Bearing Lubrication
Bearing Lubrication The whole hub assembly is partially packed with grease. A radial-lip grease-seal is pressed inside the hub next to the larger bearing. The lip of the seal faces this bearing and fits over the cylindrically machined surface on the stub-axle. Over packing bearing hubs with grease causes churning and develops very high running temperatures. Due to high temperatures and excessive mechanical working the grease breaks down and becomes soft. The centrifugal force acting on the grease in the hub pushes soft grease outwards, so that it flows towards the lip seal and seeps past the seal lips. Bearing greases are based on mineral oil and to thicken the oil soaps of calcium, sodium, or lithium compounds are added. The consistency of a grease depends on the viscosity of the base oil as well as on the structure and properties of the metallic soap added. The three most important properties of a grease includes : (i) the melting temperature, at which the grease loses its semi-soli