Rail Buckling

[Hove Heretic]

Possibly a daft question, but with rail buckling due to a week of summer weather back in the news, can anyone please enlighten me as to whether UK PW is any more susceptible to buckling than elsewhere? Also, is bull-head track any more or less prone to this problem than the F-B section now used?

 

[joeykins82]

I think I read in one of NR's statements that the Waterloo approach buckling was due to the wooden sleepers used on that section of track and that the newer concrete sleepers are less prone to heat related issues.

 

[Mugby]

It depends what condition it's in. Bull head track shouldn't be any more susceptible to buckling than F/B provided that the rails are adjusted properly with the correct expansion gaps, the fishplates well lubricated and the sleepers and fastenings in good condition. The ballast has to be topped up too, with a good shoulder at the cess end of the sleepers.

Concrete sleepers are perhaps least prone to heat related issues due to the sheer weight of them. I always think that the most likely track to buckle is that on pressed steel sleepers but again it would be largely due to the condition of the ballast.

 

[TDK]

The ballast has to be topped up too, with a good shoulder at the cess end of the sleepers.

That may a problem where a conductor rail is used for power pick up

 

[transmanche]

That may a problem where a conductor rail is used for power pick up

Why so? Surely the third rail is within the dimensions of the sleeper and higher than the running rail?

 

[Trog]

It is also not required that there be a raised shoulder for jointed track.

 

[Geeves]

There was a new one today outside of Manchester Victoria. A sprinkler system watering the rails!

 

[185143]

There was a new one today outside of Manchester Victoria. A sprinkler system watering the rails!

So that's what it was!!

 

[455driver]

That may a problem where a conductor rail is used for power pick up

Not really, as long as it isnt too high and is outside the sleeper end it should be fine, it isnt unknown for them to be too high at points or too close / overlapping the sleeper ends with "interesting" results.

 

[Hove Heretic]

Some interesting observations... a rail sprinkler... wow!! I was wondering how much of the modern buckling problems were down to long lengths of heavy section cwr compared with the far shorter sections of jointed track under the care of (many more) pw gangs than are used/needed today. Re-gapping and fishplate greasing may have been labour (and therefore cash) intensive, but there are far fewer photos of heat buckled pw from days of yore. Or perhaps the press had other things to report back then...

When it comes to the 21st century railway, I'm still at a loss to work out how either Spain or pretty much any country in Africa (especially given the prevalence of metal sleepers there), manage to maintain any sort of service !

 

[sarahj]

One of my books on trains in trouble has a picture of the flying scotsman lying on its side due to rails buckling in the heat, so it did happen in days of yore.

SJ

 

[Mugby]

Around the turn of the present century, NR imported a quantity of Italian rail (due to Corus being unable to meet demand) It was marked 'Lucchini' and was found to be prone to breaking here when temperatures fell below zero because it was a different grade of steel made for warmer climes.

 

[michael769]

I think we percieve that things are worse now, or are worse in this country because they hare happening to us right now . But you do not have to search online very far to find the same problems happen in other countries, and also have been happening for a very very long time.

 

[YorkshireBear]

I think we percieve that things are worse now, or are worse in this country because they hare happening to us right now . But you do not have to search online very far to find the same problems happen in other countries, and also have been happening for a very very long time.

I think the whole forum (including myself) are incredibly guilty of this!

 

[Wolfie]

Around the turn of the present century, NR imported a quantity of Italian rail (due to Corus being unable to meet demand) It was marked 'Lucchini' and was found to be prone to breaking here when temperatures fell below zero because it was a different grade of steel made for warmer climes.

my bold

Have you ever been in Northern Italy in winter? There are numerous ski resorts there for a reason!

 

[O L Leigh]

CWR has longer, overlapping expansion gaps to permit for greater expansion and contraction than would be the case simply by butting up the rail ends.

I think part of the problem in the UK is the temperature range across the whole year. While there are countries with lower minimums or higher maximums, there probably aren't that many that have similar ranges. Taking into account extremes of weather, the temperature can range by around 40 degrees Celsius across a year, from as low as -10 to as high as +30 in an average year.

And not only does the UK suffer with buckled rails as this is a global phenomenon. In fact, the most extreme example I've seen was somewhere in the US where a couple of hundred metres of rail were transformed into spaghetti by the heat, with the track deflecting many metres to either side.

O L Leigh

 

[Mugby]

my bold

Have you ever been in Northern Italy in winter? There are numerous ski resorts there for a reason!

I was merely stating a fact!

 

[Bald Rick]

To answer the original question, the UK is no more prone to this phenomenon than any other country; happily the laws of physics ignore international boundaries

Bullhead rail is more susceptible to buckling as it has a smaller cross section and weight for weight is more prone to horizontal bending than flat bottom. Similarly CEN 60 rail (standard on most renewals on the busier lines for the past decade) is larger in section and stiffer than the 'old' BR113A rail and is slightly less susceptible to buckling.

 

[Trog]

Around the turn of the present century, NR imported a quantity of Italian rail (due to Corus being unable to meet demand) It was marked 'Lucchini' and was found to be prone to breaking here when temperatures fell below zero because it was a different grade of steel made for warmer climes.

I don't think this is true.

Although there may have been a slight problem with the size of the rail foot with the Lucchini rail that required the use of green and white nylons on G44 sleepers instead of the normal two white nylons.
--- old post above --- --- new post below ---

CWR has longer, overlapping expansion gaps to permit for greater expansion and contraction than would be the case simply by butting up the rail ends.

Someone has no idea what Adjustment/Breather Switches are for. There are no expansion gaps provided of any kind within CWR, for the sake of taking up simple rail expansion that is why it is called CWR.

I think part of the problem in the UK is the temperature range across the whole year. While there are countries with lower minimums or higher maximums, there probably aren't that many that have similar ranges. Taking into account extremes of weather, the temperature can range by around 40 degrees Celsius across a year, from as low as -10 to as high as +30 in an average year.

While temperature range is a source of trouble with rail stress, I don't think our range is anything out of the ordinary.

And not only does the UK suffer with buckled rails as this is a global phenomenon. In fact, the most extreme example I've seen was somewhere in the US where a couple of hundred metres of rail were transformed into spaghetti by the heat, with the track deflecting many metres to either side.

O L Leigh

I have been told by someone who was likely to know that the UK has a good record compared to other railways, when it comes to the prevention of buckles.

 

[O L Leigh]

Someone has no idea what Adjustment/Breather Switches are for. There are no expansion gaps provided of any kind within CWR, for the sake of taking up simple rail expansion that is why it is called CWR.

You added the word "within", not me.

O L Leigh

 

[Hove Heretic]

To answer the original question, the UK is no more prone to this phenomenon than any other country; happily the laws of physics ignore international boundaries

Don't ya just wish the same applied to the laws of economics !!

Thinking about desert conditions where the temerature range is even more marked than the UK led me to a search for this issue in Australia. Oddly enough, discussions on 'this 'ere forum what I located' seem to confirm Bald Rick's assertion. Indeed, "Ya canna change the larrs o' physics !" - apparently.

http://www.busaustralia.com/forum/viewtopic.php?f=2&t=38526

Does anyone know how Mr.Brunel's robust looking baulk road behaved in terms of buckling, and is the modern equivalent better or worse than concrete sleepered track in this regard?

 

[Trog]

Does anyone know how Mr.Brunel's robust looking baulk road behaved in terms of buckling, and is the modern equivalent better or worse than concrete sleepered track in this regard?

I would have thought the longitudinal baulks would offer a good resistance to sideways movement, the Victorian practice of just about burying the track in ballast would also have helped. The great width of the bridge rail relative to its height, would also tend to make it stiff in resisting bending sideways.

There is no real modern form of baulk road, the nearest equivalent being long timbers over some older bridges, the junction between the long timbers and normal track is however, a point of weakness due to the difficulties involved in keeping the first few sleepers packed properly. Much better if the structures people can manage it is to have the bridge reconstructed so normal sleepered track can be used right through.

 

[Hove Heretic]

There is no real modern form of baulk road...

Knew I'd seen it somewhere!!

http://en.wikipedia.org/wiki/Ladder_track

Wonder what HS/2 will use, if and when....

 

[brianthegiant]

I think part of the problem in the UK is the temperature range across the whole year. While there are countries with lower minimums or higher maximums, there probably aren't that many that have similar ranges. Taking into account extremes of weather, the temperature can range by around 40 degrees Celsius across a year, from as low as -10 to as high as +30 in an average year.
O L Leigh

Not sure I agree, UK has a maritime climate & temperature is moderated by surrounding sea. In continental climates you get bigger temperature range, Berlin & Moscow would be good examples.

I think the problem in the UK is that this sort of hot weather is a fairly rare occurrence, so these sort of problems manifest all at once and in between are forgotten about again.

 

[RPM]

That may a problem where a conductor rail is used for power pick up

Certainly can be a problem if trains are tripcock-fitted.

 

[miikey]

First off, jointed track should not buckle. If the fishplate gaps are tight, or the joints/bolts are seized then it will basically act as CWR.. no movement of the rails when expended due to heat.
CWR should not buckle either, if correctly stressed and with a well maintained ballast profile. If the track is incorrectly stressed then this could lead to a buckle, however not necessarily cause one.
You need another trigger to cause a buckle, such as poor ballast profile or a site that has recently been disturbed through Tamping or Stoneblowing. Hence why there are heat speeds put on after a Tamper or Stoneblower.

 

[Joseph_Locke]

miikey speaks the truth.

UK CWR *should* be in a state whereby it is stress-free at a rail temperature of between 23 and 27 degress C, a figure arrived at by empirical testing by BR in the 60s.

This means that at temperatures higher than this it is compression and can buckle; however only if it is allowed to, as miikey says. "Perfect" CWR track is good to >53 degrees, which is a state of affairs rarely found in the UK.

At temperatures lower than this, the CWR is in tension, leading, at low temperatures, to broken rails.

The stree-free temperature is a balance between these to extremes; adjustment switches are only provided to allow these stresses to "escape" prior to some feature not intended or capable of withstanding them. such as older S&C, jointed track, some switch diamonds, swing bridges, etc.

Jointed track is not intended nor capable of dealing with high compressive forces in the rail at all, relying on all the gaps at all the joints being correct, consistent and available (i.e. the fishplates are oiled and correctly fitted).

 

[carriageline]

Can I ask, how comes the ballast profile makes a difference? Does it simply just stop the rails from moving?

 

[Trog]

Can I ask, how comes the ballast profile makes a difference? Does it simply just stop the rails from moving?

Provided the clips are sound, and as the prevention of rail creep is very important in CWR they certainly should be. The only way the rail can move to release compressive stress is by moving the sleepers sideways, This movement is resisted by the friction between the ballast and the sleepers, plus the resistance of the ballast off the sleeper end to being bulldozed out of the way by a moving sleeper.

The resistance through friction is mainly the result of the weight of the track pressing the rough sleeper bottom down on the ballast bed, plus some rubbing force on the sleeper sides. The raised ballast shoulder adds weight to the ballast in front of the sleeper end helping to hold it together in a locked mass, so that if the sleeper pushes against it, it resists and does not just roll away like a pile of lumpy marbles.

These resistances work best in rough angular stone, which has had time to shake down into a compact interlocked mass. This is why it is a bad idea to disturb the ballast in hot weather unless you really have to, and why the mandated precautions for hot track cut in at lower temperatures for disturbed track.

 

[Joseph_Locke]

Trog speaks truth also.

The required width of the ballast shoulder is also varied with curvature.

The "lateral resistance" can be augmented on curves by using "lateral resistance plates", which used to be screwed onto the sleeper ends, but nowadays the Vossloh variety clamps on in the foorfoot.