Abstract: A method and apparatus for suppressing vibration in turbine blading and the like is disclosed. A damping tube is inserted through an aperture in each of a plurality of turbine blades. By expanding the damping tube after it is inserted in the blades the tube is firmly secured to each blade. A wire may be inserted through the damping tube and is secured by crimping the expanded tube portions. The tube may be divided into circumferential segments with each tube being widened for example by means of a center punch at an end portion which extends through the final blade of each segment.

Abstract: A wind power plant comprising a tower carrying a power system including a power house and vanes rotatable by the wind. The tower has a lower natural frequency of vibration between the lower and higher critical frequencies of vibration of the power system, and the tower has a higher natural frequency of vibration above the higher critical frequency of vibration of the power system. A ring surrounds and is disconnectably attached to the tower, and guy wires extend from the ring to the ground. The power system is assembled on the ground and so that it surrounds the tower, and the power system is then elevated, together with the ring, along the tower. Elevation may be accomplished with cables and a winch. Alternatively, a thread-like ledge may surround the tower and the power house may carry means for engaging and moving along the ledge to elevate and lower the power house.

Abstract: A coupling device of moving blades of a steam turbine comprises a pair of projections provided on the inner and outer surfaces of the adjacent moving blades. One of the projections is provided with a hemispherical recess which loosely and slidably receives a corresponding hemispherical projection provided for the other projection when the moving blades are assembled.

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 wheel or rotor with a plurality of blades arranged at irregular or unequal pitch angles circumferentially of a disk, a hub or the like, wherein the characteristic level e.sub.k representative of the order-of-harmonic characteristic of blade pitch is defined bye.sub.k =10 log.sub.e d.sub.k +100where ##EQU1## Z=a number of blades k=1,2, . . . and n; n.gtoreq.Z.theta..sub.j =the angular position of the tip or root of each blade defined in terms of a central angle subtended at the center of a circle, which is the axis of said wheel or rotor, by an arc extended from a reference point on said circle to said tip or root of each blade on said circle, j=1,2, . . . and Z; andthe characteristic level e.sub.k satisfies the following conditions ##EQU2## where e=-13.14 log.sub.10 Z+99.70k=2,3, . . . n.

Abstract: In a gas turbine rotor of disc-type construction with a tie rod braced at least at one location along the length thereof against compressor or turbine discs by ring-shaped intermediate members, the intermediate members includes substantially conically expansible turning rings having a wider diameter end engageable in a circular groove formed in a lateral surface of one of the discs, the turning rings having at the smaller diameter end thereof an inner peripheral surface with which they are braced on the tie rod.

Abstract: A compensating linkage for the rotor control system on rotary wing aircraft is disclosed. The main rotor and transmission are isolated from the airframe structure by elastic suspension. The compensating linkage prevents unwanted signal inputs to the rotor control system caused by relative motion of the airframe structure and the main rotor and transmission.

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 segmented damper is provided with a lower dovetail portion which is insertable into a dovetail slot for radial retention and which is engageable on its face by a blade retainer for axial retention, such that the damper is pivotable in an axial plane. The damper upper portion has on its one side a flange for engaging the blade shank rail and on its other side a flange for shifting the damper center of gravity axially outward from the lower pivot point. Centrifugal force, occasioned by rotation of the disk and damper, then causes the damper to pivot and impart an axial force against the blade to thereby dampen vibrations.

Abstract: A turbomachine rotor arrangement is provided having a rotor wheel and blades thereon with a tie pin for interconnecting adjacent blades. A plurality of blades respectively define tie holes wherein the tie holes of adjacent blades are disposed with the radial heights of said holes being different and with the tie pin disposed in the tie holes so as to be acted upon by respective different amplitudes of vibration than said adjacent blades during rotation.

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: A sealing arrangement for preventing compressor fan air loss through the relatively wide gaps between adjacent blade platforms required in order to allow for rotation of the blades around their minor root axes in response to bird impact and the like. A thin flexible ribbon-like seal is bonded to one of the two adjacent blade platforms in the fan structure. At the gap, the seal includes a thickened wedge shaped portion with at least one invagination on the inner side facing the rotor axis. At the operating speed of the compressor fan, centrifugal force causes the thickened portion to be forced into the gap between adjacent platforms producing the required seal.

Abstract: A vibration damper for use in a turbine rotor of a high temperature gas turbine is disclosed. The damper is loosely mounted in an opening formed between adjacent blade rails, the end of the rotor disk connector, and sections of adjacent blade necks between the rails and the disk connector. A cover plate positioned against one side of the turbine blade and a projection extending downwardly from the other side of the turbine blade confines the damper axially in the opening.

Abstract: A method for controlling the first torsional node line position in a rotatable blade of a turbomachine to improve its flutter stability including the steps of forming a first monolithic blade having a desired airfoil shape with convex and concave side walls; arranging several of the monolithic blades in a cascade array and subjecting the cascade array to an unsteady, supersonic, transonic and subsonic flow condition thereacross and thereafter determining the unsteady surface pressures acting on the monolithic blades; independently determining the first torsional mode vibration node line of each of the monolithic blades and comparing the resultant unsteady pressure force on the monolithic blades and its relationship to the first torsional mode vibration node line to determine whether or not the monolithic blade is absorbing or adding energy to the air flow thereacross; thereafter forming a plurality of first and thereafter modified composite blades by adding dissimilar material to the blade shape of a monolith

Abstract: A rotor blade stage for a gas turbine engine comprises an annular array of aerofoil blades. Each blade is provided with circumferentially extending platforms which are arranged so as to circumferentially spaced apart from the platforms of adjacent blades. Elastomeric dampers are interposed between adjacent blades and are so adapted that upon rotation of the array of blades, each of the elastomeric dampers is centrifugally urged into engagement with the radially inner faces of adjacent platforms of adjacent blades.

Abstract: A rotor blade stage for the compressor of a gas turbine engine comprising a rotor disc having a plurality of equally spaced apart rotor blades mounted on its periphery. The spaces between the rotor blades in the region of the periphery of the rotor disc are infilled with a mixture comprising reinforcing filaments enclosed in a matrix of a cured epoxy resin and filler material. Means are provided to retain the mixture in position between the rotor blades upon rotation of the rotor disc.

Abstract: Both the disk and the blade retainer have a radially inward extending flange which axially abuts the other. A U-clip ring with its open side disposed radially outward is placed over the two flanges to hold them axially together and means is provided to maintain the U-clip ring in its holding position. In a preferred embodiment, the ring is constructed with its side farthest from the disk having a substantially greater radial height than that of the side closest the disk, and the circumferential length of the U-clip is so sized that there is a relatively small gap between its ends when it is in the installed position. With these features, the ring will remain in its assembled position without any other holding means. Removal can be effected by first radially moving one end of the ring inwardly with respect to the other and then axially moving it until it clears the other end.

Abstract: A motor mount suitable for use, for example, in a motor driven fan assembly or the like in which the motor is secured to the fan housing. The mount includes clamps for supporting the opposite ends of the motor and is adjustable to accommodate motors having different lengths and also to fit different sized mounting bolt locations.

Abstract: A vibration absorber includes a hub arranged for rotation during operation about an aixs, a mass encircling the hub and a plurality of resilient arms extending in a spaced-apart spiral pattern between the hub and the mass so that the mass rotates with the hub in a plane of rotation perpendicular to the axis and is capable of equal resilient deflection in any direction within its plane of rotation. In operation the absorber operates as a spring mass device and finds particular application in damping vibrations in a helicopter rotor due to the facility to simultaneously cancel vibration forces of different frequencies.

Abstract: A vibration dampening means and method for substantially reducing the vibrational frequency of a multi-cylinder air-cooled airplane engine. The engine driving a hydraulic governor pump for a propeller servo. The servo controlling the blades of a variable pitch propeller. The dampening means including a resilient member mounted on the cooling fins of the cylinders, a hydraulic dampener connected with the hydraulic governor pump, and resilient dampeners mounted on the propeller blades.

Abstract: A pinned root blade having a predictable center of rotation when tangentially oscillated and also having a predetermined, axial contact surface which is engageable with a rotatable rotor and which is disposed about the center of rotation in such manner as to provide maximum friction damping of the tangential oscillations.

Abstract: A method of fabricating a turbomachinery blade is provided whereby high stress levels associated with stripe mode resonance can be avoided. Once the nodal pattern for an objectionable stripe mode resonance condition of a metallic blade is determined by conventional means, a portion of the blade parent metal near the tip is replaced with a composite patch, the composite patch comprising elongated filaments embedded in a matrix material. The chordwise extent of the patch includes the nodal points at the objectionable stripe mode resonance condition and the filament orientation is chordwise to enhance chordwise stiffness.

Abstract: A helicopter rotor and transmission mounting and vibration isolation system in which the transmission is supported from the fuselage by a plurality of elastomeric mounts which are selectively positioned and focused to establish a system roll axis and a system pitch axis on opposite sides of the elastomeric mounts and which mount members are of selected stiffness to establish selected roll stiffness and selected pitch stiffness of the system, to establish the natural frequencies of the system sufficiently below the blade passage frequency to minimize the response of the fuselage to forces and moments imparted by the helicopter rotor and to provide selected torque restraint and lift restraint for the system.

Abstract: Rotatable blades are tuned by forming a plurality of ribs on concave air foil surfaces of the blades adjacent trailing edges in longitudinal alignment with the fluid flow.

Abstract: An interblade seal and vibration damper to be positioned in the damper cavity defined between a rotor disc, adjacent blades and adjacent blade platforms so as to seal across an interplatform gap by providing line contact between the damper and the platforms on opposite sides thereof for the full axial dimension of the cavity and with the damper shaped so as to have a low center of gravity for operational stability and which damper also responds to centrifugal force during rotor operation to establish damping friction between said damper and said platforms when the platforms move circumferentially.

Abstract: A rotor for compressors, turbines or the like and having a plurality of circumferentially-spaced blades in which every other blade is modified so that the average natural frequency of said modified blades differs from that of the other blades by at least 4% but by no more than 15% so as to reduce the maximum amplitude of turbine blade vibration.

Abstract: An elastomeric damping arrangement is constructed to provide a highly efficient damping of the vibrations of a vibration prone member, such as an airfoil, especially a helicopter rotor blade. The damping arrangement is applied directly on or to the vibration prone structural member in the region of dynamic deformation, as an integral component part of the structural member. At least one damping layer is covered by a protecting layer which merges smoothly into the surface of the vibration prone member. The damping layer is made of a viscoelastic material having a high internal damping action. The protecting or cover layer is made of high strength material having a high rigidity in the direction of the occurring damping force.

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 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 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.

Abstract: A turbine rotor having twisted blades, are, in the vicinity of their radiy outer portions integrally connected with each other to prevent any rotation in either direction of one blade in relation to its neighboring blades. The blades are prestressed during assembly by being un-twisted through an angle which is less than or equal to and in the same direction as the angle through which said blades would be un-twisted during rotation if they were free to rotate in relation to each other.

Abstract: A rotor blade system which is adapted for long term reliable operation in a gas turbine engine is disclosed. Techniques for altering the natural frequency of the blade system to reduce the detrimental combined effects of external excitation and self-excitation are developed. One structure shown utilizes a shroud for the control of self-excitation in combination with a pin root to lower the fundamental first natural bending frequency of the blade system below the level of the 2E frequency at idle.

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 overturning produces improved bifilar operation at all flight speeds and eliminates second order vibration due to dissimilar motions resulting from overtuning.

Abstract: There is disclosed an axial flow fan assembly having a vibration dampener carried by the fan supporting means which extends across the fan ring.

Abstract: A rotorcraft is subject to a rocking motion when on the ground, which is called ground resonance, and in the air which gives the fuselage a waddle type of motion about its center of gravity. both are a form of aeromechanical instability. This fuselage motion is coupled with and accompanied by bending oscillations of the blades with respect to the hub of the rotor of the rotorcraft. An oscillation damper is described which damps the oscillations of the aircraft and thereby eliminates or substantially reduces the rocking and waddle motion of the fuselage. The damper includes a seismic device having a mass-spring combination tuned to the frequency of the rocking motion which will typically be one half or approximately one half of the rotor revolutions per minute at cruising speed and is positioned laterally of and spaced from the center of gravity of the fuselage.

Abstract: A multibladed helicopter rotor carries at least three bifilar absorbers which are tuned to eliminate in-plane vibrations of the rotor that otherwise would be transmitted to the helicopter fuselage. By drooping the radial support arms for the absorbers out of the plane normal to their axis of rotation, the resultant of the centrifugal forces acting on the pendulous elements of the absorbers and the weight of these elements acts normal to the axes of the tuning pins of the absorbers which minimizes internal frictional damping in the absorbers.

Abstract: A multibladed helicopter rotor carries at least three bifilar absorbers which are tuned to eliminate in-plane vibrations of the rotor which otherwise would be transmitted to the helicopter fuselage. Improved tuning pin assemblies and cooperating tracking inserts for the absorber reduce the undesirable frictional damping heretofore encountered in bifilar absorbers by centering the pendulous elements of the absorbers relative to their support members and reacting forces normal to centrifugal force by permitting flapping movement of the bifilar mass in the vertical plane.

Abstract: A vibration, damper, or snubber device is disposed on the radially outward surface of a shroud member mounted on a turbine rotor. The rotor has an annular array of twisted blades connected together to form blade groups by a first and a second shroud member. The vibration damper, or snubber, is mounted on the first shroud member and extends therefrom across a gap between the shroud members to circumferentially overlap a portion of the second shroud member. A predetermined axial gap is defined between a portion of the second shroud and the snubber. When an untwist motion is imposed upon the blades due to rotation of the rotor, the axial gap closes and an abutment between the snubber and the second shroud occurs to inhibit further untwist motion and to simultaneously provide a friction interface to inhibit circumferential motion between the second shroud and the vibration damper.

Abstract: An axial flow compressor or turbine includes a stator case with a plug which is removable from outside the case, together with one or more stator vanes attached to the plug, to provide access to an adjacent part of the rotor. Such access may be used to add balance weights to the rotor as part of a rotor balancing procedure, or for inspection of rotor blades.

Abstract: The impingement baffle insert of a turbomachinery blade is provided with a plurality of collars around a portion thereof so as to ensure a proper impingement distance between the baffle and the inside wall of the airfoil and act as a wear surface against the inside wall to thereby prevent wear to the insert wall surface. The collars are affixed to the insert in preselected positions and frictionally engage the blade inner wall in close fit relationship to position the inserts and assume any wear that may result from vibration of the insert within the chamber. The inserts may have grooves formed therein to allow equalization of pressure on both sides thereof, and they may further have chamfered edges on one end thereof so as to facilitate installation into the turbine blades.

Abstract: The impingement baffle insert of a turbomachinery blade is provided with a collar around a portion thereof, the collar having a chamfered surface on the radially inner end and adapted to be frictionally engaged by a damper which also surrounds a portion of the insert and which tends to move radially outward over the beveled surface when acted on by centrifugal forces caused by rotation of the blade. The damper is thus wedged between the insert and the blade inner wall to reduce or prevent relative movement therebetween which is normally caused by thermal and vibrational forces. The integrity of the combination is thus improved to reduce the incidence of insert and turbine blade failure.

Abstract: A multi-shaft gas turbine has an inner shaft rotatably supported at opposite ends thereof with one end adapted to be connected to a load and the other end to a turbine wheel with a tubular section that receives a balance tube removably mounted within the shaft and accessible from the aft end of the engine by removal of an inner exhaust cone and a bearing pump cover. The balance tube includes front, rear and intermediate circumferentially arranged splined lands that bear balance weights angularly positioned on the tube prior to insertion thereof into the shaft, each of the weights having a peripheral surface thereon for locating the longitudinal axis of the balance tube colinearly of the longitudinal axis of the inner shaft.

Abstract: A centrifugal compressor assembly for a gas turbine engine includes an inducer section and an impeller section mounted for rotation about an axis. Because leading edges of the impeller blades are cambered, damper pads, extending perpendicular to the low pressure sides thereof also extend axially forward. Blades of the inducer section are indexed rotationally rearward of the impeller blades to improve the distribution of compression gases through the impeller section and high pressure surfaces of the inducer blades mate near their leading edges with outward surfaces of the damper pads. Because the pads and inducer blades vibrate at different frequencies, inducer blade vibrations that might otherwise cause fatigue are attenuated by contact with the damper pads. The damper pad arrangement thus permits the damping of vibrations in the inducer blades notwithstanding the indexed relationship between the inducer section and the impeller section.

Abstract: Vibration in the helicopter fuselage produced through the helicopter rotor at a frequency of one for each rotation of the rotor (commonly identified in the art as a one-per-rev vibration) is controlled by applying a correction signal to the primary cyclic control system of the rotor assembly. To generate the correction signal, a transducer responds to the one-per-rev vibrations to generate a signal coupled to circuitry for generating a vibration related signal dependent upon the amplitude and phase of the one-per-rev vibrations. The vibration related signal is applied to a sample and store network wherein it is demodulated by a reference signal related to the rotational speed of the helicopter to establish a control voltage which varies at a rate in dependence upon variation in the maximum amplitude of the one-per-rev vibrations. This control voltage is integrated and modulated by the reference signal thereby resulting in the correction signal for application to the primary cyclic control system.

Abstract: A helicopter rotor blade having at least one ramp tab of selected span and chord dimensions, weight and shaped to define an outer surface of selected angularity with respect to the blade chord and being selectively positioned along the blade trailing edge and bonded to its upper or lower surface so as to be totally within the blade chord profile and be effective to eliminate or reduce to within acceptable limits blade pitching moment dynamic unbalance.

Abstract: In eliminating one-per-rev vibration in a helicopter due to rotor unbalance, a one-per-rev vibration signal manifestation of rotor unbalance is generated and sampled when the rotor blades are successively in alignment with a reference direction during each cycle of rotation of said rotor. A difference signal is generated from the samples to represent by magnitude and phase the character of the unbalance. The rotor is modified in magnitude proportional to the magnitude of the signal and in direction dependent upon the span and chord components of the signal. In one aspect the force track error signal is applied to the input of a cyclic pitch control actuator system dynamically to automatically correct span unbalance forces.

Abstract: This invention relates to improvements in bifilar vibration dampers, and particularly to such dampers for use in absorbing vibrations in a helicopter main rotor system.The improved bifilar construction prevents detrimental inertia forces affecting the tuning of the damper and also prevents the ingress of dirt and dust into the moving parts.