[Narrator] There are people who like roller coasters,

there are people who love roller coasters,

and then there are people like Will Pemble.

All I need is a little bit of encouragement

to say yes to a crazy idea.

My name is Will Pemble, and I built a roller coaster

in my backyard.

[Narrator] Well of course he did.

I built a roller coaster in my backyard because

once upon a time when my son was 10 years old

Here we go.

We came home from vacation and he asked me,

Wouldn't it be great if we had a roller coaster

in the yard?

And it took me five seconds to know for absolute certain

that it would be great.

[Narrator] But first Pemble had to figure out

how to build one.

The first time we wanted to build a roller coaster

there wasn't a whole lot of information about it.

Okay, all things considered, not so bad.

There were a couple of videos online that we could look at.

The companies that build these don't really like

to share their secrets and so a lot of what we did

we had to kind of learn as we went.

I'm trained a little bit as an engineer.

I'm trained a little bit as a carpenter,

as a builder, I've learned how to weld.

I know some stuff but really we had to figure this out

through trial and error and while we were doing that

we had to make sure that it all stayed perfectly safe.

The trick to having your roller coaster turn out

the way you hope it will is you do the math.

You figure out what are the laws of physics

that are gonna govern this thing,

and how do I make those calculations

and understand what the coaster is gonna do

before you ever put a shovel in the ground,

before you even bend a piece of steel.

[Narrator] In total, he's built five coasters.

The first one I built in my backyard,

and it was made out of PVC and wood

about 180 feet of track.

The second roller coaster I built in my front yard

because there was already a roller coaster

in the back yard.

That's fun.

The third roller coaster I built for the Maker Fair

in San Francisco because I wanted to show my roller coaster

to more people than would fit in my yard.

The fourth roller coaster I built at a friend's house

because his kid wanted a roller coaster

and we were friends, and this is the fifth roller coaster,

the Gold Boss that I tried to improve on everything

we had done before and I feel like we've almost

gotten ourselves there.

[Narrator] The latest is a stomach swirling

stretch of steel right out the back door

of his northern California home.

A lot of people would put a swimming pool

in a yard like this.

Just a lot of people, most people would.

I didn't want that.

I didn't think that that would be particularly engaging.

I didn't think my kids would learn a whole lot from that,

and look, I have a roller coaster.

[Narrator] There are no tickets, no lines.

Just strap into the homemade cart, inch up the hill

and then fly through the turns.

The way the coaster works right now

is you get in, you go on the chain lift.

It takes about 30 or 40 seconds to get from the bottom

of the hill to the top of the hill.

So it's a pretty slow lift hill.

What that does, and we could speed it up,

but we didn't, but what that does is it gives you time

to kind of review your choices and think about

what you've done.

'Cause you look down at the thing

and it doesn't look like any roller coaster

that you've ever ridden before.

Its like oh my God, who built this thing?

Are you sure this is safe?

And by the time you get to the top you're just like,

you know this was a terrible idea,

and I have the exact same feeling.

So you get that for about 30 seconds

and then a couple of seconds when you just crest the hill

you're like, oh okay, and just like a nice, gentle,

and then you do, you just like drop off the edge

of the Earth into this dive.

And inside a couple of seconds, at the bottom of that

first straightaway there, you're going 18 miles an hour.

And then you dive into a 70 degree banked turn.

And you go 360, 450 degrees of 70 degree banked turn

back up into the sky and then you ride over this truss

and then drop down into that turn over there,

which is right next to the wall.

You go up the next camel hump which points off

the edge of the wall, and on the other side of that wall

is a 15 foot drop into I don't know what

and then you turn off of that and then you ride

into another bank and then you roll back to the station.

All of that takes less time than it took me

to describe it.

It takes like 17 seconds from the top of the lift

til back to the station.

And it's utterly horrifying, thrilling,

and the best part of all for me,

it's very very smooth.

[Narrator] But it's missing something.

At least according to Pemble's online fans

who follow his coaster building on his YouTube channel.

This coaster is awesome and a lot of people have

seen it online and we get a lot of help and

encouragement from people who watch my kooky

little videos about it.

One question that keeps coming up over and over again

is, doesn't it go upside down at any point?

It doesn't go upside down yet.

So I've had a number of people ask me if we could

add some kind of inversion, some way to make

the roller coaster go upside down here in the yard.

I have to try.

[Narrator] Now Pemble and his coaster collaborator

John Elliot, are making the loop de loop dream a reality.

And yes, he insists this is safe.

Before we built this coaster or any of the other coasters

we started with a spreadsheet and we did meter by meter

math and physics on how the cart would behave.

How the track would behave,

what the slopes needed to be, what the bank turn

would need to be, all of the things we figured out

before we ever started to build any of it.

That's the only way you can have it turn out predictably.

[Narrator] To absolutely guarantee that things are safe,

Pemble turns to his friend, Todd.

Okay Todd isn't really his friend.

He's a crash test dummy.

I know that I weigh 200 pounds and I wanna ride

my roller coaster, so we put our 300 pound

crash test dummy, Todd, on the roller coaster

and let him ride it a bunch of times

before we ever put a human being on it.

So we test everything.

Todd.

[Narrator] But an upside down loop

is a different thing entirely.

The physics of loops is kind of interesting

and presents a number of opportunities and challenges.

One of the main things that you think about

in loops is centripetal acceleration

and that's the force with which your cart

is pushing on the outside of your loop.

So how hard is it pushing against the track?

With a perfectly circular loop

you need incredible speed, incredible centripetal

acceleration to keep the cart pushing up

when it reaches the top of the loop.

[Narrator] Most commercial coasters these days

use an upside down tear drop shaped loop

called the clockoid loop.

So the way a clockoid loop looks is

when you enter the loop you have a nice big radius

and then the radius decreases, decreases, decreases

decreases very tight turn at the top and then back

out of the loop.

One of the challenges of our clockoid loop

will be that we can't build a really really big one.

We're gonna need a relatively small radius loop.

The top of our coaster is 20 feet from the bottom

of our coaster, so we basically have 20 feet

of altitude, 20 feet of potential energy

that we can use to get in and out of the loop

and when we exit the loop we still have to

finish the whole rest of the course,

and so we can't use up all our energy

just to get through this loop.

If we enter the loop at a certain speed

when we run the math on that what I'm starting

to find is that the G's that you're gonna pull,

the force on the cart and the rider and the track

and the whole system is gonna get pretty freaking

high when you're entering that loop.

And by high I mean like three, four, five G's.

Really high.

It's not gonna be fun, it's not gonna feel good.

It might be something that you'd be proud of having

achieved, but it's not gonna be something

you would enjoy.

[Narrator] After a weekend of cutting, bending,

grinding and welding, Pemble and Elliot

have a new section of track.

It's not a loop after all.

It's a barrel roll.

Which should fit better into the existing layout

and according to Pemble won't subject the rider

to painful G forces.

So what we got here is the very top part

of the barrel roll.

So what happens is our cart will enter,

there's entry down there, but basically the cart enters

this part of the barrel roll.

The rider is pointing this way

and then they spin around this piece of track,

and by the time they finish this top part

they've made a 180 degree roll from this to that

over the course of about 18 feet,

and so we're feeling very happy about this because

this was the hardest part to build.

The materials to build this coaster

cost a little bit less than $10,000.

It's the labor that's gonna get you.

This roller coaster took us about three months.

Me and my friend John worked on it together

and we probably put about 300 hours of labor into the thing.

So not a trivial amount of work.

I've had a really lucky and wonderful life.

I built one of the biggest web hosting companies

in the world, and I sold that,

and I made a little bit of money.

I run a management consulting company now

called Gold Boss.

We teach leadership and teamwork.

It's amazing how much of what we learn

on the roller coaster project, figures into

the training and consulting that we do.

[Narrator] The new section of barrel roll track

was fitted right after the first drop.

It really changes how the coaster rides.

In this roll the center of gravity of the rider

is way down by your waist,

which means that your head whips around and

there's just like a whole lot of energy.

It's not comfortable.

It's borderline not safe.

Utterly scary.

Ooh, ooh!

[Narrator] Pemble is the only person

who has ever ridden it and he'll probably be the last.

Ahh!

It seemed like an incredibly good idea

at the time.

Now it's really cool to watch, it's really fun to roll

the cart over the thing.

I've ridden it once and that was plenty.

[Narrator] But if you're a crash test dummy like Todd,

remember him?

Then it's a ton of fun to ride.

So my key take away from building an inversion

into a roller coaster is if you don't study

engineering and roller coaster manufacturing,

you're just not gonna get it right the first time.

And that's okay.

We're just gonna do it again.

I think the best thing to do for this coaster

is to tear it down completely and re build it

and design it from day one with an inversion in mind.

My advice to anybody building a backyard roller coaster

go slow, do the math, be careful and know when

to no ride it.

[Narrator] And don't forget to have a Todd on hand.