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

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-
23629-1

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-
23881-1.

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

19

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
LEW-18397-1.

<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.

20

NASA Tech Briefs, April 2010