You can use the same magnet. This time you can use a piece of iron pipe (diameter: 1 inch) as the holder. The goal is to make the distance between the magnet and the coils can be as close as possible to get the maximum result. You need to arrange the magnet position into North-South-North-South. Then wrap the magnet with resin so the magnets will keep on its position while you rotate it loudly. You should fill the iron pipe with resin then drill it so that the 6 mm bolt rotors can be placed in the middle of the rotor. It needs to be fastened using nut on its top.