Fig. 3.—Sectional Diagram of Conductor.
The framework of the machine is now complete, and we have to provide the glass plate from which the electricity is to be produced. As we cannot make this we must apply to an electrician for it. This is 10 inches in diameter. If the maker is good at, and has appliances for, working in brass on a small scale, he can make the axle himself by taking a piece of brass rod ¼ inch in diameter and 3 inches long and fastening the glass plate in the center.
This can be done by providing two circular caps of brass one and one-half inches in diameter (the side of which next the glass must be covered with cloth to prevent cracking the glass), and fastening one by solder or otherwise, on one side of the plate, the other being arranged to screw up tightly on the other side, by having the brass turned into a screw, and the center hole of the cap made with a flange to fit it. If this is beyond the reader, he must be contented with a less elaborate axle of wood instead of brass, and two wooden caps which can be firmly fastened to the axle and glued to the opposite sides of the glass plate with Prout’s elastic glue, which can be bought from any harnessmaker.
If this is used care must be taken in warming the glass not to render the glue too soft to hold it firmly when turned by the handle. To turn the axle it must be provided with a handle of wood, in the case of the wooden axle, or, in the case of the brass one, a handle is made by turning the projecting end of the axle into a screw and fitting to it a piece of flat brass three and one-half inches by one-half inch by one-eighth inch, this latter piece having another piece of brass rod three and one-half inches long fixed to the other end, on which a wooden handle is fixed (by a cap fastened at the end of the rod) so as to turn freely.
Fig. 4.—Shape of Brass Rod to collect the Electricity.
The glass plate having been thus mounted, we must turn our attention to the rubbers which generate the electricity on the plate. To make these take four pieces of wood 3 inches by 2½ inches by ⅜ inch, and on one side of them fix pieces of thick flannel (which you can get nearly ¼ inch in thickness) of the same size, and cover these over with black silk, gluing it down lightly to the wood, so as to form a thick cushion on one side of it. These four cushions have now to be fixed so as to be firmly pressed against the glass plate while it turns. This can be done by fastening them at the backs by screws to the upright pieces supporting the plate, or by gluing four small pieces of wood about ⅛ inch thick, and square in shape, to the inside of the supports. The rubbers then have four holes cut in their backs to fit these pieces of wood, on which they slide when placed on the side of the glass, and are thus held firmly in position. Fig. 1 shows the position of the holes on the backs of the rubbers. The latter plan is the best for fastening the rubbers, as it allows them to be removed at any time for warming (a very essential point) or spreading fresh amalgam on them. Fig. 2 shows the position of the plate and rubbers when in their places.
R R Rubbers.
Fig. 5.—Sectional Diagram Showing Position of Collectors and Plate.