Making the rear magnet rotor.
This is the first of the two magnet rotors. The alternator will be made up of 12 coils of winding wire, sandwiched between two disks of neodymium magnets, 12 magnets on each disk. 24 in total. Each magnet measures 3/4" * 1/2" * 1/4". I bought these magnets a few years ago when I first got interested in building a wind turbine. I'm going to see what kind of power I can get from them, seeing as I already have them. If I were buying some new, I'd get larger ones. I may still end up buying some larger magnets if these ones don't work out. That'll mean a re-design of the rotor disks to accomodate the larger magnets.
The pockets for the magnets are an odd shape due to not being able to cut out a square hole. So the corners are enlarged to allow for the diameter of the milling cutter. These enlarged corners will also help to hold the magnets in place. They will be filled with epoxy resin.
I've made the rotor disk from MDF. This may seem like a strange choice of material. Iron or steel would have been better choices, but that would not allow me to cut the disks out on my CNC router. MDF is more stable than most natural woods and if it's sealed well it should last a fair while outside in the elements. That's what I'm hoping. I may find that I need to place some laminated steel strips in the back of the disks, directly behind the magnets. If that is the case, a channel can be milled in the back of the rotor, if and when required. The centre of the magnet rotor is bored out to accept a 6004 sizedbearing. That's....42mmoutside dia, 20mm inside dia, and 12mm thick. Here's a few pictures of the rotor disk with the bearing and magnets being tested for fit.
The reason I chose 12 magnets each side is that I plan on trying a 3 phase setup at some point. All I'd have to change is the disk in between the rotors that holds the 12 coils. (The Stator). This would be replaced with a 9 coil stator, wired as 3 sets of 3 coils. The magnet rotors will remain exactly as they are. These will now be lacquered with the type of lacquer that's used on car paintwork.