Highly precise air bearings for suspending objects over an epoxy flat floor in a laboratory have been developed. These bearings float on airgaps 3 to 5 mil (about 0.08 to 0.13 mm) thick. They are modern versions of precise air bearings, developed during the 1960s, that offer a working coefficient of friction of only 1/16,000. The basic design of these bearings can be scaled easily for different loads and airflows.

When more air bearings were needed in the laboratory, commercial air bearings were evaluated and found not to afford stability of airgaps comparable to that of the 1960s air bearings. The shop in which the 1960s air bearings were built had been disbanded before 1986 and the original drawings lost. Hence, it was decided to design and build modern versions of the 1960s air bearings.

Each of the 1960s air bearings includes precise brass orifices pressed into recesses on the bottom surface of a bottom section. After insertion of the orifices, the bottom surface was manually lapped to a precise flatness. On top of the bearing, there is a complex conical section with a spherical knob that fits into a socket in the experimental apparatus with which the bearing is to be used. The conical top section is sealed to the bottom section by use of an O ring and rings of many bolts.

The bottom section of a bearing of the present improved type is slowly and precisely machined from a single piece of aluminum. The machining yields the requisite flatness; precise lapping is not needed for flatness, though simple lapping can be performed to remove tooling marks. Spherical relief recesses are machined on both sides of each orifice of an integral annular plenum; this aspect of the design reduces (in comparison with the corresponding aspects of designs of other air bearings) turbulence in the air flowing out of the bearing and facilitates cleaning.

The top section, made from a simple flat plate, includes a simple ball nose recess sealed with grease. The top section is attached to the bottom section by four to eight bolts. The air bearing is attached, by means of a threaded ball bearing, to the apparatus with which it is to be used.

This work was done by Charles T. Cowen of Marshall Space Flight Center.

NASA Tech Briefs Magazine

This article first appeared in the November, 2002 issue of NASA Tech Briefs Magazine.

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