WINDING OF CONTINUOUS-CURRENT ARMATURES 267 



and bottom bars, and in some cases will not require supporting 



flanges underneath the overhanging windings at the ends. In 



all three methods the copper is first 



cut in lengths, and, if there is more 



than one bar in a slot, these bars are 



all bent together at one operation, the 



back end loop being bent first. Then 



the copper is annealed at this point, 



and the bars are shaped on the former, 



after which the bars are marked in 



consecutive order so that when these 



bars are insulated they may be re- 

 assembled in bundles corresponding to 



the way in which they were bent. 



The bars may then be washed in a 



bath of benzine, and dipped in an in- 

 sulating varnish thinned down to about 



0*83 specific gravity. These bars are 



then placed in a baking oven and well 



baked. The object of this coating of 



varnish is to protect the copper from 



verdigris, as well as to give it a good 



insulating film. Naturally the copper 



edges must be well rounded, in order to 



obtain the best results, before they are coated with the varnish. 



The bars are then ready to be insulated. 



Frequently the practice is adopted of taping the ends, leaving 

 the slot portion bare, as in Fig. 315. 

 The slot portion may then be insulated 

 by a strip of mica cloth or mica paper, 

 cut as wide as the slot portion is long, 

 and interwoven so that one layer of 

 this insulating material separates the 

 bars, as in Fig. 316. 1 The surplus end 

 of the insulation is then wrapped 

 around the assembled bars, making 

 two or more layers, according to the 

 voltage of the machine and insulating 



space available in the armature slot. A layer of tape is then 



put on top of this insulation, and the completed bars are dipped 



1 The thickness of the vertical insulation between the conductors is 

 exaggerated in Fig. 316. 



* " 



Parts 



FIG. 316. Insulation of Group 

 of Bare Conductors. 



