Tesla Coil Construction Project

Secondary Coil

I first cut a 30 inch long piece of 6" PVC (6-1/4" OD) pipe using a hack saw. After finding out that the available wire that Tom acquired was only 24 gauge, I figured I better cut the length down a bit to reduce the number of turns and the DC resistance of the long length of small wire. Here you can see the original 30" PVC and the freshly cut 20" pipe. Leaving an inch or so exposed at the ends, the pipe length will be wound about 18 inches with the 24 ga. wire. I got a couple of PVC end caps with the pipe, but found them to cover about 3" at the ends of the drain pipe. Using my trusty hack saw, I reduced the overlay to a mere 1/4". I drilled a 3/8" hole in each end cap for the "all-thread" supports. I plan to wind the 30" form later with 20 ga. or 22 ga. wire.

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I threw together a coil winding jig out of an old drill I got for a buck at the Monroe, Michigan hamfest. I took the drill apart, removed all the switches and batteries, then hooked a wire directly to the motor. Next I fastened it to a sheet of plywood with a piece of scrap metal, a hose clamp and a wood clamp. Another piece of scrap metal was bent and drilled, then clamped to support the other end of the form. On the floor you can see an old foot switch which will be used to control the drill motor power.

I next fastened the winding jig to the coffee table with a couple more wood clamps. The drill motor was wired to a 0-20 volt Lambda power supply through the foot switch. (The power supply was another $1 hamfest bargain, but I did have to carry the boat anchor to my car--UGH.) I drilled three 1/8" holes at one end which will be used to mount the coil. I also drilled a very small hole at each end for the wire to run through.

Here you can see the coil form mounted to the jig, ready to turn. Ham radio operators may notice that the bar used to support the wire as it unspools is a mast from a Hustler mobile antenna. I just sat on the chair with the wire spool on my legs. I tensioned the wire by gently pinching it with my left hand while wearing a leather glove. My right hand thumbnail rode along the edge of the wire as it spooled on to the PVC to press it against the previous winding.

This is after just 5 minutes of winding. The drill spun the form 30 to 60 RPM. With the power supply set to only 5 volts to the drill, I could easily control the speed by increasing the wire tension.

Voila! Just 30 minutes later I have 18-9/16" of coil complete. This includes a few stops to check the mechanics and have sips of soda. It all went on real easy. The only problem was about half way through, the thing was getting a bit floppy. I found the wing nut inside the right end was coming loose due to the spinning. I suppose I could have oiled my homemade bearing, but it didn't squeak all that much.

Here the coil is removed from the jig and ready for coating. In the background you can see the aluminum dryer duct that is being prepared for the toroid terminal.

A quick measurement shows that I have about 44 turns per inch. With 18-9/16" of pipe covered, I have about 817 turns of wire. At just over 19.6" per turn, I have about 1,337 feet of wire coiled!