This article reviews mathematical models for individual components associated with power losses, such as windage, churning, sliding and rolling friction losses.
Surface coatings or finishing processes are the future technologies
for improving the load carrying capacity of case hardened gears. With
the help of basic tests, the influence of different coatings and finishing
processes on efficiency and resistance to wear, scuffing, micropitting,
and macropitting is examined.
For a high-speed gearbox, an important part of power losses is due to the mesh. A global estimation is not possible and an analytical approach is necessary with evaluations of three different origins of power losses: friction in mesh contact, gear windage and pumping effect between teeth.
The following article is concerned with the analysis of the wear-reducing effect of PVD-coatings in gearings. Standardized test methods are used, which under near-real conditions enable
statements to be made about the different forms of damage and wear (micropitting, macropitting, scuffing).
Universal tractor transmission oil (UTTO) is multifunctional tractor oil formulated for use in transmissions, final drives, differentials, wet brakes, and hydraulic systems of farm tractors employing a common oil reservoir. In the present work, the gear protection properties of two formulated vegetable-based UTTO oils, one synthetic ester-based UTTO oil, one synthetic ester gear oil, and one mineral based UTTO oil are investigated.
Mineral-oil-base lubricants show a significant decrease of kinematic viscosity with rising temperature, as exemplified in Figure 1 by lubricants for vehicle gears. An important attribute of lubricants is their viscosity index (VI), according to DIN/ISO 2909 (Ref. 4). Viscosity index is a calculated coefficient, which characterizes the change of viscosity of lubricants as a function of temperature. A high viscosity index represents a low variation of viscosity due to temperature and vice versa. A low viscosity-temperature-dependence is required for lubricants that are operated at significantly varying temperature conditions, such as vehicle engine and gear lubricants in summer and winter time. This way, the oils remain flowing and pumpable at low temperatures on the one hand; and on the other hand, sufficiently thick lubricant films can be formed at higher temperatures for a safe separation of the surfaces.