High Frequency Apparatus Page 183

CHAPTER XVIII. THE CONSTRUCTION OF LARGE APPARATUS. The construction of a high frequency transformer capable of throwing a five-foot spark will be considered first of all, for this piece of apparatus is probably the chef d'oeuvre of the assembly. The transformer consists essentially of a primary coil B, Fig. 1, of nine turns of heavy copper ribbon 2 inches wide and wound in the form of a spiral; a secondary coil of 600 turns of copper wire wound upon a wooden cylinder, S, Fig. 1; and a suitable means for holding the primary and secondary in their proper relation to each other. The secondary cylinder presents the greatest constructional problem for the amateur workman and it is suggested that this be made at the mill unless the workman is equipped with a large speed lathe. The cylinder is built up of segments of whitewood, tapered to fit around the periphery of three wooden discs, one at each end and one in the center. The entire cylinder must be assembled without the aid of nails or metal of any kind and the best course to follow is to glue the slats or segments in place and further to secure them with wooden pins covered with glue and driven into holes drilled into the wood. The cylinder is 50 inches long and 20 inches in diameter. After the assembly is completed, the surface should be turned off in the lathe and given two coats of a black vegetable 183