Melbourne newspapers today carry stories about how heat can cause suburban train lines to suffer buckled rails as shown in some graphic photos from 2009.

The most common response from readers is to blame "idiots" who managed the welding of all rail joints thus leaving no room for expansion.

The simple answer is welded rail is fine as long as concrete sleepers, metal rail clips to attach the rail to the sleepers and sufficient ballast is used.

To prevent a rail buckling an equal but opposite amount of "tie down" force needs to be applied, this is achieved by lots of good quality ballast, concrete sleepers and metal rail to sleeper clips.

SA WA QLD NT etc all have this kind of track and suffer little or no heat expansion problems at all in much longer bursts of hot weather than Melbourne.

Melbourne newspapers today carry stories about how heat can cause suburban train lines to suffer buckled rails as shown in some graphic photos from 2009.

The most common response from readers is to blame "idiots" who managed the welding of all rail joints thus leaving no room for expansion.

The simple answer is welded rail is fine as long as concrete sleepers, metal rail clips to attach the rail to the sleepers and sufficient ballast is used.

To prevent a rail buckling an equal but opposite amount of "tie down" force needs to be applied, this is achieved by lots of good quality ballast, concrete sleepers and metal rail to sleeper clips.

SA WA QLD NT etc all have this kind of track and suffer little or no heat expansion problems at all in much longer bursts of hot weather than Melbourne.

The Age mentions the experience in Perth, which has just had a string of 40+ degree days, yet not a single Transperth train was cancelled due to the heat.  Metro, by contrast, has reportedly cancelled "dozens" of trains in anticipation of the heat.

But surely even welded rail on concrete sleepers etc., as described, must expand in extreme heat?  

Will we see a return of the white paint this summer?

The Age mentions the experience in Perth, which has just had a string of 40+ degree days, yet not a single Transperth train was cancelled due to the heat.  Metro, by contrast, has reportedly cancelled "dozens" of trains in anticipation of the heat.

But surely even welded rail on concrete sleepers etc., as described, must expand in extreme heat?  

Will we see a return of the white paint this summer?

Didn't stop the Iron Ore trains running in the around Geraldton either! They run on Concrete Sleepers here.

The Age mentions the experience in Perth, which has just had a string of 40+ degree days, yet not a single Transperth train was cancelled due to the heat.  Metro, by contrast, has reportedly cancelled "dozens" of trains in anticipation of the heat.

But surely even welded rail on concrete sleepers etc., as described, must expand in extreme heat?  

Will we see a return of the white paint this summer?

If you can't fix a problem you paint it a different colour.

The Age mentions the experience in Perth, which has just had a string of 40+ degree days, yet not a single Transperth train was cancelled due to the heat.  Metro, by contrast, has reportedly cancelled "dozens" of trains in anticipation of the heat.

But surely even welded rail on concrete sleepers etc., as described, must expand in extreme heat?  

Yes it does but concrete sleepered track works differently to timber sleepered track. In the latter track the spikes are designed to allow the rail to slip, allowing the expansion to be taken up by the expansion joints. With Concrete sleepered track the clips hold the rail tightly so it cannot slip. The sleepers are also quite heavy and most important of all the tension in the rail is very closely controlled so as the track changes in temp from around -6 degrees c to say +50 degrees, the tension/compression in the rail never exceeds the point where damage would occur. Thus the expansion/contraction is spread through the entire length of the track so buckling cannot occur.

Note, when comparing  localities you have to look at the complete temperature range NOT just the maximum temp. So say in coastal Queensland where the temp range is around 25 to 38 degrees will have much less of a problem than Victoria with a range of -6 to 50 degrees. Somewhere like Britain where the temp can vary from -15 to 40 degrees will have a similar scale of problems as Victoria because of a simliar temperature range.

woodford

Much of Victoria's track is still on wooden sleepers.  Almost all is on thin ballast.  Concrete sleepers and rails secured with Pandrol or similar clips which are designed to prevent expansion are being introduced but will not provide a fully effective solution unless matched with deep ballasting.  

In simple terms the forces of expansion are overcome by the application of  greater force of resistance in the clips.  Concrete sleepers don't splinter and "give" as wooden ones do.

Until there are no pockets of wooden sleepers left and the tracks are ballasted to best-practice standards we are stuck with the slow-downs.

It's not unique to Melbourne but our temperature range is higher than some places as noted above.  Maximum speeds are imposed on rare occasions in the UK even though their routes are mostly laid with world-class track and ballasting.  Painting the webs (the upright faces) of the rails with white paint has been successful in reducing rail temperatures by a couple of Celsius degrees but not to the extent that speed restrictions can be avoided.

It comes down to Australia failing to invest adequate sums in its infrastructure and not adopting world's best practice solutions.

What is the scientific basis of the reduction from, say, 115km/h to 80km/h (assuming there is one and that 80km/h is not just a 'stock figure'?
I would have thought that there would be differing reductions on timber sleepered track v concrete sleepers perhaps coupled with differing weight of rail?

What is the scientific basis of the reduction from, say, 115km/h to 80km/h

Derailing at 80 is less severe than doing so at 115.

Thank you woodford and Gwiwer for your explanations.  

Where wooden sleepers have been entirely replaced with concrete ones, rails welded and properly clipped, but the ballast remains as before and possibly sub-standard, what happens then?  Does the sloppy ballast allow movement of the concrete sleepers, due to tensions in the rails?

What about the sections of "pepper and salt" track, where there is a mixture of wooden and concrete sleepers?  

Woodford mentioned that with wooden sleepered track, the spikes are designed to allow the rails to slip, which makes sense, but some more  recently installed wooden sleepers have the rails clipped rather than spiked.  Can the rails "slip" past these clips?  

It would seem that the current re-sleepering programs are really only intended to replace wooden sleepers with more durable ones, that need to be replaced say every 40 years rather than every 10 or less.  A side effect is a smoother ride for the trains, but it is not really about upgrading the quality of the track??  I hope that's an unfair assumption.

Watch and learn.

Rails that grow pt1


http://www.youtube.com/watch?v=ZcqcC2Dv0d8

Rails that grow pt2


http://www.youtube.com/watch?v=OLA-9lU6k-g

http://www.youtube.com/watch?v=zIc2l5f2J1s

Thank you woodford and Gwiwer for your explanations.  

Where wooden sleepers have been entirely replaced with concrete ones, rails welded and properly clipped, but the ballast remains as before and possibly sub-standard, what happens then?  Does the sloppy ballast allow movement of the concrete sleepers, due to tensions in the rails?

What about the sections of "pepper and salt" track, where there is a mixture of wooden and concrete sleepers?  

Woodford mentioned that with wooden sleepered track, the spikes are designed to allow the rails to slip, which makes sense, but some more  recently installed wooden sleepers have the rails clipped rather than spiked.  Can the rails "slip" past these clips?  

It would seem that the current re-sleepering programs are really only intended to replace wooden sleepers with more durable ones, that need to be replaced say every 40 years rather than every 10 or less.  A side effect is a smoother ride for the trains, but it is not really about upgrading the quality of the track??  I hope that's an unfair assumption.

A number of interesting points in the above most of which I do not have the knowledge to answer well, but a couple of points. The sleeper life on the NE line acccording to all I talked was 20 years
As far as my experience goes the two major advantages of concrete sleepers are they hold the track dimensions VERY well, with timber sleepered track one is lucky to get the gauge plus or minus 1.6mm and one has no difficulty in seeing the gauge 10mm out. Concrete sleepers from all the measruements I have taken (the railways I worked on all used timber sleepers) never deviate more than a few 10ths of a mm. The second advantage is a much longer life.

One must remember that most railways jn Australla are insufficently funded. the management have to make choices over a very limited number of options AND keep the network running, under such conditions making a "right" choice is impossible so they have to do the best they can which under the circumstances will never be good enough. The managment of both VLIne and ARTC earn every cent that they are paid, it being in my opinion one of _____THE______ worst jobs in the world, that is being in charge of major infrastsructure that is under funded.

woodford