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.
[Illustration: Fig. 73.]
[Illustration: 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 (Sec. 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 Sec. 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
coarser than that used for the secondary coil. For our purposes it is
best not to use a wire coarser 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 Sec. 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 Sec. 110)
should be taken before passing 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 passed 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 coarser 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 (Sec. 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 x
5 x 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 pass 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
Sec. 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.
[Illustration: 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
pass around the primary coil (Sec. 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 passing through the coarse wire, will be rapidly opened and
closed by bumping the free end of P along upon the row of nails.
The wires, C and D, coming from the secondary coil (Sec. 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 scrape 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 x 4 x 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.
[Illustration: Fig. 76.]
The Connections. We shall suppose that you have the interrupter of App.
104, Fig. 81. The ends of the primary coil (Sec. 137) are fastened
under the screws of X and W, and those of the secondary coil to Y and
Z. Connect one battery wire with X and the other battery wire to the
interrupter at S, Fig. 81. Fasten the end of a stout wire to W, and
leave the other end free to scrape along on the nails, Q, of the
interrupter. This will then open and close the primary circuit. The
handles (App. 101) are connected with Y and Z, as explained in App. 97.
Use the battery of App. 3 or 4.
APPARATUS 99.
_144. Induction Coil._ Fig. 77. If you wish to fasten your coil in an
upright position the apparatus will look like Fig. 77. The base may be 5
x 4 x 7/8 in. The binding-posts are like App. 46. The coil is made as
explained in App. 96; but to have all the ends of the coils come out at
the bottom, as shown, an even number of layers of wire will be
necessary. It will be just as well to have an odd number of layers as
before, and to bring the wire ends down the side of the coil. The coil
is fastened to the base with screws, S, passing through a tin strip, T,
which has a hole punched for the bolt. T is squeezed between the regular
nut on the bolt and an extra one on the underside of it. See Fig. 61 for
suggestion of another method of holding bolts upright. The connections
should be made with an outside interrupter, battery, and handles, as
explained in App. 98.
[Illustration: Fig. 77.]
APPARATUS 100.
_145. Induction Coil._ Fig. 78, 78-A, 78-B. In case you wish to make a
larger coil than those already described, the following will be found
practical. It is made in the same general way as before, an automatic
interrupter, however, being added.
The Core is a machine-bolt, 4-1/2 in. long and 5/16 in. in diameter. You
may use a carriage-bolt of the same dimensions, if you file away the
square shoulder at the head end, so that it will be the same size as the
body of the bolt. Paste a piece of thick paper upon the head, so that A
will strike the paper instead of the iron. The Washers should be made
around a spool that is fully 1 in. in diameter. (See Sec. 119.) The core
should be insulated with paraffine paper before winding on the primary
coil. (See App. 88.) The washers are 3-7/8 in. apart, inside. The
winding of the coils should be done with App. 93, or some other winder.
The winder-nut, W N, Fig. 70, must hold the long core perfectly tight,
to avoid wobbling. The base is 8 x 5 x 7/8 in. The different parts are
placed as shown. The coil is fastened to the base as in App. 97. For
binding-posts see App. 46.
[Illustration: Fig. 78.]
146. The Primary Coil (Sec. 137) is made by winding 3 layers of No. 24
insulated copper wire upon the insulated core. One end, 6, is fastened
to W (See Sec. 109), and the other end, 5, is held under the screw-head,
R. Wind at least two layers of paraffined paper around this coil before
winding on the secondary coil.
147. The Secondary Coil (Sec. 138) is made of No. 30 insulated copper
wire, there being 11 or 13 layers, each having about 200 turns. This
makes, in all, about 2,500 turns of fine wire. If your winder works
properly and the long core is strongly held by the winder-nut, you will
have no trouble, although it takes a little time to wind on so many
turns. The ends of this coil, 7 and 8, are fastened to Y and Z, which
are made like App. 46. It will be found best to wrap a piece of thin
paper around the coil after every 3 or 4 layers are wound on. This
makes better insulation, and makes the winding easier. Protect the coil
by covering it with thick paper. The whole coil, when completed, is
about 1 in. in diameter.
[Illustration: Fig. 78-A.]
[Illustration: Fig. 78-B.]
148. The Automatic Interrupter (Figs. 78, 78-A, 78-B) consists of
several parts. B, E, C is a piece of thin tin, all in one piece. The
part, B, is 1/4 in. wide and 1-3/4 in. long. Its exact height above the
base will depend upon the diameter of your coil. For the coil here
described, 1 in. in diameter, the top edge of B is 5/8 in. above the
base. See Fig. 78-B for shape of B, E, C before bending it, and for its
dimensions. Around the end of B are tightly wound several turns of tin,
making the armature or hammer, A, which should not be allowed to strike
against the head of the bolt on account of residual magnetism. (See
text-book.) A piece of thick paper pasted on the head for A to strike
upon is best. A will probably not get near enough to the bolt to strike
it, but this will depend upon how you arrange the parts.
D is a wooden piece, 1 in. high, 1 in. wide, and 3/8 or 1/2 in. thick;
it is nailed to the base. Through its center is a hole for the
screw-eye, S I, which is the regulating-screw. F is a piece of copper,
brass, or tin, 5/8 x 1-3/4 in. It is held to the base by the screw, S,
and is bent so that it presses tightly against S I. Through F is a
screw, R, to hold one end of the primary coil.
149. Adjustment and Use. The battery wires should be joined to W and X,
and the handles to the secondary coil at Y and Z, unless a regulator
(App. 103) is used. Let us consider the primary circuit. If the current
enters at W it will pass through the primary coil and out at X, after
going through 5, R, F, S I, B, E, and C. The instant that the current
passes, the bolt becomes magnetized; this attracts A, which pulls B away
from the end of S I, thus automatically opening the circuit. B at once
springs back to its former position against S I, as A is no longer
attracted; the circuit is closed and the operation is rapidly repeated.
B should press gently against S I, which must be screwed back and forth,
until the best results are obtained. While not in use A should be about
1/8 or 3/16 in. from the bolt-head. The armature, A, should vibrate back
and forth very rapidly. If this coil gives too much shock with one cell
of App. 3 or 4, put a regulator (App. 103) between Y and one of the
handles (App. 101).
APPARATUS 101.
_150. Handles for Shocking Coils._ Fig. 79. Ordinary sheet-tin makes
good handles. Cut 2 pieces, each 6 x 4-1/2 in., and connect a stout
copper wire to each. This may be done as suggested in Fig. 79, where the
tin laps tightly over the bare end of the wire, or by punching 4 or 5
holes through the tin, and weaving the wire back and forth through the
holes. Be sure that a tight and permanent connection is made. The wires
joined to the handles should be about No. 20, and be 4 or 5 feet long.
Roll the tin into a cylinder, so that the connection will be on the
inside.
[Illustration: Fig. 79.]
APPARATUS 102.
_151. Handles for Shocking Coils._ Very neat handles may be made from
4-in. lengths of brass tubing that is about 3/4 in. in diameter. The
wires leading to the coil may be soldered to the handles.
APPARATUS 103.
_152. Current Regulator for Induction Coils._ Fig. 80. If your coil
gives too much of a shock with one cell of App. 3 or 4, you can pull the
carbon and zinc partly out of the solution to weaken the shock, or you
can use a water regulator. T is an ordinary tin tomato can nearly filled
with water, L is a lamp chimney. One wire, A, is fastened to T directly,
or by a spring binding-post. The other wire, B, is fastened to a piece
of copper, C, which may be raised or lowered inside of L. D is a piece
of pasteboard with a small hole in its center.
153. Use. If this apparatus be put anywhere in the primary circuit, the
amount of shock can be regulated by raising or lowering C. When C is
raised, the current has to pass through a longer column of water than it
does when C is near the bottom of L. When C touches T, the current
passes easily. If it were not for the chimney, the current would pass to
the sides of T.
[Illustration: Fig. 80.]