Cut the aluminum for about 6 mm as wide as the bearings
. Wrap it to the bolts; put the bearings inside, press by the nut till it is fixed. Do this for both bearings. This will make the bearings attached tightly to the bolt (Axle). Making the house Cut the board into two equal sizes (@ 19.5 x 22 cm). Point the center out then divide each board into 4 parts. Combine these two boards; drill the corner of each as a guide with 6 mm drills. Drill the center point with 4 mm drill. Separate the board. Drill each of the boards' center with 21 mm fan board within 5 mm. you should also drill the center point with 10 mm fan drill. Combine all of them using 4 mm rod bolts. Make sure that the turbine rotates freely. You can cover it with aluminum plate or fiber.