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Commercially available roller type desk pad provides an efficient and orderly manner of handling rolled paper tapes for proofreading. The fixture, which is modified to accept Flex-O-Writer or similar tapes and roll them in either direction, reduces the chance of damaging or soiling the tapes through repeated handling.
Elastohydrodynamic (EHD) film thicknesses have been measured, by means of an X-ray technique, under conditions that closely simulate the ball-race contact in advanced turbine engine thrust bearings. The experiments were conducted with a rolling-disk machine using disks which yield a contact zone similar to that in the actual bearing. Both the rolling and spinning motions of the ball relative to the race were simulated by the apparatus. Four lubricants were evaluated at temperatures to 600 F and maximum Hertz stresses to 350,000 psi. The X-ray film thickness data correlated well with observations of surface distress (or lack thereof) in full-scale bearing tests with the same lubricants under similar conditions of temperature and load. The predicted variation of film thickness with speed and viscosity as verified, although the magnitude of measured film thickness was generally one-half to one-third of predicted values. An effect of stress greater than predicted was consistently observed in the higher stress range.
The landing contact conditions for the HL-10, M2-F2/F3, and the X-24A lifting body vehicles are analyzed statistically for 81 landings. The landing contact parameters analyzed are true airspeed, peak normal acceleration at the center of gravity, roll angle, and roll velocity. Ground measurement parameters analyzed are lateral and longitudinal distance from intended touchdown, lateral distance from touchdown to full stop, and rollout distance. The results are presented in the form of histograms for frequency distributions and cumulative frequency distribution probability curves with a Pearson Type 3 curve fit for extrapolation purposes.
An early version of an external hydrogen-oxygen tank orbiter was used as a baseline vehicle to experimentally evaluate: (1) nose shape and canopy effects on longitudinal, lateral, and directional stability and trim, and (2) yaw due to aerodynamic roll control at hypersonic speeds. Nose alterations were examined since that part of the vehicle may be subject to modifications because of internal packaging requirements, alleviation of potential high heating areas, and/or possible improvements in aerodynamic stability and control. There was also some concern about the effect of the rather high profile canopy on the aerodynamics; therefore its removal was examined. In addition, roll-yaw coupling was investigated because of its impact on the RCS fuel requirements for entry maneuvers.
The longitudinal, directional, and lateral static stability and control characteristics of a delta lifting body and a delta-wing body were obtained at a Mach number of 20 in helium for operational Reynolds numbers over an angle-of-attack range of -4 deg to 55 deg. The aerodynamic characteristics of the wing body were then evaluated in an entry study to examine the effects of vehicle performance on the aerothermodynamic parameters associated with constant and variable angle-of-attack modes for a 1500-n. mi. cross range. The experimental results indicated that the vehicles were stable, except for neutral directional stability for the wing-body shape, and could be trimmed over the operational angle-of-attack range; however, the wing-body vehicle had adverse yaw due to roll control. This roll-yaw coupling was not examined for the lifting body. The trajectory analysis indicated that a 17-percent decrease in performance required little change in the constant angle-of-attack entry mode and, in turn, resulted in a small decrease in the total heat load. For the pitch-modulated entry, the performance decrease required the pitch maneuver to begin earlier during entry and to last longer in order to meet the 1500-n. mi. cross range without a major heating penalty. The performance reduction also had little effect on the maximum laminar radiation equilibrium temperature over a major portion of the lower surface of the wing-body vehicle regardless of the entry mode.
An analysis of lubrication cross flow effects under starved elastohydrodynamic conditions is presented. Starvation is defined as any operating condition such that an increase in oil available to the contact will result in an increase in film thickness. Starved EHD behavior is considered in several situations: (1) when no new oil enters the contact, and (2) when a step change in one of the rolling parameters is introduced at an equilibrium contact. Based on the fact that important oil flow within the Hertz zone is across the rolling contact direction, it is possible to formulate a simple theory which explains quantitatively some aspects of starved ball bearing behavior.
A continuous flexible body nonlinear dynamics computer program is used for simulating the spinning mode performance of a spacecraft under applied control torques. The program takes into account the continuous flexible nature of the antennas by representing deflections in terms of shape functions and integrated the spatial dependence in the formulation of the equations of motion. Comparison of RAE flight data on roll, pitch, and yaw with predictions of the computer program in the gravity gradient mode show fair to good agreement in roll and pitch and excellent agreement in the yaw angle.
A wind-tunnel investigation was conducted at Mach numbers of 2.30 and 4.63 to determine the static aerodynamic characteristics of three 60 deg half-angle cone models. Configuration 1 was obtained by raking off a symmetrical cone at a base angle of 6.15 deg, and configuration 2 and 3 were obtained by adding flaps to a symmetrical cone. The models were tested at angles of attack from about -5 deg to about 20 deg at roll angles of 0 deg to -180 deg and at a freestream Reynolds number of 1.09 x one million, based on body diameter. The results showed that all three configurations produced finite values of lift-drag ratio useful for lifting planetary entry. All three configurations exhibited increases in yawing moment and side force with roll angle; thus, the capability for lateral trajectory control is provided.
A motion simulator study was conducted to determine the effects of roll and pitch stabilization on the handling qualities and control power requirements of VTOL aircraft during hover and short-distance maneuvering flight. Three levels of stabilization complexity were compared: (1) no stabilization, (2) rate stabilization, and (3) attitude stabilization. Control sensitivities and stabilization gains were optimized prior to comparison. Results are presented to show how the optimum systems were determined and how they compared with each other at different levels of control power. Comparisons were made both in calm air and in the presence of roll disturbances. Results indicate the attitude-stabilized system provides the best handling qualities for the least amount of control power.
For a reentry glider, approximate solutions are found in closed form for the problem of maximizing a function of the terminal velocity, altitude, flight-path angle and heading angle subject to, at most, three terminal nonlinear constraints. The results given here extend the previous results in two important ways: (1) the second-order approximation of the entry dynamics of Loh is used instead of the first-order approximation of Allen and Eggers. This approximation is found to compare extremely well with an exact numerical optimal path. (2) A three-dimensional optimization problem is solved which includes Loh's second-order approximation where the roll angle as well as the lift coefficient are determined subject to constraints which include the terminal heading angle. Furthermore, closed-form solutions can also be obtained subject to in-flight constraints on the lift coefficient and roll angle.
The series-hybrid bearing couples a fluid-film bearing with a rolling-element bearing such that the rolling-element bearing inner race runs at a fraction of shaft speed. A series-hybrid bearing was analyzed and experiments were run at thrust loads from 100 to 300 lb and speeds from 4000 to 30,000 rpm. Agreement between theoretical and experimental speed sharing was good. The lowest speed ratio (ratio of ball bearing inner-race speed to shaft speed) obtained was 0.67. This corresponds to an approximate reduction in DN value of 1/3. For a ball bearing in a 3 million DN application, fatigue life would theoretically be improved by a factor as great as 8.
The effect of G loading on the magnitude of ocular counterrolling at various angles of tilt up to 63 deg. was measured on normal subjects and compared with the effect on persons with severe or complete loss of vestibular function. The group of six normal subjects manifested a compensatory eye roll which increased as a direct and essentially linear function of the component of the gravitoinertial force acting laterally on the subject. This increase in response was not observed in the five deaf subjects with severe or complete bilateral loss of their vestibular organs. These findings confirmed similar results found by other authors using other measuring techniques which show that the reflex eye movement is dependent on and limited to the magnitude of the gravitoinertial stimulus (within the range used) when the otolithocular system is functioning normally. However when this function is severely impaired or lost, the magnitude of the compensatory eye roll is limited to that manifested at 1 G and possibly to nonotolithic contributions. These findings offer means for differentiation between otolithic-defective and ?normal' persons who exhibit little counterrolling.
Unalloyed chromium and chromium containing approximately 3 wt % ThO2 were prepared from powder produced by a chemical vapor deposition process. When rolled to sheet and tested in tension, it was found that the thoriated material had a lower ductile-to-brittle transition temperature (DBTT) than unalloyed chromium. This ductilizing was evident both in the as-rolled condition and after the materials had been annealed for 1 hour at 1200 C. The improved ductility in thoriated chromium may be associated with several possible mechanisms: (1) particles may disperse slip, such that critical stress or strain concentrations for crack nucleation are more difficult to achieve; (2) particles may act as dislocation sources, thus providing mobile dislocations in this normally source-poor material, in a manner similar to prestraining; and (3) particles in grain boundaries may help to transmit slip across the boundaries, thus relieving stress concentrations and inhibiting crack nucleation.
Primary recrystallization in TD-nickel 1 in. bar has previously been regarded as the process by which the initial fine grain structure is converted to a coarse grain size (increases in grain size by 500 times) under suitable deformation and annealing conditions. This process is dependent on deformation mode. While it occurs readily after rolling transverse to the bar axis and annealing (800 C), it is completely inhibited by longitudinal rolling and swaging deformations, even for very high (1320 C) annealing temperatures. A transmission electron microscopy examination of deformation and annealing substructures indicates that primary recrystallization in TD-nickel 1 in. bar actually occurs on the sub-light optical level, to produce a grain structure similar in size to the initial fine grained state.
Damaged tapes can now be repaired at home as long as damage does not extend to layer-to-layer adhesion within tape roll. Splice repaired section into good roll or cassette for copying. Every effort should be made to complete copying on first run, because fidelity in repaired section deteriorates with each repetition.
Analytical procedures and design data for predicting the lateral-directional static and dynamic stability and control characteristics of light, twin engine, propeller driven airplanes for propeller-off and power-on conditions are reported. Although the consideration of power effects is limited to twin engine airplanes, the propeller-off considerations are applicable to single engine airplanes as well. The procedures are applied to a twin engine, propeller driven, semi-low-wing airplane in the clean configuration through the linear lift range. The calculated derivative characteristics are compared with wind tunnel and flight data. Included in the calculated characteristics are the spiral mode, roll mode, and Dutch roll mode over the speed range of the airplane.
The important aspects of elastohydrodynamic lubrication, with a single, one-dimensional asperity, have been found by solving numerically the coupled transient Reynolds equation and the elasticity equation. Even though the assumption of a single asperity is highly ideal, this study sheds some light on the effect of surface roughness on elastohydrodynamic lubrication. The results show that the film pressure tends to increase more than the steady state pressure, and in particular, the increase in pressure reaches a maximum as the asperity approaches the inlet of the contact region. The asperity height and the pressure increase above the steady state pressure are closely related to each other; the higher the asperity height, the larger the pressure increase. In the pure rolling case, it has been found that a local pressure peak is not developed. However, in the cases of sliding and rolling, a small, local pressure peak is developed on the pressure profile when the asperity moves into the contact region. In general, the overall film thickness profile increases with increasing asperity height, but is not significantly affected by the asperity width. Moreover, the slope of the overall film thickness profile for the transient cases is much greater than the steady state profile, which is approximately constant across the contact width. The increase in the center film thickness also depends upon the width and height of the asperity.
Revisions which have been made to previous V/STOL handling qualities requirments based on criteria are discussed. A discussion of the pilot's desire for a particular characteristic is given. In addition, data and reference material are provided to back up the proposed criteria to permit the user to understand the limitations of the data on which the criteria are based. A review is included of several controversial areas including pitch control sensitivity, static longitudinal stability, roll control power, roll-yaw cross coupling, and vertical flight path control.