Nikola Tesla revealed that an earthquake which drew police and ambulances to the region of his laboratory at 48 E. Houston St., New York, in 1898, was the result of a little machine he was experimenting with at the time which “you could put in your overcoat pocket”:
“I was experimenting with vibrations. I had one of my machines going and I wanted to see if I could get it in tune with the vibration of the building. I put it up notch after notch. There was a peculiar cracking sound. I asked my assistants where did the sound come from. They did not know. I put the machine up a few more notches. There was a louder cracking sound. I knew I was approaching the vibration of the steel building. I pushed the machine a little higher. “Suddenly all the heavy machinery in the place was flying around. I grabbed a hammer and broke the machine. The building would have been about our ears in another few minutes. Outside in the street there was pandemonium. The police and ambulances arrived. I told my assistants to say nothing. We told the police it must have been an earthquake. That’s all they ever knew about it.”
Some shrewd reporter asked Dr. Tesla at this point what he would need to destroy the Empire State Building and the doctor replied:
“Vibration will do anything. It would only be necessary to step up the vibrations of the machine to fit the natural vibration of the building and the building would come crashing down. That’s why soldiers break step crossing a bridge.
On the occasion of his annual birthday celebration interview by the press on July 10, 1935 in his suite at the Hotel New Yorker, Tesla announced a method of transmitting mechanical energy accurately with minimal loss over any terrestrial distance, including a related new means of communication and a method, he claimed, which would facilitate the unerring location of underground mineral deposits. At that time he recalled the earth-trembling “quake” that brought police and ambulances rushing to the scene of his Houston Street laboratory while an experiment was in progress with one of his mechanical oscillators.
Tesla's mechanical power transmission system, he dubbed it the "art of telegeodynamics," was based primarily upon his reciprocating engine invention, patent US514,169 - Reciprocating Engine - February 6, 1894. While the fundamental operating principles of Tesla's mechanical oscillator are well understood, little has been said about how the machine would have been used for underground prospecting.
The electromechanical oscillator was originally designed as a source of isochronous (that is to say, frequency stable), alternating electric current used with both wireless transmitting and receiving apparatus. In dynamical system theory an oscillator is called isochronous if the frequency is independent of its amplitude. An electromechanical device runs at the same rate regardless of changes in its drive force, so it maintains a constant frequency (hz).
Article written by Paul Eitson
I will have to give credit to Dr. Tesla for the design of the oscillator. I will however submit a crude representation of his his work. Keep in mind the diagram is not to scale, the actual piston in the oscillator moved a distance of [ 1/ " up to 3/8"]. You may notice the lower part of the fraction under the one is missing. I have not seen a book with the actual number printed so this is somewhat of a mystery to be solved. It could be as little as 1/ 1000 and the printer could not print the number.
One of the major features of the oscillator is that it could move massive weights (coils) with little energy input. This was due to the small movement of the piston combined with the spring effect produced by the piston slamming into a closed chamber. The air inside the chamber compressed and acted as a spring, forcing the piston to travel the opposite direction. At the same time this occurs the slot on the piston aligns with the inlet to allow high pressure working to propel the piston like a rocket toward the other end where it once again slams into an "air spring".
The diagram does not show the electromagnetic coil system that also controls the frequency of the piston. I will submit an additional diagram soon as I can.
Two electromagnets positioned on either side of the shaft. In the drawing the coils appear to be about one foot in diameter. The shaft has two coil pairs attached to either end which are on either side of the electromagnet fields when the shaft is at rest. When the shaft is given a slight tap, the coils are forced into the electromagnetic field. When one coil enters the field, it energizes a coil on the opposite side of the shaft producing an oscillation in the coils, somewhat similar to the oscillation produced in (oddly enough) a Tesla coil. Also similar to the Tesla coil, a capacitor arrangement is mentioned that provides electricity for the field coils.
The Inventions, Researches and Writings of Nikola Tesla - Chapter XVIII: The tesla mechanical and electrical oscillators:
On the evening of Friday, August 25, 1893, Mr. Tesla delivered a lecture on his mechanical and electrical oscillators, before the members of the Electrical Congress, in the hall adjoining the Agricultural Building, at the World's Fair, Chicago. Besides the apparatus in the room, he employed an air compressor, which was driven by an electric motor.
Mr. Tesla was introduced by Dr. Elisha Gray, and began by stating that the problem he had set out to solve was to construct, first, a mechanism which would produce oscillations of a perfectly constant period independent of the pressure of steam or air applied, within the widest limits, and also independent of frictional losses and load. Secondly, to produce electric currents of a perfectly constant period independently of the working conditions, and to produce these currents with mechanism which should be reliable and positive in its action without resorting to spark gaps and breaks. This he successfully accomplished in his apparatus, and with this apparatus, now, scientific men will be provided with the necessaries for carrying on investigations with alternating currents with great precision. These two inventions Mr. Tesla called, quite appropriately, a mechanical and an electrical oscillator, respectively.
The former is substantially constructed in the following way. There is a piston in a cylinder made to reciprocate automatically by proper dispositions of parts, similar to a reciprocating tool. Mr. Tesla pointed out that he had done a great deal of work in perfecting his apparatus so that it would work efficiently at such high frequency of reciprocation as he contemplated, but he did not dwell on the many difficulties encountered. He exhibited, however, the pieces of a steel arbor which had been actually torn apart while vibrating against a minute air cushion.
With the piston above referred to there is associated in one of his models in an independent chamber an air spring, or dash pot,
or else he obtains the spring within the chambers of the oscillator itself. To appreciate the beauty of this it is only necessary to say that in that disposition, as he showed it, no matter what the rigidity of the spring and no matter what the weight of the moving parts, in other words, no matter what the period of vibrations, the vibrations of the spring are always isochronous with the applied pressure. Owing to this, the results obtained with these vibrations are truly wonderful. Mr. Tesla provides for an air spring of tremendous rigidity, and he is enabled to vibrate big weights at an enormous rate, considering the inertia, owing to the recoil of the spring. Thus, for instance, in one of these experiments, he vibrates a weight of approximately 20 pounds at the rate of about 80 per second and with a stroke of about 7/8 inch, but by shortening the stroke the weight could be vibrated many hundred times, and has been, in other experiments.
To start the vibrations, a powerful blow is struck, but the adjustment can be so made that only a minute effort is required to start, and, even without any special provision it will start by merely turning on the pressure suddenly. The vibration being, of course, isochronous, any change of pressure merely produces a shortening or lengthening of the stroke. Mr. Tesla showed a number of very clear drawings, illustrating the construction of the apparatus from which its working was plainly discernible. Special provisions are made so as to equalize the pressure within the dash pot and the outer atmosphere. For this purpose the inside chambers of the dash pot are arranged to communicate with the outer atmosphere so that no matter how the temperature of the enclosed air might vary, it still retains the same mean density as the outer atmosphere, and by this means a spring of constant rigidity is obtained. Now, of course, the pressure of the atmosphere may vary, and this would vary the rigidity of the spring, and consequently the period of vibration, and this feature constitutes one of the great beauties of the apparatus; for, as Mr. Tesla pointed out, this mechanical system acts exactly like a string tightly stretched between two points, and with fixed nodes, so that slight changes of the tension do not in the least alter the period of oscillation.
The applications of such an apparatus are, of course, numerous and obvious. The first is, of course, to produce electric currents, and by a number of models and apparatus on the lecture platform, Mr. Tesla showed how this could be carried out in
practice by combining an electric generator with his oscillator. He pointed out what conditions must be observed in order that the period of vibration of the electrical system might not disturb the mechanical oscillation in such a way as to alter the periodicity, but merely to shorten the stroke. He combines a condenser with a self-induction, and gives to the electrical system the same period as that at which the machine itself oscillates, so that both together then fall in step and electrical and mechanical resonance is obtained, and maintained absolutely unvaried.
Next he showed a model of a motor with delicate wheelwork, which was driven by these currents at a constant speed, no matter what the air pressure applied was, so that this motor could be employed as a clock. He also showed a clock so constructed that it could be attached to one of the oscillators, and would keep absolutely correct time. Another curious and interesting feature which Mr. Tesla pointed out was that, instead of controlling the motion of the reciprocating piston by means of a spring, so as to obtain isochronous vibration, he was actually able to control the mechanical motion by the natural vibration of the electro-magnetic system, and he said that the case was a very simple one, and was quite analogous to that of a pendulum. Thus, supposing we had a pendulum of great weight, preferably, which would be maintained in vibration by force, periodically applied; now that force, no matter how it might vary, although it would oscillate the pendulum, would have no control over its period.
Mr. Tesla also described a very interesting phenomenon which he illustrated by an experiment. By means of this new apparatus, he is able to produce an alternating current in which the e. m. f. of the impulses in one direction preponderates over that of those in the other, so that there is produced the effect of a direct current. In fact he expressed the hope that these currents would be capable of application in many instances, serving as direct currents. The principle involved in this preponderating e. m. f. he explains in this way: Suppose a conductor is moved into the magnetic field and then suddenly withdrawn. If the current is not retarded, then the work performed will be a mere fractional one; but if the current is retarded, then the magnetic field acts as a spring. Imagine that the motion of the conductor is arrested by the current generated, and that at the instant when it stops to move into the field, there is still the
maximum current flowing in the conductor; then this current will, according to Lenz's law, drive the conductor out of the field again, and if the conductor has no resistance, then it would leave the field with the velocity it entered it. Now it is clear that if, instead of simply depending on the current to drive the conductor out of the field, the mechanically applied force is so timed that it helps the conductor to get out of the field, then it might leave the field with higher velocity than it entered it, and thus one impulse is made to preponderate in e. m. f. over the other.
With a current of this nature, Mr. Tesla energized magnets strongly, and performed many interesting experiments bearing out the fact that one of the current impulses preponderates. Among them was one in which he attached to his oscillator a ring magnet with a small air gap between the poles. This magnet was oscillated up and down 80 times a second. A copper disc, when inserted within the air gap of the ring magnet, was brought into rapid rotation. Mr. Tesla remarked that this experiment also seemed to demonstrate that the lines of flow of current through a metallic mass are disturbed by the presence of a magnet in a manner quite independently of the so-called Hall effect. He showed also a very interesting method of making a connection with the oscillating magnet. This was accomplished by attaching to the magnet small insulated steel rods, and connecting to these rods the ends of the energizing coil. As the magnet was vibrated, stationary nodes were produced in the steel rods, and at these points the terminals of a direct current source were attached. Mr. Tesla also pointed out that one of the uses of currents, such as those produced in his apparatus, would be to select any given one of a number of devices connected to the same circuit by picking out the vibration by resonance. There is indeed little doubt that with Mr. Tesla's devices, harmonic and synchronous telegraphy will receive a fresh impetus, and vast possibilities are again opened up.
Mr. Tesla was very much elated over his latest achievements, and said that he hoped that in the hands of practical, as well as scientific men, the devices described by him would yield important results. He laid special stress on the facility now afforded for investigating the effect of mechanical vibration in all directions, and also showed that he had observed a number of facts in connection with iron cores.
Large electromagnetically controlled mechanical oscillator for generating isochronous oscillations, used in demonstration before the Electrical Congress at the Chicago World's Fair, August 25,
1893. Illustrated in Martin book, Fig 312, p.490.
Here is an actual picture of the electro-mechanical oscillator. Note the size of the field magnets. They were constructed of numerous flat sheets of iron. Using flat sheets of iron, as opposed to a single piece of iron, increases the magnetic field. Recent research with permanent magnets and permanent magnet, electromagnetic combinations could greatly increase the work done by the oscillator. In Dr. Tesla's machine, current is provided for the field coils by the generator. By using a permanent or combination magnet arrangement current for the field coils could be reduced, resulting in a greater output.
Motion of the piston was controlled in three different methods. Connecting the coil pairs on either end of the shaft, forces the coil on the opposite end into the field when it is at full charge, resulting in the coil being repelled from the field at the same speed it enters the field. The motion of the shaft is also reversed mechanically by both the air spring and pressure from the working fluid. Either steam or air can be used to drive the piston. If steam is used, a vacuum is created when the steam enters the jacket and condenses. The vacuum created at the outlet pulls the piston in addition to the steam push on the other end. The most important part of the picture cannot be illustrated but can demonstrated. The resonant frequency of the machine could be adjusted to match the resonant frequency of any object.
Dr. Tesla was able to match the resonant frequency of objects in the room by adjusting either the electrical or mechanical movement of the piston. He was able to identify different objects in a circuit by matching their resonant frequency. The mechanical oscillator had to be mounted on wooden blocks to help damp vibration. Dr. Tesla also showed parts of a steel arbor that had been torn apart with one of his oscillators.
The Inventions, Researches and Writings of Nikola Tesla - Chapter XVIII: The tesla mechanical and electrical oscillators:
The engraving, Fig. 312, shows, in perspective, one of the forms of apparatus used by Mr. Tesla in his earlier investigations in this field of work, and its interior construction is made plain by the sectional view shown in Fig. 313. It will be noted that the piston P is fitted into the hollow of a cylinder C which is provided with channel ports O O, and I, extending all around the inside surface. In this particular apparatus there are two channels O O for the outlet of the working fluid and one, I, for the inlet. The piston P is provided with two slots S S' at a carefully determined distance, one from the other. The tubes T T which are screwed into the holes drilled into the piston, establish communication between the slots S S' and chambers on each side of the piston, each of these chambers connecting with the slot which is remote from it. The piston P is screwed tightly on a shaft A
which passes through fitting boxes at the end of the cylinder C. The boxes project to a carefully determined distance into the hollow of the cylinder C, thus determining the length of the stroke.
Surrounding the whole is a jacket J. This jacket acts chiefly to diminish the sound produced by the oscillator and as a jacket when the oscillator is driven by steam, in which case a somewhat different arrangement of the magnets is employed. The apparatus here illustrated was intended for demonstration purposes, air being used as most convenient for this purpose.
A magnetic frame M M is fastened so as to closely surround the oscillator and is provided with energizing coils which establish two strong magnetic fields on opposite sides. The magnetic frame is made up of thin sheet iron. In the intensely concentrated field thus produced, there are arranged two pairs of coils H H supported in metallic frames which are screwed on the shaft A of the piston and have additional bearings in the boxes B B on each side. The whole is mounted on a metallic base resting on two wooden blocks.
The Inventions, Researches and Writings of Nikola Tesla - Chapter XVIII: The tesla mechanical and electrical oscillators:
The operation of the device is as follows: The working fluid being admitted through an inlet pipe to the slot I and the piston being supposed to be in the position indicated, it is sufficient, though not necessary, to give a gentle tap on one of the shaft
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
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.
Immediately after the destruction of my laboratory by fire, the first thing I did was to design this oscilator (shown in fig. 27). I was still recognizing the absolute necessity of
producing isochronous oscilations, and I could not get it with the alternator, so I constructed this machine. That was all a very expensive piece of work. It comprised four engines. Those four
engines were put in pairs and there was an isochronous controller in the center, and furthermore, that controller was so arranged that I could set two pairs of engines to any phase or produce any
beat I desired. Usually I operated quarter phase ; this is, I generated currents of 90º displacement.
By the way, now, for a first time you see my apparatus om Houston street, which I used for obtaining oscillations, damped and undamped as well . But it was necessary to state that while
others, who had been using my apparatus, but without my experience, have produced with it damped oscillations, my oscillations were almost invariably continuous, or undamped, because my
circuits were so designed that they have a very small damping factor. Even if I operated with very low frequencies, I allways obtained continuous, or undamped, waves for the reason that I
designed my circuits as nonradiative circuits.
In this diagram (Fig. 28) I show the general arrangement of these engines installed in the laboratory at 46 E. Houston Street. There were four, with four vibrating parts installed for
furnishing isochronous currents of desired wave frequencies, phases and beats.
Unique Alternating Current Generator or Exciting Tesla's Early "Beat" Receptor. Actuated by Comprest Air or Steam Which Vibrates a Special Diafram-Coil.
"That oscillator (Fig. 29) was one of high frequency for isochronous work, and I used it in many ways. The machine, you see, comprised a magnetic frame. The energizing coil, which is removed, produced a strong magnetic field in this region. I calculated the dimensions of the field to make it as intense as possible. There was a powerful tongue of steel which carried a conductor at the extreme end. When it was vibrated, it generated oscillations in the wire. The tongue was so rigid that a special arrangement was provided for giving it a blow; then it would start, and the air pressure would keep it going. The vibrating mechanical system would fall into synchronism with the electrical, and I would get isochronous currents from it. That was a machine of high frequency that emitted a note about like a mosquito. It was something like 4,000 or 5,000. It gave a pitch nearly that of my alternator of the (first) type which I have described.
Of course this device was not intended for a big output, but simply to give me, when operating in connection with receiving circuits, isochronous currents. The excursions of the tongue were so small that one could not see it oscillate, but when the finger was pressed against it the vibration was felt".
This drawing (Fig. 30) shows the construction in detail. Here is the field coil, here are teh conductors in the intense field, the valves for air supply, and the stops for limiting vibration.
The stronger the field was excited, the stronger the vibration became, but just the same, while the amplitude changed, the isochronism was not disturbed.
I want to say now why these machines were the means of obtaining the best results in the wireless work. The machine at the Houston Street laboratory with which I could obtain any difference
of phase, as well as that machine at 35 Soth Fifth Avenue, were the means of running a motor in perfect isochronism. That is, if I connected a synchronous motor to these machines and drove it
with currents of different phase, I obtained an absolutely uniform rotation, constant in time, and when I coupled this motor directly to an alternator, I obtained from the latter currents of
absolutely constant frequency, all the more readily as I tuned the circuit of the alternator to the same frequency.
These machines described in the general way only. The work has covered years, and it would take a long time to explain all about them. They enabled me to operate in whatever I did with
currents of constant frequency, and the small alternators in my experiments were driven in this way. While this work was going on, I was perfecting other ways of generating electric oscillations
of absolutely constant frequency which were then not producible in that art.
US514,169 - Reciprocating Engine, February 6, 1894
Latest form of Tesla oscillator, combining in one mechanism the dynamo and steam engine. Double compound mechanical and electrical oscilator for generating current of perfect, constant, dynamo
frequency of 10 horsepower (Tesla’s Oscillator and Other
Inventions by Thomas Commerford Martin - Century Magazine - April, 1895 - Fig. 2,
Tesla’s Oscillator and Other Inventions by Thomas Commerford Martin - Century Magazine - April, 1895
Up to this point we have been considering both continuous-current and alternating-current dynamos as driven by the ordinary steam-engine. Perhaps nine tenths of all the hundreds of thousands of dynamos in the world to-day are so operated, the remainder being driven by water-wheels, gas-engines, and compressed air.
Now, each step from consuming the coal under the boilers that deliver steam to the engines, up to the glow of the filament in an incandescent lamp, is attended with loss. As in every other cycle that has to do with heat transformation, the energy is more or less frittered away, just as in July the load in an iceman’s cart crumbles and melts in transit along the street. Actual tests prove that the energy manifesting itself as light in an incandescent lamp is barely five per cent. of that received as current. In the luminosity of a gas flame the efficiency is even smaller. Professor Tyndall puts the useful light-waves of a gas flame at less than one per cent. of all the waves caused by the combustion going on in it. If we were dealing with a corrupt city government, such wretched waste and inefficiency would not be tolerated; and in sad reality the extravagance is but on a par with the wanton destruction of whole forests for the sake of a few sticks of lumber. Armies of inventors have flung themselves on the difficulties involved in these barbaric losses occurring at every stage of the calorific, mechanical, and electric processes; and it is indeed likely that many lines of improvement have already been compelled to yield their utmost, reaching terminal forms. A moment’s thought will show that one main object must be the elimination of certain steps in the transfer of the energy; and obviously, if engine and dynamo both have large losses, it will be a gain to merge the two pieces of apparatus. The old-fashioned electric-light station or street-railway power-house is a giddy maze of belts and shafting; in the later plants engine and dynamo are coupled directly together on one base. This is a notable stride, but it still leaves us with a dynamo in which some part of the wire wound on it is not utilized at every instant, and with an engine of complicated mechanism. The steam-cylinder, with its piston, is the only thing actually doing work, and all the rest of the imposing collection of fly-wheel, governor-balls, eccentrics, valves, and what not, is for the purpose of control and regulation.
In his oscillator Mr. Tesla, to begin with, has stripped the engine of all this governing mechanism. By giving also to the coils in which the current is created as they cut the “lines of force” of the magnets, a to-and-fro or reciprocating motion, so that the influence on them is equal in every direction, he has overcome the loss of the idle part of the wire experienced in rotating armatures; and, moreover, greatest achievement of all, he has made the currents regulate the mechanical motions. No matter how close the governing of the engine that drives the ordinary dynamo, with revolving armature, there is some irregularity in the generation of current. In the Tesla oscillator, if its inventor and the evidence of one’s eyes may be believed, the vibrations of the current are absolutely steady and uniform, so that one could keep the time o’ day with the machine about as well as with a clock. It was this superlative steadiness of the vibration or frequency that Mr. Tesla aimed at, for one thing. The variations caused by the older apparatus might be slight, but minute errors multiplied by high rates of occurrence soon become perceptible, and militate against desirable uniformity and precision of action. Back of the tendencies to irregularity in the old-fashioned electrical apparatus were the equal or greater tendencies in the steam-engine; and over and above all were the frightful losses due to the inefficient conversion in both of the power released from the fuel under the boiler generating the steam.
Gain in one direction with a radical innovation usually means gain in many others, through a growing series. I confess I do not know which of the advantages of the oscillator to place first; and I doubt whether its inventor has yet been able to sit down and sum up all the realities and possibilities to which it is a key. One thing he does: he presses forward. Our illustration, Fig. 2, shows one of his latest forms of oscillator in perspective, while the diagram, Fig. 1, exhibits the internal mechanism of one of the early forms. Fig. 2 will serve as a text for the subsequent heads of discourse. The steam-chest is situated on the bed-plate between the two electromagnetic systems, each of which consists of field coils between which is to move the armature or coil of wire. There are two pistons to receive the impetus of the incoming steam in the chest, and in the present instance steam is supplied at a pressure of 350 pounds, although as low as 80 is also used in like oscillators, where steam of the higher pressure is not obtainable. We note immediately the absence of all the governing appliances of the ordinary engine. They are non-existent. The steamchest is the engine, bared to the skin like a prizefighter, with every ounce counting. Besides easily utilizing steam at a remarkably high pressure, the oscillator holds it under no less remarkable control, and, strangest of all, needs no packing to prevent leak. It is a fair inference, too, that, denuded in this way of superfluous weight and driven at high pressure, the engine must have an economy far beyond the common. With an absence of friction due to the automatic cushioning of the light working parts, it is also practically indestructible. Moreover, for the same pressure and the same piston speed the engine has about one thirtieth or one fortieth of the usual weight, and occupies a proportionately smaller space. This diminution of bulk and area is equally true of the electrical part. The engine-pistons carry it their ends the armature coils, and these they thrust reciprocatively in and out of the magnetic field of the field coils, thus generating current by their action.
Double compound mechanical and electrical oscilator for generating current of perfect, constant dynamic frequency current of 10 Horse power, built in 1893. (Article by Martin - "Tesla's oscilator and other inventions" Century Magazine April 1895, Fig. 2, Pg.921.
If one watches any dynamo, it will be seen that the coils constituting the “armature” are swung around in front of magnets, very much as a turnstile revolves inside the barricading posts; and the current that goes out to do work on the line circuit is generated inductively in the coils, because they cut lines of influence emanating from the ends of the magnets, and forming what has been known since Faraday’s time as the “field of force.” In the Tesla oscillator, the rotary motion of the coils is entirely abandoned, and they are simply darted to and fro at a high speed in front of the magnets, thus cutting the lines of the “field of force” by shooting in and out of them very rapidly, shuttle-fashion. The great object of cutting as many lines of an intense field of force as swiftly, smoothly, regularly, and economically as possible is thus accomplished in a new and, Mr. Tesla believes, altogether better way. The following description of remarkable new phenomena in electricity will justify him in regarding the oscillator as an extremely valuable instrument of research, while time will demonstrate its various commercial and industrial benefits.
Diagramatic representation of double compound mechanical and electrical oscilator for generating currents of perfectly dynamo frequency. Shows mechanical and electrical parts.