[LM302013], Letter from Edison Manufacturing Co, Alfred Ord Tate to Philadelphia and Reading Railroad Co, Elkanah Ralph Adams, December 13th, 1889


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[LM302013], Letter from Edison Manufacturing Co, Alfred Ord Tate to Philadelphia and Reading Railroad Co, Elkanah Ralph Adams, December 13th, 1889

Editor's Notes

Replying to your letter of 7th instant, I enclose herewith diagram ofproposed arrangement on your wires, together with a statement in detail of cost of maintenance.##We would propose running these eight wires from one battery of 232cells, which I have arranged in the most economical manner, by grouping the lines and dividing them up, with regard to the points in the battery where they would take current. Lines No. 1, 2, & 3 being of high resistance, require to be operated by the full number of cells; Nos. 3, 4 & 5 are operated by 157 cells (Div. A, plus Div. B) and Nos. 6 & 7 are operated by 116 cells (Div. A). Or to reverse this explanation, Division A works on the full number, 8 lines, and, of course, has the shortest life; Division B works on 6 lines, and its life is longer than the former; and Division C works on 3 lines and has the longest life. [When?] artificial resistances are indicated for each line, and the number of ohms required is given in each case. For instance, line #2 has 1612 ohms artificial resistance, and 4188 ohms in the line itself & c.##The statement of cost of maintenance, shows that the total number of lines can be supplied with current fro an outlay of $722.30 per year. The cost per year for each line is $90.30, and the cost per month for each line $7.55##In regard to statement of cost and labor, it is based upon the assumption that onje man can renew 15 of these cells in an hour, or 150 cells in a day of ten hours, and it is further assumed that the rate usually paid for this class of labor is 20 cents per hour. Therefore, to make one renewal of Division A, 116 cells, would take about seven hours; Division B, 41 cells, three hours; and Division C, 75 cells, five hours. Those multiplied by the number of renewals per year, give us a total for the three Divisions of 75 hours of labor, which at 20 cents per hour, would be $14.60 per year for 8 lines, which is $1.82 for each line, or 15 cents per month for each line. I make this estimate of labor, not so much for the sake of the cost which it represents, but to illustrate how insignificant a part it plays int eh maintenance of your cells. It shows further that one man could mak allt he renewals upon the whole of your railway system if our cells were employed.##We could furnish you this battery complete at a cost of $1.75 per cell, making your total investment $406.##In regard to the advantages to be dreived from the use of these cells: as the internal resistance of each is only .025, the internal resistance of the full battery of 232 cells, is but 8/10th ohms. This will supply a regular dynamo current, and your lines will operate just as well in wet weather as in dry weather. Our zincs never require to be cleaned, and when the copper plates are exhausted, we will buy them back from you at nine cents a pound. The copper plates in this battery have a capacity of 600 ampere hours, so that the first renewal made after the battery has delivered 300 ampere hours, is of the zincs alone. The next renewal is of zinc and copper, and the next zinc alone, and son on. The total yield of coper which we would buy back from you would be in the neighborhood of 550 pounds per year, representing a vlaue of450, by which amount the estimate attached hereto should be reduced. Thiswould make the cost per year for each line $84, and the cost per month for each line $7.00##In regard to line No. 3, which you state in your letter is only five miles in length, with a resistance of 2300 ohms, you must have about 15 coils on this line of wire. I have placed it, therefore, in Division B, and thrown in 1650 ohms artificial resistance, so that when the relays are cut out at night, as probably most ot them are, there will not be too much waste of current. I shall be glad to hear from you further when you have given this matter due consideration. Yours very truly Edison Manufacturing Company by A O Tate




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Thomas A. Edison Papers, School of Arts and Sciences, Rutgers University
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