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Aerodynamic and Hydrodynamic Bearings

The most commonly used and most numerous Aerodynamic bearing in the World is the slider bearing that is used in all computer Hard Disc Drives, it is known as a Flying Head. Also the new Hard Disc Drives are using a Grooved Hydrodynamic Bearing as the main spindle bearing. The numbers of these bearings in daily use must now be numbered in millions.

The reason for the development of these bearings has been to promote operation at high rotational accuracy so that Data Tracks of the order of 30,000 Tracks Per Inch can be reliably used.

Aerodynamic and Hydrodynamic Bearings are made in a variety of different types, but all types rely on the relative velocity between the bearing surfaces to entrain the fluid into the bearing clearance and generate a pressure profile. The slider and plain cylindrical journal bearing shown below in the sketches show this latter principle.

Click on image to enlarge

 
Hemispherical Oil Bearing
However, the inclined grooved bearing is probably the most popular type of self -acting bearing as it can develop pressure profiles under conditions of zero eccentricity or zero gravity and raise the speed at which instabilities occur {see sketches}.  

6 inch dia Hydrodynamic Bearing

FFD have designed and made Aerodynamic and Hydrodynamic bearings which have ranged from a 1.25 mm(0.050 inch) dia. hemispherical oil bearing to various Aerodynamic bearings and finally a Hydrodynamic bearing 6 inches (152.4mm) dia.

Is this the smallest hydrodynamic grooved bearing in the World?–

The magnified photograph* shows the Tungsten Carbide, 1.25 mm dia. hemispherical oil bearing. It was designed and made at FFD in co-operation with Mr F.Titcomb of Colorado Springs, USA. It was successfully tested as the main bearing for a prototype 1.3 inch dia. Hard Disc Drive Spindle. The bearing had a spherically concentric radial clearance of 0.0001 inch. The grooves were 0.007 inch wide and 0.0002 inch deep. The Lead Bronze bearing cup was diamond turned by a spherical generation machine developed at FFD for the project. At 6,000 rpm it carried a load of 0.5 lb (.0.22kg). Power dissipation was 0.002 Watts.

*Hemispherical Grooved Bearing 1.25 mm dia.