telekinetic

Someone on reddit asked this question here, and it got me thinking. Well, first it got me thinking, then it got me googling, and I found the internet almost devoid of information about the compressive strength of a LEGO brick.

I aim to fill this void, and hopefully answer this question: How many LEGO bricks can you stack, one on another (assuming perfect balance, of course) before the bottom one crushes from the weight of the stack?

Supplies:

Compression tester (to strength test a small stack of bricks)
Digital Scale (to weigh individual bricks, although I think I remember hearing they are 2.5grams)
Calculator (to divide the failure force by the weight of a single lego)
LEGO bricks (reasonable supply to allow for experimentation)

Note: I have a tensile tester at work that I am *hoping* will run in reverse...if not, I will have to make a crush fixture so I can test it in tension.

I did some preliminary testing with a few of the bricks I had at my desk on an arbor press, and it is clear that the studs on the top brick are going to be a problem--they fail WAY before the brick actually starts to lose integrity. I was going to sand them down, but then I remembered they sell flat plates, so I swung by the LEGO store after work to pick up some supplies for tomorrow. Also, I forgot my camera.

Anyways, any guesses? I'll keep this thread up to date, and probably make a youtube video when I'm finished with all my testing and have results.

Hint: It's probably a LOT

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Jetée

the 2x4 LEGO brick will have a different threshold than a square 2x2 (4 total) peg brick; so what I have to offer (now that I am totally devoid of a single LEGO brick, and I hate it) is to stay consistent and use only one type of brick, if possible.

here are the most common forms of the bricks: http://idletigers.files.wordpress.co...resolution.jpg

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spindles

I reckon it'll fall over before the bottom one crushes

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BadNick

Here's some "strength of lego" information to hold you over until your testing gets going

telekinetic

I'm focusing my testing primarily on the 2x4, though I do have the supplies to do a couple of 2x2 tests. It is interesting to speculate about which you could stack higher.

As a note, my parents have all of my remaining LEGO bricks, so I picked some up specifically for this. I crushed four today, and it made me realize something: I had never before seen a broken lego...it was kind of unsettling and sad to see one mushed, and no longer useful.

Nevermind that...I must press forward...for SCIENCE!

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Plan9

You're a bipedal Discovery Channel prime time piece, Tele. Onward!

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inBOIL

I wonder if the color of the brick affects its strength.

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telekinetic

Good question...as you can see by the supplies I've collected, I'm well equipped to investigate!



I was disappointed I couldn't find a clear brick, though...I suspect they may be more brittle.

By the way, based on my preliminary tests today, I think I'm going to test three brick stacks topped with flat tiles, like shown between the arrows.

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The_Jazz

I know from experience that a Lego will not break under the full weight of a 180 lb man while on a hardwood floor.

One of the pitfalls of parenthood.

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Redlemon

I used to have a contact over at LEGO in Enfield, CT, but that was long ago.

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telekinetic

Ack, the dreaded interAdmin Threadjack!11!

Anyways, I did some preliminary testing in a manual press just to make sure I understood the failure modes.

I crushed one brick by itself...and holy crap, did that take a lot of force. I was using a manual arbor press with probably a 20:1 force multiplication, and I still almost had my feet off the floor pulling on the handle:

(sorry for the noisy pictures, I wasn't using a flash and am too lazy to retake them)
This isn't a good test of how a column of LEGO bricks would fail, however--for that, we need to test a small stack, starting with 2:



I quickly learned two things: these are very sensitive to asymmetrical loading, as you'd expect in something that is failing in what amounts to a fancy buckling mode, and that the studs crush in way before the rest of the brick is near failure.

To mitigate the stud crushing, I tried a double stack with flat caps:



This was TREMENDOUSLY strong. I was actually very impressed. It may just have been that this one was centered under the press better than the others or something, but it had a much stronger failure mode than any of the other stacks I tested. However, there was still too much going on with the top block, so I added a 3rd to help isolate the failure to the middle and bottom blocks, simulating the large weight above:



This is another one that was a bit off center, and so had a rather boring failure mode. However, the top brick survived nearly unscathed, so I think that justifies my '3 bricks with flat tile tops' technique. To check and see if the studs were intact, I popped the tiles off the top brick:



You can't really see it, but they're completely pristine. Looks like we having a winning combination.

Stay tuned for our first calibrated runs, hopefully later today!

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BadNick

btw, I think the size of the Lego brick will factor out of the analysis because compressive strength is in units along the lines of "pounds per square inch" so if you have more square inches to distribute the load, the load will be higher...while the "psi" compressive strength would remain the same...excuse my lack of metric units which totally suck anyway.

Perhaps consider testing both the 4X2 and 2X2, record both the load at failure and the area it was applied to; then see if the "load per area" remains about the same.

Since the venerable Tinius Olsen company is right down the street from where I work, I looked at their site knowing that they're a bunch of whackos over there, and wouldn't you know it ...see the caption to Figure 18 in this brochure: http://www.parameters.com.au/library...ngMachines.pdf

Perhaps we should ask them if they can share their data as a check of telekinetic's work.

dlish

i was going to mention the area of the bricks, but badnick's beat me to it.

if you're applying the same load to a small brick as opposed to a larger brick, the rate at which the bricks will fail will probably change, dependant on the surface area that the brick has in contact with what's underneath it.

looks like an interesting thread with many possible scenarios. a ripe scenario for inquisitive minds. god damn engineers!

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telekinetic

I had originally thought so, too, however we have to consider a few factors. First of all, the wall thickness is constant, so smaller bricks are going to have thicker walls relative to their area. Second, the 'web' in the longer-than-2x2 bricks is not nearly as thick as a wall thickness. Third, one of the frequent failure modes above is the shearing off of the wide side of the long bricks, which makes me think they are geometrically inferior.

I have enough 2x2 blocks that I can test some and see if there's a correlation, but I figured I'd start with a comprehensive test of the 2x4, as it is the most typical 'LEGO,' and then go from there. I'm also curious if any interlocking brickwork patterns can get them closer to their ultimate strength per-brick than just a simple one-on-top-of-the-other stacking.

Tinius Olsen you say? Here's the 8-foot-tall 10,000+lbs-capable testing rig I'm going to be using:


Here's a close-up view:



Small world

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Daniel_

I have a suspicion that given the failure mode includes the sides "balooning" out, if you built a tower that is 4 x 4 studs using 2 x 4 bricks with a 90 degree rotation between each pair in your 3 high stack, the pressure will be more than double the 4 x 2 stack alone.

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BadNick

Your point about the structural difference between the small and large bricks is a valid point so you're on the right path.

Before I looked at the Tinius Olsen site, I was going to call over to the mechanical and civil engineering labs at my old alma mater, Villanova U., since they have some large Tinius Olsen machines, as well as my old favorite, the Instron which was able to maintain a constant test load even as the test sample distorted. However, I figured that they're all probably over there crying in their beers for blowing their chances to get into the NCAA basketball final sweet sixteen ...to St. Mary's no less! Isn't that a girl's school?

MSD

By the time you're done with this experiment, I hope to have figured out a suitable award to give you for your contribution to science.

Hard8s

One, Two, Three, Crunch
It takes three licks to get to the center of a tootsie roll pop!!!!

Ooops
Wrong question!!!!

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Redlemon

Any updates yet?

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Martian

I am breathlessly awaiting the results. This information is crucial to the design of my Lego Machine of Doom.

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AquaFox

this is sweet. this thread will have potential to be quite famous... i'll be seeing it on digg in no time at all... followed by cnn and all the others :-)

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...AquaFox...

BadNick

I've already been approached for interviews and I think it's just because I posted in this thread. I thought I saw Lego paparazzi driving by my house the other day.

Jeon

Don't worry BadNick, that was just me. I'm a stalker in my off time. Gives me something to do.


Seriously though... anybody got any results yet? ^_^

Zeraph

Totally awesome thread. For great science!

Payo2000

Has anyone seen Telekinetic recently?

I am worried that he might be lying buried under by a huge avalanche of 2x4 Lego bricks.

Can someone go around to his house to make sure he is OK?

BadNick

I hope this isn't telekinetic!



anybody have his number? I'll call him on my phone.

Payo2000

try 7337 - 1390

Zooksport2

Adam and Jamie should have some spare ones. Give them a call!...

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