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Solid Bodies versus Rubble: Results

LSSBB said:
Such an experiment as you outline will also need to take scaling factors into account if it is not a 1:1 replication of the WTC1 / 2
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If the intent was to replicate a Tower storey, sure, and a thousand other factors.

Luckily, that's not the purpose.

The "question" on the table is simply force applied by solid vs rubble for the same total mass....possibly with different "flow rates".

It is obvious that the scale method in the video above produces potentially misleading results...thus suggestion of an alternate measurement method which is not similarly affected.

By all means suggest a method which resolves issues identified with that within the video.
 
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Or better still...

Use a Wii Balance Board.

Four independent 16bit calibrated realtime pressure sensors, with excellent accuracy, able to provide readings up to 150Kg (Though able to sustain 300Kg).

I'd estimate 2dp accuracy in Kg, spitting out readings as fast as you can grab them over bluetooth, plus the ability to determine centre of mass.

Open Source Library is available here.

I may even do the legwork myself. Might be interesting.


Certainly the "hobbyist" solution to this problem.
 
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femr2 said:
Or better still...

Use a Wii Balance Board.

Four independent 16bit calibrated realtime pressure sensors, with excellent accuracy, able to provide readings up to 150Kg (Though able to sustain 300Kg).

I'd estimate 2dp accuracy in Kg, spitting out readings as fast as you can grab them over bluetooth, plus the ability to determine centre of mass.

Open Source Library is available here.

I may even do the legwork myself. Might be interesting.


Certainly the "hobbyist" solution to this problem.
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That sounds like a practical suggestion, and I will look into it! :)
 
DaveThomasNMSR said:
That sounds like a practical suggestion, and I will look into it! :)
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Readings can be taken at 100Hz.

Comparison with Kistler force plate 9287CA
208143945.jpg


Ideal.
 
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One way to look at it, in a first year physics sense, is to note that force is the change in momentum over time. For a platform that does not fail then, the change in momentum of the solid load(full bag) will occur over a shorter time period than if that same mass takes longer to see a change in momentum, ie. less force.
But
The amount of energy expended will be the same.
Energy available in both cases is simply the gravitational potential due to the height of the drop, same mass and same height means same energy.

Similar to femr's experiment above:
Create a platform and slowly load it with small weights until the platform fails.
Reduce the number of weights by half and you have a two fold margin of 'safety'.
Now drop these weights on a platform, of same design, at a rate of 2 per second
If the platform does not fail, then next trial have weights drop at a rate of 3 per second. Each trial increased the rate by one weight per second until platform fails.

You now have a force equal to that of the static load failure point but using only half the mass.

If you really want to go nuts with this, do another set out trials but double the drop distance.

Of course each trial must be done on a new platform so your budget might dictate a small model. I suggest that staple of first year engineering, Popsicle sticks, for columns and beams, 1/8th inch plywood for the platform, and 3/4 inch washers for the weights.

If you want to see column failure rather than platform failure then use 1/4 or 1/2 inch plywood.
 
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DaveThomasNMSR said:
In the now-closed thread "WTC7 and the girder walk-off between column 79 and 44," Tony Szamboti said:



My reply, from p. 86 of the thread:



Tony's reply from p.87:



Tony's reply
from page 87:


My reply
from page 88:



and more from
page 88:


Well, here I am, a new semester about to start, and I thought I'd clear off a couple items from my desk.

The experiment is in! Here's the YouTube:


Now, the responses weren't quite as large as I'd been expecting, which I think is due to the instrument response of the clunky old scale. I tried a few quick experiments with various accelerometers, and didn't get all my questions resolved.

What I did find throughout, and what is important, after all, is the simple fact that the rubble piles pack as much or more force than the solid counterparts!

Take a look at the rice in the video above. While the bagged rice hits all at once, the loose rice does a "rope-a-dope" action that actually intensifies the impact!

Bottom line:

Also, if anyone has ideas on how to configure a good comparison with good accelerometers, let us know here. I'm telling you, it's a little trickier than you might think!

Discuss.
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I find your results as expected. Then again, I've seen the aftermath of enough rock slides and snow avalanches, including fairly large tree trunks broken that I know that unconsolidated mas moving with some velocity, propelled by gravity, can do a lot of damage. I've always thought that the notion that the top part of the building couldn't damage the bottom part after it had broken up was one of the sillier of the many silly ideas of truthers.
 
It is to be expected that a loose mass will impart a lesser instantaneous force on the platform than a solid mass. That dynamic force depends on the time it takes to transfer the momentum of the mass to the platform. In that case of a solid mass that time is much shorter and thus the force is greater.
However, in applying this to the collapse of the WTC towers this begs the question; "is the difference between the force applied by a solid mass consisting of the upper falling portion(an idealized situation that does not directly represent reality), and the force applied by a loose mass consisting of the components of the upper falling portion of the structure, enough to arrest collapse?"

The first, a solid mass, is the limit at one end of the scale, and an idealized situation at the other end would be to consider that mass to consist of, say one million equal mass components. However now you would have to idealize the separation between particles since if there is no separation there is no difference.
In reality the separate falling components were not 'poured' onto the lower structure, as was suggested for the sugar drop experiment.(note to MT; I am not refering to large portions of the upper section falling at different times. Dividing the upper portion into only three or four large parts would be a different case)
Thus one now has to ask if this exercise is moot.

You have one limiting case, solid upper section, in which the lower struture cannot arrest collapse, and you have an opposing limiting case in which it can be assumed that the difference in transfer of momentum from that of a solid block will be very small due to the small separation of individual falling components.


In order to reduce the force significantly in Dave's experiment(and one that the 'clunky old scale' could react to) one would have to pour the sugar or loose rocks out over a significantly longer time than is afforded by a simple trap door. Unfortunately as soon as you do that you also move, obviously, well away from the reality that was the collapse of the WTC towers. Once again, as pointed out by ozeco, gravity delay is a concept unknown to science at this time(at least not in less than astronomical values of distance)

If we are to assume a significant difference in the force of the non-solid falling mass there must a significantly longer time of transfer of momentum. So to use this in the reality of the WTC collapses, TSz et al, will have to explain how this occurs and have that explanation not contradict the sequence of collapse as recoded in the videos.
 
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femr2 said:
What is the diameter of the scale dial ?

What factor of slowdown was used ?
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The outer diameter of the scale is 38.2 cm.

The fame rate was 1000 frames per second. I estimate the clip for loose rice was 675 frames, so about 0.675 seconds.

Does that help?
 
jaydeehess said:
...In order to reduce the force significantly in Dave's experiment(and one that the 'clunky old scale' could react to) one would have to pour the sugar or loose rocks out over a significantly longer time than is afforded by a simple trap door....
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Dave's experiment was a great first effort. However to refine it would require that the oscillation/resonance/damping effects and the subsumed aspects of mass and inertia be accounted for. Doing that would not be a trivial exercise. Moderately easy to explain in qualified terms - far more difficult to quantify. (I'm game if there is any interest but....)(EDIT: Ooops...I meant game for the "qualified explanation" - not the quantified version.)

jaydeehess said:
.. the one factor that needs to be Unfortunately as soon as you do that you also move, obviously, well away from the reality that was the collapse of the WTC towers.
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Remember the origin of this experiment was a challenge by Tony Sz. It arose in the context of rebuttal of some bits of Tony nonsense. There are far easier ways to prove that Tony is wrong on the original bit of nonsense. So be sure of the objective:

1) If it is "show that Tony was wrong" use the easier methods;
2) If it is "meet Tony's challenge to measure using scales" that objective already met and doesn't need a more sophisticated approach to the already demonstrated experiment. IIRC there was no accuracy specified in the challenge; AND
3) If it is "prove Tony wrong on his original false claim"...that should be unnecessary for anyone with basic physics expertise.
jaydeehess said:
..Once again, as pointed out by ozeco, gravity delay is a concept unknown to science at this time(at least not in less than astronomical values of distance)
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Ah "the prophet is not without honour, save in his own country" (A Hitler 1941 - quoting an earlier authority. ;)) (Alternatively "The voice of one proclaiming in the wilderness..." - that one also slightly out of context. :o)

jaydeehess said:
..So to use this in the reality of the WTC collapses, TSz et al, will have to explain how this occurs and have that explanation not contradict the sequence of collapse as recoded in the videos.
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Whilst that is true the even more basic need is for Tony to take on board the two fatal errors in his "Missing Jolt" fantasy:
1) The obvious one that he took literally the assumptions of the Bazantian abstraction and applied them to the "real event"; AND
2) His assumed mechanism was an anachronism - from his "starting point" he was looking for a future event of a jolt. The time for the jolt was already past at his starting point. That one is not as obvious - it needs a bit of thought - and a reasonable understanding of the 4D event of cascade failure that we call "initiation". :teacher:
 
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Dave,

The response has to do with the frequency with which the loose items hit the scale and the velocity of the elastic wave response. The frequency of the suspended scale you are now using is surely much lower than the scale you used previously.

If the pieces of loose rice are hitting the scale at a much higher frequency than the elastic wave frequency the response will be as though they were one large unit. This is hardly the same as loose rubble hitting stiff structure.

I think you need to stop changing more than one variable at a time. There is a big difference between the suspended scale you used recently and what you dropped your bag of rice on in this video http://www.youtube.com/watch?feature=player_embedded&v=SozKaHYD85Q

Please drop the same amount of loose rice you dropped in a bag onto the scale used in your earlier video and as shown on this page http://www.nmsr.org/nmsr911a.htm and get back to us.
 
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Tony Szamboti said:
Dave,

The response has to do with the frequency with which the loose items hit the scale and the velocity of the elastic wave response. The frequency of the suspended scale you are now using is surely much lower than the scale you used previously.

If the pieces of loose rice are hitting the scale at a much higher frequency than the elastic wave frequency the response will be as though they were one large unit. This is hardly the same as loose rubble hitting stiff structure.

I think you need to stop changing more than one variable at a time. There is a big difference between the suspended scale you used recently and what you dropped your bag of rice on in this video http://www.youtube.com/watch?feature=player_embedded&v=SozKaHYD85Q

Please drop the same amount of loose rice you dropped in a bag onto the scale used in your earlier video and as shown on this page http://www.nmsr.org/nmsr911a.htm and get back to us.
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I might be able to do that. It can take awhile to arrange the high-speed filming necessary. The main reason I went with the large scale (which turned out to have a clunky instrument response) in the first place was that you asked for at least 2 to 5 pounds to be drop-tested:

Here is something anyone can do.

Take a 5 lb. bag of sugar or 2 lb. box of rice and put some sides around a scale with ounce graduations with at least a 10 lb capacity, and pour the sugar or rice from the same height as what Dave Thomas dropped his bag of rice from. I'll bet you don't see much more than 5 lbs. for the sugar or 2 lbs. for the rice if any at all.
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With luck, I'll get some new results within a month or so. I'll probably have to make a new trap-door release to use with the smaller scale. I'm also looking at trying out the Wii balance board test Femr2 has suggested.
 
DaveThomasNMSR said:
I might be able to do that. It can take awhile to arrange the high-speed filming necessary. The main reason I went with the large scale (which turned out to have a clunky instrument response) in the first place was that you asked for at least 2 to 5 pounds to be drop-tested:



With luck, I'll get some new results within a month or so. I'll probably have to make a new trap-door release to use with the smaller scale. I'm also looking at trying out the Wii balance board test Femr2 has suggested.
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Use the original scale and don't change anything but the bag restraint on the rice.

If you change the scale, drop height, or anything else, your results will not be valid, since there will be differences in the response that there would not have been in a direct comparison.
 
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Tony Szamboti said:
Use the original scale and don't change anything but the bag restraint on the rice.

If you change the scale, drop height, or anything else, your results will not be valid, since there will be differences in the response that there would not have been in a direct comparison.
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I can use the original scale, drop heights, compensate for the slight bag weight with a few grains of rice, etc, to get a fair comparison of loose versus bagged. I intend to re-design the trapdoor, since a bilaterally-symmetric two-door trapdoor imparts less horizontal motion than the one-sided door I used with the small scale.

I will repeat the new experiment on both bagged and loose rice, so it will be a fair comparison of loose versus solid. If that doesn't work for you, please let me know before I start doing the new experiment.
 
Might you shrink-wrap the rice and suck the air out of it to make it more solid? Like a brick of rice? There is still going to be some looseness in a bag of rice. Not sure if this would be significant, and if the "brick" doesn't hit flush, there would be deflection issues... Just thinking out loud.
 
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