This increases the load capacity significantly. The top foil is coated with Teflon-S or a polyamide coating to provide lubricity during starts and stops. The intermediate and top foils are attached to a key along one edge and are wound in opposite directions. The top foil has a thin coating that provides lubricity during startup and shutdown. A wedge is formed due to the radial displacements of the shaft as it rotates.
Hydrodynamic action draws the working gas into the wedge where it is locally compressed.
The corrugated foil acts as a spring to accommodate expansion, excursions, and any misalignment. It also provides a flow path for the cooling air to remove parasitic heat from the bearing. In the reversed multilayer foil bearing, the adjacent foils move in opposite directions. The net result is that relative movement is additive, which in turn produces high coulomb damping. N.Y. Both the bump foil and the top foil are spot-welded to the sleeve.