Paper 4: Some Experiments upon the Behaviour of Hypoid Oils in Heavily Loaded Contacts

Abstract

Measurements have been made over a wide range of speed and temperature of the thickness of the oil film between rotating crossed-cylinders of hardened steel lubricated with a hypoid base oil and with the base oil compounded with a range of E.P. additives. These values of the film thickness agree well with those found in previous studies of elastohydrodynamic lubrication. It has been shown that the addition of the E.P. additives has no appreciable effect upon the thickness of the film. It is deduced from these studies that an oil film of appreciable thickness must exist between the teeth of hypoid gears over a wide range of operating conditions; the major mechanism of lubrication in a hypoid gear is, therefore, elastohydrodynamic and the main function of E.P. additives is to prevent the initiation of catastrophic forms of failure by local penetration of this hydrodynamic film.