UNIPOLAR GENERATORS.

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In order to form a frame witli two fields of force, a support,a, is cast with two pole pieces b b' integral with it. To this arejoined by bolts e a casting d, with two similar and correspondingpole pieces c c'. The pole pieces b b' are wound and connectedto produce a field of force of given polarity, and the polepieces c c' are wound so as to produce a field of opposite po-larity. The driving shafts f g pass through the poles and arejournaled in insulating bearings in the casting a d, as shown.

h k are the discs or generating conductors. They are com-posed of copper, brass, or iron and are keyed or secured to their re-spective shafts. They are provided with broad peripheral flanges■i. It is of course obvious that the discs may be insulated from theirshafts, if so desired. A flexible metallic belt n is passed over theflanges of the two discs, and, if desired, maybe used to drive oneof the discs. It is better, however, to use this belt merely as aconductor, and for this purpose sheet steel, copper, or other suit-able metal is used. Each shaft is provided with a driving pulleym, by which power is imparted from a driving shaft.

n n are the terminals. For the sake of clearness they are shownas provided with springs p, that bear upon the ends of the shafts.This machine, if self-exciting, would have copper bands aroundits poles; or conductors of any kind—such as wires shown inthe drawings—may be used.

It is thought appropriate by the compiler to append here somenotes on unipolar dynamos, written by Mr. Tesla, on a recent oc-casion.

NOTES ON A UNIPOLAR DYNAMO . 1

It is characteristic of fundamental discoveries, of great achieve-ments of intellect, that they retain an undiminislied power uponthe imagination of the thinker. The memorable experiment ofFaraday with a disc rotating between the two poles of a magnet,which has borne such magnificent fruit, lias long passed intoevery-day experience ; yet there are certain features about thisembryo of the present dynamos and motors which even to-dayappear to us striking, and are worthy of the most careful study.

Consider, for instance, the case of a disc of iron or other metal

1. Article by Mr. Tesla, contributed to The Electrical Engineer , N. Y.,Sept. 2, 1891.