I am no expert, but I know the RR’s have adapted a practice of attaching Rail Anchors to control the expansion. These are clamped onto the rail and are adjacent to the cross ties. My interpretation is that this causes the rail to expand vertically and become ‘fatter’ within the confines of the area between the ties.
Before this goes on too much further, consider the force restraining ‘buckling’ in the vertical plane, restricted by rail weight and fastening integrity to tie weight; force restraining movement in the longitudinal direction (controlled as noted by rail anchors and fastening including Pandrol clips when present); and lateral motion (tie friction; ballast end shoulders, etc.)
Yup.
Maybe not “vertically”, but “axially”.
Ed
And lack thereof.
Ed
Restraining track and rail buckling in every direction is used to constrain linear expansion of rail. But even if rail absorbs the expansion internally, its linear expansion force grows higher as the expansion absorbed within the rail increases.
At some point there will be buckling if the constrained expansion continues to increase. And once buckling happens, the force needed to move the track decreases as the track moves.
Just to keep things straight, may I offer these definitions:
sun kink: a rail dislocation caused by solar radiation
heat kink: a rail dislocation caused by heat input to the rail from the surrounding environment (includes solar radiation)
buckled track (or track buckle): a rail dislocation caused by any means
I do not see these phrases as interchangeable.
Ed
I regard heat kink and sun kink as interchangeable, alternatives. What do you call it if the sun heats the rail and then goes under a cloud when the rail buckles?
Buckling in engineering terms is more specific than just any structural failure. It means failure of a column or slender beam caused by axial compression.
In a sun kink or heat kink, I cannot think of any term besides “buckling” that better describes the kinking of a rail due to its linear expansion being constrained.
In a sun kink, the track structure besides the rails is not buckling at all. It is just being de
I know they do heat patrols/inspections on the lines I run when the temperature gets above 80F (I believe). I don’t think whether the sun is shining or not plays into that. Maybe I’m wrong? I never asked the MOW foreman that question.
It seems like there’s a lot of speculation and arguing back and forth over the probable cause in this thread.
For me, I was kinda hopin’ that someone would’ve had something more factual to report by now. I was checking online news services and this whole incident is kind of getting crowded out of the news already. I guess we’ll just have to wait for the official report to come out which could take weeks or even longer.
One thing about sun kinks, isn’t true that when the stresses are so high that a sun kink is imminent that it might not occur until precipitated by the vibration of the train passing over the weakness?
That’s what happened i
I was hoping and noticing the same thing. I suspect that when the investigation’s complete the mainline media will have moved on and forgotten all about it.
So, we’ll have to expect a report in “Trains” or possibly one of the professionals here will have learned what happened and pass it on.
Not being a professional railroader myself I’ve refrained from commenting on possible causes.
I agree that we have to wait. I hope we can be shown what the engineer saw (cab video) and hear his statement without waitng the 30+ days until the NTSB preliminary report. Then let the speculation recommence.
[quote user=“Fred M Cain”]
It seems like there’s a lot of speculation and arguing back and forth over the probable cause in this thread.
For me, I was kinda hopin’ that someone would’ve had something more factual to report by now. I was checking online news services and this whole incident is kind of getting crowded out of the news already. I guess we’ll just have to wait for the official report to come out which could take weeks or even longer.
One thing about sun kinks, isn’t true that when the stresses are so high that a sun kink is imminent that it might not occur until precipitated by the vibration of the train passing over the weakness?
That’s what happened in a sun kink in Tasmania as shown
If ya don’t want to speculate on the causes of this wreck, don’t.
If ya don’t like reading what other people speculate, don’t read it. You can either skip over that, or find a more entertaining topic.
If you think you should decide what other people should not talk about, I’ll make a note of it.
If ya just don’t like speculation, I do suggest waiting for the NTSB report. That’ll be about as good as it gets.
Ed
[quote user=“7j43k”]
Fred M Cain
It seems like there’s a lot of speculation and arguing back and forth over the probable cause in this thread.
For me, I was kinda hopin’ that someone would’ve had something more factual to report by now. I was checking online news services and this whole incident is kind of getting crowded out of the news already. I guess we’ll just have to wait for the official report to come out which could take weeks or even longer.
One thing about sun kinks, isn’t true that when the stresses are so high that a sun kink is imminent that it might not occur until precipitated by the vibration of the train passing over the weakness?
Euclid,
I didn’t quote you at all.
I cited you as previously posting the link that I posted.
All of my quotes are from the post by Fred M Cain. My responses are to him.
Ed
Oh, okay, thanks for clarifying that.
C’mon, SPECULATE! You know you want to.
Ed
Generally, forces restraining rail in the vertical direction are only relevant if the rail is going to buckle vertically (up-and-down), not laterally (side-to-side). I don’t believe I’ve ever heard of this happening. The cross-section of a 136# rail is such that the resistance to up-and-down buckling for a single rail is 7-8 times greater than it’s resistance to side-to-side buckling. That overcomes any of the other factors having to do with lateral or vertical restraint.
Just for the sake of being thorough (maybe event pedantic), I would point out that there is one other factor that contributes to resistance to track buckling, which is the rotational stiffness of the rail fasteners. In a track buckle, the ties normally displace laterally but don’t skew very much, while the rail obviously winds up with some sharp curves (hence the term “sun kink”). That means that, in the horizontal plane, the rail has to rotate relative to the tie. The fasteners may or may not resist this rotation. As Dr. Arnold Kerr put it in Fundamentals of Railway Track Engineering: neglecting the rotational resistance of the fasteners “may be justified for tracks with cut-spike fasteners that have been loosened by extensive traffic. It is definitely not the case for tracks with… [elastic fasteners].”
If you were to take this to the extreme - say, if you welded the base of the rail to a plate cast into a concrete tie - then the track structure would act more like a rigid frame and less like two se
Ed,
I agree with your synopsis and coverage of the Australian sun kink although I think it was actually in Tasmania. I think that Tasmania is actually a separate country from Australia although I’m not sure. Perhaps it’s just a province but it’s on an island separated from the mainland.
Anyhow, I read somewhere that trackwork had recently been done on that curve and the track hadn’t completely “settled” yet. Prbly they should’ve kept a 10 MPH speed restriction on it but that’s water over the dam.
In any event, I believe that particular line was later closed and today is out of service although the last I knew, no moves had been made to dismantle the line. There was a group fighting to get it coverted into either a commuter rail or light rail transit line but their efforts have as yet not succeeded.