Railways

[Yai]

How do they prevent railways in hot countries like in Africa from buckling in the constant heat ?

[wildwood]

This is only a guess, but perhaps they use shorter rail sections - more joints, to compensate for the expansion.

[Gef]

If you are old enough to have travelled by train in the sixties you will remember that there was always the "clickety - clack" noise from the wheels. This was caused by the expansion gap between the rails every 100 yards or so. Nowadays we have continuous welded rails where there is no gap for, I guess, several kilometers and perhaps that gap it too small for the current high temperatures. I guess that in hotter countries they leave bigger and more frequent gaps. I"m sure someone will post a more definitive answer..

[OnlyMe]

They build 'em properly.

[anthomson]

Not sure I quite agree here - I have just read an article saying that some railways in Africa are in real jeapody because of this problem and places like India are notorious for train accidents which I guess may be related to track problems. Modern railways will be less susceptable to the heat related problems since they make use of newer technogies ( e.g. specials alloys more tolerant to heat, 'anchor points ?' which absorb expansion throughtout the length of the rail etc.) I think there is also a trade off against comfort - short track with gaps every few metres makes for a very uncomfortable ride.

[catgate]

Well... we often hear about "infrastructure" in conection with railways, and herein lies the answer. They always keep the infrastructure in a fridge overnight and then take it out early in the morning and slip it under the lines to keep them cool during the day.Simple as that.

[andy hughes]

Apparently railway tracks are constructed with a degree of tension in them, which allows for a degree of expansion and shrinkage. The degree of movement is calculated by assessing the average higest and lowest temperatures for the country concerned, but in cases of freak temperatures, such as we are getting now, problems do occur. This explains why African and Indian railways work fine in their tempartures - the factor of excessive heat is built in. If they had previously unknown temperature rises, or indeed falls, they would experience similar problems. So that explains why there are speed and movement restrictions during this heatwave - I'll keep my eyes open for valid reaons for snow / rain / leaves on the line etc. etc.

[mushroom]

In terms of engineering, all fixed rails are subject to expansion on hot days. Rail operators have two methods of dealing with this, preventative engineering solutions and constant monitoring. The continuous welded track which is commonplace on Britain's long distance routes appears to be more prone to buckling that the old fashioned bolted sections. However, by using simple engineering principles such as the right amount of ballast under the track and the correct weight of concrete crossbeams, lateral shift (buckling) can be minimised. In addition, it appears that overseas operators of networks in hot climates have permanent patrols trackside monitoring the rails and early warning signs such as movement of the ballast.

[ianess]

The ends of the rails don`t have to be butted together at right angles as in the good old days.  I may be wrong but I think that nowadays, as well as being pretty much continuously welded, any joints are more wedge shaped so that the rails slide apart without opening up a gap as they expand.  It sounds OK but it`s only a suggestion......no guarantees!