09.04Cable Dilemma – Electronicly Detecting Problems in Amusement Ride Cables
Whether its lifting a unit to the top of a tower, or catapulting a loaded train down the track in excess of 100 miles per hour, cables play an important role in the modern theme park attraction. With ride designers increasingly pushing the boundaries of acceleration, speed, and height, the stresses imposed upon a rides cables system is enormous. While accidents are rare, they do happen, and with devastating results.
Recent Notable Cable Faults on Modern Amusement Rides
- September 18th, 2009 – Knot’s Berry Farm “Accelerator” Roller Coaster
The cable become loose or broke sending debris into the riders faces, causing cuts and lacerations, as well as sending hot hydraulic fluid and steam onto the riders.
Source - Youtube video of the accident.
- June 21st, 2007 – Six Flags Kentucky Kingdom “Superman Tower of Power” Drop Tower
The cable internally failed, wrapping itself underneath the rapidly descending unit causing a 16 year old girls feet to be severed.
The are many types of cable failures, not all types can be visually detected.
Currently most manufacturers recommend at least a weekly or daily visual cable inspection, and a procedure known as a rag test. A rag test involves manually jogging the cable through the system while dragging a rag across it, if the rag gets caught on the cable, then the cable is damaged and must be replaced. Some parks choose to perform non-destructive testing annually, or submit core samples to a metallurgical laboratory for testing. While doing all of these things is a step towards insuring guest safety, it fails to take into account daily operational factors. When a cable begins to fail, its integrity begins to rapidly deteriorate, it can go from fair conditions to imminent failure in as little as a few hundred cycles. The variables of cable material, construction, drum speed, tension, and load will dictate during what cycle a failure will occur. Very seldom will a ride operator be able to visually or audibly detect a fault within a cable before it fails. Even if an attentive operator notices a problem, activating the rides emergency stop or power disconnect functions may not entirely prevent a cable from separating or striking ride units or guest.
Theme Park Innovations is working on a solution.
There is a significant and urgent need for a signaling device that can detect problems with a rides cable system. When combined with an adequate daily inspection and life cycle management program, both of the accidents above could have been prevented.