CHAPTER XXXIX.

Improvement in the Construction of Dynamos and Motors.

This invention of Mr. Tesla is an improvement in the con-struction of dynamo or magneto electric machines or motors,consisting in a novel form of frame and field magnet which ren-ders the machine more solid and compact as a structure, whichrequires fewer parts, and which involves less trouble and expensein its manufacture. It is applicable to generators and motorsgenerally, not only to those which have independent circuitsadapted for use in the Tesla alternating current system, but toother continuous or alternating current machines of the ordinarytype generally used.

Fig. 268 shows the machine in side elevation. Fig. 269 is avertical sectional view of the field magnets and frame and an endview of the armature; and Fig. 270 is a plan view of one ofthe parts of the frame and the armature, a portion of the latterbeing cut away.

The field magnets and frame are cast in two parts. Theseparts are identical in size and shape, and each consists of the solidplates or ends a b, from which project inwardly the cores c d andthe side bars or bridge pieces, e f. The precise shape of theseparts is largely a matter of choice—that is to say, each casting,as shown, forms an approximately rectangular frame; but it mightobviously be more or less oval, round, or square, without de-parture from the invention. It is also desirable to reduce thewidth of the side bars, e f, at the center and to so proportion theparts that when the frame is put together the spaces between thepole pieces will be practically equal to the arcs which the sur-faces of the poles occupy.

The bearings g for the armature shaft are cast in the side barse f. The field coils are either wound on the pole pieces or on aform and then slipped on over the ends of the pole pieces.The lower part or casting is secured to the base after beingfinished off. The armature k on its shaft is then mounted in