How Two Boys Made Their Own Electrical Apparatus Part 3

Hold the yoke as in App. 79 or 80 for filing. As you will probably have no anvil, lay an old nut from a bolt upon the end of the block of wood (App. 26), place the metal to be punched over the hole, and imagine that you have an anvil. Very good results may be obtained by this method. The size of nut used will depend upon the size of hole wanted.

APPARATUS 28.

_43. To Straighten Wires._ It is often necessary to have short lengths of wires straight, where they are to be made into bundles, etc. To straighten them, lay one or two at a time upon a perfectly flat surface, place a flat piece of board upon them, then roll them back and forth between the two. The upper board should be pressed down upon the wires while rolling them. If properly done, the wires can be quickly made as straight as needles.

_44. Push-b.u.t.tons._ Nearly every house has use for one or more push-b.u.t.tons. The simple act of pressing your finger upon a movable b.u.t.ton, or k.n.o.b, may ring a bell a mile away, or do some other equally wonderful thing.

APPARATUS 29.

_45. Push-b.u.t.ton._ Fig. 14. This is made quickly, and may be easily fastened to the window or door-casing. One wire is joined to A and the other to C. B is a strip of tin or other metal, about 5/8 in. wide and 2 in. long. It is bent so that it will not touch A unless it is pressed down. This may be placed anywhere, in an electric-bell circuit or other open circuit, where it is desired to let the current pa.s.s for a moment only at a time.

[Ill.u.s.tration: Fig. 14.]

APPARATUS 30.

_46. Push-b.u.t.ton._ Fig. 15 and Fig. 16. By placing App. 29 in a box, we can make something that looks a little more like a real push-b.u.t.ton.

Fig. 15 shows a plan with the box-cover removed, and Fig. 16 shows a view of the inside of it, a part of the box being cut away. C, Fig. 15, is a wooden pill-box 1 in. high and 1-3/4 in. in diameter. Make a 1/4 in. hole in the cover of C for the "b.u.t.ton," G, which is a short piece of 1/4 in. dowel. This rests upon a single thickness of tin, D, which is cut into a strip 3/8 in. wide and about 1-1/4 in. long. In the bottom of C are two holes just large enough to allow the screws E and F to pa.s.s through. The wires, A and B, pa.s.s from the binding-posts, X and Y, through small holes burned through the sides of the box, and are fastened under the screw-heads. The whole box is screwed to the wooden base, which is 3 4 7/8 in., by the screws, E and F. D should have enough spring in it to raise itself and G when the pressure of the finger is removed. The circuit will be closed only when you press the b.u.t.ton.

[Ill.u.s.tration: Fig. 15.]

[Ill.u.s.tration: Fig. 16.]

APPARATUS 31.

_47. Push-b.u.t.ton._ Figs. 17, 18, 19. Fig. 17 shows a top view or plan of the apparatus. Fig. 18 is a sectional view; that is, we suppose that the b.u.t.ton has been cut into two parts along its length and through the center line. Fig. 19 is an enlarged detail drawing of the underside of the spool, C. The same part is marked by the same letter in all of the figures.

[Ill.u.s.tration: Fig. 17.]

[Ill.u.s.tration: Fig. 18.]

[Ill.u.s.tration: Fig. 19.]

Saw an ordinary spool, C, into two parts. One-half of C will serve as the outside case for the b.u.t.ton. The part to be pressed with the finger is a short length of 1/4 in. dowel. To keep this from falling out of the hole in C, a short piece of wire nail, N, has been put through a small hole in its lower end. A slot, F, has been burned or cut into the underside of C, so that N can pa.s.s up and down in it when D is raised and lowered. The rod, D, rests upon A, one of the contacts. This is a straight piece of tin, cut as shown in Fig. 17, the narrow part being 1/4 in. wide and 1-1/4 in. long. The wide part is 3/4 in. wide and 1 in.

long. The other contact, B, is the same size as A. A deep groove, a little over 1/4 in. wide, is cut into the base so that the narrow part of B can be bent down below the end of A. The base shown is 4 2-1/2 7/8 in. The spool, C, is fastened to the base by 2 screws or wire nails put up through the base, their positions being shown by the dots at E, Fig. 17. X and Y, Fig. 18, are 2 screw binding-posts. It is evident that the current cannot pa.s.s from X to Y, unless the b.u.t.ton, D, be pressed down so that the end of A will touch B.

APPARATUS 32.

_48. Sifter for Iron Filings._ Fig. 20. In making magnetic figures with iron filings, it is an advantage to have the particles of iron fairly small and uniform in size. A simple sifter may be made by p.r.i.c.king holes in the bottom of a pasteboard pill-box with a pin. The sifter may be put away with the filings in it, provided you turn it upside down.

[Ill.u.s.tration: Fig. 20.]

APPARATUS 33.

_49. Sifter for Iron Filings._ Fig. 21. Punch small holes in the cover of a tin box with a small wire nail. If you have occasion to use sifters for other purposes, the different sizes can be made by using larger and smaller nails to punch the different tin covers. But one size of nail should be used for one sifter.

[Ill.u.s.tration: Fig. 21.]

APPARATUS 34.

_50. Sifters_ may be made by p.r.i.c.king holes in an envelope. A sifter with very small holes can be made of a piece of muslin cloth. This can be used in the form of a little bag, or a piece of it can be pasted over the open bottom of a pill-box.

APPARATUS 35.

_51. To Cut Wires, Nails, etc._ If you have no wire-cutters, or large shears, you can cut large or small wires by hammering them against the sharp edge of another hammer, an anvil, or a piece of iron. Do not let the hammer itself hit upon the edge of the anvil. The above process will make a V-shaped dent on one side of even large wires, or nails, when they may be broken by bending back and forth.

CHAPTER IV.

SWITCHES AND CUT-OUTS.

_52. Switches, Cut-Outs._ Where apparatus is to be used frequently, such as for telephone and telegraph lines, it pays to make your switches, etc., carefully. The use of these switches, etc., will be shown in the proper place. Their construction only will be given here.

APPARATUS 36.

_53. Cut-Out._ Fig. 22. Details. X, Y, and Z represent 3 binding-posts like App. 42. These are fastened to a wooden base that is about 3 5 3/4. The ends of the wires shown come from and go to the other pieces of apparatus. Q shows a stout wire or strip of 2 or 3 thicknesses of tin.

Suppose we have an apparatus, as, for example, an electric bell, which we want to have ring when someone at a distance desires to call us. If we use a telephone or telegraph instrument we shall want to cut the bell out of the circuit as soon as we hear the call and are ready to talk.

Suppose the current comes to us through the wire, A, Fig. 22. It can pa.s.s by the wire, C, through the bell and back to X. If we wanted simply to have the bell ring, the current could pa.s.s directly from X into the earth, or over a return wire back to the push-b.u.t.ton at our friend's house. If, however, we are to use some other instrument, by lifting the end of Q out of X and pushing it into Y, the bell will be cut out, and the current can pa.s.s on wherever we need it.

[Ill.u.s.tration: Fig. 22.]

APPARATUS 37.

_54. Cut-Out._ Fig. 23. The main features of this are like those of App.

36. The three binding-posts are like App. 46. Instead of a band of metal to change connections, as Q in App. 36, a stout copper wire is used.

This can be easily changed from one of the upper binding-posts to the other, thereby throwing in or cutting out any piece of apparatus joined with the upper connectors.

[Ill.u.s.tration: Fig. 23.]

APPARATUS 38.

[Ill.u.s.tration: Fig. 24.]

_55. Switch._ Fig. 24. This simple switch has but one contact point, D, which is a screw-head. This switch may be used anywhere in the circuit by simply cutting the wire carrying the current, and joining the ends of the wire to the binding-posts X and Y. The metal strip, E, is made of 2 or 3 thicknesses of tin. It is 5/8 in. wide and about 5 in. long, and presses down upon D, when swung to the left, thus closing the circuit.

The short metal strips shown are 5/8 1-1/4 in. The upper strip is joined to the end of E by a coiled copper wire, C W. (See App. 50.) If the current enters by the wire, A, it will pa.s.s through C W, E, D and out at B. The strip E is pivoted at F by a small screw. The base may be 3 or 4 5 7/8 in.