Returning to flat wheels.
From other railroader's posts there seems to be a problem between those responsible for track and those responsible for locos and cars & operating departments. The wheel impact damage to track "MAY" be very important or may not. It seems that there needs to be a section of isolated real world trackage that can be equipped with "WILD" ( wheel impact detectors ). Those should be close together and just past any locations where braking will be used. Break test area into two sections with one section no replacement to the flat wheels and the other section requiring any flat wheel cars to be immediately replaced before entering the section. Probably require more car repair persons .
Then have frequent rail inspections done on each section and see what has happened to the rail. Then maybe any flat wheel replacements / truings / brake system repairs can be charged to special category of rail preventative maintenance. ( a separate cost center ). Of course most of these charges will go to the car owner but RR owners can charge this to the above mentioned PM category.
Does anyone know if the proposed ECP brake systems could reduce flat wheels and immediately detect them if one occurrs ?
A problem with setting out flat wheel cars that might occur is the operating departments would not like having to stop trains more often to set out cars with flat wheels. This can have effects on those long distance crew districts causing more dog catch crews..
schlimm Say all you want, blind us with your equations, the fact is that other sources more expert than you say something else.
Say all you want, blind us with your equations, the fact is that other sources more expert than you say something else.
From my interaction with Paul North, he seems to have a pretty good undertsanding of stress/strain response of structures, interactions of wheels and track (e.g. his bringing up the Boeing Vertol test track with the worst case SF Muni track in another thread) and at least some knowledge of dynamics. He has enough knowledge of the subject to be in the position to ask substantive questions of the "experts". IOW, he would be in the position to do a "peer review".
The TSB investigator has work experience with railroads, so it is reasonable to expect that his comments about what may be causing rail damage leading to derailments would be "expert opinion". What I've read so far comes across as a hypothesis, which is not yet backed up by firm data. It's possible that he may be thinking about the sloshing problem in the SDP-40F. Based on comments made on the forum and my own experience, "sloshing" does not seem to be a likely cause for the track damage, but there may be other aspects of a tank car that could be the source of the track damage.
The comments from the FRA appear to have come from the administrative level and not from the technical level. The experience with the Gold King mine suggsts that it is unwise to presume competence of regulatory personnel (to be fair, it would also be unwise to presume incompetence of regulatory personnel).
What Paul was saying about flat wheels is that they are known to produce very high impact forces on the rail, which are well in excess of the forces transmitted to the rail by the dynamics of main body of the car and load. It is a poor reflection on the RR industry that it took so long to recognize the economic loss from flat wheels.
The IEEE article doesn't refute comments about sloshing being a non-issue, if the liquid is viscous enough so that viscosity drag has to be taken into account in calculating forces inside the tank, then it will be too viscous to be sloshing.
schlimmSay all you want, blind us with your equations, the fact is that other sources more expert than you say something else.
No need for e pur si muove here. I doubt you will find any credible source that actually could demonstrate that sloshing at the top of filled oil-train cars is actually causing real-world derailments. But the flat wheels, that's something else again, and you would not be crying in the wilderness to point that out as a potential source. Part of it may have to do with rails after all.
Go to that issue of Interface Journal that wanswheel linked to in the oil-train track defect thread ...
http://interfacejournal.com/archives/category/wheelrail-profile-design
... and look again at the part of the article regarding hardened rail. I noted that all the references to fatigue in that section seem to involve RCF rather than impulse stress. My understanding of steel metallurgy was in part that increasing hardness to the levels being mentioned for HAL wear reduction, through the full extent of the head, would increase the relative brittleness. I find it plausible that this rail, particularly if at low ambient temperature and already being repetitively loaded by standard-diameter wheels to HAL levels, might be more susceptible to impulse damage than older rail ... and that the damage would take the form of major sudden rail breakage under the train when it did.
I do remember that in an Amtrak test of an Acela trainset, an IWS recorded in excess of 179g peak acceleration. I have to wonder if a sufficiently flatted wheel would produce the same effective result either banging down onto the flat or back up onto the undamaged tread, particularly soon after the 'flatting' event when the two 'shoulders' adjacent to the flat are still relatively sharp.
I have noticed that coal train consists running through Memphis are evidently CAREFULLY monitored for flat wheels, and when found they are replaced or trued, as it is unusual to hear even a couple of sets (and even then, usually just a light ticking to tapping). The same is generally true of the larger-diameter intermediate truck wheels in articulated stack-train sets. I think it is well understood in some professional circles that HAL consists need more than usual care to avoid flat-wheel operation, whether or not there is some seven-car replacement rule for more 'ordinary' cars. It might be interesting to see whether that understanding applied to unit ethanol or crude-oil trains prior to the rash of derailments ... or now applies and is at least partly responsible for the seeming relative absence of such derailments recently.
Say all you want, blind us with your equations, the fact is that other sources more expert than you say something else. Denial runs deep: what doesn't damage rails? Some have said cold weather doesn't cause damage or heavy unit trains or sloshing of liquid contents or other unbalanced characteristics of tank cars or flat wheels (obviously it is an accumulation of being struck by not uncommon flat wheels, especially heavy trains). But they must be right and the TSB, etc. are obviously wrong. Meanwhile, rails get damaged to the point of failure leading to derailments.
C&NW, CA&E, MILW, CGW and IC fan
Euclid [snipped - PDN] . . . What is being insisted on with an almost religious intolerance, however, is that derailments cannot be caused by this means. For this assertion, it is reasonable for the agnostics to demand proof, and yet none is provided.
For that magnitude of weight to be concentrated even on one truck = 4 wheels at the end of a car would require an impact-caused longitudinal deceleration (or acceleration) of about 2-1/2 times the force of gravity: 1/2 the weight of the car, times the truck centers of the car (say 50 ft.), divided by the height of the center of the tank cylinder (say, 10 ft.) [summation of the rotational moments = 0].
Further, to then reach that cited 140K force on any 1 wheel - to quadruple it from the above state - would require a further impact of 4 g's. So a total deceleration of about 10 g's would be required. That's not encountered anyplace on earth short of a NASA rocket or a high-differential-speed vehicle collision airplane crash, etc.) - not even earthquakes reach that amount of acceleration in any direction. Railcar lading impacts - of solid objects - usually max out at 3 to 4 g's. Impact loads on steel bridges are only 1.7 times the static loads, or 1.7 g's.
Until someone can show me where railcar impacts can reach 2 to 3 times the max. typical - 10 g's in other than a derailment or collision already underway - or about 6 times the generally accepted static load - I'll remain a skeptic.
Further I sayeth not.
- Paul North.
traisessive1Yeah guys, there is something wrong with your train. I think I heard a round wheel. You might think that's a joke, but, it really isn't. I'm sure there are more flat wheels out there than there are round ones.
You might think that's a joke, but, it really isn't. I'm sure there are more flat wheels out there than there are round ones.
schlimm Euclid schlimm If you want to do so, go ahead. I posted the study because sloshing is not so simple as to be dismissed with the sneaky, pejorative comment PDN made. As I mentioned above, nobody is insisting that it is absolutely true the tank car load shifting is causing or has ever caused a derailment. If anyone were insisting that is true, it would be incumbent upon them to prove it. What is being insisted on with an almost religious intolerance, however, is that derailments cannot be caused by this means. For this assertion, it is reasonable for the agnostics to demand proof, and yet none is provided. True. And the rather lame attempt at a vulgarity disguised as a simple word of dismissive derision is sad. "the repetitive insistence on the sloshing theories is BoguS " [his caps, my bold] Why not just have the guts to say it?
Euclid schlimm If you want to do so, go ahead. I posted the study because sloshing is not so simple as to be dismissed with the sneaky, pejorative comment PDN made. As I mentioned above, nobody is insisting that it is absolutely true the tank car load shifting is causing or has ever caused a derailment. If anyone were insisting that is true, it would be incumbent upon them to prove it. What is being insisted on with an almost religious intolerance, however, is that derailments cannot be caused by this means. For this assertion, it is reasonable for the agnostics to demand proof, and yet none is provided.
schlimm If you want to do so, go ahead. I posted the study because sloshing is not so simple as to be dismissed with the sneaky, pejorative comment PDN made.
If you want to do so, go ahead. I posted the study because sloshing is not so simple as to be dismissed with the sneaky, pejorative comment PDN made.
True. And the rather lame attempt at a vulgarity disguised as a simple word of dismissive derision is sad. "the repetitive insistence on the sloshing theories is BoguS " [his caps, my bold] Why not just have the guts to say it?
You point out that the fluid dynamics of "sloshing" is complex. I agree. The complexity is not only in the analysis, but in the subject of it. The motion would be extremely turbulent to produce anything near the effects claimed or speculated, which would likewise greatly dissipate any such forces. Any purported analysis of that complex motion will be mere circular reasoning, reflecting the input assumptions.
This post went to Hell, Michigan.
If you want to do so, go ahead. I posted the study because sloshing is not so simple as to be dismissed with the sneaky, pejorative comment PDN made. Perhaps in more cylindrical tanks no sloshing takes place. I really do not know. It's probably a moot point in regard to tank cars anyway.
Due to the drop in oil prices, oil companies have cut back the exploration side greatly. Several smaller exploration companies are gone. Shell has earlier abandoned exploration in the Arctic and the tar sands. Chevron's refining side is doing well but other components not so cutting 6-7,000 jobs, many in Houston. Since the downturn worldwide, ~200,000 jobs lost. Most oil 'experts' (I realize that on this forum, outside expert opinions are often not accepted) see the price of oil remaining in the $40-50 range for several years, due to lower demand. Of course that is speculation, but informed speculation. I wonder when we will start seeing reports of oil tank cars parked in storage?
schlimm Paul_D_North_Jr Compared to that, anyone with knowledge and/ or experience in the physics/ dynamics of railcars should recognize that the repetitive insistence on the sloshing theories is BoguS. - Paul North. http://ieeexplore.ieee.org/xpl/login.jsp?reload=true&tp=&arnumber=5367190&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D5367190 Not so simple
Paul_D_North_Jr Compared to that, anyone with knowledge and/ or experience in the physics/ dynamics of railcars should recognize that the repetitive insistence on the sloshing theories is BoguS. - Paul North.
http://ieeexplore.ieee.org/xpl/login.jsp?reload=true&tp=&arnumber=5367190&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D5367190
Not so simple
Especially when you are dealing with almost completely-filled tank cars where the 'hydrodynamic drag' (by definition from moving fluid) would be limited to the volume of fluid that actually moves. Did you actually read Mr. Zhang's paper, or look at the assumptions?
Since many of the posters here won't be able to read papers from IEEE, here are the references from the paper, for anyone who wants to check some of the physics involved:
http://web.itu.edu.tr/~mscelebi/documents/ocn_serdar.pdf Liquids sloshing are far more complex than one would imagine. For only partially filled, rectangular-cross-section tank cars. Which the people PDN was talking about, "anyone with knowledge and/ or experience in the physics/ dynamics of railcars", will recognize as being atypical of loaded North American HHFT consists, in very important physical ways. Perhaps you will be so kind as to demonstrate, with proper mathematics, how to apply the methods in the two papers you cite to cylindrical tank cars filled to normal loading volume? As an interesting added note, the two Turkish naval-architecture guys observe this, which I suspect Euclid may find interesting if he hasn't yet downloaded and read the paper: Sloshing is not a gentle phenomenon even at very small amplitude excitations. The fluid motion can become very non-linear, surface slopes can approach infinity and the fluid may encounter the tank top in ... enclosed tanks. The key question would appear to be whether there could be small resonant excitation in the carbody motion that would excite the comparatively small region in the tank where there can be harmonically-excited fluid motion into 'sufficient' complex motion to produce substantial impact/momentum force (or perhaps drag force?) on a meaningful percentage of the car structure.
http://web.itu.edu.tr/~mscelebi/documents/ocn_serdar.pdf Liquids sloshing are far more complex than one would imagine.
For only partially filled, rectangular-cross-section tank cars. Which the people PDN was talking about, "anyone with knowledge and/ or experience in the physics/ dynamics of railcars", will recognize as being atypical of loaded North American HHFT consists, in very important physical ways. Perhaps you will be so kind as to demonstrate, with proper mathematics, how to apply the methods in the two papers you cite to cylindrical tank cars filled to normal loading volume?
As an interesting added note, the two Turkish naval-architecture guys observe this, which I suspect Euclid may find interesting if he hasn't yet downloaded and read the paper:
Sloshing is not a gentle phenomenon even at very small amplitude excitations. The fluid motion can become very non-linear, surface slopes can approach infinity and the fluid may encounter the tank top in ... enclosed tanks.
The key question would appear to be whether there could be small resonant excitation in the carbody motion that would excite the comparatively small region in the tank where there can be harmonically-excited fluid motion into 'sufficient' complex motion to produce substantial impact/momentum force (or perhaps drag force?) on a meaningful percentage of the car structure.
Well around here it certainly is.
10000 feet and no dynamics? Today is going to be a good day ...
traisessive1 Yeah guys, there is something wrong with your train. I think I heard a round wheel. You might think that's a joke, but, it really isn't. I'm sure there are more flat wheels out there than there are round ones.
Yeah guys, there is something wrong with your train. I think I heard a round wheel.
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...
Paul_D_North_JrCompared to that, anyone with knowledge and/ or experience in the physics/ dynamics of railcars should recognize that the repetitive insistence on the sloshing theories is BoguS. - Paul North.
http://www.illinoisgreens.org/SpeedandSloshing.html FRA and former head of NTSB are ignorant?
http://ieeexplore.ieee.org/xpl/login.jsp?reload=true&tp=&arnumber=5367190&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D5367190 Not so simple
Never too old to have a happy childhood!
S. ConnorImagine how far that incomplete wheel went, banging along the rails unnoticed...
Probably between there and the last WILD?
It's been fun. But it isn't much fun anymore. Signing off for now.
The opinions expressed here represent my own and not those of my employer, any other railroad, company, or person.t fun any
Paul_D_North_Jr Compared to that, anyone with knowledge and/ or experience in the physics/ dynamics of railcars should recognize that the repetitive insistence on the sloshing theories is BoguS.
Compared to that, anyone with knowledge and/ or experience in the physics/ dynamics of railcars should recognize that the repetitive insistence on the sloshing theories is BoguS.
It was the FRA that introduced the theory.
There are two sides to the argument. One side suggests the possibilty without proving it. The other side insists that the theory is impossible and they don't prove that. Which side is the least credible?
I'm not suprised that there are so many flat-spotted wheels out there. Many crews sadly do not check for severe flatness in the first place.
A Strasburg RR employee once told me of a friend of his who woked for another railroad. He called to say that he had found a wedge of a freight car wheel! Much like a piece of pie. More to the suprise of both, a car came into the Strasburg yard a couple of days later, with a chunk missing, much like a pie. The two met up, and yes, it was a match!
Imagine how far that incomplete wheel went, banging along the rails unnoticed...
From oltmannd above: "After sufficient work was done to show that it really was a good idea to fix high impact wheels, . . . ".
"On this point a page of history is worth a volume of logic." - Justice Oliver Wendell Holmes, Jr., of the U.S. Supreme Court (back in the 1920's or 30's).
Procedural point: Compare and contrast the learned, scientific, and well-researched and analyzed discussion on this subject in the references I linked to above, with the speculation (nicest word I can use) in another thread here about "sloshing" in the oil tank cars causing rails to break. (Note for those who don't know: A "kip" is shorthand for "KIloPound" = 1,000 lbs.; hence 100,000 lbs. = 100 kips.) Some of the values and thresholds in those references - like individual wheel impacts above 140 kips (about 2x the normal static load) are enough to require stopping the train and setting out the offending car ASAP - are quite informative. Compared to that, anyone with knowledge and/ or experience in the physics/ dynamics of railcars should recognize that the repetitive insistence on the sloshing theories is BoguS.
Paul_D_North_Jr Back in the late 1970's or so CN did a study of the effect of flat wheels on the track structure, which was published in either Railway Track & Structures magazine or the Proceedings of the American Railway Engineering Association (AREA, predecessor to AREMA). In particular, the purpose of the study was to measure and determine the costs of the track damage caused by flat wheels, whether or not the flat spot was bad enough to require replacement or 'truing' of the wheel. The study included both wood and concrete ties, as I recall. The study concluded that the costs of the track damage greatly exceeded the costs of replacing/ truing the wheels. The administrative / institutional problem was that the track damage came out of the Engineering / MOW Department's budget, whereas the costs of fixing the wheels came out of the Mechanical Department's budget. Although a 'holistic' approach could be taken to minimize the overall aggregate or total costs by some combination of less wheel replacement costs and less track damage costs, evidently those 2 departments of most railroads couldn't agree on a method to make even that internal adjustment and reconciliation. From: http://www.tsb.gc.ca/eng/rapports-reports/rail/2014/r14w0041/r14w0041.pdf "Wheel impacts and broken rails Rail steel is known to have reduced fracture toughness and ductility at low temperatures, particularly if a rail defect, which can act as a stress riser, is present. It is also generally recognized that wheels producing high-impact loads may cause damage to equipment (axles and journals) and track infrastructure. Canadian National Railway (CN) had previously analyzed wheel-impact and broken-wheel data from 1992 to 1995. The analysis established a causal link between high wheel impact loads and broken rails. The TSB has investigated at least 5 occurrences caused by broken rails resulting from high wheel impacts (Appendix A)." See also: https://www.ihha.net/sites/default/files/document_0.pdf (pgs. 91 - 100) http://railtec.illinois.edu/CEE/Crossties/Deliverables/2013_JRC_Van%20Dyk_et_al.pdf - QUANTIFYING SHARED CORRIDOR WHEEL LOADING VARIATION USING WHEEL IMPACT LOAD DETECTORS - Paul North.
Back in the late 1970's or so CN did a study of the effect of flat wheels on the track structure, which was published in either Railway Track & Structures magazine or the Proceedings of the American Railway Engineering Association (AREA, predecessor to AREMA). In particular, the purpose of the study was to measure and determine the costs of the track damage caused by flat wheels, whether or not the flat spot was bad enough to require replacement or 'truing' of the wheel. The study included both wood and concrete ties, as I recall.
The study concluded that the costs of the track damage greatly exceeded the costs of replacing/ truing the wheels. The administrative / institutional problem was that the track damage came out of the Engineering / MOW Department's budget, whereas the costs of fixing the wheels came out of the Mechanical Department's budget. Although a 'holistic' approach could be taken to minimize the overall aggregate or total costs by some combination of less wheel replacement costs and less track damage costs, evidently those 2 departments of most railroads couldn't agree on a method to make even that internal adjustment and reconciliation.
From: http://www.tsb.gc.ca/eng/rapports-reports/rail/2014/r14w0041/r14w0041.pdf
"Wheel impacts and broken rails
Rail steel is known to have reduced fracture toughness and ductility at low temperatures, particularly if a rail defect, which can act as a stress riser, is present. It is also generally recognized that wheels producing high-impact loads may cause damage to equipment (axles and journals) and track infrastructure. Canadian National Railway (CN) had previously analyzed wheel-impact and broken-wheel data from 1992 to 1995. The analysis established a causal link between high wheel impact loads and broken rails.
The TSB has investigated at least 5 occurrences caused by broken rails resulting from high wheel impacts (Appendix A)."
See also: https://www.ihha.net/sites/default/files/document_0.pdf (pgs. 91 - 100)
http://railtec.illinois.edu/CEE/Crossties/Deliverables/2013_JRC_Van%20Dyk_et_al.pdf - QUANTIFYING SHARED CORRIDOR WHEEL LOADING VARIATION USING WHEEL IMPACT LOAD DETECTORS
In the late 70s, Amtrak wanted to keep high impact wheels on Conrail freights off their new concrete ties. Conrail installed their first WILD at Mill Creek PA to try to catch them and have them set out at Enola. After sufficient work was done to show that it really was a good idea to fix high impact wheels, it took about a decade to get the AAR rule changed to allow billing.
-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/)
CShaveRR Flat wheels and frog-pounding make different sounds, and are not likely to be confused with each other. If the o.p. says he heard flat wheels, he's probably correct.As Don says, there has to be a threshhold before they're condemnable and billable. Also, consider that some of these cars with flat spots may not have had them when the train left the point of last inspection.I have long suspected (and by "long" I mean decades) that one seems to hear a lot more flat wheels these days than in the good old days because their sound used to be drowned out by the omnipresent clickety-clack over the scores of joints within hearing range.
Flat wheels and frog-pounding make different sounds, and are not likely to be confused with each other. If the o.p. says he heard flat wheels, he's probably correct.As Don says, there has to be a threshhold before they're condemnable and billable. Also, consider that some of these cars with flat spots may not have had them when the train left the point of last inspection.I have long suspected (and by "long" I mean decades) that one seems to hear a lot more flat wheels these days than in the good old days because their sound used to be drowned out by the omnipresent clickety-clack over the scores of joints within hearing range.
I think another factor is the empty braking ratio has increased as the car construction has gotten lighter and loads have gotten heavier. Empty cars are more likely to slide when brakes are applied.
A "rule of thumb" I've heard regarding flat spots is this - if you can hear one from more than seven cars away, it's a problem. Less than that and it's OK, more or less. Obviously, any defect is an issue, it's when it becomes a problem...
There are specific guidelines for dealing with flat spots, depending on size. From NORAC: Less than 2.5" - normal speed (save other defects). Up to 4" - 10 MPH. Over 4" - Stop and stay until it's determined the car can make it to the next place it can be set out.
If my math is correct, a 2.5" flat spot is about 2% of the total tread of a 36" wheel. Noisy, but not much of a problem.
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