[D8737AAS], Test Report, Charles Batchelor, April 27th, 1887


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[D8737AAS], Test Report, Charles Batchelor, April 27th, 1887

Editor's Notes

Document is incomplete. Page 5 of 6 is missing. "Heat in Armatures ## Experiments that have been going on since August 1886, to find a method of reducing the heat generated in the iron of an Edison Dynamo. The iron part of an armature without wire in every case was run at normal speed in a field charged to the same degree of saturation as when run on full load. The iron was covered with about 1/4" of felt and the temperature was taken (when inside) in one of the bolt holes & (when outside) on the surface of the iron. The temperature is corrected by observing the rate of fall perminate after it shows maximum and adding that fall per minute to the observed temperature #1 was a regular #12 armature covered with 1/4" felt, taped crossways and bound with string. Felt washers on ends. This armature consisted of 1061 discs weighing 197 lbs. Weight of a solid core of same size & allowing for all holes would be 244 lbs. therefore there is a paper in between sufficient to make the whole 80.7% of solid iron__ This is what we use now as a regular #12. From this we get .0126" as the average thickness of discs__ There are 11 sheets of paper to 5 of iron. Paper measures .0011" Test 3 hours__ Mean volts on field 96. Speed 1200 Readings every 1/2 hour__ Temperature of armature 62 degrees C, room 20 degrees C__ The felt used was loose quality__ ## #2 This was in all respects like #1 except that there was no insulation between the discs and the shaft but there was an iron sleeve fitted to the shaft but there was an iron sleeve fitted to the shaft in such a manner that the discs fitted snug to it average thickness of each disc was a little greater in this armature than on the other Volts in field 96. Speed 1200, run 3 hrs 5 min. Temp. 69 degrees C, room 16.5 degrees C, increase 52.5 degrees C or 25% more than #1 Felt on this test was loose quality ## #3. Size a regular #12__ Instead of paper between the discs, each disc was coated with a solution of Mr Edison's will stand great heat. These discs were coated and then put on a head that revolved them about 4 times a minute until they were dry. This process was faulty as although no perceptible difference could be detected in thickness they were found to be thicker near centre than near periphery so much so that they had to be compressed with 100 tons to get them into shape Diam. of iron was about 1/16 larger than #1 & #2 this would make a difference of 4% in heat. The number of discs was 1130 of .012". Resist. per inch was 2 ohms this would only give about 8 watts of heat, not worth taking account of__ Bolts insulated as usual and discs insulated from shaft. Test 3 hours__ Temp 75 degrees C, room 20 degrees C increase 55 degrees C This armature was covered with a very close texture felt and two layers ## #4 Test of #1 with the new close felt increase temp. 50 degrees C. We found the rate of cooling off at rest was .08 degrees per min. or .16%. Armature was then run 1/2 hour and cooled off 12% or .4% per minute; if all the heat had been kept in it would have reached 86 degree increase. This heat is 20% more than on #1 test, but that showed a decreasing temperature of 1 1/2 times that of this therefore the loose felt is only 1/2 as good__ Calculating from this #1 armature would have been 88 degrees C increase. ## #5 Armature with discs coated with Edisons compund was now run with the new felt increase 55 degrees C ## #6 A regular #16 armature with regular .012" discs__ 3 hours 5 min.__ Volts 90 speed 995__ Armature 1/16 larger than usual__ increase 40.5 degrees C. New Felt__ ## #7 A regular #16 Armature with discs of .0065" thick__ same time and condition as #6__ Increase 24 degrees C ## #8 A regular #12 same as #2 but a bronze sleeve instead of an iron one and the new feet. Increase 52.5 degrees C [Page 5 of document is missing] regular. There seems to be no difference between the 'Bronze sleeve' & the regular with same felt though the Bronze sleeve seemed to cool off through the shaft a good deal. It cooled off more rapidly from bolt hole than from outside ## The difference between thick & thin plates is nearly 50%__ The thin plates hear about 55% of the regular but the total increase is so small that it is probable the percentage is much less ## We are now trying an armature with their discs, painted, & with japanned bronze bush."



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