How come railroad tracks that are welded do not buckle?

 
  bevans Site Admin

Location: Melbourne, Australia
From Wiki Answers:

Question: How come railroad tracks that are welded do not buckle?

Answer:

There is no "clickety-clack" on continuous welded rail (CWR). Continuous welded rail is layed in 1320' lengths (a quarter mile). Every quarter mile, one weld is required to bond these two ribbons together, on and on it goes. As far as buckling goes, you're on the right track (pun intended). Expansion, contraction and compression are the three major factors that keep me employed as a railroad worker. In high temperatures, we'll get "kinks" in the track that (I have seen) throw the tracks out of alignment up to 3 feet within a 50-foot distance. The rail looks like a piece of spaghetti. In the winter when the steel contracts, the rail will pop like a cannon and leave up to a 3" to 16" gap. Rail anchors help signifigantly reduce these effects. Anchors are the reason you don't see many "buckles" or rail breaks.

In an ideal world, the air temperature is measured over an extended period of time. Given the temperature range, the track will expand a predetermined amount and will retract a predetermined amount. The whole system of anchors, ballast(rocks) and ties prevents the track from buckling. The idea is that an anchor has a set amount that it will hold, the tie has a set amount it will hold, and the ballast surrounding the tie will hold a set amount. By adding up the retaining force of anchors, ties, and ballast, new rail is stretched or heated to the point where track buckles should not occur.

That being said, there there are many factors which can affect the holding force of the track. Including abnormally high or low temperatures, human error, train braking, age of anchors, condition of ties, etc., etc.

A link is provided to the Wikipedia article on continuous welded rail.


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Why in that case are there heat and buckling issues on the Victorian system?

The weather has been hot in Adelaide, have they had the same issues with track as we have in Vic?

Sydney has also been hot, have they had similiar experiences?

Can someone please provide a reason as to why we have this issue on hot days in Melbourne.

Regards
Brian

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  42101 Banned

Location: Banned
Bevans no track buckles up here because we use CWR on mostly heavy duty concrete sleepers across most of the Sydney system.

We also do what is called adjustments which is cutting several cm out of the rail at various points then belt the rails to destress them allowing that cut out gap to be closed up then we weld it back up thus taking the stress out of the rail so it can expand without buckling....the heavy duty sleepers also hold the rails downwards better than timber sleepers due to their weight and the type of fastenings used.
  FieldShunt74 Chief Commissioner

Why in that case are there heat and buckling issues on the Victorian system?

The weather has been hot in Adelaide, have they had the same issues with track as we have in Vic?

Sydney has also been hot, have they had similiar experiences?

Can someone please provide a reason as to why we have this issue on hot days in Melbourne.
"bevans"


It's a judgement against the state of Victoria!  C'mon, you know you deserve it.  Wink

Jokes aside, I really noticed the high percentage of track in and around Melbourne that still had timber sleepers. CWR on timber sleepers is a recipe for trouble when big upswings in temperature occur. Like 42101 says, you can seasonally adjust your rail tension by cutting and shutting, but you're just moving the neutral point around. It'd be OK if it was a constant 30˚C, but summer temperatures in a place like Melbourne probably still vary from low teens to mid forties. I suppose if you set the tension in the rails for too high a target, and a freaky cold change blows through, you're getting into broken rail territory.

As I understand it, big, heavy concrete sleepers with rigid fasteners are the answer. The rails still want to expand and contract the same as with wooden sleepers, but the ability of the sleepers to hold the tension is much greater. We have WOLO in NSW, but areas with 60kg rail on heavy concrete sleepers are exempt. Fortunately, that's now the majority of the suburban area, and they keep adding new bits. Eventually the whole of the RailCorp area will be covered, and we can forget about WOLO altogether.
  42101 Banned

Location: Banned
Bevans this is the gap left after we cut out 50mm and then rattle the rail with hammers to destress it and allow it to grow in this area of track we did 6 of these adjustments...3 on each rail in a 220m length.
1 Leg of rail is 110m up here.
  cootanee Chief Commissioner

Location: Waiting for the sky to fall, the seas to rise... and seeing a train on the SSFL!
This ATSB report covers 2 derailments on the same day  Exclamation It makes for informative reading.

"The investigation determined that the most probable cause for each derailment was track misalignments in the form of track buckles on a very hot day."

http://www.atsb.gov.au/publications/investigation_reports/2005/RAIR/rair2005002.aspx
  skitz Chief Commissioner

This ATSB report covers 2 derailments on the same day  Exclamation It makes for informative reading.

"The investigation determined that the most probable cause for each derailment was track misalignments in the form of track buckles on a very hot day."

http://www.atsb.gov.au/publications/investigation_reports/2005/RAIR/rair2005002.aspx
"cootanee"


The above report says 'most probabale', only probable when some information was not taken into account.  There is evidence to suggest that something entirely differnt caused the derailments.   The matter is still in dispute.

The key point I make here is that just because the ATSB made a report does not mean its right.
  Fireman Dave Chief Commissioner

Location: Shh, I'm hiding
The simple answer is it does, but it's more complicated than that. The reason welded rail doesn't seem to buckle like you would expect (on account of expansion) is because the rail is held in place with the sleepers. Obviously concrete sleepers do a better job of holding the track in place than timber due to there physical size and weight, but both restrain the rail to a degree.

With out looking up the expansion rates the rails if left free on the ground will expand at a certain rate in all directions, but this rate ONLY applies to free expansion. Once the rail is in place it's held in place with the sleepers the longitudinal expansion is limited, which is why the Alice Springs-Darwin line hasn't ended up in Indonesia.

I hope this makes sence, it's all from memory from about 12 years ago.
  42101 Banned

Location: Banned
The simple answer is it does, but it's more complicated than that. The reason welded rail doesn't seem to buckle like you would expect (on account of expansion) is because the rail is held in place with the sleepers. Obviously concrete sleepers do a better job of holding the track in place than timber due to there physical size and weight, but both restrain the rail to a degree.

With out looking up the expansion rates the rails if left free on the ground will expand at a certain rate in all directions, but this rate ONLY applies to free expansion. Once the rail is in place it's held in place with the sleepers the longitudinal expansion is limited, which is why the Alice Springs-Darwin line hasn't ended up in Indonesia.

I hope this makes sence, it's all from memory from about 12 years ago.
"Fireman Dave"


Dave as i said above we adjust the rail while its in place by cutting out small bits of it the sleepers do anchor it down but without adjustments it would still buckle.
  skitz Chief Commissioner

The key description is that the rail is installed under tension.

Say the rail was set at neutral temp of 38 degress, means that if you cut it would not move.  Below it would spring back and above it would jam your saw.

Resilient fastening assit in controlling creep of the rail and there being inadvertant quantity of rail leadingto higher heat buckle potential.  Obviously the heavier the track straucture compared to the rail the better.  Concrete is good on account of its mass, depth (more balast resistance) and amost always has resilient fastenings.

Concrete however is not the total saviour and will not stop a buckle if the rail is not destressed properly.  The recent derailment at Katherine is and example of this.
  xxxmali Junior Train Controller

Someone should put up a photo or two of a heat buckle, for those that havent seen one..
  62440 Chief Commissioner

On the ABC yesterday there was someone asking why we don't put joints back to stop the heat effects!
Most of the previous comments answer the Wiki US version.
Key items are that the rail has to be in place at the correct neutral temperature (ie no tension or compression loading) and the track structure has to provide adequate lateral stability to prevent kicks. In some places the neutral temperature can have vast ranges, in Canada +40 to -40 and the rails have to be adjusted twice a year (summer and winter destressing).
If the rail temperature is, say, 10 degrees above neutral, there should not be enough compression to cause misalignment.
In Victoria in general and in Melbourne in particular, the dominant track type is dogspiked and plated timber sleepers of varying condition mainly from fair to fail. Dogspikes have no toe load on the rail and do not prevent the rails from wandering. From observation, they are generally not in contact with the rail. Ballast is often in poor condition, not consolidated and has little shoulder beyond or above the sleeper end.
The air temperature today is in the low 40's, rail temperatures will be well into the 50's causing high compression forces. A sharp side load such as a swaying bogie can push it out of line which is why train speeds have to be reduced. A simple tap with a hammer has been known to throw a buckle taking off a lengthman's leg. (In the UK a while back)
In the UK we used to destress at night, often below freezing, our gaps would spring open by up to 300mm before we could cut to length, tension back to a welding gap, weld up and clip. (If using hammers to even out the tension, take care not to bruise the steel, a blow like that has started many a crack.)
Sydney has 1XC track, big concrete sleepers, resilient clips, 60 kg rail and lots of ballast. If rails are laid correctly, buckles will not happen.
Melbourne has poor quality timber track, what concrete sleepers there are appear lightweight, they use non resilient spikes and skimp on ballast. What is surprising is not that there are misalignments but that they keep the trains running on hot days.
Adelaide went to steel which provide lateral restraint and have resilient clips, and are upgrading to concrete
Perth is well on the way to being all concrete, though they still reduce speed on extreme days.
WW
  Fireman Dave Chief Commissioner

Location: Shh, I'm hiding
The simple answer is it does, but it's more complicated than that. The reason welded rail doesn't seem to buckle like you would expect (on account of expansion) is because the rail is held in place with the sleepers. Obviously concrete sleepers do a better job of holding the track in place than timber due to there physical size and weight, but both restrain the rail to a degree.

With out looking up the expansion rates the rails if left free on the ground will expand at a certain rate in all directions, but this rate ONLY applies to free expansion. Once the rail is in place it's held in place with the sleepers the longitudinal expansion is limited, which is why the Alice Springs-Darwin line hasn't ended up in Indonesia.

I hope this makes sence, it's all from memory from about 12 years ago.
"Fireman Dave"


Dave as i said above we adjust the rail while its in place by cutting out small bits of it the sleepers do anchor it down but without adjustments it would still buckle.
"42101"


Yes, but that's not the whole story when it comes to expansion. If the only way of stopping buckling was through the adjustments you've mentioned (which are an extension of the old slip joints used in bolted rail) you would have to adjust the rail every day.
  LamontCranston Chief Commissioner

"clickety-clack"

out Lilydale way it sounds more like a roller coaster.
  LamontCranston Chief Commissioner

Someone should put up a photo or two of a heat buckle, for those that havent seen one..
"xxxmali"

first result from google for heat buckle:

http://www.hothamvalleyrailway.com.au/news.htm
  nscaler69 Deputy Commissioner

Location: There are no stupid questions, but there are a lot of inquisitive idiots.
Picture from AdelaideNow re Adelaide's heat related issues. It was 45.7C today.
Heat buckle on the Noarlunga train line.
  409 Minister for Railways

I imagine that wouldn't have been the only one either because the track in the area around Brighton is basically sitting in mud or dirt and buckled atleast twice last year. The Belair line usually buckles as well while the vast majority of the sleepers are steel set in very dirty ballast or mud holes and has a combination of mechanically bolted and CWR track.

In Adelaide, we have a combination of timber, steel and concrete sleepers on the system as well as ballast of numerous grades, depths and cleanliness as well as a combination of CWR and mechanically bolted track. The Noarlunga Centre, Belair and Gawler Central line have a combination of everything above.
  Natronomonas Chief Train Controller

Why is it that tram tracks don't buckle? Concrete all around (I would have thought that might expand too?)

What about diagonally cut expansion joints - not a blunt end, but the rails at a steep angle to each other... as seen here.
  Myrtone Chief Commissioner

Location: North Carlton, Melbourne, Victoria
Oh yes I have heard of those before, see the image
[bigimg]http://upload.wikimedia.org/wikipedia/commons/1/1e/NYCSub_ExpJoint.jpg[/bigimg]

Tram rails don't buckle or crack proably becuase they are emeded in the street.
  SteamtoStay Chief Commissioner

Location: Building floorplates
Here's another buckle, on the UP track between Jolimont and Flinders Street.

What gets me is that the UP-side rail looks like it's been melted or squashed flat! Can that happen?
  Myrtone Chief Commissioner

Location: North Carlton, Melbourne, Victoria
I notice that the rails are being sprayed with water to cool them, but they may crack.
  42101 Banned

Location: Banned
I notice that the rails are being sprayed with water to cool them, but they may crack.
"Myrtone"


Will you quit posting absolute junk or try learning about what your on about Rolling Eyes ....do you think perhaps track staff would have the experience to know what they are doing.
  tranzitjim Chief Commissioner

Location: Banned
All that golden Drinking water.
  Myrtone Chief Commissioner

Location: North Carlton, Melbourne, Victoria
Will you quit posting absolute junk or try learning about what your on about Rolling Eyes ....do you think perhaps track staff would have the experience to know what they are doing.
"42101"


Why not assume good faith? And anyway, looking more closely at the above photo, at least one of the workmen is hitting one of the rails with a hammer, possibly to whip the rails into shape and they contract so they don't stretch or crack.
  42101 Banned

Location: Banned
Will you quit posting absolute junk or try learning about what your on about Rolling Eyes ....do you think perhaps track staff would have the experience to know what they are doing.
"42101"


Why not assume good faith? And anyway, looking more closely at the above photo, at least one of the workmen is hitting one of the rails with a hammer, possibly to whip the rails into shape and they contract so they don't stretch or crack.
"Myrtone"


Man your better than a comedy festival you are Rolling EyesLaughingLaughingLaughing .
The fettler is using...a...sledge...hammer...to..hit...a ..pigs ...foot...to...pull..out...the...dog...spikes..is this slow enough for you to understand it ?????
How will one fettler with one hammer knock that kink out of the track????? Rolling EyesRolling Eyes
  409 Minister for Railways

Greg, would you mind if I pick your brains for a sec? Having a look at your earlier photo of adding tension to rails, how long does such a process usually take from start to finish?

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