Popular Science Monthly 



613 



while the laminae are being turned. The 

 armature is now ready to receive its wind- 

 ing. Referring to Fig. 6, the method of 

 wiring can be easily understood. There 

 are two coils per slot, each having a span 

 of six slots. The winding consists of 

 twenty-two coils, each of which is composed 

 of 20 ft. of No. 29-gage enameled wire. 

 Now measure eleven 40-ft. lengths of wire 

 and in the middle of each twist a loop 

 about 1 in. long. Before beginning to 

 wind the armature the slots must be lined 

 with empire cloth. Cut from the cloth 

 eleven strips 1% in. long and 1 in. wide 

 and line each slot, using a little glue to 

 hold them in place. 



Beginning with slot No. 1, skip to slot 

 No. 6 and wind until you come to the loop, 

 which should be brought out on the side 

 of the commutator. The next coil is wound 

 in the same manner in slots No. 2 and 

 No. 7, etc. Now to the end of the first 

 coil (not the loop) twist the beginning of 

 the second coil. It is well to tie a knot 

 in the end of each coil for identification 

 when the commutator connections are 

 made. When the winding is complete it 

 should be tested for grounds and breaks, 

 etc. This may be easily accomplished by 

 means of an incandescent lamp in series 

 and the lighting circuit. If the coils pass 

 the test, strips of fiber 1/16 in. thick, 5/32 in. 

 wide, and 1^2 m - l° n g should be inserted 

 in the slots above the wire to prevent the 

 wire from being thrown out by centrifugal 

 force. Now give the armature two coats 

 of insulating varnish and set aside to dry. 



We will now need a commutator. The 

 writer has found by experience that this 

 had best be purchased. It may be ob- 

 tained from an electrical repair or supply 

 shop for a small sum. It should have 22 

 segments and be of the dimensions given 

 in Fig. 5 and fit snugly on the shaft. To 

 connect the armature coils with the com- 

 mutator proceed as follows: With a fine- 

 toothed hack saw cut a nick about 1/16 in. 

 deep in the end of each commutator bar 

 on the side nearest the coils. Now solder 

 the loops to alternate bars, keeping them 

 in their proper order. Be sure to use a 

 non-corrosive soldering flux. One element 

 of the winding is in heavy lines, Fig. 6, 

 clearly showing the proper connection of 

 the loop to the commutator segment be- 

 tween the bars connected with the begin- 

 ning and end of the coil. When the 

 connections are complete, center the arma- 

 ture in a lathe and take a very light cut 



off the commutator, removing the super- 

 fluous solder. On the opposite end of the 

 shaft is a brass thrust sleeve, which should 

 be a snug fit and be pressed on the shaft. 



The top bearing and brush holder are 

 shown in Fig. 7. The bearings are turned 

 from a piece of brass or phosphor bronze 

 rod. Both bearings are of the same dimen- 

 sions. The brushes are of J^-in. square 

 carbon, held in two pieces of square brass 

 tubing. The tubing is sweated to an 

 8-32 brass screw 1 in. long and set at 

 such an angle that the brush is at right 

 angles to the commutator. Each brush 

 holder is insulated from the bearing 

 bracket by two fiber washers, one on each 

 side of the bracket as shown in Fig. 7. 

 Now clamp the bearing bracket, field 

 laminae, and hard wood ring, Fig. 8, 

 rigidly together by means of the two }i-in. 

 bolts, which should be cut off to 2% in. 



The lower bearing is to be set in the 

 center of the top of the fan case and 

 secured by means of two small brass 

 screws. A small brass oil tube about 1 3^ in. 

 long is soldered to the oil hole in the 

 bearing and brought out through a hole 

 in the hardwood ring. On the underside 

 of the bearing is a dust cap, which consists 

 of a felt washer 1 in. in diameter covered 

 by a cap about 1% in. in diameter. The 

 top of a small paper fastener will, serve 

 the purpose well. The dust cap is on the 

 underside of the top of the fan case. 

 The connections are shown in Fig. 9. 



The motor is now complete and should 

 be tested out. If it runs in an anti-clock- 

 wise direction the field leads must be re- 

 versed so that the armature will rotate 

 in a clockwise direction. 



( To be continued) 



Connecting a Spotlight in an 

 Automobile Dynamo Circuit 



A SPOTLIGHT was wanted on an auto- 

 mobile in which the lights were on a 

 series circuit. As the spotlight was only 

 to be used occasionally the method of 

 wiring was as follows: A single switch 

 was mounted on the dash and a wire 

 connected with it from the left hand termi- 

 nal on the back of the ammeter. Another 

 wire from the switch was connected with 

 the spot lamp and grounded to the other 

 terminal of the spot lamp. If a spot lamp 

 is procured with a switch on it, it is only 

 necessary to connect a wire from the am- 

 meter to the lamp and ground the lamp. 



