Abstract: Wind tunnel having a free jet test section for simulating wind direction fluctuations, principally for the investigation of vehicles, equipped with a nozzle which can be rotated when the wind tunnel is operating, in order to alter the wind flow direction, in which arrangement the nozzle comprises a stationary part and a rotatable front part and the nozzle front part is surrounded by a cylinder surface which is sealed off in the manner of a plug in the end wall of the nozzle prechamber in relation to the test chamber; within the nozzle prechamber, which surrounds the nozzle, a compensating flow can take place upon rotation of the nozzle front part, so that the quality of the jet flow of the wind tunnel is, if at all, only barely noticeably impaired by the rotational movement. In order to investigate flow-acoustic problems with a varying wind direction, the wind tunnel can be equipped with sound deadening and sound attenuating devices as well as an absorbing lining.

Abstract: Devices and means to conduct indoor model aircraft flight, in an indoor/enclosed space using radio controlled model aircrafts. The aircraft is controlled by available multi channel radio control transmitter/receiver set and available micro size servo motors for control of aircraft surfaces and electric motor. The indoor/enclosed space is lighted, provide with upward air flow, marked by laser light beams and separated from public by transparent barrier to provide a controlled space for engaging in flight of model aircrafts.

Abstract: A device for flight control of a model plane has a plurality of photo cell sensors, preferably, located on the wing tips, nose and tail and connected to a logic circuit inside the body of the plane. The logic circuit, computes the location of the model plane based on the sum and differential output of the sensors, and outputs electronic signals that drive the servo motors controlling the plane. The logic circuit can be calibrated to individually calibrate the rudder, elevator and the throttle electronic signal output, based on the light received by the photo cell sensors. Inside an enclosed space, a focussed beam of light is directed at the model plane. The logic circuit, receives the sensors' output, and using them computes the location of the model plane within the beam of light. The focused beam of light is swivel attached to a motorized control for swiveling the reflector housing in a predetermined pattern of a closed path racetrack holding pattern and a closed path figure eight holding pattern.

Abstract: A device for changing the direction of airflow inside a duct includes a curved panel portion with a leading edge and a trailing edge. The leading edge includes a spanwise extending rounded element which eliminates turbulent separation resulting from the change in airflow direction.

Abstract: A sensor has a sensing region that responds to a surface property by producing an output signal. The sensor has a spatially distributed shape or sensitivity so that the output decreases away from a central part of the sensor, and thus the outputs of plural sensors combined have finite spatial transform as well as high roll off in spatial frequency. Preferably the output decreases to zero at edges of the sensor, and conditions of continuity or vanishing may be imposed on first or higher order derivatives. An edge sensor suitable for mounting at the edge of the structure has its weight function obtained by processes of reflecting and inverting the weight function at an edge. A sensor system employs plural such sensors and edge sensors to produce bounded spatial transfer functions for characterizing the structure. Embodiments of piezeoelectric, resistive, capacitive and thermal sensors are described.

Abstract: For cooling down a cryogenic model, provided for testing in a cryogenic wind tunnel, to the wind tunnel temperature and for performing mounting work and configurational changes on the cryogenic model, there is provided a working chamber which is supplied with warm air so that working personnel can enter it. The working chamber contains an insulating box, made from heat-insulating material, which has an open top and into which cold air is injected. The insulating box accommodates the cryogenic model under cold air conditions. Persons can perform manipulations on the cryogenic model while leaning over the edge of the insulating box. The cryogenic model is held on a holder which can be lifted upwardly out of the insulating box. Removal of the cryogenic model from the working chamber is possible by opening a top door.

Abstract: A coating material for wind tunnel luminescent barometry of surfaces such as airfoils and airframes uses a resin such as poly[1-(trimethylsilyl)propyne], or a siloxane polymer, to carry a pressure indicator. The pressure indicator may be photoluminescent ruthenium complex, such as [Ru(Ph.sub.2 phen).sub.2 ]Cl.sub.2, a photoluminescent platinum complex, such as PtOEP, and photoluminescent mixtures of pyrene and perylene.

Abstract: A temperature responsive sensor is located in the airflow over the specified surface of a body and is maintained at a constant temperature. An active thermal isolator is located between this temperature responsive sensor and the specified surface of the body. The temperature of this isolator is controlled to reduce conductive heat flow from the temperature responsive sensor to the body. This temperature control includes (1) operating the isolator at the same temperature as the constant temperature of the sensor and (2) establishing a fixed boundary temperature which is either (a) less than or equal to or (b) slightly greater than the sensor constant temperature.

Abstract: A wind driven aerodynamic manipulator is provided for imparting motion to an aerodynamic model located in a wind tunnel. The manipulator comprises a support for supporting an aerodynamic body within a wind tunnel; a first aerodynamic surface affixed to the support in such a manner as to allow motion to be imparted to the aerodynamic body by an interaction between the first aerodynamic surface and a fluid flow within the wind tunnel; and a first controller for orienting the first aerodynamic surface with respect to the fluid flow. Additionally, a multi-dimensional manipulator is also disclosed.

Abstract: Methods and compositions for measuring the pressure of an oxygen-containing gas on an aerodynamic surface, by oxygen-quenching of luminescence of molecular sensors is disclosed. Objects are coated with luminescent films containing a first sensor and at least one of two additional sensors, each of the sensors having luminescences that have different dependencies on temperature and oxygen pressure. Methods and compositions are also provided for improving pressure measurements (qualitative or quantitive) on surfaces coated with a film having one or more types of sensor.

Abstract: Method, apparatus, and sensor mast for airfoil aerodynamic performance monitoring are based on pressure measurement. Pressure transducers mounted within the sensor mast measure real-time pressure, to produce an output signal. The signal is separated into steady state and overlaid ripple components. The steady state component corresponds to the mean dynamic pressure of the airflow, while overlaid ripple component corresponds to the superimposed turbulent flow component. The overlaid ripple component is transformed to an amplitude equivalent. A dimensionless ratio of the two components forms a pressure turbulence intensity factor, which may be used consistently to predict and warn of imminent stall conditions. Pressure measurement was found to be an improvement over airspeed measurement. Pressure sensors proved more robust and less fragile than airspeed sensors.

Abstract: A method for providing a perfectly flat top with a sharp edge on a dynamic pressure sensor using a cup-shaped stretched membrane as a sensing element. First, metal is deposited on the membrane and surrounding areas. Next, the side wall of the pressure sensor with the deposited metal is machined to a predetermined size. Finally, deposited metal is removed from the top of the membrane in small steps, by machining or lapping while the pressure sensor is mounted in a jig or the wall of a test object, until the true top surface of the membrane appears. A thin indicator layer having a color contrasting with the color of the membrane may be applied to the top of the membrane before metal is deposited to facilitate the determination of when to stop metal removal from the top surface of the membrane.

Abstract: To generate an unpolluted high enthalpy air blast of several seconds duration a mass of feed air intended to constitute the high enthalpy air blast is preheated to a given temperature and stored at a given pressure in an elongate confinement tunnel with thermally insulative walls. A downstream orifice of the tunnel is kept closed and a blast of high-pressure air is applied to the upstream end of the mass of feed air to compress it quasi adiabatically to obtain a feed air temperature of at least 1,800K. The downstream orifice is opened and application of the high-pressure air blast is continued whereby the mass of feed air is expelled through the downstream orifice in the form of a feed blast, the temperature of which remains constant for several seconds.

Abstract: A temperature responsive sensor is located in the airflow over the specified surface of a body and is maintained at a constant temperature. An active thermal isolator is located between this temperature responsive sensor and the specified surface of the body. The temperature of this isolator is controlled to reduce conductive heat flow from the temperature responsive sensor to the body. This temperature control includes (1) operating the isolator at the same temperature as the constant temperature of the sensor and (2) establishing a fixed boundary temperature which is either (a) less than or equal to or (b) slightly greater than the sensor constant temperature.

Abstract: A luminescent pressure sensitive composition for determining an air pressure pattern includes a binder, preferably a polymer binder, with a luminophore, of which the intensity of luminescence depends on air pressure. The luminophore of which the intensity of luminesence depends on air pressure (active luminophore) is mixed together with an additional luminophore of which the intensity of luminescence has a different dependence on air pressure than the active or reference luminophore.

Abstract: Inlet vortex ingestion is deterred when testing an engine (12) in a test cell (10). Ramp structures (26) are installed on the walls blocking 30% to 50% of the flow area. The apex (42) of these ramps is located adjacent the engine inlet (24) with the upstream faces (46) at about a 45.degree. angle.

Abstract: A system for calibrating an internal balance used in the testing of scale models in wind tunnels including a base; apparatus for rigidly connecting a first portion of an internal balance to the base; force adaptor apparatus for rigidly engaging a second portion of the internal balance; apparatus for securing the force adaptor apparatus to the base, including apparatus for applying selected loads to the force adaptor apparatus so as to cause a corresponding loading on the internal balance; and low friction apparatus for coupling the force adaptor apparatus to the apparatus for securing, including apparatus for transmitting a direct force from the apparatus for applying selected loads to the force adaptor apparatus via a load point whose position relative to the force adaptor apparatus is substantially constant.

Abstract: Disclosed is an airflow sensing system for determining the type of airflow flowing over a flight surface. A hot film sensor is driven by a constant voltage feedback circuit that maintains the voltage across the sensor at a predetermined level. A signal processing circuit receives an output signal of the feedback circuit and determines whether the output signal is indicative of laminar, transitional or turbulent airflow. Transitional airflow is distinguished from turbulent airflow by a signal having significant energy in a low-frequency passband from 50-80 Hz. The signal processing circuit drives a three-color LED display to provide a visual indication of the type of airflow being sensed.

Abstract: Devices and means to suspend scaled flying crafts during test and training flights, in a controlled environment space with a cable/string from a high point in the space, consisting of an electrical slack sensor on the cable/string and a radio controlled electrical system to automatically adjust the slack in the cable/string with the help of an electrically driven winch, permitting the flying craft to fly safely and freely under its own power.

Abstract: A free piston shock tube/tunnel having a mechanism for stopping the piston or controlling the movement of the piston near the diaphragm end of the compression tube. The mechanism includes a generally annular protrusion positioned at the diaphragm end of the compression tube and extending upstream from the diaphragm to engage the piston at a point where the velocity of the piston is substantially at a minimum. The annular protrusion is spaced inwardly from the compression tube and has an inner diameter greater than the diameter of the shock tube.

Abstract: A method and apparatus for directly measuring the time-averaged streamwise momentum in a turbulent stream use a probe which has total head response which varies as the cosine-squared of the angle of incidence. The probe has a nose with a slight indentation on its front face for providing the desired response. The method of making the probe incorporates unique design features. Another probe may be positioned in a side-by-side relationship to the first probe to provide a direct measurement of the total pressure. The difference between the two pressures yields the sum of the squares of the cross-stream components of the turbulence level.

Abstract: A method and apparatus for measuring time-averaged static or ambient pressure and turbulence intensity in a turbulent stream involve placing a plurality of probes in the stream. Each probe responds in a different manner to characteristics of the fluid stream, preferably as a result of having varying cross sections. The responses from the probes are used to eliminate unwanted components in the measured quantities for accurate determination of selected characteristics.

Abstract: A method and portable microcomputer-based system for determining flow field stagnation points are disclosed. The apparatus uses hot film sensors wrapped around the leading edge of an airfoil to measure boundary layer oscillations. A plurality of sensor signals are provided which may be selected in groups. Signals from sensors in any group are read simultaneously. The signals are then converted to digital form and displayed on the video display of a microcomputer. Points of airflow stagnation are characterized by a doubling in frequency or other discrete harmonics and by a reversing of the phase of oscillations. Those points are identified by displaying and comparing signals from different sensor locations on a video display.

Abstract: The nozzle diffuser has an inlet in fluid communication with the narrowed inlet of an open test chamber in a conventional wind tunnel. The nozzle diffuser has a passageway extending from its inlet to an outlet in communication with the open test section. The passageway has an internal cross-sectional area which increases from its inlet to its outlet and which may be defined by top and bottom isosceles trapezoid walls of a particular flare angle and by isosceles trapezoid side walls of a different flare angle. In addition, a collector having a decreasing internal cross-sectional area from inlet to outlet may be provided at the opposite end of the test chamber such that its outlet is in fluid communication with a diffuser located at this outlet.

Abstract: The invention is a method for measuring the wavelength of cross-flow vortices of air flow having streamlines of flow traveling across a swept airfoil. The method comprises providing a plurality of hot-film sensors. Each hot-film sensor provides a signal which can be processed, and each hot-film sensor is spaced in a straight-line array such that the distance between successive hot-film sensors is less than the wavelength of the cross-flow vortices being measured. The method further comprises determining the direction of travel of the streamlines across the airfoil and positioning the straight-line array of hot film sensors perpendicular to the direction of travel of the streamlines, such that each sensor has a spanwise location.

Abstract: An improved wind tunnel six component balance having an outer shell assembly that receives a tubular inner rod and an axial member that is received within the interior of the tubular inner rod. The forward and aft ends of the outer shell assembly are connected to the inner rod. The loads imposed on the forward and aft ends of the outer shell assembly are transferred to the inner rod and into the tunnel support system. The central annular section of the outer shell assembly is connected to the axial adapters (four each and into the central disk of the axial member. The principal areas of the axial element are the central disk member, the flexures (two sets forward and two sets aft), the forward and aft gauged sections, and the forward and aft disk members. Normal force, side force, and rolling moment are carried by the outer forward webs of the outer shell assembly. The axial member will transfer the majority of the axial force then the forward and aft outer shell webs.

Abstract: A shear stress sensor is fabricated using wafer bonding technology. The shear stress sensor is a floating element shear stress sensor designed to measure shear stresses of about 1 kPa-100 kPa over a wide range of operating conditions (temperature, humidity), as well as for a large variety of fluids. The sensor employs a silicon plate suspended about 1.4 microns above the surface of a silicon substrate by piezoresistive arms. The arms are directed parallel to the flow of interest and are loaded in tensile or compressive stress. The piezoresistive arms convert the strain to an electrical output which can be configured in a half bridge circuit with appropriate wiring. Fabrication of the sensor includes bonding a substrate silicon wafer and a device wafer which has an epitaxial silicon layer grown on top of a p+ dopant layer. The device wafer is etched back using the p+ layer as an etch stop. After selective removable of the p+ layer, ohmic contacts are formed through implantation and metalization techniques.

Abstract: A method for visualizing off-surface flows consists of releasing a gas with infrared absorbing and emitting characteristics into a fluid flow and imaging the flow with an infrared imaging system. This method allows for visualization of off-surface fluid flow in-flight.

Abstract: Methods and compositions for measuring the pressure of an oxygen-containing gas on an aerodynamic surface, by oxygen-quenching of luminescence of molecular sensors is disclosed. Objects are coated with luminescent films containing a first sensor and at least one of two additional sensors, each of the sensors having luminescences that have different dependencies on temperature and oxygen pressure. Methods and compositions are also provided for improving pressure measurements (qualitative or quantitive) on surfaces coated with a film having one or more types of sensor.

Abstract: A housing block is provided having an upper surface conforming to the test surface of a model or aircraft. An oil film is supplied upstream of a transparent wedge window located in this upper surface by an oil pump system located external to the housing block. A light source located within the housing block supplies a light beam which passes through this transparent window and is reflected back through the transparent window by the upper surface of the oil film to a photo-sensitive position sensor located within the housing. This position sensor allows the slope history of the oil film caused by an aerodynamic flow to be determined. The skin friction is determined from this slope history. Internally located mirrors augment and sensitize the reflected beam as necessary before reaching the position sensor. In addition, a filter may be provided before this sensor to filter the beam.

Abstract: A laser scintillometer measures the variance of the log intensity of diverged laser light received via a first path. A large aperture scintillometer measures the variance of the log intensity of light from an incoherently illuminated source received via a second path. The ratio of the two measured variances gives the inner scale of turbulence. The refractive-index structure parameter is derived from either measured variance and the inner scale. A processor then derives values of fluxes, such as heat flux and momentum flux, from the refractive-index structure parameter and the inner scale of turbulence using Monin-Obukhov similarity relationships.

Abstract: A method and apparatus for sensing wave flow across a surface wherein at least two pressure levels are sensed and combined to provide a representation of waves within the flow. In the preferred embodiment holes bored through the aircraft surface at an interval of one-half the wavelength of the flow being measured introduce pressure perturbations into a cavity so they may acoustically interfere. The interfering waveform is sensed by at least one microphone disposed in the cavity.

Abstract: A sample in a wind tunnel is radiated from a thermal energy source exteriorly of the wind tunnel. A thermal imager system, also located exteriorly of the wind tunnel, reads surface radiations from the sample as a function of time. The produced thermal images are characteristic of the heat transferred from the sample to the flow across the sample. In turn, the measured rates of heat loss of the sample are characteristic of the flow and the sample.

Abstract: An infrared visualized air turbulence method in which helium is mixed with a heavier-than-air tracer gas such as nitrous oxide in order to cause the density of the tracer gas to be approximately equal to the density of the ambient air stream under study. To enable more accurate measurement of the velocity of the air stream, tracer gas is injected into the stream in a direction extending substantially perpendicular to the direction of flow if the stream. In one of the methods of the invention, an infrared camera and a warm background are placed on one side of an air stream and reflective surfaces are located at opposite sides of the air stream in order to enable infrared visualization of air flow in situations where it is not possible to locate the camera and the warm background on opposite sides of the air stream.

Abstract: A free piston shock tube/tunnel having a mechanism for increasing the holding time, without correspondingly increasing viscous losses in which the shock tube/tunnel includes a diaphragm positioned in the area of connection between the compression tube and the shock tube and a selectively replaceable orifice insert positioned near the diaphragm in which the orifice insert has an opening with a diameter less than the internal diameter of the shock tube.

Abstract: An improved wind tunnel six component balance that is capable of accurately measuring low loads and high loads. The variable range balance has low load axial elements that will measure low loads precisely. When the load is increased over the low range capability of the measuring elements, in either the positive or negative load direction, pressure is applied to either the forward or aft bellows that are mounted in the inner tubular rod of the balance. This pressure applies a counter balance in force that reacts against the load applied. The results of this force is that the low loads links will always stay on range.

Abstract: A wind tunnel having a test section and a fan section, interconnected by two passageways to form a recirculating air flow through said sections. There is a diffuser immediately downstream of the test section, and a second diffuser immediately downstream of the fan section. Each diffuser has an intermediate flow section where the side wall extends radially outwardly in a downstream direction at a relatively sharp angle. At the upstream end of the intermediate section there is a peripheral suction slot to draw in boundary layer air, and a by-pass passageway to discharge the air tangentially in a downstream location of the diffuser. This enables a substantial reduction in air velocity in a relatively short axial length.

Abstract: A sample in a wind tunnel is radiated from a thermal energy source exteriorly of the wind tunnel. A thermal imager system, also located exteriorly of the wind tunnel, reads surface radiations from the sample as a function of time. The produced thermal images are characteristic of the heat transferred from the sample to the flow across the sample. In turn, the measured rates of heat loss of the sample are characteristic of the flow and the sample.

Abstract: An improved static pressure probe containing a water cooling mechanism. This probe has a hollow interior containing a central coolant tube and multiple individual pressure measurement tubes connected to holes placed on the exterior. Coolant from the central tube symmetrically immerses the interior of the probe, allowing it to sustain high temperature, in the region of 2500.degree. F., supersonic jet flow indefinitely, while still recording accurate pressure data. The coolant exits the probe body by way of a reservoir attached to the aft of the probe. The pressure measurement tubes are joined to a single, larger manifold in the reservoir. This manifold is attached to a pressure transducer that records the average static pressure.

Abstract: Light from a plurality of light emitting diodes is transmitted through optical cables (12) to a lens system. The lenses (56, 58) expand and collimate the light and project it in a sheet (16) across the supersonic inlet of an aircraft power plant perpendicular to incoming airflow. A normal shock bends a portion of the sheet of light (16). A linear array of a multiplicity of optical fiber ends collects discrete samples of light. The samples are processed and compared to a predetermined profile to determine the shock location.

Abstract: A method is provided for visualizing aerodynamic flow effects on a test surface. First, discrete quantities of a sublimating chemical such as naphthalene are distinctively colored via appropriate dyes or paints. Next, a uniform layer of the sublimating chemical having a particular color is applied to the test surface. This layer is covered with a second uniform layer of a different colored sublimating chemical, and so on until a composite of multi-colored layers is formed having a discrete thickness. Friction caused by an airflow results in the distinctly colored layers being removed in proportion to such aerodynamic flow characteristics as velocity and temperature, resulting in a multi-colored portrait which approximates the airflow on the underlying test surface.

Abstract: A dual strain gage balance system for measuring normal and axial forces and pitching moment of a metric airfoil model imparted by aerodynamic loads applied to the airfoil model during wind tunnel testing includes a pair of non-metric panels being rigidly connected to and extending towards each other from opposite sides of the wind tunnel, and a pair of strain gage balances, each connected to one of the non-metric panels and to one of the opposite ends of the metric airfoil model for mounting the metric airfoil model between the pair of non-metric panels. Each strain gage balance has a first measuring section for mounting a first strain gage bridge for measuring normal force and pitching moment and a second measuring section for mounting a second strain gage bridge for measuring axial force.

Abstract: A micromachined diaphragm is positioned across a gap from an end of an optic fiber. The optic fiber and the diaphragm are integrally mounted. The end of the optic fiber provides a local reference plane which splits light carried through the fiber toward the diaphragm. The light is split into a transmitted part which is subsequently reflected from the diaphragm, and a locally reflected part which interferes with the subsequently diaphragm reflected part. The interference of the two reflective parts forms an interference light pattern carried back through the fiber to a light detector. The interference pattern provides an indication of diaphragm deflection as a function of applied pressure across the exposed side of the diaphragm. A detection of magnitude and direction of diaphragm deflection is provided by use of a second fiber positioned across the gap from the diaphragm. The second fiber provides an interference pattern in the same manner as the first fiber but with a phase shift.

Abstract: Deformable wall which is manufactured preferably from reinforced plastic includes least one closed cavity (2) and is arranged in the interior of the wall (1). A device (6) to change the cavity pressure is provided. The cavity pressure is decreased or increased to deform the wall (1).

Abstract: A device for changing a direction of an airstream, which comprises a plurality of spaced airstream direction control plates arranged in parallel in a plane perpendicular to the direction of flow of the airstream. The airstream direction control plates are swung about corresponding swing axes positioned at the downstream ends of the airstream direction control plates, to change the direction of flow of the airstream.

Abstract: An environmental wind tunnel facility for automotive vehicles, such as passenger cars, is provided with a slotted-wall extension which improves the air flow simulation over the entire vehicle and enables a reduction in the physical size of the environmental wind tunnel.

Abstract: A tiltable telescoping column is equipped with a rotating upper joint. The upper joint has an aircraft model support member for securing the model to the joint. The length of the telescoping column may be varied as its inclination changes. These motions may occur simultaneous with rotation of the upper joint so that the upper joint is capable of describing a vertically oriented circle of constant radius. The column may be mounted to a turntable for achieving compound angle displacement of the model.

Abstract: A wind tunnel for testing aerodynamic surfaces, comprising a rotor defining a cylindrical cavity for circulating a gas around the periphery of the cavity, first and second elements each having inner and outer surfaces extending between a nozzle end and an exhaust end of the wind tunnel, the elements being mounted in opposed relation in the cavity, the inner surfaces of the elements cooperating to define a nozzle, a test region and an exhaust region, the scoop surface disposed proximate the nozzle for diverting a predetermined portion of circulating gas through the nozzle, test region, and exhaust region, the exhaust region being open to the cavity to permit the diverted gas to rejoin the circulating gas, and a sting for mounting the aerodynamic surface in the test region.

Abstract: A sting for supporting and spinning small diameter models in a wind tunnel consistsing of a rear section securable within a standard wind tunnel, a cone shaped region at the front end of the rear section and a small diameter, model supporting, front section upon which a balance and a model can be mounted; an electric motor within the rear section aligned along the string axis; a drive gear mounted on the motor shaft; a driven shaft parallel to the motor shaft and extending from the motor to the cone shaped region, a driven pinion at the rear end of the driven shaft in meshing contact with the drive gear, a drive pinion at the front end of the drive shaft, a driving sleeve on the front section having a driving gear secured to its rear end and in engagement with the drive pinion, and a pair of spigots at the front end of the driving sleeve for contacting a model to be tested.

Abstract: A strain gauge balance consisting of an outer longitudinal shell and a monopiece inner center core; the outer shell having a open end and a closed end with a frustoconical bore extending towards the closed end, and the inner core having frusto conical shaped ends, one end being sized to fit within the frusto conical core and the other end being sized to fit into a sting; four radially extending, equally spaced, webs formed within the core and at each end of the core inboard of the frusto conical ends, and a central region of two longitudinally separated, semicircular cross-section parts each being formed within the part, with tensioning rings, one disposed diagonally to the other, and a number of strain gauges secured to the webs and the rings to determine induced strain in 6 degrees of freedom.