Nikola Tesla Books
LARGE TESLA AND OUDIN COILS 211 them from sockets therein. The primary helix is supported on the secondary cylinder by the three legs as shown in the drawings. The helix is so springy that there is no difficulty in springing the third leg into position after the helix has been placed over the cylinder. The object of having all of the parts removable is of course to permit packing to be done effectively and without the enormous cases that would be necessary if the coil were in one piece. The resonator is made separable in the same manner. The ends of the Tesla winding are connected to the discharge rods through the rods and balls shown in the sectional drawing. The primary is entirely independent and its only connection with the secondary is an inductive one. With the resonator, however, the case is different. The lowest turn is connected to the bottom turn in the primary helix and this in turn to a common ground terminal. The discharge rod 4 is also connected with this ground wire beneath the base. Regarding the resonator, little further need be said save for a few words about the winding. This is in one continuous layer of about 350 turns. As the voltage is lower, this winding may be of No. 18 annunciator wire wound close and most carefully coated with shellac in six applications. The practice of winding the turns close is to be avoided if possible for there is extreme likelihood of the current leaping across through the insulation. A separation of a single turn of thin cord will help materially. In closing it may be well to state that the suggestions given in this chapter are intended for the amateur worker who is not equipped with a lathe sufficiently large to take the cylinders. If the individual is so fortunate as to have access to such a large lathe, he may disregard most of the instructions and proceed in the regular manner.
