Fallbrook Technologies released the NuVinci Continuously Variable Planetary (CVP) N170 transmission for bicycles in 2007. The rear hub-based system does away with distinct, defined gears, it's sealed against dirt and other contaminants (unlike a derailleur), and it allows riders to change drive transmission ratios even when standing still. Last year, the company unveiled the NuVinci N360, which is smaller and lighter than the N170, yet has a wider range of ratios. Fallbrook has now announced yet another incarnation of the technology - the NuVinci Harmony - which is an auto-shifting version of the N360 aimed specifically at e-bikes.

The Harmony, which is intended for use with 12-48 volt e-bike systems, automatically adjusts the drive ratio in order to maintain the cyclist's preferred pedaling cadence. If you're going up a hill, for instance, it will shift into a lower ratio, so that it's no more difficult to turn the pedals than it was on the flats.

There are two handlebar-mounted controllers available for the system. The Base Controller simply allows riders to chose between three speeds of automatically-maintained cadence, with the push of a button. These will be preset by the e-bike manufacturer itself, as dictated by the gearing and other parameters of the bike. Typically, however, the cadence choices would consist of fast, medium and slow.

On the Advanced Controller, users can find the exact cadence that they prefer, then instruct the system to maintain it. Should they wish, they can also switch over to manual mode, and adjust the ratio themselves.

The hub interface itself weighs 250 grams (8.82 oz), and has a quick-release attachment for easy wheel removal.

Fallbrook Technologies' NuVinci Harmony CVP should start appearing on e-bikes in the EUR 2,000 (US$2,864) and up price range, starting early next year.