The Testing of Brushes for Life and Performance Under Various Altitude Conditions

This paper presents the author's experience in the testing of brushes on machines intended for high-altitude service on aircraft equipment. The procedure and range of conditions found useful in testing a wide variety of small a-c and d-c machines are outlined in detail. It is hoped that other investigators will contribute their experiences through discussions or additional papers, and that from this material there may be developed a suitable test code, supplementing the present Institute test code for d-c machines. The only real criterion of brush performance is that of actual experience in service, since all of the infinite variety of conditions that affect brush performance cannot be anticipated under test conditions. However carefully conducted tests over a range of specified conditions do provide a good basis for brush selection and greatly expedite the final choice for the best over-all performance. For this reason, and because it will be helpful to investigators in comparing their results, it is hoped that the proposed brush test code may be undertaken in the near future.