Welded Rail

[Modelcar]

....Forgot to sign above...QM

[Modelcar]

One would think they would have a "high tech" thought to use on the rail movement caused by summer to winter, etc...Can't see what some rail joints would harm and surely they could stand the clickedly clack of added safety. It must be a rather high priority...[expansion / contraction], and I'm sure they have their answers and follow them.

[Anonymous]

I've often wondered why the companies don't have some sort of "plug" every so often, one for hot weather and one for cold, that they could bolt in depending on the season, as it is right now, at the end of every winter they have literaly hundreds of new joints (where the rail broke) that they have to welded. Granted there would still be some broken rails simply because of fatigue, but it would be a lot less, and there would still be some expansion issues as well, but I believe they would have a lot less alignment issues in the summer time. It seems it would be cost effective, but maybe not.

[sooblue]

Everything is getting so scientific now days that unless you are on site and witness what is being done and even in what order, you would never know how much of anything is done. Even seemingly simple things are engineered these days.

[Anonymous]

When I started railroading most track where I worked was still jointed rail. I remember they installed some test ribbon on a branch line. I used to see sun kinks on occasion. Over the years it has gotten to the point that no jointed rail is on the main that I know about. The techniques they use when laying rail has made it so a sun kink is rare and you have only an occasional pull apart. When laying rail the temperature is taken and sometimes they heat the rail to get to what they have as an optimal rail temperature and all rail laying data is recorded so if compensation like cutting some rail has to be done later it will get flagged in the database and done.

[Modelcar]

In reading your response and many others and understanding some of the issues on hot and cold as it has it's effect on the integrity of continuous rail structures....I wonder if having a break at the quarter mile lengths of ribbon rail wouldn't be a good idea to build in some safety factor from the above elements. I know it would bring back some of the clickedy clack of the bygone era of railroading, but perhaps it might be a valuable safety valve.

QM

[Anonymous]

You are correct that steel will expand in every direction as it warms, however, due to the shape of rail, it's largest natural expansion/contraction would be lengthwise. Thus they are forcing it to behave differently than the pyhsics of it's construction predispose it to. As to the gauge, there is enough "slop" in the gauge to account for the expansion/contraction of the rail. I don't remember the exact specs, but there is ample room to acount for fractions of an inch in expansion. I have never seen it lift the track structure although I'm sure it would be possible, what usually happens is a "sun kink" or thermal misalignment as the railroad likes to call it. The track bows out to one side or the other. Sometimes they are a series of small "waves" (look at a stretch of straight track on a real hot day and you can usually see this) or sometimes it's a big blow out to one side or the other (usually causes a derailment if the train hits it fast enough). I saw one on a stretch of double track that had bowed all the way over to and sort of on top of the track next to it! (got lucky we didn't have a collision there!) Also, all these same forces have the opposite affect in the cold, contracting the rail and putting it into extreme tension, that's why you have so many broken rails in the winter, it just pulls the steel apart or if you happen to have some joints it breaks the bolts (sometimes breaks the joint bars themselves too).

[Modelcar]

I'm sure they can live with that gauge change...
On the 1" figure I used back a few entries it was an estimation on my part just from remembering what the gap between rails looked like between summer and winter...[Pennsylvania weather]. It was significant.

QM

[oltmannd]

For steel, forcing a change in length will cause a 25-30% change in width and height. So if you compress a 39' rail 1", you will cause the width and height to change 0.30 x 1/(39 x 12) = 0.00064 or 0.006%. If the rail head is 3" wide, you'll reduce the gauge by .002".

[Modelcar]

Well if the rail anchors do their job winter vrs. summer and keep any length expansion to a minimum...it sure must get puffed up in cross section...Expansion has to go somewhere...We can't fool mother nature.

QM

[Anonymous]

I wonder how much longer NS, CSX, UP or BNSF is in the summer vs the winter?

[Modelcar]

Yes, I have read those...also the derailment of Amtrak in Florida of several months ago.

I just did some quick figuring of rail expansion and figuring 1" per 39' of rail summer to winter and see it could be about 11' in one mile if it was not held tightly in place...I am amazed the problem is managed as well as it is.

QM

[Anonymous]

Not as much bother as a derailment! There is a good discussion of heat kinks in the various posts re: Amtrak's derailment at Kensington. Flip through those, discard the biased junk and you'll find a very informative explanation about heat kinks. gdc

[Modelcar]

The last several entries have enlightened me as to what rail anchors really do....Thanks. Now I can look and think about the circumstances with which they are working as I see them.

It seems they would be a bother when any track work is being done...especially installing new ties.

QM

[BR60103]

Rail anchors are also used on jointed track. They keep the rail from sliding along the ties, so they appear where there is extra longitudinal force regularly applied to the rails, such as braking or gradients. They are put on the uphill side of the tie on grades and on whichever side is required for braking or accelerating. At our local station, there are a lot on both sides on the passenger platform track.
Even our local streetcar museum uses them.
--David

[sooblue]

Hi
What you explained helps me to understand how there would be no expantion joints. However I will point out that steel unrestrained will naturaly expand in every direction so if the rail is prevented from sliding by the anchor the rail will expand where ever it can. If it can not slide than it must go up and get thicker.
Track guage must take that into consideration for proper tolerance. Does the track ever lift sections of ties? I know there is a lot of force involved because I've seen anchor bolts imbedded in concrete get pulled out and even seen nuts get popped off the anchors.
Mike

[Anonymous]

Yes, very intense pressure. They are trying to force the steel to expand in a way that it wouldn't naturaly (upwards rather than lenghtwise). That's why MofW has to be very carefull when changing out rail in the summer, as it will tend to "spring out" once it's released. The anchors are actually quite simple to put on..they just snap on. they can be put on with a sledge, but usually are put on by machine. The anchor itself isn't actually attatched to the tie, rather it is pressed up against it. one on each side of the tie, the 2 of them work together like a clamp, squeezing the tie and preventing the rail from sliding.

[Modelcar]

Yes...I am trying to imagine such forces on a very hot and sunny day with the heat radiating down onto the mass of metal and trying to imagine something holding it in place against that force. I remember looking at non welded rail with the space between joints and the difference between summer and winter just in a 39' length...Boy, trying to contain that force in great lengths is mind bogging.

How are the "anchors" fastened to the ties..? That must surely be time consuming to install them as someplaces they are at every tie.

QM

[oltmannd]

If you think of rail as a long, very stiff spring, it might be helpful understanding how welded rail can with stand heat and cold.

When it gets hot, the rail will try to expand. The rail anchors hold it and keep it from expanding, compressing the rail longitudinally. The rail anchors clip to the rail, one on each side of the tie and keep it from moving relative to the tie. The ties are held in place by the ballast, which actually digs into the ties a bit and the ballast is kept in place by it's own weight and friction. So, the rail has nowhere it can go - it is held in compression. The forces can get pretty high, but spread out over so many rail anchors, it is easily accomodated.

[Modelcar]

Would someone explain what job the "rail anchors" do. What exactly what is their job...? How and what are they fastened to besides the rail..? I have seen these items on track so often and never have seen any work being done by maintenance people with them to see how they are installed.

QM

[sooblue]

I've had some experiance with heat and steel including rail. Just a few degrees of temp. increase will move steel a lot. It's quite amazing really. I installed rail in 10 concrete block curing kilns that are filled by small automated rail cars. The tempratures rarely get above 150 degrees yet when I first installed the rail the tolerances between the end of the rail and the positioning car that ran perpindicular to the kiln rail were too close (1/8") as the rail heated up it grew longer and the positioning car would hit the rail. The gap had to be almost half an inch (7/16") in order for the lower car to clear the rail if it's corrisponding kiln was heating. The rail was imbedded in concrete its' entire length, the only thing it could do was grow longer.
My question, doesn't welded rail have to have expansion joints every so often? even if the rail was imbedded in concrete it is still going to go some where. I also found that the rail grew thicker as well and that popped out the concrete in places too. A lot of movement.
mike

[Anonymous]

I believe that the purpose of "rail anchors", is to eliminate longitudinal movement of rail. Welded rail can go from one temperature extreme to the other just fine, as long as it only expands/contracts, in "cross-section", not length. Where you have variable weather, (everywhere except Hawaii), there should pairs of rail anchors at every tie. These are the little "J" shaped castings that clip to the base of the rail on both sides of the tie.
Todd C.

[Anonymous]

Right on the mark! If you take care to stress welded rail when it is installed and maintain the cribbing, heat kinks will not be a problem. Right now, I've only heard of one road with heat kink issues. Are there any others?

[CShaveRR]

I would hope not...welded rail has far too many advantages over jointed rail in terms of maintenance requirements, extended rail life, and on and on.
You don't hear too much about sun-kinks on well-maintained trackage. If things are done right to begin with, the problem is minimized.
The answer is more money for maintenance--the question is, are you going to pay more to maintain a track with jointed rail, or are you going to pay more to better maintain the roadbed underneath the welded rail?

[Anonymous]

I recently heard a comment on NPR that the railroads were considering goiung back to jointed rail because of the heat kinking of welded rail. Any truth to this