With these files, 26 AWG enameled copper magnet wire, two common 608 ball bearings, 12 3/4 inch x 1/8 inch neodymium magnets, and a 16d nail, you can build yourself a 10V DC generator that fits in the palm of your hand in about 2 hours. You'll need to print one of everything and 3 bearing diameter adaptors. To wind the copper, weave the wire around the arms in the winding guide around 100 turns, up and down. This can then be fitted into the outer casing along with one 608 bearing. Attatch your 12 magnets together in sets of two, and then insert the pairs into the slots of the magnet holster. Put your other 608 bearing into the hole in the top plate, and fit two of your bearing adaptors into each of the ball bearings. Put the 16d nail in through the top plate bearing, and through the magnet holster with about a 1/16th inch tolerance between the two. Fit your last bearing adaptor onto the nail up to the bottom of the bearing holster and glue everything in place. Finally, fit the nail through the bearing adaptor in the bearing of the outer casing and fit the top plate in. From there, you can attatch a hand crank or turbine head onto the nail, and generate electricity!

Note, 3D printed 608 ball beaings can be used in this project, but will result in less smooth revolution.