We’re always patrolling for patents, and just stumbled upon a brand-spanking-new freehub design from Campagnolo. Instead of relying on a traditional ratchet and pawl system, it uses an innovative clutch and magnet arrangement – which appears to be an attempt to eliminate freehub drag.

Campagnolo Clutched Freehub Patent

If it seems like we’ve been covering a lot of new patents from Campagnolo, it’s because they seem to be on a mission to innovate and regain a sizable portion of the market. Their latest filing isn’t necessarily earth-shattering, but it addresses a potential efficiency gain that’s often overlooked: freehub drag.

As with many patents, the language is complicated – and may be further exacerbated by language translation (Campagnolo is, after all, Italian). For example, they refer to the hub shell as a “hub sleeve”, and the axle as a “hub pin”.

Buried in the patent is what appears to be the key issue being addressed, which is the drag caused by traditional freehub systems:

…results in a dissipation of kinetic energy of the rear wheel that can even be of the order of about 2 Watt at speeds of about 50 Km/h when the cyclist stops applying propulsive action. Such a dissipation of kinetic energy has a negative impact on the performance of the cyclist, forcing him/her to make greater effort to compensate for the kinetic energy dissipated.

Rather than relying on pawls, ratchets, or ring drives – the Campy design uses magnet-operated clutches for engagement.

When the cyclist interrupts the propulsive action, the second annular body pushes the first annular body (by means of the interference between the crown gears of the two annular bodies) in an axially outer direction decoupling the cassette from the second annular body (and thus from the hub sleeve). The first annular body thus reaches a free wheel configuration.

The Applicant has perceived that by arranging coupling members that axially translate the first annular body towards the second annular body in the case in which there is a rotation of the cassette with respect to the first annular body, the first annular body remains stably in the free wheel configuration (and does not tend to go back into the motion transmission configuration) until the moment when such relative rotation takes place.

The Applicant has found that by arranging magnetic members that oppose the rotation of the first annular body with respect to the hub pin, the first annular body moves axially towards the second annular body (and thus towards the motion transmission configuration) only when the cyclist starts the propulsive action again.”

No word yet on if or when this new hub will hit production – nor the actual watts saved. We will continue to follow the story for further developments.



  1. Tom on

    can’t say I’ve ever felt impeded by freewheel drag – after all, I’ve stopped pedaling because I need to slow down a little.

    • K-Pop is dangerous to your health on

      This design isn’t even in the ballpark of how a one-way sprag clutch works. That’s like saying a boxer engine is similar to a rotary.

  2. Mark on

    Was there anything in the patent about engagement speed/degrees? Noise? Weight advantages? Hub retrofitability?

    It looks like there are still star ratchets in many of the figures. It almost looks like a Chris King RingDrive, but with the engagement pushing the cassette body away from the hub instead of towards. And of course, magnets.

    So, to answer my questions:

    Regarding retrofitability, it almost looks like a standard star ratchet hub body. One would only need to take out the hub’s star ratchet spring, and install a new axle and cassette (with its star ratchet).

    Engagement may depend on how the magnets are lined up. It looks like the magnets are in the axle and the cassette’s star ratchet, so it’s not like they move in relationship to each other as you’re coasting. So it’ll be worse than a hub with similar star ratchets.

    Noise should obviously be silent if you’re reducing friction as much as possible.

    The magnets will be a bit heavier than the bits of aluminum they’re replacing, slightly offset by the lack of steel springs. The helical mechanism pushing the star ratchets should probably be made of steel, and the mating surface in the cassette body too, so weight will probably be a bit more.

    Other observations: The helical mechanism may have special lubrication requirements if you don’t want the magnets too strong- any grit in there might be troublesome. And I bet the hub will also feel notchy like a dynamo hub when turning the cassette, there still should be no (or little) net loss of power when pedalling.

  3. Cheese on

    So Chris King with retraction magnets instead of an engagement spring. I’d expect this clutch to slip frequently as dirt builds up.

    • K-Pop is dangerous to your health on

      This design isn’t like King either, but thank god it didn’t take you a six paragraph essay in a comment section to come to that conclusion. Which btw RingDrive™ is patented, so Chris would’ve sent lawyers to Italy earlier this month when the patent filing was made public. I’m starting to see a pattern of not being able to interpret schematic diagrams. And you’re anticipating clutch slip? Huh, wut? Oh right, because you know… Campy has long and sordid history of making bad hubs. Pffft! 😀

        • K-Pop is dangerous to your health on

          Ok Cheese, you got me on the patent expiring. But your assertion that this is basically RingDrive with magnets instead of a spring is still coming up awfully short. Do you see a one-piece freehub/driver helix here like RingDrive? I sure don’t. How about the fact that the drive chamber here placed in the typical outside line of the DS flange whereas Ring Drive is well inboard of the DS shell bearing. When you look at an apple and an orange do you just throw your hands up and say it’s all just fruit anyway?

            • K-Pop is dangerous to your health on

              Err, um, did you miss something? The very first sentence from Mark reads:

              “Was there anything in the patent about engagement speed/degrees? Noise? Weight advantages? Hub retrofitability?”

              Does that sound like somebody who actually read the patent?

              You don’t need to read a word of it to realize this design not only doesn’t look like RingDrive, it doesn’t operate like it either. M’kay?

      • Mark on

        No, the retraction is still the star ratchet ramps pushing each other away. The star ratchet in the cassette spins outward in a spiral dictated by the helices on the outside of the star ratchet and the inside of the cassette body. It continues to twist around the axle until the magnet(s) embedded in it catches or aligns with one(s) on the axle.

        When the cassette starts driving forward, the magnets still want to stay aligned, so the star ratchet slides inward. When the star ratchet teeth engage, then there’s enough rotational force to split the magnets.

        Backpedalling would just retract the star ratchet slightly further into the cassette body until it hits an endstop.

    • K-Pop is dangerous to your health on

      Drive by flaming is pretty unimpressive in its own right. You should just say this design is exactly like i9 Hydra just to keep the momentum going.

  4. Mr G French on

    So all the time you are pedalling, the magnets on the floating ring are moving relative to the magnets on the axle like a tiny magnetic trainer, generating small electrical currents that will “see” resistance in the parts and be partially dissipated as heat? Sounds like a net energy loss to me, only during all pedalling rather than just freewheeling…
    Or am I missing something


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