My friend Burney and I finally finished the rotary axis for Joe's 4X4 Hybrid. Here are lots of pictures that I hope make it clear how it was built. The rotary axis is hung between the first and second unistrut so that it is parallel with the X axis. The second unistrut is pushed back up against the third unistrut so that there is about 15" between the first two unistruts. The table has been cut off at the third unistrut. The fact that the second unistrut is pushed back against the third unistrut makes it easy to put the cut piece of the table back on when the rotary axis is not being used.
The rotary axis consists of the headstock and the tailstock. The headstock shaft was made from 1" diameter drill rod. It was threaded 1-8 at one end and turned down to 3/4" at the other. The 3/4" end holds a 30 tooth pulley. The motor is mounted on a 12" X 6" aluminum plate milled with the appropriate features to mount the motor. Slots are also milled into the plate so that it can be mounted in a way that allows the belt to be tensioned. The motor pulley is a ten tooth pulley giving us a 1:3 ratio. The stepper motor is 1200 oz/inches giving us a lot of torque for larger work pieces.
The tailstock was purchased from Grizzly for $50. Both the headstock and tailstock are mounted on 3/4" plywood. The plywood is bolted to 2" X 2" X 1/4" aluminum angle. The angle is bolted (using slots for adjustment) to another piece of angle that rides on the unistrut and is held to the unistrut with 5/16" bolts, unistrut nuts and handles with threaded inserts.
This all sounds complicated, but it is a really clean and easy to fabricate design. The rotary axis can be pulled off the machine in seconds and the table top returned to its original size in a couple of minutes. Please look through the pictures to understand how it was all done. BTW, as designed the rotary axis will handle a work piece up to to 41" long and 12" in diameter. I will be happy to answer any questions you may have.