Apparatus uses prestressed cables to support vibrational table. Cables are durable, do not require frequent servicing, and provide increased safety. Because much weight rests on these cables, vibration actuating pistons can provide longer service. In event of structural failure of other supporting components, they will support entire weight of vibrational table

Kerley, J. J., Jr.

Schaller, N. C.

English

NASA Technical Reports Server

September 1973	 B73-10332 
NASA TECH BRIEF 
Goddard Space Flight 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.C. 20546. 
A Multidegree-of-Freedom Vibrational Apparatus 
The problem: 
A typical vibrational testing apparatus, commonly 
called a shaker table, consists of a vibrational table 
supported by a stationary frame. The table is usually 
connected to the frame by some elastic means such as 
coil springs, flexible steel rods, or resilient rubber 
bushings or mountings. None of these elastic materials 
is prestressed and, therefore, they deteriorate rapidly 
during vibration. Another problem with this type of 
apparatus is that the table supporting the object under 
test usually rests on pistons that impart vibration. The 
Extei 
Bt 
Port
Annular 
Stiffening 
Ring 
Base 
Frame 
Stiffening 
Web 
Securing	 Standoff Means for	 Collars Cables 
A Multidegree-Of-Freedom Vibrational Apparatus
weight of the table and of the object impose heavy stress 
on the pistons which often break down after short 
service. 
The solution: 
A new vibrational apparatus uses prestressed cables 
to support the vibrational table. These cables are much 
more durable than other elastic materials and do not 
require frequent servicing. Because much of the weight 
rests on these cables, vibration actuating pistons can 
provide longer service. 
How it's done: 
The apparatus (see figure) comprises a vibration table 
consisting of two members resting on a stationary base 
frame. The upper table member is a platform for 
supporting the object under test. This platform is resting 
on four linear hydrostatic-bearing supports attached to 
the lower table member. 
The lower table member is a metal frame structure; 
it comprises two transverse frames supported on the 
periphery by four connecting frames. Four cable as-
semblies are attached to one of the transverse frames. 
The lower table member, in turn, is suspended on these 
assemblies. The cables are attached to cylindrical stand-
off collars at four locations around the stationary base 
frame. Located under the lower table member are four 
actuating pistons which transmit vibrational forces to 
the table. These pistons are actuated by their respective 
actuating cylinders. 
The stationary base frame is a rigid metal structure 
reinforced with an annular stiffening ring and stiffening 
webs around its perimeter. 
Each cable supporting the lower table member is 
pretensioned between 10% and 50% of its breaking 
strength. Pretensioning value depends on the size of the 
cable and the weight of objects under test. In general, 
Upper 
Table	 Transverse 
Upper	 Frame	
Cable Bas 
Transverse	 Assembly 
Frame
Lower 
Connecting	 Table 
Frame
 Actuating 
Piton 
Actuating
 
Cylinder 
Hydrostat c
(continued overleaf) 
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https://ntrs.nasa.gov/search.jsp?R=19730000332 2020-03-17T07:02:54+00:00Z
heavier cables need larger pretensioning tolerances. The 
advantage of pretensioning is that it eliminates the 
compressional forces that have caused the unnecessary 
wear on elastic materials and actuating pistons. An 
additional feature of the cables is that they provide 
increased safety. In the event of structural failure of 
other supporting components, they will support the 
entire weight of the vibrational table. 
Note: 
Requests for further information may be directed to: 
Technology Utilization Officer 
Goddard Space Flight Center 
Code 207.1 
Greenbelt, Maryland 20771 
Reference: TSP73-10332
Patent status: 
This invention has been patented by NASA (U.S. 
Patent No. 3,699,807). Inquiries concerning nonexclusive 
or exclusive license for its commercial development 
should be addressed to: 
Patent Counsel 
Goddard Space Flight Center 
Code 204 
Greenbelt, Maryland 20771 
Source: James J. Kerley, Jr., and
Norman C. Schaller
Goddard Space Flight Center 
(GSC-1 1302)
. 
B73-10332	 Category 06


A multidegree-of-freedom vibrational apparatus

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