How to make electrical machines (illustrated)

I propose to describe a method of making an electrical machine of small dimensions, but capable of performing all the experiments that are likely to be required of it. Fig 1.?Back of Rubber, Showing Position of Hole. For the stand of the machine take a piece of wood (deal will do, but mahogany would be preferable) 14 inches in length, 8 inches in breadth, and ? inch in thickness. To the bottom of this fasten two more pieces of the same wood, 1¼ inches broad, 8 inches long, and ? inch in thickness at opposite ends, so that the edges are flush with the board. This forms our stand, on which we now proceed to erect the machine. Take another piece of the same wood, 7 inches long by 2½ broad, and ? inch thick and fasten it firmly by four screws at the ends to the base board at a distance of half an inch from one end of its length and in the center of its breadth. We now take two pieces of wood 14½ inches long by 2¼ inches broad and ½ inch thick, and fasten them up[Pg 4]right to the opposite sides in the center of the piece just fixed to the board. They must be fixed very firmly to it with several screws, as they have to bear a severe strain while the machine is worked. P Plate. R R R R Rubbers. Fig. 2. Diagram Showing Position of Plate and Rubbers. If the reader can dovetail the ends into the cross board they will be held much more firmly. At the top of these pieces another piece of wood, 3¼ inches square by ? inch thick, is fastened by screws into the upright pieces, so as to hold all firmly together. 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[Pg 5] 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 ? 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 ? inch thick, and square in shape, to the inside of the supports.[Pg 6] 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. We now have the means for procuring electricity, but the method of collecting it has yet to be provided. To make this a conductor must be formed by cutting a piece of wood to the shape of Fig. 3. It should be about 6 inches from end to end, and must be carefully rounded so that no projections are left on it. It must then be covered carefully with tinfoil (which can be obtained from a chemist), the tinfoil being glued down as smoothly as possible. From the end of this conductor a piece of brass rod should be fixed,[Pg 7] shaped as shown in Fig. 4. A piece about 12 inches long will be wanted. This must be bent at the ends, so that when the conductor is mounted on a stand consisting of a piece of glass rod 6½ inches high, fixed to the center of the stand (that is 5 inches from the opposite end to that at which the supports are), the glass plate revolves between two surfaces of the brass rod. Fig. 5 explains the arrangement, which is somewhat complicated to describe. The glass rod should be about 7 inches long, to allow of half an inch being inserted into a hole in the center of the conductor, which is thus supported 6½ inches high from the stand. Fig. 6.?The Machine When Finished. It now only remains to fasten several small pieces of brass[Pg 8] wire about a quarter of an inch long, filed to a point, to the sides of the rod nearest the glass plate, as shown in Fig. 6, so that the plate revolves between a double row of points, which can be done with solder, and the machine is complete. The conductor can further be improved by inserting at the opposite end a small piece of brass rod two and a half inches high, surmounted by a brass ball, which is useful in some experiments. Care must be taken that the tinfoil of the conductor overlaps the brass rod at either end, and thus forms a metallic connection. If this is not done the conductor will not become charged sufficiently. If the conductor can be made of brass it will work better still, as a metallic connection is then insured. The conductor can be fastened to the glass rod on which it is supported by ?Prout?s elastic glue,? or other cement, a hole being made in the center of the bottom of the conductor, and another in the stand of the machine for opposite ends of the glass rod. The machine having been constructed, a few words will be useful in how to work it. Warmth and dryness are, above all things, essential. If the air of the room is damp it will be nearly impossible to obtain any result. Before working, the glass plate must be thoroughly warmed, taking care not to crack it, by being placed endwise before a good fire. A silk handkerchief is a useful adjunct to the machine. The glass plate should be wiped quite free from dirt, and the glass support of the conductor must also be wiped, the handkerchief being made very hot. The rubbers must be taken off (if constructed so as to be movable, as described), and placed before the fire till quite hot. Their powers may be enormously increased by covering them with amalgam, as sold in the electrical shops, but a far better plan is to cover the cushions with tinfoil, which can be glued right round the rubbers and over the backs. This will need renewing at intervals, as the plate in turning wears it out. Now, when the rubbers are quite hot and all the glass of the machine is dry and hot (this is necessary, because, if damp, the electricity would escape without producing any effect), the rubbers are put into their proper places on each side of the glass, and on turning the handle (which will be rendered easier if the machine is firmly clamped to the table) and approaching the knuckle to the conductor, a succession of brilliant sparks will be emitted from the conductor. If this does not happen either the glass or some part of the machine is damp, or the machine is not put together quite correctly, and must be examined to find out the fault. A machine of the size described should give a spark an inch long when working properly. A great number of experiments may be performed with this machine with appar[Pg 9]atus capable of being made at home. I give a final illustration (Fig. 6) to show how the machine looks when completed.