The author calls attention to the unreliability of the magnetic compass when used for aerial navigation and to the possible development of the gyroscopic compass for this purpose. He then explains how the drift of an airplane in flight makes it difficult to follow with accuracy a given course devoid of landmarks, unless an accurate drift indicator using the principle of the stroboscope is available. The development of such an instrument is then described, as are also means for synchronizing it with the compass. The use of the automatic synchronized instrument in flight over land is outlined, and its application to flight over water is described in considerable detail. Rules for aerial navigation over water, observation as to movement of wave crest and determination of wind velocity and direction are considered in their relation to the use of the instrument.
INDUCTION heating of a metal part is accomplished by placing the part in a magnetic field created by high-frequency, alternating current through an induction coil, thus converting electrical energy into heat and, with enough power supplied, heating the surface regions to the critical temperature in a few seconds. Although this principle is not new, Mr. Vaughn points out that it is only in recent years that the process has been used to any extent as a production method for various heat-treating operations. After mentioning some of the problems involved in using high-frequency current, the author gives examples of typical tractor and engine parts that are being successfully induction hardened in production.
To provide maximum comfort for passengers, it is claimed that cabin pressures must be maintained within very-narrow limits. The various steps by which a system was developed to accomplish such control is discussed and illustrated by photographs and diagrams. The author believes that the final result of the research and development program is a system which will not only provide the necessary control, but will do so with a degree of reliability unknown in earlier systems, with a minimum of maintenance and extremely simple in operation. Two production systems are described in detail with a final explanation of how a transistorized pre-amplifier and magnetic amplifier is used.
RESULTS of an Armour Research Foundation program, promoted by ATA interest in truck exhaust noise problems, are described here. It is shown that exhaust-noise measurements can be made using an octave band analyzer, and values thus obtained agree quite well with listening tests. Highway truck noises are recorded on magnetic tape, which is then fed into the analyzer at leisure. Test-stand measurements, however, give good results only when the exhaust is the main source of truck noise.
FOREWORD The majority of thunderstorm electrical discharges involving aircraft are in the “Upper-reaches” of a lightning discharge channel where currents tend to be lower than for the lightning we know near the ground: Therefore, the term “Static-discharge”, which many pilots use when the discharge does not seem violent enough to warrant the term “Lightning” may logically be used as a more general term covering all thunderstorm electrical discharges. In using the term “static-discharge” it is important to avoid confusion with precipitation charging and the associated minute currents normally discharged through “wick-dischargers” to prevent radio interference. It must be emphasized that discharges in the case of precipitation-static involve currents of fractional amperage insufficient to produce any of pitting or burning effects for which protection might be needed.
INDUCTION heating is a process or method by which metal parts are heated by simply placing them in an alternating magnetic field. The action is that of the transformer, whereby electrical energy is transferred or passed over to another isolated electric or secondary circuit by means of the magnetic field; thus, no physical attachments or electrical contacts are necessary to have electrical currents, which are dissipated as heat, flow in the parts to be processed. The strength and frequency of the alternating magnetic field can be selected to produce any desired rate of heating and ultimate temperature. A circuit can be set up to dry lacquer at 160 deg. fahr. on thin sheet-metal parts or to melt in record time immense steel ingots. Induction heating is now commercially applied in automotive production to many processes, and these are specified.
MAGNAFLUX testing has become an important adjunct in connection with the inspection of aircraft parts fabricated from magnetic materials. The method is very sensitive and may indicate not only defects which seriously weaken the part, but also non-injurious imperfections. The author has classified the several defects indicated by magnaflux which have been found in the routine inspection and examination of a large number of parts which have been in service in engines, airplanes, and accessories operated by the U. S. Army Air Corps.
The McCulloch welder’s weight of 55 lb and output of 170 amp result in hand portability with adequate power for most welding applications. The key elements of its design are a light metal, high-speed, two-stroke cycle gasoline engine and a high frequency, capacitor compensated, inductor alternator. Features of the single-cylinder engine, the power increasing muffler, and the double diaphragm “pressure” carburetor are described, and the effects of unit weight, rotary inertia, and cylinder compression ratio on cranking effort are noted. In addition, the inductor alternator’s magnetic and electrical circuits are explained and the output characteristics given.
High-temperature electrical materials presently available for application in the 500-1600 F range have been evaluated for advanced Rankine cycle systems and other high temperature applications. Magnetic materials for high saturation, low loss use include cobalt-iron and doubly oriented silicon-iron alloys. Nivco alloy (72w/o Co, 23w/o Ni and other alloying elements) has the highest creep resistance above 1000 F of all magnetic materials suitable for mechanically stressed applications. Inorganic insulations for magnet wire, flexible sheet, interlaminar coatings, potting compounds, and rigid or molded parts are discussed. Inconel-clad silver and clad and unclad dispersion strengthened copper electrical conductors offer the best performance in stressed and unstressed applications respectively.
A general discussion of the evolution of permanent magnet materials and their effect on the design of d-c motors is presented. Permanent magnet motor characteristics are compared to those of other types of motors and the advantages and disadvantages of each type are covered. The more important design considerations are discussed, and the actual design of a typical permanent magnet motor for an automotive window lift is examined in detail.
Basic information on gasolines which cause damaging induction system (intake port and valve) deposits in ground vehicle engines was obtained. Several fuels of known depositing tendencies were charcoal filtered and the absorbant extracted with chloroform and acetone. The adsorbant was then eluted with isopropyl alcohol in a silica gel column to obtain a concentrate. This concentrate was further subdivided in a column of magnesium silicate by a repeated elution sequence using n-pentane and methanol, obtaining a 97% all inclusive induction system deposit extract -- representing about 10-500 ppm of the fuel. The results were confirmed by both bench and engine tests. An identification of these induction system deposit precursors was made by means of elemental, nuclear magnetic resonance, infrared and mass spectral analyses. The induction system deposit precursors were found to consist primarily of long chain oxygen and nitrogen containing compounds such as amides and carboxylic acids.
Magnetic pulse metal forming results from kinetic energy imparted to a metallic workpiece by a magnetic pulse. Control and measurement of this energy is purely electrical. Once the parameters are established for a particular magnetic pulse forming application, the process can be monitored by a single voltage measurement. Because of general freedom from mechanical inertia, high repetition rates (for example, 16 operations per second) and microsecond capabilities can be built into the machines. Measurements of pressure on the workpiece can be derived directly from the value of the magnetic field at the surface of the metal by relatively simple equipment.