Eastern Railroad Discussion > Sun kinks and broken rails

In the summer when sun kinks occur, do they ever take a small section of rail out to cure the kink? If so, where do they cut the rail? Where the kink is, or at the closest rail joint? And if they do cut a section of rail out, does this make that section of track suspect for a broken rail in the winter? I have heard of track supervisors standing at a kink till the rail goes in the shade to see if that cures it.....Roadrat

Remember my pic at Summerhill? ... they could just put the spikes back in ... :-)

roadrat, the general principle on CWR is to lay it so it has no compression or tension at a temperature somewhere around 60 degrees F, I believe. If that is done properly, then at 100 degrees the compression forces are manageable and at zero degrees the tension forces are also manageble.

Usually, if a heat kink or "pull apart" occurs, there will be an attempt to make the repair with the right tension or compression in the new joint as dictated by the rail temperature.

Obviously, this doesn't always work so cleanly and problems arise. Particularly with "pull aparts", the cause may not be solely cold temperature but a combination of cold and a growing rail defect. Some of these breaks open up over a foot gap which makes pulling the rail ends back together to make a weld quite a chore.

Hot weather sun kinks can also be an indicator of lateral instability in the ballast.

There is a lot of "art" is this field, even today. Every year, the RR's are learning new and better ways of dealing with this problem.

Our MOW does cut out sections on a sun kink. They cut them out right at the sun kink. If you cut them out at an existing joint, you may have trouble with the holes if you need to cut too much off. If this is done right, there shouldn't be a problem with pull aparts or broken rails in the winter, but it is a possibility.

Xingman
http://home.internetcds.com/~xingman/

I have always seen CN CWR replacement work taking place on sunny days in the summer when the air temperature must be at least 80 degrees F, and the rail temperature may well be a lot warmer than that. The CN typically uses rail anchors on every other tie, and the ballast beds are substantial and maintained in good condition. I have never been aware of a cold weather (down to -30 degrees F) pull-apart in the areas that I pass by regularly.

Ray

The standard cure for pull aparts on CN isn't to pull the rail ends back together. Most times, the rail will be cut back from the break on both ends, leaving a gap of say 8-10 feet. Then drill for splice bars and slap in a piece of rail the same length as the gap. Usually they will leave the piece bolted in until spring rolls around, then they field weld it into place. I assume that cutting extra length out of the rail will reduce the tension that is bound to occur when the rail warms up again.

Mark

I can remember a Sunday on Sandpatch in 1990, when a sun-kink had a track on the mountain shut down, plus the heat also had an affect on the "armstrong" lever plant at Q Tower at the bottom of the hill. An inexpirienced operator at Q Tower was on the phone with SA Tower operator Pete Kelly trying to figure out something that he had to do with a locking pin not lining up in the switch machine at ground level beside the tracks. The poor guy at Q-Tower, knew the plant enough to throw the switches, but not how to trouble-shoot them. The Tylenol bottles were out that day..... ...Roadrat

Gee, I wonder how this works for tall buildings, roller coasters, that stand in the sun all day!!!

I think that it is an interesting exercise to compare photographs of modern CWR track with pictures taken fifty years ago. The CWR track will have plenty of shoulder ballast to provide lateral restraint and prevent sun kinks. In many of the old photos you will find little or no shoulder ballast.

Jointed rail had an expansion joint every 39ft so you could see the joints open in the winter and close in the summer.

NS seems to do a lot of their maintenance during the colder months. They lay rail, ties and ballast in the snow during December. We seem to have a lot more slow orders and other problems in the Spring and Summer than we used to. Somebody from NS told me that modern techniques prevent problems that used to occur. I can't see this happening on NS. They don't use Pandrol clips or similar anchors. I also think that steel is steel and will expand and contract the same in hot and cold weather.

Could NS operate this way because of their traffic patterns? On Conrail, our busy period was at this time of year. I think most coal gets delivered before it freezes, making it hard to unload. Plus, electricty is in more demand in the Summer with air conditioners running full blast, so I think that Spring and Summer are the peak times for coal. Maybe others familiar with these things will chime in.