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.
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.
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..
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