Abstract: The resonator includes pendular bodies, each oscillating around an axis on a support coaxial with the rotor mast and rotated by the rotor head around the axis of the rotor at a rotational speed above the rotational speed of the rotor.

Abstract: A damper for the blades of a turbine rotor for attenuating the vibrations excited in a radial direction by configuring the damper to have at least two legs bearing against the blade and the disc supporting the blade for grounding the radial vibrations transmitted radially through the damper and offsetting the center of gravity of the damper from the point of contact with the blade.

Abstract: A method and apparatus are provided for balancing a ceiling fan suspended from the ceiling, with the fan having a plurality of blades rotatable about a centerline axis of the fan. The method comprises the steps of attaching at least one test clip to each one of an adjacent pair of the fan blades with the fan stationary, operating the fan on high speed in a downdraft direction with the test clips attached and observing the fan wobble. These steps are repeated for each adjacent pair of blades to identify the pair of blades producing the minimum wobble. The method also includes the steps of determining the optimum radial position of each of the test clips, with respect to wobble, and replacing each clip with a balance weight secured to the corresponding blade. A test clip according to the present invention may be used, with the clip comprising upper and lower members, each having a generally D-shaped configuration, and a connecting member interconnecting the upper and lower members.

Abstract: A vibration isolator (20) operative for reducing vibration active on a main rotor (12) of a rotorcraft. The vibration isolator (20) includes a hub attachment fitting (22) secured in combination with the main rotor (12) and a spring-mass system (24) mounting to and rotating with the hub attachment fitting (22). The vibration isolator (20) is characterized by the spring-mass system (24) having a fairing (44) operative to aerodynamically contour the spring-mass system (24) while providing a portion of the working mass thereof. Other features of the vibration isolator include adapting the hub attachment fitting (22) to accept hub-mounted rotor systems (36), provide access to the rotor hub mounting attachment (34), and provide a motion limiting portion (74) for reducing loads acting on the spring-mass system (24).

Abstract: A new apparatus and method for dynamically absorbing resonant vibration in jet engine blades and other rotating turbomachine components over all engine speeds is disclosed. A distributed pendulum (a pendulum having its axis of motion inside its body instead of at an end) is mounted inside a jet engine blade to function as a centrifugal pendulum. A centrifugal pendulum can be tuned so that its natural frequency linearly tracks the rotational speed of the engine or other turbomachine in which it is mounted and can absorb resonant vibrations from turbomachine components whenever the frequency of a source of vibratory excitation from a so-called speed line of the turbomachine coincides with a resonant frequency of the component. The equations of motion of a distributed pendulum are derived to show that a distributed pendulum small enough to fit inside a turbomachine component can be tuned to track a turbomachine speed line by adjusting its mass distribution about its axis of motion.

Abstract: A fan blade includes a metal airfoil having first and second opposite sides extending longitudinally between a root and a tip, and laterally between a leading edge and a trailing edge. The airfoil further includes a plurality of fine striations spaced laterally apart between the leading and trailing edges in the airfoil first side, and extending longitudinally between the root and the tip. A viscoelastic filler is bonded in the striations for damping torsional vibrations of the airfoil.

Abstract: An inertial mass (50) for a vibration isolator (20) having an attachment fitting (22) adapted for rotation about an axis (16) and a spring (40) adapted for rotation with the attachment fitting (22). The inertial mass (50) is characterized by a pair of segments (52) each having a generally Z-shaped cross-sectional configuration. More specifically, each segment (52) defines a central web (54), a first leg (56) projecting radially inboard of the central web (54) and a second leg (58) projected radially outboard of the central web (54). The first and second legs (56, 58) are integral with the central web (54) and the second legs (58) are adjoined along a mating interface (I) to define the assembled inertial mass (50). As assembled, the inertial mass (50) is adapted for being mounted in combination with the spring (40) of the vibration isolator (20).

Abstract: A bladed rotor for the high pressure compressor of a gas turbine engine comprises a disc carrying an annular array of aerofoil blades in axially extending fir tree root slots. Retention plates carried in radially inner and outer slots prevent axial movement of the blade roots in their slots. A locking member is interposed between an adjacent pair of retention plates to prevent their circumferential movement relative to the disc. The locking member in turn interacts with the disc to anchor itself to the disc.

Abstract: A vibration absorber having a mass member which when static is supported by in-plane springs spaced apart from a base plate, top plate and spring retaining structures. The mass member has a bumper surface for contacting a motion limiter in the base plate. The mass member, base plate and top plate can have a passageway through the axis. The vibration absorber can be tuned by proper selection of the springs, degree of precompression and the variation of the amount of mass by the addition or removal of mass tuning weights.

Abstract: An apparatus has at least one pendulous member mounted on a rotor so as to be able to swing about an axis of pendular motion spaced at a distance from the center of inertia of the pendulous member. The pendulous member is pivotably mounted on its own axis of rotation parallel to the axis of pendular motion and situated substantially closer to the center of inertia of the pendulous member than to the axis of pendular motion.

Abstract: A dynamic balancing apparatus including an annular chase enclosing at least one weight for automatically and continuously eliminating rotational imbalance in ceiling fans.

Abstract: A rotor disk arrangement for a turbojet engine includes a balancing and damping system which has a ring having a circumferential surface recessed with housings and balance masses respectively positioned in the housings. A disk having a circumferential surface is provided which engages the circumferential surface of the ring. The circumferential surfaces are provided with a plurality of bayonet couplings, the couplings including a tenon and a groove engaged with the tenon. The groove includes a straight entrance portion which is substantially parallel to the axis of the engine and a crooked hind part which is substantially circumferentially positioned in the engine. In addition, a plurality of tongues are provided which are respectively inserted into the entrance portions of the grooves and fastened to the ring.

Abstract: Trim balancing of rotating components in the past has increased manufacturing cost. In many past applications, the time and energy required to trim balance rotating components required partial disassembly of an outer case or structure member. The present trim balancing system allows the gas turbine engine to be balanced with the outer case in situ. Access to a rotating component from the exterior of the case is made possible by a compressor air flow path and a pair of holes. The balancing can be accomplished by adding or removing weights or plugs to a band assembled on the rotating component.

Abstract: A dynamic vibration absorber for a rotating machinery element preferably of the bifilar pendulum vibration absorber type wherein the absorber system includes one or more pair(s) of masses having identical paths of movement relative to the axis of the rotating element whose vibrations are being absorbed, the individual absorber masses of a given pair moving out-of-phase with respect to one another relative to the rotating element wherein a disturbance torque with a frequency that is a multiple of the rotation rate of the rotating element is absorbed by a one-half relative frequency motion of the corresponding half-order absorber pair. The half-order absorber pairs are driven primarily by centrifugal forces, move with a frequency one-half that of the disturbance torque and use non-linear Coriolis forces as the source of the counteracting torque.

Abstract: A fluid propulsion device having blades and a surrounding frustroconical housing which rotates with the blades to accelerate fluid flow through the device. The device may be part of a marine drive or part of a fluid pump or motor.

Abstract: A blade of a built-up marine propeller is balanced by forming an open cavity of a predetermined size at a predetermined location proximate to the blade tip, conducting a spin-balancing test in which the blade being balanced and a calibration blade are assembled diametrically opposite each other on a dummy hub to form a simulated two-blade propeller, determining from the test the weight that must be added to the blade to balance the simulated propeller, and affixing a balance member of a predetermined weight in the blade cavity. A cover plate is secured in the cavity opening of the blade in sealed relation, and the external surface of the cover plate is ground to make it fair to the profile of the portion of the blade face adjacent the cavity opening.

Abstract: A rotor blade balance weight assembly comprises a weight retention housing (10) having a hollow core (22) and being closed on one end (12). The housing is disposed in an aperture which extends from the upper (52) to the lower (53) airfoil surfaces of the rotor blade (50). The closure end of the housing is contoured to match the airfoil upper surface contour. A stud (70) extends along the central axis of the housing, and washer-like balance weights (72) are received over the stud and secured by a locking nut (75). The open end of the housing is closed by a cover plate (25) that is contoured to match the airfoil lower surface contour, the cover plate being secured to the housing by a nut (78) in locking engagement with the stud. A pair of clips (37) are received within the housing, each clip having a tab surface (40) which extends through slots (42) in the housing, the clips being secured by the locking nut and stud.

Abstract: A twisted compressor or fan hollow blade is damped by an internal loose slug. The slug contacts the skin of the blade at two transversely spaced locations. This slug is located with its center of gravity eccentric of a radial line through the contact location.

Abstract: A method for balancing the rotor of a wind turbine and a balancing weight. The weight is formed of a piece of steel or other material of sufficient weight bent in an L shape with holes that allow it to be bolted onto a flange at the root of the wind turbine's blades. The width, thickness, or length of the weight can be varied to produce balancing weights of unique weight and radius from the rotor's axis of rotation. A trial weight is disclosed for use with the so-called four run method of determining the rotor's unbalance. The trial weight can be quickly and easily attached and removed.

Abstract: A fluid driven turbine motor having a turbine shroud and a rotor assembly attached to a central portion within the turbine shroud. The rotor assembly includes a rotor and a plurality of vertical vanes mounted thereto and extending radially outward therefrom. The turbine shroud also includes a plurality of intake ports directing a fluid flow to the vanes. The intake ports are positioned such that the fluid flow directed by the intake ports exert balanced forces onto the vanes. The motor may optionally include a retractable centrifugal weight assembly and ports for draining moisture from the rotor assembly.

Abstract: The invention concerns a system for reducing the resisting torque which must be overcome in changing pitch of aircraft propeller blades. The resisting torque includes gas twisting moment and centrifugal twisting moment. The invention includes a bearing system which derives a torque from radial motion of the blade, the radial motion being induced by centrifugal force. The derived torque opposes the resisting torque. The derived torque can also be used to not only oppose, but also overcome, the resisting torques. Such overcoming can be desirable because the resisting torques can drive the propeller blades into a flat pitch position if the pitch change mechanism fails.

Abstract: Damping of a turbine rotor is attained by a weighted member trapped between pockets formed in the neck of adjacent blades at one end and a space between the disk and TOBI rotor seal and forward extending blade lug at the other end. The feather seal which is a curved plate fits over the top of the weighted member and is trapped between nubs formed on the front and rear underside of the blade platform. The front face of the rim of the disk at the disk cavity is open ended and blocked off at the rear face. This assembly allows for individual blade removal and viewing from the rear face by removing a single rim cavity cover without disturbing the remaining components of the assembly. The inverted ring supports take up the axial loads alleviating the loads heretofore taken up by the TOBI rotor seal, allowing for a lighter weight installation.

Abstract: The selection of the mass of a mechanical damper 20 for a blade 12 in a turbine wheel 10, 12 independent of the size of a damper receiving opening 22 is achieved by making the damper 20, 40, 50, 60, partially hollow (FIG. 4) or completely hollow (FIGS. 5-7, inclusive).

Abstract: A variable-pitch bladed rotor including a plurality of blades extending outwardly from a hub in which they are each mounted by a respective ball-screw device. Each device comprises inner and outer races each provided with at least one helical groove, a plurality of balls co-operable with the grooves, and a cylindrical cage disposed between the races which is suitably apertured for accommodation of the balls. The cage supports gearing so associated with the inner and outer races that on pitch-change movement of the respective blade the cage is positively driven, thereby to turn about the blade longitudinal axis.

Abstract: A method of dynamically balancing an assembly of a metal jig and a ceramic rotor attached thereto, the ceramic rotor having a shaft portion, and the metal jig having at its one axial end a fixing hole, comprising the steps of: inserting the shaft portion of the ceramic rotor into the fixing hole of the metal jig, and thereby fixing the ceramic rotor to the metal jig to provide the assembly; and dynamically balancing the assembly by fixing at least one balancing piece in at least one of a plurality of balancing holes which are formed in the metal jig, the balancing holes being open in an outer surface of the metal jig. Also disclosed is a metal jig of a generally cylindrical shape for rotating a ceramic rotor in a dynamically balanced condition, having a fixing hole in its one axial end portion, in which a shaft portion of the ceramic rotor is inserted and fixed.

Abstract: An aerogenerator or wind motor comprises a variable pitch propeller rotor. It comprises compensation means (13) which are sensitive to the deceleration of the rotor to automatically exert on each blade (3), in case of deceleration of the rotor, a force which is substantially equal and opposed to the perturbating force generated by the kinetic energy of the rear or unbalanced mass of the blade.

Abstract: A tunable vibration absorber in a helicopter rotor hub arrangement with a central mass suspended in a symmetrical outer casing over the rotor hub, including an air spring for variably stiffly supporting said central mass in three dimensions.

Abstract: A blade vibration damper for a rotor assembly of an axial flow machine seats simultaneously on a radially inwardly facing surface of a blade platform and the radially inwardly facing surface of an adjacent element, such as the platform of a circumferentially adjacent blade. The damper has its mass center of gravity nearer one contact area than the other so as to reduce the normal load on the blade platform generated by centrifugal force. By properly locating the center of gravity of the damper, the size of the normal force can be optimized to maximize damping.

Abstract: A fixed frequency vibration absorber adapted to be fixedly mounted in a fixed vibration prone system. The vibration absorber is of the pendular-type with two dynamic masses suspended in pendular fashion from a base member, and with at least one coil spring acting upon the masses to establish and linearize the vibration absorber natural frequency.

Abstract: Helicopter rotor on which static balancing of the rotor is provided for by a number of annular-shaped counterweights housed inside each pin securing each blade to the hub; the said counterweights being supported by a rod pressed an clicked inside an axial hole on the relative pin.

Abstract: Low excitation frequencies of a structural component, for example of a heopter rotor blade or the like, are damped or eliminated by a pendulum device connected to the component, the excitation frequency or frequencies of which are to be damped or eliminated. In a helicopter rotor blade the pendulum device is preferably connected to the blade neck near the rotor head. The pendulum device has a plurality of pendulum bodies coupled to each other for forming a multiple pendulum in which these pendulum bodies are so tuned relative to each other that the multiple pendulum has several eigenfrequencies.

Abstract: A structure (10) for reducing vibratory airloading in a rotor blade (12) with a leading edge (14) and a trailing edge (16) includes a cut-out portion (18) at the trailing edge. A substantially wedge shaped cross-section, inertially deflectable tab (20), also having a leading edge (22) and a trailing edge (24) is pivotally mounted in the cut-out portion. The trailing edge (24) of the tab (20) may move above and below the rotor blade (12). A torsion strap (26 or 64) applies force against the tab (20) when the trailing edge (24) of the tab (20) is above and below the rotor blade (12). A restraining member (92) is slidably movable along the torsion strap (64) to vary torsional biasing force supplied by the torsion bar (64) to the tab (20). A plurality of movable weights (82) positioned between plates (84) and (86) vary a center of gravity of the tab (20). Skin (74) of the tab (20) is formed from unidirectional graphite and fiberglass layers.

Abstract: In order to damp possible vibration of a rotor blade for a gas turbine engine, the blade has a hollow tip portion with an internal surface extending across the direction of the centrifugal field on the blade. A weight comprising e.g. Silicon Nitride or Carbide is caused by centrifugal force to bear on this surface. Relative motion and hence friction between the weight and the surface serves to damp vibration of the blade.

Abstract: A device for damping vibrations of mobile turbine blades, in which the roots of the blades are engaged in recesses distributed over the periphery of a rotor disk on which is anchored, under the rim of the disk, a leading edge flange consisting of sections and a trailing edge flange consisting of a single annular part against which the blade roots and the teeth of the disk rest. Between the root of a blade and the bottom of the recess of the disk is placed, behind the forward flange, a shim in the shape of a wedge which, under the action of centrifugal force, exerts on the blade a force that causes the blade to slide axially so that it contacts trailing edge retaining flange.

Abstract: A blade for a turbomachine having an aerofoil portion and a root portion. The blade is provided with a vibration damper for damping a predetermined vibration of the blade. The damper comprises a closed chamber 14 within the aerofoil portion 13 adjacent the tip of the blade, and liquid 15 within the chamber 14. The volume of liquid 15 is less than the volume of the chamber 14. The chamber 14 is shaped, positioned, and aligned relative to the blade, so that in use the liquid 15 is constrained to form a column which oscillates in the chamber 14 in radial directions and in the same directions as the vibration to be damped. The volume, mass, and viscosity of the liquid are all chosen in relation to the frequency vibration (W.sub.B) of the vibration to be damped and the rotor speed (W.sub.E) so that, in use, the length (L) of the column of liquid is such that ##EQU1## where R=the blade tip radius.

Abstract: A rotor blade for a gas turbine engine is provided with an internal tip damper comprising a damper weight which rotates under centrifugal load to cam itself into engagement between two components of the aerofoil, in particular the interior surface of the hollow aerofoil and the tip of a cooling air entry tube. By altering the degree of offset between the center of gravity of the weight and its support the frictional engagement may be varied.

Abstract: This invention relates to the construction of a turbine rotor having a rotor disc with a plurality of blades, said blades having roots fitted into slots around the periphery of the disc with each blade engaging a stop means to properly position it, said blades being held in place by a cover plate fixed to the rotor disc and said stop means; a pocket is formed on the front face of each blade while an annular groove on said cover plate is positioned over said circumferential ring of pockets. Each pocket has an outer flat surface placed at an angle so that each surface intersects the outer surface of the annular groove; a stiff solid damper having a rectangular surface is positioned in each pocket so that one end of said surface will be supported by the outer surface of the annular groove while the other end of said surface will be supported by the outer surface of the pocket when the damper is thrown outwardly by centrifugal force.

Abstract: An improvement to rotating blades is disclosed in a device that will impose anti-moment forces and result in less stress in the said rotating member. The device consists of a rotating body or gyro which is attached to the said rotating blades, and due to the precession of the gyros, a moment is developed which is counter to the moment forces that are normally imposed on the said blades.

Abstract: The invention relates to a device for damping the vibrations of a rotary-wing aircraft rotor. An annular weight is disposed concentrically of the rotor axis. This weight is supported by at least three resiliently deformable elements such as helical springs, radially biased in directions distributed regularly around the rotor axis. The inner ends of the springs directly bear on a part extending the rotor shaft axially. Their outer ends directly bear on the annular weight so that the spring apply statically balanced centrifugal thrusts to the annular weight. The springs are so still that they support the annular weight without substantially bending.

Abstract: The invention relates to a device for damping the vibrations of the rotor of a rotary-wing aircraft. This device comprises a flapping weight concentrated near the rotor axis and at least three resiliently deformable elements, such as helical springs. The deformable elements are radially biassed in directions regularly distributed around the rotor axis. The inner ends of the deformable elements directly bear on the flapping weight. Their outer ends directly bear on rigid structure elements, rigidly secured to the rotor hub, so that the biassed deformable elements apply statically balanced centripetal thrusts to the flapping weight.

Abstract: A helicopter having a main rotor lift unit includes a plurality of pendulus mass units (44, 46) mounted to oscillate in a plane perpendicular to the chord plane of the rotor blade (10). The mass units (44, 46) are connected to a rotatable shaft (28) which passes through or adjacent the blade grip (12) for each blade (10). Hubshear vibrations generated parallel to the axis of the rotor mast (18) are damped by the oscillating mass units (44, 46) which are tuned to minimize the vibrations transmitted from the lift unit to the fuselage.

Abstract: A helicopter having a multiblade main rotor lift unit includes a plurality of pendulus mass units (48,60) mounted to oscillate in the plane of the rotor. The mass units (48,60) are connected to a rotatable shaft (24) which passes through a blade grip (14) for each blade (16). Vibrations generated in the plane of the rotor system are damped by the oscillating pendulums (22) which are tuned to minimize the vibrations in the lift unit.

Abstract: A vibration absorber for a helicopter rotor includes a hub portion, a mass portion encircling the hub portion and a plurality of resilient arms extending in a spaced-apart spiral pattern between the hub and the mass. In operation, the hub portion of the vibration absorber is mounted on a helicopter rotor so as to be rotated with the rotor about an axis of rotation of the rotor, the resilient arms ensuring that the mass is capable of equal resilient deflection in any direction within its plane of rotation whereby the vibration absorber simultaneously reduces in-plane vibration forces of different frequencies.

Abstract: A bifilar vibration absorber is provided for the main rotor of a helicopter in which the pendular mass is constrained so that the path of motion of its cg relative to the rotor hub is a cycloid.

Abstract: A helicopter main rotor has an improved fairing enclosing the rotor hub and blade root area for drag and vibration reduction purposes. The fairing has peripheral cutouts through which the blades project provided with rounded lips on the rim of the cutouts to streamline air flowing in and out of the fairing through the cutouts. Internal partitions divide the fairing into chambers, each of which subtends one cutout, thus preventing flow of air through the fairing and attendant drag caused thereby. The rotor pylon is provided with a well through which the rotor drive shaft projects having a rounded lip adjacent the fairing to produce streamline airflow out of the well.

Abstract: A load absorbing elastic member or members is incorporated in the design of a rotor blade to assist in reducing flapwise and chordwise bending moments, torsional loading, and to reduce or eliminate the control system loads induced by rotor blade moment stall. In all its embodiments, the load absorbing elastic member has operatively associated therewith a constraining member which serves as a strain amplifier permitting the load absorbing elastic member to achieve its purpose effectively.

Abstract: Helicopter rotor blades require tip weights for spanwise and chordwise bace to assure that all of the blades rotate in the same track. The improved rotor blade tip weight assembly of the present invention comprises an elongated spar, preferably formed of a reinforced plastic, adapted to be connected at one end thereof to a rotor hub. An aft fairing structure is carried by the spar and a balancing weight assembly is bonded and/or cured in place within the spar, proximate the free end thereof. The balancing weight assembly includes, in the preferred form thereof, a fiberglass weight tube housing having a pair of internally threaded weight tubes positioned therewithin. The weight tubes form bores having longitudinal axes in a common, substantially horizontal plane, and the axes each extend in a direction parallel to the axis of the spar. One or a plurality of externally threaded cylindrical weights are locked in each weight tube during balancing of the rotor blade.

Abstract: A vibration isolation system wherein a vibrating mass such as a helicopter rotor-transmission assembly is spring coupled to a body to be isolated, such as the helicopter fuselage, at a plurality of points. Each coupling point includes, in addition to a coupling spring, a weighted lever arm pivotally connected to the vibrating mass and to the body, with the body-to-lever pivot connection lying between the center of gravity of the arm and the vibrating mass-to-lever pivot connection. The coupling spring is in the form of a torsion spring, e.g., torsion bar, coupled between the body and the lever arm at the pivot connection therebetween. Vibratory forces of a predetermined frequency transmitted from the vibrating mass to the body through the spring are substantially cancelled by inertial forces generated by the lever and applied to the body through the body-to-lever pivot connection, thus isolating the body from the vibrating mass at the predetermined frequency.

Abstract: A coverplate damping arrangement is provided for a turbine assembly wherein a sealing and damping pin which extends between and under adjacent bucket platforms is formed with one or more eccentric masses which cause the pin, under the urging of centrifugal force, to rotate into abutment with the coverplate.

Abstract: A helicopter has a plurality of bifilar absorbers mounted on arms radially extended from the hub of the rotor. A bifilar mass of the required weight mounted at the end of an arm of required length to absorb input excitations at a pendulum amplitude of approximately 30.degree. at design forward speed is mounted on an arm twice the length without a reduction in weight of the bifilar mass to limit pendulum amplitude to 15.degree. while maintaining the original force output. Bifilar motion in the linear range with associated elimination of overtuning produces improved bifilar operation at all flight speeds and eliminates second order vibration due to dissimilar motions resulting from overtuning.