CONSTRUCTION OF SQUIRREL CAGE ARMATURES 99 



can be employed, any of the few following constructions is quite 

 efficient. Fig. 105 shows a photograph of a very strong construc- 

 tion employed by the Lancashire Dynamo and Motor Company 

 for their squirrel cage rotors, and Fig. 106 a sectional sketch 

 through the end ring of the same construction. The end ring is 



FIG. 106. Typical methods of fastening end rings to circular Rotor Bars. 



in this case drilled with a number of holes equal to the number 

 of slots on the rotor, these holes being of rather less diameter 

 than the body of the rotor bar. The latter is turned down at its 

 end to a diameter which will just make a good fit into the holes 

 in the end ring. The holes are counter-sunk on the outside face 

 of the ring, and the ends of the bars riveted over, as indicated in 

 Fig. 106. The bars may also be sweated at their joints with the 

 end ring as a further precaution for good contact. Then after 



FIG. 107. Typical methods of fastening end rings to circular Rotor Bars. 



riveting up the bars, the rotor is mounted in a lathe and the 

 end rings faced up, giving a well-finished job, as may be seen 

 from Fig. 105, in which the riveted ends of the bars are hardly 

 discernible. This construction is excellently adapted to with- 

 standing very high temperatures, and is therefore very suitable 

 for motors which are liable to be subject to starting against a 

 heavy torque, in which cases there is a large loss in the squirrel 

 cage windings, and liability to high temperature rises at starting. 



Fig. 107 shows another method which is almost as good as the 

 previous one, and is perhaps more useful when the cross section of 

 the end rings is not very large, as will be seen from the sketch. 



