# MISC | Expansion and Contraction in Continuous Welded Rail



## tuckerbox (Oct 15, 2007)

In New South Wales a couple of years back, they sprayed long lengths of rail track with white paint to test the expansion rate in very hot weather.
I dont know what the outcome was- maybe somebody over there might know.


----------



## cees (Jun 25, 2006)

*no bump*



Trainman Dave said:


> Ten to fifteen years ago, I read a technical discusion of using very gently curving railway lines instead of straight lines to absorb the expansion and contraction of the actual rails on a continuously welded railway. The ballasted road bed on the curves was designed to absorb the changes in length of the rails by moving in and out. To balace the inside/outside rail effect, it required "S" curves!
> 
> I appologise, but unfortunately, I cannot find the original material to give you a citation.
> 
> The conclusion was that it would probably reduce the catastrophic "kinks' significantly but it required extremely costly maintenance which would limit its application. I have never heard of this actually being applied in practise.


this railway here is build like that. already 20 years right now. and its all curved. excactly with the same "S" curves you're talking about. all between weesp and lelystad there's not any bump. i don't know about maintenance costs. what I do know is that it's always quite expensive in here because of sinking ground, i guess it won't bother that much.


----------



## Trainman Dave (Mar 30, 2007)

cees said:


> this railway here is build like that. already 20 years right now. and its all curved. excactly with the same "S" curves you're talking about. all between weesp and lelystad there's not any bump. i don't know about maintenance costs. what I do know is that it's always quite expensive in here because of sinking ground, i guess it won't bother that much.


Thank you for the info


----------



## kokanee2 (Jan 27, 2008)

trainrover said:


> Does anybody know how contraction/expansion happens/is accommodated for between/along? long sections of welded rail nowadays?


Well.... my uncle informed me that the rail on the Sishen-Saldanha iron ore railway was pre-stretched, before it was fastened to the ties, to eliminate the potential of buckling due to thermal expansion.

I know that CPR doesn't stretch the rail before its fastened, so I imagine the breaks at switches (points) suffices.


----------



## mgk920 (Apr 21, 2007)

kokanee2 said:


> Well.... my uncle informed me that the rail on the Sishen-Saldanha iron ore railway was pre-stretched, before it was fastened to the ties, to eliminate the potential of buckling due to thermal expansion.
> 
> I know that CPR doesn't stretch the rail before its fastened, so I imagine the breaks at switches (points) suffices.


As I mentioned upthread, normal procedure is to heat the rail to the highest temperature that is normally expected for the area and then clamp rail anchors onto it. As the rail cools, it contracts and goes under a tension, preventing 'sun kinks'.

Mike


----------



## trainrover (May 6, 2006)

I forgot about this thread. A belated thank-you to you, svartmetall. It was welds themselves that I've always wondered about.


























^^ interesting variety of joints sampled, although last 42" utterly useless ... mute! :wallbash:................









Trainman Dave said:


> Ten to fifteen years ago, I read a technical discusion of using very gently curving railway lines instead of straight lines to absorb the expansion and contraction of the actual rails on a continuously welded railway. The ballasted road bed on the curves was designed to absorb the changes in length of the rails by moving in and out. To balace the inside/outside rail effect, it required "S" curves!
> 
> I appologise, but unfortunately, I cannot find the original material to give you a citation.
> 
> The conclusion was that it would probably reduce the catastrophic "kinks' significantly but it required extremely costly maintenance which would limit its application. I have never heard of this actually being applied in practise.


I think cees' 20-year reference must refer to how long it's been since I last rode welded rail ... this S-curving technique's probably the corresponding answer to my old musing.

What's the longest segment possible with welded rail nowadays, longer than that rail weld train filmed in the Sierra trench?


----------

