Auto news on Youtube Jan 23 2018

You've seen triple kickflips before.

You've probably even seen quads.

But what about five, six, seven, eight flips on flat?

What is the maximum?

What is the best of a human being could do as far as flips and spins on flat?

Let's take a look.

Welcome back to rad rat video, a channel where you can learn something new about skateboarding

three times a week.

Every monday wednesday and friday we take a look at something in the skateboarding world.

We have biographies of your favorite pros, we talk about skateboarding video games, we

learn tricks on the shred school, and sometimes we learn a little bit about physics which

is what we're doing today.

So i got a question from seany who really wanted to know: what is the maximum amount

of flips you could do i'm flat?

And i was thinking, you know what, this is gonna be really easy.

All i got to do is figure out how high you can jump, how much airtime that is, and then

how hard you can kick and just work some numbers.

It'll be no big deal.

Ended up being a little bit harder than that, but i did come up with a solid answer.

So the first thing i wanted to do is figure out how much airtime you can get, and i want

to look up the world record ollie.

And so this is the current record as far as i know.

This is aldrin garcia breaking the record a few years ago, and i watched the footage

really closely looking at the waveforms for where the tail pops and everything, and i

got a number of about 0.7 seconds.

That's the amount of time that he's in the air, and so i started to run with that for

a while but i realized that that's not quite right.

Because, yeah, he jumps really really high, but right when he clears it he just pushes

his feet down.

That would be like if you're catching the board, you know, and if you've ever done a

triple flip or something where you really have to wait the board out to the last possible

second, you know that you can squeeze out a little bit more time if you just suck your

feet up and land with your knees bent.

So we're talking about air time, not necessarily height.

And i recorded myself just jumping in my bedroom and landing on my feet and i got that same

amount of time.

I didn't get as high, but i was able to delay landing a little bit, so at point seven

really isn't gonna be the maximum amount.

So i decided to look into basketball.

I found this video where there's a pro basketball player, and they have him hooked up to all

this stuff and he's able to get point eight four seconds in the air when he dunks.

Well they looked at michael jordan too.

The longest he was ever in the air was 0.92 seconds.

There's apparently this hard rule where it's impossible to jump be in the air for a second

or more and land on your feet.

It'll always be less than a second.

Unless you're talking about like an olympics high jump.

Well that's a different technique, because you jump over the bar and you land backwards,

you're not landing back on your feet.

So it's not gonna be more than a second.

That seems to be impossible.

But i also didn't want to use that number of 0.92, because it's a different technique.

He runs all the way across, and he was able to build up that momentum and jump.

Apparently you can jump higher with a running start, because you can use your regular jumping

muscles, but you can also convert some of that forward momentum into upward momentum

with different muscles.

So you're not gonna get quite the same amount standing on a skateboard and jumping straight.

So the number i decided to go with was 0.85 seconds, which seemed to be pretty fair.

That's a lot.

That's gonna be really really high, but it is technically possible, and that's all that

really matters at this point.

So that is the amount of time that you'll be in the air, but not the amount of time

that the board can flip, because there is a bit of a delay between the pop and sliding

your foot up and then flicking.

So i looked at some footage of me doing double kick flips and i found that it took about

point zero five seconds to go from popping to flicking.

And so, that would make our actual number of the amount of time that the board is flipping

is 0.8 seconds.

So we've got the amount of time that the board is flipping.

The next thing we need is the power of a human kick, because the idea is that we'll take

the force from the kick put it into the board and see how quickly it flips and go from there.

And this ended up being pretty difficult to figure out, because the first thing i was

trying to do was think about, 'okay well what's the maximum amount of human kick power

that you can ever get?' and i started to look at numbers from soccer players, football

players, fighters all kinds of stuff and i was getting numbers all over the board.

But if you take like a football kick off, that would get you like 50 flips.

It was ridiculous.

But the problem is that you couldn't possibly do that on a skateboard, because it was standing

on the board.

You have, like, this much room to get your foot going before the flick.

You don't run and kick it as hard as you possibly can, you know, and you wind up and all that

kind of stuff.

So that's not possible to do.

You could get 50 flips, i think, if you were to hold your board out and then a professional

football player runs up and kicks it as hard as possible.

You might be able to get 50 flips, but that's not going to make sense from an ollie.

And unfortunately, there's no numbers out there for how hard someone can flick their

foot, and so i had to go mythbusters-style and record myself doing it, and i had like

a ruler and stuff on the ground to try to figure out some numbers on how it works.

And the idea was to take this into a calculus formula that would help figure out the amount

of momentum that my leg is building, and it got really complicated.

So here's how i thought that it would work.

In a physics, there's something called a moment of inertia.

It's not a moment of time, it's basically like a customized formula to figure out how

much force is in something that's turning.

So with your leg, for example, your thigh is a thickest part of your leg but it's moving

less than the rest because it's only kind of pivoting while your foot's swinging around.

So you have to have a formula for how much this mass is affecting the force, and how

much your foot is and all that kind of stuff.

You can think about it like a ball on a chain.

If you were to swing a ball on the end of a chain, it has a lot more force than if you

were to hold the ball and swing the chain, right?

The same item, but where is it, you know, rotating around and everything.

So my first thought was, my leg is basically a cone.

So the thigh's the thickest, your ankles the thinnest.

So it kind of comes down into a cone, and then your foot could be like a second cone

on top of that.

So my plan was to calculate a swinging cone and then add on your swinging flicking foot,

and get some force that way.

But that really didn't work out at all either.

The numbers i got from that didn't make sense, and it's kind of obvious why.

You look at someone do a kickflip.

You don't swing your whole foot like this.

It doesn't make any sense.

You can't do that.

So what i did was, i jumped up and i did kickflip motions as hard as i could on video to try

to get some numbers that with no board i was able to just kick as hard as i possibly could,

not worrying about technique and try to figure it out from there.

And when i watched that footage back, i realized that my knee is not actually moving at all.

And so, if you think about that, you can consider just the bottom part of your leg and your

foot to be the only thing that's affecting the flip.

Your leg has to get up and move into position, but it's not really contributing to the effect

of the flip.

So next thing we have to do is figure out how to model your leg in physics.

So you could be a cone, you could be a cylinder, you could pick things that have formulas pre-made.

The best thing to do would be to actually make your custom moment of inertia based on

the mass of your leg and kind of stuff.

That's extremely complicated, and honestly i don't know how to do it.

So what i went with was a regular cylinder.

The reason for that is because, although your calf is thicker than your ankle, your foot

is moving.

And so, being smaller and lighter, it still has more of an effect.

And so i figured that would kind of work out to be a cylinder.

It's not 100% perfect but it will get us pretty close.

And we're looking at single flips here.

If it's if it's gonna be like 4.2 versus 4.3, it doesn't really matter.

We're looking for a whole number here.

So i think that that's gonna get us pretty close.

So here's the formula to figure out the moment of inertia of a cylinder.

It's one-third ml squared.

Which means we need the mass and the length to figure out where we're going with this.

So how do you get the mass of your leg?

I can't exactly put my leg on a scale because it's connected to my body, so what do you

do well?

What i decided to do was look up stats from michael jordan.

If he's the guy who's able to jump high enough to get the numbers we need, then let's just

use his body type as the person doing the tricks anyway.

So his total weight when he was playing was like 216 pounds, which is i think 91 kilograms

and i found this chart and this shows what percentage of the body is made up of different

body parts.

Your entire leg is 17.5%, but your thigh is 11% so your lower leg and foot are five point

eight five kilograms.

Slap a shoe on there, and we can up to six kilograms.

So that's good, but what about the length?

Well they don't keep stats for that.

You have stats in the nba about everything, but you don't have like inseam or anything

like that.

So i had to do a little bit of guesswork.

The length from my knee to my toe is 27 inches, but we're talking about a basketball player.

Michael jordan's hitting six six so i decide to round that up to 32 inches which is 0.8

meters.

So we can go ahead and plug that into our formula now.

That gives us one point two eight kilogram meters squared.

That doesn't do much for us right now, but we're gonna put that aside.

We'll need that number later.

The next thing we need is the angular velocity, in other words, how quickly your leg is rotating.

So what i decided to do is, i took that footage of me kicking as hard as i could and i ran

some numbers about the difference in angle over the course of a few frames.

It goes from 74 degrees to 137 degrees within three frames, which is about a tenth of a

second.

That is 630 degrees per second.

Of course, using degrees is too simple.

You have to convert it to radians, which is 11 radians.

Okay, so now we got that, we can plug that in and we can figure out how much energy is

coming out of this kick.

So here's the formula for that.

This is the moment of inertia, which we calculated as 1.28, and then the angular velocity right

here which is 11, and that works out to be 77 joules as the amount of energy being kicked

out.

And i'm not a professional athlete.

I'm not gonna be the strongest kick in the world, but we're using my speed and applying

into a bigger body with a longer leg, so the number is already a lot higher than what my

kick would actually be.

If i could, you know, put a rocky 4 punching bag with a read out on it and kick it and

see how much it is, that's already quite a bit higher than me.

But we're gonna round it up to 80 just to be safe.

To be more of professional athlete level.

So we're gonna run with a number of 80 for the actual kick, but how much does a board

receive?

Because you kicked the board and your leg doesn't stop dead.

You follow through.

Also, you have to… you're not just flipping straight down, you're flipping at an angle

to level the board back out.

Some of that energy is not going into a flip.

I had to do a little guesswork on this.

There's no numbers about how much force is lost on a kickflip, but i figure maybe 20%

is lost from the follow-through and all that kind of stuff.

So that leaves us .8 of 80 or 64 joules for the amount of energy that's going into the

board for flipping.

Ok, so now we do the exact same stuff we did before with your leg, but backwards with some

new numbers.

And let's get into that.

So the total amount of energy: sixty-four joules.

What about the moment of inertia?

This ends up being a little bit complicated, because i need to figure out what kind of

board is gonna be used here, and how to measure it.

Like, what kind of physical shape we could use for our calculations and stuff like that.

And so my board right here is… and is..

Uh it's got freestyle wheels on it, first of all.

And it is eight inches wide, which is a little bit wide for this.

I was gonna go a 7.75, and i decided to run some numbers.

I was thinking, 'so we have to figure out what shape is closest to.' and i was thinking,

maybe a cylinder.

Because if you think about it, most of the weight is like right here, you know like in

the in the metal.

And then there's a little bit more on the outside.

You get to the wheels and the board.

So if you consider it a cylinder rotating around its center like this, then this is

the formula for that.

You need the mass and the radius for it.

So this board is 2.3 kilograms, but it's not the lightest in the world.

Like i said, it's got those big wheels.

The deck's a little bit bigger than it would have been.

So i rounded that down to two kilograms for our board that we're gonna be using.

And then we need the radius.

So here's the thing.

You might think 7.75, but that's not exactly true.

If you look at the board, the widest it is, is from this corner of the deck to this corner

of the wheel.

It's kind of like a hypotenuse between the width of the deck and the height of the trucks.

And you know, what this is why people use lower trucks and smaller wheels.

At least back in the 90s.

Because the lower your trucks and wheels are, the closer the width is to the width of the

board.

You know, because if it's, you know, the taller the truck is the bigger this angle is.

So kind of makes sense why people would do that.

But i've talked about this before.

I don't think that that's really the way to go, because you're not trying to do the most

flips you possibly can in one ollie most of the time.

You're trying to do a nice kickflip, catch it, and land it cleanly.

You need more space.

You need wheels that can actually roll.

All that kind of stuff.

You need to worry about how much pop you can get.

If you have really low trucks, then that's not really gonna help.

You know, imagine the ideal version.

The board with a less, the smallest, amount of distance would be a deck sitting in the

carpet, you know.

That would flip a lot easier than anything else, but you're not getting any pop.

Try to do a quadruple kickflip with just a deck in the carpet.

You're not gonna get very far.

So i wanted to use a more reasonable setup that would kind of match what we're going

with.

So the angle that i figured out with.

So if the board's like 7.75, and the trucks are average height, the longest distance,

the radius of the cylinder here is about 8.25.

So we plug that into our formula right here, and we get a moment of inertia of 0.05.

And that is so much less than your leg.

It's spinning around its easiest axis.

It would be harder to do like, backflips and stuff.

It's spinning around itself really easily.

It weighs a lot less than you and all i can stuff.

So the number's gonna be a lot more than what your leg was able to do.

But now we've got everything we need.

We can plug it in and solve for the angular velocity, and what we end up with is 2900

degrees per second, which is pretty crazy.

I think i was like fifty point six radians or whatever, but 2900 degrees per second.

It just sounds like a lot, but what does that actually mean?

Well that is just a hair over eight flips per second.

But we're not getting a full second.

With our usable air time of 0.8 seconds, that's actually six point four flips, and that's

the maximum.

There's no way you're gonna get to that seventh.

You're gonna do six and then just barely catch it a split second before you land.

So is it really truly possible to do a hexuple kickflip on flat?

Well i just had to do a little sanity check, and take a look at some actual footage.

So this is ellis frost doing a quad kickflip on flat.

I went through it frame by frame.

It took him 18 frames to do four flips.

So if you have that flipping speed, and you stretch it out over our total air time of

0.8 you do get right around five-and-a-half flips.

So with his exact technique and his exact body size and all that kind of stuff, he could

theoretically do five and a half flips if he could jump as high as michael jordan.

And if you add in a bigger, like, basketball type of figure.

A little bit stronger guy to kick it a little bit harder, you could see it getting to six

without too much difficulty.

So it does really seem like it makes sense.

But does that mean we're ever gonna see someone at the skate park doing a hexuple kickflip?

You think about a triple flip, it's like, for most people, about as hard as you can

go, and you can do a double?

That seems pretty crazy, and i don't know if we're ever gonna see it.

At least on a normal sized board.

Because the kind of person who's capable of doing that from a physical, perspective like

a michael jordan body type: six foot six, 216 pounds, is not gonna be the kind of guy

who's really into tech skating.

Most of the time, when taller guys and bigger guys get into skateboarding they tend to do

more gap stuff.

Like he'll get on to a really big rail and holding it out.

You don't see those guys doing really technical flip tricks and stuff, because of the balance.

The taller you get, the more like top-heavy you are to a degree.

You know, if you sit down on your board you can drop in you'll never slip out.

But if you're standing up, you can.

If you stand up taller and taller and taller, it gets harder to stay on the board.

So i don't know if anyone who is capable of jumping as high as michael jordan and all

that kind of stuff are gonna be the guys trying as many flips as possible on flat.

But it is possible that it could happen.

So the second part of the question was about spins like pop shove-its and stuff?

And i found that that was a lot harder to work with, because there's no point where

your foot hits the board.

It's always in contact with it and it just builds momentum in your scoop and you throw

it.

And it's really hard to figure out exactly how much force you can generate for that.

So i decided to do just this last part with the shove it, and i found this footage of

shane o'neill doing a 720 show it on flat.

And he's landing pretty much straight on it, so i figured, you know, he's doing 720 degrees

in within how many seconds?

Let's stretch that out to our world record jump.

And so, each spin of his takes point one five seconds.

You stretch that out to 0.8 seconds, then that would be like nine hundred and sixty

degrees.

So it would be possible to do a nine hundred shove it on flat.

But he doesn't necessarily have the best technique.

A much quicker technique for shove-its is the freestyle way, where you have your front

foot on the nose and you're twisting your ankle while throwing your back foot around

at the same time.

And so here is some footage by ikkei toki who's ten years old.

He's also doing a 720 shove it on flat with a regular size board, and he does it the exact

same speed as shane o'neill.

He doesn't jump quite as high, so he has to pivot out the last little part of it.

But that technique, paired with shane o'neill's skill, paired with on michael jordan's body

type, you could potentially see a 1080 shove it on flat.

But again, i wouldn't hold your breath for that one.

So that's it for this time.

This one ended up being a lot more work than i was expecting it to be, but i think it's

pretty cool to know what the human limits are of stuff like this.

So until next time, here are some more videos you might want to check out.

I'm starting to build a bit of a playlist of these physics questions, but i have a lot

more other stuff from game reviews and everything else.

So check that stuff out here, and make sure you tap my logo on screen to subscribe and

keep learning new things about skateboarding three times a week.

Thanks for watching.