Experimental tests are conducted on squeeze-film bearings by applying electricity to piezoelectric ceramics, causing vibrations at thousands or millions of Hz that are amplified and transmitted to the bearing. Rotor operation through 24,000 rpm without whirl instability proved bearing ability to support rotor weight without hydrodynamic action

Chiang, T.

Smith, R. L.

English

NASA Technical Reports Server

3 earn 
Flexure) 
December 1970
	
Brief 70-10389 
NASA TECH BRIEF 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage commercial 
application. Tech Briefs are available on a subscription basis from the National Technical Information Service, Springfield, 
Virginia 22151. Requests for individual copies or questions relating to the Tech Brief progam may be directed to the Tech-
nology Utilization Division, NASA, Code UT, Washington, D.C. 20546. 
Hydrodynamic Squeeze-Film Bearings for Gyroscopes 
For the past six years, intensive studies have been 
conducted on squeeze-film bearings and grease or oil 
bearings for gyroscopes and high angular momentum 
wheels. Squeeze film bearings operate on a vibration 
principle and can be considered, in some respects, 
as self pressurizing bearings. Primary advantages are: 
compactness; simple construction; easy regulation; 
Piezocerarnic Bar 
and minimal friction, requiring only the use of ambient 
gas as a lubricant. 
Grease or oil bearings are cones or spheres resting 
in receptacles of matching shape. Spiral grooves are 
carefully etched or machined into the bearing so that 
the lubricant is carried by the grooves as the bearing 
turns. This forces the lubricant to the bearing apex,
where enough pressure is generated to hold the bearing 
free of the receptacle. 
Testing was carried out by applying electricity 
to piezoelectric ceramics, causing vibrations at thou-
sands or millions of Hz that were amplified and trans-
mitted to the bearing. The first cycle or two separated 
the journal from the bearing and admitted air to the 
minute space between them. The continued vibration 
held the contained air to an average pressure that was 
higher than ambient and prevented the opposed sur-
faces from touching. These bearings are quite different 
from hydrostatic bearings ("air bearings") which re-
quire constant play of a stream of air between the 
surfaces. Tech Brief B68-10180 describes the concept 
in detail (see fig.). 
The rotor ran smoothly through 24,000 rpm without 
apparent whirl instability. The queeze-film transducer 
provided a squeeze amplitude up to 400 /.tin, peak to 
peak at a frequency of 4800 Hz. The squeeze-film 
bearing proved its ability to support the rotor's 
weight (0.3 lb) without the hydrodynamic action. 
Start-up and coast-down data from the rotor were 
taken both with and without the squeeze-film action. 
During both start-up and coast-down the squeeze-
film bearing helped to maintain a gas film; the effect 
is more evident in the coast-down data. The existence 
of the gas film during starts and stops eliminates 
sliding damage and reduces criticality of surface-mate-
rial problems. Since the start-up friction accounted for 
about 50% of the available motor torque, the squeeze-
film action also eases electrical design requirements 
of the spin motor. Thus the fundamental feasibility and 
the conceptual validity of squeeze-film assistance for 
the hydrodynamic, gas-lubricated, spin-axis bearing 
during starting and stopping have been experimentally 
demonstrated. 
This document was prepared under the sponsorship of the National	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States	 will be free from privately owned.rights.
https://ntrs.nasa.gov/search.jsp?R=19700000375 2020-03-17T00:43:50+00:00Z
Patent status: 
No patent action is contemplated by NASA. 
Source: T. Chiang and R. L. Smith of 
Mechanical Technology, Inc. 
under contract to 
Marshall Space Flight Center 
(MFS-20802)
Note: 
Requests for further information may be directed 
to
Technology Utilization Officer 
Code A&TS-TU 
Marshall Space Flight Center 
Huntsville, Alabama 35812 
Reference: TSP70-10389
L:] 
Brief 70-10389	 Category 07


Hydrodynamic squeeze-film bearings for gyroscopes

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