TIME Design

WATCH: The Science Behind the World’s Biggest Wooden Roller Coaster

Whether you can't get enough of them or can't go near them, roller coasters rely on some pretty nifty tricks of physics and design.

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Your brain wants nothing to do with roller coasters—and for a wonderfully simple reason: your brain would very much like you to stay alive. So anything that’s designed to haul you up to the top of a very steep incline, drop you straight down, very fast, and repeat that process over and over again for a minute or two is something that elicits a simple, highly adaptive response in you—which pretty much involves running away.

That, at least, is how it’s supposed to work, but your entire brain isn’t in on the game. There are also thrill-seeking parts, adventurous parts, parts that like the adrenaline and serotonin and endorphin kicks that come from roller coasters. So while millions of people avoid the things, at least as many millions swarm to them, looking for ever bigger, scarier rides and ever bigger, better thrills. This summer they’ll get their wish, thanks to the opening of the appropriately named Goliath roller coaster, the biggest and fastest wooden coaster ever built, which just took its inaugural runs at the Six Flags Great America amusement park in Gurnee, Ill., about 50 miles north of Chicago.

Goliath is destined to be a tourist magnet, a cultural icon—at least until another, even bigger one comes along—and a lot of fun for a lot of people. But it’s also a feat of engineering and basic physics. And if you’re the kind of person who enjoys that sort of thing while hating the idea of actually ever riding on roller coasters—the kind of person I’ll describe as “me,” for example—there’s a lot to like about Goliath.

Modern roller coasters typically come in two varieties, wooden ones and steel ones—known unimaginatively if unavoidably as “woodies” and “steelies”—and coaster lovers debate their merits the way fans of the National and American Leagues debate the designated hitter rule.

Steelie partisans like the corkscrews and loop-the-loops made possible by the coasters’ bent-pipe architecture. Woodie fans prefer the old school clack-clack and the aesthetics of the entire structure. What’s more, plunging into and soaring through all the wooden bracing and strutwork necessary to keep the thing standing increases the sensation of speed because stationary objects that are close to you when you’re moving at high speed seem to whiz past so fast they blur. Steelies leave you more or less moving through open space, and that eliminates the illusion.

Goliath moves at a top speed of 72 mph, achieving that prodigious feat with the aid of a very simple fuel: gravity. As in all roller coasters, its biggest, steepest drop is the first one, because that’s the only way to generate enough energy to propel you through the rest of the ride—which is made up of steadily shallower hills. In the case of Goliath, that first hill is 180′ tall (55m), or about the equivalent of an 18-story building. The drop is an almost-vertical 85 degrees.

As test pilots and astronauts could tell you, such rising, falling, corkscrewing movement creates all manner of g-force effects. Most of the time we live in a familiar one-g environment. Climb to 2 g’s in a moving vehicle of some kind and you feel a force equivalent to twice your body weight. The maximum g’s Goliath achieves is 3.5. Get on the ride weighing 150 lbs., and for at least a few seconds, you’ll experience what it’s like to weigh 525 lbs.

But g forces can go in the other direction, too. With many roller coasters, the forces bottom out at about 0.2 g’s during downward plunges, meaning your 150 lb. one-g weight plummets to 30 lbs. That can give you a feeling of near-weightlessness. It’s also possible to achieve 0 g in a dive, which is how NASA’s famed “vomit comet” aircraft allow astronauts to practice weightlessness. On the Goliath, things go even further, with riders experiencing a force of minus 1 g.

“That means you’d be coming out of your seat,” says Jake Kilcup, a roller coaster designer and the chief operating officer of Rocky Mountain Construction, which designed and built Goliath. To ensure that that doesn’t happen, the Goliath cars are equipped with both lap bars and seat belts.

Though Goliath is made of wood, it does feature two so-called inversions—or half loops that take you to the top of a climb, then deliberately stall and plunge back down the same way. One includes a “raven turn,” or a twist in the track that turns the cars briefly upside down.

Even this much wouldn’t be possible on a wooden coaster if not for what Rocky Mountain calls its “Topper” track technology—a sort of hybrid of wood and metal. Most of the beams in the Goliath superstructure are made of nine laminated layers of southern yellow pine, steam-bent in stretches that call for curves and then kiln-dried. But the track itself also includes hollow metal rails running the entire 3,100 feet (or nearly a full kilometer) of the ride. The cars all have main wheels that sit on the rails as well smaller upstop and guide wheels that lock the cars to the tracks and keep them going where they’re supposed to.

“The Topper track gives a smoother ride than you get on an all-metal track,” says Kilcip, “and makes the overall roller coaster stronger than an all-wooden one.”

All that technology provides a relatively brief ride—just 87 seconds long, which is not atypical for roller coasters. For plenty of people, that’s way too short—which is what Six Flags is banking on to keep the turnstiles spinning. For plenty of other people, it’s precisely 87 seconds too long. And you know what? I’m not—um, I mean, those people aren’t—the slightest bit ashamed to admit that.

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