Publication: The Telegrapher
New York, NY, United States
On Economical Line Construction.
By DAVID BROOKS.
THE number of posts per mile usually employed in this country is double the number used in Europe. The greatest number per mile in England is twenty for ten or more wires. On the Continent it is rarely over sixteen, yet their lines are very substantially built.
If a number eight wire is stretched one span at a time, and pulled up the full strength of two men, and the posts are thirty to the mile or more, such line will be so tight as to contract and break in cold weather provided the line is strung in warm weather. On curves and angles the contraction forces the poles out of line; but if the posts are but twenty or less per mile, two men cannot pull up the span so nearly straight as not to leave a curve or sag in the wire that will admit of a much greater strain from contraction by cold without breaking the wire. The breaking strain of a number eight wire is from twelve hundred to eighteen pounds, according to quality. To bring up the span to within twenty inches of being straight requires a tension equal to four hundred and twenty pounds, where the poles are twenty to the mile. The same force will bring up the span, where sixteen poles to the wile are employed, to within twenty-four inches of the straight line.
Such a strain will split or detach any ordinary wood bracket or pin when the wire is strung one span at a time, and tied or fastened to the common glass insulator. The support of the Prussian insulator is a wrought iron bracket weighing three and a half pounds, sufficient strength to sustain a tension of one thousand pounds without bending or breaking. This system of a reduced number of poles is not practicable with the common glass insulators. They are of too frail a nature. As used with thirty to forty poles to the mile, a large percentage are broken in suspending the wires, not infrequently as many as thirty per cent. Thus go to waste.
It has been objected to this system of reduced number of poles that the wires are more liable to be broken by sleet, but that does not follow. A number eight or nine wire of good quality will sustain the necessary tension, say three hundred and fifty to four hundred and fifty pounds, and an additional strain of one thousand pounds without breaking, and that is far greater than any sleet will produce; but if fifty poles to the mile are used with wires pulled tight, sleet will break every span. With sixty poles to the mile, to avoid this very difficulty over the Alleghenies, I have seen the wires entirely prostrated by sleet, owing to the wires being stretched too tight.
It has been urged, also, that the wires are more liable to be crossed and twisted by high winds, but with a secure fastening for the wire at the insulators that does not follow. The weight of the wires keep them at their proper distance apart, and when moved by the wind, "swing and keep time together."
In 1867 I spent two weeks traveling with one of the Inspecteurs through France, where they were rebuilding their lines and reducing the number of poles. All these objections and others I suggested, but his reply was that he would use no more poles, even if they were furnished without cost. The portion of the French lines along the British Channel are exposed to very violent winds. The wires run over the bluffs, which rise hundreds of feet perpendicularly from the sea, and these shores are subject to very violent gales; in winter they are also subject to sleet, yet I venture to say there are no lines in this country that will begin to stand the exposure that theirs do.
About twelve years since there was inaugurated in Europe the use of large size wires for the long circuits - wires of four and five millimetres in diameter, equal to our number four and three gauges, but no material improvement was effected until the lines were reinsulated with what is known as the Prussian Insulator. About the year 1863 and '64-say ten years since-this insulator was adopted in Russia, Sweden, Denmark, Italy, and in France in 1867. The effect was to enable them to work from four to five times as far in bad weather as with the earlier kinds, which were generally glass, as good or better than the modern glass of this . . . [illegible text] . . . or in other words, they could work a number eleven or twelve wire a much greeter distance than formerly a number three or four. The economy of this change of insulation in the construction of lines is at once manifest. Now the wires erected are no larger than number eight for the long circuits, besides the length of the circuits worked are longer than formerly. The longest line without repeaters, or in single circuit, is from St. Petersburg to the East Indies, over three thousand miles, and this with a number eight wire. The Prussian insulator has about four times the insulating properties of the common glass of this country; with half the number per mile they are enabled to work eight times as far in rain, which will carry them out of and beyond the storm, which seldom ever extends five hundred miles in a direct line at the same time. Now the size most employed in the erection of new lines corresponds to our numbers eleven and twelve.
Were I to build a new line of two hundred miles, I should use no larger size than number eleven galvanized steel or homogeneous iron. It costs about a cent more per pound than ordinary galvanized wire. The difference in cost of wire at present prices would be about $15 per mile-say twenty posts per mile-and you have an additional saving of labor and material equal to $35 per mile, or a total saving in cost of construction of $50 per mile over a line built with number eight wire, and the usual number or poles per mile with glass insulators.
I will agree to work a number eleven wire on Brooks insulators farther, or to greater capacity in rain, than a number six wire can be worked on the common glass, insulators, and not ask one penny of compensation until the service is clearly and fairly performed. Two number eleven wires with Brooks insulators can be erected at about the same expense as one number six wire with the common glass.
The object of this is to show that large and heavy conducting wires involve an expense that brings no adequate return. We must have conductivity, but a wire of number eleven gauge can be worked two hundred miles to the full capacity of the Morse system, and no more can be done if the wire were an inch in diameter. The larger wire requires less battery, but, the saving of that expense has no proportion to increased expense of the heavy wire. There are other inconveniences, such as expense of transportation, difficulty in splicing, strain upon poles, etc., attending the use of heavy conductors, too obvious to need further reference.
We will suppose an instance of one hundred miles of line working twenty-five relays in the circuit, the relays having a resistance of one hundred and fifty units each. The total resistance of the relays would be 3,750, to which add the resistance of a number eight wire, 1,500 units-total resistance of circuit 5,250. In place of a number eight wire substitute a number eleven, having a resistance of 3,000 units. Resistance of circuit in latter ease, 6,750; increase, 1,500 units-about 22 per cent. To compensate for this loss in strength of current it would be necessary to add 22 per cent. of battery, or a fraction over one fifth the number of' cells. The increase or battery will compensate a reduction in cost of wire amounting in round numbers to about $1,500.
Three years since one of our railroad companies re-insulated with Brooks insulators a wire two hundred and fifty miles in length. This wire was a plain number ten, and had been in use twenty years. With the common glass insulators it had become little better than useless in rain. Since reinsulated it has been worked in rain without the slightest inconvenience or difficulty. Portions of this wire, measured by myself three years since, showed a resistance of over sixty units per mile. I recommended rejointing and soldering of the splices. It has been worked since in all weathers, without that expense, up to the full capacity of any wire in dry weather. To have renewed the wire with number eight galvanized would have involved an additional expense of at least $10,000. The report is that this old wire works better to-day than a new number six galvanized wire, upon glass insulators, running upon the same route. With splices rejointed there is no reason why this old plain number ten wire should not do good service for years to come. How many hundred miles of wire have been thrown away, and thousands of dollars expanded to replace the same with new wire, when the trouble was simply defective insulation. There are, of course, localities where wire soon becomes coated with rust and too brittle to bear splicing. Such portions must be replaced with new. Away from smoke and the gases of combustion, even a plain wire will last a long time.
The Washburn & Moen Manufacturing Company make an excellent article of steel wire, the strength of which is fully fifty per cent. greater than ordinary wire. The cost is about one cent. per pound more.
There is a general impression that steel dues not conduct equal to iron, but as drawn for telegraph purposes it is something higher. Latimer Clark gives their relative conductivities as sixteen for steel and fifteen for iron-a difference in favor of steel of nearly seven per cent. The more recent researches of M. Benoit give steel the preference by a fraction over ten per cent.
About two years since a business firm of this city wished to connect their two factories by telegraph. It required eight miles of line with posts. They requested an estimate, from a person connected with one of the telegraph companies, of the cost of a first class line. He estimated for forty posts to the mile and a number eight wire. I also put in an estimate for a number twelve steel wire and fourteen poles to the mile. The latter estimate was accepted. The line has given every satisfaction. Ten poles per mile would probably have answered equally well. They use no greater number for such purposes in Europe.
An article in one of the leading London scientific journals upon the bad condition of the telegraph service in the British East Indies, states that "there is no place in the world where there is such a lack of scientific knowledge in connection with the telegraph service, except America, as in the British East Indies." Whatever justice there may be in the remark applies to the structure of our lines. In this respect I do not think we are a whit behind the English. They stick to their old fogy notions with a pertinacity that is perfectly inexplicable. The application of science to the arts or industries is to but one purpose, viz., to get the greatest return for a given amount expended. In England their lines cost more and produce less than the poorest lines in this country, from the simple reason that their insulation is inferior to our common glass insulators. They fall no lower in hard rain, but they are very low in moderately damp weather-a kind of weather of which they have an abundance in England. Ten minutes of moderate rain brings their insulators down as far as they will get-a point to which glass insulators will not reach except when the rain is heavy. They are still using large and expensive wires to overcome their defective insulation.
As soon as you cross the Channel a different state of affairs is at once manifest. Early in the history of the telegraph the French Government organized the department of "Inspecteurs," and none could enter this branch of the service without passing an examination in such of the arts and sciences as were considered necessary to qualify them for this particular vocation. Those entering this department were advanced laud promoted according to the progress made in their profession. As a consequence, the works upon the telegraph written by the Inspecteurs are the best ever published, and splendid contributions to science.
The very opposite course has been pursued by the telegraph companies in this country. When an employe manifests a desire to acquire a knowledge of the business as a science, or beyond that of a mere operator, he is hustled out of the way, from fear that his better knowledge may interfere with their own crude and ignorant notions. The cost of transmission of a despatch from one extremity to the other of France is a franc. To send one an equal distance in this country costs, instead of twenty cents, nearer two dollars, and the chances of its being incorrectly transmitted or delayed are in equal greater proportion.
|Date completed:||December 16, 2005 by: Elton Gish;|