I am attempting to make a useful and accessible motor using cheap, widely available parts and utilizing 3D printing where it makes sense. Currently I am on my 8th version. The current version is an out runner style brushless motor with a single stator a two rotors.
The stator is three phases in a type of serpentine coil pattern. There is no ferrous core resulting in no cogging and no core losses. The wound stator is pressed and potted in epoxy and mechanically fastened to the hub.
The rotors each contain a halbach array of N52/N50 magnets stuck to an laser cut iron backing that is epoxied into the 3D printed halves.