STUDY OF HELICOPTER GEAR LUBRICATION.
Quarterly progress rept. no. 1, Mar-May 65,
SHELL OIL CO WOOD RIVER ILL RESEARCH LAB
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Two main subjects are treated the first is the effect of several gear surface precoatings on gear performance the second is the gear performance of a typical synthetic, tetraester, five-centistoke base oil. It was found that precoating gears by heating in atmospheres of air, or a diester base oil, had little effect on the score load of a MIL-L-23699 test oil, while gears treated in a nitrogen atmosphere gave an increase in score load. Fatigue life as measured by the time to pitting failure, on the other hand, was considerably affected by the precoatings, particularly at high speed. In constant load tests at 6400 rpm it was found that the diester oil precoating extended gear life by a factor greater than seven, while the air precoating increased life three times. Under these same conditions the nitrogen treatment had no effect on gear life. While the coating techniques investigated represent only an initial attempt in this field, the improvement in performance is sufficient to warrant further study. From tests with the synthetic base oil, it was found that this oil is rather insensitive to break-in, and that fatigue failures occurred by fatigue-scoring rather than by pitting. The purpose of these tests was to develop groundwork for future exploratory studies involving the effects of EP additives on gear performance. Author