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World’s Smallest Nerf Gun Shoots an Ant
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This is the world's largest Nerf gun.
This is a normal Nerf gun.
And for the past year,
I've been making good use of my time
by working on this
the world's smallest Nerf gun
where you can actually cock
it back and fire a dart.
And while this is now
the current world's smallest Nerf gun,
our goal for today
is to break that record
not once, not twice, but three times,
shrinking it by a factor of ten
each time we move down.
And if I'm math’s correct,
that means by the time we get here,
you'll be able to fit
five of them
across the width of a single human hair.
But before we can start breaking
all these records,
we need to talk about
the first major problem we encountered
just to get here.
And it relates to the fundamental
way a Nerf gun works.
Because when you pull the gray
cocking mechanism back, it brings
this spring loaded piston with it
all the way back until it hooks in
with this catch mechanism.
Now we're loaded and ready to fire.
So now when you pull the spring loaded
trigger back, it
forces the catch
mechanism back down,
releasing the piston plunger,
which quickly springs forward,
forcing all the air in the chamber out.
And since the lightweight foam
dart just happens to be in the way,
it goes along for the ride,
and if you actually take one apart,
you'll find
it's made from 87 parts,
13 springs and six hinges.
And so the first problem you face,
if you're trying to shrink
that down to human hair scale, is
it would be impossible
to assemble
those tiny mechanical springs and hinges,
which left us with
the incredible challenge
of trying to make our entire tiny,
functional Nerf
gun out of only one
single part with no springs.
And as it turns out,
there's only one place in the world
that leads the research
in creating really tiny,
bendable machines from a single part.
And it also just happens to be
where I got my undergrad degree
in mechanical engineering.
Which meant it was time for me
to head back to my alma mater, BYU,
to visit some old friends,
starting
with one of my favorite professors...
Dr. Howell
Good to see you, Dr. Howell
I'm trying to remember
what grade I got in your class.
I looked it up this morning.
I'm guessing an A-
man, that's ri-
Well, if I disclose that, that's a uh
a violation of federal privacy
For what it's worth,
he teaches much better than he
poker faces.
And who would have known that
this bright, energetic student
sitting in the class
was going to become
one of the most famous
engineers in the world?
Not me.
I'll tell you that much
not me
And I say that with confidence
because he was also able
to locate my student ID
and the only thing
more aggressive than those eyebrows
was the decision to rock the double
puka shell necklace for picture day.
Our first stop
was to finally meet in person
with the group of BYU students,
I'd been working pretty closely
with on this project for about a year.
So today was all about a final
meet up to see if this was a mission
accomplished situation for us
and Jacob, who led the student team,
summarized the second major issue
we faced here.
The physics of scaling down is huge here
friction and surface forces
are multiplied exponentially.
Besides the difficulty of assembly
I mentioned before,
this was the second reason
we needed it to be made out of one part
to eliminate the exponential friction
forces between moving
parts at tiny scales.
Our plan was to come up
with a template design
that was full size,
and if that worked,
we would just keep scaling
that exact shape down.
But what should that look like?
For example,
how do you even store energy to fire
a dart with no mechanical springs?
Well, here was the first prototype,
and while it's still more than one part,
you can see the clever way
the springs were replaced
with the few new parts
and stored energy
by being flexible in engineering,
we call that a compliant mechanism,
and I happen to know
the world's
foremost expert in that field.
This is the book
on compliant mechanisms.
well I think so,
but I may be biased,
and he's as humble as he is biased
because this is hands down
the number one cited book in this field.
A regular method
is going to have rigid links
and then something like hinges
are going to make it move
something like this.
And this is a very common
type of mechanism
called a 4-Bar linkage.
And Dr.
Howell explain how you can make that
out of only one part.
We get our motion
from something that bends and flexes
And this is a great demo
because if you overlay them
on top of each other,
you can see
the resulting motion is totally identical
and that is compliant, cause it’s flexible
and that is a compliant mechanism.
And as Dr. Howell
went on to explain, the compliant
mechanism version offers six advantages.
Number one,
it's fewer parts, in this case
eight versus one.
Number two, lower cost.
There's no labor for assembly
and the whole thing can be made
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