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

The electricity passes along the wire X, we will say, and round the magnet coils, thus turning the cores into magnets. It then goes down the other wire to H, up the brass spring, along the screw, and down by the brass support to the other wire, by which it returns to the battery. That is to say, it would do all this if the armature stood still, but, of course, when the cores become magnets they attract the armature, which instantly moves towards them; this breaks the circuit, the spring moving off the platinum point of the screw, and the armature springs back again, which makes the circuit complete and the magnet attracts it again, and so on. The object of the spring is to get a good deal of vibration, and it and the screw should be so adjusted that although the armature is close enough to the magnet to make it certain to “go off” directly it is meant to do so, yet there may be as much scope for the spring to work with elasticity as possible.

We have now completed the electrical part of the business, but a slightly necessary part of the apparatus has yet to be obtained—viz., the drum. You can easily make a drum if you like, by taking a broad piece of tin, twisting it round to form a hoop, and covering the ends with parchment strained tightly over them. However, I should certainly not do so, for there can hardly be any spot, I should think, which boasts of a toy-shop at all, where drums cannot be procured! For twenty-five cents you can get a very superior drum, just about the right size; if you like to get a bigger one and make the mechanical part bigger, you will, of course, be rewarded by more noise.

Now, suppose you have got a 25-cent toy-drum, you must proceed to take off one end. If you look at the construction of the drum you will find (at least it is the case with my own, and I have not seen any that are differently made) that by cutting one of the double strings that fasten the wood hoops at the top and bottom together, and then loosening all the other strings with your fingers, the wooden hoop at one end will come right off, if the nails fastening the ends together are taken out, and that then the inner hoop on which the parchment is stretched will also come off and leave that side of the drum open.

Now, this is simply grand for our purpose, for when we have arranged our little dodges inside the drum, we can put on all the hoops again, replace the one double string, and no one will be an atom the wiser. If you could get off the side without breaking any strings it would save the trouble of replacing any, but I am afraid this is hardly possible. However, off comes the side of our drum, and what is to be done next? Well, the “beater” must be put bodily inside the drum, just so close to the parchment side that was taken off that the wooden head of the drumstick touches it when attracted by the magnet. You can easily find the right place in actual practice by setting the beater going and finding the spot inside the drum where it kicks up the worst racket when working. It must not be too close or it will hinder the vibration, and we want the hammer to go off instanter when required. The beater is fixed to the side of the drum with its side marked Z in the figure (5) downwards. It is easily fastened there by making two holes in the wood (in the thickness of it), and two corresponding holes in the metal side of the drum, and then screwing it down in its proper place.

Two holes are to be made in the side of the drum and two ornamental bits of silk-covered flexible copper conductor let through. They can be secured by simply tying knots inside the drum, and the copper ends are now to be fastened, one to the wire X and the other to the wire K from the contact screw support. Having done all this and made sure that the beater works when the ends of the flexible cord outside the drum are connected with the battery, we seal up our drum again, and that is then concluded.

Now as to fixing it up, I think I may fairly assume that you know how to make it work by an ordinary battery and a “press.” It is only necessary to run a double wire from battery to press and from press to drum, one wire of the double conductor being fastened to the carbon end of the battery and the other to the zinc end, and the other end of one wire to one of the wires coming from the drum. The other wire coming from the drum is then joined to the bottom conductor of the press, and the upper conductor of the press is joined to the other wire of the double conductor that goes to the battery. It is all very easy to understand if you follow the course of the current and consider that it has to pass through the drum and the press when the latter is pushed down, and be stopped when it is left to spring up again.

But the more magical arrangement can be made with the drum, and I think it is well worth while to do it, if merely for the fun of mystifying people. The drum is going to be suspended by the flexible cords; therefore, let them be the same length, and cutting off all the coverings at the end of each, fasten a brass “eye” to the copper, twisting the wire well round the bottom of the eye. Now wind silk of the same color as the rest all round the join, so that the connection of wire and eye is completely hidden, and the eye appears merely fastened to the flexible cord as a means of suspending the drum. Now we want to construct a hook from which the drum can be hung.

PART V.

Take two small pieces of brass wire about an inch long, and turn up the ends of each into a hook. Now get a minute piece of ebonite of the same length, and, putting one hook on one side and one on the other, bind the whole together with silk. If you cannot get ebonite easily you can use a small piece of sealing-wax in the same way; by heating the wires you can sink them into the wax and so make a neater join. Now the wires must not touch each other anywhere, but must be completely separated by the ebonite or sealing-wax. The double wire from the battery and press is now fastened, one wire to the press hook on one side, and one wire to that on the other side of the sealing-wax or ebonite. Wind silk over the whole to cover the joins, and a neat double hook is the result. The picture (Fig. 6) gives the method of making the hook, and it also gives a great deal more, which I now proceed to explain.

Supposing we can rig up a small beam of wood from which to suspend the drum, we can make matters more mysterious still. Let the double wire, being hidden by some means or other all along its course, be conducted on to the end of the beam. It can then be trained along the top of it until it comes to the point from which the drum is to hang. Here there must be a hole drilled, large enough to admit the hook rather tightly. Pull the double wire through and fasten the two wires to the hooks as before described.