Engineering Topic #3: Rollercoasters

Topic number #3. The first one was Sputnik 1, with the second being the Quebec Bridge Disaster(s). That thread on it got me wondering

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Types of roller coasters

Today, there are two main types of roller coaster:

* Steel roller coasters
* Wooden roller coasters

Steel coasters are known for their smooth ride and often convoluted shapes that frequently turn riders upside-down via inversions. Wooden coasters are typically renowned by enthusiasts for their rougher ride and "air time" produced by negative G-forces when the train reaches the top of hills along the ride.

Mechanics

The cars on a typical roller coaster are not self-powered. Instead, a standard full circuit roller coaster is pulled up with a chain or cable along the lift hill to the first peak of the coaster track. The potential energy accumulated by the rise in height is transferred to kinetic energy as the cars race down the first downward slope. Kinetic energy is then converted back into potential energy as the train moves up again to the second peak. This hill is necessarily lower, as some mechanical energy is lost to friction.

Not all roller coasters feature a lift hill, however. The train may be set into motion by a launch mechanism such as a flywheel launch, linear induction motors, linear synchronous motors, hydraulic launch, compressed air launch or drive tire. Such launched roller coasters are capable of reaching higher speeds in a shorter length of track than those featuring a conventional lift hill. Some roller coasters move back and forth along the same section of track; these are known as shuttles and usually run the circuit once with riders moving forwards and then backwards through the same course.

A properly designed roller coaster under good conditions will have enough kinetic, or moving, energy to complete the entire course, at the end of which brakes bring the train to a complete stop and it is pushed into the station. A brake run at the end of the circuit is the most common method of bringing the roller coaster ride to a stop. One notable exception is a powered roller coaster. These rides, instead of being powered by gravity, use one or more motors in the cars to propel the trains along the course.

If a continuous-circuit roller coaster does not have enough kinetic energy to completely travel the course after descending from its highest point (as can happen with high winds or increased friction), the train can valley: that is, roll backwards and forwards along the track, until all kinetic energy has been released. The train will then come to a complete stop in the middle of the track. This, however, works somewhat differently on a launched roller coaster. When a train launcher does not have enough potential energy to launch the train to the top of an incline, the train is said to "roll back." On some modern roller coasters, such as Top Thrill Dragster at Cedar Point in Sandusky, Ohio, this is an occurrence highly sought after by many coaster enthusiasts.

Timing

Most large roller coasters have the ability to run two or more trains at once. These rides use a block system, which prevents the trains from colliding. In a block system, the track is divided into several sections, or blocks. Only one train at a time is permitted in each block. At the end of each block, there is a section of track where a train can be stopped if necessary (either by preventing dispatch from the station, closing brakes, or stopping a lift). Sensors at the end of each block detect when a train passes so that the computer running the ride is aware of which blocks are occupied. When the computer detects a train about to travel into an already occupied block, it uses whatever method is available to keep it from entering. The trains are fully automated. The above can cause a cascade effect when multiple trains become stopped at the end of each block. In order to prevent this problem, ride operators follow set procedures regarding when to release a newly-loaded train from the station. One common pattern, used on rides with two trains, is to do the following: hold train #1 (which has just finished the ride) right outside the station, release train #2 (which has loaded while #1 was running), and then allow #1 into the station to unload safely.

Safety

Because roller coasters are intended to feel risky, accidents such as the September 5, 2003 fatality at the Disneyland Big Thunder Mountain Railroad, attract public attention.

Statistically, roller coasters are very safe. The U.S. Consumer Product Safety Commission estimates that 134 park guests required hospitalization in 2001 and that fatalities related to amusement rides average two per year. According to a study commissioned by Six Flags, 319 million people visited parks in 2001. The study concluded that a visitor has a one in one-and-a-half billion chance of being fatally injured, and that the injury rates for children's wagons, golf, and folding lawn chairs are higher than for amusement rides.[7] In fact, driving to the amusement park has a higher risk of injury than riding the rides at the amusement park. It is not unusual for park management to pay higher insurance premiums for carousels than they do for roller coasters.

Many safety systems are implemented within roller coaster systems. The key to the mechanical fail safes is the control of the roller coaster's operating computers: programmable logic controllers (often called PLCs). Most roller coasters run with three separate PLCs; however, only one PLC is required to detect a fault for the ride's fail-safes to be activated. This is often the reason that the ride trains may stop on the lift or the brake runs, yet after a short time the ride starts again without any obvious maintenance by staff. It is likely in such a case that one of the PLCs detected a fault by mistake, and the ride operator only needed to restart the ride.

Nevertheless, accidents do occur.[8] Regulations vary from one authority to another. Thus in the USA, California requires amusement parks to report any ride-related accident that requires an emergency room visit, while Florida exempts parks whose parent companies employ more than 1000 people from having to report any accidents at all. Rep. Ed Markey of Massachusetts has introduced legislation that would give oversight of rides to the Consumer Product Safety Commission (CPSC).

Ride accidents can be caused by riders or ride operators not following safety directions properly, but in extremely rare cases riders can be injured by mechanical failures. One such example was the 2006 de-railing of one car on the Wild Thing roller coaster at Valleyfair!.

In recent years, controversy has arisen about the safety of the increasingly extreme rides. There have been suggestions that these may be subjecting passengers to translational and rotational accelerations that may be capable of causing brain injuries. In 2003 the Brain Injury Association of America concluded in a report that "There is evidence that roller coaster rides pose a health risk to some people some of the time. Equally evident is that the overwhelming majority of riders will suffer no ill effects." [9]

A similar report in 2005 linked roller coasters and other thrill rides with potentially triggering abnormal heart conditions that could lead to death.[10] Autopsies have shown that recent deaths at various Disney parks, Anheuser-Busch parks, and Six Flags parks were due to previously undetected heart ailments.

Physics

Roller coaster design is a science, as well as an art: the designer must use knowledge of kinematics to avoid overstressing the human body and building an uncomfortable or dangerous ride. The acceleration is a significant design parameter, as is the rate of change of acceleration, jerk. Jerk is often used in engineering as some precision or fragile objects—such as passengers need time to sense stress changes and adjust their muscle tension to avoid injuries such as whiplash.

http://en.wikipedia.org/wiki/Rollercoaster
http://science.howstuffworks.com/roller-coaster.htm
http://www.learner.org/interactives/parkphysics/coaster/

godtabh

We should organise a field trip to FunderLand!

I wonder is there any in house design companies in Ireland able to do any of this work

gucci

a lecturer showed us a very good documentery into the rollercoaster design, but i dont know the name of it....so this post isnt really that useful. but it basically showed 2 guys (americans) who were roller coaster designers and who have worked on an number of designs in 6 flags and some other american theme park