Tesla Three

Building the secondary

I always thought this was going to be tricky. Tesla Three is a small coil, so the secondary has to be made with very fine wire. This is especially true since it's an OLTC, so you need to aim for a low resonant frequency. I originally intended 85 kHz.

A "Falcon" brand 2-liter culture flask

My old man got me this flask out of the biochemistry labs where he works. It's 9" tall by 4.6" diameter and appears to be made out of very thin acrylic or lexan. An ideal former for a "Stubby" secondary. I also bought the thinnest magnet wire I could find which was 0.125mm gauge. I calculated that I could fit 1520 turns onto the flask and the DCR would be 780 ohms. The FANTC simulator told me that it would resonate around 125 kHz with a reasonable topload. It's not 85 kHz, but it's the best I can do under the circumstances.

The winding jig

I made a special jig to help with the winding. The flask is held between two woodscrews that stick out of the uprights. A motor (from an old VCR) spins the flask slowly by means of a rubber band.

Halfway there

Even with a motor to spin it, winding this thing was a major pain in the butt. I even managed to snap the wire once and had to splice it back together.

Finished at &!%$?:~@ last

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