Western Railroad Discussion > Want to see a sun kink?

Heres a sun kink.

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When I used to work for BNSF, we took care of these several times. Once we actually took out 9-10" of rail! And this was on concrete ties...which doesnt move as much. Amazed us all.

Matthew
http://www.bnsfpix.com

Not surprising that track kinked. Where's the ballast?

LOL!

Looks like new track going in w/o the track gangs straightening out or ballasting anything yet.

-Ryan aka "espeeboy"

I was going to comment on the lack of Ballast too. There should be a good 12" of ballast off the end of each side of the ties before it slopes down to ground level, that goes a long way toward preventing sun kinks.

Ted Curphey
funnelfan@icehouse.net

This looks like some kind of siding under construction...not ballast applied yet.

The pressure from the expanding steel has to go somewhere...how is this supposed to work? I thought these welds were supposed to be applied at something near the "normal" temperatures in the area to help prevent these kinks. I would suppose if the temperatures go abnormally high (like they are in some places these days) or low...there would be abnormalities in the rails.

Is there really any way to prevent these kinks under extreme temperatures...high....or breaks...low?

Thanks for any kind reponse.

.....a couple 200-ton locomotives at 60 mph cain't iron those li'l wrinkles out????

lowwater

Expnsion compenstors are routinely applied in bridge and piping construction.

I hope this is the only place I see one!

I thought cwr steel was formulated so that it expanded sideways or vertically instead of lengthwise.

The long lens used in the shot makes it look a bit worse than it is. I'm sure, though, that there would be some rough lateral movement of rolling stock. And at high(er) speed? Hmm...

Bill in Texas

As far as I know there is no way to internally control direction of expansion in steel ... all them little molecules are going to expand as the temp goes up. In general steel will expand a total of 1/64" of an inch per inch going from room temp to 2000 degrees in all dimensions. If you have ever seen a long billet or bar on a cooling table after rolling, you will see it getting shorter as it cools. As mentioned in prior posts you have to lay the welded rail at some neutral temperature ...preferably a high one so that the rail will seldom get a chance to expand against its normal position. By doing this you keep the rail under tension and it keeps itself straight and the occasional pull apart is easier to fix and/ or operate with. Our little tourist line has an unused segment about a mile long with no tieplates or spikes (vandals) on a real hot day the rail will bow out six feet in some places since the joints are all rusted tight.

ge13031 - As numerous people have stated in the various sun kink threads, a good quality track structure does indeed restrain the linear expansion of rails. This does not mean that stresses don't build up inside the (heated) rail, it just means those stresses are not relieved by the simplest stress-relief mechanism - linear expansion. Some of the linear stress build-up is relieved through cross-section expansion, but most has to be restrained by the track clip/ballast shoulder structure.

A sun kink can be considered the result of stress build-up to the point of the "composite" track structure failure (usually at some weak point in the ballast); stress build-up to the point of actual rail failure is something else.

Ray

Thanks, ge, and Ray, for the clarifications.

Yes, I recall tires on steam locomotive drivers are heated so they'll slip on the wheels relatively easily. I also recall (50 years ago) chilling some (small) motor rotors so their shafts slide into bearings. The bearings had previously been chilled so to slide easily into their housings.

The above expansions and contractions occurred in the easiest directions of the heated and chilled parts.

Bill in Texas

That almost looks like earthquake damage. That is one hell of a kink.

Doug Forness