Lightning with Oudin Coil

(continued)

The winding on the secondary consists of 700 turns of No. 22 D. C. C. copper magnet wire, with the turns spaced 14 to the inch. This will amount to about 2,670 feet or 5.2 pounds of wire. To wind the coil pass a metal rod through the cylinder and mount it between two saw-horses. Before winding the wire on the cylinder, glue a band of one inch copper ribbon around the cylinder, one inch from the top and another placed three inches from the bottom. The bands should not meet, a space of about one inch being left between ends. Solder one end of the wire to the top band and start winding. The spacing between turns may be obtained by winding heavy cord alongside of the wire. Shellac liberally applied will hold the turns in place.

The discharge ball is of metal and about 5 inches in diameter, mounted on top of the coil. A toilet tank float will serve the purpose very well. Complete the secondary coil by connecting a wire between the metal ball and the top of the coil.

The primary coil is wound with copper or brass ribbon 1 1/2 inches wide in the form of a flat spiral. About 53 feet of the ribbon for the 21-inch outer diameter of the 10-turn spiral winding will be required. The primary supports consist of 8 pieces of fibre 8 1/2 inches long, 2 inches wide and 1 inch thick. The four top pieces have a section cut away as in the drawing so as to keep the coil from spreading. Holes are drilled in these pieces, 3/8 of an inch from the ends, large enough to permit the passage of six inch bolts.

The primary coil is mounted on a wooden base 37 inches in diameter with the four fibre pieces to support the primary located so that the primary will be in the center of the board. The supports are then bolted to the base, thus holding the primary securely in place.

Mount the secondary inside the primary coil on a wooden base 16 inches square, supported on four wooden blocks. Place the blocks so they rest flush with the edges at the corners of the board, and drill holes for a good sized bolt to pass through each corner of the board for mounting the secondary coil to the base. A piece of copper ribbon is soldered to the inside turn of the primary coil, and to the bottom of the secondary, winding, completing the coil construction.

The apparatus is now ready for connecting and operating. The wires are connected according to the diagram. For the sake of simplicity the rotating disc is omitted in the diagram of the spark gap. The spark gap motor is of course connected to the input line through a suitable switch. The wire from the secondary of the low frequency transformer is automotive high tension wire; that from the condenser should be special, heavily insulated neon sign cable, as should that also from the spark gap. GREAT CARE MUST BE TAKEN NEVER TO TOUCH THE LOW FREQUENCY TRANSFORMER. The condenser when charged will retain a considerable quantity of electricity for days, so it is well to “short” the connections for a second (with a well-insulated metal rod) before touching them. The grounded connections may be of braided ribbon or other heavy uninsulated wire connected to a water pipe. This ground should be a water pipe, never a gas pipe. Under no circumstances should the coil be operated unless this ground is established.

The coil is now ready to be set in operation. Clip the wires from the condenser and the spark gap to convenient turns of the primary of the high frequency transformer, start the spark gap motor, and turn on the power. A loud crackling noise should be heard and streamers of fire seen darting from the discharge ball. Vary the number and position of the turns used in the primary of the high frequency transformer and perhaps alter the capacity of the condenser until maximum output is obtained. Be sure that all power is shut off when these adjustments are made, and discharge the condensers as mentioned above before touching anything metallic.

Writer corrects Tesla coverage

The recent interest in inventor Nikola Tesla's contributions to civilization, although somewhat belated, is a welcome event. However, the area papers have been inaccurate in presenting the facts. Tesla has been hailed as a “Yugoslav Inventor.” This is incorrect. While it is true that he was born in a province which is now a part of Yugoslavia, Tesla neither invented anything in nor for Yugoslavia. His entire scientific creativity was carried out in the United States. Tesla was fervently patriotic and made known his devotion to his adopted country: “The papers...which conferred upon me the honor of American citizenship are stored away in a safe, while my orders, diplomas, degrees, gold medals and other distinctions are packed away in old trunks.” Tesla refused lucrative offers from foreign governments for inventions which he wanted developed here. It would be interesting to see what response might be drawn from Schenectady, if the local papers were to hail Steinmetz as a German inventor.

In addition to this misconception is the error of reporting in which Tesla is credited as being the inventor of alternating current. The principle of alternating current was known before Tesla and several single phase systems had been installed for the purpose of street and home lighting. It was not widely adopted by industry as there was no self-starting alternating current motor. Tesla's system of alternating currents included not only single phase but was equally adapted to multiphase or polyphase currents. The three phase a.c. used in heavy industry is Tesla's contribution. In addition, his system included the alternating current motor which no one prior to Tesla could make work.

Last and of least importance is reference to one news item in the local papers in which there is an incorrect spelling of Tesla's first name. His response to one such incident stated, “I wish I could turn all the forked lightning discharge in my laboratory on the fellow. After all the work I have myself done - including the Serbian translations - my name is still (mis)spelled with a “c.”

Herbert C. Force
Niagara Falls