The vibration of electric contacts

I. R. Schumaker (nonmember; General Electric Company, Schenectady, N. Y.): The authors have stated that “considerable attention has been given to the study of current-carrying ability and circuit-interruption ability of contacts, while the ‘making’ of contacts has been practically neglected.” It is not to be assumed that little is being done on this score just because little or nothing has been published about it. Several years ago some 12 contact-testing machines were produced for member companies of the American Society for Testing Materials subcommittee on contacts to the specifications of that subcommittee and for the sole purpose of testing contact-making ability. This would indicate that considerable work had been done before that time and that an even more concerted effort is being made now. In addition, the demands of our Air Forces in this war for contactors and relays that will do tremendous jobs in small-sized packages has given the manufacturers an even greater realization of the problems involved in the “making” of an electrical circuit. However, the data that have been taken up to this point are so inconsistent that it is difficult to arrive at any conclusions. To be more specific, seven of the ASTM machines operating under the same conditions of load, speed, and pressure and using tips made by the same manufacturer in the same lot, showed a variation in total number of welds after 250,000 operations of 2 for one machine to 500 for another, with the others well distributed between these limits!