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Functioning of Reduction Gears on Airplane Engines

Description: "In undertaking to analyze the functioning conditions of a reduction gear on an aviation engine, we will consider an ordinary twelve-cylinder V-engine. The reduction gear employed consists either of a pair of spur gears, one of which is integral with the engine shaft and the other with the propeller shaft, or of a planetary system of gears" (p. 1).
Date: March 1926
Creator: Matteucci, Raffaelli
Partner: UNT Libraries Government Documents Department

The Shock-Absorbed System of the Airplane Landing Gear

Description: "A discussion is given of the behavior of the shock-absorbing system, consisting of elastic struts and tires, under landing, take-off, and taxying conditions, and a general formula derived for obtaining the minimum stroke required to satisfy the conditions imposed on the landing gear. Finally, the operation of some typical shock-absorbing systems are examined and the necessity brought out for taking into account, in dynamic landing-gear tests, the effect of the wing lift at the instant of contact with the ground" (p. 1).
Date: March 1940
Creator: Callerio, Pietro
Partner: UNT Libraries Government Documents Department

Statistical measurements of contact conditions of 478 transport-airplane landings during routine daytime operations

Description: Statistical measurements of contact conditions have been obtained, by means of a special photographic technique, of 478 landings of present-day transport airplanes made during routine daylight operations in clear air at the Washington National Airport. From the measurements, sinking speeds, rolling velocities, bank angles, and horizontal speeds at the instant before contact have been evaluated and a limited statistical analysis of the results has been made and is reported in this report.
Date: 1955
Creator: Silsby, Norman S.
Partner: UNT Libraries Government Documents Department

Comparison of landing-impact velocities of first and second wheel to contact from statistical measurements of transport airplane landings

Description: Report presenting a statistical analysis of vertical velocities at second wheel to touch made from photographs of 353 landings of transport airplanes at Washington National Airport. Results regarding gusts, rolling direction, and number of engines are provided.
Date: February 1956
Creator: Harrin, Eziaslav N.
Partner: UNT Libraries Government Documents Department

Dynamic and flight tests on rubber-cord and oleo-rubber-disk landing gears for an F6C-4 airplane

Description: The investigation described in this report was conducted for the purpose of comparing an oleo-rubber-disk and a rubber-cord landing gear, built for use on an F6C-4 airplane. The investigation consisted of drop tests under various loading conditions and flight tests on an F6C-4 airplane. In the drop tests the total work done on each gear and the work done on each of the shock-absorbing units were determined. For both drop tests and flight tests the maximum loads and accelerations were determined. The comparative results showed that the oleo gear was slightly superior in reducing the ordinary landing shocks, that it had a greater capacity for work, and that it was very superior in the reduction of the rebound. The results further showed that for drops comparable to very severe landings, the rubber-cord gear was potentially more effective as a shock-reducing mechanism. However, due to the construction of this chassis, which limited the maximum elongation of the cords, this gear was incapable of withstanding as severe tests as the oleo gear. The action of the oleo gear was greatly inferior to the action of an ideal gear. The maximum accelerations encountered during the flight tests for severe landings were 3.64g for the rubber-cord gear and 2.27g for the oleo gear. These were less than those experienced in free drops of 7 inches on either gear.
Date: May 20, 1930
Creator: Peck, William C.
Partner: UNT Libraries Government Documents Department

Analysis of Landing-Gear Behavior

Description: From Summary: "This report presents a theoretical study of the behavior of the conventional type of oleo-pneumatic landing gear during the process of landing impact. The basic analysis is presented in a general form and treats the motions of the landing gear prior to and subsequent to the beginning of shock-strut deflection."
Date: 1953~
Creator: Milwitzky, Benjamin & Cook, Francis E.
Partner: UNT Libraries Government Documents Department

Low tire friction and cornering forces on a wet surface

Description: Report presenting an investigation to study typical tire behavior on wet runways, to determine the mechanisms by which water on runways reduced tire forces, and to determine the extent of this tire-force reduction. Under certain conditions of tire pressure, velocity, and water depth, the smooth-treaded tires stop rotating and begin to plane even without the application of brakes. Results regarding the smooth-tire friction coefficients, friction coefficients of the diamond-treaded tire, effect of 4 degrees yaw angle on friction coefficients of both tires, cornering-force coefficient characteristics of both tires, effect of weight on friction coefficients of the diamond-treaded tire, and application of the results to full-scale tires are provided.
Date: September 1958
Creator: Harrin, Eziaslav N.
Partner: UNT Libraries Government Documents Department

Evaluation of the reduced-mass method of representing wing-lift effects in free-fall drop tests of landing gears

Description: Report presenting an investigation of the validity of the reduced-mass method of representing wing-lift effects in free-fall drop tests of landing gears by means of tests of a small landing gear in the impact basin. The free-fall drop tests with full weight produced excessive values of load factor, impact period, strut stroke, mass travel, and impact energy.
Date: July 1951
Creator: Milwitzky, Benjamin & Lindquist, Dean C.
Partner: UNT Libraries Government Documents Department

Reduction of the Shimmy Tendency of Tail and Nose-Wheel Landing Gears by Installation of Specially Designed Tires

Description: Shimmy of tail and nose wheels may be eliminated by installation of dampers and use of large trail; however, this produces construction and operational disadvantages. It is more favorable to employ, instead of the customary tail-wheel tires, tires with lesser shimmy tendency. A description of the best possible form for these tires follows: furthermore, a few general concepts regarding the effects of the condition of the tire, of the type of rolling motion, and of the landing, are discussed.
Date: July 1955
Creator: Schrode, H.
Partner: UNT Libraries Government Documents Department

Routes to failure in rotating MEMS devices experiencing sliding friction

Description: Gear systems rotating on hubs have been operated to failure using Sandia`s microengine as the actuation device. Conventional failure modes such as fatigue induced fracture did not occur, indicating that the devices are mechanically extremely robust. The generic route to failure observed for all rotating devices involves sticking of structures that are in sliding contact. This sticking evidently results from microscopic changes in the sliding surfaces during operation. The rate at which these changes occur is accelerated by excessive applied forces, which originate from non-optimized designs or inappropriate drive voltages. Precursors to failure are observed, enabling further understanding of the microscopic changes that occur in the sliding surfaces that ultimately lead to failure.
Date: August 1, 1997
Creator: Miller, S.L.; LaVigne, G.; Rodgers, M.S.; Sniegowski, J.J.; Waters, J.P. & McWhorter, P.J.
Partner: UNT Libraries Government Documents Department

Update on the National Center for Gear Metrology

Description: Traceability to national or international standards is clearly required by commercial sector standards including ISO 9001:1994 (Ref. 1), ISO/IEC Guide 25 (Ref. 2), and the US equivalent of ISO/IEC Guide 25-ANSI/NCSL Z540-2-1997 (Ref. 3). In the draft replacement to ISO/IEC Guide 25-ISO 17025; measurements, not just equipment, must be traceable to SI units or reference to a natural constant. The implications of traceability to the US gear industry are significant. In order to meet the standards, either gear manufacturers must have calibrated artifacts or must establish their own traceability to SI units.
Date: September 26, 2000
Creator: Cox, B. L.
Partner: UNT Libraries Government Documents Department

Notes on Factors Affecting Geometrical Arrangement of Tricycle-Type Landing Gears

Description: The effects of the geometrical arrangement of tricycle landing gears on various characteristics of an airplane equipped with such landing gear is discussed. The characteristics discussed include directional stability, overturning tendencies, steering and ground handling, shimmy, takeoff, and porpoising. The conclusions are summarized in a table.
Date: April 1937
Creator: Wenzinger, Carl J. & Kantrowitz, A. R.
Partner: UNT Libraries Government Documents Department

Deep x-ray lithography based processing for micromechanics

Description: Deep x-ray lithography based fabrication provides a means to fabricate microactuators with useful output forces. High energy x-ray exposure provides a tool for fabrication of the next generation of precision engineered components. Device characterization, materials science, an metrology continue to pose challenges at this scale.
Date: October 1995
Creator: Christenson, T. R.
Partner: UNT Libraries Government Documents Department

Tribological issues of polysilicon surface-micromachining

Description: Polysilicon surface-micromachining is a Micro-Electro-Mechanical Systems (MEMS) manufacturing technology where the infrastructure for manufacturing silicon integrated circuits is used to fabricate micro-miniature mechanical devices. This presentation describes a multi-level mechanical polysilicon surface-micromachining technology and includes a discussion of the issues which affect device manufacture and performance. The multi-level technology was developed and is employed primarily to fabricate microactuated mechanisms. The intricate and complex motion offered by these devices is naturally accompanied by various forms of fraction and wear in addition to the classical stiction phenomena associated with micromechanical device fabrication and usage.
Date: December 1, 1997
Creator: Sniegowski, J.J.
Partner: UNT Libraries Government Documents Department

Advanced micromechanisms in a multi-level polysilicon technology

Description: Quad-level polysilicon surface micromachining technology, comprising three mechanical levels plus an electrical interconnect layer, is giving rise to a new generation of micro-electromechanical devices and assemblies. Enhanced components can not be produced through greater flexibility in fabrication and design. New levels of design complexity that include multi-level gears, single-attempt locks, and optical elements have recently been realized. Extensive utilization of the fourth layer of polysilicon differentiates these latter generation devices from their predecessors. This level of poly enables the fabrication of pin joints, linkage arms, hinges on moveable plates, and multi-level gear assemblies. The mechanical design aspects of these latest micromachines will be discussed with particular emphasis on a number of design aspects of these latest micromachines will be discussed with particular emphasis on a number of design modifications that improve the power, reliability, and smoothness of operation of the microengine. The microengine is the primary actuation mechanism that is being used to drive mirrors out of plane and rotate 1600-{mu}m diameter gears. Also discussed is the authors most advanced micromechanical system to date, a complex proof-of-concept batch-fabricated assembly that, upon transmitting the proper electrical code to a mechanical lock, permits the operation of a micro-optical shutter.
Date: August 1, 1997
Creator: Rodgers, M.S.; Sniegowski, J.J.; Miller, S.L.; Barron, C.C. & McWhorter, P.J.
Partner: UNT Libraries Government Documents Department

Reports of the measurement of elastic properties of 51XX series steels for the heat treatment distortion project

Description: We have measured the temperature dependence of the elastic constants of the 51XX series steels [gear steels] for a range of phases. At RT the normalized steel (pearlite) has the highest value of the moduli, the bainite phase the next highest, and martensite the lowest. Extrapolation of the austenite suggests that at RT austenite has lower moduli than martensite. For all the grades and phases of steels examined, the behavior of the elastic constants is similar: a curve could be drawn for each of the moduli from all the phases and all the grades would not deviate by more than {+-}4%. The normalized phase (100% pearlite in 5180) is stable up to 900 C. Bainite is stable up to 500 C. Martensite starts to change above 150 C as it tempers or strain relieves; once this is complete, the martensite moduli increase to similar values to bainite. Extrapolations are discussed. Behavior in lower carbon steels (5140, 5120) should conform to above; there is no explanation for the anomalous behavior of the quenched 5120 steel.
Date: September 1, 1997
Creator: Darling, T.; Migliori, A.; Armstrong, P.E.; Vaidya, R.; Scherer, C. & Lowe, T.
Partner: UNT Libraries Government Documents Department

MOV motor and gearbox performance under design basis loads

Description: This paper describes the results of valve testing sponsored by the US Nuclear Regulatory Commission, Office of Nuclear Regulatory Research and conducted at the Idaho National Engineering and Environmental Laboratory. The research objective was to evaluate the capabilities of specific actuator motor and gearbox assemblies under various design basis loading conditions. The testing was performed using the motor-operated valve load simulator, a test fixture that simulates the stem load profiles a valve actuator would experience when closing a valve against flow and pressure loadings. The authors tested five typical motors (four ac motors and one dc motor) with three gearbox assemblies at conditions a motor might experience in a power plant, including such off-normal conditions as operation at high temperature and reduced voltage. The authors also determined the efficiency of the actuator gearbox. The testing produced the following significant results: all five motors operated at or above their rated torque during tests at full voltage and ambient temperature; for all five motors (dc as well as ac), the actual torque loss due to voltage degradation was greater than the torque loss predicted using common methods; startup torques in locked rotor tests compared well with stall torques in dynamometer-type tests; the methods commonly used to predict torque losses due to elevated operating temperatures sometimes bounded the actual losses, but not in all cases; the greatest discrepancy involved the prediction for the dc motor; running efficiencies published by the manufacturer for actuator gearboxes were higher than the actual efficiencies determined from testing, in some instances, the published pullout efficiencies were also higher than the actual values; operation of the gearbox at elevated temperature did not affect the operating efficiency.
Date: June 1, 1998
Creator: DeWall, K.G.; Watkins, J.C. & Weidenhamer, G.H.
Partner: UNT Libraries Government Documents Department

Electrothermal actuators fabricated in four-level planarized surface-miromachined polycrystalline silicon

Description: This paper presents the results of tests performed on a variety of electrochemical microactuators and arrays of these actuators fabricated in the SUMMiT process at the U.S. Department of Energy`s Sandia National Laboratories. These results are intended to aid designers of thermally actuated mechanisms, and they apply to similar actuators made in other polysilicon MEMS processes such as the MUMPS process. Measurements include force and deflection versus input power, maximum operating frequency, effects of long term operation, and ideal actuator and array geometries for different applications` force requirements. Also, different methods of arraying these actuators together are compared. It is found that a method using rotary joints, enabled by the advanced features of the SUMMiT fabrication process, is the most efficient array design. The design and operation of a thermally actuated stepper motor is explained to illustrate a useful application of these arrays.
Date: November 1, 1997
Creator: Comtois, J.H.; Michalicek, A. & Barron, C.C.
Partner: UNT Libraries Government Documents Department