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A computer program has been developed to design external spur gears having normal contact ratios (<2.0) and high contact ratios ( 2 2.0). This program has been used to study the efects of changes in some gear parameters on several performance factors of highcontact-ratio gears. The results are compared with those for the equivalent normal-contact-ratio gears.The study shows that a high-contact-ratio gear obtained by increasing the addendum of an equivalent normal-contact-ratio gear will have lower bending and compressive stresses (favorable) and increasedfriction heat generation andflarh temperatures (unfavorable).

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Sliding-rolling disk scuffing tests were conducted over a wide range of sliding and sum velocities, using a straight mineral oil and three aviation gas turbine synthetic oils in combination with two carburized steels and a nitrided steel. Geometrically-similar disks of two different sizes were tested in two different disk testers of nearly similar designs. In addition to disk size and metallurgy, the surface treatment, surface texture, and surface roughness of the disks were also varied. The investigation further covered variations in the oil supply configuration and flow rate. It is shown that the disk friction coefficient is dependent not only on the oil-metal combination, but also on the disk surface treatment and topography as well as the operating conditions. The quasi-steady disk surface temperature and the mean conjunction-inlet oil temperature are shown to be strongly influenced by the frictional power loss at the contact, but not by the specific makeup of the frictional power loss. They are also influenced by the heat transfer from the disks, mainly by convection to the oil and conduction through the shafts, which are dependent on system design and oil flow rate.