Strong Structures with Triangles | Design Squad


As I walk around a city,
I tend to notice the shapes of things. Check out that elevator shaft
up there. Triangles that are stiffening
the structure around it. That walkway down there has
triangles all over it, as does the dock right
underneath, actually. And, of course, huge triangles
made out of rope in tension, supporting the masts
of that tall ship. Why do all these structures
use triangles? It’s because triangles support, stabilize, and stiffen the structures. Support, stabilize, stiffen. Hey, cool, three “S”s. We could make a triangle
out of that. Triangles are really powerful. To demonstrate how powerful
triangles are, I’m going to use a really
classic project. Toothpicks and some gummy worms
to join them. To build a structure that’s
hopefully strong enough to hold up… …this brick. I’m going to use scissors to
chop the gummy worms into little gummy connectors. So I have now
a very nice little cube. I’m going to let it go in
three… two, one… (thuds) One of the big challenges we’re
running into with this particular design is
that it’s all built out of parallelograms. A parallelogram is a shape with
opposite sides that are parallel and equal in length. You can see, when you stick the
brick on top of this structure, the connectors
aren’t that strong. So, instead of staying up,
the whole thing just flattens. (thud echoes) Instead, let’s try building a
structure based on a triangle. As I apply force to the
triangle, you can see that
it has a lot of stiffness. No flattening this shape. Four triangles all stuck
together. But the fancy name for this
shape is a tetrahedron. So, I’m just going to keep
adding triangles until I have enough structure
to support the brick. Nice. Those triangles are not
flattening like the parallelogram. The triangles are braced against
each other for stability. It’s a nice, strong structure
that supports the brick. Even though the little
connectors we used aren’t that strong
all by themselves. What a great shape. You know, when I think about it,
I use triangles all the time when I build stuff. The next material I’m going
to work with is some aluminum cans. The cans are strong
in compression, which means they can hold weight
when they’re pushed on the top and the bottom. To show how strong they can be,
I’m going to stand on one. And you can see how much load
was on it, because all we had to do was tap
the side, and it didn’t have the stability to resist that tiny, tiny
side force, and the whole thing went
(mimics crunching). (crunches) Crushed. I’m going to build myself
a stool out of recycled cans, some duct tape, and paint sticks. Here’s leg number one. Times two! Times three! Times four! These are going to be
the four legs of my stool. Time for some paint sticks. I know this isn’t going to work
out so great, because what shape is it? A parallelogram. And this parallelogram,
without additional stability, will flatten, like this. So, I’m going to add some
triangles to stabilize it. Check it out. A triangle here. And another triangle here. Let’s see if this thing still
acts like a parallelogram or not. No, it’s actually a lot stiffer. Now I guess all I need is
something to sit on top of. It’s still wiggling
a little bit. If I add more triangles,
the stiffness of the structure should increase a bit. Yeah, that’s actually a lot
more stable. These triangles
in this structure give me those three “S”s– stability, stiffness,
and support. The stiffness and the stability
increased thanks to adding more triangles. So now the stool can
support me. Any time I’m looking to support,
stabilize, or stiffen something I’m making, I’m going to add a triangle.

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