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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.
Resources
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
