The Inventions, Researches and Writings of Nikola Tesla

position indicated, it is sufficient, though not necessary, to give a gentle tap on one of the shaft[Pg 492] ends protruding from the boxes B. Assume that the motion imparted be such as to move the piston to the left (when looking at the diagram) then the air rushes through the slot S' and tube T into the chamber to the left. The pressure now drives the piston towards the right and, owing to its inertia, it overshoots the position of equilibrium and allows the air to rush through the slot S and tube T into the chamber to the right, while the communication to the left hand chamber is cut off, the air of the latter chamber escaping through the outlet O on the left. On the return stroke a similar operation takes place on the right hand side. This oscillation is maintained continuously and the apparatus performs vibrations from a scarcely perceptible quiver amounting to no more than 1 of an inch, up to vibrations of a little over 3/8 of an inch, according to the air pressure and load. It is indeed interesting to see how an incandescent lamp is kept burning with the apparatus showing a scarcely perceptible quiver. To perfect the mechanical part of the apparatus so that oscillations are maintained economically was one thing, and Mr. Tesla hinted in his lecture at the great difficulties he had first encountered to accomplish this. But to produce oscillations which would be of constant period was another task of no mean proportions. As already pointed out, Mr. Tesla obtains the constancy of period in three distinct ways. Thus, he provides properly calculated chambers, as in the case illustrated, in the oscillator itself; or he associates with the oscillator an air spring of constant resilience. But the most interesting of all, perhaps, is the maintenance of the constancy of oscillation by the reaction of the electromagnetic part of the combination. Mr. Tesla winds his coils, by preference, for high tension and associates with them a condenser, making the natural period of the combination fairly approximating to the average period at which the piston would oscillate without any particular provision being made for the constancy of period under varying pressure and load. As the piston with the coils is perfectly free to move, it is extremely susceptible to the influence of the natural vibration set up in the circuits of the coils H H. The mechanical efficiency of the apparatus is very high owing to the fact that friction is reduced to a minimum and the weights which are moved are small; the output of the oscillator is therefore a very large one. Theoretically considered, when the various advantages which Mr. Tesla holds out are examined, it is surprising, considering the simplicity of the arrangement, that nothing was done in this[Pg 493] direction before. No doubt many inventors, at one time or other, have entertained the idea of generating currents by attaching a coil or a magnetic core to the piston of a steam engine, or generating currents by the vibrations of a tuning fork, or similar devices, but the disadvantages of such arrangements from an engineering standpoint must be obvious. Mr. Tesla, however, in the introductory remarks of his lecture, pointed out how by a series of conclusions he was driven to take up this new line of work by the necessity of producing currents of constant period and as a result of his endeavors to maintain electrical oscillation in the most simple and economical manner. FOOTNOTES [1] A lecture delivered before the American Institute of Electrical Engineers, at Columbia College, N. Y., May 20, 1891. [2] Lecture delivered before the Institution of Electrical Engineers, London, February, 1892. [3] A lecture delivered before the Franklin Institute, Philadelphia, February, 1893, and before the National Electric Light Association, St. Louis, March, 1893. [4] See pages 153-4 5. [5] It is thought necessary to remark that, although the induction coil may give quite a good result when operated with such rapidly alternating currents, yet its construction, quite irrespective of the iron core, makes it very unfit for such high frequencies, and to obtain the best results the construction should be greatly modified. [6] Article by Mr. Tesla in The Electrical Engineer, N. Y., May 6, 1891. [7] Article by Mr. Tesla in The Electrical Engineer of Dec. 23d, 1891. [8] Article by Mr. Tesla in The Electrical Engineer. N. Y., July 1, 1891. [9] Abstract of a paper read before Physical Society of London. [9] Article by Mr. Tesla in The Electrical Engineer, N. Y., August 26, 1891. [10] Note by Prof. J. J. Thomson in the London Electrician, July 24, 1891. [11] Mr. Tesla's experiments, as the careful reader of his three lectures will perceive, have revealed a very important fact which is taken advantage of in this invention. Namely, he has shown that in a condenser a considerable amount of energy may be wasted, and the condenser may break down merely because gaseous matter is present between the surfaces. A number of experiments are described in the lectures, which bring out this fact forcibly and serve as a guide in the operation of high tension apparatus. But besides bearing upon this point, these experiments also throw a light upon investigations of a purely scientific nature and explain now the lack of harmony among the observations of various investigators. Mr. Tesla shows that in a fluid such as oil the losses are very small as compared with those incurred in a gas. [12] It will, of course, be inferred from the nature of these devices that the vibration obtained in this manner is very slow owing to the inability of the iron to follow rapid changes in temperature. In an interview with Mr. Tesla on this subject, the compiler learned of an experiment which will interest students. A simple horseshoe magnet is taken and a piece of sheet iron bent in the form of an L is brought in contact with one of the poles and placed in such a position that it is kept in the attraction of the opposite pole delicately suspended. A spirit lamp is placed under the sheet iron piece and when the iron is heated to a certain temperature it is easily set in vibration oscillating as rapidly as 400 to 500 times a minute. The experiment is very easily performed and is interesting principally on account of the very rapid rate of vibration. [13] The chief point to be noted is that Mr. Tesla attacked this problem in a way which was, from the standpoint of theory, and that of an engineer, far better than that from which some earlier trials in this direction started. The enlargement of these ideas will be found in Mr. Tesla's work on the pyromagnetic generator, treated in this chapter. The chief effort of the inventor was to economize the heat, which was accomplished by inclosing the iron in a source of heat well insulated, and by cooling the iron by means of steam, utilizing the steam over again. The construction also permits of more rapid magnetic changes per unit of time, meaning larger output. [14] The compiler has learned partially from statements made on several occasions in journals and partially by personal inquiry of Mr. Tesla, that a great deal of work in this interesting line is unpublished. In these inventions as will be seen, the brushes are automatically shifted, but in the broad method barely suggested here the regulation is effected without any change in the position of the brushes. This auxiliary brush invention, it will be remembered, was very much discussed a few years ago, and it may be of interest that this work of Mr. Tesla, then unknown in this field, is now brought to light. [15] Article by Mr. Tesla, contributed to The Electrical Engineer, N. Y., Sept. 2, 1891. [16] Mr. Tesla here refers to an interesting article which appeared in July, 1865, in the Phil. Magazine, by Sir W. Thomson, in which Sir William, speaking of his "uniform electric current accumulator," assumes that for self-excitation it is desirable to subdivide the disc into an infinite number of infinitely thin spokes, in order to prevent diffusion of the current. Mr. Tesla shows that diffusion is absolutely necessary for the excitation and that when the disc is subdivided no excitation can occur. [17] See Part I, Chap. III, page 9. [18] See Part II, Chap. XXVI., page 145. [Pg 494] INDEX. Alternate Current Electrostatic Apparatus392 Alternating Current Generators for High Frequency152, 374, 224 Alternating Motors and Transformers7 American Institute Electrical Engineers Lecture145 Anthony, W. A., Tests of Tesla Motors8 Apparatus for Producing High Vacua276 Arc Lighting, Tesla Direct, System451 Auxiliary Brush Regulation438 Biography, Tesla4 Brush, Anti-Sparking432 Brush, Third, Regulation438 Brush, Phenomena in High Vacuum226 Carborundum Button for Tesla Lamps140, 253 Commutator, Anti-Sparking432 Combination of Synchronizing and Torque Motor95 Condensers with Plates in Oil418 Conversion with Disruptive Discharge193, 204, 303 Current or Dynamic Electricity Phenomena327 Direct Current Arc Lighting451 Dischargers, Forms of305 Disruptive Discharge Coil207, 221 Disruptive Discharge Phenomena212 Dynamos, Improved Direct Current448 Early Phase Motors477 Effects with High Frequency and High Potential Currents119 Electrical Congress Lecture, Chicago486 Electric Resonance340 Electric Discharges in Vacuum Tubes396 Electrolytic Registering Meter420 Eye, Observations on the294 Flames, Electrostatic, Non-Consuming166, 272 Forbes Unipolar Generator468, 474 Franklin Institute Lecture294 Generators, Pyromagnetic429 High Potential, High Frequency: Brush Phenomena in High Vacuum226 Carborundum Buttons140, 253 Disruptive Discharge Phenomena212 Flames, Electrostatic, Non-Consuming166, 272 Impedance, Novel Phenomena194, 338 Lighting Lamps Through Body359 Luminous Effects with Gases368 "Massage" with Currents394 Motor with Single Wire234, 330 "No Wire" Motors235 Oil Insulation of Induction Coils173, 221 [Pg 495]Ozone, Production of171 Phosphorescence367 Physiological Effects162, 394 Resonance340 Spinning Filament168 Streaming Discharges of High Tension Coil155, 163 Telegraphy without Wires346 Impedance, Novel Phenomena194, 338 Improvements in Unipolar Generators465 Improved Direct Current Dynamos and Motors448 Induction Motors92 Institution Electrical Engineers Lecture198 Lamps and Motor operated on a Single Wire330 Lamps with Single Straight Fiber183 Lamps containing only a Gas188 Lamps with Refractory Button177, 239, 360 Lamps for Simple Phosphorescence187, 282, 364 Lecture, Tesla before: American Institute Electrical Engineers145 Royal Institution124 Institution Electrical Engineers198 Franklin Institute and National Electric Light Association294 Electrical Congress, Chicago486 Lighting Lamps Through the Body359 Light Phenomena with High Frequencies349 Luminous Effects with Gases at Low-Pressure368 "Magnetic Lag" Motor67 "Massage" with Currents of High Frequency394 Mechanical and Electrical Oscillators486 Method of obtaining Direct from Alternating currents409 Method of obtaining Difference of Phase by Magnetic Shielding71 Motors: With Circuits of Different Resistance79 With Closed Conductors9 Combination of Synchronizing and Torque95 With Condenser in Armature Circuit101 With Condenser in one of the Field Circuits106 With Coinciding Maxima of Magnetic Effect in Armature and Field83 With "Current Lag" Artificially Secured58 Early Phase477 With Equal Magnetic Energies in Field and Armature81 Or Generator, obtaining Desired Speed of36 Improved Direct Current448 Induction92 "Magnetic Lag"67 "No Wire"235 With Phase Difference in Magnetization of Inner and Outer Parts of Core88 Regulator for Rotary Current45 Single Circuit, Self-starting Synchronizing50 Single Phase76 With Single Wire to Generator234, 330 Synchronizing9 Thermo-Magnetic424 Utilizing Continuous Current Generators31 National Electric Light Association Lecture294 "No Wire" Motor235 Observations on the Eye294 Oil, Condensers with Plates in418 Oil Insulation of Induction Coils173, 221 Oscillators, Mechanical and Electrical486 [Pg 496]Ozone, Production of171 Phenomena Produced by Electrostatic Force318 Phosphorescence and Sulphide of Zinc367 Physiological Effects of High Frequency162, 394 Polyphase Systems26 Polyphase Transformer109 Pyromagnetic Generators429 Regulator for Rotary Current Motors45 Resonance, Electric, Phenomena of340 "Resultant Attraction"7 Rotating Field Transformers9 Rotating Magnetic Field9 Royal Institution Lecture124 Scope of Lectures119 Single Phase Motor76 Single Circuit, Self-Starting Synchronizing Motors50 Spinning Filament Effects168 Streaming Discharges of High Tension Coil155, 163 Synchronizing Motors9 Telegraphy without Wires346 Transformer with Shield between Primary and Secondary113 Thermo-Magnetic Motors424 Thomson, J. J., on Vacuum Tubes397, 402, 406 Thomson, Sir W., Current Accumulator471 Transformers: Alternating7 Magnetic Shield113 Polyphase109 Rotating Field9 Tubes: Coated with Yttria, etc.187 Coated with Sulphide of Zinc, etc.290, 367 Unipolar Generators465 Unipolar Generator, Forbes468, 474 Yttria, Coated Tubes187 Zinc, Tubes Coated with Sulphide of367