Dry solids, such as graphite or molybdenum disulfide, have had very limited use as lubricants for gears. More often such solids are used in conjunction with fluids for gear lubrication. Such use is not general and data as to their value is meager.
A large gear on a radar installation was said to be difficult to move until molybdenum disulfide was mixed with the oil used. Vago^50 cites gears operating in excess of 200 degree (F) where both automotive gear oil and a molybdenum disulfide fortified lubricant were tested. After three years, inspection of the gear teeth indicated no advantage of the latter lubricant over “the chemically fortified gear oils”.
A large gear on a radar installation was said to be difficult to move until molybdenum disulfide was mixed with the oil used. Vago^50 cites gears operating in excess of 200 degree (F) where both automotive gear oil and a molybdenum disulfide fortified lubricant were tested. After three years, inspection of the gear teeth indicated no advantage of the latter lubricant over “the chemically fortified gear oils”.
If solids are included in gear oils, the particle size of the additives is of importance and should preferably be of colloidal size. Thus, Kyropoulos^28 in citing claims for a 20 per cent increase in efficiency with a worm gear unit after adding colloidal graphite, also stated that powdered graphite was not effective. While settling of the solid occurred in this case there was said to be no clogging of oil ducts.
No mention is made of the proportion of solids desirable, but one per cent of a colloidal suspension, which in turn contains 10 per cent of solids, is a normal dosage. This holds true for either graphite or molybdenum disulfide. The latter material has been recommended where there is impact loading, or oscillating or reversing motion.
