Long, thin-walled bellows compressed into a short length absorbs the same amount of torsional deflection as the same tube in full length condition and saves in cost, complexity and space. This bellows has lower torsional spring rate to absorb the bulk of the duct assembly tortional deflections, leaving the other bellows free to absorb axial and angular deflections

Daniels, C. M.

English

NASA Technical Reports Server

Thin Walled Bellows
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July 1966	 Brief 66-10332 
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NASA TECH BRIEF im 
NASA Tech Briefs are issued to summarize specific innovations derived from the U. S. space 
program and to encourage their commercial application. Copies are available to the public from 
the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Bellows Joint Absorbs Torsional Deflections in Duct System 
The problem: 
In flexible duct design, torsional loading (rotation 
about the duct axial centerline) is induced because of 
duct routing and induced deflections. In previous de-
signs, bellows were very rigid in torsion and were una-
ble to deflect and relieve these loads. To allow tor-
sional deflection, ducts were usually arranged in a 
dogleg configuration with a bellows joint in each half 
of the leg. Torsional loading in either half was ab-
sorbed by angular deflection of the bellows in the op-
posite half. Applications requiring a straight-in ap-
proach of the ducts and which offered short space 
length for their installation could not use conventional 
ducting designs.
The solution: 
Fabricate a long, thin walled bellows and compress 
it into a short length. In theory, a long, thin walled 
tube compressed into a short bellows can absorb the 
same amount of torsional deflection as the same tube 
in its full length condition. 
How it's done: 
A long, thin walled bellows is compressed into a 
short length and then installed in a flanged linkage 
which takes the pressure separating load and restricts 
the motion that the bellows can absorb to torsional 
deflections. The bolts holding the two flanges of the 
torsional bellows are loosely torqued to take the pres-
(continued overleaf) 
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https://ntrs.nasa.gov/search.jsp?R=19660000331 2020-03-11T17:40:18+00:00Z
sure separating load and allow relative torsional de-
flection between the two. 
The torsional bellows has a lower torsional spring 
rate than any of the other bellows in the duct assembly 
and, thus, absorbs the bulk of the duct's torsional 
deflections, leaving the other bellows of the duct as-
sembly free to take care of the axial and angular de-
flections. 
Notes: 
I. Piping and ducting designers may use this design to 
reduce duct complexity, cost, and space.
2. Inquiries concerning this innovation may be di-
rected to:
Technology Utilization Officer 
Marshall Space Flight Center 
Huntsville, Alabama 35812 
Reference: B66-10332 
Patent status: 
No patent action is contemplated by NASA. 
Source: C. M. Daniels 
of North American Aviation, Inc. 
under contract to 
Marshall Space Flight Center 
(M-FS-882) 
Brief 66-10332	 Category 05


Bellows joint absorbs torsional deflections in duct system

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