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Coaster Creation: Building Scream Machines

Posted September 19, 2012 10:16 AM by HUSH

You sit down and chat nervously with your friend. Your seat rocks forward and a very audible CLINK*CLINK*CLINK overcomes your senses. Gravity pulls you to the back of your seat and you get a wide-eyed view of the blue sky above. And when you finally look down, you're 120 feet in the air and just noticing the white-knuckle grip you have on the handle in front of you.

And I suspect that unless you insult your ride mates, you're about to have 2 minutes of thrills and howling. But beware the new euthanasia rollercoaster--a ride meant to kill its riders. Who's crying now?

While there are clearly many physical laws in place from the lift hill to the station brakes, rollercoasters are also remarkable feats of engineering considering the impressive specs of some of the world's best coasters. Kingda Ka, located at Six Flags Great Adventure in New Jersey, USA, blasts off to 128 mph in just 3.5 seconds, and reaches a high of 456 feet above the earth.

I'm here to provide an overview of the principals and production of the world's scream machines. And to really get in the coaster mood, may I suggest a theme song?

Coaster Physics

To complete the circuit of the coaster track, the train must have enough potential energy. In most instances this is accomplished by the ascension of a lift hill, and the distinct ratcheting sound is the result of an anti-rollback design in case the lift chain breaks.

The lift chain itself is best thought of as a roller chain driven by an electric motor. A chain dog is attached near the front of the coaster train and is deployed by an electromagnet under the track. The dog retracts upon reaching the top of the hill.

(Another form of coaster acceleration, hydraulic launching-such as on Kingda Ka, is accomplished by compressing nitrogen in an accumulator. Releasing the extreme pressure to a turbine pulls the coaster to speed in 2 to 4 seconds. This type of coaster is exclusively made by Intamin, a top coaster engineering firm. Linear induction motors are also capable of launching coasters.)

Before a descent, the coaster has potential energy. Transferred to kinetic energy at the bottom of hills, the coaster train will not be able to reach the same height as the previous hill due to conservation of energy (energy is lost to friction and drag).

The forces a rider experiences is what adds excitement to the ride. Gravity is always a factor, so varying speeds will accelerate the rider within the seat. One of the most sought-after feelings on a rollercoaster is the airtime of when the body accelerates upwards, while the train accelerates downward.

Inversions like corkscrews and loops put centrifugal forces to work. Gravity always pulls the rider towards the Earth, but velocity overrides this sensation in loops.

Coaster Engineering

Making a safe, fun, and relatively inexpensive coaster are the most important design goals , and many rollercoasters have taken an unfortunate 'cookie-cutter' construction method. The Boomerang has 45 locations worldwide. While this makes coasters more accessible, it decreases originality.

Rollercoaster tracks require flexibility in their design since they carry dynamic loads, and engineers have accounted for this. Reinforced concrete serves as a foundation for supports, which bend with the tension (on hills) and compression (on valleys) the metal coaster components endure. Coaster engineers widely use triangle designs in track sections, since it is one of the strongest geometric shapes.

Some of the most incredible coaster designs-like Hershey park's Fahrenheit, with a 97┬░drop-are drafted on computer programs meant for Boeing.

Steel coaster fabrication is much more precise than that of their wooden counterparts. Tracks themselves are bended steel pipes with steel supports. Manufacturers keep their bending techniques very secretive-an industry standard to keep a competitive edge-and ship sections of coaster to the job site. Unfortunately, bent steel pipe shortens the fatigue life of tracks, and about every 25 years the coaster's entire track should be replaced. More recent processes extend track lives. The New Texas Giant was assembled by welding planar pieces of steel together with no bending or heating.

Wooden coasters require higher levels of tolerance due to the on-site carpenter assembly and the imperfect nature of wooden planks. This gives wooden coasters the bumpy and rough feel that enthusiasts love. The rails of wooden roller coasters are bent on site according to the skeleton design. With this style of manufacturing, wooden coasters need their planks replaced every four to seven years, leading to lengthy downtimes. More recent innovations have coaster manufacturers assemble the wooden components in preformed sections with milled rails. This results in a smoother ride as well as less coaster maintenance.

Did I answer everything there is to know about coasters? No.

Will the information here prevent you from puking on one? Certainly not.

Did I enjoy writing this post? Absolutely. Rollercoasters are one of my favorite things in this world, located somewhere on my list between ice hockey and BBQ. I've ridden many of North America's best coasters, and I'm known to travel hundreds of miles to learn about and ride each one. It's a simple personal interest.

And if you're the type who doesn't like rollercoasters, we officially can't be friends.


Image credits, by order: This Southern Blog, Wikimedia, How Stuff Works, Wikimedia, Coaster-Net, Coasters 101

Coaster-Net - The Engineering Behind Coasters Part 1: Track and Supports

How Stuff Works - How Roller Coasters Work

Wikipedia - Lift Hill

Coasters 101 - Track Fabrication; Daily Inspections

Popular Mechanics - Building America's Most Extreme New Roller Coaster


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Re: Coaster Creation: Building Scream Machines

09/24/2012 4:13 PM

When I was studing for my PE license, I had some practice study material for it.

In it it showed previous answers to questions. And reasons why you should be licensed.

One was design of a roller coaster loop.

An actually designer written response actually was something like this,

"You go through the loops as fast as you can before anything happens".

“ When people get what they want, they are often surprised when they get what they deserve " - James Wood

Join Date: Nov 2011
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In reply to #1

Re: Coaster Creation: Building Scream Machines

10/20/2012 7:11 PM

"You go through the loops as fast as you can before anything happens".

Makes sense. What's wrong with that?

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