e-bike motor

2 Articles

Open-Source Mid-Drive E-Bike Motor Has Lots Of Promise, And Hyphens

July 18, 2026 by 19 Comments

[Pedro Neves] has a mid-drive e-bike, but he doesn’t own it — not truly, since he can’t repair the motor unit. For a hacker to be in that position, there are only two options: crack the old one and make it your own, or build your own from scratch. [Pedro] built his own and is open-sourcing it on his website for everyone to play with. Right now, that’s .step files and a BOM, so you’ll need to watch the design/build video on YouTube below to get the full picture.

His choice of a motor from an old battery-powered angle grinder is both thrifty and environmentally friendly, so we approve. His goal of 25 km/h seems like a reasonable speed limit, but may still be too fast for some countries’ regulations— so do check the local rules if you’re going to build this. Making the most of 3D-printed components is also a choice that makes the project more accessible, but don’t worry — the bearing surfaces are all metal. That includes the clutch bearing that will let you pedal home if the battery dies or the motor craps out. Well, unless the printed plastic axle gives up the ghost, but that got replaced with a CNC version, so it’s all good. Unless you’ve got legs like Hercules, it ought to hold.

If that’s not DIY enough, you could always build the motor yourself. This mid-drive is also part of a larger project [Pedro] is working on for a whole cargo bike, as he details in his video, which is a worthy project we’ve seen other examples of before.

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An E-Bike Motor From First Principles

May 14, 2026 by 17 Comments

Many of us have made electric transport of some form, whether a Hacky Racer, and e-bike, a go-kart, or whatever. We have invariably bought a motor, or if we are really adventurous, repurposed a car alternator. Not [Birdbrain] though, because she’s designed and built her own from first principles.

The video below goes into significant detail on the design of her motor, looking at cores, wire sixes, and configurations with a useful simulation along the way. We particularly like the way she uses a bandsaw to cut transformer laminations to shape for her core. The 3D printed housing initially isn’t strong enough for the forces induced by the magnets, but she attacks that problem with a new print. The motor works well, and as an added bonus there’s an introduction to the different types of motor driver. It seems the cheap ones don’t deliver a good waveform for the characteristics of the motor. Sadly she doesn’t fit it to a real bike in the video, but it seems this thing might just work.

If you lack the courage to make the whole thing from scratch, we took a quick look at the car alternator route a while back.

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