Device measures moments of inertia of an irregularly shaped mass about three mutually perpendicular axes by the standard pendulum and torque methods. A fixture suspends the test mass at one point and can be adjusted to allow oscillation of the mass

Conn, J.

English

NASA Technical Reports Server

Bar Support Plate 
June 1965
	 Brief 65-10176 
. NASA TECH BRIEF 
NASA Tech Briefs are issued by the Technology Utilization Division to summarize specific 
technical innovations derived from the space program. Copies are available to the public from 
the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia, 22151. 
Device Enables Measurement of Moments of Inertia About Three Axes 
Mountina Plate
Pendulum Axis 
€
Bearing Support Plate 
Bearing Support 
Bearing 
Test
SETUP FOR PENDULUM METHOD 
The problem: Designing a fixture which will permit 
the measurement of the moments of inertia of an ir-
regularly shaped mass about three mutually perpen-
dicular axes, without requiring remounting of the 
mass. Such a fixture was required for measuring the 
moments of inertia of delicate instrumentation pack-
ages which could be suspended from only one point. 
The solution: A fixture which suspends the test 
mass at one point and which can be adjusted to allow 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States Govern-
ment, nor NASA, nor any person acting on behalf of NASA: A. Makes 
any warranty or representation, express or implied, with respect to the 
accuracy, completeness, or usefulness of the information contained in
oscillation of the mass about each of three mutually 
perpendicular axes for measurement of the respective 
moments of inertia by the standard pendulum and 
torque methods. 
How it's done: The fixture employs a long thin 
suspension rod which is rigidly fixed to a bar support 
plate at one end and to the test mass at the other. For 
making measurements with respect to one axis by the 
pendulum method (as illustrated), the bar support 
(continucd overleaf) 
this document, or that the use of any information, apparatus, method, 
or process disclosed in this document may not infringe privately-owned 
rights; or B. Assumes any liabilities with respect to the use of, or for 
damages resulting from the use of, any information, apparatus, method, 
or process disclosed in this document.
https://ntrs.nasa.gov/search.jsp?R=19650000174 2020-03-11T17:23:15+00:00Z
plate is suspended from bearings in two bearing sup-
port plates on opposite sides of the bar support plate. 
These support plates are bolted to the mounting plate 
which is bolted to a fixed reference surface. To meas-
ure the moment of inertia about a transverse axis by 
the pendulum method, the bearing support plates are 
detached and bolted to the second pair (perpendicular 
to the first pair) of opposite edges on the bar support 
plate and the bearing support plate. Measurement of 
the moment of inertia of the mass about an axis per-
pendicular to the first two axes is accomplished by the 
torque method. For this measurement, the bearing 
support plates are removed and replaced by torsion 
plates, which are rigidly bolted to the bar support 
plate and mounting plate. With this assembly the mass 
is constrained to oscillate about the longitudinal axis 
of the suspension rod (as illustrated in the second fig-
ure). The test mass remains attached to the bottom of
the suspension rod during the moment of inertia meas-
urements about each of the mutually perpendicular 
axes. 
Notes: 
I. The fixture can be easily modified to permit meas-
urements with respect to more than three axes. 
2. Inquiries concerning this invention may be directed 
to:
Technology Utilization Officer 
Goddard Space Flight Center 
Greenbelt, Maryland, 20771 
Reference: B65-10176 
Patent status: NASA encourages the immediate 
commercial use of this invention. Inquiries about ob-
taining rights for its commercial use may be made to 
NASA, Code AGP, Washington, D.C., 20546. 
Source: Joseph Conn 
(GSFC-49) 
Brief 65-10176	 Category No. 05


Device enables measurement of moments of inertia about three axes

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