Nikola Tesla Books
206 HIGH FREQUENCY APPARATUS Rather than attempt a minute description of each operation in the construction of these coils, the author will endeavor to cover the constructional features in each case, believing that the reader is sufficiently well-versed in mechanics to be able to read the drawings without difficulty. The construction is practically identical in the two designs and a description of one will suffice for the other. The most difficult part of the work is the building of the secondary drum indicated by 1 in the drawings. This is a wooden cylinder with wooden heads. The difficulty is found in the fact that the builder must not use metallic nails in the assembly. This is not insurmountable, however, for the shoemaker uses a substitute that fills the bill very nicely. His sharp wooden pegs may be driven like nails if the precaution is taken to start the hole with an awl or drill. If the builder has no lathe, he may order the wooden discs, which constitute the heads and intermediate forms for the cylinder, turned to size, from the mill. The wall of the cylinder is composed of wooden slats placed closely and glued and pegged to the discs. The construction will be materially assisted if holes are bored in the discs prior to assembly and a long curtain pole passed through to line them up. The pole is removed before the last few slats are placed in order that the brass bushings shown in the cylinder heads may be inserted and secured. After this, the final slats are placed in position, glued and pegged. The cylinder may next be mounted upon a pair of horses and arranged to revolve through the agency of a short length of iron rod screwed into each bushing. The rod should be flanged in back of the threaded portion to prevent the strain on the bushing that would otherwise be present. With the cylinder between horses and a staple driven over each spindle, the builder may proceed to finish off the surface. A plane run along the slats will take off
