W. Beaty 1996

On winding secondary coils: PVC pipe is probably the best thing you can use. This gets expensive on extremely large (10 ft, 12in dia.) coils, and baked/varnished cardboard "sonotube" concrete forms are usually used then. If you ever use cardboard, its a good idea to lower its conductivity by painting it with many coats of varnish, or that wood-waterseal stuff.

The first coil I tried (back in 1981) I did on very heavy cardboard tube about 4in diameter, and put several strips of clear doublestick tape along it to keep it from sproinging off while winding when I let loose of the wire. This worked fine. Wax might work, but it would have to be sticky.

I cobbled together a winder by taping 8mm movie reels to each end, mounting one end in my old plastic 8mm movie editor, and sticking a rod in the other end , with the rod stuck through a cardboard box support. It worked fine, handcraking the editor and handfeeding the wire. My second coil (in 1993) I did on 5" pvc pipe with double sided tape strips on the pipe, and used a lathe with a footpedal speed control, and hand-fed the wire using leather gloves. On both coils I painted them with polyester resin, the kind used for fiberglas coating. You have to use lots of catalyst in the resin when doing thin coats, or it won't harden.

Since hand-winding a coil without mechanical aids takes hours and hours, I strongly suggest spending a few hours to figure out some sort of winder scheme. Winding on a lathe took me only about 20 minutes, and most of that time was because I kept letting the turns overlap, so I'd have to stop and unwind slowly to correct the kinked turn.

One thing I had trouble with was sparks jumping between the primary and the main coil. The higher the power supply voltage, the better, but at some point the voltage creates unwanted arcs. The solution is to wind the heavy primary turns on an excessively long tube, so the spark path has to go a long distance to get to the main coil.
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