ropular iaciencc Montnhj 



47L^ 



COWWUTATOR 



The machine is now ready to be fitted 

 with brushes. The brush system de- 

 scribed as follows, like the armature, can 

 be used on any type of machine — series, 

 shunt or compound. The brushes are 

 made from very thin sheet copper bent as 

 shown in the sketch. They are mounted 

 on a small fiber or hard wood block of the 

 dimensions shown. Small brass machine 

 screws hold them in place and also provide 

 means for connections. Care should be 

 taken in adjusting the brushes so they 

 bear flatly upon the commutator surface 

 which reduces the 

 resistance of the 

 sliding contact to a 

 minimum. 



After mounting 

 the apparatus on a 

 suitable base, the 

 connections of the 

 various parts are 

 made as illustrated. 

 It will be seen that 

 the field winding is 

 connected in a se- 

 ries with the arma- 

 ture, which fact 

 gives the dynamo 

 its name. An emp- 

 ty thread spool is 

 forced on the end of 

 the shaft to serve 

 as a driving pul- 

 ley. The dynamo 



may be driven by a water motor, gas 

 engine or other means. If the ex- 

 perimenter has alternating lighting cur- 

 rent available, a small 110 volt motor 

 may be used to drive the generator. In 

 this case, it makes an ideal motor gen- 

 erator for use on the experimenter's table 

 for electrolysis, etc. A series wound 

 dynamo, however, should never be em- 

 ployed to charge a storage battery as it is 

 very likely to change its polarity and 

 injure the cell. 



To build a shunt wound dynamo, it is 

 necessary to make a different field 

 winding. The field winding of a shunt 

 wound dynamo should have a much 

 higher resistance than the armature 

 winding so that it will have suffi- 

 cient magnetizing power without draw- 

 ing too much current. In this case, No. 

 30 single cotton covered copper wire 

 should be used for the field coils. About 



SHUNT COMPOUND . 



COPPER SE&MtNTS BRASS . 



RIVETED TO FIBER DISK SCREWS"; 



METHOD OF WINDING ARMATURt 

 FI& 1 



Wiring diagrams for the different fields; 

 also the method of winding the armature 



1 2 lb. is the amount needed. It is wound 

 on in the same way, the only difference 

 being that it is connected in shunt to the 

 armature instead of in series with it. 

 The method of connecting a shunt wound 

 dynamo is shown in the sketch. This 

 machine is ideal for charging storage 

 batteries. 



Compound wound dynamos are pro- 

 vided with two separate field windings. 

 One winding, which is of fine wire, is con- 

 nected in shunt across the brushes, while 

 the other winding, which is of larger wire, 

 is connected in se- 

 ries with the arma- 

 ture winding. The 

 connections are 

 plainly shown in 

 the sketch. The 

 fine wire should be 

 wound on first and 

 consists of Y^ lb. 

 of No. 30 single 

 cotton covered wire 

 divided equally be- 

 tween the two poles. 

 After being given a 

 coat of shellac, a 

 layer of paper is 

 placed over the 

 winding. The sec- 

 ond T^inding, which 

 consists of ^ lb. of 

 No. 18 single cotton 

 covered wire, is then 

 wound over the first After being shel- 

 lacked, it is covered with friction tape and 

 the machine is assembled. 



A very good universal generator can be 

 made by winding each one of the three 

 magnets furnished with the magneto. 

 One can be wound for a series dynamo, 

 one for shunt and one for compound. 

 The experimenter will then have a ma- 

 chine of any type by using the correspond- 

 ing magnet over the armature. It is not 

 necessary to arrange any mechanical con- 

 trivance to hold the different magnets in 

 place as they generally fit tightly over the 

 sheet iron frame that covers the armature. 

 It will be necessary, of course, to use the 

 proper connections for each different 

 magnet. 



These small generators, if properly 

 constructed, should deliver from 20 to 30 

 watts of energy. This will depend largely 

 upon the strength of the magnets. 



V.ETMOO Of MTt. 

 BRUSHES 



