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. 



9 





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 



:!^i. 



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. 



