NuVinci Human-Powered Transmission
 

Has anyone heard of this transmission for bicycles? Continously Variable Planetary, does this sound like something that is revolutionary. Any "engineers" in the commuting forum?

The Nuvinci Website:

The NuVinci transmission uses a set of rotating and tilting balls positioned between the input and output components of a transmission that tilt to vary the speed of the transmission. Tilting the balls changes their contact diameters and varies the speed ratio. As a result, the NuVinci CVP offers seamless and continuous transition to any ratio within its range, thus maximizing overall powertrain efficiency, with no jarring or shocks from the shifting process, and improving acceleration, performance and overall vehicle efficiency over conventional transmissions.

Here an animated demo.

FAQ about bicycle use.

Data Sheet.

http://www.fallbrooktech.com/images/...t_th_500px.jpg

Sheldon Brown website:

http://www.sheldonbrown.com/gloss_i-k.html

The most widely known form of internal gearing is the three-speed utility bicycle. 4-and 5-speed hubs have also been available for many years, but went out of fashion during the early '70's bike boom. Shimano, Sram (formerly Sachs) and Sturmey-Archer have started marketing 7- and 8-speed hubs. Sram offers a 9-speed model, and Rohloff offers a 14 speed model. Fallbrook Technology's NuVinci hub is continuously variable, essentially offering an infinite number of "gears."

Not seen that before. Looks intriguing.
Here are two of the bikes that uses it.
$3k for the Al frame, $4k for the carbon.
I'd guess the hub is around $1k

http://homepage.mac.com/awcg/.Pictures/Bike/TheRide.gif

Ellsworth eh... sounds like they're aligning themselves about as far away from the "practical" and "value" market as possible.

No number for efficiency given there. The losses are likely to be associated with solidifying of the fluid and possibly any slipping in the area where the fluid is squeezed, particularly given rotational mismatch there.

Its gear range is 350% though so ya its great you can fine tune to any "gearing" you want but you're confined within a certain relatively narrow range. The Shimano 8 speed internals are 307% for reference and then 14 speed Rohloff is somewhere in the 500s

I find the idea cool but I have no personal qualms with how the current internally hub gears work. A 13% gear change is fine by me.

in order to get enough friction that the power would be transmitted without the balls slipping, the mechanism would have to be very accurately built, especially the seals for the "special fluiid" and probably be quite inefficient. it does not compare efficiency anywhere on the site.

continuous gear would be great if it could be as efficient as a normal drive train and not complex/expensive/heavy

CVTs have a reputation for inefficiency and for slippage. That's not a big problem in industrial equipment (I don't care of my 3hp Bridgeport milling machine motor delivers 2.8hp to the spindle due to losses in the cone-pulley CVT, after all) but it's obviously a big deal in a bicycle. With the balls, rings, and fluid, I also have to wonder how heavy it is.

It's a neat device, and if it really works as well as they imply it could be pretty cool. I'll wait until I see hard numbers for efficiency before I get too excited about it, though; the trade magazines are full of innovative, breakthrough mechanical products that somehow seem to consistently fail to live up to their advertising hype.

Here's an early (positive) review of the NuVinci transmission thingy in use. It's heavy, a whopping 4,2kgs.

http://phil.veloblog.ch/post/7/333

--J

Bicycle at the 2007 Handmade Bike show with the Nuvinci Hub.

http://gallery.mtbr.com/data/mtbr/981/DSC4188.JPG

Huh--I didn't believe the 4 kg weight until seeing that bike--wow!:eek:

Wow, I just read about this recently. For those wondering about the efficiency of the drive, the review that Juha pointed to lists the manufacturer's claimed efficiency at 97% and concluded that it's probably accurate.

4.2 kg is some serious weight though. :eek:

If they made it automatic then I'd buy it.

Given the light weight and high efficiency of a standard roller chain drive and the huge ratio count now available (up to 3x10, with perhaps 25 or 26 usable gears), I see no benefit whatsoever to a CVT for bikes. Give me a 5 or 6 percent ratiometric progression from the low 40s to the mid 90s (gear-inches), and I have everything I need. (In fact, I already have it!) CVT for bicycles is a solution in search of a problem.

Even though every car I have owned has had an automatic transmission (I haven't even driven a stick in almost 25 years), the concept of an automatic transmission for bicycles is completely unattractive to me. I want to know when it going to shift, I don't want to be caught by surprise, and I want to be able to vary my cadence as desired.

The only new bicycle transmission technology which intrigues me is the manually controlled electromechanical derailleur set, which I think both Shimano and Campagnolo, and perhaps SRAM as well, have prototyped. The benefits would be automatic trimming of the front cage and multiple locations for gear controls, such as on the drops and on the brake hoods.

+1, except, we should probably recognize that this project's purpose is just to explore technology, not to reach the mass market.

Have you heard this from the designer?

Seems contrary to most successful business models.

You're right, I don't know this first hand. The reason I wrote that is that from a price and weight (and function) standpoint, it categorically can't be intended for any large market, unless you consider super high-end quirky gear to be a large market, which it might be, but it's not mainstream. Very few bikes will have this.

You're last statement is exactly the reason why I find the CVT attractive. If it's shifting continuously then there are no jumps. Nothing to catch you by surprise. You just keep applying the same effort to the pedals and the bike adjusts its speed accordingly.

And I'm sure an adjustment could be added to change the parameter of the automatic transmission so you could vary your cadence. The important thing is that you'd only have to vary it when you want to change cadence, not because the terrain changed.

That's an amazingly good efficiency. I tend to take manufacturers' ratings with a large grain of salt, but if they're claiming 97% it's got to be pretty decent in any case. If you can get past the weight it's a pretty neat setup.

I'd love so see something like that with an automatic control - rather than the twist grip selecting the drive ratio, let the twist grip control the cadence. If you start spinning too fast it'll lower the ratio to keep your cadence in the target zone, and if you start spinning too slow it'll raise it. If you want to adjust your cadence you just have to twist the grip.

It's probably still not something I'd buy - I love hearing the derailleur snick back and forth when I change gears. :)

"I want to know when it going to shift, I don't want to be caught by surprise, and I want to be able to vary my cadence as desired."

Better re-read their web page. You do control the "pitch".

"You’ll find yourself shifting without thought, whenever you feel like it - while you’re pedaling, when you’re coasting (freewheeling), when you’re pedaling backwards, even when you’re stopped. There’s no hesitation, no noise, no waiting for the mechanism to “hunt” for the gear you’ve selected, nothing to synchronize, nothing to guess at, a simple twist of your wrist and you’re at a new ratio."

:lol:

NuVinci is going to stay
 

Seems like NuVinci is a hit. In bicycle-country no. 1 (The Netherlands) one of the leading bike manufacturers (Batavus) introduced three models with the NuVinci hub. One of these models won the Dutch bike innovation award and is Dutch bike of the year. These bikes sell like hot cakes.

I'm sure next year more manufacturers will follow.

I just took a look at the home page you listed in your User Profile. Is there a connection between you and the NuVinci manufacturer?

No, not at all. The only connection is: I own one of these bikes and love it. Sorry the site only is in Dutch.

The site is set up to gather user reviews of the hub with pros but also with cons.

OK, sorry I missed the disclaimer at the bottom of your web site.

--J

And that's Ellsworth for you.