The secondary coil on our Tesla Coil was built around a 4.5 inch PVC form and was 22 inches of coil with a total form height of 26 inches. A few things to keep in mind when choosing a form: 1) make sure the form you are using contains no metal. Some PVC pipe contains metal to help it be found after being buried in the ground. 2) In our case we bought 4 inch PVC pipe. 4 inches was the measurement of the inner diameter of the pipe, not the outer, so always keep that in mind when designing a secondary coil. The wire we used was 24 AWG polyurethane coated magnet wire. We used about 1000 feet of wire to wind 22 inches of our coil. We also drilled two small holes in the pipe at the top and bottom to run the wire through to make its connections to either ground (bottom) and to the torrid (top). To wind the coil we strapped the PVC pipe into a lathe and then manually spun the PVC pipe while guiding the wire to make sure it stayed taught and there was no gaps. In retrospect, It would have made more sense to run the lathe on its lowest speed setting rather then turning the pipe by hand.

Below is a photo of the finished coils. There are two coils because originally we planned on building a transmitting and receiving coil but later scrapped the idea after deciding that our knowledge of high frequency wireless power was not sufficient enough to use that idea.

We used 4 inch toilet flanges to mount the secondary coil to the base inside of the primary coil. The slots in the flange lined up perfectly with out primary coil supports.