STUDY OF HELICOPER GEAR LUBRICATION.
Quarterly progress rept. no. 2, Jun-Aug 65,
SHELL OIL CO WOOD RIVER ILL RESEARCH LAB
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Studies of the effect of gear-tooth surface pretreatments on gear performance were continued. Two surface precoatings, one obtained with Parco Lubrite solution and one with trichloroacetic acid, were found to increase greatly the constant load gear fatigue life, the former consistently, and the latter under some conditions of operation. A 30 reduction in load with the untreated gears was necessary in order to achieve the same constant load life as obtained with Parco Lubritetreated gears at 6400 rpm. In other experiments, improvement of the surface finish by lapping resulted in improvements in gear life of about two to four times that of the untreated gears, the greater improvement being at low speed. None of the pretreatments significantly affected the score load of a MIL-L-23699 oil. In break-in studies employing a loading schedule in which the load was increased stepwise, it was found that neither operation for a long prior period at low load nor elimination of the low-load steps had any significant effect on the eventual failure load, or the mode of failure. In tests with a synthetic base oil on the Rotary Contact Simulator, in which various points on the gear tooth profile were simulated, immediate scoring occurred on the disks simulating the tips, and areas near the tips, of the pinion and gear addenda. In every case of scoring, the mating disks, representing the corresponding dedenda, had undergone considerable surface cracking and sometimes pitting. Between these extremities on the gear-tooth active profile no failures occurred. Author