Forget fiddling with derailleurs and gear levers mid-commute. Instead, Bafang wants to make urban e‑biking smoother than ever with its…
Forget fiddling with derailleurs and gear levers mid-commute. Instead, Bafang wants to make urban e‑biking smoother than ever with its…
Oh man, I have some mixed feelings about this. The first few iterations of automatic transmissions for automobiles (circa 1970s I think?) also used mechanical means for shifting, somewhat similar to centrifugal governors. While they did remove the need to manually shift, my understanding is that they were also not exactly predictable. And since automatic transmissions wouldn’t be very useful in performance cars, they would have found use in mid-tier cars with mid-tier performance. So a mis-shift would leave the driver poorly configured if, say, they’re trying to accelerate to merge onto a highway.
For 250 W ebikes limited to 25 kph (15 MPH), this might be less of an issue, but I hope that Bafang can skip over that part of automotive history and that it Just Works™ for typical human pedaling cadences.
In that regard, the calculus should be simpler because the “dynamic range” of pedaling cadences is only some 50-200 RPM, or 4x between slowest and faster. Whereas for automobile engine speeds, the range can be 700-7000 RPM, or 10x between slowest and fastest. And even if Bafang sets the gear ratios consistently too high or too low, the sprocket ratios of the chain/belt can be used to tune that linearly. So bike manufacturers should have a number of parameters they can tweak, for either leisure- or commuter-oriented product lines.
I think all they mean by that is they don’t depend on external sensor data for this. The motor has internal sense of the speed, either through dedicated speed pickup, or through the rotor hall sensors. At least that’s my interpretation.
More recently, look at the shitshow CVTs were for a decade.
CVTs on automobiles were definitely released before all the issues were fully resolved, no question there. Though I think for fixed machinery and personal mobility, CVTs have substantial benefits, if they are properly engineered for the task. The major drawbacks being efficiency and packaging.
Supposing maybe Bafang develops on this present idea and makes an integrated CVT hub motor, an ideal implementation would have the torque sensor adjusting the ratios to keep the human at a constant effort.
Would it result in the pedals having nearly zero relationship to the actual effort of moving the bike, being essentially spin class but in public? Almost certainly. CVTs automobiles aren’t exactly considered fun to drive. But bikes for transportation is a key segment, and some people just want a bike for points A to B.