Step 5: Drill Holes in Plexi-glass
This step will be based on the bolts that you used and the bearings that you used but it will consist of an eight hole pattern with the holes spaced 45 degrees apart just like the hard drives. Then you will drill a hole in the center of the sheet of 7×7″ plexi-glass, I drilled a 5/8 inch hole because of my bearings and then you can just drill an appropriate sized hole for your bearings. In only one of the pieces of plexi-glass you will need to drill a few holes around the center hole for exhaust ports. The larger the hole the larger the high rpm’s horsepower and the smaller the holes the more low rpm torque. I drilled four 3/8 inch hole around the center, 25 mm out from the center, so you could use the same pattern you did for your hard drive disks just skip every other hole. And four 3/8″ hole is about right in the middle of the two rpm ratios. Also, use a 3/8 inch bit for the eight hole for the bolts to go through if you are using 5/16 bolts like me. These holes are 2.5″ from the outside of the 5/8 inch hole you drilled in the center or if you did not drill a 5/8 inch hole they are 2.8125″ from the center. This is another eight hole pattern like for the disks so like I said before space them 45 degrees apart.
Step 6: Cut Pipe and Drill Air Inlet
Cut your pvc pipe to 2.2″ and then drill a hole the size of your tubing into the middle of your pvc pipe and offset it a little bit so it is at an angle so that when the air enters it, it immediately starts spinning inward. Once this pipe is cut to make sure the whole end surface is even, take it on the lathe and face it off until smooth, then take some 600 grit sandpaper and smooth the ends so no air can escape when the plexi-glass is put onto the ends. If you want to skip the sanding then just put some silicon or mopar sealer around the ends to keep the air from seeping out. On my project I did not do this, I just sanded it because in my opinion it gives it a better appearance. This step is pretty self explanatory.