Electric-assisted bicycles, or ebikes, are fundamentally changing the way people get around cities and towns. What were once sweaty, hilly, or difficult rides have quickly turned into a low-impact and inexpensive ways around town without foregoing all of the benefits of exercise. [Braden] hoped to expand this idea to the open waters and is building what he calls the ebike of kayaking, using the principles of electric-assisted bicycles to build a kayak that helps you get where you’re paddling without removing you completely from the experience.
The core of the project is a brushless DC motor originally intended a hydrofoil which is capable of providing 11 pounds (about 5 kg) of thrust. [Braden] has integrated it into a 3D-printed fin which attaches to the bottom of his inflatable kayak. The design of the fin took a few iterations to get right, but with a working motor and fin combination he set about tuning the system’s PID controller in a tub before taking it out to the open water. With just himself, the battery, and the motor controller in the kayak he’s getting about 14 miles of range with plenty of charge left in the battery after the trips.
[Braden]’s plans for developing this project further will eventually include a machine learning algorithm to detect when the rider is paddling and assist them, rather than simply being a throttle-operated motor as it exists currently. On a bicycle, strapping a sensor to the pedals is pretty straightforward, but we expect detecting paddling to be a bit more of a challenge. There are even more details about this build on his personal project blog. We’re looking forward to seeing the next version of the project but if you really need to see more boat hacks in the meantime be sure to check out [saveitforparts]’s boat which foregoes sails in favor of solar panels.
Would a piezo detect the impact of the paddle on the water?
I would think the motor/prop spins faster when paddling as it unloads. Rpm sensor ought to do it.
It would also be unloaded when in water flows, including rapids. Would need a way to differentiate between the two, or it’s just going to burn all its power trying to push you harder downstream.
Taking from the “ebike” inspiration, one would install a load cell somewhere along the paddle to measure the force applied (measuring power would be somewhat more complex) and drive the motor proportionally to this signal. I’m curious if this would be comfortable without significant filtering, paddling being much more “bursty” than pedaling.
About 40 years ago I first rode in a canoe with a minnkota 35lb thrust motor pushing it. DC motor on a stick held under water with some resistors for speed control and a 12v deep cycle for energy. I still have it, and it still works. I used it on my 10′ inflatable dinghy recently. I found another 110lb thrust trolling motor at the dump last year, ditched the bow mount stuff, replaced the controller with a generic motor controller and that works too. Bigger motor might live well with 24v. Next step is to package some lithium ebike or tool batteries with it and use it to push my 3000lb sail boat. The only magic here is the packaging on the el cheapo inflatable kayak with some clever 3d printing. The old minnkotas would lend themselves to that too if you just cut their shafts and print a part to hold it, or otherwise jury rig a thing to attach it to the boat. They don’t have enough power really to even need speed control, a hefty on/off switch would suffice. On means you get to walking speed in a minute, so manually controlled pulse modulation would do it.
A rowing scull has a huge acceleration during each stroke — an accelerometer would certainly work in that case to pace the motor. For a kayak, I imagine it would need some tuning to work.
Or could just make it voice activated: Pretend to be a coxswain: You just have to call out “STROKE!” every second or so.
Yelling is always the solution.
160kV motor? Really? Am I misunderstanding something here?
It’s shorthand for RPMs per Volt — ‘k’ standing for ‘constant’ rather than kilo. It’s one of the key values when choosing motors for model airplanes.
Yes, you are misunderstanding something. It’s not kilovolt but “constant velocity”, the RPM which the motor will output, per volt applied, while unloaded. It’s related to the number of turns of copper in in the motor core.
cplamb understood it perfectly: it’s the youtube talent who didn’t get the memo, and sounds like an ignorant fool when he says it’s a “160 kilovolts” motor out loud.
Used correctly in this context, it’s Kv (motor velocity constant), which should sufficiently disambiguate from kV (kilovolts)
I agree, but I also know that when I first saw the abbreviation and figured it out, I thought it was dumb given it’s only differing by capitalization. But then, I wrote code before I learned much math, and I haven’t got the neatest of handwriting. So I never liked how we reuse the same handful of letters of the alphabet, sometimes capitalizing, then adding the equivalent greek letters and their capitals, then adding superscripts and subscript tick marks, all to resist just using another letter instead. It feels like if all your variables in a program were defined using morse code where the dot is a single quote and the dash is a double quote… ”'””””’
We have various conventions for frequency, wavenumber, period, and wavelength, such as in https://en.wikipedia.org/wiki/File:Commutative_diagram_of_harmonic_wave_properties.svg
I could see maybe using rpm(or Hz) per volt, maybe radians per weber if they want to reduce to a couple standard units. Or if we want to make a new name, maybe something like voltnumber since wavenumber or “repetency” is the cycles per unit *distance* and so voltnumber isn’t completely wrong, and Kvn or Cv or Cvn would all be slightly easier to distinguish if you lose capitalization. Or as an angular form of velocity per volt, maybe it could even go down to something relating the electric field vs the motion. The linear form would differ by not having a radius and would have something like the slope of the e-field vs distance and then the distance versus time or whatever.
That’s neat! Regular old trolling motors can be pretty heavy. The hulls aren’t that efficient, and the craft are small, so this probably makes a difference all on its own.
This hack has a significant impact on registration and licensing fees.
Didn’t see this was posted! You guys have given me a ton of cool ideas / info! I’m planning to put an IMU on the oar. And hopefully use that data to detect paddling as well as which way the user is trying to steer.