Oil Train

[Euclid]

dehusman

 

Euclid

So now the argument focuses squarely on the technical question of whether ECP brakes contribute to safety or not.

 

 

Not at all, it really has nothing to do with whether ECP is safe or not.  The AAR's lawsuit is about how do they implement the regulation.  I was talking about the regulation with someone involved with the design of new tank cars and he felt this was one of the most poorly written regulation he had seen.  The technical and operational aspects were full of loopholes, contradictions, responsibility without authority and ambiguous language.

 

Not at all?  What are you talking about?  In my comment from which you quoted, what I quoted from the AAR statement most certainly does have everything to do with ECP brakes and whether they improve safety.  The AAR made that very point in my quote from their statement.  Read their words.  They have also stated that position many other times in the last few months.

 

"In its prepared statement, AAR said its main concerns with the rule include… the mandating of ECP brakes, which is unproven technology that will not prevent derailments and will not provide meaningful overall safety benefits that our industry and the general public want."

[dehusman]

Euclid

So now the argument focuses squarely on the technical question of whether ECP brakes contribute to safety or not.

Not at all, it really has nothing to do with whether ECP is safe or not.  The AAR's lawsuit is about how do they implement the regulation.  I was talking about the regulation with someone involved with the design of new tank cars and he felt this was one of the most poorly written regulation he had seen.  The technical and operational aspects were full of loopholes, contradictions, responsibility without authority and ambiguous language.

[Euclid]

From the link above announcing the AAR appeal:

In its prepared statement, AAR said its main concerns with the rule include… the mandating of ECP brakes, which is unproven technology that will not prevent derailments and will not provide meaningful overall safety benefits that our industry and the general public want."

 

I do not know what they mean by “meaningful overall safety benefits.”  It sounds like splitting hairs over the quantity of safety benefit.  I think the general public wants any amount of safety benefit.  Perfection is not possible, but every little bit helps.

Of course, the ECP industry will disagree with the AAR contention that ECP brakes will not prevent derailments.  They will say that the near elimination of slack run-in will prevent derailments, thus leaving the AAR to argue that the slack control advantage is not “meaningful.”  The ECP industry will laugh at the AAR’s contention that ECP is “unproven technology.”   

Here is what Sarah Feinberg, Acting Administrator of the FRA, said about ECP brakes: 

 

Sarah Feinberg, the acting administrator of the Federal Railroad Administration, said: “The mission of the F.R.A. is safety and not focusing on what is convenient or inexpensive or provides the most cost savings for the rail industry. When I focus on safety, I land on E.C.P. It’s a very black-and-white issue for me.”

[wanswheel]

Excerpt from Wall Street Journal, June 12

Railroads don’t own the vast majority of tank cars so have little control over whether the costly new brakes are installed. Moreover, the brake requirement isn’t a mandate for tank car owners, only railroads. But if tank cars aren’t equipped with the new brakes, oil trains will either have to be reduced to a maximum of 69 tank cars or to a maximum speed of 30 miles an hour, both of which would effectively reduce railroads’ capacity.

Railroads also take issue with the rule’s allowance of shipments in any kind of tank car, provided it is in less than a block of 20 tank cars or fewer than 35 tank cars total.

Additionally, they want increased thermal protection for tank cars to allow for emergency responders to have more time before they explode during a fire…

Railroads aren’t the first to challenge the new rules. Separate challenges filed in federal appeals court include one by environmental groups arguing the timeline to phase out dangerous older tank cars is too long and that the new standards are too weak, among other demands. Two Illinois municipalities filed a similar appeal, while the American Petroleum Institute, which represents the oil industry, is seeking more time to make retrofits to oil tank cars because of manufacturing-capacity restraints.

[Euclid]

Very interesting news.  I was expecting the AAR to take issue with the ECP mandate.  But I am surprised that they also take the position that the new tank car rules do not go far enough to increase safety.  It seems like an odd stance.  The AAR was presumably worried that the new regulations would go too far, and that worry was validated by the ECP mandate.  However, the AAR does not see the ECP mandate as going too far in terms of safety because they don’t believe ECP improves safety.

So now the argument focuses squarely on the technical question of whether ECP brakes contribute to safety or not.  On that point, the AAR and the USDOT are diametrically opposed.  Apparently the court will answer that question once and for all. 

[Buslist]

As I predicted here it comes! Will ECP survive the court challange?

http://www.progressiverailroading.com/federal_legislation_regulation/news/AAR-files-appeal-of-USDOTs-tankcar-rule--44756?email=[e-mail]&utm_medium=email&utm_source=prdailynews&utm_campaign=prdailynews06/15/2015

[tree68]

Euclid

With all the testing, I am amazed that this was not learned before launching the 1232 cars.

Who says it wasn't?

[Euclid]

Paul of Covington

    I'm still trying to figure out why it is important to know that a tank car might fail by being compressed till the pressure of the liquid blows it out.   Personally, it seems much more likely that the metal fails by being punctured or torn by an edge or corner of another car or a solid structure.   If the pressure caused the metal to fail, it seems to me that the metal would be pushed out at the edges of the break, and investigators would have recognized this as the cause of failure.   If it can be shown that the pressure caused the failure, how would you design the cars differently?

 

Paul,

It is not particularly important to know that a tank may breach by squeeze burst.  It is just another breach mode.  But the squeeze burst mode is connected to a larger point, which is quite important.  That point is that although the squeeze burst is just another breach mode, it is the one that requires the most force.  That leads to the main overall point which is that the necessary high force to cause squeeze burst IS available.  Its availability and potential rises with the total number of cars behind the derailment.  And while that force may be high enough to cause the squeeze burst, its potential is far greater than what is needed to cause punctures or tears in tank walls.  It raises the challenge to protect against all of the breach modes.

The industry speaks often about punctures as a breach mode.  They test to determine how much force it takes to puncture a tank head with a coupler.   They install tank head shields to protect the head from puncture.  I don’t believe that the industry accounts for the maximum potential force that I refer to when designing this protection.  If they did, why are tank cars breaching in every derailment? 

The industry has endless technical expertise at their disposal.  How could they possibly miss anything?  But they did totally miss the boat with the 1232 tank car design.  Only after building and putting into operation hundreds of these cars, have they learned that they are way short of solving the breach problem which was the announced intent.  Did they not test this design?  Did they test to incomplete assumptions?          

You ask; if it can be shown that the squeeze pressure caused the failure, how would I design the cars differently?  Since the heart of the problem is the extreme force potential of the trailing cars, my answer is that I would not design them differently because there is no viable design possible without increasing the empty weight of the car, and thus reducing the payload to an uneconomical level.  The actual breach mode makes no difference.  The maximum force potential will be unstoppable no matter whether it drives punctures, tears, crushing, cracking, or squeeze bursting.       

I conclude that there is no way to protect tank cars from this highest potential force.  That is why the car builders have recently said that tank cars cannot be built strong enough to prevent breaching in high speed, high energy derailments.  With all the testing, I am amazed that this was not learned before launching the 1232 cars.

[Norm48327]

Murray

Nice thing about the Internet. It captures everything you say...no matter how incorrect it is.

And shows how Bucky's logic keeps going in circles as he tries to explain what he really meant and justify his opinion.

[Anonymous]

dehusman

 

Euclid

Several times it has been implied that I say it does happen very often. Obviously that is not the case and I never said or implied it. It is the typical tactic of exaggerating something to an absurd level in order to discredit it.

 

 

Lets see:

 

5/28 10:14 pm

 

Euclid

I also said that I believe that in many cases, the tanks are subjected to extreme compression that sometimes raises the internal pressure high enough to burst the vessel.  I know that you have insisted many times that this is impossible and has never happened.  I have explained why I think it can and does happen.

 

 

  

5/29 1:59 pm

 

Euclid

You raise good points.  All I am saying is that I believe this happens often.  If it can be proven otherwise, so be it.  If I could procure examples, I would, but how can I do that?  But in the meantime, I don’t see why it would be considered to be an extraordinary claim. 

 

 

 

 

 

 

 

 

 

 

Nice thing about the Internet.  It captures everything you say...no matter how incorrect it is.

[MidlandMike]

Euclid

Dave,

You say that bursting requires raise the internal pressure without exceeding the tensile strength of the shell.

I don’t understand your point.  Raising the internal pressure to the point of exceeding the tensile strength of the shell is precisely what bursting is.

 

You evidently don't know the difference between tensile strength and burst pressure.

[MidlandMike]

Euclid

 

MidlandMike

 

Euclid

...

But again, the point is not so much that these collision impacts can occur.  Instead, it is that the real world force potential is so vastly greater than just one moving car striking a stationary car; the simplistic model of collision which appears to be assumed in the crash testing of tank cars.    

 

 

 

 

You still have not demonstrated a mechanism by which the force of a following car is multiplied by the rest of the following cars.  Couplers are designed to fail before structural damage is done to a car.  Tank cars themselves are their own structural force, since the absence of center sills.  A following tank car will itself be crushed between the pile and the next following tank car, and so on.  The entire force of the train will never be concentrated at one spot, and the kenetic force will be disapated thru the entire pile-up process.

 

 

 

Midland Mike,

This in respose the your above quoted post and your post a few posts prior:

I agree that a small amount of the kinetic energy in string of cars coming into the derailment from behind is going to be absorbed in the draft gear.  Also, a fair amount will be dissipated by braking.  But every car will still retain a large amount of kinetic energy that will either require enough braking time to dissipate or; might get dissipated in a mass of collisions and friction during a derailment pileup, if there is not enough time for the brakes to stop the cars.   

So, I would say that the total energy of this line of incoming cars is indeed concentrated to one point.  Generally speaking, that force is directed through the drawbars and couplers to the head end.  Specifically, the force is concentrated to the point of impact if it runs into an obstacle.  

Say you have 20 cars on the rails, rolling forward, and feeding cars into the derailment zone.  The collective energy of those 20 cars is pushing one car at a time into the derailment pileup.  It is true than just one car at time is derailing, but that does not mean that the collision force is as if only a single car hit a stationary car.   On the contrary, the force that is directed into the collision point is the force of 20 cars acting as one, just like a giant battering ram.

Therefore, regarding the force that damages and ruptures tank cars in a pileup; the greater the number of cars behind the derailment, the higher that force rises.

 

I didn't say the draft gear would absorb some energy, I said theat the draft gear/couplers will fail.  You have not disputed that they are made to fail in extreme forces, you just keep repeating that the total force is directed thru the couplers.

A train of tank cars is not like an line of impenetrable billiard balls, but instead are elastic, which is indesputable as evidenced by the crumpled pile of tank cars in the wake of a wreck.  You have no basis in physics for saying that the total force of the following cars is transferred to the pile "like a giant battering ram".

[dehusman]

Euclid

Several times it has been implied that I say it does happen very often. Obviously that is not the case and I never said or implied it. It is the typical tactic of exaggerating something to an absurd level in order to discredit it.

Lets see:

 

5/28 10:14 pm

Euclid

I also said that I believe that in many cases, the tanks are subjected to extreme compression that sometimes raises the internal pressure high enough to burst the vessel.  I know that you have insisted many times that this is impossible and has never happened.  I have explained why I think it can and does happen.

  

5/29 1:59 pm

Euclid

You raise good points.  All I am saying is that I believe this happens often.  If it can be proven otherwise, so be it.  If I could procure examples, I would, but how can I do that?  But in the meantime, I don’t see why it would be considered to be an extraordinary claim. 

 

 

[Wizlish]

Euclid

Now you say this: “except that a few posts ago you were trying to claim it was the predominant way in which tank cars were failing in these accidents.” That is not true. I never said anything of the sort. Please show me exactly where I said that. You say it was a few posts ago. Which one?

You are correct -- I looked back at the recent history of this thread and you did not say that (directly or otherwise).  What you were doing was returning to the idea that it was frequently observed as a failure mode in these accidents.

In science, if you are going to promote a hypothesis, it is YOUR responsibility to establish evidence for it.  It is not permissible to claim that we have to disprove that it ever, ever happens when yes, yes, it sertaily could happen.  You have repeatedly stated that you think it occurs in many situations, not that it 'could' happen under some circumstances.  That does not give it scientific standing, any more than coining terms like "maximal force potential" somehow makes them real phenomena that we then bear the onus of refuting.

[Paul of Covington]

    I'm still trying to figure out why it is important to know that a tank car might fail by being compressed till the pressure of the liquid blows it out.   Personally, it seems much more likely that the metal fails by being punctured or torn by an edge or corner of another car or a solid structure.   If the pressure caused the metal to fail, it seems to me that the metal would be pushed out at the edges of the break, and investigators would have recognized this as the cause of failure.   If it can be shown that the pressure caused the failure, how would you design the cars differently?

[Euclid]

Wizlish

 

Euclid

Just to clarify, if we go back to the beginning of this topic, I said that I believe that squeeze bursting can happen and does happen sometimes. So I don’t see the basis for all the rejection focused on the premise that it does happen all of the time in every derailment. Nobody ever said it does.

 

 

Just to clarify, Dave (and I) don't really believe it happens, but perhaps it does.  However, we are not just going to take your word that it does.  We have been asking, and will continue to be asking, for some proof, either photographic or reported, that 'squeeze bursting' exists as an actual cause of an actual failure ... even one ... and not just a hypothetical occurrence.

The 'rejection' is not based on any 'premise that it does happen all of the time in every derailment'.  I am not sure where you got the idea anyone was claiming that - except that a few posts ago you were trying to claim it was the predominant way in which tank cars were failing in these accidents.  That's neither here nor there.  We want to see proof that it happens in ANY derailment. 

Proof, that is.  Not more 'yes, but' assertions that it maybe, kinda, sorta, could be happening. 

 

Wizlish,

I cannot prove that it happens.  All I claimed is that I believe it happens, and I explained why.  Others have not proved it does not happen, but they say they don’t believe it happens, and they have explained why.  You and others are free to believe or disbelieve whatever you want.  At this point, from both sides, all we have is the logic our reasoning.      

Several times it has been implied that I say it does happen very often.  Obviously that is not the case and I never said or implied it. It is the typical tactic of exaggerating something to an absurd level in order to discredit it. 

Now you say this: “except that a few posts ago you were trying to claim it was the predominant way in which tank cars were failing in these accidents.”

That is not true.  I never said anything of the sort.  Please show me exactly where I said that.  You say it was a few posts ago.  Which one?

[Wizlish]

Euclid

Just to clarify, if we go back to the beginning of this topic, I said that I believe that squeeze bursting can happen and does happen sometimes. So I don’t see the basis for all the rejection focused on the premise that it does happen all of the time in every derailment. Nobody ever said it does.

Just to clarify, Dave (and I) don't really believe it happens, but perhaps it does.  However, we are not just going to take your word that it does.  We have been asking, and will continue to be asking, for some proof, either photographic or reported, that 'squeeze bursting' exists as an actual cause of an actual failure ... even one ... and not just a hypothetical occurrence.

The 'rejection' is not based on any 'premise that it does happen all of the time in every derailment'.  I am not sure where you got the idea anyone was claiming that - except that a few posts ago you were trying to claim it was the predominant way in which tank cars were failing in these accidents.  That's neither here nor there.  We want to see proof that it happens in ANY derailment. 

Proof, that is.  Not more 'yes, but' assertions that it maybe, kinda, sorta, could be happening. 

[Euclid]

Well, yes I agree that in order for the tank to burst from squeeze pressure collapse, there cannot be any openings in the tank wall.  If there are openings, there will be no internal pressure increase due to collapsing, and therefore no bursting from an internal pressure increase.

Perhaps Dave meant to say, “In order to "squeeze" a tank car hard enough to cause it to "burst" from internal pressure the car has to have enough compression pressure placed on it that it compresses the inside without to the point of exceeding the tensile strength of the shell.”  

Just to clarify, if we go back to the beginning of this topic, I said that I believe that squeeze bursting can happen and does happen sometimes.  So I don’t see the basis for all the rejection focused on the premise that it does happen all of the time in every derailment.  Nobody ever said it does. 

If a tank car is punctured or torn open, that precludes any possibility of squeeze bursting.  If a car is subjected enough force to collapse and burst it, but is not adequately restrained to resist that force, then no squeeze burst will be possible.  Or if a car is adequately restrained, but not subjected to a sufficient squeeze pressure, no squeeze burst will be possible.  I have offered the theory of squeeze bursting as just one more mode of breaching.  And as I originally said, I believe squeeze bursting is often facilitated by the tank collapse folding and cracking the steel.

However, aside from all of this, my larger point petains to the variations of train force that damages tank cars in a derailment; depending on how long the train is and where the derailment is located in the train; and how great these forces can be.  Unless you design head shields and tank walls to withstand these highest possible levels of compression, you are only working around the edges of the problem.         

[Wizlish]

Euclid

Dave,

You say that bursting requires raise the internal pressure without exceeding the tensile strength of the shell.

I don’t understand your point.  Raising the internal pressure to the point of exceeding the tensile strength of the shell is precisely what bursting is.

 

What he means is that, in order to have a tank car fail by your mechanism, you have to maintain the hydrostatic pressure inside an 'intact' shell (in other words, capable of holding the full hydrostatic pressure being developed) up to the point that some part of that shell fails entirely due to the force exerted by the hydrostatic pressure.

 

At least one of his points being that, in an accident, something else is likely to bend, puncture or compromise the shell (and incidentally relieve at least some of the hydrostatic-pressure force) before that state is reached.

 

It's the mechanism up to the moment of bursting he's discussing, not the actual "bursting" itself.

[Euclid]

Dave,

You say that bursting requires raise the internal pressure without exceeding the tensile strength of the shell.

I don’t understand your point.  Raising the internal pressure to the point of exceeding the tensile strength of the shell is precisely what bursting is.

[dehusman]

In order to "squeeze" a tank car hard enough to cause it to "burst" from internal pressure the car has to have enough compression pressure placed on it that it compresses the inside without exceeding the tensile strength of the shell. 

That's why I say "bursting" is unlikely.  I think that in the collision the pressure is so rapid and so concentrated that the shell is punctured or torn before it has a chance to compress the internal pressure to the failure point and rupture from the inside.

While the TTC cab surviveability videos posted by Euclid are a poor example none of the cars involved were tank cars and all the strikes were end to end or cornering blows, it is clearly seen that in all cases the sheet metal of the car sides rends and tears almost immediately on impact. 

[Euclid]

I did mention above that the brakes will dissipate some of the kinetic energy.  They would dissipate all of it if there were enough time to stop the train.  A derailment does not often give the brakes time to stop the train before cars collide.  Obviously there is a lot energy remaining when then happens.  Otherwise, what causes the pileup?  I cannot imagine how the battering ram analogy can be doubted.  It is the essence of trains.  If two trains hit head on, are we to conclude that the energy directed to the point of collision was just the force of the two knuckles hitting each other because they were the first to contact?

[tree68]

Euclid

Therefore, regarding the force that damages and ruptures tank cars in a pileup; the greater the number of cars behind the derailment, the higher that force rises.

And, the more cars "behind" the derailment, the greater the combined retarding force of their brakes, which are now in emergency.  The oncoming cars (which are not getting a head start - they are right behind the derailing cars) are not free rolling, unless you have a situation where the engineer has p!ssed away the brakes on a downgrade.  And that could happen with ECP, too...

So far we've heard lots of theory on how this battering ram phenomenon is supposed to happen.  It's time for some incident reports documenting same.  Just because it "could" happen doesn't mean it ever has, or ever will.

[Buslist]

BaltACD

 

 

Euclid

MidlandMike

Euclid

...

But again, the point is not so much that these collision impacts can occur.  Instead, it is that the real world force potential is so vastly greater than just one moving car striking a stationary car; the simplistic model of collision which appears to be assumed in the crash testing of tank cars.    

 

 

 

 

You still have not demonstrated a mechanism by which the force of a following car is multiplied by the rest of the following cars.  Couplers are designed to fail before structural damage is done to a car.  Tank cars themselves are their own structural force, since the absence of center sills.  A following tank car will itself be crushed between the pile and the next following tank car, and so on.  The entire force of the train will never be concentrated at one spot, and the kenetic force will be disapated thru the entire pile-up process.

 

 

 

Midland Mike,

This in respose the your above quoted post and your post a few posts prior:

I agree that a small amount of the kinetic energy in string of cars coming into the derailment from behind is going to be absorbed in the draft gear.  Also, a fair amount will be dissipated by braking.  But every car will still retain a large amount of kinetic energy that will either require enough braking time to dissipate or; might get dissipated in a mass of collisions and friction during a derailment pileup, if there is not enough time for the brakes to stop the cars.   

So, I would say that the total energy of this line of incoming cars is indeed concentrated to one point.  Generally speaking, that force is directed through the drawbars and couplers to the head end.  Specifically, the force is concentrated to the point of impact if it runs into an obstacle.  

Say you have 20 cars on the rails, rolling forward, and feeding cars into the derailment zone.  The collective energy of those 20 cars is pushing one car at a time into the derailment pileup.  It is true than just one car at time is derailing, but that does not mean that the collision force is as if only a single car hit a stationary car.   On the contrary, the force that is directed into the collision point is the force of 20 cars acting as one, just like a giant battering ram.

Therefore, regarding the force that damages and ruptures tank cars in a pileup; the greater the number of cars behind the derailment, the higher that force rises.

 

 

The only way you are going to understand what actually happens in a derailment is ride one out in the middle of the derailing train.  What you learn there will have applicability to that unique set of circumstance.  Derailments do not conform to your simplistic rules of physics and train dynamics.

 

 

That is why actual physical derailment/impact (the term FRA prefers) tests are carried out at TTC.

[Euclid]

There is not a complete set of rules for them, but they do conform to what said above. 

[BaltACD]

Euclid

MidlandMike

Euclid

...

But again, the point is not so much that these collision impacts can occur.  Instead, it is that the real world force potential is so vastly greater than just one moving car striking a stationary car; the simplistic model of collision which appears to be assumed in the crash testing of tank cars.    

 

 

 

 

You still have not demonstrated a mechanism by which the force of a following car is multiplied by the rest of the following cars.  Couplers are designed to fail before structural damage is done to a car.  Tank cars themselves are their own structural force, since the absence of center sills.  A following tank car will itself be crushed between the pile and the next following tank car, and so on.  The entire force of the train will never be concentrated at one spot, and the kenetic force will be disapated thru the entire pile-up process.

 

 

 

Midland Mike,

This in respose the your above quoted post and your post a few posts prior:

I agree that a small amount of the kinetic energy in string of cars coming into the derailment from behind is going to be absorbed in the draft gear.  Also, a fair amount will be dissipated by braking.  But every car will still retain a large amount of kinetic energy that will either require enough braking time to dissipate or; might get dissipated in a mass of collisions and friction during a derailment pileup, if there is not enough time for the brakes to stop the cars.   

So, I would say that the total energy of this line of incoming cars is indeed concentrated to one point.  Generally speaking, that force is directed through the drawbars and couplers to the head end.  Specifically, the force is concentrated to the point of impact if it runs into an obstacle.  

Say you have 20 cars on the rails, rolling forward, and feeding cars into the derailment zone.  The collective energy of those 20 cars is pushing one car at a time into the derailment pileup.  It is true than just one car at time is derailing, but that does not mean that the collision force is as if only a single car hit a stationary car.   On the contrary, the force that is directed into the collision point is the force of 20 cars acting as one, just like a giant battering ram.

Therefore, regarding the force that damages and ruptures tank cars in a pileup; the greater the number of cars behind the derailment, the higher that force rises.

The only way you are going to understand what actually happens in a derailment is ride one out in the middle of the derailing train.  What you learn there will have applicability to that unique set of circumstance.  Derailments do not conform to your simplistic rules of physics and train dynamics.

[Euclid]

MidlandMike

 

Euclid

...

But again, the point is not so much that these collision impacts can occur.  Instead, it is that the real world force potential is so vastly greater than just one moving car striking a stationary car; the simplistic model of collision which appears to be assumed in the crash testing of tank cars.    

 

 

 

 

You still have not demonstrated a mechanism by which the force of a following car is multiplied by the rest of the following cars.  Couplers are designed to fail before structural damage is done to a car.  Tank cars themselves are their own structural force, since the absence of center sills.  A following tank car will itself be crushed between the pile and the next following tank car, and so on.  The entire force of the train will never be concentrated at one spot, and the kenetic force will be disapated thru the entire pile-up process.

 

Midland Mike,

This in respose the your above quoted post and your post a few posts prior:

I agree that a small amount of the kinetic energy in string of cars coming into the derailment from behind is going to be absorbed in the draft gear.  Also, a fair amount will be dissipated by braking.  But every car will still retain a large amount of kinetic energy that will either require enough braking time to dissipate or; might get dissipated in a mass of collisions and friction during a derailment pileup, if there is not enough time for the brakes to stop the cars.   

So, I would say that the total energy of this line of incoming cars is indeed concentrated to one point.  Generally speaking, that force is directed through the drawbars and couplers to the head end.  Specifically, the force is concentrated to the point of impact if it runs into an obstacle.  

Say you have 20 cars on the rails, rolling forward, and feeding cars into the derailment zone.  The collective energy of those 20 cars is pushing one car at a time into the derailment pileup.  It is true than just one car at time is derailing, but that does not mean that the collision force is as if only a single car hit a stationary car.   On the contrary, the force that is directed into the collision point is the force of 20 cars acting as one, just like a giant battering ram.

Therefore, regarding the force that damages and ruptures tank cars in a pileup; the greater the number of cars behind the derailment, the higher that force rises.

[MidlandMike]

Euclid

...

But again, the point is not so much that these collision impacts can occur.  Instead, it is that the real world force potential is so vastly greater than just one moving car striking a stationary car; the simplistic model of collision which appears to be assumed in the crash testing of tank cars.    

 

You still have not demonstrated a mechanism by which the force of a following car is multiplied by the rest of the following cars.  Couplers are designed to fail before structural damage is done to a car.  Tank cars themselves are their own structural force, since the absence of center sills.  A following tank car will itself be crushed between the pile and the next following tank car, and so on.  The entire force of the train will never be concentrated at one spot, and the kenetic force will be disapated thru the entire pile-up process.

[Euclid]

BaltACD

The accordion process stops when the stresses on the coupling are not sufficient to break the coupling between cars in two.  The entire derailment procees is an exercise in depleting the kinetic energy in the moving train to zero.  It cannot be depleted to zero, instantly.

 

I am not sure if you are intending to contradict what I said about the accordion process stopping during the derailment.  I agree that the depletion of kinetic energy will continue for as long as the train is in motion, as you say.  My point was that the accordion process can start or stop at any point during the derailment process while the train is in motion.  I did not mean to suggest that the depletion of kinetic energy can stop during that period.

My point was that if the accordion process suddenly stops during the derailment, the continuing depletion of the kinetic energy may cause incoming cars to increase their damage to the derailed stationary cars.    

[CSSHEGEWISCH]

At last, somebody who understands the basic laws of physics, especially:  Energy neither be created nor destroyed.