148 



Popular Science Monthly 



fastening it to the shaft. The balance 

 wheel may be made to suit the fancy of the 

 builder. 



Before assembling the parts, a commuta- 

 tor must be made and slipped on the shaft 

 back of the standard or between the up- 

 right and end support. As it is necessary 

 to have a break in the current for a short 



1 v -g^E^ ^plpMiJ ^ 



TO 6INDINGJ I t 60 ™ IN 



TO STANDARD w 



INSIDE ENDS 

 TO OPPOSITE SOLDERED 

 BINDING POST 

 AND BRUSH 

 The parts and their assembly for the 

 construction of the universal motor 



period a part of the commutator must be 

 insulated from the shaft. This is ac- 

 complished by making a base G cut from 

 a hard fiber rod which is drilled to slip in 

 the shaft. A brass tube having an inside 

 diameter to fit on the fiber rod is filed as 

 shown at H, and when assembled it appears 

 as shown in the illustration on page 147. 



The brush-holder for making contact on 

 the commutator is constructed as shown 

 at J. The base is made of hard rubber, or 

 fiber \}/<z in. long and % in. thick. One end 

 is rounded and drilled to slip over the core 

 or lower bolt between the standard D and 

 the magnet end C. The thin brass spring 

 makes contact with the metal strips on the 

 commutator as it revolves. 



Both inside and outside ends of each coil 

 are brought down through the base in 

 rubber tubes. The inside ends of coils are 

 soldered together. One outside end is 

 connected with the iron standard D, and the 

 other outside end with a binding post. The 

 remaining binding post is connected with 

 the spring on the brush-holder. — W. E. Day. 



Rebuilding Worn-Out Dry 

 Battery Cells 



THE most difficult part of rebuilding 

 dry cells in quantity is the removal of 

 the contents, which consists of peroxide of 

 manganese and carbon powder tightly 

 compressed and covered with pitch. Strike 

 the pitch a sharp blow with a hammer to 

 break it; then dig it out with a pointed 

 tool like that of a screwdriver. Save the 

 pitch and sand in separate receptacles. 



The compressed oxide and carbon are 

 also difficult to remove. About the only 

 quick method is to use a twist drill Y% m - 

 in diameter, placed in the chuck of a lathe. 

 By pressing the zinc-cylinder of the cell 

 on the drill and boring several holes in the 

 compressed material to within 34 m - of 

 the bottom, you will break it up so that 

 all of the compound can be readily removed. 

 Save the borings and the crumbled mass. 

 If a small portion is left at the bottom it 

 may be easily removed with the aid of a 

 screwdriver. The material removed is 

 spread out to dry and any lumps found 

 are crushed. The exposure of this material 

 in a thin layer not only permits the moisture 

 to evaporate, but brings about a certain 

 amount of reoxidation of the spent 

 manganese dioxide. As soon as the ma- 

 terial has become dry it must be heated to 

 a moderate temperature — about 400 deg. F. 

 will answer, but not to a bright red, as 

 this will drive off some of the oxygen, 

 every bit of which is needed in the renewed 

 cell to act as a depolarizer. During the 

 heating, which may be readily done in a 

 stout iron pan, it must be well stirred. This 

 process will eliminate a very large part of 

 the exciting salts used in the original cell. 

 The heated material must then be spread 

 out and exposed to the air to cool. When 

 cold it is ready to be mixed with the 

 exciting salts and repacked in the original 

 zinc-cylinders. 



Almost all the cylinders may be used 

 again after being soaked with hot water 

 for about I hour or more. The soaking 

 will loosen the original paper lining and it 

 can be easily removed with a pointed tool 

 inserted between the cylinder and the 

 lining. Finally clean out the interior with 

 a stiff brush and wet sand, or with a wire 

 brush. When the cylinders are aired they 

 are ready for re-filling. Some of the 

 cylinders will be used up and unfit for use 

 again. These may be dissolved in hydro- 

 chloric acid to form a strong solution of 



