NDGYour Diagnosis IS OCD, Sir. There can never be too much info regarding Safety esp when so much Placarded material is moving by rail, and others who are responsible for Track Maintenance might well take pointers from any of the information presented in these threads regardless of track, ties or fasteners. Wide Gauge can have many causes, some right under one's nose, IF he knows where to look beforehand.
There can never be too much info regarding Safety esp when so much Placarded material is moving by rail, and others who are responsible for Track Maintenance might well take pointers from any of the information presented in these threads regardless of track, ties or fasteners. Wide Gauge can have many causes, some right under one's nose, IF he knows where to look beforehand.
This is true, and indeed Safety should be First, but the thread topic is specifically LAG SCREW FIXATION with respect to wide gauge or other derailments. I repeat: what is the relevance of the report you posted with respect to that topic? (I am serious; you've partly answered it already above. Be as OCD as you want; even if nobody else may care about that stuff but me, I'll still read it with interest.
The old saying was 'Sun Kink'
How is that supposed to be different from the current saying, "sun kink"?
There can also be too much information presented, seemingly in an obsessive fashion? regarding locomotives scrapped half a century or more ago. ( Groan! ) I like steam, but, there is overkill. Younger folk will wonder about forum folk and may well get turned off by steam overkill? if they had any interest to begin with?
I like steam, but, there is overkill.
Younger folk will wonder about forum folk and may well get turned off by steam overkill? if they had any interest to begin with?
You are starting to get dangerously personal with these remarks, which is strange coming from someone who certainly goes on at length with stream-of-consciousness recollections of Canadian minutiae from bygone days that may be of equal, if not greater, deterrent effect on casual Forum readers. (Not that I want you to stop posting them -- I find them fascinating both in the subject matter and in the telling!)
Some people have had a life, some have not?
And some still do. I certainly have one outside the Forum, but I enjoy passing along some thoughts to perhaps-interested parties here.
There is a world of difference in changing and spiking ties in real life, than reading about it in an obscure manual.
There is also a world of difference between understanding the engineering of track fixation systems, and the refinement of automated reporting systems for effective track safety, and recounting riding obsolete locomotives over sun-kinked track.
I, on the other hand, have been trying not to make fun of non-engineers who post on technical topics disparagingly. (Having done that myself too often in the past, and repenting of it)
(I do, however, ask how your supposed experience with changing and spiking ties might relate to automated track inspection and maintenance... particularly with respect to track fixation systems that do not show physical signs of damage as they fail)
Some have no other reason to contribute that to overlord others with their knowledge, much of which may not be of interest to others.
Let's charitably hope you are not referring to me with this sentence. Most people on this (and other) forums do understand the point of the delete key, and are aware that no one (in or out of 'the Government') is twisting their arm to have to read or follow something that's posted. If you are not interested in steam technology ... don't read about it. No one is likely to care whether you do or not, although some might be concerned about the associated arrogance in dictating what is and isn't interesting to younger readers.
One is not likely to experience a superheater element failure on the road in Oregon? Nor shed a tire by too much Independent on the engine.
And this is relevant ... how? Because most readers won't be doing this firsthand?
I'll happily grant you that readers over in the Classic Trains forum are more likely to be interested in arcane steam-era details of that kind. My own experience with "shedding tires at high speed" didn't involve too much brake on a steam engine, and occurred much later than typical steam experience -- and I suspect you'd probably think my discussing it would be both OCD and 'overlording' with special knowledge -- but some people might find it interesting, or amusing. Is there a reason discussing something like that ought to be verboten because some folks are turned off by it?
When the Post Count reaches 5550, will there be a party?
I tried to figure this out, but couldn't. It might have been funnier to ask 'when the post count reaches 5550, will everyone participating receive a patch in the mail', but you probably couldn't figure that one out any more that I could figure out yours.
Fortunately we can now return to actual subjects ... some, you may be dismayed to know, probably containing more actual technical discussions of technical material with (horrors!) dry technical analyses.
Get out the popcorn...
Whatever for? Show's over.
The TSB report of the CN wreck cites the cause of broken lag screws to be a combination of shearing and bending stress. What about the tensile stress lengthwise with the screw shank? Why would that not also contribute?
Lateral pressure from the train against the outside curve rail tries to tip the rail over. This rail tipping force would tip the tie plate with the rail since the plate is fixed to the rail base. Tipping the tie plate would exert uplift of the four lag screws holding it to the tie. The leverage of this action would have the potential of applying the greatest upward tension on the screws on the field side of the rail outside of the curve. This is except for the fact that the two gage-side screws have the greatest leverage advantage of holding the rail against tipping the plate. So if the two gage-side screws succeed in doing that, it prevents the field-side screws from failing due to their relative leverage disadvantage.
So generally, I conclude that the two gage-side screws would be the first to break from fatigue caused by the dynamic tensile stress cycles of passing trains. And when one or both of those gage-side screws break, it opens the door to more easily breaking the field-side screws due to their relative leverage disadvantage. I wonder if it would be a better design to have just one screw on the field side and three screws on the gage side. Perhaps moving the three gage-side screws further from the rail by lengthening the tie plate would also help.
In the BNSF presentation, the tie plate lateral shear force is absorbed by shoulders in the concrete tie. All the lag screws do is hold the rail base down. However, the uplift force on the screws caused by the tipping force on the rail is likely greater than it would be in the in the case of the CN system. This is because the BNSF screws are nearer the centerline of the rail, and thus subject to greater leverage advantage of the tipping rail to pull the screws. I assume that these lag screws as shown on page 89, failed only because of the tensile stress lengthwise with the shank.
Euclid The TSB report of the CN wreck cites the cause of broken lag screws to be a combination of shearing and bending stress. What about the tensile stress lengthwise with the screw shank? Why would that not also contribute?
This is what I suggested back on Page 8, although not as clear.
AnthonyV Question: Is there any indication which side of the rail the lag failures occur? Gauge side or field side? I would think that the screws on the inside would be subjected to shear, bending, and tensile forces where the screws on the ouside would be subjected just shear and bending.
Question: Is there any indication which side of the rail the lag failures occur? Gauge side or field side? I would think that the screws on the inside would be subjected to shear, bending, and tensile forces where the screws on the ouside would be subjected just shear and bending.
However, the moment (or torque) tending to cause the rail to tip over must be balanced against the opposing moment due to the weight of the car.
For example, a 263,000 lb tank car on a 3 deg curve at 30 mph exerts an outward radial force on the outside rail (one truck only) of about 4,150 lb. The downward force produced by the weight of the car is 65,750 lb (one side of one truck).
Since we should be comparing moments (or torques), we need to factor in the point of application of each force and the moment arm for each force. I don't have that data handy, but my sense is that two forces are applied very closely to each other and the moment arms are comparable. If these assumptions and calculations are reasonable, then it appears that the car weight can prevent the rail from tipping over.
Does this seem reasonable or am I way off?
Just another thought:
I always assumed that the outside rail in a curve has to be held securely in order to prevent tipping over. I often wondered how the rail doesn't tip over, even with loose spikes, spikes sticking up, missing spikes, etc. it just might be that the weight of the car does prevent the rail from tipping over and the purpose of the spikes is to prevent the lateral movement of the rail.
Clearly this depends on the curvature, car mass, and train speed.
AnthonyV,
I definitely see and agree with your points about the weight of the car resisting the rail tip-over.
I conclude that in the CN wreck, all four lag screws are subject to tensile, bending, and shear forces. I am not sure how the lag screws are used with the U.P. system involved in wreck at Mosier. With the BNSF system, I conclude that the four lag screws are only subject to tensile stress lengthwise with the shank.
These are my thoughts regarding the leverage model: The rail force is to tip over to the outside. When it exerts this tipping force onto the tie plate, the tie plate becomes a lever that pivots on the fulcrum point of its edge that is on the field side of the rail. If movement is possible, this tends to exert shear, bending, and upward tensile force on all four screws.
Here is where it gets confusing. Consider the following scenarios:
1) There are two screws on the field side and none on the gage side.
2) There are two screws on the gage side and none on the field side.
In scenario #1, the tensile force is much higher on the two screws than it is in scenario #2. This is because in #2, the screws are much further from the fulcum point of the lever.
So, in the normal arrangement of two screws on each side of the rail, I conclude that as long as the two gage-side screws are tight, no upward tensile force is exerted on the two field side screws.
Therefore, the failure must begin with the two gage-side screws. Then when they break, the two field side screws will be subject to far more tensile uplift than were the two gage-side screws; and so they will fail relatively quicker than did the two gage-side screws.
Euclid These are my thoughts regarding the leverage model: The rail force is to tip over to the outside. When it exerts this tipping force onto the tie plate, the tie plate becomes a lever that pivots on the fulcrum point of its edge that is on the field side of the rail. If movement is possible, this tends to exert shear, bending, and upward tensile force on all four screws. Here is where it gets confusing.....
Here is where it gets confusing.....
Euclid:
This is the first time that I have thought about this in any detail. It just might be much simpler than one might think at first glance.
Assume the outward radial force is 4,150 lb outward (from my post above) on the rail acting 8" from the pivot point you mentioned in your post. This produces an overturning moment of about 2,800 ft-lb. Further assume that the car weight of 65,750 lb is acting downward 4" from the same pivot point. The weight produces a moment of about 22,000 ft-lb in the opposite direction, preventing the rail from tipping over.
(Note that the moment arm values are just assumptions, but they shouldn't be too far off.)
If these calculations are anywhere near reasonable, then the weight of the car generally prevents the rail from tipping over.
The Following might be of interest?http://www.cbc.ca/news/business/cp-layoffs-derailment-risk-1.3652528Safety First.
NDGSafety First.
Apparently not as First as it ought to be to Ackman, Harrison & Co. Especially since I don't think it's dawned on some railroads that there is an enormous potential problem with lag-screw fixation and detection of some common problems with it... problems that may not have a good answer other than people ON the tracks with test equipment they know how to use.
There is also this, from Transport Canada (linked from the report NDG provided, but you have to read down past the newsworker tolerance limit to get there)
https://www.documentcloud.org/documents/2906493-TRANSPORTCANADASTATEMENTSTOCBC.html
Having established the point that it's ill-advised and 'not in the interests of Safety First, Last, and Always' to cut these trackwork positions arbitrarily ... I got angrier and angrier at the newsworker spin on this story as I got further into it.
"For the last 10 years in a row, CP has been the safest Class 1 railroad in North America, measured by train-accident frequency," Martin Cej, the railway's assistant vice-president of public affairs, said in a statement emailed to CBC. "The recently announced temporary layoffs are the result of lower car volumes and softening demand in a lacklustre North American economy — factors that are affecting all railroads, not just CP."
And then, the story starts discussing all the recent derailments ... complete with de rigueur flaming oil-train picture ... on CN, which last I looked was a different railroad run by different people. Then they mention that only two of their thirteen (horrors! how unsafe!) derailments were on CP after all...
And then it starts quoting people who think the answer is more and more regulation and oversight by TC and other regulators, as if more bureaucracy was the common-sense answer to safety problems on the railroads. I was waiting for a comment on Lac Megantic, and sure enough it provided some of that, too (as if, perhaps, CP's track maintenance had contributed to that accident?)
In short: very important message, delivered in an increasingly reprehensible way. It'll be interesting to see if CP changes its tune on the 500 layoffs as the evolving story of the lag-bolt fixation problems gets better detailed...
for the "after" picture: http//:www.thedalleschronicle.com/news/2016/jun/25/railroad-replace-bolts-after-mosier-derailment/
zugmann Can I point out that Norm just screwed the whole thread? Sorry.. I couldn't resist any longer. Norm48327
Can I point out that Norm just screwed the whole thread?
Sorry.. I couldn't resist any longer.
Norm48327
for the "after" picture: http://www.thedalleschronicle.com/news/2016/jun/25/railroad-replace-bolts-after-mosier-derailment/
Judging by the corrosion, those bolts have been broken for some time.
Norm
Now we know what "one or more" broken lag bolts looks like.
Here is the link again from the above post:
http://www.thedalleschronicle.com/news/2016/jun/25/railroad-replace-bolts-after-mosier-derailment/
As Norm says, some of the bolts, do indeed appear to have been broken for a long time. Overall, they appear to be woefully inadequate for the task unless their service life were known and were conscientiously limited to its length. That service life would also include the life of the ties as the bolts damage the threaded bores in the wood. There is not much good in inspecting the track every couple days when you have this kind of mass failure underway.
Interestingly, the article mentions ECP brakes and Sarah Feinberg contenting that they could have reduced the number of cars involved, and also limited the breaching.
I would say, that from what we know about the derail cars dragging in line for 3/8 mile prior to the pileup, derailment sensors on each car would have prevented the pileup, the punctures, and the fire altogether.
The article says this:
There was little prior focus on failed lag bolts, and there appears to be only one other instance in which they caused a derailment, in Canada’s Alberta Province in 2012, Gard said, adding a further look is needed.
This is the CN Fabyan Bridge derailment that we have been discussing here. In my opinion, there should have been a lot of focus on the potential failure of lag bolts after that wreck. It was fully investigated and it should have been a wakeup call to the railroad industry.
What is most amazingly strange is the U.P. response that on 530 miles of track curves using lag bolts, they will replace those bolts with spikes.
UP is replacing screws with spikes, not BNSF.
ECP brakes would have made no difference. An emergency application would have been exactly the same.
Without having dimensions of the screw I can't say for sure but if the shank Diameter of the screw is the same as the cross section of a cut spike then the minor diameter has a less than half of the area of the cut spike. I would have thought that going to a round fastener would mean maintaining that area, which is where the shear strength of the fastener comes from.
tdmidget,
I meant to refer to the article saying U.P. is replacing their screws with spikes, and have edited my post accordingly. I am somewhat mystified by their reasoning for the change. Screws were adopted because their superior holding power is an advantage on curves compared to using spikes.
I am guessing that the reason for changing back to spikes is that their progressive failure is visually predicted by seeing them somewhat backed out of their holes. Whereas spikes with the better holding power do not back out, but rather, they break with no visual indication.
I would think the better approach would be a combination of improving the strength of the screws, determining their lifespan based on use, and replacing them within that time span. They could also couple that with periodic inspection to see if their lifespan is on course with its prediction.
Euclid I would think the better approach would be a combination of improving the strength of the screws, determining their lifespan based on use, and replacing them within that time span. They could also couple that with periodic inspection to see if their lifespan is on course with its prediction.
If you can't reliabilly inspect something to determine failure, it makes no difference what it's life span before failure is - especially if the life span before failure is different than the rest of the inspectable track structure.
Never too old to have a happy childhood!
BaltACD Euclid I would think the better approach would be a combination of improving the strength of the screws, determining their lifespan based on use, and replacing them within that time span. They could also couple that with periodic inspection to see if their lifespan is on course with its prediction. If you can't reliabilly inspect something to determine failure, it makes no difference what it's life span before failure is - especially if the life span before failure is different than the rest of the inspectable track structure.
I see no reason why these lag screw installations could not be reliably inspected. That alone would prevent failure. After learning what happened in the CN Fabyan Bridge derailment, the TSB developed specfic instructions for how to inspect the lag screw systems. It is additional work, but it is effective and necessary.
Then with what is learned in the inspections, they could determine the life of such lag screw installations. Knowing that lifespan would then be used to give further insurance in addition to the direct inspection for lag screw condition. This all should have been obvious after the CN wreck in 2012.
Euclid BaltACD Euclid I would think the better approach would be a combination of improving the strength of the screws, determining their lifespan based on use, and replacing them within that time span. They could also couple that with periodic inspection to see if their lifespan is on course with its prediction. If you can't reliabilly inspect something to determine failure, it makes no difference what it's life span before failure is - especially if the life span before failure is different than the rest of the inspectable track structure. I see no reason why these lag screw installations could not be reliably inspected. That alone would prevent failure. After learning what happened in the CN Fabyan Bridge derailment, the TSB developed specfic instructions for how to inspect the lag screw systems. It is additional work, but it is effective and necessary. Then with what is learned in the inspections, they could determine the life of such lag screw installations. Knowing that lifespan would then be used to give further insurance in addition to the direct inspection for lag screw condition. This all should have been obvious after the CN wreck in 2012.
Remember you are dealing with railroads - additional work is verbotten! Maintenance items are adopted as standard to decrease work, not increase it.
Well if reducing inspections to minimize work leads to train wrecks, it seems penny wise and pound foolish.
EuclidI see no reason why these lag screw installations could not be reliably inspected.
Care to tell us what "experience" you have in inspecting them? If you have a plan that works please make it public so the railroads can learn from it.
Euclid Well if reducing inspections to minimize work leads to train wrecks, it seems penny wise and pound foolish.
Who is reducing inspections? FRA sets the required inspection standards for the various classes of track and the carriers either meet or exceed these inspection standards already. If the inspection item (lag screws) now creates more work in their inspection than a competing technology - the lag screws will shortly be replace by the competing technology.
Norm48327 Euclid I see no reason why these lag screw installations could not be reliably inspected. Care to tell us what "experience" you have in inspecting them? If you have a plan that works please make it public so the railroads can learn from it.
Euclid I see no reason why these lag screw installations could not be reliably inspected.
Norm,
The plan has been public since the TSB of Canada published in shortly after investigating the CN Fabyan Bridge derailment in 2012. Here it is:
When conducting inspections of curves, turnouts, and bridge decks with screw spikes, please be governed by the following:
And what is your "experience" with this topic?
C&NW, CA&E, MILW, CGW and IC fan
BaltACD Euclid said: Well if reducing inspections to minimize work leads to train wrecks, it seems penny wise and pound foolish.
Does anyone know the dimensions of these lagscrews?
tdmidget Does anyone know the dimensions of these lagscrews?
Here is some info on what they call BNSF-style lag screws.
www.lewisbolt.com/products/Square_Head_Timber_Screw_BNSF_Style/index.html
Nice to see the Made In America since 1927 line.
Euclid
For the record Steve Ditmeyer was never a federal "regulator". He did work for FRA but was head of their research group. His major focus was PTC related work. The Aries system at BN was his baby, he was quite bitter when the BN did not implement it. His tenure at FRA was short.
What was the weight of an overloaded car ?
Many of the home improvements shows often state that some woods do better with nails than screws. Screw holes drilled sometimes are better. So are screw spikes drilled or just run into the crosstie ? Would expect that type of wood for cross tie might have different results ?
A 5/8 cut spike has a cross section of .3906 square inches. The BNSF screw, which is probably typical, has a cross section of.5050 in the minor diameter, which is where every example shown has broken. A 3/4 cut spike would have a cross section of .5625 square inch and likely be cheaper. It would not cost much to put smll grooves on it like a ring shank nail, which are a mofo to pull out.
The stress riser of the threads cannot be disregarded, as cannot the obvious corrosion.
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