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[spectratone]

are new rails cut after install or do they have expansion joints or something? relief cuts? or are they one piece welded together?
thanks
glenn

[trainboyH16-44]

Well, there are usually two types of rail in that way. The first, and older kind, commonly found in yards and on less used sidings, is jointed rail, with sections that are usually about 39 feet long. These joints do absorb expansion.
The other kind is continuous welded rail, usually in quarter mile long sections, and is used on most mainlines and some sidings, and is held in place with rail anchors to avoid it kinking in the sun, or other problems caused by expansion and contraction.

[BR60103]

There are some places where there are expansion joints. I think around bridges where expansion could be critical. The joints are like switch points, with the other rail turning off to the side.
One of the mine railroads (forget the details) had a long grade where the rails were pulled downhill by the locos on long trains. A length of rail was cut off annually as the rails stretched.

[TomDiehl]

There are actual expansion joints. The one I've seen most commonly looks sort of like a switch point. However, what would be the "point" is stationary and the rail expands and is pushed outside the gauge.

[tree68]

For what it's worth, I recall reading someplace, in response to a similar question, that with CWR, the fact that it's well anchored (hopefully) causes the expansion to occur in the width and height of the rail, not the length. Sun kinks would tend to tell one that such a concept has its limits, but it does make a certain amount of sense.

[Leon Silverman]

I first heard about welded rail being used in the 60's when I was a college engineering student.  I asked my colleg professor about the stress built up by temperature variations.  He replied that the stresses generated were well within the elastic limits of the steel, meaning that a properly anchored rail will not distort. 

 If you read other entries in the Model Railroader Forum regarding expansion and contraction of  model railroads, you will discover that the main problem is dimensional changes caused by moisture variation in the wooden structures and not temperature response of the rails.  The offered solution is to either seal the wood (or homosote, if used) with some kind of paint or use styrofoam subroadbed. 

[Leon Silverman]

I first heard about welded rail being used in the 60's when I was a college engineering student.  I asked my colleg professor about the stress built up by temperature variations.  He replied that the stresses generated were well within the elastic limits of the steel, meaning that a properly anchored rail will not distort. 

 If you read other entries in the Model Railroader Forum regarding expansion and contraction of  model railroads, you will discover that the main problem is dimensional changes caused by moisture variation in the wooden structures and not temperature response of the rails.  The offered solution is to either seal the wood (or homosote, if used) with some kind of paint or use styrofoam subroadbed. 

[Anonymous]

Here are Rail Expansion Joints as used by Montreal Tramways, in this Case, just before a Turnout.

http://dewi.ca/trains/montreal/pix/a005_12.jpg

They were also used just before Open Track went into Street Running.

Route 17 shown here went to Busses in June 1959.

All Streetcars gone in Sept. 1959.

CPR Steam Hung on into 1960 in Regular Service in the Montreal Area.

[ndbprr]

Most of the time the clips used on welded rail force the expansion vertically.  The weather the country is experiencing this week with the entire country over 90 degrees you can expect that some locales not used to this type of weather will experience what are called sun kinks where the rails suddenly make an S curve over which the trains can not pass and must be alert to avoid.  If I were a member of a railroad mechanical deprtment I would install the rail at the anticipated mid point of temperature range so it would minimize expansion and contraction.  It is generally when temps get beyond normal that kinks occur.

[Anonymous]

This was covered in an issue of Trains Magazine a little bit ago.  Essentially, the rail is anchored to the ties so it can't expand in length, and is forced to expand in width and height.  However, on hot days there can be a tremendous amount of lengthwise stress generated, and this will sometimes generate a "heat kink" in the rails (the rails suddenly develop a little curve section) which is very dangerous at maximum speed.  On hot days, most railroads will issue a "slow order" to have the trains slow down by a certain percentage at the hottest part of the day, so that if a heat kink builds up, there is less chance of a derailment, and if the train is going slower, the sidwards thrust of the cars going into a curve will have less chance of actually creating a heat kink.

On cold winter days, there is the opposite problem:  The track tries to contract, and cannot, so it gets shorter (heigth-wise) and thinner but the length stays the same.  The cold makes the steel more brittle, and it also causes it to try to separate the joints (or just break, in the case of welded rail). This causes signal system failures in cold weather as joint bars or insulated joints need to be replaced when the cold pulls them apart (usually just as a train passes overhead, adding to the rail stress).  Of course, when the signal system fails under my train, there are many possible causes for it, one of which is a derailed car or broken wheel destroying the track, so the latest set of rules states that, if two or more signals fail while I go over the rails, I have to stop and inspect every wheel on every car, for derailments, flat spots, broken flanges, and so on.  And of course this is only on really cold days...  Can't wait to get through engineer's school.

[Poppa_Zit]

The derailment of the Amtrak Auto Train near Crescent City, Florida on April 18, 2002 was caused by sun kink.

http://transcripts.cnn.com/TRANSCRIPTS/0204/19/lt.21.html