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.
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.
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.
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.
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.
Recent interest in high temperature lubrication, in particular liquid metal lubrication, has prompted an investigation of the possible use of hydromagnetic effects to increase bearing pressurization and load capacity. It has been found that by applying an external magnetic field a significant increase in pressurization can be achieved over the purely hydrodynamical bearing. Recent literature on the subject is herein reviewed and the order of magnitude of the magnetohydrodynamical effect in lubrication is discussed. Several practical arrangements for hydromagnetic bearings are briefly analyzed and evaluated. It is pointed out that a magnetic field applied transversely to the fluid film is more effective than a tangential field. In general, frictional forces are increased over the hydrodynamical bearing, but larger film thicknesses can be maintained.
Methods of freely, magnetically, suspending rotors in air, in various media, and in a vacuum are described. Rotors weighing from 10−6 lb to over 100 lb have been suspended and spun, but both larger and smaller rotors can be employed. Rotor speeds in excess of 106 rps and centrifugal fields of over 109 g have been obtained. When “coasting” freely in air at a pressure of 10−9 torr, ḟ/f ~ 10−9 sec−1, were ḟ is the loss in rotor speed per second at a speed “f.” A double magnetic suspension also will be described.
A mobile digital data acquisition system was developed both to improve accuracy and eliminate time consuming analysis of reported data from field or laboratory tests. Converting 14 channels of analogue information into a digital form, the system records the digital data on magnetic tape in a format compatible to computer processing. A brief description of the hardware and software essential to such a system is presented in this paper. Also included is a typical example of the efficiency of data reduction and the rapid analysis which may be achieved.
In oceanographic studies, by use of powered submersible research vehicles, speed is usually of slight concern, but it may be quite important to avoid noise, agitation of the surrounding water, or stirring of the ocean bottom materials. For these reasons, propulsion by means of a system that derives its thrust by action upon a very large expanse of the surrounding sea is desirable. The electromagnetic propulsion system is eminently suited for such applications. With secondary batteries of modern type, and use of a superconducting magnet, the performance, at the acceptable low speeds, of electromagnetically propelled research submarine vehicles is attractive from the range and efficiency standpoints, and gives the above mentioned advantages of silence and minimal disturbance. An example for a 15 ton submarine is given. Scaling relations are indicated to facilitate scale up or scale down from this size.