Why You’ll Fail the Milk Crate Challenge

[light synth music]

[Narrator] This is the Milk Crate Challenge.

The goal, to make it from one side

of the pyramid to the other.

[milk crates clattering]

This is gone, this is gone.

So the problem here isn't

that it's a staircase or a pyramid,

but that these are essentially individual columns of crates

stacked on top of each other.

And they're not just any columns.

They are totally unsupported columns.

My name is Dr. Nehemiah Mabry.

I'm a professional engineer, and I'm an educator.

Columns are vertical, slender members.

We design them against a failure known as buckling.

And basically, it's a sudden horizontal movement.

You can think of maybe a soda can.

If you step on a soda can,

a lot of times it collapses on itself.

A ruler.

Press on the ends of the ruler, you'll get a bend sideways.

And it happens whenever the force exceeds

what we call the critical load.

Critical load is the maximum amount of weight or load

that a column can take before it becomes unstable.

The skinnier and the taller a column is,

the less of a critical load is needed

for it to get unstable.

As you're walking up this crate challenge,

you are literally getting to a point to where

what it takes for that column to fail becomes less and less.

You know up is easy.

Going down is going to be the [beep] problem.

[Narrator] So why is it here, at the top of the pyramid,

where most people tend to fall off?

Side sway.

See, there it is.

When you put it down...

If you imagine that this is a column,

there are different ways that a column can be fixed, right?

It can be embedded in the ground,

which we call fixed.

It can't move sideways, nor can it rotate,

because it's embedded in the ground.

And if we had that same type of connection up here,

this is your most stable column, right?

It's called fixed fixed.

The most unstable column is when you have something

fixed or pinned here,

and literally there's no support up here.

So that means that whatever load comes up here

is basically gonna have to support itself.

And if this doesn't have the stability that it needs,

then you're going to get the buckling very easily.

Going up, you know, you're basically,

you can rest your weight, right?

But when you're stepping down,

you actually have to control the placement of your weight

a little bit more than you had to going up.

And when it comes to column,

the placement of your weight really, really matters.

Ideally, in a perfect case scenario,

a person would be able to set their weight

right down the center of that crate.

And it literally has what we call pure compression,

so that's all that its experiencing.

But really,

if you happen to put your weight off to the side,

now you're creating like a rotational moment.

Well, the problem is that because these are separate crates,

it's not like there's a continuation

of the member of the column to actually push off of.

You're really depending on your own muscle control

to try to get it back stable,

which is extremely tough.

So there are a couple of ways

that if I just had to build this

and make it structurally sound,

I would find a way to attach each crate

to each other with adhesive,

or something to make it act as one unified column.

Another thing I would do is create lateral support.

I would probably have several crates,

so that when one begins to sway,

it can distribute the load to the other.

I have just been able to explain to you

exactly why these things fail,

but it's a totally different thing from understanding it

and actually getting out there and doing it.

It doesn't always translate.

So even though I can very, very clearly

explain to you what's going on here,

you're still not gonna catch me doing this crate challenge.

And that should tell you something.