These are the rotors into which you'll cast magnets if you construct Hugh Piggott's 8' diameter axial flux wind turbine, or otherpower.com's 10 foot dia. wind turbine design--or if you choose to design your own machine. We have these rotors custom-cut with a CNC water jet machine, so that all holes are perfectly centered and aligned. The finish is excellent. These are 12" outer diameter. They have a 2.75" diameter hole in the middle. Both have 4 holes, 5.010" in diameter located on a 4" diameter circle (this is a common bolt pattern for car, and trailer hubs), and one has an extra 4 holes which are tapped 1/2" - 13 for jacking screws. (you need jacking screws to assemble, and disassemble finished alternators) These rotors are a perfect fit for both Hugh Piggott's and otherpower.com's plans. They could save you hours of cutting steel plate with a torch, grinding, and drilling. The stud holes are perfectly aligned to fit common Dexter trailer hubs. Note -- some of these rotors come out very slightly warped along the flat plane (the worst we've seen is about .050"). If you find that a rotor is slightly warped, you can either try to flatten it, or - if you use it as is be sure to put your magnets on the convex surface, this makes the alternator easier to adjust. They become warped due to the way the flat steel sheets were handled before cutting, and it's out of our control. It's truly a minor issue but we mention it so there are no surprises.

Also note! While we usually keep these in stock, they are sometimes made to order. If you order a set of these from us, we'll let you know the status - it may take up to 10 days before we can ship if we have to build them for you. The price gets you two rotors, with all the holes drilled and 4 holes tapped for jacking screws in one of the rotors.