The 9/11 Forum

David Chandler has done an analysis comparing the speed of the collapse wave with the speed of ejected material.

http://www.youtube.com/watch?v=eXSHm3CdHf4

I have identified a number of problems with his method.

1. The analysis is based on choosing a point within the ejecta that is easily identifiable and tracking that point relative to the collapse wave. However, the chosen point seems to float in the air compared to many other easily identifiable heavy debris which move much faster.

2. The collapse wave has a head start and is already moving at a significant speed.

Here are some images from Chandlers presentation where I have marked other easily identified heavy debris which are moving significantly faster than the collapse front even though the collapse front most likely had a significant head start. (Note: The green and red markings are Chandler's.)





Note that the item marked with magenta starts out very near the collapse front. In the second image, it is leading the collapse front by approximately 15m.

Note also that the item marked with tan (appears to be a large section of the perimeter columns) starts out roughly 10m above the collapse front and ends up roughly 10m below the collapse front.

It seems that David Chandler may have chosen a piece of aluminum cladding, for which air resistance is a major factor in slowing the free fall. I encourage him to redo his analysis with the ejecta I have used as they are clearly heavy debris and provide a completely different picture of what is happening.

This happens a lot. A confusion between aluminum cladding and heavy debris.

Note the fastest 2 objects in the BBC video clip are 2 pieces of perimeter columns from the very corners:

On the left we have a small section of corner perimeter columns fall so fast that it is not visible in the stills posted above. On the left we see a large (6 story) chunk of the perimeter leading the fall. It, too, is from the very corner.

I find it strange how these two corner perimeter chunks fall away from the building with such ease and clearly lead the collapse on both the left and right sides, but that is a different subject. Using frame by frame, forward and backward video analysis they both fall from floors 92 to 97, the collapse initiation region. In other words, the NW and NE corners from the collapse initiation region practically "fall off" the building with little to no resistance.


The big problem with the Chandler analysis is that you have a falling heavy piece (the one on the right mantioned above) that is practically BY DEFINITION a measure of what freefall actually means. You can clearly see what freefall is compared with the rate of collapse propagation by comparing the lead falling object on the right with the observed collapse propagation.

Freefall is MUCH FASTER than collapse propagation and you don't have to be a Physicist to see that.

The detached and falling NE corner is shown below



and you can see the falling perimeter NW corner piece on the right below (and, of course, the NE corner too).



I think it is rather obvious that the falling piece on the right clearly leading all objects is, in a practical sense, the DEFINITION of freefall.

If you want to compare collapse propagation to freefall, just compare it to the rate of fall of the object on the right.

Here is another photo of the same object, lower right



Since it fell from the collapse initiation region and is obviously a heavy object (and it had zero initial velocity downwards), isn't it practically by definition the standard of what freefall speed means?

Would it not be the natural reference object to determine how much slower than freefall the collapse progressed?

Major_Tom wrote:Here is another photo of the same object, lower right

Since it fell from the collapse initiation region and is obviously a heavy object (and it had zero initial velocity downwards), isn't it practically by definition the standard of what freefall speed means?

Would it not be the natural reference object to determine how much slower than freefall the collapse progressed?

Yes, do you know of a video from that angle?

Hambone wrote:
Here are some images from Chandlers presentation where I have marked other easily identified heavy debris which are moving significantly faster than the collapse front even though the collapse front most likely had a significant head start. (Note: The green and red markings are Chandler's.)

So the question then becomes "Are there any phases of the collapse where the collapse front progresses with an acceleration ~ g ?"

In other words, is there evidence of a CD progressing in a staccatto fashion?

Based on these stills, the claims that the collapse front always progresses at a free fall acceleration rate is false. However, there's no need for a CD to have such a characteristic.

This raises an interesting (well, maybe ) question: are CD's always pre-timed? I always thought so, but if you want a CD that's 'very' progressive (i.e., floors CD'd only when they are 'near' the bulk of the collapsing front; doing so will make the CD appear more natural, and less like a CD), unless you were supremely confident that you could calculate the speed of such a collapse ahead of time, what you'd want instead is to track the collapse visually, with telemetry feedback determining the sequence.

In doing so, you certainly would not spot outlier pieces of building that fell off at the very beginning of the collapse. The 2nd and 3rd stills posted by Major Tom in this thread make that clear.

Since the C in CD is for 'controlled', even if such is not the normal method of CD, that doesn't mean it's impossible.

It'd be interesting to know the vertical acceleration of the aluminum cladding that Chandler measured....

Yes, do you know of a video from that angle?

The only one that somewhat captures this piece is the BBC video below

http://www.youtube.com/watch?v=Xo7t3XQ2 ... re=related

Note: Most videos, including this one, are cropped to focus on the visible progression so this piece is usually cropped out of them. You won't see it unless you know where to look.

It is the same one Chandler uses. Comparison to this piece shows that the claim that the building fell as if in freefall is silly.



It doesn't show whether the collapse front progressed with a particular acceleration at any specific phase, As Metamars points out.

People who want to use fall time as proof of CD may ask what Metamars does:

So the question then becomes "Are there any phases of the collapse where the collapse front progresses with an acceleration ~ g ?"

Or greater than g?

Visual inspection of the BBC video suggests the answer is "no".

This can be determined by simply counting the number of floors consumed in any short interval of time at different moments during the collapse. If the number of floors consumed per "delta t" clearly changes over time, then an easy calculation can give you the rate of change of the number of floors consumed over "delta t", or acceleration (using floors as a measure of distance). d(d(floors consumed)/dt)dt

I don't see any "staccatto" progression in the destruction of floors, but it is always something to look for.

Major_Tom wrote:
I don't see any "staccatto" progression in the destruction of floors, but it is always something to look for.

Chandler has measured a jump in velocity, compared to the aluminum cladding. In a sense, that's a staccatto, but with only 1 beat.

If the aluminum cladding was falling with, say, net acceleration .9g, and the collapse front that he measured exceeded that, even if only for .2 sec, that would be suspicious. Especially, if such a pattern were repeated - i.e., staccatto.

Remember, if the 6 floor section gets a head start, even though acceleration due to gravity will be the same as for the cladding, of course it's vertical speed will exceed that of the cladding, even ignoring differences in wind drag.

metamars wrote:

Major_Tom wrote:
I don't see any "staccatto" progression in the destruction of floors, but it is always something to look for.

Chandler has measured a jump in velocity, compared to the aluminum cladding. In a sense, that's a staccatto, but with only 1 beat.

If the aluminum cladding was falling with, say, net acceleration .9g, and the collapse front that he measured exceeded that, even if only for .2 sec, that would be suspicious. Especially, if such a pattern were repeated - i.e., staccatto.

Remember, if the 6 floor section gets a head start, even though acceleration due to gravity will be the same as for the cladding, of course it's vertical speed will exceed that of the cladding, even ignoring differences in wind drag.

There appears---by the video---to be a degree of "pulsing". The term "staccato" (I'm a music major) refers to accented pulses there are clearly heard (or in this case, seen), as opposed to "legato" which lacks a definite pulse or accent.

The expulsions seen destroying the faces seem to pulse every 20 to 30 floors, die out and then pulse again. They, as expected, are beating the corner destruction, since the corners are the strongest part of a structure, as a general rule. This seems to be consistent with the "squibs" seen 20 or 30 stories below the collapse wave at any given time. If this were a demolition, the "squibs" would preceded collapse, creating a weaker structure for the upper rubble to pummel and that increased load would "pulse" the debris outward as it impacts broken debris below. The amount of resistance that slowed collapse can be inferred by the degree in which the corners survive beyond the walls. They do, but only for a few moments. A natural, gravity-driven collapse could produce "pulsing" as broken debris from above overwhelms the structure below, allowing a certain amount of pressure to be driven outward as we see. However, the apparent symmetry of the perimeter failure with little directional bias from the strain/compression force differences because of the plane impacts, is a cause for concern.

Part of this argument has raised an interesting thought in my mind. We could calculate resistance pulses of the building with the videos. These pulsations or rhythms occurring during collapse can shed light on the mechanism by way of understanding of the static oscillations vs. the dynamic oscillations during a collapse event. Vertical oscillations would be gravity system being overwhelmed outside the design load factors and the degree of destruction across a given floor would "pulse" an overload, even if not seen with the naked eye. A series of these rhythmic pulses, could conflate the more dynamic (visible) pulse by way of spring-like resistance felt over several floors, especially the mechanical floors, which evidently had outrigger structures to increase stiffness in the facade walls. The mechanical floors, by virtue of increased stiffness and the outrigger trusses, would be an increased burden on the falling debris, creating an excess of potential energy by way of out-of-plane flexing of the mechanical-floor structures. This could create the large pulses seen in the videos. A quantification of these pulses could show the degree in which the structure resisted collapse at certain points. Or, it could show how one would effectively demolish buildings such as these by way of a controlled progressive collapse scenario.

metamars wrote:

Major_Tom wrote:
I don't see any "staccatto" progression in the destruction of floors, but it is always something to look for.

Chandler has measured a jump in velocity, compared to the aluminum cladding. In a sense, that's a staccatto, but with only 1 beat.

If the aluminum cladding was falling with, say, net acceleration .9g, and the collapse front that he measured exceeded that, even if only for .2 sec, that would be suspicious. Especially, if such a pattern were repeated - i.e., staccatto.

Remember, if the 6 floor section gets a head start, even though acceleration due to gravity will be the same as for the cladding, of course it's vertical speed will exceed that of the cladding, even ignoring differences in wind drag.

We don't know that it is cladding. Maybe it is a curtain? Being that the point Chandler choses changes form, I suggest that there was some rotation which would give variable wind resistance.

Hi all,
First off, I was invited to join this forum. I don't have a lot of time or energy to invest in the discussions, but I do appreciate a forum where the focus is on evidence rather than trashing personalities.

My interest in using Physics Toolkit for 9/11 videos grew out of my amazement that the "collapsing" towers billowed out so much. I originally did a crude estimate of the ejection velocity of a chunk I could trace on a television screen and estimated horizontal ejections of over 60 mi/hr. When I realized I could import the videos into Physics Toolkit I came up with 72 mi/hr. This started the ball rolling. I looked around to find more things to measure that would be informative. I hope people will look at the results which are posted on YouTube at my channel: DavidSChandler or go to my website 911speakout.org.

The video being discussed here is low on my priority list of significance as a meaningful measurement. I am NOT trying to assert idealized freefall acceleration of the demolition wave. I assume (but have not measured) that the bulk of the material is moving at terminal velocity. In the video I repeatedly use the term "freefall through air". What I am trying to do is to make the point that the demolition wave is just that: a propagation of a series of explosions that move down the face of the building pretty well keeping pace with the material around it. You don't need pinpoint accuracy measurements to observe this. True, as a measurement it is a bit sloppy, but measuring the locations of dust clouds is an approximate enterprise.

The real meat of what I have to say is in the first part of the video. Here is a chain of explosions occurring far below the actual level of collapse of the building. What I didn't point out, but should have, is that they are also localized. They do not ring the entire building. They don't look like what would happen if floors were smashing together blowing out the air. Other videos show that different waves are propagating simultaneously down the building at very different levels. I have made another video for the AE911truth YouTube channel that makes this point explicitly, awaiting committee approval for it to be posted on the AE site. (As I write, I am realizing that the internal core columns form a rectangular array that is close to the walls on the E and W sides of the North Tower and farther from the N and S walls. That means explosives on the core columns would more easily blast out of the E and W sides of the building. I guess discussions like this can be fruitful after all!)

In any case, I agree that heavier chunks of stuff are probably still in freefall while the majority of the lighter debris is at terminal velocity. It is interesting that so much stuff is falling from higher than the level of the explosions we are seeing. That reinforces the idea that these explosions are not at the point of collapse, or even the point where most of the material is being ejected. If these are not planted explosives, what are they?

DavidSChandler --- Probably better to choose a more neutral descriptive term than 'explosions'. The term 'puffs' has been used on another thread here, the one devoted to the topic of these puffs occuring below the collapse front.

David B. Benson wrote:DavidSChandler --- Probably better to choose a more neutral descriptive term than 'explosions'. The term 'puffs' has been used on another thread here, the one devoted to the topic of these puffs occuring below the collapse front.

To the degree that "puffs" is an adequate adjective to describe these events, you have to stand in awe at the assumption that "explosions" somehow is more dubious a description. To me, "puffs" is what somebody does on a cigarette. Explosions don't have to come from "bombs".

I'll stick with explosions. That describes what I'm seeing. "Puffs" doesn't come close.

I haven't heard any explanations from the official narrative side of the spectrum that would account for these explosions of vast amount of material at high speed simultaneously on multiple floors many floors below the collapse zone racing down the building to more or less keep pace with at least medium-density material (whatever chunk I'm tracking...big enough to be consistently visible on this scale) falling through air nearby.

The closest approximation is floor pancaking, but I would remind everyone that NIST dumped FEMA's pancake theory in favor of the pile driver theory. But even the postulated pancaking doesn't convincingly explain what is observed as described above. There is another video showing the NW corner of the North tower. This same wave of explosions is visible from a different angle, along with another larger wave of explosions many floors higher. I recently did a video commentary on this clip, which is undergoing some in-group discussion before being posted on the AE911Truth YouTube site. Check there probably within ~1 week. Another video I did with commentary on another substantial wave of explosions is on YouTube called "South Tower Coming Down". It can be found on my DavidSChandler YouTube channel.