The roller coaster is a popular amusement ride developed for amusement parks and modern theme parks. LaMarcus Adna Thompson patented the first roller coaster on January 20, 1885. The earliest roller coasters descended from Russian winter sled rides held on specially constructed hills of ice, especially around St Petersburg. They were usually built 70 to 80 feet tall and consisted of a 50 degree drop. By the late 1700s their popularity was such that entrepreneurs elsewhere began copying the idea, using wheeled cars built on tracks. One such company was `Les Montagnes Russes à Belleville` which constructed and operated a gravity track in Paris from 1812. The first loop track was probably also built in Paris from an English design in 1846, with a single-person wheeled sled running through a 13-foot diameter loop. None of these tracks were complete circuits. Even today the French use the term montagnes russes (russian mountians) to refer to roller coasters.
The coaster cars ride along on a long, winding track. The track begins with a steep ascent, which builds up a reservoir of potential energy in the coaster car. The rest of the track`s hills, valleys, twists and turns serve to change the built-up energy back and forth between potential energy and kinetic energy. As the train moves, it gradually loses energy to friction until it reaches the end of the ride. A roller coaster`s energy is constantly changing between potential and kinetic energy. At the top of the first lift hill there is maximum potential energy because the train is as high as it gets. As the train starts down the hill, this potential energy is converted into kinetic energy -- the train speeds up. At the bottom of the hill there is maximum kinetic energy and little potential energy. The kinetic energy propels the train up the second hill building up the potential-energy level. As the train enters the loop-the-loop it has a lot of kinetic energy and not much potential energy. The potential-energy level builds as the train speeds to the top of the loop but it is soon converted back to kinetic energy as the train leaves the loop. The coaster tracks serve to channel this force -- they control the way the coaster cars fall. If the tracks slope down, gravity pulls the front of the car toward the ground, so it accelerates. If the tracks tilt up, gravity applies a downward force on the back of the coaster, so it decelerates.
Since an object in motion tends to stay in motion as per Newton`s first law of motion, the coaster car will maintain a forward velocity even when it is moving up the track, opposite the force of gravity. When the coaster ascends one of the smaller hills that follows the initial lift hill, its kinetic energy changes back to potential energy. In this way, the course of the track is constantly converting energy from kinetic to potential and back again. This fluctuation in acceleration is what makes roller coasters so much fun.
In most roller coasters, the hills decrease in height as you move along the track. This is necessary because the total energy reservoir built up in the lift hill is gradually lost to friction between the train and the track, as well as between the train and the air. When the train coasts to the end of the track, the energy reservoir is almost completely empty. At this point, the train either comes to a stop or is sent up the lift hill for another ride.
There are two major types of roller coasters, distinguished mainly by their track structure.
The tracks of wooden roller coasters are something like traditional railroad tracks. The metal wheels of the coaster train roll on a flat metal strip, measuring 4 to 6 inches (10 to 15 cm) across. This strip is bolted to a sturdy running track made of laminated wood. In most coasters, the car wheels have the same flanged design as the wheels of a train -- the inner part of the wheel has a wide lip that keeps the car from rolling off the side of the track. The car also has another set of wheels (or sometimes just a safety bar) that runs underneath the track. This keeps the cars from flying up into the air.
Wooden coaster tracks are braced by wooden crossties and diagonal support beams. The entire track structure rests on an intricate lattice of wooden or steel beams, just like the beam framework that supports a house or skyscraper. With these materials, designers can combine the hills, twists and turns into an infinite variety of course layouts.
They can even flip the train upside down (though this is rare in modern wooden coasters). But, since the track and support structure are so cumbersome, a wooden track is fairly inflexible. This makes it difficult to construct complex twists and turns. In wooden coasters, the exhilarating motion is mainly up and down.
The world of roller coasters changed radically with the introduction of tubular steel tracks in the 1950s. As the name suggests, tubular steel tracks consist of a pair of long steel tubes. These tubes are supported by a sturdy, lightweight superstructure made out of slightly larger steel tubes or beams.
In tubular steel coasters, the train wheels are typically made from polyurethane or nylon. In addition to the traditional wheels that sit right on top of the steel track, the cars have wheels that run along the bottom of the tube and wheels that run along the sides. This design keeps the car securely anchored to the track, which is absolutely essential when the train runs through the coaster`s twists and turns.