[LB007816], Letter from Thomas Alva Edison to William Joseph Hammer, July 28th, 1882


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[LB007816], Letter from Thomas Alva Edison to William Joseph Hammer, July 28th, 1882

Editor's Notes

Did you receive a letter which I sent to E.H.J wherein I explained the great importance on the 250 Light machines of setting the brushes in the direction of rotation to the non-sparking point For fear that Johnson did not give it to you I will again state that the K or 250 Light machines will give 1300[--] volts when load is on and when the brushes are set a right angles to the slot or open part of the field but the sparking is very great but If the arm is moved in the direction of rotation you will reach a point where there will be absolutely no sparking and you will still have sufficient Volts hence in practice we we find that the R machine gives the [least] trouble with the brushes then the Z This cannot be done on the 60 Light or Z for the reason that it does not give Volts enough to prevent of putting the brushes in the direction of rotation to [buy] [great] [e--sil] If it is attempted to set the Z brushes away up towards the top where there is no spark the Volts will fall as [low] as 85 But I have made the K and the new L or 150 light which you will soon receive so powerful & with such an excess of Volts that you can avail of and use the non-sparking point & still have sufficient Volts to bring the lamps up to proper candle power & also [lose] several percent on the Conductors if the brushes are set at the non-sparking paint with the full load & 1/2 are taken off it will spark slightly, as the non-sparking point is now nearer to the old place in one special Experiment on our L machine we adjusted the brushes in the direction of rotation so far that these were at right angles to the brushes position on the Z. & still we had enough volts to bring the lamps [up] You showed "[hammer] this dodge in all our men who put up plants there for the reason that in the old position [L] bar loops around the armature was short circuted all the time one brush touching two blocks of course short ckts one loop & the other does the same and this shortcircuiting is done in a strong part of the field & the powerful Current circulating in this circuit of extremely low resistance produces powerful sparks on the brushes. If now the latter is moved in the direction of rotation [as] it approaches & shortckts loops which are in weaker field hence the sparking is diminished & the economy increased. This effect takes place of course on the K. & .L. on the K & K we get 1/2 a light more per indirect[ed] H.p. The reason why we did not try it on the large machine before was the belief that the Volts or pressure would fall too low but by Connecting up the field in 3 we were enabled to put we have 3 different varities of Automatic regulators to go with Isolated plants working at Menlo going through the Evolution test & I think one of them will prove reliable Did E H. J write you about running a feeder or feeders out of your H [[adest] station when you increase your lamp so as to keep the pressure on your [distributing] mains even & have all your drop of E.M.F in the feeder. Please show this letter to Dr. Fleming.




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