Fluid film bearing of hybrid device consists of orifice compensated annular thrust bearing and self-acting journal bearing. In series hybrid bearing, both ball bearing and annular thrust bearing carry full system thrust load, but two bearings share speed. Operation of system is stable and automatically fail-safe

Anderson, W. J.

Coe, H. H.

Fleming, D. P.

Parker, R. J.

English

NASA Technical Reports Server

June 1971	 Brief 71-10173 
•
	
NASA TECH BRIEF 
Lewis Research Center 
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 program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D. f. 20546. 
Series-Hybrid Bearing: An Approach to Extending

Bearing Fatigue Life at High Speeds 
A new high-speed hybrid bearing, consisting of a 
fluid film bearing coupled in series with a ball 
bearing (see fig.), reduces the DN value (D = bear-
ing bore number in mm; N = shaft speed in rpm) 
Fluid-Film Bearing 
Inner Member
Thermocouple 
Floating 
Housing
Inlet 
Test 
Bearing 
Lubricant 
Inlet 
Fluid-Film 
Bearing Outer 
Member
Thrust Load 
by approximately one-third. As a result, the fatigue 
life of a ball bearing in a 3 million DN application, 
for example, could be increased as much as eight 
times.
Recent developments in gas turbine engines have 
resulted in requirements for larger shaft diameters 
and higher main shaft bearing speeds. Future turbine 
engine requirements may include bearing DN values 
as high as 4 million. When ball bearings are 
operated at DN values above 2 million, centrifugal 
forces produced by the balls can be significant. The 
resulting increase in Hertz stresses at the outer-race 
ball contacts may seriously shorten bearing fatigue 
life. The hybrid bearing alleviates this condition. 
The fluid film bearing of the hybrid device con-
sists of an orifice-compensated annular thrust bear-
ing and a self-acting journal bearing. In the series-
hybrid bearing, both the ball bearing and the 
annular thrust bearing carry the full system thrust 
load, but the two bearings share the speed. 
As the hybrid system starts up, the ball bearing 
is operating at full speed and the fluid film bearing 
parts are running together. The ball bearing outer 
race is mounted in a stationary housing. The fluid 
film bearing outer member and the ball bearing 
inner race rotate as a unit and at such speed 
that the torques of the fluid film bearing and the 
ball bearing are equal. The centrifugal force on the 
oil in the rotating shaft generates hydraulic pressure 
to supply the pressurized thrust bearing. As soon 
as enough hydraulic pressure is generated to lift 
the applied thrust load, floating and sliding begins 
within the fluid film bearing. Rotational speed 
increases until the torque required equals the torque 
of the ball bearing. Thus, one element of the fluid 
film bearing rotates at shaft speed and the second 
element rotates with the inner race of the ball 
bearing, at a speed less than shaft speed. In this 
manner, speed is shared between the ball bearing 
and the fluid film bearing. (continued overleaf( 
115-Series 
Ball Bearing 
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=19710000172 2020-03-17T02:24:57+00:00Z
Notes: 
1. Operation of the system should be very stable 
since the fluid film bearing torque is a linear 
function of its sliding speed, while the ball 
bearing torque changes little with speed. 
2. The system is automatically fail-safe. Should the 
fluid film bearing seize, the ball bearing will 
merely take over and run at full speed. 
3. The following documentation may be obtained 
from: 
National Technical Information Service 
Springfield, Virginia 22151 
Single document price $3.00 
(or microfiche $0.95) 
Reference: 
NASA-TN-D-7011 (N71-l3071), Experi-
mental Evaluation of the Series-Hybrid Rol-
ling-Element Bearing 
4. Technical questions may be directed to: 
Technology Utilization Officer 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, Ohio 44135 
Reference: B71-10173
Patent status: 
This invention is owned by NASA, and a patent 
application has been filed. Royalty-free, nonexclu-
sive licenses for its commercial use will be granted 
by NASA. Inquiries concerning license rights should 
be made to: 
Patent Counsel 
Mail Stop 500-311 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, Ohio 44135 
Source: W. J. Anderson, R. J. Parker,

D. P. Fleming and H. H. Coe

Lewis Research Center

(LEW-1 1152) 
Brief 71-10173	 Category 07


Series-hybrid bearing - An approach to extending bearing fatigue life at high speeds

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