Solid Bodies versus Rubble: Results

[DaveThomasNMSR]

In the now-closed thread "WTC7 and the girder walk-off between column 79 and 44," Tony Szamboti said:

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.

My reply, from p. 86 of the thread:

Y'know, you should be careful what you wish for!

Tony's reply from p.87:

I am all for you doing a test with a bag of sugar or rice dropped on a scale and then pouring the same mass of loose sugar or rice onto the scale from the same height the bag was dropped and showing the results.

Tony's reply
from page 87:

There would be some effect due to proximity and it is on the order of milliseconds that each load would have to be applied with respect to each other to have a cumulative effect. However,the WTC rubble would not have been compacted until a significant number of stories were demolished and that would not have been right away, which is the point of the issue with the missing deceleration and the load required to continue the collapse early on.

Let's see what happens with Dave Thomas' new test, which he seems eager to do, with a bag of rice or sugar and poured rice or sugar. I think the proximity needs to be quite close and that is why I said little to no amplification will occur with the poured material.

My reply
from page 88:

Well, quality work takes time! All is shaping up nicely, with a VP of research giving the required nod to get me some high-speed camera time, complicated by the absence of the usual camera operator this week, and the travel status of said VP. So it could take a few days, yet.

Meanwhile, I have been loaned a mahvelous 60-pound scale, and can start in on the stiffness calcs tomorrow!

and more from
page 88:

Got a definite date, but it's still a couple of weeks away - Tuesday, Aug. 14th. (A TV science channel will be in town, and I get to piggyback on the time-consuming HS camera setup.)

Being a derail of the girder walkoff anyway, I'll just start a new thread when results are in.

Hasta luego, Dave

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:

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.

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.

 

[cjnewson88]

Well done Dave

+1

 

[Orphia Nay]

Nice work, Dave!

 

[Ivan Kminek]

Thanks, Dave, a good work)

 

[Scott Sommers]

Awesome! Thank you.

 

[femr2]

A quick and dirty trace of test #1...no static feature extraction...

(SG - 2 - 15)


It's a shame the video has a few trace related barriers...

1) The focus is pretty fuzzy.

2) There is no real-world scaling (known dimensions of the cradle could resolve that)

3) The camera is not precisely positioned.

4) As the trace point of interest is the "hook" beneath the meter, it's a shame the zoom was so far out.

5) I don't know the timebase. Video assumed to be standard ~29.97fps. The slowdown factor is unknown.

6) The video ends abruptly, rather too quickly.

7) Lighting is pretty dark, reducing potential accuracy.

...

If you do any more videoing, could I recommend placing the camera carefully exactly opposite the meter "hook", framing the shot as zoomed in as is practical, and providing information enabling conversion to real-world units of distance and time. Attaching a circular marker to the hook, with a black spot surrounded by white would be ideal

ETA: A trace of the bottom of the meter dial, quantifying static feature trace...

That motion will of course affect the graphs above when included.

 

[DaveThomasNMSR]

A quick and dirty trace of test #1...no static feature extraction...

[qimg]http://femr2.ucoz.com/_ph/9/948883068.png[/qimg]

[qimg]http://femr2.ucoz.com/_ph/9/202261047.png[/qimg]

(SG - 2 - 15)


It's a shame the video has a few trace related barriers...

1) The focus is pretty fuzzy.

2) There is no real-world scaling (known dimensions of the cradle could resolve that)

3) The camera is not precisely positioned.

4) As the trace point of interest is the "hook" beneath the meter, it's a shame the zoom was so far out.

5) I don't know the timebase. Video assumed to be standard ~29.97fps. The slowdown factor is unknown.

6) The video ends abruptly, rather too quickly.

7) Lighting is pretty dark, reducing potential accuracy.

...

If you do any more videoing, could I recommend placing the camera carefully exactly opposite the meter "hook", framing the shot as zoomed in as is practical, and providing information enabling conversion to real-world units of distance and time. Attaching a circular marker to the hook, with a black spot surrounded by white would be ideal

ETA: A trace of the bottom of the meter dial, quantifying static feature trace...

[qimg]http://femr2.ucoz.com/_ph/9/612551636.png[/qimg]

That motion will of course affect the graphs above when included.

Very interesting, femr2, thanks for posting this!

I don't know if I will re-do this one, but if I do, I will take your suggestions to heart.

If I decided to just chuck the clunky scale next time, and use visual motion tracking and analysis as you have done - what do you think would be the best impact surface? Plexiglass with a flag for tracking motion? Idears?

Thanks, Dave

 

[carlitos]

You're just a shill for Big Physics.

 

[tsig]

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.

Will it be ignored or hand waved away? Stay tuned to this station for our exciting conclusion.

(well done Dave)

 

[femr2]

Very interesting, femr2, thanks for posting this!

You're welcome.

I don't know if I will re-do this one, but if I do, I will take your suggestions to heart.

Cool.

If I decided to just chuck the clunky scale next time, and use visual motion tracking and analysis as you have done - what do you think would be the best impact surface? Plexiglass with a flag for tracking motion? Ideas?

I'd suggest there's a number of issues there...

Without the clunky scale, there's no calibration. Dropping something on something else that doesn't give way provides little information. Dropping something on something else that does give way requires information about the material giving way.

The information, as I see it, that comes from your tests, is the difference between the various tests, not their absolute "values".

In terms of increasing trace accuracy and fidelity (in order to provide the most accurate displacement/time, velocity/time and acceleration/time profiles) I'd suggest...

a) repeating the same experiments, using the same equipment, but...

b) Placing a marker on the "hook". (a circular piece of white card/wood with a black circle in the middle is ideal)

c) Placing a marker on the dial of the meter. Under the number 5 would be good.

d) Filming only the two markers as closely, as well lit, as possible.

e) Placing two rulers in-frame, one vertical the other horizontal, to allow accurate conversion from pixels to real-world units.

f) Uploading the original binary video data, rather than letting youtube mess with it.

Bottom line is your point is kinda proven already, but if you're interested in looking at acceleration behaviour (of the undoubtedly damped system) in more detail, I'm quite happy to perform the relevant tracing process.

It is useful for me personally to see the behaviour of the "fixed" meter (the last graph) which proves the need to consider static feature extraction.

It is useful for me personally as additional "validation" of the trace techniques used to provide motion trend behaviour for WTC1, 2 & 7.

It may be useful for you to have more detailed empirical data about the difference between motion behaviour for your various tests. Much more informative than the singular "peak" value you have at present, as the time dimension can be included.

 

[LSSBB]

Will it be ignored or hand waved away? Stay tuned to this station for our exciting conclusion.

(well done Dave)

I agree, great work, Dave.

Now it's time for Truthers to live up to their challenge: demolish a building with unobservable devices.

 

[Architect]

Well done, Dave

 

[Justin39640]

Obviously the dial indicator was CGI'd.

 

[femr2]

For those interested...the difference in displacement behaviour between bagged and loose...

I suggest there are factors to account for, such as the reaction of the cradle, scale and supports...for the bagged "impact".

 

[thedopefishlives]

For those interested...the difference in displacement behaviour between bagged and loose...

[qimg]http://femr2.ucoz.com/_ph/9/653746227.png[/qimg]

I suggest there are factors to account for, such as the reaction of the cradle, scale and supports...for the bagged "impact".

That is an absolutely fascinating graph. I honestly had no idea how "smooth" (in a very qualitative sense) the impact of a loose material like that could be.

 

[LSSBB]

That is an absolutely fascinating graph. I honestly had no idea how "smooth" (in a very qualitative sense) the impact of a loose material like that could be.

Makes sense to me, the individual particles would have freedom of movement so the noise should closely follow a normal distribution.

 

[femr2]

Comparing static motion...that is the motion of the meter itself...

Tends to explain the rather flattened profile of the bagged displacement trace.

Whatever the meter is hung from is not rigid, and so when the bagged rice impacts the meter itself is set into oscillatory motion.

Reduces the "difference" between the two meter readings somewhat I would say, but it should be noted that the scale of meter oscillation is still only half of the difference between peak bagged and loose displacement.

 

[femr2]

While the bagged rice hits all at once, the loose rice does a "rope-a-dope" action that actually intensifies the impact!

I suggest caution when interpreting your meter readings, as there are undoubtedly other factors at work, such as reaction of the cradle, chain, meter and whatever it is hung from.

The impact is not "intensified", of course, simply "extended", which has an effect upon the equipment being used.

 

[femr2]

Discuss.

Whilst this is the last port of your post, I'm starting here as I don't see anyone actually discussing anything, but instead just "+1"-ing.

Perhaps that is due to limited understanding, who knows...

It is good that you have spent the time and effort performing the tests, but it's important to ensure results are "put out there" with clear interpretation and scope details provided.

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.

The response of the "clunky old scale" is obviously very important to correct interpretation, as it clearly and significantly affects your results. You have alluded to this above, and within the video. Others here may have missed the point.

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!

No.

The disassociated mass does not apply more force than a solid of the same mass.

It is side-effects of the (heavily damped) experimental setup which create those results.

the bagged rice hits all at once

There is likely a little "slack" in the bag, but for sake of simplicity, sure.

the loose rice does a "rope-a-dope" action that actually intensifies the impact!

No, whatever you mean by "rope-a-dope".

Again, the reaction of the equipment is obviously a significant factor.

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!

Quantifying the response of the equipment, impacting object(s) and impacted surface is a can of worms.

In order to "simulate" a WTC-type environment, you'd need to quantify the strength of "floor supports"...

Make a platform with a square hole just larger than your "floor tray". The platform needs to be solid, on solid ground.

Glue a number of matchsticks exactly half way over the internal edge...sticking out so as to be able to support your tray.

Gradually add mass until the matchsticks fail. Repeat until you can select the right number of matchsticks so as to be able to support, say, 3 times your static mass.

You get the picture...

The only "result" as such is how slowly you have to pour the "static mass" in order for the floor supports to NOT fail.

 

[LSSBB]

Whilst this is the last port of your post, I'm starting here as I don't see anyone actually discussing anything, but instead just "+1"-ing.

Perhaps that is due to limited understanding, who knows...

It is good that you have spent the time and effort performing the tests, but it's important to ensure results are "put out there" with clear interpretation and scope details provided.


The response of the "clunky old scale" is obviously very important to correct interpretation, as it clearly and significantly affects your results. You have alluded to this above, and within the video. Others here may have missed the point.


No.

The disassociated mass does not apply more force than a solid of the same mass.

It is side-effects of the (heavily damped) experimental setup which create those results.


There is likely a little "slack" in the bag, but for sake of simplicity, sure.


No, whatever you mean by "rope-a-dope".

Again, the reaction of the equipment is obviously a significant factor.


Quantifying the response of the equipment, impacting object(s) and impacted surface is a can of worms.

In order to "simulate" a WTC-type environment, you'd need to quantify the strength of "floor supports"...

Make a platform with a square hole just larger than your "floor tray". The platform needs to be solid, on solid ground.

Glue a number of matchsticks exactly half way over the internal edge...sticking out so as to be able to support your tray.

Gradually add mass until the matchsticks fail. Repeat until you can select the right number of matchsticks so as to be able to support, say, 3 times your static mass.

You get the picture...

The only "result" as such is how slowly you have to pour the "static mass" in order for the floor supports to NOT fail.

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