Research program studies behavior of specific high-speed, angular-contact ball bearings. Program is aimed at detailed investigation of ball-separator behavior and lubrication surface-finish effects in a specific gyro wheel

Geer, T. E.

Kannel, J. W.

Stockwell, R. D.

Walters, C. T.

Wilson, W. R. D.

English

NASA Technical Reports Server

September 1969
	 Brief 69-10367 
NASA 'TECH BRIEF 
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from the Clearinghouse for Federal Scientific and Technical Information; Springfield, Virginia 22151.. 
•...	 '	 _______________ 
Study of High-Speed Angular-Contact

Ball Bearings Under Dynamic Load 
A'resëarch program has been conducted to inves-
tigate the behavior of specific high-speed, angular-
contact ball bearings. The program was a continuation 
of the effort to isolate several probable causes of 
ball-bearing "failure" in a specific gyro wheel. The 
present program was aimed specifically at detailed 
investigation of two of these potential causes, namely, 
the ball-separator behavior, and lubrication surface-
finish effects. The ball separator has been investigated 
with respect to dynamic behavior, materials, and 
geometric design. The effects and functions of lubri-
cation and raceway finish have been studied from the 
viewpoint of lubricant-film generation, lubricant 
flow, and traction forces. In addition, the bearing-
dynamics-analysis program, which was previously 
developed, has been extended through development 
of a companion program for analysis of ball and sep-
arator dynamics. Both of these programs were used 
for extended studies of the dynamic effects on pre-
cision bearings due to the presence of the ball sep-
arator. 
Experimental measurements of gyro-bearing lubri-
cant-film thickness and traction characteristics were 
performed in the rolling-disk configuration to verify 
lubrication models for calculations of bearing dynam-
ics. Values of rheological model parameters were de-
termined that fit the experimental data for the load 
and contact-residence time conditions of interest in 
the gyro-bearing configuration. Mathematical tech-
niques and approximations were developed to effi-
ciently calculate the total tractive force and moment 
at a ball/race contact in the analysis of bearing dy-
namics. 
Verifying experiments were also conducted for 
models of the tractive force between the ball and the 
.,
ball separator. A gyro-bearing-scale-traction appa-
ratus was developed with a measuring sensitivity of 
±0.01 gm force. Measurements of traction in the 
range of 0.2 to 1.0 grn force were obtained for speeds 
ranging from 24,000 to 36,000 rpm and loads ranging 
from 2 to 10 gm force. Results were in reasonable 
agreement with the theory when meagerness of the 
lubricant was accounted for. 
Theoretical analyses and rolling-disk experiments 
were performed to assess the effects of roughened 
surfaces on elastohydrodynamic lubrication. Average 
film thicknesses found for transverse and circumfer-
ential roughness lay were higher than those for smooth 
surfaces. Significant reductions in traction were 
found for the circumferential roughness lay in the 
gyro-bearing operating range of conditions. 
Lubrication models for each of the types of bearing 
contact were incorporated into the bearing-dynamics 
analysis program. This digital computer program pro-
vides a numerical solution of the complete set of equa-
tions of motion for the moving elements of an angular-
contact ball bearing. Analyses of the current gyro wheel 
geometry were performed using the program for the 
conditions of an oversize ball and race misalignment. 
Several interesting general features of ball and sep-
arator motion in high-speed bearing operation were 
noted that have not previously been calculated Re-
sults also revealed a separator/race contact drive 
mechanism for the ball-separator-whirl instability. 
Several potential ball-separator material and geom-
etry improvements have been conceived. Relatively 
new high-temperature polymers, such as Polyimide 
and Pyrrones, were found to offer several potential 
advantages over Synthane and Nylasint. Geometry 
changes in the pocket and at the outer race contact 
(continued overleaf) 
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were conceived which may offer improved separator 
stability and lower torque and associated frictional 
heating. 
Experimental measurements of ball/race lubricant-
film thickness were obtained from operating gyro-
wheels to assess the effects of raceway-surface 
apparatus were improved and experimental results 
are believed to be more reliable quantitatively than 
in previous research. Results showed considerable 
differences in film-thickness behavior between the 
smooth and the roughened race; however, theory and 
rolling-disk data explain the differences in the inter-
mediate and high speed ranges fairly well. It now 
appears that the surface-finish theory and experi-
ments can be used to design a surface that will pro-
vide lower ball/race traction with adequate minimum 
film thickness. 
Notes: 
1. It is believed that the state of theoretical predic-
tion of lubrication processes and dynamic behavior 
in gyro bearings has progressed to the point that 
significant improvements in bearing performance
can now be realized. Future research tasks should 
be conducted in the areas of ball-separator geom-
etry, ball-separator material, and raceway surface 
finish. Modifications in geometry suggested by 
analyses must be checked for practicality and then 
further analyzed using the bearing dynamics anal-
ysis program. 
2. Documentation is available from: 
Clearinghouse for Federal Scientific 
and Technical Information 
Springfield, Virginia 22151 
Price $3.00 
Reference: TSP69- 10367 
Patent status: 
No patent action is contemplated by NASA. 
Source: C. T. Walters, J. W. Kañnel, W. R. D. 
Wilson, T. E. Geer and R. D. Stockwell of 
Battelle Memorial Institute 
under contract to 
Marshall Space Flight Center 
(M FS-20562)
. 
. 
Brief 69-10367	 Category 05


Study of high-speed angular-contact ball bearings under dynamic load

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