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At least 37 records · Page 2

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NASA NTRS1986

Experimental investigation of rotorcraft hub and shaft fairing drag reduction

A wind-tunnel test was conducted to obtain data on several rotorcraft hub and shaft fairing drag reduction configurations. Aerodynamic loads and moments were acquired for each test configuration. Limited wake pressure measurements and flow visualization (tuft) photographs were obtained for some configurations. All hub and shaft fairing configurations were tested on a 1/5-scale XH-59A model fuselage. Both coaxial and single rotor configurations were tested. All rotor assemblies were modeled with nonrotating hardware. The drag reduction methods tested included cambered elliptical hub fairings, several different shaft fairings, and strakes. Test data show that significant drag reductions can be attained with certain fairing configurations. The lowest drag values for the single rotor configurations were obtained for a cambered elliptical hub fairing with a large thickness airfoil shaft fairing. The lowest coaxial configuration drag values were obtained with cambered elliptical hub fairings and a long chord intermediate shaft fairing.

Young, L. A.↗

NASA NTRS1988

Designing Shafts For Long Life

Improved method developed for choosing sizes of power-transmitting shafts for limited or unlimited service lives under variety of operating conditions. Stress versus fatigue life of proposed shaft design plotted, modified to account for expected operating conditions and used to calculate shaft diameter required for given fatigue life. If diameter of shaft represented by plot equals or exceeds required diameter, shaft considered adequate.

Loewenthal, Stuart H.↗

NASA NTRS1989

Fiber-Optic Sensor Would Detect Movements Of Shaft

Fiber-optic sensor senses both rotational speed and axial displacement of shaft in motor, pump, or other rotating machine. Does not require magnetic materials, notches, or grooves in shaft. Required modification of shaft is etching or plating surface to make ring black around half circumference and reflective around other half along short length at one end or some other convenient location. Triangular bundle of sending and receiving optical fibers aimed at black/reflective ring on shaft. Frequency and amplitude of output pulses of fiber-optic probe indicates rotational frequency and axial position of shaft.

Roschak, Edmund J.↗

NASA NTRS1990

Shaft-Rotation Detector

Signal-processing subsystem generates signal indicative of rotation of shaft from output of accelerometer mounted on housing of bearing supporting shaft. Output of subsystem binary signal at frequency of rotation of shaft. Part of assembly of electronic equipment measuring vibrations in rotating machinery. Accelerometer mounted in such way sensitive to vibrations of shaft perpendicular to axis. Output of accelerometer includes noise and components of vibration at frequencies higher than rotational frequency of shaft.

Randall, Richard L.↗

NASA NTRS1990

Shaft Adapter For Data Coupler

Shaft adapter developed to provide means for securing Acurex 1200B universal data coupler to rotating instrumented shaft. Consists of two major parts: shaft sleeve and shaft clamp. Provides for accurate measurements of stresses and strains in shaft.

Elliott, James R.↗

NASA NTRS1990

Thermal/structural analysis of the shaft-disk region of a fan drive system

In January 1989, a mishap occurred in the National Transonic Facility wind tunnel at NASA-Langley. It is believed that the failure of an insulation retainer holding foam insulation around the exterior of the fan drive shaft resulted in the subsequent damage to other components in the tunnel. The effect was determined of removing the external thermal insulation on the shaft would have on the stresses on the shaft, disk and bolts holding the two together. To accomplish this, a detailed thermal/structural finite element analysis of the shaft-disk interface was performed. The maximum stresses on the three components were determined for several configurations and conditions with and without the external thermal insulation, and then these results were compared to the original analyses to access the effect of removing the external thermal insulation on the proposed future operation of the shaft/disk structures of the fan drive system. Although the stresses were higher without the external insulation, the stresses did meet all stress criteria. In addition, all stresses were within the infinite life regime of the Modified Goodman diagram. Therefore, it was determined that the structural integrity of the shaft-disk region is not compromised if the external insulation is removed.

Gregory, Peyton B.↗

NASA NTRS1989

Integrated controls and health monitoring fiberoptic shaft monitor

Recent work was performed on development optical technology to provide real time monitoring of shaft speed, shaft axial displacement, and shaft orbit of the OTVE hydrostatic bearing tester. Results show shaft axial displacement can be optically measured (at the same time as shaft orbital motion and speed) to within 0.3 mills by two fiber optic deflectometers. The final results of this condition monitoring development effort are presented.

Coleman, P.↗

NASA NTRS1995

Tachometer Derived From Brushless Shaft-Angle Resolver

Tachometer circuit operates in conjunction with brushless shaft-angle resolver. By performing sequence of straightforward mathematical operations on resolver signals and utilizing simple trigonometric identity, generates voltage proportional to rate of rotation of shaft. One advantage is use of brushless shaft-angle resolver as main source of rate signal: no brushes to wear out, no brush noise, and brushless resolvers have proven robustness. No switching of signals to generate noise. Another advantage, shaft-angle resolver used as shaft-angle sensor, tachometer input obtained without adding another sensor. Present circuit reduces overall size, weight, and cost of tachometer.

Howard, David E.↗

NASA NTRS2007

Shaft seal assembly and method

A pressure-actuated shaft seal assembly and associated method for controlling the flow of fluid adjacent a rotatable shaft are provided. The seal assembly includes one or more seal members that can be adjusted between open and closed positions, for example, according to the rotational speed of the shaft. For example, the seal member can be configured to be adjusted according to a radial pressure differential in a fluid that varies with the rotational speed of the shaft. In addition, in the closed position, each seal member can contact a rotatable member connected to the shaft to form a seal with the rotatable member and prevent fluid from flowing through the assembly. Thus, the seal can be closed at low speeds of operation and opened at high speeds of operation, thereby reducing the heat and wear in the seal assembly while maintaining a sufficient seal during all speeds of operation.

Keba, John E.↗

NASA NTRS2026

Manufacturing Process Development of a Carbon Fiber Reinforced Polymer Composite Shaft for Electric Motors

Electric aircraft applications require electric motors with increased specific power and efficiency. Composite structural components in motors are a potential solution for reducing motor mass, reducing magnetic losses, and limiting undesired conduction paths for fault, electromagnetic interference, or common-mode currents. In this report, manufacturing trials for a high-speed carbon fiber reinforced polymer composite motor shaft are presented. Four prototype shafts were produced using a hybrid biaxial/triaxial fabric that was circumferentially wrapped onto an additively manufactured high-temperature washout mandrel. An additional traditional overbraid approach was also evaluated and shows promise for high-rate, high-performance parts using automated manufacturing. This paper discusses the shaft design, manufacturing methods explored, material selection, the manufacturing trials, and the lessons learned. The results of this manufacturing investigation show feasibility for manufacturing composite shafts for electric motors.

Electric moto shaft↗

NASA NTRS1966

Intermediate rotating ring improves reliability of dynamic shaft seal

Intermediate rotating ring improves the reliability of dynamic shaft seals whose rubbing surfaces wear down rapidly at high shaft speeds. The rotating ring is placed between the rotating shaft sealing surfaces and the stationary surface, and driven at one-half the shaft speed.

Mesny, P. R.↗

NASA NTRS1972

Comparative lubrication studies of OH-58A tail rotor drive shaft bearings

Comparative lubrication tests were run with OH-58A helicopter tail rotor drive shaft bearings. The tests were run in an outdoor environment with ambient temperatures ranging from 10 to 75 F. Dust was periodically applied to the bearings to simulate field conditions. The cause of bearing failure was associated with dust penetration. Rotor shaft failure was found to be caused by the shaft rotating in the standard rubber collar due to seizure of the bearings. Bearings with a positive rubbing seal having a MIL-G-81322 grease produced lives greater than with bearings having labyrinth seals and a mineral oil paste lubricant. An elongated collar prevented failure of the rotor shaft during bearing seizure. In a limited test, installation of tail boom shrouds over the bearings which excluded dust and water resulted in bearing lives in excess of 1800 hours or 1200 hours greater than the current 600 hours TBO, regardless of the lubricant-bearing combination used.

Dietrich, M. W.↗

NASA NTRS1977

Performance of large-bore tapered-roller bearings under combined radial and thrust load at shaft speeds to 15,000 rpm

The performance of 120.65-mm bore tapered roller bearings was investigated at shaft speeds up to 15,000 rpm. Temperature distribution and bearing heat generation were determined as a function of shaft speed, radial and thrust loads, lubricant flow rate, and lubricant inlet temperature. Lubricant was supplied by either jets or by a combination of holes through the cone directly to the cone-rib contact and jets at the roller small-end side. Cone-rib lubrication significantly improved high-speed tapered-roller bearing performance, yielding lower cone-face temperatures and lower power loss and allowing lower lubricant flow rates for a given speed condition. Bearing temperatures increased with increased shaft speed and decreased with increased lubricant flow rate. Bearing power loss increased with increased shaft speed and increased lubricant flow rate.

Parker, R. J.↗

NASA NTRS1978

Design of transmission shafting

Formula considers flexure fatigue characteristics of shaft material under combined cyclic bending and static torsion stress. Formula permits selecting shaft sizes that meet common loading conditions without adding on excessive shaft material. Formula is applicable to design of rotary power or torque transmission shafting external to machine elements.

Loewenthal, S. H.↗

NASA NTRS1979

Nonsynchronous vibrations observed in a supercritical power transmission shaft

A flexible shaft is prone to a number of vibration phenomena which occur at frequencies other than synchronous with rotational speed. Nonsynchronous vibrations from several sources were observed while running a test rig designed to simulate the operation of a supercritical power transmission shaft. The test rig was run first with very light external damping and then with a higher level of external damping, for comparison. As a result, the effect of external damping on the nonsynchronous vibrations of the test rig was observed. All of these nonsynchronous vibrations were of significant amplitude. Their presence in the vibrations spectra for a supercritical power transmission shaft at various speeds in the operating range indicates that very careful attention to all of the vibration spectra should be made in any supercritical power transmission shafting. This paper presents a review of the analysis performed and a comparison with experimental data. A thorough discussion of the observed nonsynchronous whirl is also provided.

Darlow, M. S.↗

NASA NTRS1980

Balancing of a power-transmission shaft with the application of axial torque

Evaluation of power transmission shafting for high-speed balancing has shown that when axial torque is applied, the imbalance response is altered. An increase in synchronous excitation always occurs if the axial torque level is altered from the value used during balancing; this was the case even when the shaft was balanced with torque applied. The twisting of the long slender shaft produces a change in the imbalance distribution sufficient to disrupt the balanced state. This paper presents a review of the analytic development of a weighted least squares approach to influence coefficient balancing and a review of experimental results. The analytic approach takes advantage of the fact that the past testing has shown that the influence coefficients are not significantly affected by the application of axial torque. The 3.60-m (12-ft) long aluminum shaft, 7.62 cm (3 in.) in diameter was run through the first flexural critical speed at torque levels ranging from zero-torque to 903.8 N-M (8000 lb-in.) in 112.9 N-M (1000 lb-in.) increments. Good comparison was achieved between predicted and experimental results.

Zorzi, E. S.↗

NASA NTRS1983

Flexible Coupling Corrects Shaft Misalinements

Proposed flexible coupling provides nearly error free measurements of shaft rotation in presence of misalinements between shaft and position sensing transducer. Intended to be used in situations in which input or output shaft is mounted on flexible joint. Its function is to insure equal input and output angular velocities by forcing input and output shafts to remain parallel.

Mayo, R. A.↗

NASA NTRS1983

Structural dynamics studies of rotating bladed-disk assemblies coupled with flexible shaft motions

In order to analyze the dynamic behavior of the first stage compressor/fan of the 'E3' turbofan engine, a classical structural dynamics approach is employed to couple the motions of a flexible bladed disk to a rotating flexible shaft. The analysis accounts for flexible disk displacements which are transverse to the plane of rotation, and radial as well as tangential, and also accounts for rigid disk translations along, and rotations about, axes normal to the undeformed shaft axes. In the case of a wide range of E3 engine shaft flexibilities and speeds, some of the one-diametral node frequencies are shown to be affected by shaft degrees of freedom whose stiffness values are in general range of design practice. Coriolis forces are also found to significantly affect natural frequencies where strong coupling between certain modes is present.

Loewy, R. G.↗