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Left:Tony Ellsworth gives Donald Miller a lift atop The Ride, a cruiser with no fixed gears.
Recreation
DA VINCI’S new ride
Bike designers resurrect a 500-year-old idea to change the way people pedal
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In the late 1990s, Donald Miller was creating “unsafe and impractical” low-profile lie-atop prototype bicycles in his machine shop (that is, his garage). “I just wanted to build a more efficient bike,” says the San Diego cyclist and former realtor turned inventor. Eventually, Miller instead shifted his focus to the drive train, convinced that the traditional chain-and-gear system was the primary factor holding back the evolution of the two-wheeler.
Across town, bicycle designer Tony Ellsworth was coming to the same conclusion. “I knew we needed to move past derailleurs to make bikes more user-friendly,” says the founder and CEO of Ellsworth Handcrafted Bicycles, “but we didn’t have any better alternatives.”
Derailleurs shift poorly under load and can’t be shifted without pedaling. Worse, they offer a finite number of gear ratios. “Every human, like every engine, has a speed at which their power production is optimal,” Miller says. The more gears, the more likely a rider is to find that ideal speed under any condition.
Then Miller came across the continuously variable transmission (CVT), which has no fixed gears. Leonardo da Vinci envisioned the idea in a sketch from the 1490s, and it has been used sporadically since (in the Prius, for example). But no existing CVT could easily be shifted manually.
In 1999 Miller hit upon the elegant solution that would become his NuVinci transmission. Inside the rear hub are two rotating metal discs—one that receives power from your pedaling, and one that puts out power to turn the rear wheel. Between them, a set of rotating spheres is manipulated by the rider using a handgrip-mounted dial to change the angle at which the spheres meet the discs. So instead of stepping from gear to gear, the bike simply moves smoothly among infinite gear ratios.
Ellsworth saw an article in a local newspaper on Miller’s company, Fallbrook Technologies, and realized that the NuVinci was the solution he was looking for. “It takes the limits off how a bike designer can couple a human being with a bike,” he says.
Once Ellsworth convinced Fallbrook to work with him rather than rival Cannondale, he poured his considerable energy into designing a new bike around the NuVinci transmission. The hub is still too heavy for racing bikes, but its ease of use makes it perfect for casual bikes, such as The Ride. Twist the dial on this laid-back cruiser, and the gear ratio seamlessly increases or decreases to precisely the level you need.
Angelo Guido, a former Ford transmission engineer, believes the NuVinci design has further applications, including wind turbines, farm machinery and cars. “People have been thinking about this for a long time,” he says, “but this design has the simplicity, scalability and torque capacity” to finally deliver on the CVT’s 500-year-old promise.
—TOM CLYNES
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