Tape Tension Research Articles

磁気ヘッドの摩耗のエンベロープに及ぼす影響

Reproduced envelope of VCR head output will vary depending on the combination of magnetic head contour shape and tape stiffness, with low stiffness tapes in particular having damped envelope. Head contour was measured by the interference ring method with spline interpolation. The change of the head contour through wear has various patterns according to the head construction. Head shape dependence and tape tension dependence of reproduced envelopes were studied in connection with the tape stiffness. Reproduced envelope decreases with the increase of the radius of curvature for transverse direction of the head surface. Envelope improvement will be obtained by choosing the best position of gap on the head contour for each head construction, and by decrease of tape tension and head protrusion.

Tape dynamics in a high-speed helical recorder

Tape dynamics in a helical recorder were measured at head speeds up to 75 m/s. The onset and amplitude of transverse waves are studied as a function of head velocity, tape tension, and tape thickness. Wave patterns are plotted over a range of these parameters. The tape deflection directly behind the head, in front of the head, and at the tape edge is investigated and compared to theoretical predictions of tape deflections reported in the literature. For the range of parameters studied, damping of tape dynamics was increased in cases with lower head velocity, higher tape tension, and thinner tape. Chevron-shaped wave patterns were found to wrap around the head. The general deflection of the waves, particularly the short waves preceding the head and the dip trailing the head, correlate well with predictions existing in the literature. However, the chevron-shaped wave pattern that extends to the tape edges at high head speeds has not been predicted in the literature. The present measurements indicate that free tape-edge boundary conditions should be assumed in a high-speed model, and that the tape behavior in the vicinity of the head is a strong function of head speed, tape tension, and tape thickness. >

A study of geometrical a changes in a head surface caused by sliding wear against a tape. (1st Report, Experimental study).

The changes in head geometry caused by head-and-tape contact are investigated experimentally and analytically. Dummy heads made of copper and lapping tapes are used for wear tests in which the dummy head slides on the lapping tape travelling under constant tape tension and sliding velocities, leading to a constant contact force. An optical interference microscope and a surface profilometer are used to examined the head geometries, and an optical microscope is used to examine the head-and-tape contact area. The tape deformation is calculated using the finite element method under a condition of uniform pressure applied to the tape. From these investigations, the following is clarified. At the early stage of wear, the head wears selectively where the contact force is high. The head reaches specific geometries in spite of the difference in initial geometries of heads. This means that the contact pressure between the head and tape becomes uniform in accordance with the progress of wear. The head geometry in a steady state of wear is very close to the tape deformation calculated under uniform pressure. This result shows the occurrence of uniform wear, and the wear volume V calculated by V = cPvt, where c is the specific wear rate, P is the contact force, ν is the sliding velocity and t is the sliding period.

Contact Analysis Between Magnetic Heads and Magnetic Tapes of Video Cassette Recorders : (Analysis with Infinite-Width Heads)

An analytical method of contact status between magnetic heads and magnetic tapes as well as the results of such an analysis are explained. Tape deflection is obtained in the form of the influence coefficient "Aij" created as a point "i" when a unit load is applied to a point "j". The contact status is clarified by adopting a theory of increments in which calculations are successively made while causing a head and tape to gradually make contact with each other. The contact length upon the head differs depending on the values of the head radius, tape tension, tape rigidity and degree of protrusion of the head. The actual measurements were achieved by utilizing the interference fringe pattern created between the head and the transparent tape. The experimental results are in close accord with the numerical results.

Overview of challenger space shuttle tape-data recovery study

Degraded magnetic tapes recovered from the Challenger space shuttle, after being immersed in seawater for six weeks, could not be unwound without damaging the recording surface. The recording side had become cemented to the backside. During unwinding, the fragments from the recording side, mostly at tape edges, transferred to the backside, and remained firmly adherent. Magnesium hydroxide was found to be the substance adhering the recording surface to the backside. It is thought Io have precipitated due to the increased concentration of magnesium ions resulting from the corrosion of the magnesium alloy flanges of the reel assembly. In addition, we found that low-molecular weight degraded magnetic-coating binder was present on large areas of the backside of the tape. Matrix experiments showed that the presence of magnesium hydroxide was primarily responsible for the interlayer adhesion. We found that magnesium salts could be removed with a treatment of 0.5 molar nitric acid, and low-molecular weight binder could be dissolved with a methanol rinse. We devised a method to chemically treat the damaged reels. We first removed the eroded magnesium hub and placed the reel on a spring-loaded plastic ring. The reel was then treated in a wash tank. The reel was treated under partial vacuum with nitric acid and methanol. As a last step, the treated reel was relubricated to replenish it with lubricant. After treatment, the reels were carefully unwound without any damage to the recording surface. The reels had to be manually unwound in a 180° peel mode at a very slow rate of about 0.15 meters per minute. The digital data from the unwound reels were recorded in analog mode for optimizing reprocessing using a commercial drive which operates under low tape tension and speed. The copied reels were then digitized by NASA. Over 90% of the data blocks from a recorder were readable and 100% of the voice data blocks were recovered.

Contact analysis between magnetic heads and magnetic tapes of video cassette recorders. 1st Report. Analysis with infinite-width heads.

Explained are the analytical method of contact status between magnetic heads and magnetic tapes, as well as the results of such analysis. The tape deformation is obtained in the form of influence coefficents Aij created at a point i when a unit load is applied to a point j. The contact status is clarified by adopting the theory of increments in which calculations are successively made while causing a head and a tape to gradually contact each other. The contact length upon the head differs depending on the values of the head radius, the tape tension, the tape rigidity and the degree of protrusion of heads. The actual measurement was achieved by utilizing the interference fringe pattern created between the head and the transparent tape. The experimental results are in close accord with numerical results.

Tension gradient measurement of magnetic tape

This paper describes a device that measures the tension distribution across the width of magnetic tape. Historically, tension variation along the length of the tape has been used to quantify data reliability, and accurate tension control with the use of vacuum column is necessary. The longitudinal tension gradient is the primary source of data error. Thick mylar and lower number of tracks per mm produce very little tension gradient across the width of the tape. Conditions due to the decrease in tape thickness, tape hub taper, alignment of the tape-device components, and high temperature and humidity of the tape environment, result in tape tension being no longer uniform across the width. A tension-measuring device was developed to aid in the understanding of the presence of tension gradient across the width of the tape and its resultant effects on uneven head wear and nonuniform data reliability. The use of this device led to improvements in tape-path component design, head wear, and data reliability.

Selectivity and Effectiveness of Pan Tension Devices for Coyote Foothold Traps

Data were collected on the numbers of coyotes (Canis latrans) and nontarget animals that stepped on standard traps and traps equipped with shear-pin, curved leaf spring, or steel tape tension devices and were captured or excluded. The modified 3N-M Victor steel foothold traps were about three times more effective than standard traps for excluding kit (Vulpes macrotis) and swift (V. velox) foxes, gray foxes (Urocyon cinereoargenteus), striped skunks (Mephitis mephitis), opossums (Didelphis virginiana), and jack rabbits (Lepus californicus). Coyote capture rates in initial field tests were lower for modified traps than standard traps when set in wet clay or alkali soils. Shear-pin and leaf spring devices were then modified and zinc-plated to reduce rusting caused by moisture and to improve trap performance. Exclusion rates (percentage of animals that stepped on pans and were excluded) in subsequent field tests for all designated nontarget animals for the wet soil test were 92, 100, 95, and 6 for shear-pin, leaf spring, steel tape, and standard traps, respectively. Coyote capture rates with the improved devices in wet areas with clay or alkali soils were 87, 92, 84, and 98% for shear-pin, leaf spring, steel tape, and standard traps, respectively. The improved devices functioned adequately for use in coyote trapping activities. J. WILDL. MANAGE. 48(3):700-708 Steel foothold traps are used for harvesting furbearers and for removing coyotes and other predators from livestock depredation areas. Private fur trappers usually attempt to capture smaller furbearers as well as coyotes, but U.S. Fish and Wildlife Service (USFWS) Animal Damage Control Program (ADC) efforts are hampered when traps set for coyotes are sprung by other animals. Because traps are an important tool in the ADC program, efforts were initiated at the Denver Wildlife Research Center (DWRC) to make trapping for depredatory coyotes more efficient and selective (Linhart et al. 1980). Trap selectivity and efficacy are major issues raised by proponents of restricting or prohibiting use of steel traps (Dixon 1930, Atkison 1956, Gipson 1975, Singer 1975, Nichols 1976, Parsons 1977, Howard 1979, Todd 1980, Schmidt 1981). T ese issues are also of concern to the

Capacitance Probe Study of Rotating-Head/Tape Interface

A modified version of the capacitance probe technique is used to investigate the head-tape interface in a rotating head configuration. The relationship between air-bearing spacinga nd contour design is studied as a function of tape tension, head protrusion, and velocity; in addition, the effect of wave dynamics on flying height is examined.

Minimax problem of determining the tape tension during winding on a compliant bobbin

The object of this report is to analyze the modes in which the tension on the inner turns drops when a tape or a thread are wound on a compliant bobbin as, for example, during processing of glass-plastic products. It is established here under what conditions one cannot possibly ensure a uniform residual tension in all turns upon completion of the winding; for this case, then, the optimum mode of tension change during winding is sought, so that the tension drop in the inner turns will be minimum.

Standard Alignment Tape Recorder for EIAJ Type I Videotape Recorder

A standard alignment tape recorder for EIAJ type I VTR (STD-VTR), which was requested by the Electronic Industries Association of Japan (EIAJ), was developed. This recorder was especially designed considering durability, reliability and accuracy in order to maintain a high level for the standard. The main parts of the tape guide portion were made of high wear-resistant ceramic. The adjustment and calibration of the characteristics were performed very carefully. One of the most important functions of the standard tape is the skew characteristic, and, therefore, the tape tension was maintained within ±1 g by a closed-loop servo system using an air column. — In connection with the development of this recorder, the characteristics of EIAJ type I VTRs on the market were evaluated. There were some characteristic differences, but no serious problem of tape interchangeability between different manufacturers with the exception of the skew characteristics. The standard alignment tape will be applied in order to realize a yet higher tape interchangeability (including skew characteristics) as well as a more easy VTR operation.

Investigation of Dynamic Taping

The preferred time for reading tape length when using dynamic taping is suggested, differing from the one previously proposed. The dynamic taping technique has been suggested as a method for eliminating catenary corrections. An experimental investigation in which the measured length and tape tension were measured as functions of time was conducted to confirm or suggest modifications to the time at which the length should be measured. An analytical method for determining the time-placement relationship of one end of the tape is presented and theoretical curves are shown for a range of amplitudes of tape oscillation. Comparison between an experimental cycle and the theoretical values resulted in good correlation in the critical regions. The tape force-time relationship depends on the observer, and the length-time relationship depends on the force, length, and cross section of the tape. However, the minimum reading of the tape appears to give a more accurate result than the reading previously proposed.

White Light Interferometry of Elastohydrodynamic Lubrication of Foil Bearings

This paper describes an experiment performed to verify the one-dimensional model of elastic foil behavior developed by Stahl, White, and Deckert. In the experiment, a loop of tape one-inch wide passes over a stationary recording head, and the air-film thickness between the head and the foil is determined using white light interferometry. Measured data for various experimental conditions are compared with the predictions of the model and also with prior foil-bearing analyses. The influence of parameters such as tape thickness, head radius, tape tension, etc. on the nature of the spacing field is demonstrated.

ビデオヘッドと磁気テープとの摩擦と摩耗 (第1報)

Experiments were made to study the contact force and frictional force between the magnetic head and the magnetic tape in a two head helical scan type VTR. Both forces were directly measured in the experiment in which the head attached to spring plates contacts with the tape under the conditions of the rest and running at 0.19 m/s. The frictional force at higher speeds was measured by means of the deceleration of disk having heads due to friction. The tension of tape running around the cylinder was also studied in VTR. The frictional force increases linearly with the increase of tape tension and height of head protruded from the cylinder and is of order of 1 g. The friction is independent upon the frictional speed over the range of 0.19 to 11 m/s. It is concluded that the frictional force is directly proportional to the contact force and the coefficient of friction takes approximately the value of 0.22 in operation of VTR. The tape tension at the tape supplying side of the cylinder in VTR is about three times that at the winding side. The increase of tension is mainly due to the friction of tape sliding on the cylinder and decreases as the protruding height of head increases.

An Automatic Skew Corrector for Helical-Scan Cassette Videotape Players

In most present-day helical-scan cassette videotape players, tape tension (and therefore tape stretch) is not controlled by a vacuum block as in quadruplex systems but by manual adjustment of the tape supply tension. If the tension is not correct, a timing error results which causes the picture to be skewed to the left or right. An effective automatic skew-correction circuit has been developed that feeds an output signal through an operational amplifier and a Darlington output stage to 2 rotary solenoid that controls tape tension. Skew error after correction is less than 0.5 μs. One type of widely used Japanese cassette player was modified with the skew corrector in less than 20 min using only screwdriver and soldering iron. When a videotape cassette player must operate unattended and when tapes come from many sources automatic skew correction is essential.

Magnetic tape recorder for long operating life in space

Magnetic tape recorders have long been used on satellites and spacecraft for onboard storage of large quantities of data. As satellites enter into commercial service, long operating life at high reliability becomes important. Also, the presently planned long-duration space flights to the outer planets require long-life tape recorders. Past satellite tape recorders have achieved a less than satisfactory performance record and the operating life of other spacecraft tape recorders has been relatively short and unpredictable. Most failures have resulted from malfunctions of the mechanical tape transport. Recent advances in electric motors and static memories have allowed the development of a new tape recorder which uses a very simple tape transport with few possible failure modes. It consists only of two brushless dc motors, two tape guides, and the recording heads. Relatively low tape tension, wide torque capability, and precise speed control facilitate design for mechanical reliability to match that of tape-recorder electronics.

A Theoretical Study of the Dynamic Behavior of Foil Bearings

The differential equations and boundary conditions for the problem of a foil bearing subjected to small variations in tape tension are developed. The numerical results show that the fluctuations of the foil are a function or the frequency parameter ω* = 2r0ωε1/3H0*/U and of the compressibility factor θ = T0/par0.

Effects of Bending Stiffness in Magnetic Tape

The elasticity of magnetic tape is an important factor in determining the shape of a tape loaded over a magnetic head Over a single apex the radius of curvature of the tape is inversely proportional to the wrap angle and to the square root of the ratio of tape tension to bending stiffness. If a constant-pressure support is assumed instead of a knife edge, the radius of curvature increases considerably. A chart is provided for use in calculating the radius of curvature under different loading conditions. Over a double apex the results are the same as for a single apex except when the distance between apexes becomes small. By increasing the radius of curvature of the head to conform to the radius of curvature of the tape, the rate of head wear can be greatly reduced.

A sensitive radiotracer technique for measuring abrasivity of magnetic recording tapes

A special magnetic tape transport system and radioactive dummy recorder heads were designed and constructed to provide a sensitive, rapid, and precise method of measuring the abrasivity of magnetic recording tapes under conditions closely approximating their use in actual instrumentation recorders. The tape contact face of the dummy-recorder head was made of neutron-activated Kovar. Two-hundred-foot samples of 0·5-in. wide instrumentation tape were tested using the same tape wrap angles, tensions, and speeds as those used in actual recorders. The amount of radioactivity transferred to the tape was used to establish the amount of Kovar worn from the head. The precision of 5-pass tests was about 4%. Virtually all of the abraded radioactive material adhered to the tape. Abrasivity was directly proportional to tape tension, but independent of tape speed. Relatively large differences in abrasivity were found, even among samples from the same reel of tape. Comparison of measurements made with radioactive heads of two different designs indicates that the test method gives relative abrasivity values applicable to actual recorder heads.