Nikola Tesla Books
KICKING COIL APPARATUS 81 first layer must have its turns separated ½ in. Over this layer of wire are placed three more layers of paper; then another of wire with turns spaced ½ in. This is repeated until 50 layers are in place, the turns being gradually placed closer together until, with the 50th layer, they are separated only 1/32 in. From this point on and until the 150th layer, which completes the coil, has been wound, the turns may be spaced about 32 to the inch. The layers should be but one inch in width in order that a margin of 1/4 in. may be left on either edge. The final layer of wire is to be covered with 10 layers of oiled paper, the end of the winding being brought out ready for connection with the primary. The primary consists of 10 turns of copper ribbon, 1 in. wide, wound spirally around the secondary pancake. Between the turns of the primary is a strip of corrugated board such as is used for packing purposes. The finishing end of the secondary is soldered to the starting end of the primary and at this point a length of flexible lamp cord connects to the junction of the two. The ten primary turns are then wound and a tap of lamp cord taken from the under edge of each of the turns from the third to the tenth inclusive. This provides a means of varying the primary inductance while tuning the apparatus. The final primary turn is held mechanically by means of a wrapping of several layers of oiled paper; the latter may be shellacked in place. Removing the coil from the lathe, we now have the complete winding ready for impregnation with the compound already suggested for the condenser. The entire coil is to be immersed in the molten wax for several hours and, before its removal, the heat should be withdrawn in order that the mass may partially congeal. As the wax shrinks on cooling, it is essential that the substance be
