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Full text of "NASA Technical Reports Server (NTRS) 20100012804: Foil Gas Thrust Bearings for High-Speed Turbomachinery"

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Supplying electric power to the sole- 
noids would cause the magnetostric- 
tive cylinders to push radially inward 
against a set of wedges that would be 
in axial contact with the stepped disk. 
The wedges would convert the radial 
magnetostrictive strain to a multiplied 

axial displacement of the stepped 
disk. This axial displacement would be 
just large enough to lift the stepped 
disk, against the permanent magnetic 
force, out of contact with the ring. 
The ring would then be free to turn 
because it would no longer be 

squeezed axially between the stepped 
disk and the hub. 

This work was done by Myron A. Diftler 
and Aaron Hulse of Lockheed Martin Corp. 
for Johnson Space Center. Further informa- 
tion is contained in a TSP (seepage 1 ). MSC- 

ft Low-Friction, Low-Profile, High-Moment Two-Axis Joint 

This device can be utilized in robotics, automobile steering, transmission 
systems, and aircraft control surface linkages. 

Lyndon B. Johnson Space Center, Houston, Texas 

The two-axis joint is a mechanical de- 
vice that provides two-degrees-of-free- 
dom motion between connected compo- 
nents. A compact, moment-resistant, 
two-axis joint is used to connect an 
electromechanical actuator to its driven 
structural members. Due to the require- 
ments of the overall mechanism, the 
joint has a low profile to fit within the al- 
lowable space, low friction, and high mo- 
ment-reacting capability. The mechani- 
cal arrangement of this joint can 
withstand high moments when loads are 
applied. These features allow the joint to 
be used in tight spaces where a high load 
capability is required, as well as in appli- 
cations where penetrating the mounting 
surface is not an option or where surface 
mounting is required. 

The joint consists of one base, one cle- 
vis, one cap, two needle bearings, and a 
circular shim. The base of the joint is the 
housing (the base and the cap to- 
gether) , and is connected to the ground- 
ing structure via fasteners and a bolt pat- 
tern. Captive within the housing, 
between the base and the cap, are the 
rotating clevis and the needle bearings. 

The clevis is attached to the mechanical 
system (linear actuator) via a pin. This 
pin, and the rotational movement of the 
clevis with respect to the housing, pro- 
vides two rotational degrees of freedom. 

The larger diameter flange of the cle- 
vis is sandwiched between a pair of nee- 
dle bearings, one on each side of the 
flange. During the assembly of the two- 
axis joint, the circular shims are used to 
adjust the amount of preload that is ap- 
plied to the needle bearings. The above 
arrangement enables the joint to handle 
high moments with minimal friction. 

To achieve the high-moment capability 
within a low-profile joint, the use of 
“depth of engagement” (like that of a 
conventional rotating shaft) to react mo- 
ment is replaced with planar engagement 
parallel to the mounting surface. The 
needle bearings with the clevis flange 
provide the surface area to react the cle- 
vis loads/ moments into the joint housing 
while providing minimal friction during 
rotation. The diameter of the flange and 
the bearings can be increased to react 
higher loads and still maintain a compact 
surface mounting capability. 

This type of joint can be used in a 
wide variety of mechanisms and me- 
chanical systems. It is especially effective 
where precise, smooth, continuous mo- 
tion is required. For example, the joint 
can be used at the end of a linear actua- 
tor that is required to extend and rotate 
simultaneously. The current design ap- 
plication is for use in a spacecraft dock- 
ing-system capture mechanism. Other 
applications might include industrial ro- 
botic or assembly line apparatuses, posi- 
tioning systems, or in the motion-based 
simulator industry that employs com- 
plex, multi-axis manipulators for various 
types of motions. 

This work was done by James L. Lewis of 
Johnson Space Center and Thang Le and 
Monty B. Carroll of Lockheed Martin. Fur- 
ther information is contained in a TSP (see 
page 1). 

This invention is owned by NASA, and a 
patent application has been filed. Inquiries 
concerning nonexclusive or exclusive license 
for its commercial development should be ad- 
dressed to the Patent Counsel, Johnson Space 
Center, (281) 483-1003. Refer to MSC- 

4 Foil Gas Thrust Bearings for High-Speed Turbomachinery 

John H. Glenn Research Center, Cleveland, Ohio 

A methodology has been developed 
for the design and construction of sim- 
ple foil thrust bearings intended for 
parametric performance testing and low 
marginal costs, supporting continued 
development of oil-free turbomachin- 
ery. A bearing backing plate is first ma- 
chined and surface-ground to produce 
flat and parallel faces. Partial-arc slots 
needed to retain the foil components 
are then machined into the plate by wire 

electrical discharge machining. Slot 
thicknesses achievable by a single wire 
pass are appropriate to accommodate 
the practical range of foil thicknesses, 
leaving a small clearance in this hinged 
joint to permit limited motion. The 
backing plate is constructed from a 
nickel-based superalloy (Inconel 718) to 
allow heat treatment of the entire assem- 
bled bearing, as well as to permit high- 
temperature operation. However, other 

dimensionally stable materials, such as 
precipitation-hardened stainless steel, 
can also be used for this component de- 
pending on application. 

The top and bump foil blanks are cut 
from stacks of annealed Inconel X-750 
foil by the same EDM process. The 
bump foil has several azimuthal slits sep- 
arating it into five individual bump 
strips. This configuration allows for vari- 
able bump spacing, which helps to ac- 

NASA Tech Briefs, April 2010 


commodate the effects of the varying 
surface velocity, thermal crowning, cen- 
trifugal dishing, and misalignment. Rec- 
tangular tabs on the foil blanks fit into 
the backing plate slots. 

For this application, a rather tradi- 
tional set of conventionally machined 
dies is selected, and bump foil blanks are 
pressed into the dies for forming. This 

arrangement produces a set of bump 
foil dies for foil thrust bearings that pro- 
vide for relatively inexpensive fabrica- 
tion of various bump configurations, 
and employing methods and features 
from the public domain. 

This work was done by Brian Edmonds and 
Christopher DellaCorte of Glenn Research Cen- 
ter and Brian Dykas of Case Western Reserve 

University. Further information is contained 
in a TSP (see page 1 ). 

Inquiries concerning rights for the com- 
mercial use of this invention should be ad- 
dressed to NASA Glenn Research Center, In- 
novative Partnerships Office, Attn: Steve 
Fedor, Mail Stop 4-8, 21000 Brookpark 
Road, Cleveland, Ohio 44135. Refer to 

<1 Miniature Multi-Axis Mechanism for Hand Controllers 

Lyndon B. Johnson Space Center, Houston, Texas 

A hand controller provides up to 
three axes of motion, and all required 
feel characteristics (stiffness and break- 
out torques) located inside a hollow 
handle within the grip of the hand. This 
is achieved using a miniature gimbal 
mechanism that allows for independent 
motion about one, two, or three axes 
within the grip volume of the hand, and 
miniature flexure assemblies co-located 
with the gimbal mechanism that provide 
substantial stiffness and breakout 
torques in each axis of motion. Also, 
miniature sensors can be integrated into 
the gimbal mechanism, also located 

within the grip volume of the hand, to 
provide direct angular position measure- 
ment for each axis of motion. 

Previous designs either had the pivot 
axes located outside the grip envelope, 
or used mechanical linkages to couple 
the axes of motion to remotely located 
spring mechanisms and sensors. This 
proposed design is not susceptible to vi- 
bration, shock, or g-loading in any axis, 
is of the smallest possible size and 
weight, and is highly reliable. 

This work was done by Pablo Bandera and 
Paul Buchele of Honeywell, Inc. for Johnson 
Space Center. For further information, contact 

the fSC Innovation Partnerships Office at 
(281) 483-3809. 

Title to this invention has been waived 
under the provisions of the National Aero- 
nautics and Space Act (42 U.S.C. 2457(f)/ 
to Honeywell, Inc. Inquiries concerning li- 
censes for its commercial development should 
be addressed to: 

Honeywell, Inc. 

PO. Box 52199 

Phoenix, AT 85072 

Refer to MSC-2445 7-1, volume and num- 
ber of this NASA Tech Briefs issue, and the 
page number. 


NASA Tech Briefs, April 2010