Roller Coasters

[TalonRider]

COASTER POWER

Except for a number of compact steel coasters (Schwarzkopf's Jumbo Jet-type coasters, for example) there are no motors mounted in the cars themselves. Coaster trains are indeed free-wheeling. However, there has to be some method of getting the trains to the gravity part of their course, and on nearly all roller coasters that is by way of the lift hill, which is almost universally at the beginning of the ride and is the highest point on the ride. the most prevalent means of conveying trains to the top of the lift hills is the continuously moving drag chain.

The process works like this: After the train is loaded and passengers are secured by some type of safety restraint, the station brakes are released and the cars roll by gravity --sometimes assisted by specially mounted trackside tires that are motorized to momentarily grip and propel the train-- toward the base of the lift hill. At this point, narrow metal protrusions (called "chain dogs") below two or more of the cars engage the sprockets of the chain, and the train is hoisted up the first hill. After cresting the apex, the train is automatically disengaged from the chain and completes its journey back to the station with only gravity and momentum as the power sourse. A few coasters feature a second lift hill partway through the course.

Some steel coasters use a tire-driven friction lift system, cables, and even magnetic propulsion, but the chain lift remains the most popular method. In addition, the sound of a chain lift and chain-dog system creats a certain apprehension for riders as their train clank-clank-clanks ominously up the lift hill.

The gravity factor presents designers with the challenge of using a finite source of energy to provide the most entertaining ride possible. That's where creativity and an understanding of physics, dynamics, and engineering are combined to assure that the train, and its passengers comfortably negotiate the layout and return to the unloading platform. There are countless crucial parameters with which designers must contend so that their rides operate consistently and safely under a variety of situations. Varying passenger loads, friction, amount and consistency of wheel lubrication, and wind drag are just some of the circumstances which can and do affect the way a roller coaster behaves on a particular run.

Seasoned riders are well aware how temperamental certain coasters can be, especially wooden rides. The amgient temperature, especially excessive heat and humidity, can dramatically determine the way a coaster train reacts on a given day. Also, a strong wind can act as a natural braking force, should the train encounter a pesky breeze at just the right angle.

On the upside of nature's atmospheric shenanigans, riding a roller coaster during a light rain or just after a storm can increase train speed dramatically, especially on wooden coasters. Water gathers on the rails, mixing with oil and grease to form an ultra-slick surface. This friction reduction makes for a

zippier-trip.

While the majority of the general public will postpone an amusement park visit if inclement weather is forecast, experienced coaster enthusiasts usually seize the opportunity. As long as there is no lightening involved (which will close all outdoor coasters), crowds will be light and the coasters intense.

Taken from:

ROLLER COASTERS by Scott Rutherford

Published in 2003 by Lowe & B. Hould Publishers

Previously published in 2000 by MBI Publishing Company.