Great Western Coffee Shop

Just picked up from the website...………...think I may just work from home tomorrow!!!


https://www.gwr.com/about-us/media-centre/news/2019/july/hot-weather-travel-advice

Hmmm, think I will take a pair of shorts for the journey home. My journey home on SWR's 455 trains is very sweaty. No air conditioning, all windows opened. In fact, no different from my old commute on the Thames / FGW turbos.

I am working from home tomorrow but only after a big battle with a very non sympathetic manager  ??? >:(

I hope no-one was planning a trip to or from Cardiff...……...all cancelled due to the sunny weather.....

07:15 London Paddington to Cardiff Central due 09:21

09:56 Cardiff Central to London Paddington due 12:00

10:56 Cardiff Central to London Paddington due 13:01

11:56 Cardiff Central to London Paddington due 14:07

12:15 London Paddington to Cardiff Central due 14:21

12:56 Cardiff Central to London Paddington due 15:02

13:15 London Paddington to Cardiff Central due 15:23

13:56 Cardiff Central to London Paddington due 16:02

14:15 London Paddington to Cardiff Central due 16:22

14:56 Cardiff Central to London Paddington due 17:02

15:15 London Paddington to Cardiff Central due 17:21

15:56 Cardiff Central to London Paddington due 18:04

16:15 London Paddington to Swansea due 19:23

16:56 Cardiff Central to London Paddington due 19:09

17:56 Cardiff Central to London Paddington due 20:05

18:14 London Paddington to Swansea due 21:20

Add to that the 10.15 and 11.15 Paddington to Cardiffs terminating at Bristol Parkway.

Surprised non of the Paddington - Bristols and vv not cancelled (yet).

Fair weather only railway, very poor.
And yes I know that record breaking heat is expected, but with a warming climate this really should have been foreseen.

And why so many half length IETs ? Looking at the number of cancelled trains there should be plenty of spare stock to run full length trains on every service that is still running.

Good point. Hopefully that will happen. Today of all days would not be good to have rammed 5 carriage trains. Could be dangerous in the event of a breakdown.

Interesting that all the "don't use the railways" warnings on the media, don't say or your car as it is likely tarmac will melt at that temperature.

At least two short forms out there ...



and let's take all those crowds who want a day at the seaside and ...

But this is severe weather, according to Journey Check!  ;D

They do say it is likely to be as warm as the Great Heatwave of a couple of weeks back.

Putting out dire warnings of the possible situation after noon, but not allowing people to bring forward their journeys to the morning by not waiving ticket restrictions at all is not as helpful as they could have been.

It is Summer - rails too hot;
Autumn        - leaves on the line;
Winter          - rails icy;
Spring          - any of the above.

I've done the Trans-Siberian in Winter and the Ghan in Summer and neither has any problem.   ::)

On some railways in Russia (I don't know which) the track is cut and rewelded between winter and summer to reset the neutral temperature - otherwise the temperature range is too large for CWR. I doubt NR would be keen on doing that.

If you are feeling sorry for those poor hard done-by rails left out on the sun all day, you might like to look at Constantin Ciobanu's PWayBlog website (https://pwayblog.com/). I was going to call him the Mad Romanian, but only because he is (1) Romanian, (2) a permanent way engineer, and (3) madly enthusiastic about his subject and about communicating it to anyone who will listen. In particular, if you though jointed track was simple and didn't pose any design issues about temperature variations, think again!

I've declared a hot weather suspension of my heavier gardening duties today with a redeployment of resources to ice cube production.

The Ghan takes 50 hrs to cover 1800  miles - hardly a blistering (pun intended) pace !
The Trans Siberian shows "8 days" to cover 5700 miles (bit glacial..............)
 ;) ;)

Well compared to the WCML, MML and ECML lines where little to nothing is running, the GWML appears to be coping well.

The major disruptions now are reported as OLE failures, with more than one case of broken wires and trackside fires - Peterborough, St Albans, West Hampstead, Birmingham (more than one), and perhaps some of the multiple issues on GA. That does sound like loss of tension due to heat expansion and the tensioner running out of travel (i.e. the weights hit the floor).

I don't think I have ever heard NR say that was a real issue here, while SNCF have always included it in their warnings about disruption in hot weather. The new OLE GWR have ought not to suffer that problem ... you'd hope. 

Our new OHLE is ugly, but very resilient!

In the case of drop weights, you can measure the drop, count the turns, and work out the temperature range for a given wire run length. For a Tensorex, it's not so obvious, but it still can only cope with a certain expansion length. Presumably that's enough for what was foreseen by the designers about ten years ago, plus a safety margin. The only other question is whether they were all set up right - I think that can be checked visually, though I don't have the details.

Yes, I saw a large strip of builder's plastic sheeting wrapped around catenary supports on line CDL1 into Paddington.  I see on OTT it is marked as shut between SN117 and SN94.  Would have caused a lot more disruption had it affected the 6 main running lines.  Still had huge delays at Reading with two down locals cancelled and the third nearly 20 minutes late.

[If/When] the UK is a tropical country, routinely with many days over 35 degrees C, then there will/should be investment to ensure complete running on those days without weather related stoppages.  But if it's just one day in a blue moon, is it sensible to invest /more pragramic to say "we'll run slower that day".

I've seen many historic pictures of snowploughs going through deep drifts on UK railways, and some spectacular overseas videos of current operations.   But these days, I can't think of where a snowplough is kept locally, waiting for use if need be. Occasionally frustrating such as March of last year where there was a lag of days getting (just) the TransWilts re-opened after bad weather, but it the big measure of things ...

Of course, the big measure might be that this becomes a routine type of weather ...

The S&D was in quite a mess in the winter of 1962/63 (when I was 10!) so I remember it well!

Something else I remember was that Bristol Corporation (as the City Council were called then) were seriously hauled over the coals about their lack of snow clearing equipment when that heavy snow struck on Boxing Day 1962. We had 10" of the stuff in our front garden and it more or less stayed there until March. As a result of the criticism the Corporation spent a huge amount of money investing in the latest state-of-the-art snowploughs and ancillary equipment.

It sat unused in their Albert Road depotfor 19 years and was finally scrapped in 1981.

Can you guess what happened in the winter of 1982?  ;D

I am a bit more forgiving of snow/ice induced chaos*, because a warming climate suggests that the problem will become steadily less serious as the years go past.

Heat related problems are much more important in my view, because without significant mitigation action, they will get worse and worse.
And whilst OHLE in the GWR area looks re-assuringly robust, this wont help if the wires expand and sag in hot weather. As more of the GWR network is eventually electrified we have large scale OHLE failures to look forward to.
Survival of the nice solid supports is little consolation if the wires attached thereto have fallen down.

Early on in the sorry IET saga, I expressed doubts as to the reliability of the units in hot weather. A supporter of the new DMUs felt that I was unduly negative over this and pointed out that reliable operation at, IIRC 32 degrees was an "essential requirement"
I speculated as to what happens at 40 degrees, this was said to needless speculation as it "wont get that hot" Well today we found out what happens at nearly 40 degrees (met office) and almost certainly well over 40 degrees at engine height, in a cutting, and with another unit alongside.
Over a dozen short formations DESPITE numerous cancellations that SHOULD have resulted in plenty of spare units.

*Thinking of the Lewisham debacle and the appalling conditions suffered by victims of the "keep them on the trains no matter what" policy, I feel that much more robust plans are needed for speedy rescue in such cases. Might never be needed for a COLD weather emergency, but will certainly be needed for the next HOT weather stranding.

It is important not to make knee-jerk reactions just because things go belly up on one occasion. That is why I posted the off-topic story about Bristol Corporation to illustrate the point - they wasted huge sums of money on a knee-jerk reaction and Bristol ratepayers may well still be paying off the loans now. I would certainly have been when I was a Bristol ratepayer in the 1970s.

If we are going to get 40 degree temperatures once every 40 years then nothing needs to be spent. Even if we get them once a year I doubt that the money needs to be spent. If we ever get then once a week during the summer then clearly the money ought to have been spent by now.

At the moment we simply don't know if we need to spend the money or not. At present we should be monitoring the situation, and spend the money if and when it clearly needs to be spent.

So, the all time temperature record wasn't beaten after all.

Global warming? Pah! :P

GWR have been not to shabby when it comes to communications today, however, LNER were much better than every TOC. At about 17:00 yesterday evening, they had lifted ticket restrictions for services today to be used on Friday, Saturday or Sunday services. They also said how they were certain they’d be unable to run a decent service in the afternoon and issued plenty of updates.

You have to remember that the tracks are about 10 degrees celsius hotter than the air temperature, and once the track hits 40 degrees it can cause second degree burns, hence why Network Rail we’re struggling to work on at Gloucester. I would like to talk NR engineers for working in these terrible conditions to return service to normal, on time.

Anyways, enjoying the lovely sound of rain through the window as it cools down and the worst of it is over.

I think I have fathomed out the real reason for the huge amount of metalwork for the OHLE. When they decide that Brunel's GWR no longer has the "capacity", they won't have to widen/relay the existing track - two new lines can just be laid above the existing track supported by the ironwork that is already there. Simples !

Anyone would think the IETs were the only trains to have any heat related problems today!  In reality they performed reasonably well, given recent issues with engine reliability, and suffered the same displacement issues due to speed restrictions as anything else on the GWR network - which it seems held up better than any other long distance route out of London on the second hottest day ever recorded.  I see a HST had to be evacuated near Peterborough.

Another textbook case of confirmation bias from Broadgage.  ;)

Not so much confirmation bias, as pointing out the failures of a newish and hugely expensive train that was touted as being so much better than previous trains.
Also another victory for my crystal ball which specifically forecast overheating, not based on any detailed analysis but on previous experience with other new DMUs in hot weather.

Hmmm, a reply that sounds to me like....{drum roll}....confirmation bias ;D

Don’t forget that HSTs we’re always suffering from high water temperature in exceptionally hot weather, especially before being re-engined.

Daily Telegraph this morning:

(https://i.postimg.cc/dQ2XSKR5/Matt.jpg) (https://postimages.org/)

I dare say after yesterday's disruption to trains heading North out of London there will be a few more working from home requests going in.

Former colleagues tell me they performed far from reasonably well, backed up by a lot of their personal Facebook posts.

Call them cynical, but apparently they tell me there were no diesel only restrictions, is it a coincidence that happens for the first time on the hottest days of the year?!

There were no diesel only restrictions for two days last week and none today either.

I did a quick calculation.  A 1000 metre solid copper cable would extend by 85cm if heated from -10 to +40 degC.  OK, so catenary is made of twisted strands, and is some sort of alloy, but I guess the extension would be of that order.  But then, the catenary is clamped at regular intervals - surely it must be able to slide through these to allow for expansion and contraction?

I also wondered whether the catenary and contact wire will stretch a bit over their lifetime - they're under considerable tension, after all.  Do the tensioners and weights need adjustment from time to time, and could that be part of the problem if they hit their end stops in very hot weather?   

Actually... how did the GWR overhead wiring cope with the heat?

Because it was designed to!

Specifically (and in answer to Adrian):

expansion coefficient of catenary wire: 18 ppm/K   (CuAg conductor wire is 17, so less demading)
maximum wire length (half run length)  750 m     (wire runs usually fixed at mid point)
Tensorex C+ travel                              1m   (there are ones with shorter travel, presumably for short runs)

therefore temperature range allowed for   74 K  which should cover (say) -20^o to +50^o

The Tensorexes (Tensorices?) have a helpful dial on the side to tell you where they are in their travel. There is a standard maintenance task to measure the wire temperature and check the dial. However, it isn't required unless something else has happened to mechanically upset the wire - so evidently stretching in service isn't an issue (i.e. too small to worry about).

A few observations from the sharp end (commuting on Thames Valley/North Downs) over the last two days-

1 - It does not seem to be the IETs that have failed but Turbos - two missing at peak evening period yesterday and today on the North Downs , with train problems blamed on Journey Check (OK - pinch of salt time)

2 - We knew in the morning that from 12 noon that a reduced speed service would be operating, so shouldn't GWR have an emergency fall back timetable they can implement and use on all information systems?

3 - Transport Focus are clearly best prepared - there was already a "how was it for you" questionnaire about hot weather problems in my Inbox when I got home this evening!

Following on from the wire expansion range of 74^oC = 1m, setup is based on a central temperature of 20^oC so should be -17^o to +57^o. In fact that's also stated as -18/+56 or even -20/+60; I guess no-one's really too worried about the couple of degrees at the extremes ... yet.

As to support and registration, the principles are:

Most runs have tensioners at both ends, and are anchored or at least restrained in the middle to define where the wires are along-track at that point. Elsewhere the wires define their own positions along-track depending on temperature, and the supports mustn't resist that.

The catenary wire is held vertically and horizontally at each support, and drapes in a catenary shape between them defined by the load (its weight and the contact wire etc.) and tension. Some systems do have pulleys or slides, but Series 1 uses (almost always) cantilever arms that swing horizontally. That provides support at a fixed height, and laterally at position that is fixed (can't be pushed sideways) but moves as the arm swings (due to wire expansion). Arms are 1 to 1.8 m long, and the along-track movement is +/- 0.5 m, so this swing could be +/- 30^o! There may be a rule that the longer arms are used near the ends of a run.

The conductor wire hangs from the catenary wire on droppers, which holds it level but allows a pantograph to lift it against a reasonably constant force due to the tension and weight of the conductor wire. Its horizontal position is defined by registration arms, which are clamped to it but free to move vertically and along-track. They pivot at a point on the cantilever arm even further out (usually) than the catenary clamp, but as the two wires expand by almost the same amount the conductor wire stays below the catenary wire.

Then again, perhaps it was?  ;)

https://www.bbc.co.uk/news/amp/uk-49132575

Following on again from the design temperature range of Series 1 being 74 K, I was wondering what it was in earlier OLE. I don't have technical data on that, but I did find this in BR.12034/16 (from Railways Archive), which was a summary of current practice in about 1988 (it isn't dated):

"...the equipment is automatically tensioned, usually by weights and pulleys, in order to maintain constant tension within +/-1.5% in the catenary and contact wire over a temperature range of 56^oC. For this temperature range, the maximum tension length into which the equipment can be divided is just under 2 km."

Assuming that does mean 56K, not 0-56^oC, it doesn't look a big enough number even for the observed climate leading up to 1988, when account is taken of direct sun heating of the wires. How big that effect is, for example compared to rails, is another thing I'v never seen information about. What I can say, however, is that if anyone (like your boss) suggests going out to paint the wires white - look very caefully at the PPE you are provided with.

More of a breeze a few metres above the ground, and not much effect of heat radiated from the ground - I reckon the wires would be significantly cooler than the rails on a sunny day.  Could try using chrome plating the wire to keep it even cooler?

Thanks for all the technical details to satisfy my curiosity - all very interesting!

The extra wind is certainly going to help remove local hot spots. But the ground radiation effect is the same (nearly) at any height - the greater distance being exactly compensated by the greater area of ground in any solid angle. And the ground is always there, of course, filling all the directions that are "down" rather than "up", plus those blocked by things.

What I think matters more for rails is ground reflection, for example from a light-coloured cutting side wall. There may be some reflection from shiny (well a bit bright anyway) new ballast too. That may be a bit less at OLE height.

There is another mitigation for the wires, that the length depends on the average temperature over the whole 700 m. For a rail, the equivalent length is far shorter - less than 200 m, at least in the short term. On the other hand, there is a minimum length of rail that can buckle.

The temperature record has now been confirmed.

Presumably the overhead wires are also heated a bit by resistance losses caused by the current flowing. This would be very variable according to amount of traffic, not a constant.

Regardless as to the details, it is well known that the wires expand in the heat, and means to compensate for this are readily available.
So what went wrong ? Was the temperature greater than the maximum planned for ? If so that sounds like a basic error in design or installation. The temperatures though reaching a new record were still only about 1 degree higher than those previously achieved. I would expect infrastructure to function correctly up to at least 5 degrees higher than the previous record.

Or were the multiple failures not due to simple expansion of the wires, but something else related to the heat.

A few more quick calculations.  Contact wire has cross-section of 120 mm2, copper has resistivity 1.7 x 10-8 so 1.4 mOhm per metre.
If a train is drawing 10000 kW at 25kV, that's a current of 400 A, which would cause heating of 23 W per metre.

Heat capacity will be about 400 J per K per m, so rate of heating would be roughly 1 degree every 20 seconds.

Of course, I've ignored the heat generated at the point the pantograph touches the contact wire.  I've no idea how to estimate that, though any heating effect must surely affect the pantograph more than the wire.  Do pantographs get hot?

Some people are never satisfied ... but here is the official reckoning of the maximum current capacity of Series 1 OLE (some of this will flow in the catenary wire, but not a lot as it's smaller and less conductive):
 

Ambient temperature 28o C Solar gain 980 W/m2 Wind speed 0.45 m/s (1 mph) Current 531 A Resulting wire temperature 56o C Notes:    That applies for a conductor wire at end-of-life wear - 25% gone (so presumably down to 90 mm2). The limit is for continuous current, and for 10 minutes or less it can be raised by 15%. Under those conditions the wire itself can cope with 964 A, reaching 80o C, if the run is short enough for expansion to be less than 1 m. If the wind is just a little higher - 3 m/s (6.7 mph) - at 30o C ambient, the current limit becomes 964 A. I don't think starting current is a big issue -  nothing like the headache it is for 1500 V DC OLE, anyway (think of a big goods loco in the south of France on a hot day, for example).