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  1. #1
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    New Type of CVT for Bike Hubs - NuVinci

    Is this some new competition for the Rohloff?

    NuVinci™ Overview

    The patented NuVinci technology developed by Fallbrook Technologies Inc. (Fallbrook) is the most practical, economical and universally adaptable continuously variable planetary (CVP) transmission for human-powered and motor-powered vehicles and machines. The NuVinci CVP is ideally suited for applications in many major industries including bicycles, light electric vehicles, tractors, automobiles, trucks, and utility class wind turbines among others.

    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 improves acceleration, performance and efficiency over conventional transmissions. 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.



    When compared to traditional continuously variable transmissions (CVTs), the NuVinci CVP is less complex, has considerably fewer parts, offers more stable control, is easier to shift, offers more scalability across product lines, is better packaged, and is less expensive to manufacture and assemble.

    Distinguishing the NuVinci CVP from Traditional CVTs.

    There is a clear distinction between Fallbrook’s NuVinci continuously variable planetary drive (CVP) and more traditional continuously variable transmission (CVT) technologies.

    A CVT is a transmission that is infinitely variable between its high and low range as opposed to a conventional geared transmission where the number of speed ratios between high and low is limited by the number of gears.

    The CVT has been called the “holy grail” of transmissions because it eliminates the multiple gears, shifting clutch and many other parts found in conventional transmissions. In place of gears, most CVTs use one or more cones, discs, balls, toroids or other alternative shifting devices. These geometric shapes allow the contact points on the shifting device to vary in diameter, thus changing the input to output speed.

    The use of CVTs has not become widespread due to multiple problems inherent in traditional designs. These problems include shifting control difficulties, poor efficiency, scalability challenges, questionable reliability and durability, high cost, and other factors.

    The NuVinci CVP represents a quantum leap forward over traditional CVTs as well as conventional mechanical transmissions. These advantages include:

    Higher torque density
    Smaller size/weight
    Easily scalable
    Simpler
    More adaptable and versatile
    Improved overall performance
    Easy to package (less space required)
    Lower manufacturing and maintenance costs

    How the NuVinci Transmission Works

    The NuVinci CVP is continuously variable and infinitely applicable to almost any product using mechanical power transmission. NuVinci technology combines the advantages of a toroidal traction CVT with the time-proven versatility of the planetary gear arrangement. It uses rolling traction to transfer torque, just as toroidal transmissions do. However, unlike toroidal CVTs, it distributes the transmitted torque over several spheres in an inherently stable configuration, thus lowering contact pressures and significantly improving durability, control stability, and torque density.

    This arrangement makes the NuVinci transmission the only practical CVT to combine the smooth, continuous power transfer of a CVT with the utility of a conventional planetary gear drive. Torque inputs can be summed or divided, just as in a conventional planetary. Ratio control is stable, and can be actuated down the center line of the transmission, again similar to the proven planetary transmission. Part shapes are simple and easy to manufacture. And in most applications, there is no need for power-robbing, high-pressure hydraulics.

    The NuVinci CVP reduces fuel and/or energy consumption due to its high efficiency and seamless speed changing characteristics, allowing the power input such as an engine to operate in its most efficient speed range. Overall, the NuVinci CVP’s mechanical and manufacturing efficiency improves performance and reliability while reducing costs over conventional CVTs and stepped transmissions.

    As a result, the NuVinci CVP can potentially replace the planetary gear automatic transmission in most mechanical devices.


    Key advantages of the NuVinci CVP

    Compared to conventional transmission technologies, the NuVinci CVP provides:

    Less complexity. There are significantly fewer parts than conventional transmissions and it is much less costly to manufacture.
    Overall improved system efficiency. With the NuVinci CVP, it is easy to keep an engine running at its most efficient speed.
    Greater acceleration and optimum performance. Acceleration is faster and smoother – right up to the vehicle’s acceleration limits – because it keeps the engine running at peak performance.
    Easier shifting. There is no jarring associated with shifting gears.
    Ability to accept multiple inputs while varying speed and ratio, managing torque and providing multiple power outlets. A NuVinci transmission is the most practical CVT technology to perform all of these tasks simultaneously.
    Support for a torque demand rather than a speed demand control solution. The NuVinci CVP solves the low-speed acceleration problem inherent in some torque-demand vehicles.
    Scalability and potential to reuse tooling. The technology is highly scalable. The design and implementation of a low-torque application utilizing four balls may involve the same basic parts as a higher torque application with eight or sixteen balls. Also, tooling can be used across a wide variety of applications.


    Compared to CVT alternatives, the NuVinci CVP offers:

    Coaxial input and output. The input and output shafts are in-line, making the transmission simpler, smaller, easier to package, and lighter.
    Better torque density. A NuVinci CVP delivers a large amount of torque in a small space. It is smaller and easier to package than CVTs because it does not require an offset shaft and because it can spread torque across any number of balls.
    Lower manufacturing cost. The transmission uses simple geometry and very simple parts which results in a lower cost. The NuVinci CVP can also be scaled across a wide variety of vehicles in many cases without retooling.
    Lower control cost. Transmission control is stable, linear and does not require a major control system development effort.
    Power path variability. The technology is easily integrated into a wide range of applications with varying power path requirements or options.
    Scalability. The NuVinci CVP’s simple design and low part count make it easily scalable.


    Technology Applications for NuVinci technology

    While the NuVinci CVP has application potential in virtually any mechanical device requiring speed variation,. Fallbrook has initially identified six major industries for licensing of NuVinci technology:

    Bicycles
    Light electric vehicles (LEVs)
    Automobiles
    All-terrain vehicles (ATVs)
    Agricultural equipment
    Wind energy

    Fallbrook selected these initial industries because they offer:

    High potential for early adoption by manufacturers
    Large market size
    Potential rapid time-to-market
    Companies seeking a competitive advantage through improved technology

  2. #2
    mmm, carbon
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    I think this has a relatively small available gear range -- in the order of 300% IIRC. In principle it's great, but not versatile enough compared to a Rohloff. Maybe good for the downhillers?

  3. #3
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    Mmmm. Twin tilting balls. Isn't there a native american joke in there somewhere?

  4. #4
    willtsmith_nwi
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    Link Please ???

    http://www.fallbrooktech.com/02_Demo.asp


    It looks to me like this thing will have some serious efficiency problems. Each of the balls is skewered. And it looks like the balls are forced to laterally (to varying degrees) to the hub.

    Also the mechanism for tilting those skewered ball units looks a little tricky. I would be concered about keeping these in sync.

    If it works out, it will be a great option for a hub or a G-Boxx.
    Last edited by willtsmith_nwi; 04-24-2005 at 12:32 AM. Reason: Found a link, changed my attitude a bit.

  5. #5
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    there were guys at interbike last year showing off this technology. They made a tranny for a m1 tank, and without changing the rpm at all, they could go from 30mph forward, ll the way down to stopped, and then into reverse, with no break in the power transfer. impressive stuff.

  6. #6
    willtsmith_nwi
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    I would be more interested ...

    Quote Originally Posted by Pentacle
    there were guys at interbike last year showing off this technology. They made a tranny for a m1 tank, and without changing the rpm at all, they could go from 30mph forward, ll the way down to stopped, and then into reverse, with no break in the power transfer. impressive stuff.
    I would be more interested to see someone pedalling around on one of their trannies. What is the efficiency in this unit, what is the weight???? If there is too much friction in the unit, it will never fly in the biking world.

    I get a little suspect of IP companies pimping technology around that they aren't willing to actually bring to market.

  7. #7
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    Efficiency is important, but a more fundamental question is how does this gear box work?

    It is simple to understand how using different circumfrences around a ball bearing can provide differing gear ratios. But what I don't understand is how does the input drive (transfer power) the output disc. The interface between the input and output appear to be just the ball bearings, and well, that would just make the input spin and the output would remain stationary. What am I missing here?

  8. #8
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    Quote Originally Posted by nmcg
    What am I missing here?
    The common theme in every internally geared hub is some sort of anti-torque device. Shimano and Sram both have axles with flat sides that won't rotate inside the dropouts. Rohloff has various options, such as an arm which connects to the chainstay or tabs which slide into extended dropouts.

    Each has the same purpose: hold part of the guts of the hub "fixed" in relation to the frame, so that the gears and hub shell may spin around it. That part is represented by the yellow axle in the NuVinci video on their website.

    Unlike a cartridge bearing, the "balls" in the NuVinci are fixed to this non-rotating portion of the hub -- they don't have the ability to freely rotate with the input wheel.

    NuVinci is generating enough clamping force between the two plates that the balls can't slide, so as the input plate drives the balls, the balls transfer that motion to the output plate.
    speedub.nate
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