Do heat kinks happen every summer?

I'm scheduled to take a #5 CZ from CHI-EMY departing this upcoming Saturday. This is my second attempt to ride this train, as my scheduled trip last year was cancelled by Amtrak when there was a track washout somewhere in Iowa. This year looks to not be much better, as I am concerned with the nationwide high temps this week and into next week causing heat kinks in the rail. I've heard about it happening before on #5, and I'm wondering if it's just something that's to be expected every summer. How much of a delay can this cause? Do trains every get completely cancelled because of compounding delays due to heat kinks? I'm really hoping I can finally take the train...

Heat kinks and pull-aparts are two sides of the same coin. They occur usually when a large temperature change occurs in a relatively short period of time. This causes a rapid contraction or expansion of the rail. If the rail has time to react so that the contraction/expansion is distributed evenly throughout a length of rail, then a kink or break does not usually happen. If the condition of the ties, rail anchors, ballast, etc... is insufficient, then the forces can be concentrated in one area, which might allow a kink or break.

Pull-aparts are usually not as much of a problem because once the rail breaks, the signal system will protect the train, as long as it doesn't happen right under the train.

In your case, if the temperature has remained high for several days, the rails should have had time to adjust to them.

Please chime in if somebody has more or better information.

jb

[edit] I should mention that this problem is usually associated with continuous welded rail, not jointed rail.

I say "don't sweat the potential rail problems due to excessive heat"

/pun off

Enjoy the ride. And be forewarned that the trainwill be very crowded. Take early meal sittings to assure the greatest menu selection.

Isn't there a technological solution by now to detect heat kinks and drop the signals to stop like a cold weather pull-apart would? I'd guess some kind of ultrasonic transducer to measure rail length.

MattW said:

Isn't there a technological solution by now to detect heat kinks and drop the signals to stop like a cold weather pull-apart would? I'd guess some kind of ultrasonic transducer to measure rail length.

Click to expand...

You mean like a shockwave produced at one end and received at the other, any deviation from a normal range in time is unacceptable? Doesn't the speed of sound change with temperature?

I was wondering if a heat kink could be detected by a change in the electrical resistance of the rail.

I'd wager that one of the detection companies is working on the problem.

jb

HEAT ? The rail is heated by the sun. One other item heating the rail is each axel causes deflection of the rail . Deflection = additional heat. So how much do the very long trains with axel counts to 1000 add additional heat temps ? ?

Is this what you all mean?

CCC1007 said:

MattW said:

Isn't there a technological solution by now to detect heat kinks and drop the signals to stop like a cold weather pull-apart would? I'd guess some kind of ultrasonic transducer to measure rail length.

Click to expand...

You mean like a shockwave produced at one end and received at the other, any deviation from a normal range in time is unacceptable? Doesn't the speed of sound change with temperature?

Click to expand...

I know it does in air because the air changes density with temperature, but I'm not sure about a solid object. Any mechanical engineers out there want to weigh in on this?

I'm not a ME, but logically it has to. When a block of metal expands in the heat, its volume changes, but it's mass doesn't.

Density of steel, like gases and liquids, varies with temperature. The absolute numbers would probably be irrelevant though, you would want to just look for dramatic changes. I doubt that economical monitoring technology would be available for sun kinks. You would need some very sensitive equipment to detect changes in rail length and the cost to deploy that over a large system would I think be much higher than the cost of slowing trains to look out for kinks a few times per year.

Sensitive electrical measurements on rails is a waste of time. Too many induced currents because of weather passing overhead, transients on nearby high-voltage power lines, medium-wave radio signals, etc. Rails are a great antenna. Just getting railroad signal systems to work reliably is a challenge.

I just thought of another problem with trying to electrically sense a sun-kink. The presence of the moving train could disturb the track a bit, thereby acting as a catalyst to allow the sun-kink to happen. But, at that time the train is already in the block - potentially distorting all electrical measurements.

Tough engineering problem.

jb