NuVinci continuously variable transmission

Nuvinci Cycling technology currently under development for other applications, including wind turbines, light electric vehicles, outdoor power equipment, and automotive front-end accessory drives.

[4] The NuVinci CVT gear system uses a set of rotating and tilting balls positioned between the input and output discs of a transmission.

The gear ratio is shifted by tilting the axles of the spheres in a continuous fashion, to provide different contact radii, which in turn drive input and output discs.

[5] The NuVinci CVT's simple design and low part count make it easily scalable, with tooling that can be used across a wide variety of applications.

However, unlike toroidal CVTs, it distributes the transmitted torque over several spheres, thus lowering total clamping force required.

As with other traction-type CVTs, transmission of torque through the NuVinci CVT involves some relative sliding between the torque-transmitting contact patches.

It is caused by the relative difference in surface speeds of both elements across the contact patch and is a major source of power loss in traction drive CVT’s.

"[9] In all traction-type CVTs, this relative sliding necessarily occurs between surfaces which are under the very high clamping pressures required to ensure torques are transmitted reliably.

[11] However, its geometry does differ significantly from the Kopp type of tilting ball variator in the reference in that the NuVinci has its torque transfer contacts on the outside diameter rather than the inside diameter, which puts the idler (an element that reacts clamping load) in compression rather than tension, and because the idler contact surface is not conformal as in the Kopp design.

Independent test results have shown that at 1:1 it is actually more efficient than comparable bicycle internal gear hubs, while at the ratio extremes it is slightly lower.

[14] That same article points out that "the combined weight of Shimano SLX front and rear derailleurs, shifters, freehub and cassette comes out to about 1.3 kg (2.9 lb)".

In 2007, The Ellsworth Ride received top honors in Popular Science magazine's annual Best of What's New review of significant new products.