Fig. 6.—Support for Commutator End of Axle.
The dotted lines show position of holes for screws and axle. P P, Holes for screws.
To do this we shall want two supports for the axle. These are made of brass, shaped as in Figs. 5 and 6, 5 being the one at the pulley end of the axle, and 6 that at the other end. They are fastened by screws through the holes P P, into the holes H H H H in the bottom part of the side of the magnet, as previously shown in Fig. 2.
When the armature is fixed in its proper place it will appear as Fig. 7, this being a sectional diagram from above, and the top pieces of the magnet being omitted for simplicity’s sake.
Fig. 7.—Ground Plan of Magnet and Armature when put together.
M M, Magnet. P, Driving pulley. A, Armature. R, Roller of wood covered with brass. Top of magnet and springs of commutator omitted.
The brass of which the supports are made should be about ⅛ inch thick, and must, of course, be drilled in the center with a hole to admit the axle of the armature. To keep it exactly in the right place while revolving, a piece of circular brass tube, with a bore the size of the hole made to admit the armature, should be soldered to the brass supports in front of the hole; that for the pulley end of the axle should be ½ inch long. One at the other end is not necessary, but looks neater; this may be about ¼ inch long—i. e. as long as the end of the axle projecting beyond the brass support.
This much having been accomplished, we have now to consider the “commutator,” which is a piece of apparatus by which all the currents proceeding from magnet and armature are sent in one direction, and thus, instead of counteracting each other, are made available for experiments.