Visualization technique produces a visual simulation of gas bearing operation by electronically combining the outputs from the clearance probes used to monitor bearing component motion. Computerized recordings of the probes output are processed, displayed on an oscilloscope screen and recorded with a high-speed motion picture camera

Evans, R. C.

Klassen, H. A.

Wong, R. Y.

English

NASA Technical Reports Server

T Li ii 
March 1969
	 Brief 69-10073 
NASA TECH BRIEF 
NASA Tech Briefs are issued to summarize specific innovations derived from the U.S. space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Electronic Visualization of Gas Bearing Behavior 
I------
Rigidly Mounted Pivot
scilloscope 
Probe 1
Capacitance Probe -
	
_(3_. Potentiometer 
Capacitance Probe 
Signal Conditioner	 ...>_. Summing Amplifier 
In experimental investigations of gas bearings for 
rotating machinery, clearance probes are often placed 
at various locations to monitor bearing component 
motion. To analyze bearing operation, it is neces-
sary to establish the relationship among the outputs 
of the various probes in order to determine the rela-
tive motions of the bearing components. The outputs 
from the clearance probes are usually displayed on the 
vertical axis of a multitrace oscilloscope or oscillo- 
graph with a time scale on the horizontal axis. In
analyzing these traces, the circumferential location 
of the probes must be carefully identified and small 
changes in phase relationship between the traces are 
not readily detectable. 
A visualization technique has been developed, by 
which the outputs from the various clearance probes 
were combined electronically to produce a visual sim-
ulation of bearing operation. In this simulation, the 
shaft journal appears as a circle on an oscilloscope 
with radial motions greatly exaggerated relative to the 
(continued overleaf( 
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size of the circle. The radial motions of the corners 
of the leading edge of one of the pads pivoting on one 
of the rigidly mounted pivots, and the radial motion 
of the flexibly mounted pivot, appear as moving points 
on the oscilloscope screen. 
Visual Display Procedure 
The clearance probes are of the capacitive type 
used for noncontact sensing connected to high-fre-
quency oscillator-amplifiers. A change in distance 
between the probe and the sensed object produces a 
proportional change in capacitance, which in turn 
changes the amplifier output voltage. 
At each bearing, two probes are mounted 90° from 
each other to sense shaft motions. A probe is mounted 
behind the flexible diaphragm directly over the pad 
pivot to sense pivot radial motion and diaphragm de-
flection. Two probes are used to measure the radial 
motion of the leading edge of one pad pivoting on one 
of the rigidly mounted pivots in each bearing. The 
capacitance probe outputs are recorded on magnetic 
tape. 
The taped signals are processed by an analog com-
puter to combine selected signals and to accurately 
establish the angular relation between the probes. The 
computer outpqt signals are displayed on an oscil-
loscope screen using four X—Y displays, and recorded 
with a high-speed motion picture camera. 
Actual shaft frequency was approximately 640 
hertz; but in order to visualize the bearing opera-
tion, a speed reduction factor of at least 320 was
needed. Part of this reduction was accomplished by 
reducing the tape speed to eliminate multiple traces 
caused by persistance of the oscilloscope screen. Fur-
ther reduction was obtained by photographing the 
oscilloscope display at 130 frames per second, and 
subsequently projecting the film at slower speeds. The 
result is clear motion pictures of the complex mo-
tions of a cross section of the bearing in operation. 
Notes: 
1. Documentation for the innovation is available 
from:
Clearinghouse for Federal Scientific 
and Technical Information 
Springfield, Virginia 22151 
Price $3.00 
Reference: TSP69- 10073 
2. Technical questions concerning this innovation 
may directed to: 
Technology Utilization Officer 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, Ohio 44135 
B69-10073 
Patent status: 
No patent action is contemplated by NASA. 
Source: Robert Y. Wong, Hugh A. Klassen, 
and Robert C. Evans 
(LEW-1071 I)
.. 
Brief 69-10073	 Category 01


Electronic visualization of gas bearing behavior

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