Semper VaporoThe track would 'tent' about 6 and a half feet from the ground in the middle.
Never took trig....
The corollary to that finding is therefore that the track would likely displace a similar distance horizontally.
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...
Flintlock76Selector had his tongue firmly planted in his cheek, just as I did when I mentioned "Diazinon Alley."
Overmod, thanks for the detailed explanation.
zardoz Flintlock76 Selector had his tongue firmly planted in his cheek, just as I did when I mentioned "Diazinon Alley." I'm so, and feel like such a.
Flintlock76 Selector had his tongue firmly planted in his cheek, just as I did when I mentioned "Diazinon Alley."
I'm so, and feel like such a.
Don't feel bad, there's jokes I don't get either from time to time, or don't get until an hour later.
The worst is when I read a joke and get it right away when I'm drinking a Coke! Ever shoot Coca-Cola through your nose? Agony, man, agony!
Flintlock76The worst is when I read a joke and get it right away when I'm drinking a Coke! Ever shoot Coca-Cola through your nose? Agony, man, agony!
Vernor's isn't much better. The worst part of getting a joke "later" is that the time is well past for any sort of witty reply...
The principle reason rail buckles laterally instead of vertically is that the stiffness ("Moment of Inertia") of the rail in the sideways direction is much less than in the vertical direction - something like 1/3 or 1/4, IIRC (can't find the exact values for any rail section for around both the X-X and Y-Y axis).
Even assembling 2 rails into a track - kind of like a ladder - doesn't make it all that much stronger in the lateral direction, as the rails are still free to slide over the ties, at least with spikes. Rail anchors or spring clips do add some more resistance. Otherwise, as to which way it'll go in theory is a contest between the weight of track (only) plus some vertical ballast resistance and the stiffer rail vs. the lateral resistance of the ties in ballast plus the effect of rail anchors and the weaker rail. As a practical matter all the kinks I've ever seen are horizontal. On the other hand, concrete highways usually buckle vertically (happened on Delaware Rt. 1 near Frederica this past Friday).
One reason that most observed buckling is lateral is the other factor that Overmod alluded to: If the track did try to rise vertically, as soon as it got up a little bit it would lose contact with the ballast beneath, and hence lose that source of lateral frictional and interlocking resistance. It would then be a lot easier to kink sideways, and then after that come back down. It would be interesting to see or read about a closely instrumented event of that kind to see what the exact motions and time/ speed of them are. That may have been done out at the TTCI or by some railroad's Test Dept., but I don't know of (or can't recall) it. I don't think it's a sudden sharp snap - though that could happen under a moving train - more like a couple seconds. Unlike a theoretical Euler column with a constant load, almost as soon as the track starts moving the compression is released and the force decreases, bringing it back into a new state of equilibrium at the deflected location pretty quickly.
- PDN.
With the application of closely spaced rail anchors doesn't this force the expansion, vertically by small increments, within the spacing between two anchors and thus mitigate the linear expansion?
Paul_D_North_Jr The principle reason rail buckles laterally instead of vertically is that the stiffness ("Moment of Inertia") of the rail in the sideways direction is much less than in the vertical direction - something like 1/3 or 1/4, IIRC (can't find the exact values for any rail section for around both the X-X and Y-Y axis). Even assembling 2 rails into a track - kind of like a ladder - doesn't make it all that much stronger in the lateral direction, as the rails are still free to slide over the ties, at least with spikes. Rail anchors or spring clips do add some more resistance. Otherwise, as to which way it'll go in theory is a contest between the weight of track (only) plus some vertical ballast resistance and the stiffer rail vs. the lateral resistance of the ties in ballast plus the effect or rail anchors and the weaker rail. As a practical matter all the kinks I've ever seen are horizontal. On the other hnd, concrete highways usually buckle vertically (happened on Delaware Rt. 1 near Frederica this past Friday). One reason that most observed buckling is lateral is the other factor that Overmod alluded to: If the track did try to rise vertically, as soon as it got up a little bit it would lose contact with the ballast beneath, and hence lose that source of lateral frictional and interlocking resistance. It would then be a lot easier to kink sideways, and then after that come back down. It would be interesting to see or read about a closely instrumented event of that kind to see what the exact motions and time/ speed of them are. That may have been done out at the TTCI or by some railroad's Test Dept., but I don't know of (or can't recall) it. I don't think it's a sudden sharp snap - though that could happen under a moving train - more like a couple seconds. Unlike a theoretical Euler column with a constant load, almost as soon as the track starts moving the compression is released and the force decreases, bringing it back into a new state of equilibrium at the deflected location pretty quickly. - PDN.
Even assembling 2 rails into a track - kind of like a ladder - doesn't make it all that much stronger in the lateral direction, as the rails are still free to slide over the ties, at least with spikes. Rail anchors or spring clips do add some more resistance. Otherwise, as to which way it'll go in theory is a contest between the weight of track (only) plus some vertical ballast resistance and the stiffer rail vs. the lateral resistance of the ties in ballast plus the effect or rail anchors and the weaker rail. As a practical matter all the kinks I've ever seen are horizontal. On the other hnd, concrete highways usually buckle vertically (happened on Delaware Rt. 1 near Frederica this past Friday).
What methods are most commonly use to prevent or mitigate? It would seem to be becoming a more likely occurrence.
diningcarWith the application of closely spaced rail anchors doesn't this force the expansion, vertically by small increments, within the spacing between two anchors and thus mitigate the linear expansion?
You still have the issue that the overall longitudinal force developed atomically by the thermal 'epansion' is developed, and while an increased number of anticreepers will 'subdivide' the force expressed by the corresponding subdivisions of rail length between anchors, the aggregate force will still be expressing on whatever the rail anchors bear against. Any weak point in the longitudinal resistance, particularly one that progressively weakens if perturbed, then becomes a place where 'something's gotta give'.
I suspect you will find that rapid release of even relatively short lengths of the expansion sends a shockwave along the rail that may help induce any other area(s) near the point of excursion into motion.
As noted, the provision of slab track along with good longitudinal 'anchoring' provides as good an immunity against lateral buckling as anything cost-effective. As noted, though, this introduces preferred vertical buckling as a failure mode, perhaps preferentially under or immediately after passage of a train. In my very humble opinion the chief issue here is not overt failure of the slab track, but a progressive working of the slab out of line and surface over time that would be very expensive to correct (unless you have explicit means for top-down rail adjusting while maintaining rigid longitudinal location integrity).
The correct approach to this remains periodic adjustment of rail length at the determined adjustment points between sections. I believe there have been articles in Trains that cover progressive improvements in theory and practice over the years as field-welded extreme LWR with modern rail metallurgies have been implemented.
charlie hebdoWhat methods are most commonly use to prevent or mitigate? It would seem to be becoming a more likely occurrence.
It is a common misbelief that the force of expansion is irresistible, and thus cannot be stopped. Yet steel rail is elastic. It can be stretched like a rubber band and then when the stretch force is relaxed, the rail will return back to its original length.
Likewise, rail can be compressed lengthwise so it becomes shorter, and when the compression is released, the rail will rebound to its original length.
It is this lengthwise compression that leads to sun kinks. Although rail can be compressed, it does push back against that compression just like compressing a coil spring. The pushback tends to buckle the rail into sideways loops that take up the extra length of expansion. But if you can physically contain the rail side-to-side against that buckling pressure, the rail will compress to absorb the extra length of expansion without being able to buckle. That side-to-side constraint is the role of ties and ballast.
But if even though the rail can be prevented from getting longer or moving side to side, thermal expansion will exert forces lengthwise and sideways as a reaction to the lengthwise force being restrained. And if those sideways forces on the rail find a weak spot in the rest of the track system, they will form sun kink as a reaction.
However, if thermal expansion were indeed an irresistible force, we would see sun kinks and pull-aparts of welded rail every time the temperature changed.
You are correct in stating that steel will compress, the opposite occurs when the track drops below the neutral temperature and the cross section thins as the rails go into tension. The problem with compression in a long thin structure is that it is not stable with respect to buckling, the solution for another "long thin structure", radio towers, is the use of guy wires. A similar approachcould be taken with track, where the track is connected to anchors (which would have to be massive) on each side by steel cables, but I doubt if would provide much of a benefit. When rails are under tension, the tensile forces tend to restore any deviations from straight - think "pushing" with a rope versus pulling.
The early descriptions of CWR mentioned that the rail should be laid on one of the hotter days of the year (i.e. high neutral temperature) to have it stay under tension for the vast majority of the year. The problem is that in areas of extreme summer/winter temperature shifts, the rails will pull apart at a weak point, so a compromise needs to be made between sun kinks and pull aparts.
The forces involved with temperature change in rail get big. For those who like math the equation is this.
Change in Force = Cross sectional area of the rail x 200 x Change in temperature
136# rail has a cross section of 13.35 sq in, the 200 is a thermal force constant to make the answer end up in pounds of force and temperature is in degrees F. A 1 degree rise in rail temperature increases the force in the rail by about 2670 pounds.
The temperature here is rail not air temperature. Rail temps can get up to 130-140 degrees on a hot day, but generally will not go above that no matter what the air temp is. It is the temperature differential (lowest low to highest high) over a year that determines what the desired neutral temperature (DNT) for laying rail is. Each road sets this themselves. It can be 85 degrees for North Dakota or 105 for Arizona.
What resists this change in force are the ties, fastenings and ballast that make up the rest of the "system" of the track structure. The bottom of the tie/ballast interface provides about 50% of the resistance and the sides and shoulders split up the rest.
Properly laid and maintained CWR track will have a well graded, sharply angular, clean, heavy, well compacted ballast with at least 1' wide shoulders and a minimum of about 12" of rock under the tie. The subgrade will be well compacted and well drained. The ties and fastenings (spikes or elastic fasteners, plates, anchors, etc) will be in good condition and properly applied.
The "well compacted" part is critical. Doing work on the track at the extremes of temperature ranges can mess this up and lead to slow orders until the track structure is tightened up again.
The system has to work together properly and has to be inspected properly to ensure any potential defficiencies are caught before they can create a problem. Get to know and love your local track inspector.
The table I posted in the 3rd post on the first page of this thread is what one Class 1 uses as its 'formula' for rail expansion in differing temperature. It state the nominal 'normal' temperatures for rail being laid. The temperatures shown at the top of the table are not ambient temperatures but the change in temperatures.
Never too old to have a happy childhood!
That happy median/ rail neutral temperature is a balancing act that is a serious art (& science) form to get right by the M/W folks in the field that know the materials they have to work with.
While sun kinks and pull-aparts can happen anywhere, curves seem to create most of the problems - usually caused by surfacing operations that may have happened months or years before (nature of the beast with surfacing machinery, especially the track liners, plus rail anchors that are never enough and are wearing out in a holding/friction sense)...taking what Paul & Steve already very well tried to explain, when you see rail trying to lift up off the plates, getting snaky or showing evidence of lateral movements... out comes the welders and the section gangs trying to reduce pressure by removing rail. With CWR, you do not have the visual evidence of the rail gap closing up and a trail of broken bolts, but you sure can see that the compressive forces are at work in the track system.
Before all the FRA rules and the science of track expansion was better explored, most roadmasters in the summer when dealing with rail getting snaky or out of the plates (surfacing gang or just track heating-up) used to keep a few cars of ballast around that were watered-down in the cars during hot spells for dumping up to the top of rail ("plugging") to cool the rail off and keep the sun off most of the rail.. Doesn't work anymore - with fewer ballast cars and allowance for ballast in the budget having been curtailed (no excess allowed, no wide ballast shoulders - even in the curves))
(If that pull apart in winter happens in signal territory, you have some protection. Much less in dark territory. Some folks gamble and place the emphasis on protecting against sun kinks to the detriment of protection against pull-aparts. Signal system is no help in the heat and the heat plays hell with proper adjustment of switches around the points and stock rails.)
Flintlock76 Organophosphorus compounds. The first things I think of when I see the term are "Tabun," "Sarin," and "Soman." Scary stuff indeed! Although I do know they had their origins in insecticide research. Anyone remember chlordane? Dad used it around the house to kill bugs and swore by the stuff. Dad ALWAYS followed the directions for its use and never had a problem with it. Too bad a lot of people didn't, it was a good product.
Organophosphorus compounds. The first things I think of when I see the term are "Tabun," "Sarin," and "Soman." Scary stuff indeed!
Although I do know they had their origins in insecticide research.
Anyone remember chlordane? Dad used it around the house to kill bugs and swore by the stuff. Dad ALWAYS followed the directions for its use and never had a problem with it. Too bad a lot of people didn't, it was a good product.
I remember chlordane! It was indeed good stuff. My father wouldn't let us kids anywhere near it. I also remember a mixture of 2,4-D and 2,4,5-T with a little dishwashing liquid; pretty close to the dreaded Agent Orange, but would kill honeysuckle vines graveyard dead, and was about the only thing that would. That and hungry goats, or VERY hungry cows.
Proper use is the key. It seems that a lot of homeowners use enough herbicide to turn their lawns into a hazmat site as bad as some industrial sites near my old neighborhood.
CSSHEGEWISCHProper use is the key. It seems that a lot of homeowners use enough herbicide to turn their lawns into a hazmat site as bad as some industrial sites near my old neighborhood.
Based upon the basic human thought process - 'If a little is good, more is better.'
I just read in my local newspaper that due to the record breaking heat wave currently passing through Europe, many communities in Germany, Switzerland, and Austria are painting the rails white on vital rail links, hoping the extra reflectivity will reduce the amount of heat the rails absorb, to avoid damage to the rails.
I understand the reflectivity of white concept, but is this significant enough to actually protect the rails from kinking?
Convicted One I just read in my local newspaper that due to the record breaking heat wave currently passing through Europe, many communities in Germany, Switzerland, and Austria are painting the rails white on vital rail links, hoping the extra reflectivity will reduce the amount of heat the rails absorb, to avoid damage to the rails. I understand the reflectivity of white concept, but is this significant enough to actually protect the rails from kinking?
In any case, it would be interesting to see the technical details of how it is working.
One other thought: Ties and ballast will also absorb thermal radiation from the sun. They, in turn, will heat the rails by direct contact through the heat transfer means of conduction. Hot ties and ballast will also heat air by conduction, and it will rise up around the rails and heat them by the heat transfer means of convection. And any heat transfered to the rails by conduction or convection will not be mitigated at all by painting them white.
Convicted OneI just read in my local newspaper that due to the record breaking heat wave currently passing through Europe, many communities in Germany, Switzerland, and Austria are painting the rails white on vital rail links, hoping the extra reflectivity will reduce the amount of heat the rails absorb, to avoid damage to the rails. I understand the reflectivity of white concept, but is this significant enough to actually protect the rails from kinking?
When it is the only thing you can afford in a TIMELY fashion it is the only play you can make. Doubt it's effectiveness, but if it saves one derailment it will have more than paid for itself.
BaltACDWhen it is the only thing you can afford in a TIMELY fashion it is the only play you can make. Doubt it's effectiveness, but if it saves one derailment it will have more than paid for itself.
I'm thinking that someone on this side of the pond tried that a few years ago.
The opinions expressed here represent my own and not those of my employer, any other railroad, company, or person.
zugmannBaltACD When it is the only thing you can afford in a TIMELY fashion it is the only play you can make. Doubt it's effectiveness, but if it saves one derailment it will have more than paid for itself. I'm thinking that someone on this side of the pond tried that a few years ago.
I believe you are right and I believe there was no definitive evidence that it worked.
There are people advocating laws requiring urban roofs to have white shingles to stop climate change. That too is dubious as to its effectiveness, I think. So this painting things white to keep them cooler seems to be a bit of a fad.
To use finishes to keep rails cool is doable, but it will take a very sophisticated approach. The cost would be astronomical. You can't just go out with a bunch of laborers and mop a bunch of white paint like whitewashing a fence.
Euclid White paint on rails will get dusty and grimy. ...
Iron worn off the rail head will also streak the white paint with rust orange (iron oxide) and yellow (iron hydroxide).
Go out in the sun and put your hand on a black car and then on a white car.
Go out in the sun in a black shirt, then in a white shirt.
Or you can reverse the order if you want.
_____________
"A stranger's just a friend you ain't met yet." --- Dave Gardner
Paul of Covington Go out in the sun and put your hand on a black car and then on a white car. Go out in the sun in a black shirt, then in a white shirt. Or you can reverse the order if you want.
Not disputing the temperature differences between white and black in direct sunlight.
However, the painted surfaces of ral to get 'direct' sunlight will be the web of the rail at shortly before sunrise and shortly before sunset. The base of the rail will get the most sunlight during the day as well as the tie plate - are the base and the tie plate being painted, what about the nominally black crosstie where wood is in place.
What is the effect of the elastometric tie plate cushion used in concrete tie installations on securing the rails under high ambient temperature conditions.
Convicted One I understand the reflectivity of white concept, but is this significant enough to actually protect the rails from kinking?
Considering that most of the heat added to the rails in direct sunlight is coming from the sunlight itself, the reflectivity can make a big difference. There is a subtle point as a good fraction of the heat going out of the rails is through radiation and that is affected by the emissivity, which is equal to (1 - reflectivity) at the wavelength in question. White paint can be good as it reflects visible light and near infrared, while being a strong emitter at far infrared. A polished metal surface can be much hotter than a white painted surface due to the polished metal being highly reflective at far infrared and thus a poor emitter.
With Europe being at a higher latitude than most of the US, the sun would striking the rails at a lower angle and thus painting the web would have more of an effect.
BaltACD only play you can make
That is akin to what I finally concluded. Even if it's effectiveness is only 1/2 of one percent, it is worthwhile if that 1/2 of one percent was what kept the rail from buckling.
I once rode on the CNO&TP and recall that track had what appeared to be large rail expansion joints about every mile or maybe less. These were big mechanical contraptions that appeared to allow the rails to slide past each other kind of like two swtich points opposing each other. The rail slip conection was housed in a heavy frame maybe a foot wide and 8 ft. long at least. They seemed to have a lot of parts. I have never seen those anywhere else.
Erik_Mag There is a subtle point as a good fraction of the heat going out of the rails is through radiation and that is affected by the emissivity, which is equal to (1 - reflectivity) at the wavelength in question
So too is that layer of paint a barrier to heat trying to escape from the rail, is it not?
I recall discussion pertaining to the inadvisability of painting air cooled engines for that reason. I realize that comparison has an apples and oranges aspect since the engine is an internal heat source, but still I would expect the paint applied to the rails would still present a barrier to heat trying to escape, say during the passing of clouds obscuring the sun from time to time.
Air cooled engines as the name implies, are cooled by convective heat transfer between the fins and the air along with some radiative heat transfer. For large engines with a lot of air flowing through the fins, e.g. airplane engines, paint on the fins would be detrimental to cooling as almost all of the cooling is convective heat transfer. For a small engine with little or no induced airflow, e.g. lawnmower, the cooling would mostly be radiative heat transfer, so paint may actually help if it increases emissivity.
I suspect heat loss from rail would mostly be radiative heat transfer, so paint might help with increasing emissivity. The main effect is decreasing the amount of solar energy absorbed by the rail.
Our community is FREE to join. To participate you must either login or register for an account.