http://www.core77.com/blog/object_culture/invention_da_vinci_5810.asp

no more chain
follow the links for more info.
What are people saying about hubs with NuVinci technology?

Reaction to the NuVinci CVP hub has been nothing short of phenomenal. Bicycle industry executives and consumers alike are quoted as saying:

?Smooth?, ?very smooth? ?very smooth, unbelievable?, ?silky?
?It?s so easy to shift and maintain a perfect cadence.?
?Takes the worry out of shifting?
?I haven?t missed riding a bike until now"
?It is the best transmission on a bicycle?
?I have seen nothing like it?
?[this] technology is a great fit?.?
?The ride quality is ready now!?
?I want it now!?

I find this fascinating, don't get how it works mechanically a 100%, but very interesting none the less. It would appear this transforms your traditional geared bike into a single speed essentially (chain & gear wise) while maintaining all the benefits of a geared bike. You still have to transfer your effort from the crank to the hub somehow (i.e. chain or drive shaft) and if you want a bike with rear suspension, there would be some kind of chain tensioner required to take up the slack created by the suspension movement.

Maybe some of you mechanical wizards out there can explain this better but my take on it is, unlike a regular geared bicycle where the drive train is always fixed meaning aside from the actual shifting process there is always a solid connection between the crank and the wheel rotation while pedaling. With the NuVinci technology, however, there is never a fixed connection between the crank and wheel, there is always mechanical slippage between the input and output (i.e. crank and wheel). It is the adjustment of this slippage that simulates traditional gearing / effort required to turn the wheel. Major difference being the NuVinci system allows for infinite in between ratios to be achieved between a fixed high (i.e. 34 tooth) and low (i.e. 11 tooth) ratio while achieving ultimately smooth "shifting" across the range. In theory, at least, this is similar to how an automatic transmission in a car works.

In summary this is really cool stuff. It definitely has to capability to radically change the biking industry. It will be interesting to see where this technology goes. Hopefully the roll out will be faster than the development phase considering Leonardo Da Vinci came up with this idea in 1400's and it's just being implemented now, in bikes at least.

Here are the links to the manufacturer's website demo movie on the NuVinci hub:

High Speed QuickTime: [url]http://www.fallbrooktech.com/02_Demo.asp#[/url]
High Speed Windows Media Player: [url]http://www.fallbrooktech.com/video/cvp2-lg.wmv[/url]

Dial up Quicktime: [url]http://www.fallbrooktech.com/02_Demo.asp#[/url]
Dial up Windows Media Player: [url]http://www.fallbrooktech.com/video/cvp2-sm.wmv[/url]