[LB011401], Letter from Thomas Alva Edison to Edward Hibberd Johnson, March 7th, 1882


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[LB011401], Letter from Thomas Alva Edison to Edward Hibberd Johnson, March 7th, 1882

Editor's Notes

I can probably arrange to go over to England in the course of three or four months, i.e. when we have got the Central Station fairly started here and provided the [p--a---] does not arise in the meantime.##The bar armatures sent you will prove far superior to the one that Batchelor had and will give an exonomy of about 96% of which about 90% will be available outside when 12 h.p. is being taken off it. It is the most perfect machine we ever made and has only about eighteen thousandths resistance with only the same size as the regular B armature and about the ame radiating surface. You can run easily 250 B lamps on it and I think it will carry 115 to 125 of the 16 candle B lamps without any difficulty. It will greatly astonish Sir William Thomson when he comes to test it. You can put it in any one of the Z Dynamos and there will be quarter of an inch clear piece that you can look through Get sir William to make a test of it in the same way that howell made his test both as to [scientific] and commercial efficiency and I feel convinced that if he makes this test, he will have to admit that my machine is the most perfect of all machines yet devised and leaves nothing to be desired or possible##These machines are rather costly or rather the armature is. But they can be made quite reasonably providing 100 or 150 were ordered to warrant us in making a lot of special tools to enable us to turn out the work cheaply.##You speak in one of your letters about some of the machines heating and others not. You know that if the brushes are set exactly on the neutral [point] [--- ---] the brushes on the commutator block which is exactly opposite the centre of the field piece all the machines will have the same electro motive force providing all the fields are arranged in [get] the same [illegible] the fifth one has its brushes set say several blocks [removed] from the centre and the direction of rotation it will diminish the electro motive force of that machine and it will become less heated than the others. If you have five machines and four of them have the points of the brushes set up more towards the opening while the fifth one is set exactly right the fifth one will give the highest electromotive force and do the greatest amount of work and become heated. If the four machines had their brushes set away so as to be on a [line] with the block at the opening of the field there would be no current at all given from these machines and the fifth one would have to do all the work so you can see how a slight change in the position of the brushes will cause a machine to easily run abnormal load and doubtless this is the cause of your troubles##Please let me have your views as to the disposition of the Exhibit now at Crystal Palace. Gouraud I fancy wants to make a permanent exhibitin of the thing there. I want you to tell me what you think about it and where they should go after the exhibition closes.##Swan promised Barker some Swan lamps and said he was to get them from Montgomery the Swan Coy's agent here. Barker cannot get them and wants you to see what you can do. He wants about half a dozen##Can you get from the United Telephone Coy half a dozen or a dozen of the motograph Telephones made for the Edison Co [---] Bergmann. They do not use them and I think they ought to let you have them for me. Barker wants six of these






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