Since the dawn of the Tour de France more than 100 years ago, virtually everything about bikes has changed. Except the spokes.
Now, three alumni of the UMN College of Science and Engineering have fashioned strong spokes from a flexible polyethylene polymer. Charlie Spanjers (chemical engineering ’10), Kyle Olson (electrical engineering ’10 and Ph.D. ’16), and Brad Guertin (mechanical engineering ’10 and M.S. ’14)—bike nerds all—began by tossing around ideas for reducing weight and making other improvements.
Eventually, they devised a braided polyethylene fiber with a threaded stainless steel rod inserted into the hollow cavity of the fiber. The threads of the rod connect to nipples within the rim. The technology is like a Chinese finger trap—the more it’s pulled, the tighter the connection gets.
In 2015 the three founded a company, Berd LLC, which touts its PolyLight spoke as “the lightest in the world.” Besides weighing less than half what metal spokes do, the flexible spokes dampen vibrations, making for a smoother ride.
Laypeople who assume flexible spokes are impossible have supplied lots of memorable comments, like “‘This is just vaporware! This product can’t exist!’” says Spanjers. But “if you bring a wheel, it’s a good way to convince them.”
Berd won the general division of the Minnesota Cup in 2016. In 2018 it received a $225,000 National Science Foundation grant because it had developed new manufacturing processes for polymer-to-metal connections, an innovation applicable to many domains beyond spokes. The company founders hope to expand into industries like sailing, automotive, or aerospace.
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