A Drone Motor Does E-Bikes

On paper, the motors from both an electric bicycle and a drone can both take about 500 watts or so of power. Of course, their different applications make them anything but equivalent, as the bike motor is designed for high torque at low speed while the drone motor has very little torque but plenty of speed. Can the drone motor do the bike motor’s job? [Pro Know] makes it happen, with a set of speed reducing and torque increasing belts.

The build takes a pretty ordinary bicycle, and replaces the rear brake disk with a large pulley for a toothed belt, which drives a smaller pulley, and through a shaft another set of pulleys to the drone motor. The bracket to hold all this and the very large pulley on the wheel are all 3D printed in PLA-carbon fiber mix.

When it’s assembled, it runs the bike from a small lithium ion pack. That’s not unexpected, but if we’re honest we’d have our doubts as to whether this would survive the open road. It’s evidently a novelty for a YouTube video, and we’d be interested to see how hot the little motor became. However what’s perhaps more interesting is the choice of filament.

Could carbon fibre PLA be strong enough to print a toothed belt pulley? We’d be interested to know more. We saw the same filament combo being tested recently, after all.

37 thoughts on “A Drone Motor Does E-Bikes

      1. There are many different clones and reimplementations often substantially better than the last opensource vesc hadware. Look for ones measuring current on all three phases. Also last year when I checked there had been forks coming bypassing extremely sensitive TI’s DRVsomething chip and reimplementing it with discrete mosfet drivers and a little more software.

        I have CheapFOCer v2 VESC hw reimplementation. Works OK.

  1. Power-transmission drive belts are traditionally made of rubber coated cloth, technology that has been refined literally over centuries. Belt drives dominated the industrial revolution well before steam and electric power (e.g. water-powered textile mills). Modern toothed belts may even sport composite materials. This low-tech history would make for an interesting Hackaday article all by itself.

    1. You could have one on the history and another on the ones that are still around, maybe with a bit about how they relate to chains. There’s flat serpentine belts, vee-belts, cogged belts, asymmetric belts (which I know of from their use in go kart cvt’s), belt-like things with some odd materials or structure… Some of them transmit force on both faces, some don’t but can still have tension applied from that side, others would have their spine broken by too much of a backwards angle… There’s even twisted belts, although using that for a right-angle turn is more of a historic thing.

    2. Just no. I build belt drive mountainboards, ebikes/motos, and was a competition RC pilot before drones were ever a thing. No way this multi-belt setup would be robust enoughto be viable in the wild. 👎

    3. That doesn’t change the fact that they’re very inefficient in low-torque loads – far less efficient than a chain, and there’s two belts. Bicycles are all about efficiency, and this will fall on its face.

      The other problem? Noise. It’s high-pitched and annoying.

      Still yet another problem: that tiny drone motor can handle 500W because it had an insane amoutn of airflow from the props keeping it cool. On a bike, there’s a fraction of the airflow.

      And yet more problems: zero weather-proofing, mechanical fragility, entanglement, an entire side of the bike can’t be used for carrying bags, and so on.

    4. Back in the day, horses pulled portable steam engines that used belt drives to operate farm equipment. Eventually, somebody got the bright idea of connecting the steam engine to the wheels to make self-propelled steam engines that they called “tractors”, which still had the power takeoff pulley to drive belts.

  2. I wonder how well this manages heat. I know some cheap drone motors (and or controllers) assume they will get a lot of airflow from the propeller for cooling, but don’t do well if you run them with something else instead.

  3. Meh, a simple demonstration that power, torque, and RPM are related to each other. Want more torque? Use a transmission to increase torque while reducing RPM. Want more RPM? Use a different transmission to increase RPM while reducing torque. Only advantage in having a closer match between available torque from the motor and required torque for the job is a simpler transmission between motor and task, with the advantage that a simpler transmission is cheaper and usually more efficient.

    1. He mentions at the end that the bike won’t do more than 10km/h on the battery he’s using, it’s fine. It’s clearly just a demonstration of the concept. If he makes a more practical version, he could always add a clamp break on the rear wheel anyway.

      1. -Hills exist
        -Any two-wheeled vehicle with only a front brake is a suicidal idea. Braking hard in an emergency will go exactly the way you think it does. You gotta design for emergencies, not nominal use.

        Also the difference in relative size between the motors doesn’t pass the smell test. That motor is going to be toasted soon anyway, I don’t care what the wattage rating is.

        1. In an emergency on a bike the front brake is the only brake that is doing any good. The rear brake is only useful when you are not braking hard enough to get much weight transfer, when the front brake would be fine anyway.
          I know lots of folks who have only a front brake on their bike.

    2. Rear brakes are pretty useless as most of the forces are put on the front tyre when braking. Just try stopping your bicycle using only the rear brake compared to the front.

      1. Have you ever tried stopping a bike or motorbike using only the front brake though? Like a fast stop to avoid running into something? You will go over the handlebars. Have you never done that? The front brake does dissipate more energy than the rear, that doesn’t mean the rear brake is useless. At all.

        It’s supposed to be a 40/60 split favoring the front brake, you don’t get rid of 40% of your braking capacity frivolously

        1. I’ve had the rear wheel lift off the pavement an inch or so, you don’t want to do that suddenly. If you are breaking that hard to avoid hitting something and apply the brakes hard enough to transfer 100% of the weight to the groin wheel the rear brake can’t help you and you are probably going to have a your choice of crashing because you aren’t braking hard enough or you’re braking too hard and going over the bars. Rear brakes aren’t going to help.

    3. Takes a few seconds to put on an old school cable pull break. Might have to weld a bracket to the frame, if it came with discs.
      Assuming he didn’t do this, he does deserve to be kicked square in the balls.

      Rear disc breaks on a bike are a ‘I have so much money I waste it’ flex. Like a CF frame. The realm of spandex clad T.D.Frog larpers.

  4. I have done this for an electric longboard (though with a much more powerful motor). The only issue with the printed parts was the heat of the motor. Tried both abs and pla, and anything touching the motor failed, everything else was fine.
    I still have an abs pulley on one wheel, years later. It’s epoxied in place because the wheel itself could not withstand the tourque from the motor, but the pulley is fine. But pretty worn from gravel/abrasion and small stones passing between belt and pulley.

    1. Agreed, and the motor is tiny compared to the original motor. Don’t care how high-tech, there’s no substitute for size and mass when it comes to dissipating wattage. I give this contraption a couple miles maximum

      1. Heat pipes are a substitute for size and mass when it comes to dissipating wattage. You know, hot end, cold end, hollow tube full of working fluid selected for boiling point. Still needs a heat sink. Including heat pipes results in similar performance with a smaller, lighter, more expensive package.

        You are not wrong about this motors expected life. Not so much from running, but when it first gets stalled. Motor life will depend on how the ESC is programmed.

  5. This was all solved and productionized by the Currie ezips back in the 80’s. I’ve had one for years. Its stone reliable and easily maintained in service. I recently upgraded to LiPo4 batteries. Which gave the relic a new lease on life….

  6. Why not power one of the gears on the crank? You’d get to use a proper chain and have a selection of chainrings (from 22T) to mate up to until you find a decent ratio.

    1. With so little power available I fear that driving a sprocket on the crank incurs too much additional friction, both in the change from belt to chain as well as in the additional chain to the rear wheel. This of course is my extremely humble opinion.

      1. That’s because it’s a hilariously too-small motor. Why would you take a motor that’s supposed to propel a few grams of unmanned aircraft (spread between four motors) and bolt it (plastic it) onto a vehicle that transports the mass of a man? And is pushing rigid mechanical parts coupled to hard asphalt instead of air? Doesn’t seem like a good idea

  7. If I were turning a drone motor into a bike motor, I would imitate velogical…

    I’d leave the disc brake in place, and put a pair of motors on the seat stays.

    Each motor would spin a tiny tire which would press against the rim of the bicycle tire, about where caliper breaks would press on a bike which had them.

Leave a Reply

Please be kind and respectful to help make the comments section excellent. (Comment Policy)

This site uses Akismet to reduce spam. Learn how your comment data is processed.