Foil bearings are a type of air bearing. A shaft is supported by a compliant, spring loaded foil journal lining. Once the shaft is spinning fast enough, the working fluid (usually air), pushes the foil away from the shaft so that there is then no contact. The shaft and foil are separated by the air's high pressure which is generated by the rotation which pulls gas into the bearing via viscosity effects. A high speed of the shaft with respect to the foil is required to initiate the air gap, and once this has been achieved, no wear occurs. Unlike aero or hydrostatic bearings, foil bearings require no external pressurisation system for the working fluid, so the hydrodynamic bearing is self-starting. http://en.wikipedia.org/wiki/Foil_bearing A company that makes them... http://www.newwayairbearings.com/
Not many have because they will last forever! Engineers don't want stuff to last for they make their salary on fixing stuff that breaks down over time. Please Register or Log in to view the hidden image!
That sounds pretty cool, but the wikipedia article is relatively short and begs some questions. Where does the air come from? Is the bearing sealed or does it draw ambient air? I'm asking because I want to know if these can be used at high altitudes or even space.
I would question if it is truly frictionless (air friction would still apply, even to a rotational force) but they are certainly better than ball-bearing and the like! Very cool!
