How to Make Electrical Machines / Containing Full Directions for Making Electrical Machines, Induction Coils, Dynamos, and Many Novel Toys to Be Worked by Electricity

by R. A. R. Bennett

Fig. 8.—Pillar of Commutator.

A, Brass rod. B, Screw inserted at end. C, Nut fitting screw B. D, Hole for screw to fix to base.

To make this necessary adjunct to the dynamo, take a circular bar of brass rod about ⅜ inch in diameter and an inch long. Into the middle of this solder a brass screw by drilling a hole and inserting its upper end minus the head. On this screw works a brass nut about ⅜ inch long. At the other end of the rod a hole is drilled for the insertion of another brass screw, long enough to go through the base. Another pillar precisely like this has now to be made, only ½ inch high without the nut. Now cut two pieces of sheet brass 2 inches long and ½ inch broad, sufficiently stout to act as springs and not too stout to be elastic. At one end of each cut a longitudinal hole about ¾ inch long and ⅛ inch broad; that is to say, this slit must be broad enough to slip over the top of the screws above the pillars. At the other ends of the brass springs slits of equal length, but very narrow—only about ¹⁄₂₄ inch wide—may be cut, to make the brass more “springy.” On the under side of this end of one spring and the upper side of the other, two pieces of thin sheet copper are fixed, the same breadth as the springs, and about ½ inch long. These are soldered by one end to the side of the spring, so as to act as springs themselves, their other ends being free.

All this being rather complicated, we must invoke the aid of the engraver once more. Fig. 8 gives you the method of making the pillars—A being the brass rod, B the screw and C the nut, the hole to admit screw to fasten the pillar to the base is made at the end D.

Fig. 9.—Brass Spring of Commutator.

A, Slit to fix over screw, B, in Fig. 8. The shaded part represents the copper spring, soldered at B.

Fig. 9 is the brass spring with slit, A, to slip over the screw of Fig. 8, and the copper spring soldered to one side, at the end, at the point B. Now we slip the brass spring over the screw, the screw coming through the slit, and screw down the nut C. We thus have two springs supported at the ends on pillars at a height of 1 inch and ½ inch from the base respectively. Of course, both the pillars and springs are treated alike, but in the case of the tallest the copper is on the under side, and in the other on the upper side.

Now we go back to the armature, on the axle of which you will remember that I told you to fix a small roller of wood. This is only ¾ inch long and ½ inch in diameter, and is fixed firmly to the axle so as to revolve along with the armature. This roller is soaked in melted paraffin wax for an hour or two before fixing on, or boiled in it for some time, so that it may permeate the wood. The roller can easily be turned (of boxwood, preferably) if you are possessed of a lathe, but if you have none, go to the nearest photographer (or, preferably, a dealer in photographic apparatus), and from him you can buy for 3 cents a roller long enough to cut dozens for dynamos—they are what sensitized paper is sold rolled on.