• Quick note - the problem with Youtube videos not embedding on the forum appears to have been fixed, thanks to ZiprHead. If you do still see problems let me know.

Solid Bodies versus Rubble: Results

femr2 said:
I'll be looking at the WBB soon
Click to expand...

Early tests...

131436899.png


16061659.png


285073749.png


Should prove useful.
 
I was moving some cement blocks around my yard the other day and dropped one an inch or two on a finger. After the cussing ended I thought back to this thread. I thought about how much that hurt and wondered what dropping a few tens of thousands such bricks on me from more than a couple inches would do. I'm surprised they found any remains..
 
femr2 said:
Early tests...

[qimg]http://femr2.ucoz.com/_ph/9/131436899.png[/qimg]

[qimg]http://femr2.ucoz.com/_ph/9/16061659.png[/qimg]

[qimg]http://femr2.ucoz.com/_ph/9/285073749.png[/qimg]

Should prove useful.
Click to expand...

Very interesting! I estimate the WBB "spring constant/stiffness" to be about 2600 newtons/meter.
 
DaveThomasNMSR said:
Very interesting!
Click to expand...
Testing is ongoing, but promising. I'll perform a number of solid-vs-loose tests shortly.

I estimate the WBB "spring constant/stiffness" to be about 2600 newtons/meter.
Click to expand...
:confused: How ?

The WBB uses four pressure sensors, with effectively zero travel. I don't know the exact hardware details, but it is probable that the electrical resistance is affected by pressure, not physical travel.

There's (very) slight play in the "feet", but given the board will register accurate mass over 350Kg, I don't see how your value can make any sense.

I think it's meaningless, but (using 350Kg and a massive 2mm travel) would give a "spring constant/stiffness" of 1,716,750 N/m
 
Last edited:
The scale of distortion of the metal is suggested as under a millimeter for a 220lb load.

It's not awfully meaningful, as displacement is not the direct mechanism, but that would give a ballpark spring constant of ~1,000,000 N/m.
 
femr2 said:
Testing is ongoing, but promising. I'll perform a number of solid-vs-loose tests shortly.
Click to expand...

I look forward to the results. I want to know if my understanding, as outlined in my posts earlier, is correct.

In short I predict that the loose material test will show a very small lessening of max force. That is, if the difference is measurable. If not then may I suggest a slower 'pour' to compare. In other words, how diffuse does the material have to be to see a measurable difference?
 
Last edited:
jaydeehess said:
I look forward to the results. I want to know if my understanding, as outlined in my posts earlier, is correct.

In short I predict that the loose material test will show a very small lessening of max force.
Click to expand...
It's a reasonably straightforward problem to solve mathematically. Depends on the rate of dropping the material. The complicating factors arising from the weight/mass of the sprung part of scale and the containment devices. The aspects of movement, momentum, rebound and the timing of the rebounds, complicated further by resonance and damping effect which could see some of the distributed drop landing on the rebound cycle etc etc.

In the original DTNMSR experiment those factors could easily have been large enough to affect the outcomes. They were certainly enough to cause me to have reservations. With femr's WBB I'm confident that those aspects are so small as to be discounted.

IIRC the original reason for this was a two part claim raised by T SZ. Part one a false claim about the impact of particulate mass - which is obvious on examination and doesn't need experimental proof. However part two arose when T Sz made a challenge to prove it by experiment. Other than that challenge the experiment is redundant to proving the underlying issue.
 
jaydeehess said:
I look forward to the results. I want to know if my understanding, as outlined in my posts earlier, is correct.

In short I predict that the loose material test will show a very small lessening of max force. That is, if the difference is measurable. If not then may I suggest a slower 'pour' to compare. In other words, how diffuse does the material have to be to see a measurable difference?
Click to expand...

I'll be testing various "pour rates".
 
ozeco41 said:
It's a reasonably straightforward problem to solve mathematically. Depends on the rate of dropping the material.
Click to expand...
Indeed. Virtual world behaviour is a no-brainer.

The complicating factors arising from the weight/mass of the sprung part of scale and the containment devices.
Click to expand...
Instrument response is certainly a factor, but I think we need to move away from "springs" a little, given the WBB determines mass by change of resistance, nt displacement. There IS some post-impact oscillation, which recovers in the order of 0.05s.

It's clear that these experiments speak volumes about the importance of "what is impacting what".

Pre-stressing the plate has helped, minimising the "empty" response. Peak mass increased and recovery time reduced when the plate was pre-stressed when compared to the same mass drop without pre-stressing.
 
femr2 said:
I'll be testing various "pour rates".
Click to expand...

I suspect you don't care for the term 'pour' in this respect. I know I don't since wrt the WTC collapses there was no 'pouring' in effect.

It brings up an imagery of delayed gravity, and we've already been there.

However with lack of a better term, 'pour rate' would suffice.
 
Last edited:
ozeco41 said:
It's a reasonably straightforward problem to solve mathematically. Depends on the rate of dropping the material. The complicating factors arising from the weight/mass of the sprung part of scale and the containment devices. The aspects of movement, momentum, rebound and the timing of the rebounds, complicated further by resonance and damping effect which could see some of the distributed drop landing on the rebound cycle etc etc.

In the original DTNMSR experiment those factors could easily have been large enough to affect the outcomes. They were certainly enough to cause me to have reservations. With femr's WBB I'm confident that those aspects are so small as to be discounted.

IIRC the original reason for this was a two part claim raised by T SZ. Part one a false claim about the impact of particulate mass - which is obvious on examination and doesn't need experimental proof. However part two arose when T Sz made a challenge to prove it by experiment. Other than that challenge the experiment is redundant to proving the underlying issue.
Click to expand...

This is why I am interested. Although I understand the principles behind it, I am not sure at what point in varying the 'pour rate' you will see a significant change in max force.
I understand that no matter what the 'pour rate', the energy absorbed will be the same, just the time period over which it is used will change.
Basically its the dynamic nature of the situation that takes me beyond my physics knowledge and is more the realm of you engineers. Though I have an intuitive grasp of what will take place I cannot express it in the math.
 
jaydeehess said:
I suspect you don't care for the term 'pour' in this respect. I know I don't since wrt the WTC collapses there was no 'pouring' in effect.

It brings up an imagery of delayed gravity, and we've already been there.

However with lack of a better term, 'pour rate' would suffice.
Click to expand...

Various materials (sugar, rica, pasta, gravel, LEGO) will be looked at, as will various "structures", rather than varying scaled "grains".

But, yes, I'm not keen on pour. Controlled material/structure release ?
 
You must log in or register to reply here.

Back
Top Bottom