128 



ARMATURE CONSTRUCTION 



tightened up by means of a pair of lock-nuts on the sleeve, or on 



the shaft direct. 



After the commutator has been assembled in this way, it is 



ready for machining on the outside ; the steel rings as well as the 



segments being turned all over. For high speed commutators, 



the sections for the segments shown in Figs. 149 and 150 have 



been employed, with a view 

 to further security of the seg- 

 ments against the radial forces. 

 The construction shown in 

 Fig. 149 is used by the Brush 

 Electric Engineering Company, 

 and the construction shown in 

 Fig. 150 is the invention of 

 James Burke. It will be seen 

 that the adjacent segments lock 

 Seg ?ouwors. r Hi8 '" Spee on each other along their whole 



length : the segments in each 



case would be cut to the required lengths from bars rolled or 



drawn to the required section. 



Commutator bushes or spiders are generally of cast iron, as are 



also the V clamping rings, except in large commutators, where 



steel is usually employed. 



In very small commutators the bush and end V-rings are often 



of brass, the end ring being tightened on to the brush by a screwed 



collar, instead of being drawn up by bolts as in larger sizes. 



FIG. 149. 



FIG. 150. 



