I got a chance to chat with the guys at NuVinci at Sea Otter 2009. This hub has been out there for some time and is also being aimed at the powered vehicle market. The Nuvinci uses a series of large ball bearings to translate torque from an input ring of one radius to an output ring of another radius. As one radii increases, the other decreases, creating variable drive ratios. The contact surfaces are bathed in a rheopectic fluid which transmits torque under shear strain. The product does present a weight penalty to leg powered cyclers and seems like it may be better suited to hybrids, electric bicycles and other similar people moving machines.
The shifter features a very intuitive inchworm hill representation. Twist one way to make a hill for low gears, twist the other way for a flat line for high gears. Since the transmission is continuously variable, this is a very slick little shifter. I hope this makes it into all manner of entry level bikes as it really makes shifting intuitive for the non-cyclist.
The NuVinci hub was installed on a bike with a Carbon Drive Systems drivetrain. A unique look at the human powered drivetrain of the future?
The belt drive bike had a fantastic looking inlaid wood fender. Classy.
I also understand that someone was racing a NuVinci hubbed MTB at the Otter. Heavy.