Tap, Stud, Nut, and Cap

 I had ordered 1.25 inch threaded rods for the studs.  Once I got them I realized that the pilot holes needed to be a little deeper.  Then there was another crossroad, cut the rods, or deepen the holes.  At this point I had already tapped fourteen holes.  So, well, the easiest rework was to make the holes deeper which was cutting aluminum.  Otherwise I would have been cutting twenty four steel rods.  Also, I am thinking I want more steel content around the periphery of the rotor for a little flywheel effect.

When I first cut the pilot holes around the periphery I made them 800 mils (0.8 inch) deep.  Then, after picking, and buying the threaded rods I realized that the pilot holes needed to be right at 1 inch.  So I have to rearrange the Mini Mill to do radial indexing again, and align the rotor to make all the pilot holes 200 mils deeper.  This went fairly quickly because I had already set up this operation.  After making the pilot holes deeper, I could tap all the holes deeper, then install the hardware.  I did have the issue of drilling holes that were already tapped.  This did work well because the original pilot holes are still there, and the threads are cut into the walls of the pilot holes, so you just have to be careful to run the drill bit between the existing threads, and not chew on the walls of the pilot holes.

The last task on the rotor was to increase the size of the center hole so that I can mount the rotor on the arbor that I will use to hold the rotor on the motor.  I have used this center hole as a center in all the machining processes.  So I want to change the size of this hole without affecting the position in the X, and Y axes.  The right thing to do would be to put the rotor on a lathe, spin the part, and use the center chuck to hold a drill bit to bore out the center hole.  So, instead, I used drill bits on the drill press to do this.  I didn't firmly clamp the part so that the drill bit could center itself in the hole.  Then used a series of bits to increase the size of the hole incrementally.  So, in about six steps I increased the size of the hole from around 230 mils to 375 mils.  Then gave it a test fit on the arbor.

The completed rotor weighs 22 ounces, which is heavier than I thought it would be.  I've also been thinking about things like the flywheel effect, and the gyroscopic effect.  When I spin it the torque effect from the spinning rotor will drag the frame in the same direction.  So, having mounted it, and spun it a little, like five minutes ago, it does seem to be reasonably balanced to spin at low speeds.  As the speed goes up, it does vibrate a little more, so when I start finishing the part I'll pay more attention to the balance on the rotor.

So, now I need to start thinking about fabricating the stator which is the collector for the system.  Yeah!  It Spins...