- The Washington Times - Thursday, August 15, 2002

Jim Seay likes to send people for a ride. Mr. Seay, president of Premier Rides Inc. in Millersville, Md., has helped design some of the most thrilling roller coasters in the country, such as the Joker's Jinx at Six Flags America in Largo. He says it takes about two years to complete a ride once the brainstorming stage has begun. Each roller coaster is like one huge science project.
"If you could see the sophisticated electronics room it's 200 feet of computers, electrical switching components, and it's extremely impressive," Mr. Seay says. "From the park's perspective, it's very important that the people riding the rides don't think about the science that goes into the rides The goal of the park is to give you a once-in-a-lifetime thrill experience."
Roller coasters, commonly called "scream machines," are designed according to basic concepts of physics. Lacking engines, they store potential energy as they are pulled or propelled up their first, or "lift," hill then they simply coast on their tracks, responding to the forces of inertia and gravity. As technology advances, engineers search for ways to create more interesting experiences.
The Joker's Jinx, which opened during the summer of 1999, is essentially a "rocket sled ride," Mr. Seay says. The 7-ton train accelerates from zero to 60 mph in about three seconds. With a maximum height of 78 feet, the 2,705 feet of curving track in the 500-ton steel maze offer about a 1-minute-30-second journey. The coaster has four upside-down loops, 30 vertical curves and 25 horizontal curves.
"I've always loved thrill rides from a personal standpoint," Mr. Seay says. "They are a fun and exiting product to work on. I used to work in aerospace engineering, and now I work in entertainment engineering. It's a natural crossover of skills."
The first roller coaster, built in 1884, was towed manually up its lift hill. Later innovations included mechanical hoists, chains or other means of pulling the cars up the first hill. The Joker's Jinx, by contrast, is pushed, or "launched" by an electromagnetic acceleration system that uses linear induction motors (LIMs) placed along the track in the launch zone. When the nonferrous "reaction plates" on the sides of the coaster cars pass through the LIMs' magnetic field, the motion induces a current through the reaction plate, and the cars are pushed ahead of the magnetic wave.
For safety purposes, two operators push launch buttons simultaneously, which tells the controls to send a current to the linear induction motors. Then the train is catapulted forward.
Upon launch, the ride moves at about 1 g. The symbol g represents the pull of gravity on Earth. (Everyone experiences at least 1 g, the pull of gravity on his or her own body weight.) At its peak, the Joker's Jinx reaches 4 g. Engineers often try to design roller-coaster rides so that these forces go through one's spine, which helps keep riders in their seats.
Mr. Seay could predict the safety of the Joker's Jinx before it was built using finite element analysis computer software programs, which can determine whether a design will collapse because of stress. An example of the programs Mr. Seay used would be those made by Algor Inc. in Pittsburgh.
Engineers usually limit the rides to a maximum stress of about 6 g on the body in order to prevent possible injuries, such as riders blacking out. Also, a coaster structure usually only carries about one-tenth of what the frame is capable of holding.
Most states, including Maryland and Virginia, have adopted the safety guidelines set forth by the American Society of Testing and Materials in West Conshohocken, Pa. Its standards focus mainly on the construction and maintenance aspects of the coasters, primarily through building codes and regular visits from state inspectors.
While the Joker's Jinx uses electromagnetic technology to impel it along the rails, a different technology is at work at Paramount's Kings Dominion in Doswell, Va., where the world's first air-launched roller coaster, Hypersonic XLC, debuted in November 1999. HyperSonic XLC moves from zero to 80 mph in fewer than two seconds, propelled by air injected into cylinders that sit below the train.
The ride is also unique because it represents the first time a coaster was launched straight up in the air. Traditional roller coasters use chains to bring them to the top of the first hill. However, chains were not the best choice for a roller coaster that is launched vertically. Engineers used cables, similar to those that pull an elevator, to allow for a quicker ascent.
"Anybody who has ridden it will tell you it's a very intense experience," says Ned Hanson, head engineer at S&S; Power Inc. of Logan, Utah, which built the ride. "The intent is to feel like you're floating."

Yet neither of these takes the U.S. prize for length or height. That honor belongs to Millennium Force at Cedar Point amusement park in Sandusky, Ohio. At 310 feet, Millennium Force created by Cedar Fair Limited Partnership, which owns the park is the tallest roller coaster in North America and the first to break the 300-foot barrier. It also is the fastest, traveling about 93 mph.
Taking lateral forces into consideration, the overbank turn, which rotates the vehicle 122 degrees upside down, was created to eliminate side-to-side movements for the riders without slowing down the train. It opened in May 2000 as a collaborative effort between Cedar Fair LP and Intamin in Zurich, Switzerland.
"The higher you lift something, the faster its acceleration rate," says Rob Decker, corporate director of planning and design at Cedar Fair Limited Partnership, referring to the potential energy an object gains due to its position. For a brief moment at the top of each hill, riders are suspended in the air. Then, the potential energy transfers into kinetic energy, or energy of motion, as the coaster falls over the hill. The coaster receives all the energy it needs to complete its course after descending the first hill.
Millennium Force is initially pulled up the first hill through an elevator lift system that uses cables. This system is four times faster than using chains, which is a benefit to those standing in line for the ride.
Different types of wheels keep the ride smooth. Running wheels keep the coaster on the track and run on the top of the rails. Guide wheels run on the outside of the left and right rails and control movement from one side of the track to another. Up-stop wheels, which are positioned underneath the rails, keep the vehicle from leaving the track.
When roller coasters lean to the center of a turn, it is because of centripetal force, which is the force directed to the center of a circle. Engineers use this principle to determine what the necessary bank angle on the turn should be to prevent passengers from being bounced around while on the ride.
One juxtaposes the force created by the turn with the exact angle that eliminates lateral movement. If the bank angle on the turn is not steep enough, one will be thrown to the outside of the passenger seat because of centrifugal force, which is when a moving body tends to flee from the center of a circle.
Mr. Decker says most riders of the Millennium Force are terrified by its speed and love every second of it.
"It's a very scary thing," he says. "When we first announced the height and speed, everyone who was a coaster enthusiast had to get on the ride. Now people know how smooth it is. You don't feel like you've been shaken up and all rattled."

Bob Rogers, chairman and founder of BRC Imagination Arts in Burbank, Calif., says that because there are many tall and fast roller coasters in the United States, his company suggests differentiating rides through technology, using it to tell a story. For instance, an amusement park could use robotics to create a backdrop with animated people, talking birds or aliens throughout the ride. Computer graphics and animation also could be added.
"We're approaching limits as to what the human body can take," he says. "We will have to find other ways to make roller coasters more stimulating without exposing people to more danger We think the answer is that we have got to get better at the story and illusion to cause the danger to seem greater than it really is."
Whether the danger is true or imaginary, most people ride roller coasters for the thrill, says Brian Biseman, project engineer at Chance Morgan in La Selva Beach, Calif. His company created the Steel Dragon in Nagashima, Japan, which is the tallest, longest and fastest steel roller coaster in the world. With a speed of 95 miles per hour, it is 318 feet tall and 8,133 feet long. The first hill has a drop of 307 feet.
"Science is everything in how we design," he says. "They are just big physics models It's all about making curves on the rides that don't generate excessively high forces on riders, to avoid causing injury, yet maintaining sufficient forces to be fun and move the coaster."

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