ABSTRACT
The essential factor in the lubrication of gearing, as with other mechanisms, is the maintenance of a fluid film between the surfaces of components with relative motion and mutual loading. By separating the surfaces in this way, there is a reduction in the degree of contact between the asperities on the mating parts. Inadequate separation leads to welding of the areas of contact, followed by tearing of the metal surfaces and the virtual destruction of the gears. In general, the higher the viscosity the more friction or ‘drag’ does the lubricant generate. The higher the frictional torque, the greater is the power loss in the gears and the lower is the mechanical efficiency. There is, of course, an economic incentive to reduce the power loss, since both running costs and the cost of initial equipment will be unnecessarily high. Lubricant viscosity governs the film thickness under elasto-hydrodynamic conditions. However, there is a practical limit to the viscosity from other considerations.
