Become a
Pinball Wizard


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Become a Pinball Wizard - Design

How many kids spent time playing pinball when they should have been hitting the books and thinking about their future? Well, for John Rotharmel, playing pinball was the future. Today, he is the mechanical engineering manager for Stern Pinball, Melrose Park, IL, constantly figuring out how to make a game invented in the 1940s (earlier if you count pre-flipper) perform at its best. And they're clearly doing a decent job, as their "Rolling Stones" game recently had this writer on good terms with the change machine in search of the all-important high score during a recent test drive at a local arcade.

Become a Pinball Wizard - Design

Detail of the Rolling Stones pinball game. Image: Stern Pinball

But the overall theme and visuals of pinball are not where Rotharmel comes in—that's the game designer. It's in the ball action and the mechanisms that create the right combination of speed where an engineer can be worth his weight in Chuck E. Cheese tokens. "It's about being familiar with coil-driven mechanisms," he says. "With motor-driven machines, it's straightforward because there aren't any torques that are required but with coils, the data is empirical so a little more testing has to be done. You also need to understand how electromagnets work and what you can work with at various force levels without overstraining the electrical system." But it's also a feel for the material. Sheet metal linkages, Rotharmel estimates, make up 60–70% of game parts.

The engineer's role in the machine's creation begins with the game designer's vision and then assessment by Rotharmel and the two mechanical engineers under him. "For the coil aspect, it's driven by a return spring and there are different ways to achieve this," Rotharmel says. "The game designer will tell us what kind of pinball action they're looking for. They'll say, 'I want this to be a violent bounce' or 'This should be a soft rebound,' and we decide whether it's a coil-driven kicker or a spring-loaded device that will give you the right kind of bounce."

But it also comes down to money. It's up to the engineer to give the designer hints as to when it's going over budget. "The designer will communicate based on that, 'OK, this isn't important, but I've really got to have this for the game to be what I want it to be.'"

Become a Pinball Wizard - Design

Finite element analysis is used for testing the pinball game design.

And, again, testing is a huge part of the success. "We do finite element analysis," he says. "But we also have great software and perform a lot of stress analysis and want to feel good that the game won't break in a period of two to three years."

Also, as you might have guessed, it's a job requirement for Rotharmel to repeatedly play the game. "We're doing that throughout the process, making sure ball path and smoothness are as good as they can be," he says.

When I start to ask how they know the machine is finished, Rotharmel has an answer even before I've finished the question. "Never!" he says. "If a designer could work on a game forever, they would. That's why we're even playing the game as it's ready to be shipped, still evaluating, still making final minor adjustments…And, we're having a lot of fun!"

Several dollars and a high score later, I can attest to it.

Eric Butterman is an independent writer.

If a designer could work on a game forever, they would. That's why we're even playing the game as it's ready to be shipped, still evaluating, still making final minor adjustments.

John Rotharmel, mechanical engineering manager, Stern Pinball

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July 2012

by Eric Butterman, ASME.org