Summer’s here and it’s time to get back on the bike. We could have looked at a fancy new ultralight, but the NuVinci is the bike that’s really going to shake things up. It answers a question you may not have thought to ask: what if you could pick up a new ride with a transmission that made sure you’ll never be in the wrong gear?
A NuVinci bike effectively has an infinite number of gears. You can adjust it smoothly, without worrying about clicking into gears, to provide the precise right amount of resistance. You can start at a very low gear to pedal easily and then smoothly ramp up to a higher gear as you gain speed. And since everything is internal, repairs are rarely necessary. It’s a revolution, really–one of the most fundamental changes to the bicycle in decades.
On a regular bicycle, the input force comes from your legs, turning the pedals, which in turn spin the chainring — the big toothed gear up front. A chain carries that force to the cogs connected to the hub in back, which in turn turns the rear wheel; the ratio between the number of teeth on the chainring and the number of teeth on the current cog determines what gear you’re in. A “high” gear turns a big ring up front and a small cog in back–hard to pedal, but a lot of movement from each revolution. Reverse it and you get a “low” gear–easy to pedal, but not much movement.
But more often than not, there is no right gear for a given situation — fourth gear is too low, fifth too high, say. So why not do away with those pesky steps altogether? A continuously variable system does just that.
via Popular Science
