PRACTICAL MECHANICS FOR BOYS TEXT

inches, multiply by the length, and then by .0034. In making patterns for aluminum castings provision must be made for shrinkage to a greater extent than with any other metal or alloy. The toughness of aluminum can be increased by adding a small per cent. of phosphorus. All alloys of metals having mercury are called _amalgams_. A sheet of zinc suspended in the water of a boiler will produce an electrolytic action and prevent scaling to a considerable extent. Hydrofluoric acid will not affect a pure diamond, but will dissolve all imitations. A strong solution of alum put into glue will make it insoluble in water. A grindstone with one side harder than the other can have its flinty side softened by immersing that part in boiled linseed oil. One barrel contains 3-3/4 cubic feet. One cubic yard contains 7-1/4 barrels. To find the speed of a driven pulley of a given diameter: Multiply the diameter of the driving pulley by its speed or number of revolutions. Divide this by the diameter of the driven pulley. The result will be the number of revolutions of the driven pulley. To find the diameter of a driven pulley that shall make any given number of revolutions in the same time: Multiply the diameter of the driving pulley by its number of revolutions, and divide the product by the number of revolutions of the driven pulley. A piece of the well-known tar soap held against the inside of a belt while running will prevent it from slipping, and will not injure the belt. Boiler scale is composed of the carbonate or the sulphate of lime. To prevent the formation it is necessary to use some substance which will precipitate these elements in the water. The cheapest and most universally used for this purpose are soda ash and caustic soda. Gold bronze is merely a mixture of equal parts of oxide of tin and sulphur. To unite them they are heated for some time in an earthen retort. Rusted utensils may be cleaned of rust by applying either turpentine or kerosene oil, and allowing them to stand over night, when the excess may be wiped off. Clean afterwards with fine emery cloth. Plaster of paris is valuable for many purposes in a machine shop, but the disadvantage in handling it is, that it sets so quickly, and its use is, therefore, very much limited. To prevent quick setting mix a small amount of arrow root powder with the plaster before it is mixed, and this will keep it soft for some time, and also increase its hardness when it sets. For measuring purposes a tablespoon holds 1/2 ounce; a dessertspoon 1/4 ounce; a teaspoon 1/8 ounce; a teacupful of sugar weighs 1/2 pound; two teacupsful of butter weigh 1 pound; 1-1/3 pints of powdered sugar weigh 1 pound; one pint of distilled water weighs 1 pound. Ordinarily, 450 drops of liquid are equal to 1 ounce; this varies with different liquids, some being thicker in consistency than others, but for those of the consistency of water the measure given is fairly accurate. CHAPTER XIV THE SIMPLICITY OF GREAT INVENTIONS, AND OF NATURE'S MANIFESTATIONS If there is anything in the realm of mechanics which excites the wonder and admiration of man, it is the knowledge that the greatest inventions are the simplest, and that the inventor must take advantage of one law in nature which is universal in its application, and that is vibration. There is a key to every secret in nature's great storehouse. It is not a complicated one, containing a multiplicity of wards and peculiar angles and recesses. It is the very simplicity in most of the problems which long served as a bar to discovery in many of the arts. So extremely simple have been some of the keys that many inventions resulted from accidents. INVENTION PRECEDES SCIENCE.--Occasionally inventions were brought about by persistency and energy, and ofttimes by theorizing; but science rarely ever aids invention. The latter usually precedes science. Thus, reasoning could not show how it might be possible for steam to force water into a boiler against its own pressure. But the injector does this. If, prior to 1876, it had been suggested that a sonorous vibration could be converted into an electrical pulsation, and transformed back again to a sonorous vibration, science would have proclaimed it impossible; but the telephone does it. Invention shows how things are done, and science afterwards explains the phenomena and formulates theories and laws which become serviceable to others in the arts. SIMPLICITY IN INVENTIONS.--But let us see how exceedingly simple are some of the great discoveries of man. THE TELEGRAPH.--The telegraph is nothing but a magnet at each end of a wire, with a lever for an armature, which opens and closes the circuit that passes through the magnets and armature, so that an impulse on the lever, or armature, at one end, by making and breaking the circuit, also makes and breaks the circuit at the other end. TELEPHONE.--The telephone has merely a disk close to but not touching the end of a magnet. The sonorous vibration of the voice oscillates the diaphragm, and as the diaphragm is in the magnetic field of the magnet, it varies the pressure, so called, causing the diaphragm at the other end of the wire to vibrate in unison and give out the same sound originally imparted to the other diaphragm. TRANSMITTER.--The transmitter is merely a sensitized instrument. It depends solely on the principle of light contact points in an electric circuit, whereby the vibrations of the voice are augmented. PHONOGRAPH.--The phonograph is not an electrical instrument. It has a diaphragm provided centrally with a blunt pin, or stylus. To make the record, some soft or plastic material, like wax, or tinfoil, is caused to move along so that the point of the stylus makes impressions in it, and the vibrations of the diaphragm cause the point to traverse a groove of greater or smaller indentations. When this groove is again presented to the stylus the diaphragm is vibrated and gives forth the sounds originally imparted to it when the indentations were made. WIRELESS TELEGRAPHY.--Wireless telegraphy depends for its action on what is called induction. Through this property a current is made of a high electro-motive force, which means of a high voltage, and this disturbs the ether with such intensity that the waves are sent out in all directions to immense distances. The great discovery has been to find a mechanism sensitive enough to detect the induction waves. The instrument for this purpose is called a coherer, in which small particles cohere through the action of the electric waves, and are caused to fall apart mechanically, during the electrical impulses. PRINTING TELEGRAPH.--The printing telegraph requires the synchronous turning of two wheels. This means that two wheels at opposite ends of a wire must be made to turn at exactly the same rate of speed. Originally, this was tried by clock work, but without success commercially, for the reason that a pendulum does not beat with the same speed at the equator, as at different latitudes, nor at altitudes; and temperature also affects the rate. The solution was found by making the two wheels move by means of a timing fork, which vibrates with the same speed everywhere, and under all conditions. ELECTRIC MOTOR.--The direct current electric motor depends for its action on the principle that likes repel, and unlikes attract. The commutator so arranges the poles that at the proper points, in the revolution of the armature, the poles are always presented to each other in such a way that as they approach each other, they are opposites, and thus attract, and as they recede from each other they repel. A dynamo is exactly the same, except that the commutator reverses the operation and makes the poles alike as they approach each other, and unlike as they recede. Steel is simply iron, to which has been added a small per cent of carbon. Quinine is efficient in its natural state, but it has been made infinitely more effectual by the breaking up or changing of the molecules with acids. Sulphate of quinine is made by the use of sulphuric acid as a solvent. EXPLOSIONS.--Explosions depend on oxygen. While this element does not burn, a certain amount of it must be present to support combustion. Thus, the most inflammable gas or liquid will not burn or explode unless oxygenized. Explosives are made by using a sufficient amount, in a concentrated form, which is added to the fuel, so that when it is ignited there is a sufficient amount of oxygen present to support combustion, hence the rapid explosion which follows. VIBRATION IN NATURE.--The physical meaning of vibration is best illustrated by the movement of a pendulum. All agitation is vibration. All force manifests itself in this way. The painful brilliancy of the sun is produced by the rapid vibrations of the rays; the twinkle of the distant star, the waves of the ocean when ruffled by the winds; the shimmer of the moon on its crested surface; the brain in thinking; the mouth in talking; the beating of the heart; all, alike, obey the one grand and universal law of vibratory motion. QUALITIES OF SOUND.--Sound is nothing but a succession of vibrations of greater or less magnitude. Pitch is produced by the number of vibrations; intensity by their force; and quality by the character of the article vibrated. Since the great telephone controversy which took place some years ago there has been a wonderful development in the knowledge of acoustics, or sounds. It was shown that the slightest sound would immediately set into vibration every article of furniture in a room, and very sensitive instruments have been devised to register the force and quality. THE PHOTOGRAPHER'S PLATE.--It is known that the chemical action of an object on a photographer's plate is due to vibration; each represents a force of different intensity, hence the varying shades produced. Owing to the different rates of vibrations caused by the different colors, the difficulty has been to photograph them, but this has now been accomplished. Harmony, or "being in tune," as is the common expression, is as necessary in light, as in music. Some chemicals will bring out or "develop," the pictures; others will not. Colors are now photographed because invention and science have found the harmonizing chemicals. QUADRUPLEX TELEGRAPHY.--One of the most remarkable of all the wonders of our age is what is known as duplex and quadruplex telegraphy. Every atom and impulse in electricity is oscillation. The current which transmits a telegram is designated in the science as "vibratory." But how is it possible to transmit two or more messages over one wire at the same time? It is by bringing into play the harmony of sounds. One message is sent in one direction in the key of A; another message in the other direction in B; and so any number may be sent, because the electrical vibrations may be tuned, just like the strings of a violin. ELECTRIC HARMONY.--Every sound produces a corresponding vibration in surrounding objects. While each vibrates, or is capable of transmitting a sound given to it by its vibratory powers, it may not vibrate in harmony. When a certain key of a piano is struck every key has a certain vibration, and if we could separate it from the other sounds, it would reflect the same sound as the string struck, just the same as the walls of a room or the air itself would convey that sound. But as no two strings in the instrument vibrate the same number of times each second, the rapid movement of successive sounds of the keys do not interfere with each other. If, however, there are several pianos in a room, and all are tuned the same pitch, the striking of a key on one instrument will instantly set in vibration the corresponding strings in all the other instruments. This is one reason why a piano tested in a music wareroom has always a more beautiful and richer sound than when in a drawing-room or hall, since each string is vibrated by the other instrument. If a small piece of paper is balanced upon the strings of a violin, every key of the piano may be struck, except the one in tune, without affecting the paper; but the moment the same key is struck the vibration of the harmonizing pitch will unbalance the paper. The musical sound of C produces 528 vibrations per second; D 616, and so on. The octave above has double the number of vibrations of the lower note. It will thus be understood why discord in music is not pleasant to the ear, as the vibrations are not in the proper multiples. ODORS.--So with odors. The sense of smell is merely the force set in motion by the vibration of the elements. An instrument called the _odophone_ demonstrates that a scale or gamut exists in flowers; that sharp smells indicate high tones and heavy smells low tones. Over fifty odors have thus been analyzed. The treble clef, note E, 4th space, is orange; note D, 1st space below, violet; note F, 4th space above clef, ambergris. To make a proper bouquet, therefore the different odors must be harmonized, just the same as the notes of a musical chord are selected. A BOUQUET OF VIBRATIONS.--The odophone shows that santal, geranium, orange flower and camphor, make a bouquet in the key of C. It is easy to conceive that a beautiful bouquet means nothing more than an agreeable vibratory sensation of the olfactory nerves. TASTE.--So with the sense of taste. The tongue is covered with minute cells surrounded by nervous filaments which are set in motion whenever any substance is brought into contact with the surface. Tasting is merely the movement of these filaments, of greater or less rapidity. If an article is tasteless, it means that these filaments do not vibrate. These vibrations are of two kinds. They may move faster or slower, or they may move in a peculiar way. A sharp acute taste means that the vibrations are very rapid; a mild taste, slow vibrations. When a pleasant taste is detected, it is only because the filaments are set into an agreeable motion. The vibrations in the tongue may become so rapid that it will be painful, just as a shriek becomes piercing to the ear, or an intense light dazzling to the eye; all proceed from the same physical force acting on the brain. COLOR.--Color, that seemingly unexplainable force, becomes a simple thing when the principles of vibration are applied, and this has been fully explained by the spectroscope and its operation. When the boy once appreciates that this force, or this motion in nature is just as simple as the great inventions which have grown out of this manifestation, he will understand that a knowledge of these things will enable him to utilize the energy in a proper way. CHAPTER XV WORKSHOP RECIPES AND FORMULAS In a work of this kind, dealing with the various elements, the boy should have at hand recipes or formulas for everything which comes within the province of his experiments. The following are most carefully selected, the objects being to present those which are the more easily compounded. ADHESIVES FOR VARIOUS USES.--Waterproof glue. Use a good quality of glue, and dissolve it in warm water, then add one pound of linseed oil to eight pounds of the glue. Add three ounces of nitric acid. Leather or Card-board Glue. After dissolving good glue in water, to which a little turpentine has been added, mix it with a thick paste of starch, the proportion of starch to glue being about two to every part of glue used. The mixture is used cold. A fine Belt Glue. Dissolve 50 ounces of gelatine in water, and heat after pouring off the excess water. Then stir in five ounces of glycerine, ten ounces of turpentine, and five ounces of linseed oil varnish. If too thick add water to suit. For cementing Iron to Marble. Use 30 parts of Plaster of Paris, 10 parts of iron filings, and one half part of sal ammoniac. These are mixed up with vinegar to make a fluid paste. To cement Glass to Iron. Use 3 ounces of boiled linseed oil and 1 part of copal varnish, and into this put 2 ounces of litharge and 1 ounce of white lead and thoroughly mingle so as to make a smooth paste. Water-proof Cement. Boiled linseed oil, 6 ounces; copal, 6 ounces; litharge, 2 ounces; and white lead, 16 ounces. To be thoroughly incorporated. To unite rubber or leather to hard substances. One ounce of pulverized gum shellac dissolved in 9-1/2 ounces of strong ammonia, will make an elastic cement. Must be kept tightly corked. For uniting iron to iron. Use equal parts of boiled oil, white lead, pipe clay and black oxide of manganese, and form it into a paste. Transparent Cement. Unite 1 ounce of india rubber, 67 ounces of chloroform, and 40 ounces of mastic. This is to be kept together for a week, and stirred at times, when it will be ready for use. To Attach Cloth to Metal. Water 100 parts, sugar 10 parts, starch 20 parts, and zinc chloride 1 part. This must be first stirred and made free of lumps, and then heated until it thickens. United States Government Gum. Dissolve 1 part of gum arabic in water and add 4 parts of sugar and 1 part of starch. This is then boiled for a few minutes, and thinned down as required. TO MAKE DIFFERENT ALLOYS.--Silver-aluminum. Silver one-fourth part, and aluminum three-fourth parts. Bell-metal. Copper, 80 parts; tin, 20 parts. Or, copper, 72 parts; tin, 26 parts; zinc, 2 parts. Or, copper 2; 1 of tin. Brass. Copper, 66 parts; zinc, 32 parts; tin, 1 part; lead, 1 part. Bronzes. Copper, 65 parts; zinc, 30 parts; tin, 5 parts. Or, copper, 85 parts; zinc, 10 parts; tin, 3 parts; lead, 2 parts. German Silver. 52 parts of copper; 26 parts zinc; 22 parts nickel. For Coating Mirrors. Tin, 70 parts; mercury, 30 parts. BOILER COMPOUNDS.--To prevent scaling. Use common washing soda, or Glauber salts. TO DISSOLVE CELLULOID.--Use 50 parts of alcohol and 5 parts of camphor for every 5 parts of celluloid. When the celluloid is put into the solution it will dissolve it. To Soften Celluloid. This may be done by simply heating, so it will bend, and by putting it in steam, it can be worked like dough. CLAY MIXTURE FOR FORGES.--Mix dry 20 parts of fire clay, 20 parts cast-iron turnings, one part of common salt, and 1/2 part sal ammoniac, and then add water while stirring, so as to form a mortar of the proper consistency. The mixture will become very hard when heat is applied. A Modeling Clay. This is made by mixing the clay with glycerine and afterwards adding vaseline. If too much vaseline is added it becomes too soft. FLUIDS FOR CLEANING CLOTHES, FURNITURE, ETC.--For Delicate Fabrics. Make strong decoction of soap bark, and put into alcohol. Non-inflammable Cleaner. Equal parts of acetone, ammonia and diluted alcohol. Taking dried paint from clothing. Shake up 2 parts of ammonia water with 1 part of spirits of turpentine. Cleaning Furniture, etc. Unite 2.4 parts of wax; 9.4 parts of oil of turpentine; 42 parts acetic acid; 42 parts citric acid; 42 parts white soap. This must be well mingled before using. Removing Rust from Iron or Steel. Rub the surface with oil of tartar. Or, apply turpentine or kerosene, and after allowing to stand over night, clean with emery cloth. For Removing Ink Stains from Silver. Use a paste made of chloride of lime and water. To clean Silver-Plated Ware. Make a mixture of cream of tartar, 2 parts; levigated chalk, 2 parts; and alum, 1 part. Grind up the alum and mix thoroughly. Cleaning a Gas Stove. Make a solution of 9 parts of caustic soda and 150 parts of water, and put the separate parts of the stove in the solution for an hour or two. The parts will come out looking like new. Cleaning Aluminum. A few drops of sulphuric acid in water will restore the luster to aluminum ware. Oil Eradicator. Soap spirits, 100 parts; ammonia solution, 25; acetic ether, 15 parts. DISINFECTANTS.--Camphor, 1 ounce; carbolic acid (75 per cent.), 12 ounces; aqua ammonia, 10 drachms; soft salt water, 8 drachms.