Page:Popular Science Monthly Volume 92.djvu/964

 948

��Popular Science Monthly

��Durable Terminals for Electrical Conductor Cords

THE terminals of flexible conductor cords often become frayed with use, a condition which results in poor con- nections and short circuits. A good terminal is made as follows: Peel back the insulation on the cord until a clean surface is obtained; then cut it off squarely and bend the end into a symmet- rical loop. Dip the loop first into solder- ing flux and then into molten solder, holding it until the solder "takes." This forms a solid terminal which can be screwed down tight without injury and will prove satisfactory. — Thos. A. Reynolds.

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�� ��Shocking Device That Works on the Commercial Current

AN electrical shocking device which l\. gives an even, soothing effect to the nerves is preferable to those which pro- duce slow, intermittent discharges. An apparatus for producing the soothing current is quite easily made. The source of current is an 110 volt A.C. which is reduced by resistance. The main source of resistance is the weak solution of salt and water in the two upright glass tubes. The electric light bulb is of 25 watt power and is used to judge the strength of the current and also serves to JW jJW reduce it. The current can T| nn be regulated by means of the two hat-pins which

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��Resistance in two tubes to reduce alter- nating current for a shocking machine

project through the stoppers of the tubes. One set of binding posts is for the main circuit, the other is used for the trans- mission of the current into the body. A set of handles made from the carbons of old dry cells are used for hand-grips.

To regulate the shocker, see that the switch, shown in the center of the illus- tration, is turned off. Then short-circuit the hand-grips and turn on the switch

���Push down the hat-pins in the tubes until the wires in the bulb are reddened. Note the amount of water that is between the connection points of each tube. Add the two amounts and increase the distance between them about 8 in, A very low current should be flowing through the apparatus and it is now quite safe to grip the handles. The current can now be varied to suit. — John C. Jack.

��Locating and Repairing Short- Circuited Armature Coils

1^0 locate a short-circuited armature coil, pass a current from a battery of dry cells, or a storage battery, through the armature, using the brushes of the machine for terminals. Using a low- reading voltmeter, touch its lead wires to one pair after another of the adjacent commutator segments. A zero deflection of the voltmeter needle indicates a short- circuited armature coil.

It will be seen, at periodic intervals in passing around the commutator, that the meter deflection reverses, and that just preceding this transition point the value is less than normal deflection. This merely indicates the passage from one pole to another on the winding. Thus, for instance, on a four-pole armature, there will occur four such reversals. Switching of the voltmeter leads will cause the meter to register in the right direction.

If a "short" is found, clean out the spaces between commutator segments, to be sure that no mental dust is responsible for the trouble. If this trial fails, care- fully lift out the coil connected to the bars to which the short-circuit was traced, and repair any insulation breaks.

If a winding is broken, the break may be located by connecting a battery through an ammeter to two metal strips, held apart by a piece of wood, at such a distance that they will touch adjacent bars on the commutator. Holding this device against the commutator surfaces turn the armature slowly by hand. A reduced or zero deflection of the meter indicates a broken or open-circuited winding. The only thing to do in this case, is to lift out the damaged coil, solder the ends together, re-insulate the break, and place the wire back in its proper slots on the armature. -Peter J. M. Clute.

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