This article focuses on a new amusement ride that blends several control systems by combining spinning-coaster thrills with interactive special effects. The Exterminator at Kennywood Amusement Park combines a ‘wild mouse’ coaster with the interactivity of a dark ride. ‘Dark ride’ is amusement maker parlance for fun house style frights that pop into view unexpectedly. A proximity sensor, positioned after the coaster and animation went in, begins the action sequence for this figure just as the riders come upon it. Bringing the Exterminator up to speed was a matter of controlling the coaster, controlling the animation, and controlling the interaction between the two independent systems. A process of trial and error, determining the right moment to start an event occurs only after the animation is in place and the carts are riding the rails. A double pneumatic fin brake below the track slows carts as needed before they enter the boiler.



ALONG A SECTION OF the Exterminator at Ken- nywood Amusement Park, riders in cars roll toward what park electrical director Bill Mar- venko calls the “infinite track mirror trick.” The track looks as though it’s been gnawed away by giant rats, which are loose in a subterranean utility space, chewing their way out. A mirror perched trackside reflects the scene of devastation back to the riders; the real track remains safely intact beneath the cart.

Along another section, riders brace as fire and smoke from an industrial boiler threaten to consume them. The effect is done partly with a fog machine.

What brings the ride to life is not smoke and mirrors at all, but the careful orchestration of a myriad of inputs and outputs by control systems behind the scenes. A combination of programmable logic controllers, sound and automation controllers, and logic modules supervises everything from directing the descent of the coaster carts, to animating the figures and special effects, to initiating animation sequences.


According to Marvenko, the Exterminator started op- eratirag last year at the amusement park in West Mifflin, Pa., near Pittsburgh. As with any large-scale construction project, building the ride took the efforts of several major and minor contributors. Even more than on most projects, though, a great many finishing touches had to wait to adorn the ride until the coaster and the animation modules were bolted down.

Once Kennywood decided to introduce the new ride, it brought in R&R Creative Amusement Designs of Anaheim, Calif., to create a theme, look, and story. Although no two amusement rides are alike, many share common elements from different suppliers. In the case of the Exterminator, French manufacturer Reverchon of Paris would supply the roller coaster that eventually would take riders along the dark underground passages of the utility tunnel.

Today, however, audiences depend on more than just roller coasters for their thrills. So Kennywood planned the ride around a runaway-rat theme. For the animation, Kennywood brought in Jacksonville-based Sally Corp.

The Exterminator combines a “wild mouse” coaster with the interactivity of a dark ride, said Sally Corp.’s CEO, John Wood. The old wild mouse ride was always popular, but it has recently undergone a resurgence in ridership. The typical wild mouse coaster sends four passengers in a single car through a series of hairpins and drops. “The hairpin turn is really where it got its history,” Wood said. “The ride looks innocuous. It looks like it would just be fun.” Because the carts use offset turning wheels, the wild mouse “gives you the feeling at every turn that you’re going to go off the edge,” Wood said. “You go straight and the turning wheel is back about 18 inches. When you make that turn, there’s no railing or anything around you. You’re asking, ‘What’s keeping me up?’ “ As if that’s not enough, the Exterminator dropped a box over the wild mouse, Wood said, putting the whole thing in the dark.

“Dark ride” is amusement- maker parlance for funhouse- style frights that pop into view unexpectedly. Wood said that such rides, which his company specializes in building, are quite sophisticated in terms of the audience participation level they can attain.

“Our evolution of the dark ride has incorporated a game component into the ride experience. Riders go on a quest,” Wood said, “and in order to participate in the quest they shoot at targets with flashlights or laser guns or zappers. Riders are scored as they go, either collectively or individually.”

The Exterminator does not strive for that level of audience participation. With the coaster and the animation, it doesn’t need to. There’s already plenty going on. But Wood said that the sophistication of today’s controls demonstrates how technology is advancing the industry.

A Ride On The Wild Side

According to Marvenko, a trip aboard the Exterminator goes something like this: Before loading, riders form a line along a queue-up ramp. They walk up and through a control room replete with a television anchor announcing a city takeover by rats. Almost a thousand lights blink randomly at the panel. Along the walls of the 28-foot building hang maps depicting West Mifflin’s utility underground. The effects sequence repeats at intervals of about 20 minutes, Marvenko said.

After riders enter the loading station, which extends along the coaster track for about 50 feet, they climb into cars by groups of four. The roller coaster uses seven independent cars in all. The load station, serving as a portal to the underworld, plays up this effect with roots overhead, red lighting (for the sake of safety), and, down-track, where the cars enter the tunnel, a giant, slow-moving exhaust fan powered by a small motor.

Once loaded, the cart makes its one and only powered climb to the top of the first hill. From there, the cart will freewheel, with only brakes controlling its descent.

The first scene is the electric room, where the 10,000- pound shell of an Alstom circuit breaker (for which Ken- nywood paid $30,000) shows sure signs of trouble. Electric arcs, the result of a digital video image projecting onto scrim, bounce among the breaker’s three giant electrodes. Frayed cables hang helter-skelter, obviously the work of furry Luddites.

The cart then descends, climbs, rounds a bend, and comes upon a giant rat arm, Marvenko said. The arm lowers in front of the oncoming cart, surely ready to sweep it off the track. At the last moment, the track falls away and the occupants slip beneath the rat’s surly grasp.

In the next scene, an animated exterminator in orange coveralls stands ready to fire a gun loaded with what passengers know can only be high-strength rat poison. This is also where the track disappears in the mirror trick.


The cart speeds on to a darkened room. As it starts negotiating the serpentine section of track, a patented locking mechanism releases the cart body from the chassis. Up until this time, the cart body has been locked to the rolling chassis to ensure safe passage through the upper drops. Now free to spin, the cart body and its four occupants begin winding one way or another while the chassis chases the hairpins. A rotation cam between body and chassis controls spin speed, but each trip through is different because the direction of spin can reverse and its rotational rate depends on whether the cart holds four portlies or three slims. Still spinning, cart and passengers enter the maw of the boiler.

Alive after escaping the fire and smoke of the boiler, the passengers continue spinning as they ride over a series of camelbacks—small hills—that dissipate the coasters energy before it returns to the loading area.

Three-Part Control

Bringing the Exterminator up to speed was a matter of controlling the coaster, controlling the animation, and controlling the interaction between the two independent systems, Marvenko said.

Unlike the animation, which Sally Corp. built in accordance with R&R’s original custom design, the coaster duplicates a prototype ride that Reverchon first made in 1986, of which 35 copies have since been sold.

According to Vincent Pic Paris, Rever- chon’s U.S. representative in Jupiter, Fla., the company makes its spinning coaster in only one version. The same version can be carted from fair to fair as a portable ride or fixed in place to act alone or, in Kennywood’s case, as the core around which other amusements such as dark rides are built.

“The track is not modular,” Pic Paris said, “and we are trying to keep it as is. Any modification of the track represents a huge amount of engineering hours.” Standardizing the track helps Reverchon meet the conformity assessments of such organizations as Bureau Veritas of Courbevoie, France, and TUV Suddeutschland of Munich, which test and control the integrity of both systems and welds, he said.

Standardization holds true for controls, too, at least in how Reverchon engineers address them. “The controls approach is the same for all the spinning coasters we have manufactured and delivered,” he said, although specific components of the system have changed over the years as manufacturers have introduced new products.

The coaster uses a blocking system to keep successive carts spaced safely apart, Pic Paris said. A series of proximity sensors set at intervals along the track sense cart presence, reporting back to a Siemens PLC. The sensors divide the track into zones. By detecting the presence of the cars as they enter the zones, the PLC knows the approximate whereabouts of as many as six cars at once.


Nine double pneumatic fin brakes are distributed around the track circuit, one for every zone, he said. At each location, two lengths of angle, each 2 meters long, back up against air bladders. Actuated by air pressure following a PLC signal, the angles force opposing strips of brass toward each other. The soft metal provides wear surfaces that rub along the sides of corresponding metal fins projecting from the cart undersides.

The coaster PLC keeps all the active carts under surveillance. If a cart starts gaining on the one ahead of it, the PLC claps the appropriate fin brake to slow it, he said. If a cart does not pass a sensor within a certain period of time, the PLC assumes it is dead on the tracks and stops the car trailing it. The sequence repeats until all active carts are safely stilled.

Although many amusement rides use PLCs by other manufacturers, Reverchon elected to use a Siemens controller partly because of its ability to meet Cen- elec (the European Committee for Electrotechnical Standardization) Level 4 safety directives, he said. “The ride is fitted with two computers that check each other,” he added.

Unlike the controls for the coaster, the animation aspects of the ride—the rat arm motion, the exterminators, the smoky boiler room—require that the action sequence be synchronized to an audio track. “Typically, we won’t do much with PLCs,” said Sally Corp.’s Wood. For anima- tronics, synchronizing audio and action is the primary task. “PLCs are obviously a scripted technique, programming a series of activities that take place one after the other, sometimes related to time, but not always,” Wood said.

“Time synchronization is critical when it comes to moving a mouth at the right sequence, or having characters appear more lifelike,” Wood said. Sally Corp. programmers code mostly by way of a clock track or by way of analog FSK (frequency shift keying), in which a signal is encoded or decoded on a separate track of the disk, tape, or digital chip, and synchronized with the audio program.

“When you are sitting there trying to manipulate what is, in essence, an electronic puppet, then you’ve got to play the soundtrack on one hand, while you’re manipulating the character on the other, and putting all that information on some storage vehicle,” Wood said.

The success of a ride like the Exterminator depends greatly on putting the audience in the scene, Wood explained. Action is directed at the riders as carts swing by individual animations.

“We want the action to appear as though it’s happening because of the rider’s presence. We’re shooting fog on people, in the case of the Exterminator, which adds to the sensation of the experience,” Wood said.

“We have developed some techniques that allow for localized, solid-state control, as opposed to a centralized scheme,” he said.

“We have little control boxes that house what we call a mini-SAM—or sound and automation controller—and on that card there is the ability to store up to four minutes of audio.” The card holds a small amplifier as well, along with an animation controller. A sensor, detecting a cart, starts the show and the sequence, he said. The Exterminator consists of a number of short shows in the middle of one big show, he added.


Any of the rides that Sally Corp. has worked on could have used central control. It’s more a matter of the individual park operator’s tastes, Wood said. Local control assists troubleshooting because walkie-talkies or video monitors are unnecessary. On the other hand, “some operators like to tour people through their control Mecca.” For them, central control is the way to go. “Disney is certainly one of those,” he said.

The ride designers originally planned on triggering the animation sequences from photocells that detected the passing carts, Mar- venko said. But the park had tried photocells previously, he said, with limited success because dirt and dust would debilitate them. Using them in the dark of the new ride was questionable as well.


The designers decided instead to use proximity sensors. These could have been wired directly into the individual animation controllers, Marvenko said. That approach, however, would make it difficult to locate the sensors to fire the effects at the right times. A process of trial and error, determining the right moment to start an event occurs only after the animation is in place and the carts are riding the rails, he said. “We didn’t know how fast the cars would move. At the beginning of the ride they go slow and in some places they go fast. If I were to put a photocell 50 feet away from the trick, it might trigger at the wrong time. I might be playing with that forever,” he said.


The trial-and-error process ended up adding sensors that were beyond the capabilities of the original controllers, Marvenko said. The designers considered several ways of accommodating the extra controls inputs.

One way was to simply go to a larger master controller. Another way was to use several micro-PLCs. A third way, suggested by a salesman at Scott Electric of Greensburg, Pa., which supplied the original controls, was to use five logic modules from Siemens. Logic modules offered I/O for less cost than did the other approaches.

Hey, Dummy, Move Your Arm

A long time passed between the stirrings of the big idea and the final sequencing of animation, the last nailing down of scenery, and the first welcoming aboard of a paying thrillseeker. Along the way, however, the artistic themes that initiated the project never strayed far from center. Themed-adventure designers Richard Bastrup and Richard Fer- rin, who own R&R, were among the first people Kennywood approached with its idea for the Exterminator. They are usually among the last to sign off on a ride as well. After developing initial concepts for the Exterminator, R&R designed art, logos, and characters, then produced all the audio and video elements.

“We call ourselves art directors,” Bastrup said. “We work closely with the project architect and all the manufacturers,” he said.

Project timelines in the industry run from 7 to 18 months, with a year being most common, Bastrup said. Designing themed adventures is very much a specialty business, he said. Where possible, R&R confines the bidding on animation and effects to just a few companies.

Construction of the amusements is stratified, too. “As small as the business is, there are people who specialize in bigger animation and those who concentrate on smaller stuff,” he said. “But there is no standard to bid against as there is in laying concrete, for instance.”

R&R is very much aware of what is technically feasible when it sets about to design a ride. But technical details are left to the animatronics makers. Take the exterminator figures, for example.

“The designers created the location and the approximate poses of the figures,” said Sally Corp.’s Wood. “We then translated that into life-size drawings of those poses.”

From the drawings, Sally Corp. engineers created frames of stainless steel because the figures would feel fog. Then the engineers encapsulate the frames in vacuum-formed plastic, Wood said. “Inside this body form are the actuators that turn a head, tilt a head, move a mouth, move an arm,” he said. For most animation, Sally Corp. uses pneumatic actuation because it is cleaner than hydraulics and less costly than motors.

“The animation schedule is typically dictated by the show action required-what’s the most realistic action that we should be able to get for the budget. We then use industrially rated techniques activated by digital or analog signals,” Wood said.


Still, for all the technology that ride-builders have available today, Wood relies on a simpler equation.

“Technology does not typically drive the amusement park field; it complements it,” he said. “Fun and entertainment drive the amusement park. People don’t care whether you have cams and cogs for moving your animation or sophisticated controls—as long as it’s fun.”