Thomas Alva Edison, Journal Notes, page x, 187x

Thomas Alva Edison, Journal Notes, pages 2 - 3, 1875 2 perfect and conspicuous copies ever taken on the Autographic press were taken this evening with ink formed of printers ink thinned by castor oil and ground in a mortar some two weeks previously. October 3, 1875 Thos A Edison. Chas Batchelor. James Adams No 2 Electric Pen In testing a new model pen this evening, one with all the mechanisms put in an iron frame (cast) we found that it did not approach in power or speed the rubber frame pen made by John Ott. The spools of the iron frame pen were two sizes of wire longer than Otts magnets. Thinking perhaps that the resistance was too great or that owing to the greater number of convolutions the self induction delayed magnetization we unwound one layer from each spool, but this did not appear to increase the power or speed materially. We then tested R on Galvanometer of both pens & found them about the same. We used the cast iron frame as a yoke to the engine magnet and found by testing that there were free poles at the poles where the cores are connected to the cast iron back. These free poles became nearly as strong when the armature was in contact with the regular poles, as the regular poles we then in addition to the cast iron yoke inserted a small soft iron yoke about 3 - 64 thick. This made some difference in the speed still there were free poles. We then took the magnet out of the engine frame for testing, found that with the small soft iron back there was scarcely any free poles when the front armature was not in contact with the cores. This armature is 3 - 32 thick, but when in connection the free poles were very strong perhaps they would attract with a force almost equal to the regular ones, by making the armature thicker the free poles became stronger If the yoke was increased in thickness the free poles became weaker and it is very probably that 3 if both the yokes cores and armatures had the same mass of metal and all in good contact no magnetism or free poles could be detected but the moment the iron circuit, or perhaps we might call it the magnetic circuit was weakened by decreasing the mass of the iron at any one point free poles would appear at that point, hence to obtain the maximum power the mass of iron in the yoke should be so great as to offer but little resistance to the passage of the magnetism so as not to cause free poles to go to the point of greatest .R. those in front of the the armature, and it may be found that a thin armature will increase this tendency by increasing the resistance we also discovered a Phenomenon. thus with a thick armature and back or yoke considerably thinner a nail was attracted only on opening and closing the circuit further tests should be given this and the armature& yoke proportions. Oct 6th 1875. All night Thos. Edison Chas. Batchelor James Adams Autographic Pen No 3 Worked on pen all night. (model pen) found that cams gave vibrating pen too great a movement (ie) three times more movement that was necessary to puncture the paper, hence engine had to do more work, altered it so that it would give much less movement. There was a great improvement in the speed of the engine, but not enough to account for the unsatisfactory working of the pen. We tested Writer Thomas Alva Edison Date written 1875 Paper x in x x in Pen Penmanship Style Collection Courtesy of Thomas Edison National Historical Park The Thomas Edison Papers, Rutgers University [1] Link for electric pen Electricpen.org[2] File name Edison Thomas Alva 1847-001-001-001