Guest Opinion

Don’t freak out about Freak Out
By: 

Wendy Goerl, Special to the Leader

The KMG Fireball (a.k.a. Afterburner) had a catastrophic breakdown at the opening day of the Ohio State Fair. The simple answer to “What happened?” is a sweep arm (or something in the junction between the seats and the sweep arm) broke.

In response, Fireballs (and Move-It/Spin Out, a related ride with the same gondola arrangement) worldwide have been shut down until KMG and accident investigators figure out exactly what happened.

Several fairs that have contracted carnival companies using the Freak Out (Fireball’s “little brother”) have decided not to allow the operation of Freak Outs, either.

For someone with a grade-school education and a conviction that all catastrophic failures can be prevented with enough qualified inspections, this seems to be a sensible precaution.

For anyone with the most basic understanding of the physics of mechanics and strength of materials, it’s like banning oranges because you discovered a worm in an apple.

Freak Out and Fireball can both be described as groupings (six for Fireball, four for Freak Out) of four seats attached to a gondola that rotates at the end of a long arm that swings through around 240 degrees of arc. There’s a significant difference in the nature of the gondola. In the Fire Ball, the sweep arms (which connect the seats to the swing arm) are essentially cantilever beams.

If you’re in building construction, you know what a cantilever is. If you’ve visited the Infinity Room of House on the Rock in Spring Green, you’ve stood on a cantilever. If neither of those gives you any perspective, think about trying to loosen a bolt. Fingers don’t work too well if the bolt is tight. So you get a wrench. If that doesn’t work, you get a longer wrench.You push down on one end of the wrench, and the other end exerts a moment (turning force) on the nut. The wrench is working like a cantilever.

The sweep arms on the Fireball are like the wrench: the nut is the hub of the gondola, the sweep arm is the wrench, and the seats are your hand—tugging on the “wrench” with every swing. Observers watching the Fireball will tell you that in full swing, the sweep arms are flexing with the strain of the G-forces every swing.

This stress can eventually fatigue the metal in the sweep arm, creating cracks that will eventually become breaks. The problem is that by the time these cracks are large enough to see with the naked eye — or even a loupe — the metal’s probably already broken. General inspections will not reveal them, no matter how competent the inspector.

The only way to detect these cracks before they become a threat to ride safety is with non-destructive testing, which — depending on what exactly is being tested — can include ultrasound, X-rays, magnetic particle testing, neutrons, terahertz radiation, among other methods.

The Freak Out is the same thing, isn’t it?

Uh, no. In the Freak Out, the sweep arms are not cantilevered. They actually attach at an angle — only about half of the distance from the fulcrum of the swing arm to the seats is actually the swing arm, the rest of the distance is sweep arms. When the arm is swinging, the sweep arms will want to push in toward each other, a force that is resisted by spreader bars set between the arms. This puts much less stress (closer to the fulcrum equals less force) — and therefore less chance of structural failure — on the sweep arms.

One more difference between Fireball and Freak Out: The frames of both rides are part of a single trailer (the Fireball requires an “auxiliary” trailer for the other parts, the Freak Out does not), meaning there’s a rather substantial amount of structural steel on each end of the trailer. Fireball swings parallel to the trailer, so if a seat grouping falls off, it slams into that massive steel. Freak Out swings perpendicular to the trailer, so a loose seat grouping would be able to skid to a stop away from the ride (assuming there’s nothing massive near the ride), meaning the Freak Out is slightly less dangerous in the case that there actually is a seat detachment.

Wendy Goerl, of Shawano, is a 1998 graduate of the Milwaukee School of Engineering.