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Shapeways Ask an Engineer #2: Strength and Structure (VIDEO)


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:-) nice.
#1 wedge (Homepage) on 2013-02-19 14:54 (Reply)
Great experiment! My partner - the ultimate scientist hero - suggests that a more equal experiment would have been to place either vertical or horizantal struts on the square-test. That way both cubes would have the same or similar amount of material. He postulates that you would get a similar result, but it would better illustrate the power of triangles vs rectangles.
#2 T. Shawn Johnson (Homepage) on 2013-02-20 20:28 (Reply)
Great ! but you guys shoud work on the quality of these videos :

audio
video
editing
inntro etc...

just trying to be constructive ;-) keep up the great work !
#3 giorgio (Homepage) on 2013-02-21 17:46 (Reply)
At 2:20, do I spy some little tensegrity structures?
#4 psuedonymous on 2013-02-21 18:08 (Reply)
Good stuff guys, but I think there's a great possibility that you're selling yourselves short in saying the triangular structure is twice as strong. I understand that you are not trying to prove some sort of abstract scientific theory, but by using the 2-soda-cans-instead-of-1 reasoning, you're implying that the structural load limits of the square structure cube and the triangular structure cube are 1 soda can and 2 soda cans, respectively. A better version of this test might use a platform and smaller weights, and perhaps find that the load limit of the square is .6 soda cans, and the triangle 1.8 - thereby making the triangular structure a whole THREE times stronger than the square structure.

As I said, I can tell you were not taking this all that serious, and it was merely a demonstration of strength, but it would be interesting to see how strong of a structural difference you could demonstrate along with some more accurate information!!

Keep it up guys, I love your work!
#5 John Galletta on 2013-02-21 18:21 (Reply)
Another domain for experiment: the diagonals can be placed in 2**6 ways. (I haven't worked out how many are effectively distinct.) I would guess that the whole is a bit stronger if the diagonals form a tetrahedron.
#6 Tamfang (Homepage) on 2013-02-21 18:45 (Reply)
You needed at least one more strut on the inside from a top corner to the opposite bottom corner.
#7 Rafi Schutzer (Homepage) on 2013-02-21 19:04 (Reply)
The first wire frame cube failed because, without triangular bracing, it was effectively a mechanism with somewhat stiff joints. You can add struts to the basic cube all you want, but the only effective ones will be the diagonals as in cube two. The triangulated cube failed by Euler compression strut instability in the upright members, clearly seen just at the end of the video. The best way to prevent that is to increase the moment of inertia of the uprights. (or shorten the distance between end points by breaking the big triangles into smaller ones).
#8 Michael Piersdorff on 2013-02-21 20:31 (Reply)
Wouldn't help, Rafi. See my post below.
#9 Michael Piersdorff on 2013-02-21 20:34 (Reply)
When I wrote the opposite corner, I meant that it should be diagonally opposite internally. In fact the more internally diagonally opposite struts the better. All four intersecting in the center would be nice.

http://en.wikipedia.org/wiki/Structural_engineering_theory#The_Euler-Bernoulli_beam_equation
#10 Rafi Schutzer (Homepage) on 2013-02-21 21:01 (Reply)
how did u make these product..?
#11 blackbeard saini on 2013-02-22 11:32 (Reply)
Structural Can Support Experiment #101

Results:
a. The weaker design can hold no cans.
b. The stronger design can hold 1 can, but it cannot hold 2 cans.

Experimenters' Conclusion:
The stronger design is twice as strong.

Reader Observation:
WTF! Does that mean if the stronger design cannot hold 4 cans then it would make it quadruply as strong, or if it cannot hold 1000 cans then you can use them as scaffolding at a construction site?

Message to the kiddies:
Don't listen to these silly illogical people. You and I know that you would have to compare the maximum that each can can hold before you could work out relative strength. So don't go around saying it is "twice as strong" or the other children in the playground will make fun of you.

PS "Twice as strong for only 15 cents more".
"More that what? "15 cents" without a base comparison is a useless figure on its own. If it cost 5 cents without the additional "lines" (I wish), then you would have to go back to the design drawing board.
#12 Mary on 2013-02-23 02:03 (Reply)
I thought the same things Mary. But I didn't have heart to write it down. The reason these people say such idiotic things is because they are SALESPEOPLE. The people that actually create new things have more on the ball than the fast talking bullsh*t artists above.
#13 Rafi Schutzer (Homepage) on 2013-02-28 15:26 (Reply)
Just for fun, see the structural simulation of one of the 3D printed model performed in Rhino using Scan&Solve for meshes plugin. Watch the short video at
http://youtu.be/xPaCIaXj68M

We will post simulation of the second model when we get to it. Enjoy!
#14 Vadim (Homepage) on 2013-03-01 00:46 (Reply)
Just for fun, see the structural simulation of one of the 3D printed model performed in Rhino using Scan&Solve for meshes plugin. Watch the short video at
http://youtu.be/xPaCIaXj68M

We will post simulation of the second model when we get to it. Enjoy!
#15 Vadim (Homepage) on 2013-03-01 00:47 (Reply)

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