[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. ___________________________________________________________________ (page generated 2022-07-16 23:00 UTC)