[HN Gopher] Why rails buckle in Britain
___________________________________________________________________
Why rails buckle in Britain
Author : scrlk
Score : 188 points
Date : 2022-07-16 15:04 UTC (7 hours ago)
(HTM) web link (www.networkrail.co.uk)
(TXT) w3m dump (www.networkrail.co.uk)
| zabzonk wrote:
| I don't see how this really explains anything. I have never
| understood how continuously-welded rails work compared with the
| old-style track using short rails and fishplates joining them,
| and this link doesnt help (for me at least).
| adrian_b wrote:
| It seems that the answer to your question is that the
| continuously-welded rails work only within a relatively narrow
| temperature range.
|
| As mentioned at this link, the continuously-welded rails are
| made to be stress free at a specified temperature, for example
| 27 degrees Celsius in UK.
|
| At lower temperatures the rails contract, which does not have
| bad consequences unless the temperature becomes so low that the
| rails will crack, because their strength has been exceeded by
| the contraction stress. At very low temperatures the trains may
| need to reduce their speed, so that the rails will not crack
| due to the additional stresses caused by a passing train.
|
| At higher temperatures, the rails dilate, and when the
| temperature is high enough they will buckle. Due to that, the
| trains may need to reduce the speed, or even stop and wait for
| the rails to become colder.
|
| At least a part of the rails from Germany have also been
| updated with continuously-welded rails.
|
| In one of my trips, it was a hot summer day and because of the
| rail buckling all the trains had huge delays. Even if I should
| have arrived at the Frankfurt airport about 3 hours before my
| flight, due to the train delays caused by the hot weather, I
| have arrived so late that I have lost the flight.
| konschubert wrote:
| Steel is a bit like rubber if your holding it with enough
| force...
| dazc wrote:
| Considering this is Network Rail, I agree, the opportunity to
| answer a lot of obvious questions has been seriously
| overlooked.
| scrlk wrote:
| I found this article and associated video, along with the
| Wikipedia article to be useful for filling in the gaps from the
| article:
|
| https://broadwayextensionblog.blogspot.com/2017/03/stressing...
|
| https://www.youtube.com/watch?v=I8EZ6pEAyLc
|
| https://en.wikipedia.org/wiki/Rail_stressing
| bombcar wrote:
| http://vinchad.blogspot.com/2014/06/ever-wondered-why-contin...
|
| > Its laid it's in tension by hydraulically stretching it
| before cutting to length and welding to the previous length.
| Sufficient tension is applied to achieve a 'Stress Free
| Temperature' (SFT) of 27 degrees C (i.e to relieve the tension
| by expansion the rail would need to be heated by the sun to
| 27C, whereupon it would neither be in tension or compression).
|
| Apparently they lay it "hot" and so normally when it is cooler
| than that it is actually "pulling" on itself trying to shrink,
| and when it gets hotter than that it begins to compress.
|
| If it can't compress it buckles, if it can't shrink then the
| tension grows, but steel has incredible tensile strength.
| ssl232 wrote:
| I wonder if you can combine rail sections with different
| zero-stress temperatures to cancel out across a wider range?
| Gare wrote:
| The tension is between each pair of sleepers (60 cm
| distance), how would that work?
| robocat wrote:
| Here's a link showing the tensioning process using a petrol
| powered hydraulic cylinder: https://broadwayextensionblog.blo
| gspot.com/2017/03/stressing...
| gattilorenz wrote:
| It mentions the pre-stressing, but a better explanation is at
| https://worldwiderails.com/how-do-railroads-deal-with-therma...
|
| It also explains some of the maintenance procedures.
| robocat wrote:
| This article shows mechanical tensioning using a hydraulic
| cylinder: https://broadwayextensionblog.blogspot.com/2017/03/
| stressing... although it is clearly a straight section. Do
| curved sections of rail just expand and contract?
|
| The parent link says "Railroads deal with thermal expansion
| by heating the rail prior to installation".
|
| reddit/etmidust wrote "I was a manager of track maintenance
| for a US railroad for a while. When they lay new rail, part
| of the process is a 'heater car'[1]. This machine rides the
| rail and is basically a multi headed blow torch to heat the
| new rail to the 'rail neutral temperature'(SFT). At this
| point the rail is not yet spiked down to the ties so that it
| has a chance to grow and expand. After the heater car some
| other rail cars called spikers follow to spike the new rail
| down. That is how they 'pre-stress' the rail. I am skipping
| some steps, but that is the gist of it."
|
| [1] https://imgur.io/tvCy9C2
| aaaaaaaaaaab wrote:
| https://en.m.wikipedia.org/wiki/Rail_stressing
| smcl wrote:
| Pasting a couple of @GarethDennis tweets which answer this:
|
| It is worth pointing out that jointed rather than welded track
| WILL NOT solve the buckling problem.
|
| In fact, jointed track is at a MUCH HIGHER risk of buckling in
| heat than welded rails as gaps close and there are 160+ joints
| PER MILE to maintain...
|
| ...plus jointed track is generally lighter, weaker and thus at
| higher risk of buckling (most GB buckles are in jointed, not
| welded track).
|
| Bolted joints also have a nasty habit of disintegrating under
| traffic and derailing trains (hence use of welded track to
| start with)
| adrian_b wrote:
| Your arguments make sense, so it appears that continuously-
| welded rails should be better than the traditional jointed
| rails.
|
| Nevertheless, when I was young I traveled frequently by
| train. During some decades, I have never seen problems caused
| to the train traffic by too high temperatures, on traditional
| jointed rails.
|
| On the other hand, in the last few years, whenever I happened
| to travel by train through Germany on continuously-welded
| rails and the weather was hot, there were train delays due to
| the rails.
|
| So it seems that there is some disconnection between theory
| and practice. Maybe the new continuously-welded rails have
| been designed based on ancient recorded temperature ranges
| that are no longer valid due to climate changes, as already
| suggested in the parent article, but in any case something is
| wrong with the design of modern rails.
|
| In the parent article it is mentioned that changing the
| stress-free temperature to a higher value is not good enough,
| because the strength of the rails could be exceeded during
| cold winters. So it is likely that the rails would have to
| also be thicker, increasing their cost.
| mook wrote:
| I don't know anything about German weather, but according
| to a random article on Wikipedia: https://en.m.wikipedia.or
| g/wiki/List_of_extreme_temperatures... says 9 of 16 extreme
| maximums are within the last year (with one about a month
| over).
| vladvasiliu wrote:
| > In fact, jointed track is at a MUCH HIGHER risk of buckling
| in heat than welded rails as gaps close and there are 160+
| joints PER MILE to maintain...
|
| Why? Don't the gaps give the track some amount of play which
| would lower the pressure and therefore the risk of buckling?
| mannykannot wrote:
| I don't have a reliable source, but I recall hearing that
| expansion gaps require the rails to have some freedom to
| slide back-and-forth, as the expansion and contraction
| occurs over the whole length. The rails are not guaranteed
| to go back to where they started when they cool down, so
| gaps can close up (while correspondingly widening elsewhere
| to compensate), and if you have too many closed gaps in a
| row, the rails can jam.
| jaclaz wrote:
| I believe you were misinformed.
|
| The rails have not a real freedom to slide, they have two
| different forms of resistance, the one provided by the
| ties and the one provided by the junction, there is only
| a given temperature range where they can slide.
|
| The rail goes into a cycle, you need some 3-4 Cdeg to win
| the resistance of the joint (in this part the rail is
| compressed by some 6000 kg of resistance) and some 6-7
| degrees more to win the resistance of the ties (some
| 10-12000 kg more of compression), then it becomes "free
| sliding" until the gap in the joint closes, this needs
| 12-13 Cdeg more and the rail is again compressed by the
| ends.
|
| When the temperatures lowers, the same cycle is reversed,
| the rail first contracts until the gap starts to appear
| and widens, then you have again a range where it is free
| sliding, then the two resistances come into play again,
| when the temperature lowers further the excursion is
| limited by the joints (usually they allow 14 mm travel)
| and the rail is subject to traction (as opposed to
| compression).
|
| The only point that never moves is the tie at the center
| of the rail length, you have to imagine a spring that you
| try to expand by pulling the two sides, it will return to
| its original shape, all forces are relative to the
| center, so there is not any reason why the rail should
| not come back to its original position.
|
| Check this:
|
| https://pwayblog.com/2017/03/06/jointed-track-response-
| to-ra...
|
| In practice - strangely enough - rails behave very
| similar to the theory.
| WalterBright wrote:
| The center of each section of rail could be bolted to the
| ties with non-sliding holes.
| makomk wrote:
| The gaps do give some amount of play. The trouble is that
| once the temperature exceeds the design maximum the gaps
| close up completely and all that expansion force is
| directed into hard metal-on-metal contact, at which point
| something has to give. Jointed rail tracks are not designed
| to handle those forces without buckling because the whole
| point of having the joints is so that they don't have to.
| webmobdev wrote:
| How do engineers plan for thermal expansion when laying
| traintracks in deserts where the daytime and nighttime
| temperatures are vastly different? -
| https://old.reddit.com/r/askscience/comments/8yxd21/how_do_e...
| Linda703 wrote:
| lordnacho wrote:
| I wonder if it's the same buckling we mean when we're studying
| structural engineering:
|
| https://en.wikipedia.org/wiki/Buckling
|
| The interesting thing here is that when something buckles, it's
| not the material failing like when you crush a cake. It can
| buckle well before you reach the force needed to break the steel
| under compression.
| philo23 wrote:
| Definitely the same kind of buckling. Here's an example from a
| couple of years ago in the news https://www.bbc.co.uk/news/uk-
| england-cumbria-44658254
|
| Check Google images for some more extreme examples.
| lostlogin wrote:
| Interesting - that looks like wooden sleepers too.
| bambax wrote:
| > _More than three-quarters of track on the network today is
| modern on concrete sleepers._
|
| "modern"? or "mounted"?
| mrob wrote:
| Looks to me that they forgot a comma. It probably should be
| "modern, on concrete sleepers."
| mnd999 wrote:
| Both, I think their point is that they've got rid of most of
| the wooden sleepers and replaced them with 'modern' concrete.
|
| Unfortunately, 'modern' is a pretty meaningless word and tells
| us nothing as to the why of this.
| penguin_booze wrote:
| Ha! The other day, I was having a short chat with a fellow
| commuter on this very topic (including 'why not in other
| countries?'), in the context of the expected heat wave on Monday
| and Tuesday. And the reason, I speculated, was exactly same as
| mentioned in the article. I'm glad I wasn't wrong. I'll share
| this article if I see them again.
| N_A_T_E wrote:
| Sounds like someone needs to invent some sort of expansion joint.
| I assume its a hard engineering problem with significant trade
| offs.
| Ekaros wrote:
| There is probably one, but the design was done for temperature
| range outside the current conditions. You can accommodate only
| for so much and at some point it make sense to say yeah, this
| temperature is good enough. There is very likely some trade-
| offs involved as well.
| chrisseaton wrote:
| > Sounds like someone needs to invent some sort of expansion
| joint.
|
| As the article says, there basically isn't the money or will to
| fix the problem, so they're leaving it as is.
| iggldiggl wrote:
| Such things exist
| (https://en.wikipedia.org/wiki/Breather_switch), but so far
| they've been mostly only used for localised
| expansion/contraction/movement hotspots, i.e. bridges longer
| that 50 - 100 m or so.
| jameshart wrote:
| Missing context for international readers who perhaps may not be
| aware of the weather forecast for the UK next week:
|
| "England braces for 40C temperatures as experts warn thousands
| could die" - https://www.theguardian.com/uk-
| news/2022/jul/15/heat-emergen...
| dcomp wrote:
| And for further context its the first RED (danger to life)
| warning [0] (for the purposes of heat, other red warning have
| been issued [1])
|
| [0] https://www.metoffice.gov.uk/about-us/press-
| office/news/weat... [1]
| https://www.metoffice.gov.uk/weather/learn-about/past-uk-wea...
| krona wrote:
| Most of the danger to life is people drowning in lakes,
| rivers etc.
| jameshart wrote:
| British people are not normally found in lakes or rivers.
| If they are being driven into those dangerous environments
| by the weather, perhaps the weather could be considered
| dangerous.
| bombcar wrote:
| According to the Romans it's common to find them there:
|
| > Their form of rule is democratic for the most part, and
| they are very fond of plundering; consequently they
| choose their boldest men as rulers....They can endure
| hunger and cold and any kind of hardship; _for they
| plunge into the swamps and exist there for many days with
| only their heads above water_ , and in the forests they
| support themselves upon bark and roots, and for all
| emergencies they prepare a certain kind of food, the
| eating of a small portion of which, the size of a bean,
| prevents them from feeling either hunger or thirst
|
| https://penelope.uchicago.edu/~grout/encyclopaedia_romana
| /br...
|
| It's historical writing so it _must_ be true.
| jameshart wrote:
| This is fantastic. I'm assuming that "a certain kind of
| food, the eating of a small portion of which, the size of
| a bean, prevents them from feeling either hunger or
| thirst" was Kendall Mint Cake.
| rozab wrote:
| ..since that warning was introduced in 2021
| tfsh wrote:
| It was introduced given the increase in temperature. This
| is the first time in recorded history that the temperature
| in the UK has been forecasted to reach 40degC
| mnobu wrote:
| This will be the hottest temp ever recorded in the UK
| though.
| dcomp wrote:
| To be fair they have been monitoring deaths before [0],
| just the first time there's a national warning to the
| public.
|
| Quite a few schools have decided to use this warning to
| close as they are unable to manage heat on their premises
| [1]
|
| [0] https://www.gov.uk/government/publications/phe-
| heatwave-mort...
| Izkata wrote:
| > 40C
|
| And for those of us in the US who don't know but aren't curious
| enough to look it up: 104 F
| mechhacker wrote:
| This is a very common engineering challenge, but I don't have
| experience with the specifics of rails.
|
| Roads (especially near bridges) have expansion joints so that the
| sections can expand and contract in hotter/colder weather. It
| looks like slab tracks just have more support and try to fight
| expansion. This will increase the load required to buckle the
| tracks, but it will put the entire system (slabs, rails) under
| more stress.
|
| In other industries this can really affect the entire design of
| mechanisms. Motor mounts in cars look to allow thermal expansion
| between the hot engine components and the chassis without letting
| the whole thing shake apart by being too loose. You can make
| designs such that they are very close to being statically
| determinate, meaning there is only one restraint for each of the
| 6 degrees of freedom, so relative thermal expansion doesn't
| stress and fatigue adjacent structures. However, that means that
| adding redundancy in case a single support failure can be quite
| tricky...
|
| One area where thermal expansion is very challenging is
| fasteners. I've seen some machines where the joint had to be
| different materials than the fasteners, and it had to survive a
| wide temperature range, so the torque on the fastener, including
| testing it and calibrating the tools, became extremely critical.
| nimbius wrote:
| as someone who 30 years ago laid rail for the RJ corman railroad,
| the hardest sites were in the southwest. track that can go from
| near zero to fifty celcius is not long for this world. if the job
| site was quiet some days you could even hear the ties groaning as
| the sun came up.
|
| in the US we use a vision system on a special rail repair engine
| that checks for issues, but common controls are lowering speed
| and some days just not using certain tracks
| edf13 wrote:
| Tl;dr
|
| They don't stress them to higher temps because (they say) it will
| cause fractures/stress at winter temps
| dboreham wrote:
| Article doesn't mention but welded track does have expansion
| joints. They just exceed their expansion range at some point.
| Also rails can expand beyond their mounting geometry between the
| joints, on curves.
|
| I noticed the white sprayed tracks in Italy recently. It didn't
| prevent the network becoming congested due to speed restrictions
| imposed as temperatures exceeded 105F.
| scotty79 wrote:
| Does UK really have such large temperature variability?
|
| I thought inland European countries have it way worse.
| 317070 wrote:
| Yes, you are correct. The UK has a temperate climate, unlike
| the continental climate in many other European countries.
| smcl wrote:
| It still occurs in other countries too, you're just reading the
| explanation by Network Rail who manage UK tracks.
| davidthewatson wrote:
| Computer vision can be used to classify sun kinks at speed from a
| train-mounted sensor.
|
| The GPS-triangulated sun kink data can then be used to dispatch
| repair teams to the appropriate location preventing derailments
| in the process.
|
| This has been studied academically and commercially in the US for
| a few years, at least. I'm not aware of a commercial deployment,
| but it may be in progress given the published R&D.
|
| For instance:
|
| https://arxiv.org/pdf/1802.01286.pdf
|
| From the paper: "Sun kink classifier could classify
| professionally simulated sun kink videos with a precision of
| 97.5%."
| gsnedders wrote:
| The challenge is ensuring you have sufficiently frequent passes
| on hot days, and therefore sufficient fitted trains, right?
|
| That paper seems to be notable because it's doing it from
| vision alone (and no LIDAR), whereas similar things (including
| gauging generally) have been used commercially for a while; see
| eg http://www.rail-vision.co.uk/
| WithinReason wrote:
| > The problem is that if we stressed Britain's rails to the same
| degree as those in very hot countries, there would be the risk of
| increased tension on the rails in the winter.
|
| This doesn't make sense, relative to many European countries the
| UK has much milder summers _and_ winters.
| gizajob wrote:
| In the UK, the railway in summer breaks because it gets too
| warm. In winter it breaks because leaves get on the line or it
| is too cold. If its snowing, forget it. For a country whose
| national pastime is the weather, we don't deal with it very
| well the second it shifts out of its bland average. We spend
| the whole year wishing it would get hot and sunny, and then
| freak out the second it does.
| permo-w wrote:
| you could argue that that's because we have such mild
| weather. in other countries typical changes in the weather
| are a bigger deal, so it's less appropriate for small talk.
| this would go some way to explaining why trains stop running
| when it's very rainy/hot/cold/leafy/snowy. we don't expect
| the weather to be drastic, and it rarely is, so we're not
| prepared for it when it happens.
|
| I have no idea whether any of that is true (I doubt it), but
| it was interesting to write out.
| nicoburns wrote:
| British weather is indeed often milder than that of other
| countries, but it's also often much less predictable. In
| some countries it's pretty reliably hot and sunny all
| summer and snowy all winter.
| throwaway294566 wrote:
| In Britain, reliably, once per day it'll rain. Only the
| rest of the weather is unpredictable.
| nicoburns wrote:
| Not in the past few weeks!
| benbristow wrote:
| And for a country that invented the railway too! (Although
| also meaning we have the world's oldest system, and a very
| expansive system at that - even after the Beeching cuts)
| lazide wrote:
| Sounds like Seattle!
| ThePadawan wrote:
| The Swiss railway has a (DE/FR/IT only) page at [0] to explain
| what they do.
|
| - Start adjusting the tension on tracks starting in March when
| it gets warmer
|
| - Use more expensive concrete sleepers where high forces appear
| (as TFA mentions)
|
| - Cool exceptionally problematic parts of the track with water
| from tank cars
|
| So in summary:
|
| - spend money
|
| - spend money
|
| - spend money
|
| That could explain why Network Rail isn't keen on doing any of
| that.
|
| [0] https://company.sbb.ch/de/medien/dossier-
| medienschaffende/so...
| gsnedders wrote:
| > - Start adjusting the tension on tracks starting in March
| when it gets warmer
|
| And of course this also implies adjusting the tension on the
| tracks starting in October or so, too!
| WithinReason wrote:
| Despite saving all that money, the UK has the most expensive
| train ticket prices in Europe:
|
| https://www.vouchercloud.com/resources/train-prices-
| across-e...
| benbristow wrote:
| And most of that money (apart from the recently
| nationalised operators like Northern, ScotRail and LNER)
| goes back to the foreign-ran railways (Abellio/Netherlands,
| Amey/Keolis/France, Arriva/Germany).
|
| It's ace!
| Sharlin wrote:
| It's amazing how many problems are solvable simply by
| spending money.
| ThePadawan wrote:
| A very Swiss attitude.
|
| Like that time in 2016 when a Swiss town paid a 290k CHF
| fine rather than house Syrian refugees [0]!
|
| [0] https://lenews.ch/2016/06/16/swiss-town-pays-instead-
| of-taki...
| jeffrallen wrote:
| Yes that's shameful behavior. Good thing there are 5000
| other communes that take their social responsibilities
| seriously.
| jeffrallen wrote:
| It's amazing how many problems are solvable when a society
| chooses to solve them.
| acer4666 wrote:
| The article explains that European countries replace their
| tracks between summer and winter
| lrem wrote:
| That seems inconsistent with my experience, unless they
| manage to do it completely without disturbing traffic.
| gsnedders wrote:
| A lot of the re-tensioning can be done overnight; there's
| no actual replacement, just changing the level of
| (pre)stress the steel is under.
| [deleted]
| ThePadawan wrote:
| All I could find is this paragraph:
|
| > Some countries regularly have extremes in temperature that
| affect their railway. They may adjust their rails between
| summer and winter, or have other measures in place to manage
| the effects over the long term.
|
| Which, when paraphrased, says: "Other countries may or may
| not do something else".
|
| (Which, when paraphrased, says the PR person had no effing
| clue.)
| jaclaz wrote:
| Also "adjust" does not mean "replace".
| chx wrote:
| The British rail situation can lead to very interesting problems.
| https://www.londonreconnections.com/2015/know-run-story-behi...
| it's one of the most interesting postmortems of a non-software
| issue I've ever read.
| rwmj wrote:
| Northern Japan has a much wider range of temperatures than the UK
| -- -20C in winter to high 30s in summer would all be considered
| normal -- and yet they can run high speed trains all year at 200+
| km/h. How is that done?
| nabla9 wrote:
| Shinkasen tracks have dense placement of strong fasteners and
| prestressed reinforced concrete slabs over thick cement asphalt
| mortar.
|
| (basically tracks over concrete road over thick asphalt like
| road)
|
| This is question of economics, not question of ability.
| numpad0 wrote:
| Multiples of other solutions + expansion joints. Expanding long
| rails blend into fixed "tongue" rails and goes off track
| towards the sides.
|
| 1: (for illustrations) https://costep-
| webteam.hatenadiary.jp/entry/20061023/p1
|
| 2: (for illustrations) http://tarouroom.blog89.fc2.com/blog-
| entry-968.html
| gsnedders wrote:
| As with many (most?) high speed lines, it's done through
| maintenance overnight: the Shinkansen doesn't run from midnight
| till 6am, plus dealing with the potential expansion through
| additional work on the track during those overnight periods
| (largely by re-stressing the steel).
|
| This is all about overnight access and about the cost of the
| work involved.
| smcl wrote:
| They'll perhaps use slab track, like HS2 in the UK will use.
| rwmj wrote:
| This one? https://www.railengineer.co.uk/slab-track-paving-
| the-p-way/ How does this make the rails less likely to
| buckle? Just because it's held in place more tightly?
| pkulak wrote:
| Yes. They actually talk about it in the article.
| bitdivision wrote:
| > The CWR is subject to compression loads due to
| temperature changes, which can cause buckling, or sharp
| lateral displacement. These phenomena are prevented using
| reinforced fastenings, sleepers and ballast.
|
| https://www.ejrcf.or.jp/jrtr/jrtr15/f38_tec.html
|
| I found the above, but it doesn't say that much about
| buckling. I don't think they use slab tracks however.
|
| If buckling is the lateral movement of the track due to
| thermal expansion, I would imagine the old wooden sleepers
| would be much easier to pull sideways. Looking at the above
| link about slab tracks, they look far more secure and less
| likely to move sideways.
| gumby wrote:
| I wasn't familiar with rail ballast but found this good
| link which explains what the term refers to and how it
| helps keep the rails aligned (explicitly the posted
| article talks about when current mitigation is
| indequate).
|
| https://railroadrails.com/information/what-is-railway-
| ballas...
| MilaM wrote:
| Not sure if this is relevant here, but shiny metal surfaces emit
| less thermal energy than painted metal surfaces. Learned about
| this recently while reading about home heating radiators.
|
| https://en.wikipedia.org/wiki/Thermal_radiation#Surface_effe...
| lazide wrote:
| Rusty metal covered in dirt, grease, and oil probably does
| pretty badly though.
| colordrops wrote:
| I love how this article answers the question in the first couple
| sentences.
| immmmmm wrote:
| 1.1 degree above pre-industrial reference and it is already a
| nightmare and yet we drill again to keep the carbon economy
| running.
|
| not a climatologist (just an interested physicist) but (some of)
| these heatwaves overshoot models predictions by a fair margin.
|
| can't wait for the fresh papers quantifying that this autumn.
| it's gonna be bleak.
| zimpenfish wrote:
| I'm starting to take a small crumb of comfort that my advancing
| years mean I'm probably going to be gone before it starts
| getting _really_ bleak. Feel bad for all my younger relatives
| though.
| GekkePrutser wrote:
| In Holland they used to leave big gaps, diagonally cut so there'd
| be overlap.
|
| This have the trains a rythmic kadunk sound that's even been
| popularized in songs :) It also worked quite well as far as I
| know but I suppose it caused more wear and tear on the rolling
| stock.
|
| Not sure if this is still done there though.
| jorams wrote:
| > Not sure if this is still done there though.
|
| It's not[1], and there is risk of track buckles in the
| Netherlands as well. ProRail does extra monitoring during
| heatwaves[2]. I don't remember ever hearing news about this
| being a notable problem, but it probably does happen.
|
| [1]: https://www.prorail.nl/veelgestelde-vragen/hoe-vangt-
| prorail... [2]: https://www.prorail.nl/nieuws/maatregelen-
| tegen-de-hitte
| GekkePrutser wrote:
| I wonder if this new 'voegloos' stuff is quite as good at
| absorbing heat as the 'kedeng kedeng' ones though :)
|
| I don't remember that in the 80s/90s there were such concerns
| and I had family working on railway maintenance. The climate
| problem wasn't as big back then but we had some scorching
| summers too.
|
| Instead the autumn was the all hands on deck period with
| leaves on the tracks and later in the autumn snow freezing
| the switches.
| t0mas88 wrote:
| That sound does not seem to be there anymore, but that could
| just be because of better isolation or suspension on the
| trains.
| jpollock wrote:
| This drove me down a rabbit hole, so I thought I would share.
|
| Track used to be separate pieces (seemingly before 1950), but
| they are now continuous welded rail [1][3]. This was done to
| allow trains to go faster, and lowers maintenance on the trains.
| This confused me because trains go "clack clack clack" - I guess
| that's foley now.
|
| However, it means track is more prone to buckling, since there
| aren't any expansion joints, like we have on bridges.
|
| Slack is added/removed from the rails by stressing the track
| during installation [2].
|
| They heat (or mechanically stretch) the track to the length at a
| chosen "neutral" temperature. Then they install the track. This
| allows them to calculate the max expansion and contraction the
| track will see and offset those forces with the sleepers
| (horizontal forces?) and the ballast (vertical forces?).
|
| The rail can still buckle - this is engineering. If the ballast
| fails, or the temperatures exceed the maximum allowed for, then
| it will buckle. It also looks like it must be continually
| destressed by going along the rail, cutting it and re-welding it?
| [4]
|
| [1]
| https://en.wikipedia.org/wiki/Railway_track#Continuous_welde...
|
| [2] https://en.wikipedia.org/wiki/Rail_stressing
|
| [3] Thermite track welding:
| https://www.youtube.com/watch?v=5uxsFglz2ig
|
| [4] https://www.nzherald.co.nz/nz/peter-calder-old-methods-
| keep-...
| bobthepanda wrote:
| CWR is common to reduce noise and bumps. The latter in
| particular is really important at high speeds, because the feel
| of a bump to a rider is a lot worse.
| salty_biscuits wrote:
| Buckling at high temperature is better than fracture at low
| temperatures. I used to do research in this area. The "holy
| grail" technology would be a non destructive way to infer the
| "neutral stress temperature" of continuously welded rail that
| has been already installed in a quick and non destructive way.
| Saw lots of weird hopeful technology prototypes based of
| measuring the hysteresis curves of induced magnetism in the
| rail, idea being that the stress would have some effect on the
| magnetic domains. Never worked in the field AFAIK. Here in
| Australia they will get hoses out on hot days desperately
| trying to cool the rail down to stop it buckling.
| tobylane wrote:
| The neutral temperature is 27C, we may have to follow countries
| further south in setting it higher.
| int_19h wrote:
| It should be noted that whether rails are continuous or not
| depends a lot on the country and the region. There are still
| many places around the world where you'll find tracks made of
| separate pieces. For example, Russia has around 10,000
| kilometers of track like that (out of 85,000 km total).
| redshirtrob wrote:
| You're correct that the rail needs to continually have its
| stress managed. This could be cutting the rail and adding a new
| piece, or removing a bit. This is a fairly labor intensive and
| costly process so the railroads were very interested in coming
| up with a way to determine when a buckle or break was most
| likely.
|
| Buckles and breaks were most common just after a train had left
| a section of track. The normal approach was to issue slow
| orders when the temperature got too high (buckle) or too low
| (break). So there was a lot of interest in finding more
| accurate ways to determine when slow orders were necessary and
| to optimize when to add/remove rail.
|
| AFAIK this problem is still outstanding. The product I worked
| on years ago never quite succeeded. Railroads are a harsh
| environment.
| laumars wrote:
| Yeah trains haven't clack clack clack for a long time now.
| Possibly as much as 20 years for the lines I'm on.
| the_mitsuhiko wrote:
| What many countries started doing is painting rails white. I
| believe that is also happening in the UK. I believe they started
| doing that in Italy with good results. This is what the painting
| process looks like in Austria in a trial project:
| https://youtu.be/GBMWHAkk6xM?t=52
| curiousgal wrote:
| Why aren't they painting them backwards though?
| lostlogin wrote:
| Good point. However the paint in the hip is going to rub off
| anyway and what's underneath is reflective.
| ThePadawan wrote:
| Here's what SBB (the Swiss train operator) says at [0], german
| only:
|
| SBB will not rely on tracks painted white because
|
| - it makes it harder to discover cracks in the tracks
|
| - with prolonged use the effect noticeably lessens to due
| accumulation of dirt
|
| - OBB and SBB have measured he effect at ~5degC and that's not
| significant enough to be worth it.
|
| [0] https://company.sbb.ch/de/medien/dossier-
| medienschaffende/so...
| the_mitsuhiko wrote:
| It might be a mixed bag and presumably different operators
| have different results. OeBB did not decide yet on the
| future, smaller operators are. Italy has been painting rails
| white for many years (40?) and continues to do so.
| ekianjo wrote:
| how long does the paint last?
| sschueller wrote:
| I believe it lasts quite a while on the sides and the top is
| rubbed to a reflective shine when trains run over it anyways.
| nomdep wrote:
| O__________O wrote:
| Unable to find guidelines or comment from the mods, but HN's
| comments are in English, please use English unless it is a
| comment in English explaining a non-English term.
|
| (Dang, please clarify HN's position on non-English comments;
| believe I recall seeing this before, but unable to find
| guidelines or comment from you. Thanks.)
|
| EDIT: Related comment from Dang on use of non-English
| submissions:
|
| https://news.ycombinator.com/item?id=27571809
| pvg wrote:
| Submissions have to be in English. The problem with the GP
| comment is not that it's not in English, it's that's it's
| tropey and unsubstantive. Just flag bad comments and move
| on.
| zabzonk wrote:
| I agree completely with "comments in English, please". but
| despite not learning any German for over 50 years, I came
| up with "One think works", which is not too far off!
| Akronymus wrote:
| "So easy, so effective" seems like the most appropriate
| translation in this case
| benbristow wrote:
| They started doing that a few years ago. Can see it in action
| on the main bridge going towards Glasgow Central as there's
| lots of points (15 platforms), seemed to help.
|
| Alternately, I've seen videos in the likes of Chicago where
| they've literally installed pretty much bunsen burners and set
| the rails on fire to deal with the winter.
| https://www.youtube.com/watch?v=z76ywZDXyPw
| linker3000 wrote:
| From a linked page:
|
| "We paint certain parts of the rail white so they absorb less
| heat - and expand less. Typically, a rail painted white is
| 5degC to 10degC cooler than one left unpainted."
| picsao wrote:
| the_mitsuhiko wrote:
| Looks surprisingly laborious if this Twitter video is to
| trust:
| https://twitter.com/networkrail/status/1547986150723244032
| pimlottc wrote:
| You'd think they could make a robot to paint the rails but
| then again, the rails on the things that vehicles are
| supposed to be riding on!
|
| Perhaps you could make a device that rides on one rail
| while painting the other one. Flip it around and do the
| other side when you've done the first pass.
| laumars wrote:
| This is an easy problem to solve. You just have the paint
| mechanism at the back of the vehicle so it paints after
| the wheels have moved over the track. Kind of like the
| reverse of the plough at the front of the train that some
| networks (not U.K.) have to clear the track before the
| wheels pass over it.
| jaclaz wrote:
| Of course that is not a problem.
|
| What needs to be painted is the sides of the rail, the
| top - even if painted in the process - will return to
| lucid metal as soon as the next few trains pass on them.
|
| Usually small trucks (Unimogs adapted to rail use) or
| small convoys are used, see:
|
| https://scalaenne.wordpress.com/2016/07/30/binari-
| bianchi/
| peterbraden wrote:
| or just paint behind the robot
| rayiner wrote:
| And use a pencil instead of inventing a pen that works in
| zero gravity.
| happymellon wrote:
| The pencil introduced graphite dust into the air that
| caused electrical problems.
|
| This is why astronauts use a pen. Sometimes the "cheap
| and simple" way has side effects that are more harmful
| than the original problem.
| jakear wrote:
| Oil pencils and wax pencils are a thing too.
| matkoniecz wrote:
| And Russian space station (while they had one) was
| notorious for repeated fires.
|
| Probably that approach to safety was cause for it.
| fl0id wrote:
| How would this be any better then the video? It would
| also be much more expensive and complex then what they
| made.
| Ekaros wrote:
| Painting vehicle and robot likely cost pretty much the
| same. And with vehicle you don't really need to think
| about all of the nitty gritty details of autonomous
| operations or regulations.
| lkbm wrote:
| The GP's video shows them using a spraying train car to
| do it much, much faster. It still has people riding on it
| and walking alongside, but sure looks more efficient.
|
| Meanwhile, I notice that all the replies to the UK video
| are people complaining about the rail system reducing
| headcount and mocking the idea that this task could be
| automated.
| makomk wrote:
| gambiting wrote:
| If you read anything about their demands, you will
| discover that from this year their contract is changing
| to require more hours at the same pay, so they are
| literally being given a paycut. In every other industry
| that would be illegal, but rail workers are expected to
| just suck it up and be grateful that they even still have
| a job, right? They protest compulsory redundancies
| because they know exactly how the British system works -
| a lot of people will be fired and the rest expected to
| just pick up the slack and work more hours, without any
| improvement like automation.
|
| And among other things changes like not being paid for
| their commute when doing overtime(which was paid for
| previously), at the time when petrol has crossed PS2/L
| around the country.
| xyzzyz wrote:
| Are pay cuts illegal in UK? Wow, that's insane.
| laumars wrote:
| Why is that insane?
| gambiting wrote:
| Why is it insane? Maybe I should have clarified - your
| employer cannot cut your pay without a very good reason
| and you have to agree to it. In general it's a very
| tricky process legally, just like letting someone go -
| you need to make sure it's done correctly or you will
| lose in court. They cannot just say "from next month you
| will work extra 2 hours a week at same pay". Like....no?
| That's not in the employment contract we have signed, it
| binds both sides. And yet that's exactly what is
| happening to rail workers.
| xyzzyz wrote:
| Your clarification makes more sense -- I also consider
| reduction in pay to be equivalent to firing, a piecewise
| one. I understand that it means that has to follow all
| rules about firing people, and that much I also find
| reasonable. At the same time, I find the rules about
| firing commonly found in Europe as wrongheaded, but
| that's not my complain above, which is about "illegality
| of pay reduction".
| makomk wrote:
| None of the media coverage I've seen or can find seems to
| mention this supposed paycut due to more hours at the
| same pay, including in really sympathetic outlets like
| the Guardian which describes their demands as being
| exactly what I claimed. In fact, the only change to terms
| I can find anywhere that even vaguely resembles that is
| that maybe some staff will no longer get the same
| generous overtime multiplier on Sunday, and that's from
| the literal World Socialist site which is vague enough in
| their wording that I suspect they might be playing sneaky
| word games again. (They're... not the most trustworthy
| source.)
| londons_explore wrote:
| Such automation will be banned in the UK. Painting things
| has to be done by hand. Union rules. No unauthorized
| mechanization! Spray cans are untested technology and are
| unsafe. Spray paint is worse for the environment and
| workers health. Besides, painting by hand is better for
| morale.
|
| Painting will obviously have to happen at night (double
| pay), and is risky work (double pay again). Oh, and we
| can't do more than 3 hour shifts because it involves
| bending down. And we'll be needing a minimum crew of 8 -
| 1 painter, 1 safety expert, 1 signalling expert, 1
| electrics expert, 1 spotter, 1 paint quality expert, a
| foreman to lead the team, and a union rep to check
| everything is done according to the book. Oh, and
| wherever the work is being done more than 15 minutes from
| a toilet, we'll need a mobile toilet booked and
| installed, as well as a break room. If any of those
| people are missing or late, we'll cancel the work and
| retry in 3 months.
| lol768 wrote:
| Railroad deaths and injuries per capita are much lower
| than in the USA. I'd say the unions and RAIB have done a
| pretty good job at improving safety standards.
| thecompilr wrote:
| Ah, but railroad workers in the US are also part of a
| union/unions, with arguably even more rules and
| regulations and very averse to technological advances,
| since it reduces the need for manual labor. So yeah USA
| would have more deaths because everything is manual and
| archaic, whereas in the UK you have things like the DLR,
| it could never happen in the US.
| londons_explore wrote:
| The DLR is only automated because it's brand new. It
| replaced nobodies job. And even that was a real fight to
| get and caused lots of strikes.
| thecompilr wrote:
| Of course, but try to add an automated line to the new
| york subway.
| alt227 wrote:
| This has been downvoted, but in my experience of 10 years
| of working in the UK rail industry, this is pretty much
| spot on.
| ClumsyPilot wrote:
| while this isn't without merit, I consistently see that
| individual workers are much more concious of quality of
| their work and safety/reliability of the end user than
| the management is.
|
| We've had many industrial accidents, from Bhopal's
| disaster to Boeing Max, thousands of people died, and all
| of them were caused by management meddling where they
| shouldn't. none of them were caused by unions
| nonrandomstring wrote:
| > we'll be needing a minimum crew of 8 - 1 painter, 1
| safety expert, 1 signalling expert, 1 electrics expert, 1
| spotter, 1 paint quality expert, a foreman to lead the
| team, and a union rep to check everything is done
| according to the book.
|
| Hah! Typical free market libertarian approach that cuts
| corners. You can't just go out and start painting stuff
| matey! What about the viability study? Someone needs to
| build a model of the processes, and conduct a pilot time
| and motion study. People won't just accept white rails
| without consultation. Where's the perception management
| and transformation campaign to make sure the new white
| theme is on message and brand aligned for Railtrack?
| You'll have to add at least 1 lawyer, 1 community liaison
| officer, 2 PR people, an advertising account executive...
|
| > we'll need a mobile toilet booked and installed
|
| Toilet? Pfff. You can't just go out and stick up a
| toilet....
| Nition wrote:
| It's even spraying _in front_ of the train car and then
| apparently rolling right over it without much trouble
| (although I note some white paint on the wheels).
| ajkjk wrote:
| It still blows my mind that the color of something makes such
| a difference.
| amelius wrote:
| This is also why I paint my CPUs and GPUs black.
| Too wrote:
| It's easily relatable, compare wearing a black vs white
| t-shirt a warm sunny day.
| blibble wrote:
| a tricolour dog or cat that's been sitting in the sun is
| how I discovered this as a child!
| mh- wrote:
| How did you decide what 3 colors to paint them with for
| the test?
| sangnoir wrote:
| It sounds like a natural experiment to me - genetics
| decided the colors (I'm guessing black, white and brown:
| colors commonly found in multicolored cat & dog breeds)
| Ekaros wrote:
| I suppose you could as well polish them very well, but I
| think that will last shorter time than paint.
| nathancahill wrote:
| Wait until you hear about how much money we could be saving
| if roofs were white instead of the typical dark gray.
| (Locale: en-US)
| bpye wrote:
| Wait why aren't roofs white then?
| burlesona wrote:
| Cultural norms are really hard to change. There is no
| reasonable world in which businesspeople in the US south
| and southwest should wear suits and ties. But if they
| didn't, they would not be taken seriously in our culture.
| Sharlin wrote:
| They are in many parts of the world. The reasons why they
| aren't in other parts of the world are many, but they
| include the fact that bitumen as a petroleum byproduct
| has been cheap; other traditional roof materials used in
| Western Europe are also naturally fairly dark; in cooler
| climates heating has historically been a more pressing
| concern than cooling; people migrating from said cooler
| climates have not bothered to adapt their construction
| methods to local conditions; AC powered with cheap fossil
| energy has been seen as a silver bullet; people choose to
| avoid upfront expenses even if that means suffering in
| the future; cooling is rapidly becoming a concern even in
| said cooler climates, but adaptation lags behind because
| people are surprised that the climate change is actually
| now _their_ problem and not some future people's
| problem...
| CalRobert wrote:
| Just built a house in Ireland (moved here from
| California) and have been very glad we ignored basically
| all the advice people wanted to give us and went for
| things that make it easy to cool. High ceilings with roof
| windows to vent heat have made the last couple days much
| more pleasant. Really glad it's wood and we're not
| dealing with all that thermal mass people here seem so
| enamored of.
|
| I also have a 200 year old stone cottage and when it gets
| hot it stays hot for a very long time (same for being
| cold).
| fmajid wrote:
| There is such a thing as white bitumen, and Obama's
| Nobel-laureate Secretary of Energy Steven Chu had
| suggested we adopt it.
| mediaman wrote:
| Many newer roofs are white. For example, EPDM roofs are
| all near-white.
| mikeyouse wrote:
| Meh, my EPDM roof is black.. I think you're thinking of
| TPO?
| DiabloD3 wrote:
| If you live in the north, it's so you don't have roof
| collapses in the winter due to snow buildup.
|
| If you live in the south, it's because people think there
| isn't good roofing materials that can be lighter colors.
| Those people are wrong.
| Too wrote:
| Once the snow is covering the roof the color can't
| matter? This would only have a marginal effect on very
| mild snow to melt it before it accumulates. Snowy days
| also don't have much sun to catch to begin with, clouds
| ya know. No, roof collapses are prevented by stronger and
| more sloping roof.
| alar44 wrote:
| I can tell you're not from the north. Snowy days aren't
| dark and cloudy. You'll wear sunglasses sometimes. Dark
| roofs absolutely help melt snow. The snow starts melting
| near the gutters and then climbs upward. The snow also
| sublimates. When it gets really cold, clouds can't form
| so there are a lot of bright days without a cloud in the
| sky.
| bombcar wrote:
| The north could (and is!) solved by metal roofs that are
| white or light colored and steep - steep enough that snow
| slides right off.
| gumby wrote:
| Because they produce glare for neighbors. Also tradition.
| Mirrors would be even better, but apart from expense and
| weight, worse for anyone in the path of the glare :-/
| [edit: reply comment to this says mirrors wouldn't
| actually be better]
|
| But, for example, California is requiring light roofs and
| other mitigating issues, so there is some progress.
|
| BTW if you do decide to paint your roof (or any other
| external surface) please use TiO2 paint as the UV from
| the sun will then cause it to break down pollutants like
| NOx and greenhouse gases like methane.
| jccooper wrote:
| Mirrors have low emissivity. While they accept a bit less
| heat, they will hold on to it more than something with
| white paint (which can have pretty good emissivity) and
| will thus get hotter.
| gumby wrote:
| Thanks, that's interesting. Al is a pretty good IR
| reflector, and I believe most common mirrors these days
| use it as the reflective coating. Is the glass the
| problem?
| nine_k wrote:
| The roof of the apartment building where I live is
| silvery-white.
|
| It makes totals sense. I also suppose that many people
| who own single-family houses would not do that, mostly
| because it looks odd. Looking odd is something that makes
| people uncomfortable.
|
| When you find a way for a light-colored roof to look
| _cool_ while also not costing an arm and a leg, people
| will gladly adopt it. This happened to solar panels when
| they started to look well and also signal wealth and care
| of the Earth.
| spyder wrote:
| And for a better effect they could use paint that can cool
| below the ambient temperature by radiating infrared to space
| (if they aren't already using that, but it's probably more
| expensive):
|
| https://www.nature.com/articles/d41586-019-03911-8
|
| Here is a YouTuber trying to making such paint:
|
| https://www.youtube.com/watch?v=N3bJnKmeNJY
|
| Another article:
|
| https://greekreporter.com/2022/05/08/revolutionary-white-pai...
| bombcar wrote:
| The same thing is done to roofs in hotter climates; modern roof
| paint (expensive, it was $160 a gallon when I used it) on a
| roll roof can drop interior house temperatures 5-10 degrees or
| more.
| mordechai9000 wrote:
| We replaced our 40 year old tar and gravel roof (with small
| light colored stones) with a dark colored architectural
| shingle. There was an immediate, noticable difference. On
| summer nights you could feel the heat radiating out of the
| attic after a long day in sun.
|
| This was in a cold climate, albeit at high latitude, so long
| days and low sun angle in the summer means more insolation.
| Since we rarely get above 70F here, I didn't think it would
| make much difference. Of course, it's only noticable a couple
| months out of the year.
| nine_k wrote:
| In a cold climate it could help with heating costs though,
| I suppose?
| toomuchtodo wrote:
| Does this increase the longevity of the roofing material if
| used on something like asphalt shingles?
| bombcar wrote:
| It can, yes. But often with shingles you're better of
| replacing them when worn with shingles that have the
| reflectivity "built in".
| cassepipe wrote:
| Can't eroding paint chips pollute the environment ?
| Faaak wrote:
| Same as when you fart
| masswerk wrote:
| From the video: first trials achieved a cooling by 5 to 8degC.
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