Seth Goldstein acknowledges he’s prone to the occasional fit of “irrational exuberance,” to quote Alan Greenspan. Since the biomedical engineer retired in 2002 after 31 years at the National Institutes of Health, he has rerouted his creative energy to the art of kinetic sculptures.

His contraptions meet at the cross-section of childlike whimsy and technical wizardry, as gears, pulleys, innovation and inspiration coalesce into eccentric creations. One motorized sculpture, named the Why Knot, repeatedly fastens and unfastens a necktie. Another, billed as the Ro-Bow, uses computer programming and mechanical rods to play tunes on a violin. The suburban D.C. resident also created a piece called Cram Guy, in which a robotic man speed-reads Cliff’s Notes — his brain glowing red and pulsating — before he gives in to sleep deprivation.

Now, Goldstein, 80, has completed what he calls his “wackiest” work yet: the Rube Goldberg Exercise Bike, inspired by the iconic cartoonist and the fantastical gadgets he dreamed up. By pedaling the stationary bike, Goldstein triggers a chain reaction that causes the machine to scratch his back, fan him, pour him a mug of water and — if he really earns it — serve him a cookie.

Seth Goldstein

“The Why Knot and Ro-Bow, those are fundamentally great ideas — I mean, indisputable,” says Goldstein, who credits his wife, fellow former engineer Paula Stone, for conceiving those sculptures.

His latest work is entirely whimsical and fully his own. “A Rube Goldberg back-scratcher?” he says, chuckling. “This is questionable.”

Goldstein credits a childhood trip to a Hershey’s chocolate factory, where he was awed by the candy bar-wrapping machinery, with revving up his mechanical aptitude. By age 8, he had his heart set on attending MIT. Two decades later, he left the university with four engineering degrees. Since retiring from NIH, where he worked on devices for medical research and clinical use, his kinetic sculptures have been displayed at the American Visionary Art Museum in Baltimore and the Franklin Institute in Philadelphia.

“His whole lifetime, he’s had this passion for making things,” Stone says. “I just so admire him for that. He’s so lucky to have a passion, to have been supported in that, to have an aptitude for that, and he just loves doing it. It’s kind of wired into his system to make things.”

“If there’s some apocalyptic scenario, you want to be with a Seth Goldstein,” adds Rebecca Hoffberger, director of the American Visionary Art Museum. “He’s going to figure out stuff that nobody else ever thought about, just to solve problems.”

The Rube Goldberg Exercise Bike took Goldstein two years to complete, with plenty of stops and starts along the way. One detour came a year ago, when he underwent open-heart surgery to have an artificial valve replaced. But he accelerated work on the project after the pandemic sent him and his wife into isolation in mid-March.

“The pandemic was sort of weighing on me, and this gave me a good way to keep my mind off things,” Goldstein says. “I had to work on something that would be positive. Things are kind of dreary right now.”

Goldstein says the idea stemmed from a desire to “do something big” after he spent five years completing an intricate, six-foot wooden model of a Cutty Sark clipper ship that he built from scratch. He began the process when he came across a dilapidated exercise bike in his house, thought it would be nice to have his back scratched while riding it, and drew a detailed schematic.

With his ambitions set on constructing something “absolutely ridiculous,” Goldstein thought of more and more elements to pile on. He incorporated swinging cutouts of a dog eyeing a biscuit and a cat chasing a mouse, which were remnants from a previous project he had abandoned. And, though he did order some new pieces, the finished sculpture is largely recycled parts from his basement workshop, including a century-old hand drill.

“I’m not a hoarder,” Goldstein says, “but I don’t throw things away, either.”

As Goldstein details his creation, he exudes an endearing sense of humor and infectious enthusiasm for the art. He recalls spending upward of six hours a day working on the sculpture, navigating plenty of trial and error. Even landing on Keebler Sandies as the right cookie took time, after his preferred choice, Oreos, proved too fragile to survive the system intact.

“I mean, there were a lot of setbacks, and he has a good vocabulary of swear words,” Stone says with a laugh. “But underneath it all is this patience and this perseverance and a commitment to making something work. He just gets into the flow of it.”

All told, the device features five chains, six bands and 10 timing belts transferring motion throughout the system. Each cycle finishes with the deflation of a balloon, which releases a barrier blocking the cookie. The baked good then falls onto a turntable before a conveyor belt brings it to Goldstein. As long as he keeps pedaling, the process repeats.

“One of my principles when I make things is I want to have it be a cycle, so that the thing resets itself,” Goldstein says. “I like that feature.”

Goldstein isn’t sure if the Rube Goldberg Exercise Bike will find its way to a museum, like his previous sculptures. (“If the general public got on this exercise bike, they’d wreck it within a day,” he says.) But the public can see the contraption in all its labyrinthine glory on Goldstein’s YouTube page, where he has posted a video in which he rides the bike and explains its machinations.

Having recently purchased new supplies for his workshop, he’s already kicking around ideas for his next kinetic sculpture. In Goldstein’s head, the creative gears spin in cycles — just the way he likes it.

“If you have your creative work, you never feel age because you’re always engaged in something new,” Hoffberger says. “I really do believe that’s at the heart of who he is.”