[LB009489], Letter from Thomas Alva Edison to Charles Batchelor, December 31st, 1881


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[LB009489], Letter from Thomas Alva Edison to Charles Batchelor, December 31st, 1881

Editor's Notes

In putting out a great number of plants as we are now doing we have found it necessary to have a Regulator for the candle power If our lamps as the parties using the light are apt to run the lamps up very high & thus cause a great many breakages. Thus the average life would be shortened great dissatisfaction caused a people get the impression that run statement as to life were not true. So I have devised an Indicator which works beautifully and I advise that hereafter all Isolated Plants shall be accompanied by [--] of them. I will send you one with your model "Z" Dynamo provided [---] patents have been resulted in [Preece] and [----] [---]. It consists of an apparatus which is plated across the iron just as if it [were] an ordinary lamp. It has a magnet with [illegible] the magnet a resistance of seventy ohms & In the same circuit is seventy [three] resistance making a total resistance equal to the lamp. This magnet is provided with an armature (about four inches long and an inch thick) of iron fastened to a large sliding armature lever arranged to work the same as a relay. A large brass spiral spring made of 1/8 in with the spiral doing about 3/4 in diamater & 4 in long is used to adjust it and is arranged so that with the proper adjustment is obtained it cannot alter. The whole thing is enclosed in a box. The big magnet acting as a relay closed the circuit on which there is a vibrating burglar alarm [and] which makes a great noise the circuit being a delivered one closed round one of the resistances of the device enough current is obtained to ring the bell violently.##The machine is set in the following manner. Suppose that we sent out a Dynamo machine and lamps which give sixteen candles at one hundred volts. Then we take one of these boxes and put it on a circuit which is just 100 volts & so adjust the armature of the Regulator that by increasing the volt by one the [rise] of current will attract the armature close the delivered circuit and the bell will commense to ring One volt only makes a difference of half a candle but the bell always works on this variation. Now you see if this the Regulator is put in the Lamp circuit & the machine is first started & the bell rings the attendant at once knows the candle power is too high and he adjusts the field magnets resistance just enough to stop the bell ringing & then he knows his lamps are not more than sixteen candle & thereafter it is impossible for any of the lamps to go above 16 1/2 candles without the bell ringing##We find this apparatus is very reliable & brings out very conspicuously the bad governing of our small engine when the B lamps are used the extra 70 ohm resistance is [taken] out leaving only the magnet in which is the same resistance as the B lamps. So all you have to do is that when you send out a plant you must adjust the Indicating machine at your Works and send it out with it. It is so reliable that we shall use it in the Central station in the place of an Electric Dynameter for guaging the volts. Bergmann remaking them at $25.00 but we hope to get them much cheaper than that.##We received your cable about the model Z Dynamo. This will be sent to you very shortly via [Hamburg] You must not take it into France until you have got the proper authorization from the authorities as it is necessary to take very great csre that nothing is done to violate the patents The Paris Opera House Dynamo were ordered to be shipped to Puskas & Bailey. If I had done so my patents would have been endangered. I sent them to Geo Walker as Exhibition material. In ordering stuff from here you must be very careful about this authorization & even when you have the authority I shall always ship to Hamburg & let you get the forwarding done at your end. I am told that anything imported without the proper authorization vitiates the patent and can be taken advantage of by our competitors and that the authorities cannot make a [retrospective] authorization so as to make the patent good again. they cannot legally do so according to French law.##We are building a model Disc Dynamo for B lamps the same as you have at Paris and which was built at menlo SPark. We can send you the working drawings of the armature after we have phonograph tested it if you desire.##Regarding the large Dynamo we are building six for the Illuminating Coy and could start another one on a model for. You but would like to have the Coy over there send a formal order. However I think the drawings will be sufficient for you as we have got them absolutely correct so I think you can do just as well with them with explanations from us just as well as with a model Dynamo.##I spend a great portion of my time now at the Lamp Factory Upton had got badly worried regarding the life of the lamps but now we make a [curve] of each days run so we know exactly what we [are] about and those curves show that the [Six] per Horsepower have an average life exceeding eight hundred hours and I am gradually increasing this. I am also working on spirals with great success. I shall undoubtedly succeed in making 280 ohm A lamps 12 per horse power 600 hour life but do not promise this. this is of course sub [-osa]. I shall also be able in the course of six or seven weeks to materially reduce the cost of the lamps so that we can make some profit on them.##We sold 2000 resistance lamps to the Western Union to be used as Resistance in their telegraph lines at seventy five cents each.##We have had the steam on the big English machine (for spare) we had 1300 lamps on it for several weeks we havse some trouble with the business but I shall get them all right in a day or so & then shall ship the machine to Johnson.##We are progressing very well with the Rail Road. The locomotive is being built at [Goerck] St & will be finished in a week or so. Hughes is laying the track





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