curvature - then assuming the cuboid does not deform (and I would not want to be on a train where any bit deformed significantly) the same dimensions apply in each direction...............

Does not compute

Back to my original postulate

I suspect that the tolerance of track and wheels, with the addition of the need to splay somewhat on sharp curves where long wheelbased non-bogie vehicles are allowed, leads to some quite generous / sloppy motion at low speeds. A pulled vehicle with appropriate rail and wheel profiles will tend to centre, a pushed one has different forces so may go "to the side" somewhat, and all will be further influenced by the coupling type, braking forces, and whether the vehicle itself has equal break forces to those either side of it, or less or more brake effect. You then need to consider rail grinding at maintainaince time, and the gauge widening effects of running vehicles of certain types on certain curvatures; preseumably the effect of the rails would differ with "push" or "pull" and in one direction would probably put different wear on the track to the other - so the risk might be of track damage rather than / in addition to vehicles thumping the platform, or something on the other side.

It's too complex a subject for me to get my head round in the few minutes I have.  Here are some starters for those of you with more brainpower, more time, or more background knowledge of this sort of thing:

http://en.wikipedia.org/wiki/Standard_gauge
http://wapedia.mobi/en/Rail_gauge
http://www.freepatentsonline.com/4386469.html
http://www.encyclopedia.com/doc/1G1-15486422.html

As I read it, adding track and vehicle tolerances you have a "play" at rail / wheel level of about 40mm on straight (60 m.p.h.) track ... and that's before you even go on to consider any sponginess / rockyness in the joints. I remember how the Hastings units used to rock around, and I seem to recall they had rubber bushes as limiters. Then there are end of vehicle overhang issues and splaying on curves.

Thank you!

I do actually a lot of physical modelling - but I'm the classic academic - fail to apply it to real life issues - had I actually thought about it.........

I can now understand why ... after applying the grey matter to the issue