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

There are many toys which one meets with in the scientific stores, the making of which for themselves would give great satisfaction to enterprising devotees of the electrical art. They are for the most part easily constructed, and a great deal of amusement can be derived from them. I have my doubts whether the fathers and mothers of the amateur electrician will thank me for introducing the subject of the present article, but they must take comfort in the thought that if it works well it shows real constructive power on the part of the maker.

For the benefit of those whose capability of working in metal is limited, I am first going to describe the making of this remarkable instrument in its simplest form—a form, in fact, so simple that any one can make it and achieve success in a few hours.

First of all we want an old tooth-powder box. These are all made the same size, and consequently it is unnecessary to give dimensions. The top of the tooth-powder box is to be taken, and by means of a fretsaw (this invaluable tool should be in the hands of every boy who likes carpentering; there are many uses to which it can be put quite different for what it is intended for) a circular hole is to be cut out about ⅛ inch less than the inside—that is to say, a rim of about ⅛ inch is to project all around from the rim of the lid.

We now want what is known in photography as a “ferrotype” plate—i. e., a piece of very thin sheet iron. Most dealers in photographic goods will not sell less than four or five dozen of them, and this is too many for us. A photographic friend will let us have one gratis, or a professional photographer may agree to part with one for five or ten cents if he is attacked when in a good temper.

The ferrotype plate having been procured by some means or other, the next thing is to cut from it a circle just small enough to go inside the rim of the top of the tooth-powder box. You can mark out the circle before cutting it by painting the top of the rim of the bottom of the tooth-powder box with ink and pressing it down on the ferrotype plate, when enough ink will come off to guide the scissors, and of course the circle so cut will be the exact size required.

We now have to make the motive power of the machine, for there is plenty of work done in it, though it only makes a noise—no one can “make a noise in the world” without doing plenty of work! And to make this we take a piece of soft iron rod about 1½ inch long and half an inch in diameter, and cut two circles out of cardboard 1¾ inch in diameter. The soft iron rod can be bought from any hardware store, and it ought to be quite soft enough to work at once without doing anything to it; if it is not, it must be heated red-hot in a good fire and left among the coals over-night to get cool very gradually.

Personally I have always found that the ordinary bars of soft iron bought from any hardware man are amply soft enough for any electrical work.

You must get the hardware man to file the ends of your bar flat; if they are not filed you will have to do it yourself, and a fine job it is!

Now we go back to the circles of cardboard. A hole is to be cut in each in the center exactly the size to admit the core of soft iron, then by slipping the circles over the ends we get a reel. Now a hole has to be made exactly in the center of the bottom of the tooth-powder box, and exactly so large that the core of soft iron will fit tightly into it; you can do this again with the fretsaw, the wood of which tooth-powder boxes are made is delightfully easy to cut.

Now comes the adjustment of the reel. You must put the circles on the core, and putting one end of the latter through the hole at the bottom of the box you must push the iron through until the top is exactly flush with the top of the rim of the side of the box. One of your circles will now be much further on the core than the other, and the one at the end that is not pushed through the hole must be adjusted close to the edge, leaving about ¹⁄₁₆ of the core projecting, so that we have now a reel formed at one end of the core, and held in position by the bottom of the box. The more stiffly the core fits the hole the better, and if it has to be hammered into its place, better still, only take care not to split the wood of the bottom of the box.