Iron wire

“ Iron seems to be the most desirable material for guard wires because it gives the required mechanical strength and sufficient conductivity at a less cost than copper, aluminum, or bronze, and is easier to handle and less liable to break than steel. It was formerly the practice to staple guard wires to the tops of poles or to the ends of cross-arms, but it was found that the wire was more apt to rust and break at the staple than elsewhere, and in the better class of work such wires are now mounted on small insulators. ”

“ Things that seem to us most solid are equally mobile. An iron wire seems solid. It is so; some parts much more so than others. The surface that has been in closest contact with the die as the wire was drawn through, reducing its size by one half, perhaps, is vastly more dense than the inner parts that have not been so condensed. File away one tenth of a wire, taking it all from the surface, and you weaken the tensile strength of the wire one half. But, dense and solid as this iron is, its particles are as mobile within certain limits as the particles of air. ”

“ Therefore the advantages in point of price of iron wire over copper in the first place, would be greatly overbalanced by the increased cost of insulating and sheathing it. It is of the greatest importance that the copper wire of the cable should be as pure as possible, for the slightest trace of arsenic or other foreign element is sufficient to hamper, in some mysterious way, the swift course of the subtle current, and very materially to weaken the conducting power of the wire. ”

“ As might be expected, conductors traversed by such currents are rapidly heated, owing to the increase of the resistance, and the heating effects are relatively much greater in the iron. The hysteresis losses in iron are so great that an iron core, even if finely subdivided, is heated in an incredibly short time. To give an idea of this, an ordinary iron wire 1/16 inch in diameter inserted within a coil having 250 turns, with a current estimated to be five amperes passing through the coil, becomes within two seconds' time so hot as to scorch wood. ”

“ FIG. 24.—Showing how wires are arranged and insulated.
Aluminum wire is very light, and causes very little strain on the pole or cross-arms. It offers more resistance than copper, but some of the larger sizes may be used with equally good results.
Iron wire must never be used, even if galvanized or tinned. It possesses a certain reactance tending to choke off the high frequency currents.
FIG. 25.—Aerial insulator. ”

“ My experiment is well illustrated by the writer's diagram, except that the nail should be at the end of the iron wire, where its polarity is of course most strongly marked. But the result is not as he states it. For, as the wire is brought up toward the magnet, the nail drops off before the wire touches the magnet. When the sheet iron is used, the point at which the nail drops off is farther from the magnet than in the case of the wire, and when it is brought nearer it will again pick up the nail, which then continues to cling until the iron touches the magnet and afterwards. ”

“ But I mention this as an illustration of the fact that fine wire cannot be produced at one drawing, but must, so to speak, be coaxed down to the requisite degree of attenuation, even when so valuable a metal as gold is used. As a general rule, it may be taken that iron wire requires more coaxing than brass, brass more than copper, and copper more than the precious metals—their different degrees of malleability rendering them amenable to different degrees of treatment. ”

“ In cities and wherever the iron circuits were subjected to the destructive effects of atmospheric action, especially where much bituminous coal was used, oxidization shortened the life of the circuits in the pioneer telephone days, just as now happens thirty years later. The prevailing belief among the early telephone men was that iron wire would have an average life of from fifteen to twenty years. ”

“ Best best (B. B.) , which varies more in quality, is not so tough, and is lower in conductivity. It is frequently sold as E. B. B.;
3. Best (B.) , which is the poorest grade made, being more brittle, and lowest in conductivity. Iron wire should be well galvanized.
German Silver Wire.—German silver is an alloy consisting of 18 to 30% nickel, and the balance about four parts copper to one part zinc. It is very largely used as a resistance material in making resistance coils, and is sold in the form of wire, and strip. The resistance of this wire varies with its composition. ”

“ For an iron wire Y/p is about io 12 /4, so that for a frequency of 500 in a wire fixed at both ends a length about 5 metres is required. If the wire is stretched across a room and stroked in the middle with a damp cloth the fundamental is easily obtained, and the first harmonic can be brought out by stroking it at a quarter the length from one end. A glass or brass rod free at both ends may be held by the hand in the middle and excited by stroking one end outwards with a damp cloth. ”

“ These inventions were the foundation of the system of patents under which barbed wire has been protected and sold. The development of the barbed wire industry would hardly have been possible without steel. Iron wire, used for fencing prior to the introduction of steel, was not suitable, seeing that iron does not possess sufficient tensile strength and lacks homogeneity, qualities which Bessemer and open-hearth steels possess in a high degree. ”

“ Since writing the above, I find that when, in the apparatus of twenty copper and twenty zinc plates, ten copper plates on one side are connected with ten zinc on the other, and a communication made between the remaining twenty by a piece of iron wire, about the eighth of an inch in diameter, the wire enters into a vivid state of combustion on the immersion of the plates. Platina wire equal to No. 18 (the largest I had at hand) is rapidly fused if substituted for the iron. ”

“ Formerly iron was used for telegraph wires; but it needs much more electricity to carry power or light or heat or a telegraphic message over an iron wire than one of copper. Moreover, iron will rust and will not stretch in storms like copper, and so needs renewing much oftener. Electric lighting and the telephone are everywhere, even on the summits of mountains and in mines a mile below the earth's surface. ”

“ A continuous rod of good conducting metal must be carried from the top of the building to the ground. Describes varying carrying capacities of iron, zinc, or copper; recommends from his experience in South Africa, 42–strand rope of 1/16th inch galvanised iron wire.
The disintegrating energy is mainly expended on the extremities of the conductor.
In Natal he used to enclose the top of the rope in a tube of stout zinc, finished at the top by a gilded ball of wood, and he opened the strands of the wire above it into a brush. The French electricians strongly recommend a cluster of points. ”

“ An electrical explosion which only melts a copper wire would utterly destroy an iron wire of twice the diameter of the former. In being heated a rod contracts in length, and is then liable to fracture by the shrinkage, but if of sufficient size these results are not likely to occur. An iron rod, by successively receiving an electrical discharge, is sometimes reduced in size.
The conducting power of metals likely to be found in buildings is as follows: taking the power of lead as one, that of tin will be two—that is, tin conducts electricity twice as well as lead ”

“ In fact, it has been ascertained that iron always becomes a magnet when electricity is passed round it. The alarm-bells of the electric telegraphs are set ringing by a simple application of this principle. A conducting wire is made to run for hundreds of miles, and then coils itself round an iron bar. ”

“ The wire may be wound on by hand, but a winder (App. 93) will do much better and quicker work.
APPARATUS 84.
113. Horseshoe Electro-Magnet. Fig. 58. Bend soft iron wires, and make a bundle of them. If you wish to wind the wire around spools, the bundle cannot be very large. It will be found best to make the bundle about 3⁄8 in. in diameter, and not to use the spools. Strong paper should be wrapped once or twice around the legs of the horseshoe, and the insulated wire, say 4 layers, can then be wound directly upon this. ”

“ A mass of soft iron (shape immaterial) is wound with many turns of insulated copper wire, in such a manner that, were an electrical current sent along the wire, the mass of iron would become strongly north at one extremity, and south at the other. As prolongations of the electro-magnet thus produced are affixed two masses of iron facing one another, and so fashioned or bored out as to allow a ring, or cylinder of soft iron, to rotate between them. ”

“ Insulated wire for the purpose of winding magnet coils is termed magnet wire. Copper is the material almost universally employed for the conductor. Its high conductivity, great ductility, and low cost are the factors which make it superior to all other metals. However, in special cases, where exceedingly high conductivity is required with a limited winding space, silver wire is sometimes employed, and on the other hand, where very high resistance is desired within a limited winding space, either iron or German silver or some other high-resistance alloy is used. ”

“ Hold the bundle of wires in a vise, and file the ends smooth, before winding on the wire. Paraffine should be used to hold the turns of insulated wire together.
APPARATUS 83.
112. Electro-Magnet. Fig. 57. An electro-magnet with a removable core may be made by winding the wire [Pg 53] on a spool. The core is made, as in App. 82, of soft iron wires, bound together with stout thread. A bolt may be used instead of the wire, but the wire loses its magnetism much quicker than a soft steel bolt would. ”

“ Electricians are said to be somewhat divided in opinion as to the relative advantages of iron and copper wires for transmitting the electric current, but for over-head wires the London and North Western Company prefer galvanised iron wires, as having greater tensile strength and superior powers of elongation and contraction, so as to allow for a considerable variation in temperature. ”

“ When wire is wound by hand from a spool into a coil, or around a core, it soon becomes twisted and tangled. Make a winder. This will keep the wire straight and save much time.
APPARATUS 81.
Fig. 54.
108. Electro-Magnet. Fig. 54. Drive a nail into a board so that it will project about 3⁄4 of an inch. A soft, or wrought-iron, nail is best, but a short, thick wire-nail will do. If you do not have a thick nail, use an iron screw. Wind 3 or 4 layers of insulated copper wire around it, and fasten the bare ends of the wire down with bent pins. ”

“ It is absolutely essential that the iron be very soft and well annealed, otherwise the iron cores retain a considerable amount of magnetism when the current is not passing, which makes the bell sluggish in action, and necessitates a higher battery power to make it work (see § 14) . Two bobbins of insulated wire are fitted on the cores, and the magnet is held in its place by a transverse strip of brass or iron secured by a wood screw passing between the two bobbins. ”

“ He advocates the use of iron as the best metal to use, specifying a weight of 2 lbs. per foot. He thinks wire ropes are more easily applied than rods, ribbons, or tubes, and prefers a rope 1·2 in. diam. of six strands of seven No. 11 B.W.G. wire, each round a hemp core—costing about 5d. per foot. Conductors should be specified in terms of electrical units, viz.: ·3 ohms per 1000 yards, and be continuous. Every unavoidable joint should be soldered. He has found in practice many bad joints, especially in copper conductors. ”

“ If the wire has been wound on the bare cores (without bobbins) , as is sometimes done, bared places in the wire may be touching the iron. This may be ascertained by connecting one pole of a bottle bichromate, or other powerful battery, with one of the wires of the electro-magnet coils, and drawing the other pole of the battery across the clean iron faces of the electro-magnet poles. If there is any leakage, sparks will appear on making and breaking contact. Nothing but unwinding and rewinding with a well covered wire can remedy these defects. ”

“ But, what is still more remarkable, these induced currents may be sent through the wire without the actual contact of the soft iron with the steel bar. If this piece of iron is brought very near to one magnet without touching it, and then withdrawn, an electric thrill or wave is induced in the wire which is felt in the distant magnet, just as if the contact had been actually made and broken. And so if we play the piece of soft iron backward and forward, before the magnet, no matter how rapidly or slightly, each motion is felt as an electric pulse in the magnet at the other end. ”

“ Conductors of small iron rod or wire are very objectionable. They commonly rust at the joints, and have fallen to pieces, and often been knocked to pieces by lightning. Iron may, certainly, be employed with advantage, but should be galvanized. Zinc is an even better conductor than iron; and being spread over the surface is not open to the objection of making a conductor of two metals of unequal conducting power. A good and efficient conductor might be formed of galvanized iron. It should be of wrought iron, galvanized, of 2 inches diameter, with screwed joints of extra thickness. ”