Originally built in 2005, the roller coaster’s turnaround was rebuilt this summer to include a 360-degree barrel roll that is visible to passersby. The tracks for the wooden coaster’s inversion are formed from 12 thin strips of wood that have been nailed together to form the curves of the track line. The Gravity Group, LLC
The Hades 360 roller coaster, in Wisconsin Dells, Wisconsin, is the first wooden roller coaster to perform a 360-degree corkscrew.
June 25, 2013—Corkscrew. Barrel Roll. Inversion. All of these terms are used to describe a long-sought-after goal: taking a wooden roller coaster upside down. Last month, the newly christened Hades 360 roller coaster, located at the Mt. Olympus Water and Theme Park in Wisconsin Dells, Wisconsin, became the first wooden roller coaster to accomplish just that. Originally built in 2005, the coaster’s turnaround was rebuilt this summer to include a 360-degree barrel roll that is fully visible to passersby.
“It’s something that we’ve always wanted to do,” says Korey Kiepert, P.E., an engineer and partner in the Cincinnati, Ohio-based Gravity Group, the company that designed the ride and added the inversion. “It’s something that modern technology has allowed us to do ….We just tried to take our existing bag of tools and apply it to something new. And I think that’s the heart of engineering: taking what you know, and trying to make something new out of it.”
The 4,726 ft long roller coaster, originally called the Hades, reaches speeds of 60 mph, has a lift height of 136 ft, and includes a 140 ft drop at 65 degrees into an underground tunnel. The ride also crosses beneath the park’s parking lot twice, boasting the world’s longest underground tunnel for a wooden roller coaster, at 700 ft. The coaster also includes a dramatic 110-degree overbanked turn.
The key technology developments that enabled the inversion design to finally move forward include a new “Timberliner” train car design that Gravity Group unveiled in 2011 combined with advances in three-dimensional computer modeling software, Kiepert says. The new cars have the ability to twist quickly enough to pass through an inversion, while at the same time maintaining appropriate forces on the riders, says Chad Miller, P.E., a creative designer and engineer with the Gravity Group.
Three-dimensional software modeling and the recently developed
“Timberliner” train cars made it possible for a wooden roller coaster
to go upside down for the first time. Trains on the 4,726 ft long
Hades 360 roller coaster can reach speeds of 60 mph; the coaster
also includes a 110 degree overbanked turn, shown here.
The Gravity Group, LLC
The ability to protect riders from forces that transition too abruptly from one direction to another is crucial in roller coaster design, Miller explains. The new cars can twist at twice the rate of the typical cars that have been used for the last half-century. “We needed that kind of banking in order to avoid having these abrupt changes in the rider forces, especially from right to left, and left to right,” Miller says.
The Gravity Group uses the wood design software RISA 3D (created by Foothill Ranch, California-based RISA Technologies) to plan its rides. “We wouldn’t be anywhere without the computer and structural design packages,” Kiepert says. “It’s hard to believe [that] years and years ago they tried going upside down, at the turn of the century, and they made their rickety wooden loops and different things [without software.] The amount of analysis that we do—that we want to do, that we’re required to do—I mean, it’s tremendous. I can’t imagine not having a computer and just trying stuff out.”
The tracks for the inversion are formed from 12 thin layers of wood that have been nailed together to form the necessary curves of the track line. “Traditionally on a wooden roller coaster, there might be eight layers of 1 ½ inch board, whereas for this ride—because of the amount of twisting and bending that we were trying to do—we used 1-inch material,” Kiepert says. “We had material that was planed down [especially] for us, so it was thinner and we could put more twist into it—[but] the exact amount of twist, and what our limits are, that’s getting into ‘the colonel’s secret seven herbs and spices,’” he says.
Inverting a wooden coaster is a complicated business, Kiepert explains, because typically with wooden coasters, the structure is designed like a truss with posts that perform as the top and bottom chords would, and diagonal and vertical members that behave as the intermediate truss pieces. The track is built up with structural-grade bolted connections, and then track supports called ledgers are placed at the correct height to form the ride. “But as soon as we’re going upside down,” Kiepert says, the situation changes completely, because “instead of our track on the top side of the ledger, it’s going on the bottom side of the ledger, essentially.”
A traditional wood structure would have enclosed the loop completely, which would not have provided the visual impact that a visible barrel roll provides—both to the riders and to passersby. To provide enticing, open views, the design team hung the inversion from cantilevered steel channels supported by truss framing on one side of the track, according to Larry Bill, P.E., the Gravity Group engineer who performed the structural and civil engineering work on the design.
A wooden coaster is defined as a ride with a wooden track no matter what material he supporting structure is made from, Kiepert explains. Using steel structural members made it possible to cantilever the ledger from the side, he notes, and this enabled the design team to fit the inversion into the available section of track.
The design team typically uses treated southern yellow pine for its track, and in this instance it chose kiln-dried lumber treated with chromated copper arsenate. (See “China’s First ‘Racing’ Wooden Roller-Coaster Opens,” on Civil Engineering online.)
The corkscrew is situated on a similar foundation to that used for the original ride—a concrete slab-on-grade and grade beam system with epoxy adhesives attaching the track to the foundation, according to Bill. Grade beams measuring 18 in. wide and 3 to 4 ft deep have been filled with rebar so that they perform as required under tension and compression as the train and its passengers pass through the inversion, Kiepert says.
Now that an inversion on a wooden coaster has been accomplished, Kiepert says that engineers will have to determine their next goal. “Certainly now that we’ve gone and done the corkscrew, there are other inversions and other geometric shapes and things that we might try out,” he says. Steel-tracked coasters play with the seating position of riders, so the next generation of wooden roller coaster design could also follow that lead, he says.
A first-person video of the ride is available online.