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The generic roller coaster vertical loop is the most basic of roller coaster inversions. Specifically, the loop refers to a continuously upward-sloping section of track that eventually results in a complete 360 degree circle. At the top-most piece of the loop, riders are completely inverted.
History
The vertical loop is not a recent roller coaster innovation. Its origins can be traced back to the 1850s when the French built the Centrifuge Railway. The ride relied on centripetal forces to hold the car in the loop. The ride was shut down after an accident. [1] Later attempts to build a looping roller coaster were carried out during the late 1800s with the Flip Flap Railway at Sea Lion Park. The ride was designed with a completely circular loop (rather than the clothoid of modern looping roller coasters), but caused neck injuries due to the intense G-forces pulled with the tight radius of the loop. The next attempt at building a looping roller coaster was in 1901 when Edwin Prescott built the Loop-the-Loop at Coney Island. This ride used a modern clothoid shaped loop and a steel structure, however more people wanted to watch the attraction, rather than ride. No more looping roller coasters were built until the Revolution opened at Six Flags Magic Mountain in 1976. In 2000, a modern looping wooden roller coaster was built, the Son of Beast at Kings Island. Although the ride itself was made of wood, the loop was supported with steel structure. Due to maintenance issues however, the loop was removed at the end of the 2006 season.
Loops on non-rollercoasters
Designers of other rides have been tempted sometimes to include similar loops. Usually safety concerns lead them to quickly reconsider.
One case where they did not was at New Jersey's infamous Action Park, where one was built on a water slide and then opened to the public. Riders were warned to descend with their legs crossed and arms across the chest to traverse the loop safely (See picture on this discussion thread). Too many ignored this instruction, however, and either got stuck atop the loop (requiring the construction of an access hatch to free them) or injured themselves, or both. It was closed after a month, but remained on view for the remainder of Action Park's operations.
It has been dismantled since then and will probably not be rebuilt. As of 2006, no other looping water slides have opened at any parks. However, since 2002, the Swiss company Klarer Freizeitanlagen AG has been working on a safe design for a looping water slide and have now built and tested a 1:1 prototype of their design. [2] [3]
Physics/Mechanics
In actuality, most roller coaster loops are not circular in shape. Most loops are clothoid in shape -- slightly vertically thinner. The shape resembles an inverted tear drop and allows for less intense G-forces throughout the element for the rider. The use of the clothoid was pioneered in 1975, on Revolution at Six Flags Magic Mountain, by Werner Stengel of leading coaster engineering firm Ing.-Büro Stengel GmbH.
At the top of a loop, gravity helps to pull the rider around the bend; at the bottom, gravity and the loop are in opposition. Also, the train is slower at the top of the loop. If the loop's curvature is constant, clearly the rider is subjected to the most force at the bottom. If the curvature of the track changes suddenly, as from level to a circular loop, that greatest force is imposed almost instantly (see jerk). Gradual changes in curvature, as in the clothoid, reduce the force maximum (permitting more speed) and allow the rider time to cope safely with the changing force.
Obviously this "gentling" runs somewhat contrary to the coaster's raison d'être. Schwarzkopf-designed roller coasters often feature circular loops resulting in intense rides -- a trademark for the designer.
It is rare for a roller coaster to stall in a vertical loop, although this has happened before. Turbine (then known as Sirocco) at Walibi Belgium once stranded riders upside-down for several hours. The design of the trains and the rider restraint system (in this case, a simple lap bar) prevented any injuries from occurring, and the riders were removed with the use of a cherry picker.
External links
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