Hi, I used bushing with a PVC pipe on the outside. The problem was I did not extend the PVC pipe all the way to the bottom of the test fixture. It was a learning experience. The PMA survived. Considering that it was slammed it to the pavement at 65 MPH, the magnets are still in place on the rotors without using glue, the drive shaft was not bent, I was able to observe a constant increase in output, and the hole unit did not explode in to many smaller pieces. I should have repairs made in a few days and be able to test the gearbox. It did show the fabrication method to be sound and stable. The max RPM was around 300. I have to design the PMA to perform better at lower RPM's. Comments welcome.