Welded rail is a technology that the railroads have yet to MASTER in all of the various weather conditions. When I was working, the first cold snap of the season ALWAYS produced a high number of broken rails and pull-a-parts when it hit. Trains moving over the territory were constantly leaving on track occupancy indicators on CTC model boards all over the system - when Signals & Roadway investigated the track circuits they found broken rails and pulled apart rail joints. In unsignalled territory the signal maintainers got called out for crossing protection operating without the presence of trains.
When the heat would hit during the summer you would end up with Sun Kinks - and the signal system did not help identify them, they would have to be seen.
Never too old to have a happy childhood!
One must also consider the track bed. Back in the day, as I understand it, ties were only half-deep in the ballast - longitudinal support was less than we find today.
Nowadays, the ballast is kept right to the top of the ties, which helps keep the track in alignment, which is one reason that welded rail is forced to expand outward, as discussed.
Every now and then the expansion overwhelms holding ability of the ballast and you get one of those carnival ride kinks that show up occasionally on social media.
The slack in jointed rail may help deal with normal expansion, but provides than many more places where a pull-apart can occur. It just depends on which set of bolts fails first...
Larry Resident Microferroequinologist (at least at my house) Everyone goes home; Safety begins with you My Opinion. Standard Disclaimers Apply. No Expiration Date Come ride the rails with me! There's one thing about humility - the moment you think you've got it, you've lost it...
Dorango & Silverton NG had a sun kink a whil back.
Right now with the bitter cold pull aparts are becoming very prevelant.
Murphy SidingInteresting. You'd think the corrosion between the joint bar and the rail would be a pretty weak link that would let go pretty quickly when the rail grew or shrunk.
Do not forget that the joint bars are secured laterally with clamping tension by the bolts, which perhaps themselves are rusted so they don't self-loosen. The effect is to key the joint with corrosion, making it far more resistant to longitudinal motion, until some of the clamping force is relieved. This was commonly done by section crews in the days of more hands-on line maintenance, with reference to the crack of rail ends coming together when enough bolt tension on the bars was relieved.
The 'lubrication' Hay mentions is partially to prevent intercorrosion in the joint, partially to assure movement when the bolts are loosened.
the track structure lomits expansion and there was a discussion of welded rail vs jointed rail in at least one previous thread.
I remember that the total epansion in a given length of connected jointed rails is more than than in the same length of welded rail because the welded rail is forced to expand in width and height instead of length. The track structure limits longitional expansion and there are only two ends to expand instead of many.
I tried to sell my two cents worth, but no one would give me a plug nickel for it.
I don't have a leg to stand on.
Interesting. You'd think the corrosion between the joint bar and the rail would be a pretty weak link that would let go pretty quickly when the rail grew or shrunk.
Thanks to Chris / CopCarSS for my avatar.
A few years ago there was a picture in the magazine of a steam-era heat kink, which was offered as an exemplar of such behavior in jointed rail. According to the 1950 edition of Hay's Railroad Engineering text, joint bars could "freeze" to the rail from corrosion and thus not allow thermal expansion/contraction to be properly compensated for, thus resulting in kinks or pull-aparts. (As an aside, in another post today, Jeff Hergert noted a number of pull-aparts in and around his territory.) According to Hay, strategies to combat joint-bar freezing involved some form of lubrication.
It's that internet thing... 7 physical phenomena that cause derailments... #4 will amaze you!!!
I just never know what to expect on the other side of your initial posting...
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The February issue of Trains Magazine has a good article about the 7 physical phenomena that cause derailments... They tried to make the explanation straightforward but some things seem to have been glossed over a bit. Question- the part about sun kinks says that a mile of welded rail can grow 17" on the hottest days, causing potential problems. Were sun kinks not as big a problem with 39' stick rail? The way I figure it each bolt would have had at least 1/16" of play in order to get the bolt to slide through the hole. That would mean 1/8" of play every 39 feet, which equals 16.92 inches of *growth* before running into problems?
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