The 9/11 Forum

Yes, your figure (very nice) is similar to #2 except no connection failure. I felt compelled to allow sequential failure to account for what would probably be unrealistic angles of rotation, but is otherwise like one possible geometry I had in mind.

It does make sense. But... I'm glad you mention the facade distortion, which is the counterpoint to "no significant external evidence of catastrophic connection failures in these regions" if the connections do survive. There is a little curl visible on the SW top. I suppose...

The femr gif is what I was pointing to.

Thanks for these series of posts, OWE, femr, Major_Tom, they are really clarifying for trying to understand how the over g moment could happen.

So with femr’s graphic—I believe I understand how this could be a potential mechanism for over g acceleration— but hopefully you will bear with me for a second.

would this scenario, basically, be:

core fails in the lower part of the building, it begins to collapse and pulls down on perimeter through unbroken connections, perimeter then _itself_ fails in a lower part of the building (independently of pull down) in a small window of time--long enough after the core to give the core enough of a head start but not so long after either…

Perhaps this is what you all are more or less saying, and am slowly catching up, but wouldn’t the perimeter have had to fail for reasons that are not a direct result of the core pulling it…otherwise either the connections would break too soon to accelerate the perimeter—even if it could to those levels if the lower support for the perimeter were intact-- or the perimeter would be pulled inward rather than (relatively) straight down?

Melville wrote:core fails in the lower part of the building, it begins to collapse and pulls down on perimeter through unbroken connections, perimeter then _itself_ fails in a lower part of the building (independently of pull down) in a small window of time--long enough after the core to give the core enough of a head start but not so long after either…

I think that's it.

Perhaps this is what you all are more or less saying, and am slowly catching up, but wouldn’t the perimeter have had to fail for reasons that are not a direct result of the core pulling it…otherwise either the connections would break too soon to accelerate the perimeter—even if it could to those levels if the lower support for the perimeter were intact-- or the perimeter would be pulled inward rather than (relatively) straight down?

You raise an interesting point, several actually. So interesting that I think this geometry might need to find its way into a mass-spring simulation.

I typed a bunch of stuff, then deleted it. Very thought provoking. More thought required.

Bump, since it seems to be a hot topic. And to remind latecomers that the discussion has been going on here for a long time.

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After some reflection on this matter, and given the ongoing tail-chasing discussions at JREF, I'm inclined to believe my reaction to suggested mechanisms has been skewed by my perception that they are somewhat pedantic. Not grossly so, but it is fairly easy to come up with gravity driven systems where some component accelerates at greater than free fall, the real issue is concretely applying any of these mechanisms to the remaining structure of WTC7 and its dynamic state.

Honestly, the most in-depth discussion of this topic of which I'm aware is my own post here in this thread, written about a year ago. The thread started at the end of November 2008, and Dr. G was the first to notice that the NIST interpolation indicated a period of over-g.

For those of you showing up late, the acceleration of WTC7 was one of the first topics examined in detail in this forum, and the discussions continued off and on for over 3 years. There is no place where more attention has been paid to the details of extracting motion data from Bldg 7.

Measurements aren't the whole story. This simple planar mass-spring model, as crude as it is, represents the most intensive effort to produce a computational result from an idealized elastic model I've seen. The scale is 1:1 with the top 14 stories; the most significant kinematical deficiency is obviously being in 2D, but this result would hold for an axis of symmetry directed orthogonally through the plane. There are other deficiencies I won't bother with here but should be evident to anyone with some experience in simulation.

It is a bounding case in that it is:

- fully elastic
- no connection breakage
- no damping
- empty space below at t > t₀ + 0.5

Due to having no elastic limit, it is effectively a hell of a lot stronger than B7 ever could be (it can rest with the entire mass supported on the endpoints, which would clearly result in immediate and total structural failure in the real building).

Being a scale model of an extreme bounding case, this model very roughly captures the maximum possible elastic response for structures in this class. The dynamics indeed reproduce very closely the observed descent characteristics claimed for B7, namely about 2.5 seconds of over g.

Hmm, what a coincidence!

And maybe it is just a coincidence. I'm hesitant to put too much stock into it but, after seeing how eagerly all manners of people at JREF have jumped onto the "it's basic physics" bandwagon, I think it's quite appropriate to cite a scale simulation as long as others think they can shoot from the hip.

What does this model have to say about the elastic response theory of over-g in WTC7? In a couple of words, fat chance. Structures which are homomorphic to this model require seemingly impossible elastic/ductile response to produce this dynamic effect. By comparison to the cheap analogies and vague seat of the pants reasoning employed daily everywhere this topic is discussed, this model is the authoritative death knell for the elastic response theory.

Post-rant disclaimers:

What I said above, and said before in other posts, seems to put me at odds with femr2. Not really. There's no doubt in my mind femr2's measurements are the best, and I'd have no qualms about using these measurements to assert over-g is likely to have been exhibited. Some time ago, I relaxed but did not totally abandon my skepticism. This was with the intent of following up with an analysis to the sensitivity of scaling errors; not errors on femr2's part, but rather the possibility of incorrect information (supplied by NIST) on which femr2's final results depend, something which femr2 has acknowledged and recently disclaimed in a post at JREF. Since I didn't follow up, I must simply accept the results as correct unless something shows otherwise.

As usual, none of this (at least directly) has anything to do with CD or not. One mistake I make all the time is that I assume readers are aware of background context - that because I've mentioned it somewhere before, even multiple times, everyone must have seen it. So there it is. My incredulity has nothing to do with any natural or unnatural processes, it is and always been contingent on two things:

1) disintegration is NOT a state which corresponds well to 'heroic' levels of elastic response
2) derived acceleration from video displacement measurement is a perilous task

I've made my case for #1 above, mostly posthumously, as I'm not in fighting mode over this issue. It is presented as a critical contribution, trying to reason about the phenomena as precisely as natural language allows, and even going on to coupled multibody physics simulations - well beyond the capabilites of natural language. I feel this is important given the level of discussion still surrounding the issue. Not counterarguments so much as mitigating considerations.

femr2 has undoubtedly done the best with the process from front to back, the conclusions are the gold standard for this subject. Anyone depending on these results is in pretty good stead. There are no guarantees, however. The caveat of #2 is omnipresent, you just happen to be in good hands with femr2, IMO.

Recent post by femr2 at JREF, in response to a post by Christopher7, nicely summarizes many of the fine points. NIST and Chandler do NOT agree. Both employ inferior methods. NIST interpolation (quite unconsciously, I believe) does indicate over-g. Etc, etc.

There are many more fine points than these. Finding them in this forum is an exercise for the truly interested reader, but it isn't that hard.

What I think is fascinating is the chronology from the debunker camp (sorry to keep using these indiscriminate terms as if there were a monolithic debunker entity), which is of a considerably wider scope than merely JREF. As I recall, and anyone is welcome to correct me, it goes something like this:

Period of time prior to release of NIST WTC7 draft report
- there was no interval in which any portion of WTC7 was in freefall, let alone exceeding g

Following release of draft but prior to final report (comment period + final publication)
- same as above but with the addition of "Chandler is full of BS"

Following release of NIST final report
- Chandler simply demonstrated NIST was correct all along, in his own bumbling truther way
- freefall is expected

Immediately following revelations that NIST interpolation showed over-g
- disbelief, attack of the messenger

Once the reality that NIST interpolation showed over-g had sunk in
- over-g is no surprise, rather it can be expected

Immediately following femr2 presentation of interpolations showing over-g
- over-g is no surprise, rather it can be expected; still, attack the messenger

Once the reality that femr2 actually had something sunk in
- over-g is no surprise, rather it can be expected; cite femr2 instead of NIST


I challenge anyone who thinks my recollection wrong to prove it so, the posting histories are all there at major forums. Find me one debunker who was arguing for freefall acceleration before the NIST final report or over-g before femr2 clued them in (they'd already missed the bus on discussions here years ago). ONE.

Note that virtually every one espousing over-g now (like it ain't no thing but a chicken wing) never said anything about it before femr2 and Major_Tom practically shoved it up their collective asses.

Why, an entirely crackpot line of thinking is revealed by that chronology! The only thing funnier is Christopher7 playing the role of debunker-stuck-in-the-past.

Now, research the subject of WTC7 acceleration on this forum. Perhaps you'll understand why I don't take kindly to advice from the peanut gallery.*





* there are notable exclusions to the peanut gallery, not everyone who self-identifies as 'debunker' is mindlessly part of the debunker camp, at least not all of the time.

Christopher7 shows he doesn't know his ass from a hole in the ground:

You are spewing a lot of techno-babble trying to snow people. I'm not buying it. This is actually very simple. The graph that Chandler used is the one he has his students use to determine speed and/or acceleration. NIST used the same method because it is an excepted scientific way to get the job done.

FEMR's graphs show something different, something that did not happen. They are worthless insipid, techno-babble. But you can buy that crap if you want.

FEMR does NOT know better than Chandler and NIST and yes, that is an appeal to authority, as is your insistence that FEMR knows what he is talking about. He doesn't. I know BS when I hear it and this is Texas prime.

http://forums.randi.org/showpost.php?p=8286082&postcount=4782

I like Mandy Patinkin, but am developing a rash to his visage, courtesy Christopher7's avatar.

What's wrong? (Even many of the debunkers know this, so follow along if you don't!)

"The graph that Chandler used is the one he has his students use to determine speed and/or acceleration."

I hope Chandler doesn't have his students do this, because it would be very sad, but I wouldn't be surprised. Chandler did a linear interpolation of velocity. If the acceleration isn't constant, then this method will be unable to resolve anything but the best fit line.

Oh, but you say Chandler got a good fit? So what? I show here and in the following post that obtaining an equally good fit of NIST's "over-g" data is quite simple with a modest twiddling of the t0 placement, yielding an apparent constant acceleration from a nonlinear interpolation, 90% of g. Illusions.

Good measurements show the acceleration to be non-constant, so shoving crappy data through a sieve which only allows constant acceleration will - surprise - yield constant acceleration.

Here is a post describing the position error due to lack of perspective correction for the CBS camera, based on typical geometry available. The position error is only 2%, but add in temporal uncertainty and take second differences, then what is the possible range of error on acceleration fits?

More BS from Christopher7.

Incorrect. Mr Chandler and NIST used every 5th or 6th frame because any more that that does not increase the accuracy, it just adds "noise".

What a load. It adds a lot more information than noise. There is, a priori, no reason to assume the information content differs from sample to sample on average, and even less reason to believe that the samples chosen by Chandler were somehow 'special'. So the act of choosing less samples provides correspondingly less information. While it is true that noise is present, always is, all data extraction is predicated on the notion of a useful signal to noise ratio which applies to the dataset as a whole.

Less noise => less information. Sorry, that's the way it goes.

Reductio ad absurdum: If more points merely add more noise, then collecting every 5th or 6th point doesn't go far enough! Why stop there? Use only 1 point out of the whole dataset. OK, three, because that's the minimum needed to determine acceleration. Beginning, middle and end. After all, adding more points only adds noise.


Is it too bitter to call so many people dumbasses? I'm sooo tired of people claiming armchair expertise when they know nothing.

Melville wrote:Perhaps this is what you all are more or less saying, and am slowly catching up, but wouldn’t the perimeter have had to fail for reasons that are not a direct result of the core pulling it…otherwise either the connections would break too soon to accelerate the perimeter—even if it could to those levels if the lower support for the perimeter were intact-- or the perimeter would be pulled inward rather than (relatively) straight down?

Thinking finally done. Yes.

When you scan an old picture at more than 300dpi then you will pick up noise but that has indeed nothing to do with the frames of a video. If you have a fixed camera and a fixed object noise will randomize your video frames but the average could provide a better resolution than a random frame of that video. The problem of determining the acceleration is still very difficult, but it is clear that one should use all frames.

OneWhiteEye wrote:Note that virtually every one espousing over-g now (like it ain't no thing but a chicken wing) never said anything about it before femr2 and Major_Tom practically shoved it up their collective asses.

Why, an entirely crackpot line of thinking is revealed by that chronology! The only thing funnier is Christopher7 playing the role of debunker-stuck-in-the-past.

Now, research the subject of WTC7 acceleration on this forum. Perhaps you'll understand why I don't take kindly to advice from the peanut gallery.*

It's all, er, progress

Popped in to find my discussions with Chandler about his data. Shall have a rummage.

Oh, and only popped there as I do an occasional search on @mentions

einsteen wrote:it is clear that one should use all frames.

Absolutely. As I tried time-and-time-again to get through to tfk, the important factor is how you handle that data afterwards. Don't think he ever got there

OneWhiteEye wrote:Recent post by femr2 at JREF, in response to a post by Christopher7, nicely summarizes many of the fine points. NIST and Chandler do NOT agree. Both employ inferior methods. NIST interpolation (quite unconsciously, I believe) does indicate over-g. Etc, etc.

The post has now been moved to "abandon all hope", and a warning issued. lol