What causes heat kinks and other track problems?

SGP posted:

Anytime I have heard of heat kinks it seems to only  happen on long straight sections of right of way. Is this necessarily the case or can heat kinks occur on curved sections of railroad also?

Yes, in fact curves are more vulnerable.

What about other kinds of damage from weather such as water damage? Is serious flooding needed for washouts along a railroad right of way or can it happen from culverts and small bridges? Are some right of ways built better to handle water coming up to the rail before serious damage occurs?

Washouts can occur at very small bridges or culverts if they get plugged up with debris and cause water to flow across the track instead of under the bridge.  Certainly a generous amount of heavy ballast and a wide ballast shoulder give track a better chance of withstanding flowing water as well as track buckling (sun kinks).

Heat kinks happen because different materials expand and contract as the temperature changes, at different rates.    In the case of real track, the earth/roadbed does not expand as much as the rail which absorbs heat from the sun more readily and expands, while the foundation it is sitting on does not expand as much or at all.

I always wondered why continuous welded rail doesn't have these problems.

bob2 posted:

I always wondered why continuous welded rail doesn't have these problems.

It does.  You must have been misinformed.  It's much more vulnerable to track buckling than jointed rail.

Three factors can limit vulnerability:

1. A generous amount of good quality, clean ballast and wide shoulders (one or more feet of level ballast outside the edge of the ties before the slope begins).
2. Installing Continuous Welded Rail at the proper atmospheric and rail temperature.
3. Reducing the maximum speed of trains when ambient temperatures are very high.*

Jointed rail can absorb a little more expansion and contraction than welded rail can, although it also requires the same ballast standard as CWR.  If a piece of CWR requires replacement and temperatures are not within the proper range, then MofW will cut out the defective section and insert a new one with bolts and angle bars.  Later, when temperatures permit, the bolts and bars will be removed and a thermite field weld will be done.

During periods of high temperature, visual on-track inspection by a qualified Maintenance of Way employee in a track car or Hy-Rail is essential. The frequency depends on the traffic level, but will be at least once per day.  A Track Inspector who knows his territory can spot trouble before it results in buckled track.  He knows the best and worst spots on his territory.  There is always at least a slight amount of risk, but it can be prudently managed so as to be very slight.

*  In some territories where high temperatures are likely to occur, defect detectors broadcast the ambient temperature in addition to other information, and the railroad's Special Instructions instruct crews to adhere to specific speed reductions based on temperature and type of train.

This topic addresses questions I have always had, but never researched the answers.  How could  AT&SF could maintain 79 and 90 mph speeds through the Mojave or other brutal areas where the temperatures soar and plummet.  And on an unrelated note, how enginemen could hack it in the steam era (or in un-air conditioned diesels) through that region?  I also ponder about people snaking in Barstow yard or Needles in the height of summer. They have to be the toughest of hombres.

Agreed.  I can't handle much more than 85 degrees.  Fortunately, I live two miles from the Pacific.

I was based in Phoenix for a while.  Took two minutes to walk around a 737; three minutes in the same heat to deep-fry my brain.  And don't touch anything shiny!

Rail is amazingly flexible.   The expansion/contraction is predictable, coefficient of linear expansion.  

Continuous Rail pictured date, 1966. 

Back in the mid 80's, I worked on a track gang installing 1/4 mile lengths of ribbon rail.  After the rail is laid, spiked down, and and joints welded, a "rail burner" comes along heating up the rail with propane burner hood directing the flames at the steel rail.  The steel rail expands, of course.  A few miles down the line, where the gang plans on tying up for the night, the new ribbon rail is cut about 3' short of the existing rail.  As the burner moves towards the tie-up point, that 3' gap is slowly shrinking until the burner finally gets there, at which point the gap is down to 1/4" or so.  Incredible!  I actually stood there on more than one occasion and watched a 3' gap shrink down to nothing.  The ribbon rail is then quickly secured to the existing rail, either by drilling and bolting with splice bars, or by welding.

Mile after mile after mile, ribbon rail is under constant tension.  During a long, hot summer, if the heat of the sun warms the rail to a point hotter than what the rail burner got it, then the rail will start surpassing the rail burner expansion point and can start buckling and kinking.  Curved sections of track are a little more resistant to buckling and kinking, because they can expand outward of the curve to a small degree.  But long straight sections of track?  Forget it!  There's nowhere for the steel rail to move except sideways and/or up & down. 

In the late 1970's there was an article in Model Railraod Craftsman.  Somebody had a 2R O gauge outside layout.  This layout had heat expansion issues.  So every so often, one of the rails would have a 45 degree bend to the outside.  The next section of track would be butted up against it.  On the opposite rail, there would be a guard rail.  The idea was if the track expanded or contracted, the rail tail would take the abuse, not the rail used by trains.

Have the real railroads considered this?  Might work in places where the rail has a tenancy to buckle?

I appreciate all the answers. If anyone does have any sources that breakdown track conditions I would be interested. It seems like if the climate of a region can possibly impact heat kinks, an area where there is less coverage from trees (be it desert or just a less wooded area) would be significantly more at risk of heat kinks than a route that is running along forests that may shade it a bit.