Abstract :
W. C. Kalb (National Carbon Company, Inc., Cleveland, Ohio): Mention is made in the paper by E. R. Summers and J. F. Settle of the rapid brush wear experienced on synchronous-converter rings under conditions of very low humidity. This effect was known to most brush manufacturers. Therefore, when extremely short brush life first was encountered in high-altitude flight, it was but natural to assume that this was due, at least in part, to the low humidity known to prevail at high elevation. Although the view was held in some quarters that other factors were the major cause of high-altitude brush failure, the investigations made by Doctor Ramadanoff and Doctor Glass, as demonstrated at this meeting, provide convincing evidence that low humidity and meager oxygen supply are the major factors contributing to rapid brush wear.
