[D8737AAW], Test Report, Henry E Walter, May 11th, 1887


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[D8737AAW], Test Report, Henry E Walter, May 11th, 1887

Editor's Notes

"I find that in making these tests it is necessary to make several corrections in order to get at the comparative heat generated in any armature, and in order to do this the armature had to be run each time to get at the exact rate of cooling under the test ## By running the armature core after the test for a given time, and taking the fall of temperature in exactly that time, the rate of cooling under different temperatures is arrived at, and know this the exact temperature of the armature for the test can be calculated; that is the temperature the mass of iron would rise to if all the heat had been held in; this divided by the time it ran would give the absolute rate of generation of heat per minute (from which can be calculate the h.p. absorbed by the machine.) ## After these corrections had been made on the previous core tests, at least on all the armatures that had been run for the cooling value, it turns out that where these tests gave apparetnly the same result, they now give a variation of 25% in heat. In the case of the '12' bronze sleeve, it seems that the cooling value was very high, perhaps because a good deal more heat was conducted through the shaft (to bearings or radiated from the bare shaft) than in the case of the armature with regular wooden sleeve; or it may be because it was not well covered. Again, the armature with bronze sleeve and plates only cooled off at same rate as armature with wooden sleeve, seeming to show that the bronze sleeve was not well covered. In any case the results show that the bronze sleeve increases the heat by 25% and the bronze plates decrease the heat by the same amount, therefore a '12' armature constructed of bronze sleeves and plates would heat about the same extent as one with wooden sleeves and iron plates. In the case of most other machines the heat would be less in the former case as the '12' is rather short of section in the armature core. In the case of the '16's' all the figures go to show that the heat of the this plate armature is from 55 to 60% of that of the regular one and since there ought to be only 25% of the heat instead of 55% there must be some constant source of heat not remedied by the this discs, which must be the iron plate and the shaft. Figures on heat in latter, to come later."



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