Last week I was invited to tour the NuVinci design and testing headquarters in Austin, Texas. I was able to test ride a number of electric bikes and regular bikes with their new “Continuously Variable Planetary” (CVP) drivetrain. Below is an introduction to their technology and I will be following this article up with more articles on their latest projects and my visit to their headquarters.
It’s Time for Something NEW!
The bicycle drivetrain or “gears” on a bicycle have been the same old thing for quite a while. There is the typical derailleur system that shifts the chain from one chainring or cog to the next and there are the internally geared hubs that use a planetary gear system to change the gear ratios of a bicycle. There have been advancements in these technologies but they have basically polished the existing system to make relatively small improvements.
Now there is something NEW! It is the CVP drivetrain for bicycles that uses spheres and input and output rings to vary the “gear ratio” of a bike; all going on inside the rear hub. The continuously variable transmission (CVT) was actually conceptualized as early as 1490 by Leonardo da Vinci. NuVinci has refined his original idea into this CVP drivetrain for the bicycle. It is a new technology for bikes that presents some exciting advantages over the same old, same old.
If you want to learn more about the mechanics of the system, checkout the technical video here.
First of All; Forget About Gears!
What I mean is that with the NuVinci system there really are no “gears”, just infinite gear ratio possibilities between the low and high range of the system. A typical bicycle shifting system has specific gears that you will select. The NuVinci system allows you to select any gear ratio between the low (for hills) and high (for high speeds on flat areas).
The advantage to this is that sometimes you may find that on a traditional bicycle drivetrain one gear may be a little too difficult to pedal but the next gear may be too easy to pedal. With the NuVinci you can find that perfect gear ratio because it is “continuously variable” between the low and high gear ratios. NuVinci equates it to adjusting the volume on a stereo by turning the dial.
Shift Under Full Pedaling Power!
One of the real pains of the traditional derailleur and internally geared hubs has been shifting the gears under full power; i.e. when you are pedaling up a hill and you want to shift to an easier gear. Recent advancements in the traditional drivetrains have allowed shifting under almost full power, but not complete full power.
The NuVinci is different; it allows shifting the gear ratio under full power. I tried many different shifting scenarios when I was in Austin and I could always shift the bike under full power. If you are experienced with traditional shifting systems you will be amazed at how well this new system works.
Never Skip a Gear!
Traditional drivetrain systems (derailleur and internally geared hubs) are finicky in that they require proper cable tension to make sure they don’t skip or miss a gear.
Since the NuVinci is “continuously variable” between high and low there is no way to skip or miss a gear. In addition if the cable tension is not perfect, it is not as critical of an issue compared to traditional drivetrain systems. It just takes a little of the low or high range away from the system, not as bad as skipping a gear; that can hurt!
Low Maintenance! (or No Maintenance!)
Once the NuVinci hub is set up there is really nothing to worry about maintenance wise. According to NuVinci the oil (called a traction fluid) in the hub never has to be changed and all the other internal components of the hub will last the lifetime of the hub. Derailleur systems typically require adjustments here and there because they tend to fall out of adjustment over time. Typical internally geared hubs also require precise cable adjustment and they need to be regreased or have the oil changed on a regular basis.
Other Benefits of an Internally Geared Hub
I personally like internally geared hubs because they have no derailleurs to fuss with. They allow a straight and simple chain line and you can use a wider chain that can be more durable than some of the narrow chains used on a derailleur system. In fact there are now belt drives on the market that you will be able to use with the NuVinci CVP hub. Please note that using a belt drive would require that you have a front hub motor for an electric bike setup. Overall, internally geared hubs create a “clean”, simple and quiet drivetrain for a bicycle.
What is it Like to Ride?
Here is a video with Richard Cunningham (Mountain Bike Action editor) with his thoughts on the ride experience:
Okay, What About the Cons?
For the person that uses this system on their e-bike or traditional commuter bicycle the only con that I can think of is the cost of the system. It costs more than a low to mid range derailleur system but not a whole lot more. The lifecycle cost (initial cost, plus maintenance, plus lifetime of the product) is probably less because you will get more miles out of the NuVinci system compared to a typical derailleur system. The price of the NuVinci is similar to other internally geared hubs on the market.
For the rider who is an avid sport rider and/or racer looking for really high performance there are a few cons to the system. It weighs more than a typical derailleur drivetrain. And it is slightly less efficient than a typical derailleur drivetrain, though very comparable to other internally geared options. Again, those are concerns for the high performance oriented cyclist, not the person riding an electric bike or traditional commuter bike.
An Automatic Shifting System? Whoa!
That’s right, NuVinci allowed me to ride a bicycle with their “Developer Kit” installed, which is an electronically controlled automatic shifting system that will work perfectly with e-bikes! I rode a Panasonic e-bike with this system while in Austin and it is smooth! Stay tuned for future developments on auto-shifting technology from NuVinci 🙂
Do you have any questions or comments on the NuVinci CVP system? Do you have the hub on your bike? We (the Electric Bike Report community) would like to hear from you!
Please leave your comments or questions below.
P.S. Don’t forget to join the Electric Bike Report community for updates from the electric bike world, plus ebike riding and maintenance tips! (upper right hand corner of this site)