Aerostatic or Hydrostatic Bearings

The overwhelming majority of bearings in industrial use are of the Aerostatic type, i.e. often known as air bearings if air is the working gas.

Bearings of this type require a supply of fluid from an external source that is then passed through the bearing film and is discharged to an external ambient environment. The property of a bearing of this type is that it will have load carrying capacity and film stiffness at zero rotational speed. {As an approximate design guide a journal bearing where the length (L) is equal to the diameter (D), supplied with a supply pressure (P) will carry a Load (W), where W = 0.25x{LxD²xP}. Figure 1 and Figure 2 illustrate the working principles.

As the journal bearing rotates an added load bonus exists due to relative motion of the bearing surfaces. However, in the case of the thrust bearing this bonus does not occur.

FFD have designed and made Aerostatic journal bearings from 1.8mm diameter (0.075 inch) to support a tungsten carbide pin, to journals 15 inch in diameter for a special purpose machine tool.

FFD have supplied thrust bearings 14 inch(355mm) diameter carrying tons of load. They have also supplied different sizes of spherical Aerostatic bearings for special purpose applications.

Diagram of Spherical Air Bearing

Click on image to enlarge Figure 1 Figure 2