Deforming railway tracks?!

[CornishPete]

I'm sure there's something I'm missing but could anyone explain why railway tracks made from steel, with a melting point of 1400 degrees, would buckle and deform at 35 when they are seemingly fine at 25??! Ever cut through one? They're probably 3 or 4 times heavier than a similar sized rsj!!
Same as engines overheating.
Are these things really designed with only a 10 degree tolerance?

 

[waddycall]

Linear expansion.

 

[voipio]

Expansion. Actual track temperature will be quite a bit higher than ambient air temp, due to the heating effects of sunlight; think car roofs.

 

[CornishPete]

Linear expansion.

Do they not have any method of allowing for this then? And how much do they expand?

 

[voipio]

In the (g)olden days, fishplates were used to join the tracks and allowed some linear movement from expansion. Now, with continuously welded rails, expansion results in compressive stresses in the track, and if track alignment isn't good enough, the tracks buckle to relieve the stress.

 

[waddycall]

No idea but I’d guess they have expansion joints but they weren’t intended to need to cope with these extremes of heat. When you add miles of track together the total expansion must be huge.
Edit- wot he said probably

 

[Parm]

In the (g)olden days, fishplates were used to join the tracks and allowed some linear movement from expansion. Now, with continuously welded rails, expansion results in compressive stresses in the track, and if track alignment isn't good enough, the tracks buckle to relieve the stress.

Exactly this

 

[brightspark]

a few years ago the railway crossing next to me was manned with a br worker all weekend it was red hot . i went out and asked him what the score was . he said keeping an eye on the track for bucking .its all welded for over a mile down the strait but near us theres a joint with a fish plates i looked down the track and it was definately buckled with the heat . it normally isnt. if it gets bad they reduce the speed limit of the train

 

[CornishPete]

I suppose with miles of continuous track even a small expansion per m of track adds up. And I suppose 35 degrees Vs 25 degrees is 40% hotter in percentage terms.
What do they do in places like Africa, India or Australia where it's always hot?

 

[S-Rail]

Having a quick Google , a standard track length is 18 metres with a minimum of 14.3mm gap . Add that over a few miles and you’ve gained a few meters .

 

[brightspark]

its the same when they build

I suppose with miles of continuous track even a small expansion per m of track adds up. And I suppose 35 degrees Vs 25 degrees is 40% hotter in percentage terms.
What do they do in places like Africa, India or Australia where it's always hot?

slow down

 

[voipio]

In cold weather, continuously welded tracks will be in tension. There will be a temperature at which they will be stress free, and above that, in compression.

 

[S-Rail]

its the same when they build

slow down

I’d say speed up ,,, poop or bust

 

[brightspark]

when they build suspension bridges they have to join them at certain times of the day , the last road section can grow or shrink about 1 meter depending on temperature

 

[Fred Trevvett]

And I suppose 35 degrees Vs 25 degrees is 40% hotter in percentage terms.

It's actually only 3.5%. have a look at Kelvin temperatures for further details

 

[mtt.tr]

One of the solutions is to lay track at a higher stress temperature

But then it goes into tension.

 

[Brad93]

In shipbuilding, in strong sunshine, you can literally lose your joint gap on the dark side of the vessel.

 

[8ob]

I suppose its gapped to allow for expansion but kept as tight as possible to keep the noise down. Tough one to balance out.

Bob

 

[Hitch]

Heat expansion can be a surprising amount.

Made a job years ago that were simple guards between sections of a largenoven for curing fibreglass.
They were measured up at the install... went to fit them during commissioning when the oven was warm.
Had to cut all but one down

 

[Maker]

I suppose its gapped to allow for expansion but kept as tight as possible to keep the noise down. Tough one to balance out.

Bob

It doesn't need gaps, its continuous welded rail, if they left gaps it wouldn't be continuous.

The stress in the rail will be well within the strength of the steel, the issue if the ballast isn't maintained properly (Or the rail gets hotter than was intended) then the sleepers can move and the rail gets a kink.