We're building a hoverboard from Back to the Future that actually hovers
This episode of Make It Real is sponsored by Monster Legends the
very first game to feature the Hacksmith as a character
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Here at Hacksmith Industries we just finished building our very own self-lacing shoes from
Back to the Future so naturally the next step is building a hoverboard to go with them
Hoverboard?
When I first saw Back to the Future 2 when I was just a kid
I wanted a hoverboard, everyone wanted a hoverboard
35 years after the movie came out and we still don't even have anything close
For god's sake when Marty travels from 1985 to the future he goes to 2015
That makes us five years behind
On Wednesday, October 21st 2015
2015? You mean we're in the future
Well I suppose the movie got a few things wrong,
but where are we when it currently comes to hoverboards?
There are basically three technologies that get us kind of close
First up is air powered, the problem with this method is that it's essentially using jet power
which basically means you're flying not really hovering
Another popular method is using superconducting magnets
While promising, in order for this to work you have to keep the magnets freezing cold at all
times and ride on a specially engineered track and that presents an entirely new set of obstacles
Finally we have eddy currents, here we're still using magnets but
instead of freezing them they're spinning at high speeds to generate eddy currents
We're pretty good at making things spin really fast
Here at Hacksmith industries we take on co-ops from a variety of tech backgrounds and experiences
This is Jimmy, Jimmy studies mechanical engineering at the university of Waterloo
and he also leads Waterloop
A student design team developing hyperloop technologies based on Elon Musk's ideas
Some of those principles should actually translate pretty well, I think we're going to hire him
He'll be here with us for the next four months and in that time he needs to build me a hoverboard
Eddy current that's what I know, that's what I do best
First of all: What is a magnet and how do they work?
All magnets have north and south poles
These are pretty useful if you want to stick things together
The same poles repel each other
What does this look like?
Looks like hovering to me so I know what you're thinking
Why don't we just take a bunch of heavy duty magnets, stick them to the bottom of the board
and repel off a magnetic floor of the same pole?
Well just ask Earnshaw
He has a theorem that states a collection of point charges cannot be maintained in a stable
stationary equilibrium configuration solely by the electrostatic interaction of the charges
No one understands what you just said you gotta slow it down man
Uh okay- cut!
Here we have two magnets of the same pole facing each other,
the only way we can make this magnet hover is if we constrain its degree of freedom
You'll see I have this other magnet on this rod and if I let it drop down it hovers
Now let's see what will happen if I remove the rod entirely
It didn't work very well without the rod,
if we made the hoverboard like this it'd only be able to hover in one spot and that's no fun
In other words you just can't make another magnet hover against another just won't work
But- this is where eddy currents come into play
When you expose an electrical conductor (copper or aluminum)
to a moving magnetic field you create an electrical current within the metal
This is called eddy currents
I have this inductor it's connected to this multimeter here and
well right now it says zero volts duh because there's no power connected to it
If I rub this magnet across the inductor we get a voltage reading
How is this possible?
Because of science b****
Now due to Lenz's law, the changing electrical current actually creates a magnetic field
I guess in a simple term this kind of acts like a magnet, now if we use the same principle that
the same poles repel each other, we can actually apply this to our hoverboard
And in this case we don't break Earnshaw's theorem, but how are we gonna do that?
We need a lot stronger magnets
There are two ways to maximize the strength of a magnet, first a colder magnet is a stronger magnet
Yes we do live in Canada but keeping a magnet cold comes with its own set of infinite difficulties
The other way is to take advantage of what's called a hall back array
A good example of this is fridge magnets use one side of it and it doesn't stick
Flip it over-
Apparently our big fridge is made out of aluminum that means magnets don't stick to it
Luckily our small fridge here is made out of steel so as I was saying
you flip this over and it sticks
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What crazy monsters can you guys make with me?
That also sounds weird
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These magnets need to be fixed to our board and the easiest way to make them move at a high speed
is to create spinning wheels that are connected to the bottom of our board
In this case we'll be using these arc magnets
specifically designed for hull back arrays from K&J Magnetics
But how many magnets do we need?
How strong are they?
And how fast do we have to spin them?
We could spend all day trying to calculate the theoretical forces they could make, but that's
really hard there's so many different factors that affect it and modeling it is really hard
Trust me I've tried
Let's just build one to test
This is our prototype wheel and here we're going to test out how much force they actually make
and how much power we need to keep them spinning at high speeds
On this test rig we have this load cell, this load cell will record how much force is being applied
Also on our motor we have applied a watt meter and a tachometer to record
how much power the wheel is consuming and also at what speeds
So our tests have shown that we can do 44 pounds of force at around 5,500 rpm
James weighs about 165 pounds so that means we'll need four magnet wheels to make him hover
But we want him higher off the ground than just level,
so we're going to use eight magnet wheels to get approximately an inch off the ground
I guess I need to design a board that will fit eight of these things
Obviously we need to make this board look like the hoverboard from the movie
Hoverboard?
It's such a 1980s imagining of the future, the pink, the diagonal lines, I love it
I found a one-to-one 3d model to work with
Let's transpose the wheels onto the board and see how much space we need
Then we can scale the model up until everything fits inside
Unlike a conventional skateboard that bends when you stand on it we can't have that with our board
so, instead we're gonna make this board out of aluminum, it's light and strong but
more importantly it's non-magnetic
Let's Make It Real
Now, the last step is the balance of wheels
If we don't balance them this is how they're going to perform
We've sent out our wheels to FanTactics they specialize in
dynamic balancing of rotating assemblies
Balancing our wheels will ensure they don't explode
and they can safely operate at super high speeds
Wheels are ready, board is ready
In part two of the hoverboard series we're gonna be wrapping board and beautiful pink 80s glory
I'm going to assemble it, I'm going to make up with my mom and James is going to hover-
Jimmy what happened?
Well this is what happened...
it's not on fire
It's not on fire
It's on fire
Okay...
Sometimes things don't exactly go to plan, you're not gonna want to miss
part two of our hoverboard series, things go a little off the rails
And remember to download Monster Legends to get the Hacksmith monster,
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That's heavy