- [Jared] The inside of this household fan
has some neat mechanisms
especially the gears and levers
that cause it to oscillate back and forth.
Let's take a closer look.
My name is Jared
and I make 3D animations (metal thudding)
on how things work.
After this video, make sure to visit my YouTube channel
to see more animations.
First, a quick tour of the features of this fan.
At the bottom are the buttons to set the fan speed,
a dial to adjust the pitch of the fan,
and then the pin on top to make the fan move back and forth.
You know the drill by now.
Your fan might be slightly different
but the mechanisms I'm about to show you
are probably very similar,
unless it's a box fan or one of those tower fans
or a bladeless fan.
These are pretty cool.
I might have to do a future video on this.
But for now, let's focus on this fan over here.
Taking one apart is pretty simple.
Several screws in the bottom and plastic pieces to take off.
The coolest parts are at the top.
So sit back and relax and we'll let the 3D animation
do all the hard work.
Okay, let's start at the bottom
and go through this in detail now.
Four buttons, three speeds,
and then the white one turns off the fan.
Each time you press down a button,
the previous ones are released.
The white button turns the fan off.
It also doesn't stay down like the other buttons do.
And if you've been following my YouTube channel,
you know that I like to explore different mechanisms.
And there is definitely a mechanism here.
Let's take a look.
Each button has a spring underneath
that wants to push the button back up.
Inside is a metal plate
with a few jagged cuts going down.
This metal plate is being pushed to the right
by this spring.
By pushing down a button, the plate slides to the left.
Push down far enough and it clicks into place
preventing the button from coming back up.
Press down another button and the plate slides enough
to release the first button.
The sole reason for the white button
is to release any of the other buttons.
You'll notice that there's no notch to hold
the white button down.
Releasing the other buttons will then turn off the fan.
Coming out the back here is three color-coded wires.
Whichever button is pressed will send a signal
up the wire to the top of the fan
and into the motor to start the fan spinning
at whatever speed we choose.
At first, the fan will only be pointed
in one direction.
If we wanna cool off more of the room,
then press the pin and the fan starts oscillating,
or, in other words, moving back and forth.
We already have and electric motor
and you don't wanna add another one.
The idea here is to convert the spinning motion
of the fan into a side-to-side motion.
Let's take a step back so we can understand
the concepts behind this.
This is called a four-bar mechanism.
Each bar is connected by pins
which allow them to rotate freely.
One of the bars is usually fixed in place
so that it can't move.
This one is called the crank.
Usually a motor is causing it to rotate around.
These other two bars are forced to follow the motion.
By changing the lengths of these bars,
we can get some different motions.
Let's focus in on this configuration.
Normally the green bar is the one that's fixed in place.
Watch what happens when instead the small blue bar
is fixed in place.
Now watch the motion of the green bar.
Notice how it goes back and forth about the same amount.
And this is how we get that oscillating motion
for the fan.
Now let's go back and see how all this works on a fan.
So the four bars on a fan are right here.
This is the short bar that's fixed in place.
There's a long bar here.
And another long bar, which in this case is the motor.
And then the last bar which is the crank.
This is the one that has to rotate to get the fan
to start oscillating.
But there's still a missing piece.
How do you convert the rotation of the fan
to the rotation of the crank?
The magic happens inside of the gear box.
Before we take a look at the gear box,
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All right, let's see what's inside
of that gear box.
There's a piece that sticks out the back
that rotates along with the fan.
This is called the worm.
When it spins, it kind of looks like it's moving
even though it's not.
Right next to it is the worm gear.
Down below is another gear which is directly attached
to the crank.
The pin is what connects all of these gears together.
You can see it has some gear teeth on it.
Towards the top of the pin,
there's a spring with two ball bearings.
They come out just far enough to catch the worm gear
and spin with it.
Let's walk through the whole thing now.
The fan is on which spins the worm and the worm gear.
This spins the pin.
Which spins the next gear,
which turns the crank causing the four-bar mechanism
to oscillate the fan back and forth.
This only works when the pin is down.
When the pin is up, it doesn't rotate
along with the worm gear
so nothing else below it will move.
This means the fan will continue to point
in the same direction.
But if we press the pin down,
the fan starts to oscillate again.
Let's look at the ball bearings again.
When the pin gets pulled up,
the ball bearings would go flying in each direction
if there was nothing to stop them.
This actually happened to me the first time
I took apart the fan.
Don't worry, I found them again.
Just be warned if you try this yourself.
What normally prevents this is the gear box lid.
Pull the pin up and you can see the ball bearings
are forced back in.
This is what keeps the pin up.
Otherwise it would just fall back down.
Press the pin down again and the spring
forces the ball bearings out and in contact
with the worm gear.
I also wanna point out that the speed of the crank
is much slower than the speed of the fan.
If it was spinning as fast as the fan,
well, it probably would break before that point.
The right combination of gears
helps to slow the speed down so the oscillation happens
at just the right speed.