How Two Boys Made Their Own Electrical Apparatus Part 9

[Ill.u.s.tration: Fig. 68.]

[Ill.u.s.tration: Fig. 69.]

APPARATUS 92.

_128. Crank for Winders, etc._ Fig. 69. This form of crank or handle will be found easier to make than the one in which a wire is expanded in the slot of a stove bolt, and it can be used for many purposes, especially where dowels serve as axles. Wrap a little paper around the end of the 1/4 in. dowel, D, and push it part way into the spool, A, then put in a set-screw, S, to keep A from twisting upon D. The straight end of the wire, H, should be put into a hole, B, and another set-screw used to fasten it into the spool.

APPARATUS 93.

_129. Winder._ Fig. 70. For winding bolt magnets, this form of winder is very useful. It consists of a "stove bolt," S B, 2 in. long (total length) and 5/16 in. in diameter.

[Ill.u.s.tration: Fig. 70.]

130. Handle or Crank, H, is made of a stout wire, 4 in. long, bent at the lower end as shown. H is fastened into the slot of S B. To do this the end of H is hammered flat until it will just slip into the slot. It may be soldered there, or be made to fit by expanding it so that it will press out against the sides of the slot. To do this, place S B into a hole in an anvil, or hold it in a vise, being careful not to injure the thread. Place the flattened end of H in the slot, and strike it on top so that it will expand and be pinched in the slot; but do not pound it so hard that you split the bolt head. Three or four good center-punch dents upon the wire over the slot will help to expand it.

131. The Framework is made of wood, the dimensions being shown in Fig.

70. A 5/16 hole should be made for S B, the thread of which will stick through about 1/4 in. so that the winder-nut, W N, can be turned onto it. W N should be on but 2 or 3 threads of S B. This will leave part of it for the thread of the bolt magnet, and when this and S B meet in center of W N they will bind against each other and hold the bolt tight.

The winder can be nailed or screwed at S to the edge of a table or held in a vise.

APPARATUS 94.

[Ill.u.s.tration: Fig. 71.]

_132. Winder._ Fig. 71. This shows a winder that can be used for several purposes by arranging different attachments. It will be first described as shown in Fig. 71, where it is being used to wind a bolt magnet. The princ.i.p.al dimensions are shown in the figure. It is made of 3/4 in. wood about 3 in. wide, the two outer parts X and Z being nailed to the center one, Y, which is to be held in a vise, or fastened to the edge of a table. A 5/16 in. hole should be made through the upper part X and Z at one side of the center, so that a long 5/16 bolt can be put through and used as described in App. 93, if desired. A smaller hole, 1/4 in., should be made on the other side of the center for a 1/4 in. dowel. The dowel, D, is shown, and this size is a little smaller than the hole in ordinary spools, shown at A and B. One-quarter in. dowels can be made to fit fairly tight into the holes by wrapping paper around them.

Five-sixteenth bolts can be screwed into the spool holes, shown by the bolt magnet in Fig. 71. To firmly hold a spool from twisting around upon the dowel-axle, a set-screw, S S, is needed. These are small screws, say 5/8 in. long, No. 5. A small hole should be made into the spool before forcing in the screw. (App. 25.)

The spools A and B are fastened in this way, by set-screws, to D. The handle, H, is made as in App. 93, in this case a short stove bolt, S B, being used and screwed into B. Fig. 69 shows a very simple form of handle for all such purposes, which may be used instead of the one here shown. The details of winding on the wire are given under App. 88.

APPARATUS 95.

_133. Attachment for Winder._ Fig. 72. By using this addition to App. 93 or 94, almost any ordinary kind of windings can be made. The wooden block, A, may be about 2 in. square and 7/8 in. thick. A set-screw, S, binds it to the dowel-axle, D, which is made to turn by one of the forms of cranks given, and which is held in one of the frameworks. Windings like that shown in App. 112, Fig. 85, can easily be done with this, the upright part, with the two spools, being screwed right to A of Fig. 72.

[Ill.u.s.tration: Fig. 72.]

CHAPTER XI.

INDUCTION COILS AND THEIR ATTACHMENTS.

_134. Induction Coils_, or shocking coils, are rather expensive to buy, and altogether too complicated for boys to make by the methods usually given in books. The method here given is simple, the materials are cheap, and if you make them according to directions, you will have an apparatus that will, be able to make your friends dance to a rather lively tune. The amount of shock can be regulated perfectly (App. 103).

Winding. Full instructions have been given for making bolt magnets (App.

88). The winding of our induction coils is done in the same way by the same winder as the bolt magnets (App. 93), or by hand. You will find it a very tiresome and troublesome job, however, to wind on 12 or 15 hundred turns of fine wire by hand. Make a winder.

Several different forms of induction coils are shown. The coil is the most important feature, however, and we shall consider that separately.

When you understand the construction of one coil, you can readily apply this to the different forms. Some form of contact breaker, or current interrupter, is needed also. These will be treated by themselves. The connections will be discussed under each form of apparatus.

APPARATUS 96.

_135. Induction Coil; Construction of Coil Proper._ Figs. 73, 74. An induction coil is a peculiar and wonderful apparatus. There are at least two coils to each one. These are both wound upon the same core. They are made of different sizes of wire, are wound separately, and the strangest thing of all is, that these two coils are not connected with each other in any way. If they were not thoroughly insulated from each other, the coil would be of no value. (Study induction.) The winding of the two coils is done as explained in App. 88.

[Ill.u.s.tration: Fig. 73.]

[Ill.u.s.tration: Fig. 74.]

136. The Core is made of a 5/16 machine bolt, 2-1/2 in. long. Leave but 2 or 3 threads at the end, just enough to fasten it solidly to the winder (App. 93). The washers should be about 1-5/8 in. apart inside, and they should be made around a spool (-- 119) that is fully 1 in. in diameter.

137. The Inside or Primary Coil could be wound directly upon the bolt; but it is much better to cover the bolt with one or two thicknesses of paraffined paper, I (Index), as shown. A pinhole, H, in the washer is for the inside end (see -- 123) of the primary coil, and the hole, J, is for the outside end of it.

The primary coil should be made of 3 layers of wire, which should be coa.r.s.er than that used for the secondary coil. For our purposes it is best not to use a wire coa.r.s.er than No. 20, and not finer than No. 24.

Use No. 24 insulated copper wire if you are going to connect ordinary batteries with it. A bichromate cell (App. 4) is best. Put about 6 in.

(see -- 109) of wire through H, and with App. 93 wind on 3 layers of say No. 24 wire. There being an odd number of layers, the winding will stop at the head end of the bolt, where a half hitch (see -- 110) should be taken before pa.s.sing the wire through the hole, J. Cut the wire 6 in.

from the hole. Write down the number of turns of wire to each layer and the total number of turns. You now have a 3-layer coil, and a current pa.s.sed through this will magnetize the bolt; you have--so far--merely an electro-magnet. Cover the primary coil with 2 layers of paraffined paper, K (Fig. 74), and put some paraffine between the edges of K and the washers, so that the wire of the secondary coil cannot possibly come in contact with that already wound on.

138. The Secondary Coil should be made of a large number of turns of fine wire. Do not use anything coa.r.s.er than No. 30. This is a good size, as finer wire is very easily broken by unskilled hands. For the size of bolt mentioned put on 13 layers. There will be about 100 turns to each layer, making a total of about 1,300 turns of No. 30 wire. Write down the total number of turns in your coil. To start the secondary coil, make a pinhole, L, just outside of the insulation, K, of the primary coil. Put 6 in. of wire through this, wind the end around the nut (App.

93, Fig. 70), and wind on as evenly as possible 13 layers. If the layers become rough, it is well to put a band of paper around after each 3 or 4. When you have finished take a half hitch (-- 110), and leave a 6-in.

length free. Cover the secondary coil with strong paper. This coil may be used on any of the forms of shockers given.

APPARATUS 97.

139. Induction Coil. Fig. 75. The base is made of a piece of board, 7 5 7/8 in. The locations of the different parts are shown in the figure. The coil is explained in detail in App. 96. It is fastened to the base by a thin copper strip, 4, which is bent over the coil and held down by screws, 3. If you haven't any copper you can use a narrow strip of tin. Do not use a wide piece of tin or iron. The coil may be held down firmly by strong twine placed around each end of it. The twine should pa.s.s through holes in the base, and be tied on the underside of the base. The binding-posts are like App. 46.

140. The Current Interrupter consists of a tin or copper strip, R, 6 in.

long and 1/2 or 3/4 in. wide. At one end of R is a screw, S, which is used as a binding-post for the outside end, B, of the primary coil. (See -- 137.) Along the center line of the strip, R, are driven 1-in. wire nails, Q. These are placed 1/4 in. apart, and they should go into the wood enough only to make them solid. (See Fig. 81.) Do not drive them in so far that they will split the base. A stout wire, P, fastened at one end only completes the interrupter.

[Ill.u.s.tration: Fig. 75.]

141. The Connections. The binding-posts, W and X, should be connected with the wires leading from a battery. Use the bichromate batteries of App. 3 or 4. A dry battery will do. If the current enters at X, it will pa.s.s around the primary coil (-- 137) and out through B into R. It can go no farther until the free end of P is made to touch R, or one of the nails, Q, when the circuit will be closed. The current will fly around and around through the battery, primary coil, and interrupter as long as the end of P touches a nail. The battery current does not get into the secondary coil at all. You can see, then, that the primary circuit, that is, the one pa.s.sing through the coa.r.s.e wire, will be rapidly opened and closed by b.u.mping the free end of P along upon the row of nails.

The wires, C and D, coming from the secondary coil (-- 138) are in connection with Y and Z, to which are connected the wires leading from the handles (App. 101) held by the person receiving the shock.

142. To use the coil, arrange as explained. Let your friend hold the handles (App. 101) while you sc.r.a.pe the end of P back and forth along the row of nails. For those who cannot stand much of a shock, use a regulator (App. 103).

APPARATUS 98.

_143. Induction Coil._ Fig. 76. In case you wish to make the interrupter as a separate piece of apparatus, as App. 104, this arrangement will be found good. The base is 5 4 7/8 in. The coil is explained in App.

96, and the methods of holding it to the base are given in App. 97. The binding-posts are like App. 46.