[D8830AAR], Test Report, Charles Summer Wirt, William J Jenks, May 24th, 1888


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[D8830AAR], Test Report, Charles Summer Wirt, William J Jenks, May 24th, 1888

Editor's Notes

"I have tested the latest pattern of switches made by B.+ Co. with the following results. ### Description--A double pole switch for house use having a revolving fourfaced spiral cam, with contact springs pressing against opposite faces, two of which are faced with copper/the cam and base of earthenware, cover and key of brass. ### I put on each switch current sufficient to raise the temperature of the contact to about I40 F., or as hot as the hand can bear, time being allowed for the temperature to become constant. The current in each case was.--- ### [List of currents follows] The 60 lt. switch should have carried at least 1/2 as much as the 120 lt., but did not do it. ### I have always thought it fair to rate a switch at one half the current taken on such a test as the above. This is very much a matter of opinion however. A little heat on this switch will not do any permanent injury, which is one great advantage of the insulating material used. ### I object to the shape of the cam as at present made, it gives the brush sever bond just before breaking contact while the tension in the normal closed position is small. There ought to be as much tension in the latter position as the material will stand without danger of being sprung, and as little tension as possible in other positions. I would have the metal faces of the cam made concentric, and the insulating faces of such shape as to relieve the brush of all tension in the normal open position. ### In the smaller sizes with the punched terminal pieces there is a tendency for the screws holding the brush to loosen with the vibration. I would have this remedied either by using solder in addition to the screws or else by substituting rivets. ### Mr. Edison suggests that capacity would be increased by splitting the brush and by using an end bearing as on a dynamo brush. I am afraid of the metal cover coming so close to the conductors. There are rivets going through the insulation and chances for trouble are good. ### The new terminal used on larger sizes makes good connection if your line happens to consist of TWO wires fitting the holes. In practice they will be an informal nuisance. I know that B. & Co. have tried faithfully to produce a god terminal I am perfectly satisfied that the only fit way to connect these it so use solder. The sooner we come to it the better." Charles Wirt






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