The boy's own book of great inventions

Preface

The purpose of this book is to tell the story of some few of the great epoch-making inventions, to trace their influence upon world progress and to describe, so far as possible, simple experiments, embodying the principles involved, for home laboratory work. Many very important inventions and discoveries have had to be omitted. The field to be covered is so broad and the limits of a single book so narrow that the selection of subject-matter has been of necessity largely a process of judicious elimination. But in a book of this sort it is not so important what particular subjects are discussed as it is to teach certain fundamental truths and to emphasize the tremendous influence upon human affairs of the so-called dreamer, the man of vision, who in spite of every obstacle of fate and man has blazed the path of progress for the race. We cannot point out too often that genius is very frequently but another name for imagination. The inventor and the poet are in spirit one. The poet creates a mental image and clothes it in words suggestive of the thought picture. The inventor conceives the idea of an instrument, fraught with great material possibihties, and embodies it in a suitable mechanism. Both the poem and the machine, as everything else in the universe, are mental creations. The most intricate piece of machinery existed in the mind of the inventor before it could be translated into visible and tangible form. But in every instance the thinking of the inventor must be true to the eternal laws of the universe if bis creation is vi Preface

to have meaning and purpose in it. The inventor's roincl is a mirror of universal truths and if his thinking does not reflect them as they are, the product is distortion, error and failure. Some few great minds have caught the vision of a small portion of the truths of Nature and have materialized them for the benefit of mankind. But there is still an ocean of almost infinite possibility for the inventor. The age of discovery and achievement has only just begun and we may be perfectly sure that, so long as the race is here, there will yet be progress to make. Surely the miracles of Science have not all been wrought.

The writer is under obligation to a large number of business organizations for their kindness in supplying photographs and material used in the preparation of the book. He wishes especially to acknowledge his indebtedness to his wife for making more than two-thirds of the drawings for the line cuts and for typing the manuscript. Credit is also due to Miss Beatrice Booraem for a part of the drawings used in the cuts.

Floyd L. Darrow.

Brooklyn, N. Y.,

Contents

PAGE

Preface v

Chapter

Chapter I

We are all acquainted with the spinning top vender who, on the crowded street corner, at the automobile show or country fair, displays his wares and demonstrates to a curious and credulous group how his uncanny gyros utterly defy the law of gravity, and tells you that no scientist wise enough to explain their action has yet appeared.

But gyroscopic action is as old as the universe itself Do you know that the earth beneath your feet is a huge gyroscope ceaselessly obeying the same laws as the spinning top? The rolling hoop which as a child led you many a merry chase owes its balancing power to these self-same laws. At once the plaything of children and the marvel of sages, who of us Kttle more than a decade ago would have imagined that within this toy lay hidden the possibilities of the mono-rail car, a gyro-compass of absolute reliability and infinitely more accurate than the magnetic, an automatic aeroplane stabilizer, a means of steadying a ship in the roughest sea, a steering device for the torpedo and perfect proof of the earth's rotation? Do you realize that the wonderful stability of your wheel or motorcycle is due solely to the principle of the spinning top and that it is the gyroscopic action of a swiftly rotating bullet that carries it straight to the mark? Do you know, too, that the pole star of to-day is not the pole star of ten thousand years ago nor will it continue to be the pole star of the future? And this because of the gyroscopic movement of the earth as it spins on its axis and at the same time whirls about the sun. Far from being a puzzle the gyroscope admits of both mathematical and popular explanation. Its marvelous balancing power is one of the most striking illustrations of the fundamental law of inertia, the most common property of all matter. Inertia means inactivity. A body at rest tends to remain at rest or if in motion to continue in motion unless acted upon by an outside force.

This is a matter of common experience. As we endeavor to keep our balance in a swiftly moving subway train with its sudden changes of motion and bending about sharp curves, we get a very vivid realization of the opposition which a body offers to any change in its state of rest or motion. The distance to which the athlete throws the discus is determined by the quantity of inertia which he can store up in it as he whirls the circular plate about his head. When he throws it, too, he simply lets go and the inertia of the moving discus carries it off in a straight line tangent to the curve in which it moves. The inertia stored up in a massive flywheel keeps the machinery running smoothly and without vibration. A moving train does not stop when the power is turned off but only when the brakes have been appHed and the friction and air resistance have overcome its momentum, and momentum is simply the inertia of a moving body. The earth rotates on its axis and revolves around the sun with no change in its velocity because it meets with no resistance and is itself powerless to accelerate or retard its motion. Its inertia keeps it going. So with our top, or gyroscope. When set spinning it resists with a force, altogether greater than would be expected from its size and weight, any tendency to change its plane of rotation, or the direction in which its axis points. This is simply the inertia of a rotating body and its magnitude depends upon the mass and speed of the body. The swiftly turning wheels of a motorcycle resist with a tremendous force any change in their plane of rotation and therefore balance themselves and rider in perfect security.

To better study the laws of rotating bodies I made a gyroscope from a bicycle wheel and operated it with an electric motor. On one side of the hub I brazed a clutch similar to that of an automobile crank. I extended the cone shaft about two and one-haK feet by boring and threading a hole in the end of a steel rod and screwing this onto the projecting end of the shaft. This was made secure with a set-screw. About midway of the bar a socket was bored to provide for mounting the spinning wheel upon the upright support. A chuck and holder to fit the end of the motor shaft were provided so as to engage the clutch in speeding up the gyroscope. I weighted the rim with a large number of turns of copper wire, holding it in place with copper bands, and trued the wheel about the shaft perfectly with small quantities of solder placed wherever needed on the rim. The heavier the rim the less will be the speed required, but a fellow experimenter in using lead for this purpose found that as he speeded up the wheel the lead began to leave the rim and he very prudently began to leave the room.

In making a demonstration the operator holds the clutch of the gyroscope firmly against the chuck on the end of the motor shaft and his assistant gradually speeds up the motor. When a fairly high speed has been attained the gyroscope is withdrawn and mounted upon the support as shown in the cut. Instead of falling, however, the end of the shaft bearing the wheel stands slightly above the horizontal and the gyroscope at once begins to revolve, or ''precess" about the vertical support, seeming to the popular mind completely to defy the law of gravity. As the speed of the wheel dies down its axis slowly drops to the horizontal, then below and gradually the action ceases. If the wheel be operated in the opposite direction the same phenomenon occurs except that the precession is also in the opposite direction. Holding the rapidly rotating gyroscope in the hands one experiences no difhculty in moving it in any direction so long as the plane of rotation is not changed. But attempt to disturb this and a tremendous resistance at once develops. One seemingly wrestles with a giant. We are opposing the inertia of a rotating body and find that it is very great. Once set spinning in a certain plane our gyroscope continues to rotate in that plane with all the momentum it possesses.

But why does the gyroscope precess? Why does it not fall? Far from being in defiance of the law of gravity it is on the contrary because of this law that the gyroscope behaves as it does. A body that is under the influence of two forces or two motions at the same time can never act as though it were under the influence of only one. And this is just what the popular mind does not take into account. Our gyroscope is made to rotate about one axis and it will be readily apparent that the gravitation of the earth tends to rotate it about another axis at right angles to the first. Therefore the gyroscope can rotate about neither axis as though the other rotation were absent, but must tend to rotate about an axis lying between the two. In trying to place itself parallel with this intermediate axis the gyroscope begins to revolve, or precess as it is called, but in so doing

Speeding up the gyroscope.

Demonstrating the precessional movement of the gyroscope.

the direction of each axis shifts, and so long as the speed of the gyroscope keeps up its own axis will continually chase this intermediate axis about the vertical support but never catch up with it. Were there no gravitational force our gyroscope would rotate with its axis at right angles to the support but there would be no precession. This is conclusively shown by placing a counterpoise on the free arm of the gyroscope

shaft just sufficient to balance Fig. i.— In the above diagram the

the weight of the wheel when the precession immediately ceases. Thus when the force of gravity is neutralized the gyroscopic action disappears. If the counterpoise is moved to the end of the shaft causing the wheel to move upward, precession at once begins again but is in the opposite direction.

After such a demonstration even the most skeptical could never assert that the gyroscope suspends the law of gravity.

The earth itself affords one of wheel is rotating about axis AB and at the same time the force of gravity is tending to pull it downward along arc BE and about axis AD.

Therefore the wheel being under the influence of two curvilinear motions tends to move forward so that its axis of rotation will coincide with the intermediate axis AC and in so doing begins to "precess." As the wheel precesses, however, both axes AB and AD also move forward and with them axis AC thus causing the precessional movement to continue so long as the wheel continues to rotate.

the most perfect examples of gyroscopic action. Because of the earth's constant rotation its axis with slight variation points in the same direction from century to century. It is simply a spinning top. At the same time that it rotates on its axis, however, it is re-

6 The Boys^ Ow}i Book of Great Inventions

volving around another axis in its annual movement about the sun. The two axes are inclined at an angle of 23 3^ degrees to each other and therefore just as our gyroscope precesses so does the earth. It is continually endeavoring to place its axis parallel to the axis of its orbit but with no better success than the gyroscope. But the precessional movement which results, constantly shifts westward the equinotial points, where the sun crosses the equator, at the rate of 55 seconds of arc each year and causes the axis of the earth to describe a small circle in the heavens completing it once each cycle of 25,900 years. In other words the earth wobbles just as a top does in dying down. This accounts for the former statement that the pole star is not constant.

One of the more recent and probably the most important appHcation of the gyroscope is in the gyro-compass. This compass is now a part of the equipment of all modern battleships and submarines in the various navies of the world and it is a matter of no Httle pride to Americans that an American inventor, Mr. Ehner A. Sperry of Brooklyn, has contributed most toward the perfection of this marvelous piece of mechanism.

In order to understand the action of the gyro-compass suppose we carry a gyroscope, mounted similarly to the one shown in the cut, to the North Pole. Such a gyroscope has three degrees of freedom, that is, it rotates upon one axis and is free to turn about two others, one horizontal and at right angles to the first and the other vertical. Suppose now that we clamp the gyroscope in a horizontal plane allowing it to turn only about the vertical axis and then set it spinning. If by means of electricity we keep up the spin the axis of the gyroscope will point constantly in the same direction but. because of the rotation of the earth beneath it, this axis will seem to turn successively to every point of the compass and describe a complete circle every twenty-four hours. Thus does the gyroscope prove the earth's rotation.

Now suppose we make a larger and heavier gyroscope mounted with three degrees of freedom and operated by electricity. Let us as before clamp the gyroscope in a horizontal plane but give it freedom about the vertical axis and then set it spinning. Now since the gyroscope is under the influence of two motions, its own rotation and the rotation of the earth, it is bound to precess just as our bicycle wheel did and will slowly swing around until it has placed its axis in line with the meridian, or in other words pointing true north and south. It has done as far as possible what the gyroscope is perpetually trying to do — place its axis parallel with that of the larger curve in which it is moving. Now let us unclamp the horizontal ring giving the gyroscope freedom to move in a vertical plane and slowly its axis will rise until it is parallel with the axis of the earth and points to the pole star. And there it will remain pointing, not to the magnetic north but to the true north, with an accuracy that knows no ''variableness nor shadow of turning."

In a fixed position on land the operation of such a compass presents no difficulties, but when it comes to mounting one on a ship which may move in any direction and at the

Fig. 2. — A gyroscope mounted with three degrees of freedom.

same time be tossed by the waves, the gyroscope receives a ''mixed" motion which deflects it from the meridian. But Mr. Sperry has overcome these seemingly insuperable difficulties and with the insight of true genius has perfected automatic correcting apparatus which neutralizes the effect of every variable influence. Like a creature of Hfe this gyro-compass seems instinct with initiative and self control. Quicker than human thought it adapts itself to every change of motion and with unerring accuracy guides the mariner both on the surface of the sea and through its depths.

What the magnetic compass has meant to navigation cannot well be overestimated. With the advent of the steel ship, however, its use has become constantly more difficult. In the days of wooden ships practically the only influence that reached the dehcately balanced compass needle was that of the earth's magnetic field. But the large masses of iron in a modern ship with their attractions for a suspended magnet have introduced disturbing factors which cannot easily be neutrahzed and which have destroyed much of the former usefulness of this instrument. The magnetic field of the earth is at best exceedingly weak and the directive force which it exerts is not sufficient to hold the needle steadily on the meridian. Then, too, the compass needle, except for a few places on the earth's surface, does not point to the true north but to the magnetic north and tables of declination giving the amount of this variation must always be consulted by the mariner in determining the real course of his ship.

Therefore, the invention of the gyro-compass which is entirely independent of all magnetic influences marks the greatest advance in practical navigation in recent years. Utilizing the immense directive force of the earth's rotation, an instrument of the highest precision has been produced

The ship stabilizer, the g>To-compass and a simple demonstration of gyroscopic

action.

and one which points to the true north whatever may be the ship's position and course or however violently it may be tossed by the waves.

The first experimenter to utilize the principle of the gyroscope in a practical instrument was the great French physicist, Leon Foucault, about the middle of the last century. He mounted a gyroscope with three degrees of freedom and, as already described, was able to give visible proof of the earth's rotation. He carried his apparatus to England and exhibited it before the Royal Academy where he aroused the greatest enthusiasm. In 1878 the wellknown American author and physical demonstrator, Hopkins, appKed an electric motor to Foucault's gyroscope and was able to obtain much more certain results. The gyro-compass which he set up operated very well in a stationary position but when subjected to the varying motions of a wave-tossed ship it became practically useless.

As previously stated the man who has contributed most to the perfection of a gyro-compass of absolute reHability, one which automatically adjusts itself to every movement of the ship and points with unvarying accuracy to the true north is the American inventor, Mr. Elmer A. Sperry. A marvelous instrument is this eye of the ship. As one observes it in operation in Mr. Sperry' s factory, subjected to artificial motions, more severe than any encountered in actual service, the unchangeableness with which it holds to the meridian gives the appearance of a living, throbbing organism endowed with intelligence and self control. But here again, just as in every other useful device, this mechanism is the product of himian thought. Back of it stands the idea of the inventor translated into material expression. It is additional proof of the psychological truth that personality is the keynote of the imiverse.

lo The Boys' Own Book of Great Inventions

Without the gyro-compass the navigation of the submarine would have been exceedingly difficult and its sphere of action greatly restricted. A magnetic compass is of Httle use on underseas craft owing to their steel structure and the weak magnetic field of the earth. The equipment for a battleship or submarine consists of a master compass and a number of repeaters conveniently placed about the ship and all under electrical operation and control. The heavy wheel of the master compass revolves in a vacuum case with a speed of approximately 8600 revolutions per minute. Its construction including the automatic correcting devices for changing motions is somewhat intricate but its operation is strictly in accord with the gyroscopic action already explained.

The Monorail Car. — To the imagination and genius of Mr. Louis Brennan, a young man of Irish birth, whose youth was passed in Australia, a country of great distances and at that time inadequate railway faciUties, we owe the spectacle of a car that travels on a single rail, imsupported on either side yet balancing itself perfectly, sensitive to the slightest strain but secure and stable as a mountain side. A paradox it, indeed, seems to be, yet, as we shall see, strictly in accord with the laws of gyroscopic action. The same force that holds the earth's axis pointing invariably to the pole star or balances a swiftly rolling hoop operates here to give a wonderful exhibition of inherent strength and stability. To conceive of such a project, so revolutionary to all current ideas of locomotion and apparently in direct opposition to natural laws, and then to work it out to ultimate success is the mark of true genius.

As Mr. Brennan grew to young manhood surrounded by the vast spaces of AustraHa, he pictured in imagination the future of this great continent thickly peopled, dotted

The Gyro Paradox ii

with large cities and highly organized industrially and agriculturally. But there seemed to be one insuperable obstacle to this rapid development, namely, the great cost of railroad construction and certain very serious defects in the two-rail system. It is a very difficult matter to lay two rails exactly parallel and keep them so or to build a road bed so solid and secure that the rails will at all points be at the proper height. Any considerable deviation from the parallel condition results in severe side thrusts or even derailment and the depressions in the rails cause jolts and rocking, so violent as to make very high speeds dangerous and impossible. These defects were more common to the railways of Australia, imdoubtedly, than they are to those of this country. As Brennan suffered the discomforts incident to travel there, he became convinced that the future of that vast area depended upon improved transportation facilities and he determined to solve this problem. Thus does the vision of the seer blaze the way of progress.

To overcome these defects there seemed but one way and that by means of a one rail system. Therefore, Brennan without any hesitation set himself to invent such a system. But how to make a car balance itself on a single rail was a baffiing problem. Brennan had the idea. The means for its material creation were yet to be discovered and perfected. For years the problem was constantly with him. He could not get away from it. Having become familiar with the action of the gyroscope and its wonderful stabilizing power, he bought several models and began to experiment. At last he was on the right track. And then came a long period of experimentation in the laboratory, the workshop in which man hammers into material expression the ideas which his genius creates. He made tops and mounted gyroscopes in a great variety of ways. He found that a picture frame mounted on two sharp pins could be balanced perfectly by placing within the frame a spinning gyroscope. When he replaced the pins with wheels, tandem fashion, not only would the frame balance itself but it would run on a stretched wire. So long as the spin was kept up the mechanism exhibited great stability. If one pushed against it the frame pushed back with an equal and opposite thrust. The problem seemed nearing solution, but Brennan soon found that his car would turn over on its side and leave the track at the first curve. Obviously it is impossible to build railroads mthout curves and therefore a new and very difficult problem had presented itself. As will be seen a httle later, the cause of this mishap is a direct result of the laws of motion governing the gyroscope and its remedy seems very simple now. To Brennan it proved an obstacle which he was long in overcoming. The very law of motion which he was seeking to utilize as the stabilizing force of his car seemed likely to defeat his purpose and bring his years of thought and work to naught.. But perseverance knows no turning back and Brennan had no idea of abandoning his purpose. He went to southern France for a short rest but the problem of the curve perpetually haimted him. One morning he bought a toy gyroscope of a street vender, a very crude affair when compared with the elaborate ones in his own laboratory, but as he spim it and pondered its action in a flash there came to him the way out of his difficulty. He returned to England and very shortly perfected the first model of the Brennan car.

On May 8, 1907, Brennan exhibited his model before the Royal Society and later gave numerous public demonstrations at his country place. Here was a car that balanced itself automatically, pushed back with a very great force against any thrtist tending to drive it from the track, rounded sharp curves, climbed steep grades, followed the crookedest gas pipe with perfect ease and crossed deep ravines on a slender and swaying cable. If a heavy weight were placed on one side, the car did not fall but rose sHghtly to meet the load. If one thrust down on the edge of the car, it pushed back and rose. In roimding a curve the car leaned in sKghtly just as a bicycle rider does. Indeed, it seemed instinct with intelligence and Hfe. And all on a single rail, as stable when at rest as when in motion.

A closer inspection revealed a two chambered compartment in the front of the car in which two small fly wheels rotated in vacuum cases at the rate of about 7000 revolutions per minute. These wheels, smaU but heavy, rotate in opposite directions and being mounted so as to permit of precessional movement constitute the balancing mechanism of the car.

Just how they operate will become clear from a consideration of the following figures and explanation. Brennan has simply utilized the very great inertia of a rotating body, which is free to precess, in balancing his car. But far from being in defiance of gravitation this balancing power is the direct result of well known laws of motion.

Figure 3 shows a gyroscope mounted with three degrees of freedom, that is, it may rotate about axis OA and at the same time turn on axis BC or DE. If the heavily rimmed wheel is set spinning, its inertia will keep its axis OA pointing in the same direction and will resist any effort to displace it. This resistance, however, will manifest itself by causing the gyroscope to turn or precess about one of the other axes. Suppose we attempt to force the axis of the spiiming gyroscope down by applying pressure at A. The result is not a downward but a horizontal movement of the whole mechanism to the left about axis DE. If now we apply a vertical upward pressure at A, the precession will take place in the opposite direction. Should we endeavor to hasten the precessional movement by exerting

Fig. 3.

a sidewise thrust at A, the axis of the spinning wheel will either rise or fall. It will rise if we push to the left and fall if we push to the right. In any of these cases we are subjecting the gyroscope to two rotations at the same time and, just as in the case of the bicycle wheel, it attempts to rotate on the resultant axis lying between the two. And it makes no difference whether the gyroscope be subjected to one or several disturbing influences, each will have its own effect. So long as the spin keeps up the action is automatic and instantaneous, the mechanism responding immediately to every influence, however slight. Its action is literally quicker than human thought. The amount of its inertia and therefore its stabilizing influence depends simply

Fig. 4. — Gyroscope to illustrate the balancing action in the mono-rail car.

upon the mass of the gyroscope and the speed with which it rotates.

Now let us consider Fig. 4. This will explain the action of the gyroscope in balancing the mono-rail car. By means of the vertical axis DE the gyroscope is attached to the frame work of the car. The axle OF carries two friction wheels, or rollers Wi and W2 which during the operation of the gyroscope will according to various influences come in contact with segments Si S2 S3 S4. These segments are a part of the framework of the car. The roller Wi is loosely mounted on the axle OF so that it is free to turn whenever pressed against the adjacent segments of the car frame. On the contrary roller W2 is not attached to the axle but to an extension of the horizontal portion of the gyroscope frame.

Now let us see what will happen when a car running on a single rail and supplied with such a gyroscope is subjected to any of the variable influences such as the centrifugal force from rounding a curve, wind pressure, or the sudden shifting of passengers and freight. Suppose the car suddenly tips to the right from the weight of fifty passengers who move to that side of the car. This will bring segment 5*1 down against roller Wi and because of the friction between them the roller will immediately begin to run along the segment just as a locomotive wheel runs along the rail. But it will be seen that this is the same as a side thrust on the axle OF, pushing it to the left and, just as explained in Fig. 3, the result will be an upward movement of the axle. In other words as the car tends to tip to the right the automatic action of the gyroscope gives an upward thrust in the opposite direction, which causes the car to tip back to the left. This action will bring segment S2 in contact with roller W2 giving an upward thrust to the axle OF, but an upward thrust, it will be remembered, causes the axle to move to the right, thus bringing roller Wi in contact with S3 along which it tends to roll. This will increase the movement to the right and therefore cause the axle to be depressed downward, for a side wise thrust to the right brings a downward movement of the gyroscope axle. This downward movement will bring segment S4 in contact with roller W2 which will arrest the downward tendency and move the axle back to the left and into its original position. All this happens instinctively, as it were, and with lightning rapidity. Whatever the disturbing influence may be, this series of oscillations is set up and continues until the whole car is again in perfect balance.