AIRCRAFT ENGINE MOUNT
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims the benefit of U.S. Provisional Patent Application
Serial No. 62/100,672, filed January 7, 2015, the disclosure of which is incorporated herein
by reference in its entirety.
BACKGROUND
[0002] Aircraft engine mounts require failsafe mounts. Typically forward and aft mounts
will secure a jet engine, also known as a turbofan, turbojet and by other terms, to a pylon or
other structural component on the aircraft. Each mount includes a plurality of securement
points with at least one additional failsafe point. The failsafe enables safe operation of the
aircraft in the event of a failure at one of the other securement points. In addition to the
primary task of safely securing the engine to the airframe, the forward and aft mounts must
be readily accessible to permit efficient installation, removal and servicing of the engine.
SUMMARY
[0003] This disclosure describes an engine mounting system comprising a forward engine
mount carrying a forward shackle assembly. The forward shackle assembly includes a coat
hanger bracket, a center bearing, a cylindrical bearing and a spherical bearing. A pin passes
through each bearing and a bolt having a head sized to pass through the bearing is positioned
within the pin. A double wrench washer tool is incorporated into the mounting system when
the forward shackle assembly is secured to a pair a clevis points.
[0004] Additionally, this disclosure describes an engine mount system suitable for
mounting a turbofan engine to a pylon attached to an aircraft wing. The mount system
includes an aft mounting reacting vertical, lateral and rear loads and a forward mount reacting
thrust, vertical and lateral loads. The system attaches to the aircraft engine at 4 points at the
forward mount and two points at the rear mount. Further, the forward and aft mounts include
an additional fail-safe attachment to the engine. The fail-safe attachment associated with
each mount only engages under select failure conditions. The Fail-safe features included at
both the aft and forward mount provide full fail-safe load paths. The system remains
statically determinant under all loading conditions in both the all components intact and
under single component failure configurations.
[0005] Further, this disclosure describes an engine mounting system that permits a known
distribution of loads under all conditions with component loads being independent of the
engine, engine mount, and pylon stiffness. The mount system provides fail-safe features for
safety. The system also accommodates installation tolerances and differential thermal
expansion between the engine and mount system components without the introduction of
internal mount system stresses.
[0006] Disclosed herein is an engine mounting system. The engine mounting system
includes a forward engine mount. The forward mount carries a forward shackle assembly.
The forward shackle assembly includes a coat hanger bracket, a center bearing positioned
within a first hole passing through said coat hanger bracket, a cylindrical bearing positioned
within a second hole passing through said coat hanger bracket and a spherical bearing within
a third hole passing through said coat hanger bracket. A first pin housing a first bolt passes
through said cylindrical bearing. A second pin housing a second bolt passes through said
spherical bearing. Each bolt has a bolt head sized to permit passage through the respective
bearing but not through the respective pin.
[0007] Also disclosed herein is an engine mounting system comprising an engine, a
forward engine mount, first and second clevis points on the engine each clevis point having a
pair of lugs and a set of nested bushings positioned within each lug of each clevis point. The
forward engine mount includes a main fitting carrying a forward shackle assembly. The
forward shackle assembly includes a coat hanger bracket, a center bearing positioned within a
first hole passing through the coat hanger bracket, a cylindrical bearing positioned within a
second hole passing through the coat hanger bracket and a spherical bearing within a third
hole passing through the coat hanger bracket. The clevis points are configured to be secured
to the cylindrical bearing and the spherical bearing carried by the coat hanger bracket. A first
pin passes through the cylindrical bearing and the nested bushings within the first clevis
point. A second pin passes through the spherical bearing and the nested bushing within the
second clevis point. A first bolt passes through the first pin. The first bolt has a threaded end
and a bolt head sized to permit passage of the bolt head through the cylindrical bearing but
not through the first pin wherein the bolt head projects outward from the first clevis point. A
first securement device is positioned on the first bolt opposite of the bolt head. A second bolt
passes through the second pin, the second bolt has a threaded end and a bolt head sized to
permit passage of the bolt head through the spherical bearing but not through the second pin
wherein the bolt head projects outward from the second clevis point. A second securement
device is positioned on the second bolt opposite of the bolt head. A wrench washer tool
positioned between the first bolt head and the nested bushing within the first clevis point and
between the second bolt head and the nested bushing within the second clevis point.
[0008] Still further, disclosed herein is a bearing assembly. The bearing assembly
includes a pair of lugs, a pair of nested bushings positioned within each lug, each nested
bushing having an inner-flanged bushing and an outer-flanged bushing, the inner-flanged
bushing extending beyond the lug, a bearing positioned between the lugs such that the
bearing is adjacent to the flanges of each nested bushing and a pin having a first end and a
second end passing through the bearing. The second end of each pin optionally carries a
flange. The flange carried by the pin engages the inner flanged bushing located within the
lug adjacent to the second end of the pin. In place of the optional flange may be a washer or
spacer having a diameter sufficient to engage the inner- and outer-flanged bushings. A bolt
positioned within the pin. The bolt has a threaded end protruding from the second end of the
pin carrying the flange and a bolt head adjacent the first end of the bolt, the bolt head sized to
preclude passage of the bolt head through the pin. A nut positioned on the threaded end of
the bolt. When a washer is substitute for the flange, the washer will be placed on the
threaded end of the bolt prior positioning the nut on the threaded end of the bolt.
Additionally, a washer is positioned between the bolt head and the pin. The washer engages
the inner-flanged bushing located within the lug adjacent the bolt head. Upon application of
torque to the bolt head and the nut, the inner-flanged bushings located within each lug are
compressed against the bearing thereby precluding application of force laterally against the
lugs.
[0009] Additionally disclosed herein is an engine mounting system comprising an aft
engine mount. The aft mount carries a first engine mounting link, a second engine mounting
link and a failsafe link. The aft mount includes a center split pylon having two halves
secured to one another. The pylon carries the first engine mounting link, the second engine
mounting link and the failsafe link. The first engine mounting link carries three bearings
positioned within the link, a first upper spherical bearing, a center oriented bearing and a
lower spherical bearing. The first upper spherical bearing secures the first engine mounting
link to the center split pylon and reacts forces in all vertical and horizontal directions. The
second engine mounting link carries three bearings positioned within the link, a first upper
spherical bearing, a center oriented bearing and a lower spherical bearing. The first upper
spherical bearing secures the first engine mounting link to the center split pylon and reacts
forces in all vertical and horizontal directions. The center oriented bearing of the first engine
mounting link reacts forces only in a direction 90 degrees to the axis of the first engine
mounting link and the center oriented bearing of the second engine mounting link reacts
forces only in a direction 90 degrees to the axis of the second engine mounting link.
[0010] Still further, the present disclosure describes an engine mounting system
comprising an aft engine mount carrying a first engine mounting link, a second engine
mounting link and a failsafe link. The aft mount includes a center split pylon having two
halves secured to one another. The pylon carries the first engine mounting link, the second
engine mounting link and the failsafe link. Additionally, the pylon has at least one hole on its
the upper surface. The hole is defined by a pair of opposing recesses in each half of the
center split pylon. Located at the lower portion of the hole is a groove. Positioned within the
hole is a shear pin. The shear pin carries a flange received within the groove located at the
lower portion of said hole.
[0011] Additionally disclosed herein is a method for staking an oriented bearing. The
method comprises the steps of machining a chamfer on a surface within a bearing mounting
opening; machining at least one divot within the chamfer; positioning a bearing race within
the bearing mounting opening; staking the bearing race within the chamfer; and, forcing the
bearing race to conform with the divot within the chamfer.
[0012] Also disclosed herein is a wrench washer tool. The wrench washer tool is
particularly suited for torqueing operations where bolt heads are blocked by additional
components. The wrench washer tool comprises a first end and a second end. The first end
has a first slot defined by parallel side walls. The first slot also carries flanges projecting
inwardly from the parallel side walls. The second end of the wrench washer tool has a
second slot defined by parallel side walls. The second slot also carries flanges projecting
inwardly from the parallel side walls of the second slot. Additionally, the wrench washer tool
carries torque application point projecting outwardly from the tool.
[0013] Further, disclosed herein is a bearing configured to react forces in a single plane.
The bearing comprises a bearing race, two opposing bearing race interfaces and a cylindrical
bearing inner member positioned within the bearing race. The cylindrical bearing inner
member has two curved exterior walls and two parallel exterior walls. The curved exterior
walls engage the bearing race interfaces and the parallel exterior walls define a gap between
the cylindrical bearing inner member and the bearing race on each side of the cylindrical
bearing inner member.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 depicts a side view of a turbine engine secured to a pylon by forward and
aft mounts.
[0015] FIG. 2A is a top view of a forward engine mount for a turbine engine.
[0016] FIG. 2B is a front view of a forward engine mount for a turbine engine.
[0017] FIG. 2C is a top side perspective view of a forward engine mount for a turbine
engine
[0018] FIG. 2D is a side view of a forward engine mount for a turbine engine.
[0019] FIG. 2E is a bottom side perspective view of a forward engine mount for a turbine
engine
[0020] FIG. 2F is an exploded assembly view of a forward engine mount for a turbine
engine
[0021] FIG. 2G is an exploded assembly view of an aft engine mount for a turbine
engine
[0022] FIG. 2H is an exploded assembly view of the main fitting, the forward shackle and
the Whipple tree shackle of the forward engine mount for a turbine engine.
[0023] FIG. 3 is a side view of a forward engine mount for a turbine engine depicting the
interface attachment points between the forward engine mount and the turbine engine.
[0024] FIG. 4A is sectional view of a shackle assembly taken along lines A-A of FIG.
4B.
[0025] FIG. 4B is a perspective view of a forward engine mount for a turbine engine with
the front shackle secured to a turbine engine.
[0026] FIG. 5 is an enlarged perspective view of a shackle interface on airplane left with
clevis points on the engine.
[0027] FIG. 6A is a sectional view of a shackle on the airplane right of the engine.
[0028] FIG. 6B is an enlarged perspective view of a shackle interface on airplane right
with clevis points on the engine.
[0029] FIG. 7A is a front view of the forward shackle assembly of the front engine
mount.
[0030] FIG. 7B is a top view of the forward shackle assembly as identified in FIG. 3.
[0031] FIG. 7C is a perspective of the forward shackle assembly.
[0032] FIG. 7D is a cross sectional view of the forward shackle assembly taken along
line.
[0033] FIGS. 7F, 7G, 7H, 7J and 7K depict the components of the cylindrical bearing
found on airplane right of the forward shackle depicted in FIG. 7A.
[0034] FIG. 8 depicts the wrench washer tool.
[0035] FIG. 9 depicts the forward housing of the engine with the interface attachment
points associated with the forward mount.
[0036] FIG. 10 depicts the improved staking configuration for the cylindrical bearing.
[0037] FIG. 11 depicts the detail of area 12 depicted in FIG. 11.
[0038] FIG. 12 depicts the detail of the race staked into the chamfer.
[0039] FIGS. 13-15 depict various load failure points by an -X- and the reacted loads
following failure of the indicated fastener or component.
DETAILED DESCRIPTION
[0040] As used herein, the terms "left' and 'right' refer to airplane left and right.
[0041] This disclosure describes an improved fail-safe engine mounting system 10
suitable for securing turbine engines to aircraft. As depicted in FIG. 1, system 10 includes a
forward engine mount 20 and an aft engine mount 30 for securing a turbine engine 12 to a
pylon 5 or other aircraft structure. The securement of engine 12 to pylon 5 via forward
mount 20 and aft mount 30 is accomplished using multiple bolts 8 and shear pins 44.
Additionally, this disclosure provides an improved bearing staking process suitable for
retaining bearing races within any application that requires bearings positioned in a
predetermined configuration and substantially precluding rotation of the bearing races.
[0042] Engine 12 includes the necessary securement points for attachment of engine to
engine mounting system 10. The forward portion of engine 12 includes forward mount front
clevis mounting points 13a and 13b, right and left respectively and forward mount fail safe
clevis mounting point 13c. The forward portion of engine 12 also includes two forward but
lower clevis points 14a and 14b. Lower right clevis point 14a and lower left clevis point 14b
are slightly to the aft of engine forward fail-safe clevis mounting point 13c. As depicted in
FIG. 4A, each clevis mounting point 13a, 13b includes a pair of lugs 15 with each lug having
a passageway 15a therethrough suitable for receiving bushings 60.
[0043] The forward engine mount 20 will be described with reference to FIGS. 2A-2F,
2H, and 3-10. The forward engine mount 20 includes a main fitting 40, a forward shackle
assembly 50, a Whipple tree assembly 80 with two thrust links 87 carried by the Whipple tree
80. Main fitting 40 is a two-piece assembly split along the vertical thrust plane. Bolts 42
passing through main fitting right 40a and main fitting left 40b and retained by securing
devices (not shown) secure each half to the other. Prior to assembly, two or more shear pins
44 having a lower lip or flange 44a are positioned within recesses 45 in each half 40a, 40b
and are retained therein upon completion of assembly of main fitting right 40a to main fitting
left 40b to one another. Each recess 45 having a groove 45a which cooperates with flange
44a of pin 44 to retain shear pin 44 within main fitting 40 after assembly thereof. Following
assembly of main fitting right half 40a and main fitting left half 40b, recesses 45 define holes
45 along the centerline of main fitting 40. Thus, shear pins 44 are retained within holes 45 of
main fitting 40 on the thrust line of forward engine mount 20.
[0044] Positioning of shear pins 44 along the centerline of main fitting 40 ensures
application of thrust along the centerline 40c of mount 20 to pylon 5 without inducing any
lateral moment. As assembled, one shear pin 44 is a tight fit having about 0.002 inches
(about 0.051 millimeters) clearance between pin 44 and main fitting 40 and a second shear
pin 44 has a slight clearance fit of about 0.01 inches (about 0.25 millimeters) clearance
between pin 44 and main fitting 40. Thus, the second shear pin acts as a fail-safe.
[0045] In the assembled configuration, main fitting 40 has a forward projecting boss 46
and a rearward and downward projecting boss 47. Each boss will typically have a tapered
decreasing diameter from the main fitting to the end of the boss; however, each boss may
have a constant diameter cylinder configuration or any other convenient configuration.
Additionally, each boss will have at least two threaded holes 48 with at least one hole 48 in
each half of main fitting 40a and 40b. Further, in the assembled configuration, main fitting
40 has a fail-safe lug 49 position on the lower portion of main fitting 40.
[0046] The forward shackle assembly 50 includes a coat hanger bracket 51, a center
bearing 52, a cylindrical bearing 53 and a spherical bearing 54. Positioned within cylindrical
bearing 53 is a pin 58 with a bolt 6 1 installed within pin 58. Bolt head 61a is sized to
preclude passage through pin 58; however, bolt head 61a and pin 58 together will pass
through cylindrical bearing 53. Positioned within spherical bearing 54 is a pin 57 with a bolt
6 1 passing through pin 57. Bolt head 61a is sized to preclude passage through pin 57;
however, bolt head 61a and pin 57 together will pass through spherical bearing 54. As
discussed in more detail below, during assembly bolt 6 1 will be positioned within pin 57 or
58 and a castellated nut 62 secured to bolt 61. Bolt 6 1 and pin 57 or 58 will pass through the
respective bearing 53 or 54. Wrench washer 70 will be positioned such that flanges 73 are
located between bolt head 61a and pin 57 or 58. Thus, flanges 73 act as a retaining washer.
Although described herein as pin 57 and pin 58, the same pin may be used with both bearing
assemblies.
[0047] Coat hanger bracket 5 1 may be a single piece of metal, e.g. steel. However, to
provide for the multiple redundancies required by the aviation industry, coat hanger bracket
5 1 typically includes at least two separate elements 51a and 51b split substantially along the
mid-plane of coat hanger bracket 51. Typically, elements 51a and 51b are machined from
stainless steel appropriate for the environment of use such as but not limited to 15-5PH
stainless. Other suitable classes of metals appropriate for use would include: titanium alloys
or high strength nickel alloys such as Inconel 718 and other alloys having the strength
necessary for the targeted environment. In general, as is known to those skilled in the art,
bearing size, steel hardness and other similar characteristics will be determined according to
common engineering practices as dictated by the environment or field of use for the
component.
[0048] With reference to FIG. 7A, forward shackle assembly 50 includes coat hanger
bracket 5 1 and bearings mounted within coat hanger bracket assembly 51. Centrally located
within coat hanger bracket 5 1 is a center bearing 52. Center bearing 52 is sized to be fitted
over the main fitting forward projecting boss 46. A retention plate positioned over center
bearing 52 and secured to forward projecting boss 46 by bolts 56 provides secondary
retention of forward shackle assembly 50 to main fitting 40. Bolts 56 pass through holes 55a
in retention plate 55 and engage threaded holes 48 in forward projecting boss 46.
[0049] As further depicted in FIG. 7A, cylindrical bearing 53 is positioned to aircraft
right of center bearing 52 and spherical bearing 54 is positioned to aircraft left of center
bearing 52. However, the side-to-side orientation of cylindrical bearing 53 and spherical
bearing 54 may be reversed and still provide the same functionality. Regardless of the sideto-
side orientation of the two bearings, forward shackle assembly 50 provides a statically
determinant system between forward engine mount 20 and engine forward mount front clevis
mounting points 13a, 13b.
[0050] Spherical bearing 54 reacts load in both the vertical and lateral direction. Use of a
spherical bearing on each side of center bearing 33 could lead to undue stress on coat hanger
bracket 5 1 and result in load distribution dependent upon the stiffness of the engine 12. With
reference to FIG. 5A, to avoid rattle and reduce wear, pin 57 passing through spherical
bearing 54 must have a tight fit within spherical bearing 54 and engine forward mount front
clevis mounting point 13b. In this application, a tight fight is generally between about 0.0
inches to about 0.002 inches. Thus, use of two spherical bearings will not accommodate
thermal expansion between engine forward mount front clevis mounting points 13a, 13b and
forward shackle assembly 50. As a result, use of two spherical bearings in forward shackle
assembly 50 will not provide a statically determinant system.
[0051] However, use of cylindrical bearing 53 at one mounting point of forward shackle
assembly 50 provides a loading point that reacts loads only in the vertical direction while
permitting angular deflection at engine forward mount front clevis mounting point 13a.
Thus, this configuration provides sufficient lateral clearance to accommodate tolerances. The
combination of spherical bearing 54 and cylindrical bearing 53 provide a statically
determinant system.
[0052] To ensure the desired loading of cylindrical bearing 53 in the vertical direction,
the cylindrical bearing race 53a of cylindrical bearing 53 must be staked-in forward shackle
assembly 50 such that cylindrical bearing inner member 53b when installed within cylindrical
bearing race 53a has lateral clearance but no vertical clearance. As previously noted, the
degree of clearance will depend upon the application. As depicted in FIG. 7A, the minimum
lateral clearance between cylindrical bearing inner member 53b and race 53a is about 0.026
inches (about 0.66 millimeters) on each side or total lateral clearance of 0.52 inches (about
13.21 millimeters). The lateral clearance provided by cylindrical bearing 53 permits sliding
of cylindrical bearing inner member 53b within cylindrical bearing race 53a. The clearance
provided allows the mounting system to accommodate installation tolerances, thermal growth
and deflections under normal operating conditions.
[0053] Under normal operating conditions, total forces experienced at forward shackle
assembly 50 may be determined with reference to spherical bearing 54. However, in the
event of a failure of spherical bearing 54, the clearances defined above will close due to the
added load carried by cylindrical bearing 53 resulting in cylindrical bearing 53 reacting both
lateral and vertical loads. Thus, after failure of spherical bearing 53, at least one gap between
the parallel exterior walls of cylindrical bearing inner member 53b and race 53a closes. As
illustrated in FIG. 15, the pin and bolt within fail-safe lug 49 will also engage fail-safe clevis
mounting point 13c to only react vertical loads. Likewise, as depicted in FIG. 13, failure of
cylindrical bearing 53 will transfer all load to spherical bearing 54. Thus, shackle assembly
ensures a statically determinant system between engine forward mount front clevis mounting
points 13a, 13b under normal operating conditions as well as under failure of either bearing
53, 54. FIG. 14 depicts the failure of one-half 51a or 51b of coat hanger bracket 51. In this
failure mode, the surviving portion of coat hanger bracket 51 continues to react forces in the
same manner as prior to the failure. Thus, cylindrical bearing 53 does not experience any
changes in load. FIG. 15 depicts the failure of cylindrical bearing 53. Under this failure
condition, spherical bearing will react all forces of thrust and vertical loads. Additionally,
fail-safe lug 49 will engage to only react vertical loads.
[0054] FIGS. 7F-7H and 7J-7K provide further details of cylindrical bearing 53. As
depicted therein, cylindrical bearing 53 includes a cylindrical bearing inner member 53b with
flat ends and a bearing race 53a. Bearing race 53a has two opposing interfaces 53c.
Cylindrical bearing inner member 53b has two curved exterior walls defining bearing
interfaces 53c and two parallel exterior walls. When installed within bearing race 53a,
bearing interfaces 53c of cylindrical bearing inner member 53b contact bearing interfaces 53c
of bearing race 53a. In normal operations, interfaces 53c of bearing race 53a and cylindrical
bearing inner member 53b provide the only load contact points between bearing race 53a and
cylindrical bearing inner member 53b. Thus, in this configuration cylindrical bearing inner
member 53b slides within bearing race 53a in the unloaded direction. Additionally, with
cylindrical bearing inner member 53b installed within race 53a, parallel walls of cylindrical
bearing inner member 53b define a gap between cylindrical bearing inner member 53b and
race 53a on each side of cylindrical bearing inner member 53b. Cylindrical bearing inner
member 53b is installed by rotating 90° about the cylinder axis relative to the operation
position and cylindrical bearing inner member 53b into outer cylindrical bearing race 53a.
Rotating cylindrical bearing inner member 53b back to the operational position captures
cylindrical bearing inner member 53b in cylindrical bearing race 53a, i.e. cylindrical bearing
inner member 53b engages cylindrical inner interface 53c. Outer cylindrical bearing race 53a
may optionally include a liner or cylindrical bearing 53 may have metal-to-metal contact
between cylinder 53a and outer cylindrical bearing race 53a.
[0055] As discussed above, forward shackle assembly 50 engages engine forward mount
front clevis mounting points 13a and 13b. Paired shouldered or flanged bushings 60 are
positioned within each clevis passageway 15 of each clevis point 13a, 13b. As depicted in
FIGS. 4A, 4B and FIG. 8, pair flanged bushing 60 is a nested arrangement of an innerflanged
bushing 60a and an outer-flanged bushing 60b. Outer-flanged bushing 60b is press
fit within passageway 15a and inner-flanged bushing 60a slid into outer-flanged bushing 60b.
This configuration of bushings cooperates with pins 57 or 58, bolt 6 1 and a double wrench
washer tool 70, depicted in FIG. 8, to permit securement of forward shackle assembly 50 to
forward mount front clevis mounting points 13a, 13b without the need to specify selective
assembly of components, i.e. use of stacked washers. Outer-flanged bushing 60b material
may be 304 annealed CRES, 15-5PH, 17-4PH, HI 150 with optionally 100% of all surfaces
lubed. Inner-flanged bushing 60a should or could be 15-5PH, 17-4PH, condition H1025 or
INCO 718. Typically, the inside diameter and end face of inner-flanged bushing 60a will be
lubed at points where it contacts the ball of the bearing. Preferred lubes are moly based or
graphite based. Alternatively, outer-flanged bushing 60b may be a bronze material such as
Aluminum bronzes, copper beryllium (AMS454 type) or Copper-tin-nickel spinodal bronze
(AMS4596 type). When using a bronze material for outer-flanged bushing 60b, innerflanged
bushing 60a will typically be formed from a steel alloy such as 15-5PH. The bronzebased
bushing configuration would not require a lubricant.
[0056] FIGS. 4A and 6A depict the configuration and relationship of main fitting left 40b
of forward shackle assembly 50 positioned within lugs 15 of engine forward mount front
clevis mounting point 13b. After positioning of coat hanger bracket 5 1 in alignment with
engine forward mount front clevis mounting points 13a and 13b, pin 58 and bolt 6 1 are
positioned within the assembly by passing from the rear of coat hanger bracket 5 1 through
spherical bearing 54 within coat hanger bracket 5 1 and through clevis mounting point 13b.
Likewise, pin 57 and bolt 6 1 are positioned within the assembly passing from the rear of coat
hanger bracket 5 1 through cylindrical bearing 53 and clevis mounting point 13a. Washers or
spacers 75, as needed, are placed on bolts 6 1 prior to securing a castellated nut or other
locking mechanism on bolts 61. As depicted, the head 61a of each bolt 6 1 is sized to pass
through the opening of spherical ball 54a and cylindrical bearing inner member 53b. Further
as depicted in FIGS. 4A, 5A and 6A, bolt 6 1 has a length such that double wrench washer
tool 70 may be positioned between pins 57 and 58 and each bolt head 61a with castellated nut
62 or other locking mechanism secured to each bolt 6 1 in the assembled but pre-torqued
configuration.
[0057] Double wrench washer tool 70 provides multiple functions within the
configuration of fail-safe engine mounting system 10. As depicted in FIG. 8, double wrench
washer tool 70 has two slots 71 positioned a distance apart. The distance between slots being
equal to the centerline of the clevis mounting point passageways 15a in lugs 15. Each slot
having a distance such that the parallel walls 71a and 71b of the slots serve as wrench flats
72. Additionally, parallel walls 71a and 71b carry inwardly projecting flanges 73. Flanges
73 are separated by a distance approximately equal to the diameter of bolts 61. Thus, when
positioned between bolt heads 61a and pins 57, 58, double wrench washer tool 70 acts both as
a wrench with wrench flats 72 engaging bolt heads 61a to preclude rotation thereof during
torqueing operations and flanges 73 acting as retaining washers to engage and capture bolt
heads 61a. Thus, double wrench washer tool secures and precludes loss of pins 57, 58
thereby precluding pins 57, 58 passing through the bearings. Double wrench washer tool 70
additionally carries a torque application point 74 suitable for engagement by any
conventional torque application tool. As depicted in FIG. 8, the torque application point is an
upwardly projecting ear 74 with an opening suitable for receiving a drive mechanism. Ear 74
is not limited to an upward projection; rather, torque application point 72 needs to provide
sufficient clearance beyond the confines of the equipment being assembled to permit
engagement by any conventional torque application tool.
[0058] Thus as described above, positioning of forward shackle assembly 50 with coat
hanger bracket 5 1 aligned with engine forward mount front clevis mounting points 13a, 13b
places cylindrical bearing assembly 52 and spherical bearing assembly 54 in alignment with
openings 15a of clevis mounting point lugs 15. Final securement of coat hanger bracket 5 1 to
clevis mounting points 13a, 13b entails positioning of bolts 6 1 through pins 57 and 58 and
castellated nuts 62 on bolts 6 1 followed by securing bolt heads 61a with double wrench
washer tool 70. The wrench flats 72 of double wrench washer tool 70 are positioned such
that wrench flats 72 and flanges 73 engage bolt heads 61a of each bolt 61. With double
wrench washer tool 70 positioned between bolt heads 61a and pins 57, 58, each bolt 6 1 can
be turned until each head 61a aligns with wrench flats 72. Once each bolt head 61a engages
wrench flats 72 of double wrench washer tool 70, then each associated castellated nut 62 or
other locking mechanism can be tightened to secure forward shackle assembly 50 to engine
forward mount front clevis mounting point 13a, 13b.
[0059] Although described herein as a castellated nut 62 and cotter pin (not shown)
arrangement, the device opposite of bolt head 61a may be any suitable nut or securement
component having at least one secure locking mechanism. In some applications, the
securement component will have at least two secure locking mechanisms, e.g. a locking
compound and at least one physical locking component. Thus, upon final assembly, double
wrench washer tool 70 remains as an integral component of the joint between engine 12 and
forward shackle assembly 50.
[0060] FIG. 4A depicts a sectional view of the forward shackle assembly 50 positioned
within clevis mounting lugs 15 taken along lines A-A of FIG. 4B. Thus FIG. 4A depicts a
spherical bearing. However, the relationship of the bearings 53 and 54 and nested bushings
60 with forward shackle assembly 50 positioned within a clevis point 13a or 13b will be the
same. FIG. 4A depicts the relationship of engine forward mount front clevis mounting points
13a, 13b , pins 57 or 58, bolt 61, spacer 75, castellated nut 62, outer-flanged bushing 60b, i.e.
the press fit bushing, inner-flanged bushing 60a and double wrench washer tool 70. As
depicted in FIG. 4A, pins 57 and 58 have a flange 57a, 58a, respectively, positioned at the
end of the pin adjacent to the threaded end of bolt 61. Flange 58a may be omitted and
replaced by a large washer or spacer 75 having a diameter sufficient to engage inner- and
outer- flanged bushings 61a, 61b. Normally, spherical ball 54a or cylindrical bearing inner
member 53b would be positioned between the shoulders of inner bushings 60a. As discussed
above, forward shackle bearings 53, 54 are positioned within engine forward mount front
clevis mounting points 13a, 13b. During securement of forward shackle assembly to engine
forward mount front clevis mounting points 13a, 13b, bolt head 61a and pin flange 58a force
inner-flanged bushing 60a into engagement with spherical ball 10 of spherical bearing 54 or
in the case of the cylindrical bearing 53 into engagement with the cylindrical bearing inner
member 53b. Thus, all relative movement takes place between inner- and outer-flanged
bushings 60a and 60b. By forcing all motion between the inner- and outer-flanged bushings
60a and 60b all potential damage to the pins 57, 58 in a failure mode is avoided. Further, the
nested bushing arrangement precludes bending of the engine clevis lug 15 during installation,
removal and/or servicing. Thus, the torqueing operation does not place stress on clevis
mounting point lugs 15. The double bushing arrangement may be used with any clevis point
and bearing assembly without the need for wrench washer 70. If the assembly of a shackle or
other bearing mount to a clevis point is not obstructed by other components, a washer or
spacer 75 having a diameter sufficient to engage both inner- and out-flanged bushings 60a,
60b may be substituted for wrench washer 70. Washer or spacer 75 will be placed between
bolt head 61a and nested bushing 60. As discussed above, this configuration of nested
bushings 60 and spacers or washers 75 will not place stress on clevis mounting point lugs 15
during torqueing of nut 62 and bolt 61.
[0061] Thus, as depicted in the FIGS. 3, 5 and 6B, double wrench washer tool 70 and
castellated nut 62 retain forward shackle assembly 50 within engine forward mount front
clevis mounting points 13a, 13b thereby securing forward shackle assembly engine 12.
Although described herein as a single component, double wrench washer tool 70 may also be
provided as separate individual wrench washers with each having a suitable torque
application point.
[0062] To complete the assembly of forward engine mount 20 to engine 12, main fitting
fail-safe lug 49 is secured to engine fails-safe clevis 13c. This mounting point does not
experience direct engagement unless both bearings in coat hanger bracket 5 1 fail.
Additionally, the thrust links 85 carried by Whipple tree support 80 must be secured to engine
forward lower clevis points 14a and 14b.
[0063] With reference to FIGS. 2E and 2H, Whipple tree support 80 includes three
openings, a central opening 8 1 and left and right openings 82, 83. Central opening 8 1 is sized
to receive a bearing 84 with bearing 84 configured as an interference fit over rearward and
downward projecting boss 47. A cap 85 having a diameter greater than opening 8 1 is
positioned over opening 8 1 with Whipple tree 80 positioned on bearing 84, bolts 86 passing
through cap 85 and into boss 47 secures Whipple tree 80 to boss 47. As depicted in FIG. 2F,
each thrust link 87 is secured to Whipple tree 80 by a clamped pin joint arrangement where a
pin 88 having an external diameter sized to fit within thrust link opening 87a passes through
Whipple tree opening 82 or 83. A bolt passes through the pin 88 and a nut 90 with an
optional washer or other conventional mechanism for retaining bolt 89 within pin 88 secures
thrust link 87 to Whipple tree 80. Typically, nut 90 for retaining bolt 90 will be a self-locking
nut or a castellated nut with cotter pin. Each forward end of thrust links 80 with thrust link
opening 87b is positioned within the respective engine forward lower clevis point 14a, 14b.
Typically, for lower clevis points 14a and 14b, each clevis point lug 15 will have a bushing
15b positioned within the clevis mounting point passageway 15a. Each forward end of thrust
link 80 contains a spherical bearing similar to spherical bearing 54. A pin 88 passes through
bushing 15b and spherical bearing 54 with a bolt passing through pin 88 and is retained by a
nut 90. Nut 90 may be a self-locking or a castellated nut with cotter pin.
[0064] As discussed above, cylindrical bearing 53 as included within coat hanger bracket
5 1 provides a statically determinant system. To provide this system, cylindrical bearing 53
must be arranged such that it carries load only in the vertical direction. Accordingly, rotation
of bearing within forward shackle assembly 50 during assembly of forward shackle assembly
50 forward mount front clevis mounting points 13a and 13b must be avoided. To preclude
rotation of cylindrical bearing 53 within forward shackle assembly 50, cylindrical bearing
race 53a is staked within forward shackle assembly 50. With reference to FIGS. 10-12, the
staking process includes the steps of forming a staking groove 92 within cylindrical bearing
race 53a and machining a matching chamfer 93 within the opening 94 of forward shackle
assembly 50. Following machining of chamfer 93, one or more spherical ball end mill
"divots" 95 are machined into chamfer 93. After positioning of cylindrical bearing race 53a
in opening 94 and conventionally staking cylindrical bearing race 53a, a second staking step
is used. In the second staking step, a ball nosed "punch" or other appropriate staking tool is
placed over the race at the location of each divot 95 and hammered with sufficient force to
drive race material into each divot 95. Thus, the second staking step forces the staked bearing
to additionally conform with divot 95 previously machined into chamfer 93. The additional
staking step increase the torque restraint value of the staked-in bearing by two to three times
the torque restraint value of the conventionally staked-in bearing. For a bearing race located
within a two-inch hole, the torque restraint value will increase from about 500 inch-lbf (about
56.6 Newton-meters) for conventional staking to at least 1000 inch-lbf (about 113 Newtonmeters)
and typically will increase to 1500 inch-lbf (about 169.5 Newton-meters) depending
on the metal used for the race of the staked-in bearing.
[0065] FIG. 2G depicts an aft mount 30. Aft mount 30 includes a pylon fitting 3 1 made
up by pylon halves 31a and 31b. Joinder of halves 31a and 31b by bolts 32 and pins 33
captures and retains three links 34, 35 and 36. Links 34 and 35 attach to pylon fitting 3 1 with
spherical bearings 54 and to rear engine clevis points 16 with spherical bearings 54. As
described above, a bolt 6 1 and nut 62 will retain links 34 and 35 at each mounting point. Link
36 is also joined to pylon fitting 3 1 by staked oriented bearings 38 positioned within openings
37. Staked oriented bearings 38 do not carry load along the axis of links 34, 35. Rather,
bearings 38 only carry load perpendicular to the axis running along the length of links 34 and
35. The staking operation for oriented bearings 38 include the use of a chamfer and divot as
described above with regard to oriented cylindrical bearing 53 of forward mount 20.
Additionally, aft mount 30 includes at least two shear pins 44 with each shear pin 44 having a
lower lip or flange 44a. Each shear pin is sandwiched between halves 31a and 31b of pylon
fitting 31. Thus, shear pins 44 are located on the centerline of aft mount 30. Location of
shear pins 44 on the centerline of aft mount 30 ensures lateral loads are carried without
inducing moments in that direction. As assembled one shear pin 44 is a tight fit, about 0.002
inches (about 0.051 millimeters) clearance between pin 44 and pylon 3 1 and a second shear
pin 44 is a slight clearance fit, about 0.01 inches (about 0.25 millimeters) clearance between
pin 44 and pylon 31. Thus, the second shear pin acts as a fail-safe.
[0066] Other embodiments of the present invention will be apparent to one skilled in the
art. As such, the foregoing description merely enables and describes the general uses and
methods of the present invention. Accordingly, the following claims define the true scope of
the present invention.

CLAIMS
What is claimed is:
1. An engine mounting system comprising:
a forward engine mount carrying a forward shackle assembly, said forward shackle
assembly comprises a coat hanger bracket, a center bearing positioned within a first hole
passing through said coat hanger bracket, a cylindrical bearing positioned within a second
hole passing through said coat hanger bracket and a spherical bearing within a third hole
passing through said coat hanger bracket;
a first pin passing through said cylindrical bearing;
a second pin passing through said spherical bearing;
a first bolt passing through said first pin, said first bolt having a threaded end, said
first bolt having a bolt head sized to permit passage of the bolt head through said cylindrical
bearing;
a second bolt passing through said second pin, said second bolt having a threaded end,
said second bolt having a bolt head sized to permit passage of the bolt head through said
spherical bearing.
2. The engine mounting system of claim 1, wherein said forward shackle assembly
provides a statically determinant system.
3. The engine mounting system of claim 1, wherein said cylindrical bearing carries load
only in the vertical direction.
4. The engine mounting system of claim 3, further comprising:
a chamfer around the circumference of said second hole and at least one divot within
the area defined by said chamfer;
said cylindrical bearing having a race, said race having upper and lower interfaces and
said race retained within said second hole by a staking operation between said race and said
chamfer;
a portion of said race further deformed into the area defined by said divot, thereby
securing said race within said hole; and,
a cylindrical bearing cylinder positioned within said race, said cylindrical bearing
having upper and lower interfaces and right and left walls, said cylindrical bearing cylinder
engaging only said race upper and lower interfaces and defining a gap between the right and
left walls of said cylindrical bearing cylinder and said race.
5. The engine mounting system of claim 1, wherein said forward engine mount further
comprises:
a split main fitting, said split main fitting carrying a forward projecting boss and a
rearward and downward projecting boss, said forward projecting boss and rearward and
downward projecting boss defining the length of said main fitting, said main fitting split into
two halves along the centerline of said length of said main fitting, said forward projecting
boss carrying said forward shackle assembly;
said main fitting halves secured to one another,
said main fitting having at least one hole positioned on the centerline of said main
fitting;
a shear pin retained within said hole on the centerline of said main fitting.
6. The engine mounting system of claim 5, wherein said main fitting has at least two
holes positioned on the centerline of said main fitting, a first shear pin retained within a first
hole and a second shear pin retained within a second hole, wherein the first shear pin reacts
force and the second shear pin reacts force only in the event of the failure of the first shear
pin.
7. An engine mounting system comprising:
an engine,
a forward engine mount comprising a main fitting, said main fitting carrying a
forward shackle assembly, said forward shackle assembly comprises a coat hanger bracket, a
center bearing positioned within a first hole passing through said coat hanger bracket, a
cylindrical bearing positioned within a second hole passing through said coat hanger bracket
and a spherical bearing within a third hole passing through said coat hanger bracket;
first and second clevis points on said engine each clevis point having a pair of lugs,
said clevis points configured to be secured to said cylindrical bearing and said spherical
bearing carried by said coat hanger bracket;
a set of nested bushings positioned within each lug of each clevis point;
a first pin passing through said cylindrical bearing and said nested bushings within
said first clevis point;
a second pin passing through said spherical bearing and said nested bushing within
said second clevis point;
a first bolt passing through said first pin, said first bolt having a threaded end, said
first bolt having a bolt head sized to permit passage of the bolt head through said cylindrical
bearing but not through said first pin wherein said bolt head projects outward from said first
clevis point;
a first securement device positioned on said first bolt opposite of said bolt head;
a second bolt passing through said second pin, said second bolt having a threaded end,
said second bolt having a bolt head sized to permit passage of the bolt head through said
spherical bearing but not through said second pin wherein said bolt head projects outward
from said second clevis point;
a second securement device positioned on said second bolt opposite of said bolt head;
a wrench washer tool positioned between said first bolt head and said nested bushing
within said first clevis point and between said second bolt head and said nested bushing
within said second clevis point.
8. The engine mounting system of claim 7, further comprising:
a failsafe lug carried by said main fitting;
a third clevis point carried by said engine;
said failsafe lug aligns with said third clevis point; and,
a third pin with a third bolt positioned within said pin, said pin passing through said
failsafe lug and said third clevis point.
9. The engine mounting system of claim 8, wherein said system provides a statically
determinant system.
10. The engine mounting system of claim 8, wherein said coat hanger bracket is
comprises two halves with the first half being a front element and the second half being a
back element, wherein each half houses said center bearing, said spherical bearing and said
cylindrical bearing.
11. The engine mounting system of claim 10, wherein upon failure of any one of said
spherical bearing, said cylindrical bearing, said front element or said back element, said
engine mounting system provides a statically determinant system.
12. A bearing assembly comprising:
a pair of lugs;
a pair of nested bushings positioned within each lug, each nested bushing having an
inner flanged bushing and an outer flanged bushing, said inner flanged bushing extending
beyond said lug;
a bearing positioned between said lugs such that said bearing is adjacent to the flanges
of each nested bushing;
a pin passing through said bearing, said pin having a first end and a second end,
a flange carried by said second end of said pin, said flange carried by said pin
engaging said inner flanged bushing located within the lug adjacent to said second end of said
pin;
a bolt positioned within said pin, said bolt having a threaded end protruding from the
second end of the pin carrying said flange and a bolt head adjacent said first end of said bolt,
said bolt head sized to preclude passage of said bolt head through said pin;
a nut positioned on said threaded end of said bolt; and,
a washer positioned between said bolt head and said pin, said washer engaging said
inner flanged bushing located within said lug adjacent said bolt head, wherein upon
application of torque to said bolt head and said nut, said inner flanged bushings located
within each lug are compressed against said bearing thereby precluding application of force
laterally against said lugs.
13. A bearing assembly comprising:
a pair of lugs;
a pair of nested bushings positioned within each lug, each nested bushing having an
inner flanged bushing and an outer flanged bushing, said inner flanged bushing extending
beyond said lug;
a bearing positioned between said lugs such that said bearing is adjacent to the flanges
of each nested bushing;
a pin passing through said bearing, said pin having a first end and a second end,
a bolt positioned within said pin, said bolt having a threaded end protruding from the
second end of the pin carrying said flange and a bolt head adjacent said first end of said bolt,
said bolt head sized to preclude passage of said bolt head through said pin;
a nut positioned on said threaded end of said bolt;
a first washer positioned between said nut and said pin, said first washer engaging
said inner flanged bushing located within said lug adjacent said nut; and,
a second washer positioned between said bolt head and said pin, said second washer
engaging said inner flanged bushing located within said lug adjacent said bolt head, wherein
upon application of torque to said bolt head and said nut, said inner flanged bushings located
within each lug are compressed against said bearing thereby precluding application of force
laterally against said lugs.
14. An engine mounting system comprising:
an aft engine mount carrying a first engine mounting link, a second engine mounting
link and a failsafe link;
a center split pylon having two halves secured to one another, said pylon carrying said
first engine mounting link, said second engine mounting link and said failsafe link;
said first engine mounting link carries three bearings positioned within said link, a
first upper spherical bearing, a center oriented bearing and a lower spherical bearing, said
first upper spherical bearing secures said first engine mounting link to said center split pylon,
said first upper spherical bearing reacts forces in all vertical and horizontal directions;
said second engine mounting link carries three bearings positioned within said link, a
first upper spherical bearing, a center oriented bearing and a lower spherical bearing, said
first upper spherical bearing secures said first engine mounting link to said center split pylon,
said first upper spherical bearing reacts forces in all vertical and horizontal directions;
said center oriented bearing of said first engine mounting link reacts forces only in a
direction 90 degrees to the axis of said first engine mounting link; and,
said center oriented bearing of said second engine mounting link reacts forces only in
a direction 90 degrees to the axis of said second engine mounting link.
15. An engine mounting system comprising:
an aft engine mount carrying a first engine mounting link, a second engine mounting
link and a failsafe link;
a center split pylon having two halves secured to one another, said pylon carrying said
first engine mounting link, said second engine mounting link and said failsafe link;
at least one hole on the upper surface of said center split pylon, said hole defined by a
pair of opposing recesses in each half of said center split pylon;
a groove located at the lower portion of said hole;
a shear pin positioned within said hole, said shear pin carrying a flange received
within said groove located at the lower portion of said hole.
16. The engine mounting system of claim 15, wherein said center split pylon has at least
two holes positioned on the upper surface of said center split pylon; a first shear pin retained
within a first hole and a second shear pin retained within a second hole, wherein the first
shear pin reacts force and the second shear pin reacts force only in the event of the failure of
the first shear pin.
17. A method for staking an oriented bearing comprising:
machining a chamfer on a surface within a bearing mounting opening;
machining at least one divot within said chamfer;
positioning a bearing race within said bearing mounting opening;
staking said bearing race within said chamfer;
forcing said bearing race to conform with said divot within said chamfer.
18. A wrench washer tool comprising:
a tool having a first end and a second end,
a first slot positioned on said first end, said first slot defined by parallel side walls,
flanges projecting inwardly from said parallel side walls of said first slot;
a second slot positioned on said second end, said second slot defined by parallel side
walls,
flanges projecting inwardly from said parallel side walls of said second slot; and,
a torque application point projecting outward from said tool.
19. A bearing configured to react forces in a single plane, said bearing comprising:
a bearing race;
two opposing bearing race interfaces;
a cylindrical bearing inner member positioned within said bearing race, said
cylindrical bearing inner member having two curved exterior walls and two parallel exterior
walls wherein said curved exterior walls engage said bearing race interfaces and said parallel
exterior walls define a gap between said cylindrical bearing inner member and said bearing
race on each side of the cylindrical bearing inner member.
20. The bearing of claim 19, wherein said curved exterior walls of said cylindrical bearing
inner member transmit load only to said opposing bearing race interfaces of said bearing race
and said cylindrical bearing inner member slides in the unloaded direction within said bearing
race.