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Why roller coaster loops aren't circular

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There’s this coaster in Hershey Park Pennsylvania, called the Sooper dooper looper. On it, you come around this bend that’s full of trees blocking your view and before you know it you’re hurtling down the track at 45 miles per hour toward a thrilling 75-foot loop. According to Hershey's website, it’s the “first-ever looping roller coaster on the east coast”. But the good people at the Hershey company have that wrong. Because about 75 years before the Sooperdooperlooper, Coney Island — in my hometown of New York — was home to the first two looping coasters in America. Unlike the Sooperdooperlooper, which has been around for almost 50 years, these early looping coasters didn’t even last a decade.

Because it turns out, loops shouldn’t be made like this. Looping roller coasters got their start in Europe as early as 1842. Back then, they were called centrifugal railways they... weren’t super popular or successful. They tried a few more in Europe, as we understand it, these were short-lived and more of a novelty.

That’s Randy Geisler, former president and current member of the historical committee for American Coaster Enthusiasts. I've loved roller coasters my entire life. The movements, the speed, and just the world whipping by you in every direction.

People in the 1800s didn't have the same fondness for looping coasters. And that didn’t change much when America built its first looping roller coaster in 1895:

Coney Island’s Flip Flap Railway. That’s because these coasters had a few major problems. The biggest one being, they made the loops circular. In physics, we love perfect circles. It's an easy shape. But from a human experience point of view, it is a nightmare.

That’s Matt Anderson. I’m a physics professor at San Diego State University. To make it around the Flip Flap’s circular loop cars needed to move really, really fast while changing directions. The coaster itself is trying to push you up in a new direction. Your head, your spine, and everything else want to keep going in a straight line. But the coaster is saying, no, you gotta curve into this arc. Changing directions so rapidly causes a spike in G forces. You've gone from one G instantly to 12 or 14 Gs. That’s a big problem. 6Gs is the most a human body can handle on a rollercoaster and only for about a second.

At that force... All the blood is just being pulled out of your head and you will pass out. You can see how wild the G-forces are in this looping-coaster-simulation chart created by George Sidebotham, a mechanical engineering professor at the Cooper Union.

Because of our chat, he became so obsessed with the circular loop problem that he made a bunch of looping-coaster-simulation charts. This line represents a circular loop like the Flip Flaps. After jumping from 1 to 14 Gs, it would decrease as you reached the top of the loop then ramp up again to 14 at the bottom, and then back to 1 as the coaster leaves the curve. Passengers were completely rattled. The Flip Flap, being made mostly of wood, didn’t help either. Wood is stretchy and compress-y. You can see the circle moving as the cart goes around. It's stressing it this way and then it's stressing it that way. It just looks like an engineering catastrophe about to happen.

The next looping coaster built on Coney Island, the Loop, Was crafted to avoid all those issues. It was made entirely out of steel, which offered more stability. And the circle was switched to more of an upside-down teardrop shape. Squeezing the sides in helped ease the transition into and out of the curvature reducing the G forces and creating a smoother, less body-damaging ride. But still, they had a capacity problem.

Neither the Flip Flap nor the Loop the Loop could support more than a few riders at a time because the loops were small, and so the cars had to be small, too. Most of the cars, seated 4 people. And pretty much you could only send people about once every 5 minutes. They just couldn't make enough money. More people would watch than ride. The Flip Flap lasted 7 years, the Loop lasted 9. And all other looping coasters around the world shut down shortly after.

It seemed like the end of the track for loops. That is... until something new came along. In 1959, Disney unveiled the Matterhorn. It didn’t have a loop but it was the very first tubular steel coaster. Unlike regular steel which was solid throughout, tubular steel was hollow in the middle, making it lighter-weight, and easier to bend into smooth arcs and curves. Unlike wood, tubular steel could support heavy weight and more dynamic movement. And in 1976, Six Flags Magic Mountain debuted the first modern vertical looping coaster, made with tubular steel.

The Great American Revolution squeezed the loop even more than the Loop creating what’s known as a “clothoid loop". It gets smaller and smaller as you get to the top to try and even out the G forces. And then it does the exact opposite as it comes back down. With clothoid loop-shaped coasters, designers could distribute the G’s more evenly and decide more precisely how many Gs to hit... about 4.9 in the case of the Great American Revolution. A much smoother experience compared to the Flip Flap's uneven G force spikes from 1 to 14 to 9 to 1.

This clothoid loop — crafted using strong and easy-to-bend tubular steel, and built 113 feet high meant that the Great American Revolution could support 20 riders at g forces that feel exhilarating instead of harmful. And since then loops have exploded in popularity. Double loops! Crazy loops!

And that Sooperdooperlooper in Hershey Park which, by the way, can proudly claim that it’s the first modern looping roller coaster on the east coast.


For more information and travel tips about cities and what they have to offer, we suggest visiting our city guide with over 100 cities in the USA, Canada, and many other countries around the world.

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