Produced by James Simmons.

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Transcriber’s Note


This book was transcribed from scans of the original found at the
Internet Archive.




                        ARTS AND SCIENCES No. 9

                               Home-made

                               Toy Motors

     A Practical Handbook Giving Detailed Instructions for Building

                          Simple but Operative

                            Electric Motors

                                   BY

                              A. P. Morgan

                          COLE & MORGAN, Inc.

               Publishers of the Arts and Sciences Series

                    P. O. BOX 473 CITY HALL STATION

                            NEW YORK, N. Y.




                             COPYRIGHT 1919

                                   BY

                          COLE & MORGAN, Inc.




    CHAPTER I. EXPLAINING HOW AN ELECTRIC MOTOR OPERATES. SOME
    PRINCIPLES OF MAGNETISM. THE DIFFERENCE BETWEEN A SHUNT AND A SERIES
    MOTOR. ............................................................
    CHAPTER II. THE CONSTRUCTION OF SIMPLE TOY ELECTRIC MOTORS. .......
      SIMPLEX MOTOR WITH THREE-POLE ARMATURE. .........................
      HOW TO MAKE THE SIMPLEX OVERTYPE MOTOR. .........................
      THE MANCHESTER MOTOR. ...........................................
    CHAPTER III. A Magnetic Attraction Motor. A Motor Having a Laminated
    Field and Armature Frame. How to Make an Experimental Induction
    Motor. How to Make an Electric Engine. ............................
      A MAGNETIC ATTRACTION MOTOR. ....................................
      HOW TO CONSTRUCT A MOTOR HAVING A LAMINATED ARMATURE AND FIELD
      FRAME ...........................................................
      HOW TO MAKE AN EXPERIMENTAL INDUCTION MOTOR. ....................
      HOW TO BUILD AN ELECTRIC ENGINE .................................
    CHAPTER IV SMALL POWER MOTORS .....................................
      A VERTICAL POWER MOTOR ..........................................
      CONNECTIONS FOR THE THREE POLE ARMATURE .........................
      CONNECTIONS FOR THE SIX-POLE ARMATURE ...........................
      A HORIZONTAL POWER MOTOR. .......................................




    FIG. 1.—If a current of electricity is passed through a wire, the
    wire will attract to itself iron filings. .........................
    FIG. 2.—If a wire carrying a current of electricity is formed into a
    loop, the space enclosed by the loop will become magnetic. The
    arrows represent the paths of the lines of magnetic force. ........
    FIG. 3.—By forming the wire into several loops or a spiral so that
    the effect of the individual turns is concentrated in a small space,
    an _Electromagnet_ is made. .......................................
    FIG 4—The strength of an electromagnet is proportional to the ampere
    turns. The magnet illustrated above does not possess sufficient
    turns to be very strong. ..........................................
    FIG. 5.—An increase in the number of turns of wire has resulted in
    considerable increase in the magnetism and this magnet is able to
    lift a much greater weight than that shown in Figure 4. ...........
    FIG. 6.—The Principle of the Electric Motor. ......................
    FIG. 7.—Diagrams showing the difference between a Shunt and a Series
    Motor. ............................................................
    FIG. 8.—Details of the Armature for the Simplex Two-pole Motor. ...
    FIG. 9.—Showing the Armature assembled on the shaft ready for
    winding. ..........................................................
    FIG. 10.—A front view of the Field Frame. .........................
    FIG. 11.—The completed Field Frame, ready for winding. ............
    FIG. 12.—The Bearings. ............................................
    FIG. 13.—Side view of the Armature and Commutator Core assembled on
    the Shaft before winding. .........................................
    FIG. 14.—Showing the Motor assembled on the Base so that all the
    parts may be lined up before winding. .............................
    FIG. 15.—The Field Frame with the Winding in position. ............
    FIG. 16.—The Armature Winding before the Commutator is completed. .
    FIG. 17.—The completed Armature showing how the Commutator is
    constructed. ......................................................
    FIG. 18.—Details of the Commutator. ...............................
    FIG. 19.—The completed Motor. .....................................
    FIG. 20.—Details of the Three-pole Armature. ......................
    FIG. 21.—The Three-pole Armature assembled on the shaft. ..........
    FIG. 22.—Showing the Armature and Shaft with the Commutator Core in
    position. .........................................................
    FIG. 23.—Diagram showing how the coils are connected together so as
    to form a continuous winding. .....................................
    FIG. 24.—The completed Three-pole Motor. ..........................
    FIG. 25.—The Simplex "Overtype" Motor. ............................
    FIG. 26.—Details of the Field Frame for the "Overtype" Motor. .....
    FIG. 27.—Showing how the Field is Wound. ..........................
    FIG. 28.—The Bearings. ............................................
    FIG. 28.—The Manchester Motor. ....................................
    FIG. 30.—Details of the Field Frame. ..............................
    FIG. 31.—Details of the Field Pedestal. ...........................
    FIG. 32.—Showing how the Field Coils are Wound. ...................
    FIG. 33.—Details of the Magnet Bobbins. ...........................
    FIG. 34.—The completed Electromagnets mounted on the Yoke. ........
    FIG. 35.—Details of the Armature Shaft. ...........................
    FIG. 36.—Details of the Standard which forms the upper bearings. ..
    FIG. 37.—The Brass Contact. .......................................
    FIG. 38.—The Brush which bears against the Contact. ...............
    FIG. 39.—The completed Magnetic Attraction Motor. .................
    FIG. 40.—The completed Electric Motor. ............................
    FIG. 41.—Details of the Field Frame. ..............................
    FIG. 42.—The Assembled Field ready for Winding. ...................
    FIG. 43.—Details of the Armature Laminations. .....................
    FIG. 44.—The Armature assembled on the Shaft ready to Wind. .......
    FIG. 45—The Commutator and Method of connecting the Armature Coils.
    FIG. 46.—The Bearings. ............................................
    FIG. 47.—Brush and Supporting Block. ..............................
    FIG. 48.—A well known Three-pole Battery Motor. ...................
    FIG. 49.—Showing how a Three-pole Motor may be provided with
    "Starting Coils" and connected to form an Experimental Induction
    Motor. ............................................................
    FIG. 50.—The completed Engine. ....................................
    FIG. 51.—The Base. ................................................
    FIG. 52.—Details showing the size of the Magnet Bobbin. ...........
    FIG. 53.—The Frame which supports the Electromagnets. .............
    FIG. 54.—The Main Bearings. .......................................
    FIG. 55.—The Shaft. ...............................................
    FIG. 56.—Showing the Armature, Armature Bearing and the Connection
    Rod. ..............................................................
    FIG. 57.—Details of the Brushes and Brush Holder. .................
    FIG. 58.—Showing how a Flywheel may be made out of sheet iron. ....
    FIG. 59.—A Vertical Battery Power Motor. ..........................
    FIG. 60.—Details of the Field Frame of the Vertical Motor. ........
    FIG. 61.—Three-pole Armature. .....................................
    FIG. 62.—Six-pole Armature. .......................................
    FIG. 63.—Showing how the Coils on a Three-pole Armature are
    connected to the Commutator. ......................................
    FIG. 64.—Showing how the Coils on a Six-pole Armature are arranged
    and connected. ....................................................
    FIG. 65.—Details of the Commutator. ...............................
    FIG. 66.—Details of the Bearings, Shaft, and Pulley. ..............
    FIG. 67.—The Brushes and Brush Holder. ............................
    FIG. 68.—Details of the Field Frame for the Horizontal Power Motor.
    FIG. 69.—Front view of the Field Frame. ...........................
    FIG. 70.—The Field Magnet Bobbin. .................................
    FIG. 71.—Details of the Shaft, Rocker Arm, Bearing and Pulley. ....
    FIG. 72.—Rear view of the completed Horizontal Motor. .............
    FIG. 73.—Side view of the Horizontal Motor. .......................




CHAPTER I. EXPLAINING HOW AN ELECTRIC MOTOR OPERATES. SOME PRINCIPLES OF
MAGNETISM. THE DIFFERENCE BETWEEN A SHUNT AND A SERIES MOTOR.


*An Electric Motor* is a device for transforming electricity into
mechanical power. A generator, or dynamo, is constructed in almost the
same identical manner as a motor but its purpose is just the opposite. A
dynamo transforms *mechanical power into electricity*. A dynamo produces
electric current, but a motor *consumes* it. Some machines can be used
either as a motor or dynamo—not all however.

Of course most experimenters have in all probability seen many electric
motors, but it is more than likely that the exact operation is not
thoroughly understood. Here is your chance to learn.

The little motors described in this book can each be made in two or
three hours out of a few scraps of sheet iron, magnet wire and screws.
The cost of the necessary materials is practically negligible.

One of the main advantages of these little motors is that they
illustrate the actual principles that are used in the large motors, such
as are employed everywhere for practicable power purposes.

The iron parts may be made out of sheet iron or the ordinary so-called
"tin" used in cocoa cans, etc. Thin tin can be cut with an ordinary pair
of shears. Sheet iron such as is used in making stovepipes, etc., is an
excellent material to use in making these little motors. Sheet iron is
usually heavier than tin and will have to be cut with a pair of "snips."
Greater skill will also then be required in bending the parts. It is
worth while noting however, that the extra difficulty involved in using
the heavier material is worth the trouble because it makes possible a
more powerful and efficient motor.

The first and easiest type of motor to make is the "Simplex."

*The Principle on which an Electric Motor Operates* is really very
simple. If a current of electricity is passed through a copper wire, the
wire will attract to itself iron filings, etc., as long as the current
continues to flow. As soon as the current is shut off, the filings drop
away because the magnetism immediately disappears with the cessation of
the current.

[Illustration: FIG. 1.—If a current of electricity is passed through a
wire, the wire will attract to itself iron filings.]

If a wire, carrying a current of electricity is formed into a loop, the
entire space enclosed by the loop will possess the properties of a
magnet.

By forming the wire into several loops or a spiral the combined effect
of all the individual turns is concentrated in a small space and a much
more powerful field is produced. If the coil is provided with an iron
core, the magnetism is much more concentrated and will exercise a very
powerful attractive effect upon any neighboring masses of iron or steel.
Such a coil is called an electromagnet.

[Illustration: FIG. 2.—If a wire carrying a current of electricity is
formed into a loop, the space enclosed by the loop will become magnetic.
The arrows represent the paths of the lines of magnetic force.]

Electromagnets play a very important part in the construction of
electric motors. The strength of an electro magnetic coil is
proportional to its ampere turns. The number of ampere turns in a coil
is obtained by multiplying the number of amperes flowing through the
coil by the number of turns of wire composing it.

[Illustration: FIG. 3.—By forming the wire into several loops or a
spiral so that the effect of the individual turns is concentrated in a
small space, an _Electromagnet_ is made.]

You can easily see the effect of turns of wire on an electromagnet by
winding two or three turns of wire around a nail and connecting it to a
battery. These two or three turns will probably create enough magnetism
to enable the nail to lift up one or two ordinary carpet tacks.

[Illustration: FIG 4—The strength of an electromagnet is proportional to
the ampere turns. The magnet illustrated above does not possess
sufficient turns to be very strong.]

Then increase the number of turns to forty or fifty and note that the
magnetism of the nail has increased greatly and that it now possesses
power to pick up a larger number of tacks at a time.

From this one may be led to believe that the more turns of wire an
electromagnet possesses, the stronger it will be, and while to a certain
extent this is true, it should be remembered that it is not simply
*turns* that count but *ampere turns* and if the number of turns of wire
is increased beyond a certain point the resistance of the coil to the
electric current will become so great that the current in amperes
flowing through the coil is greatly reduced and consequently also the
magnetism is decreased.

[Illustration: FIG. 5.—An increase in the number of turns of wire has
resulted in considerable increase in the magnetism and this magnet is
able to lift a much greater weight than that shown in Figure 4.]

It will be found that the magnetism of an electromagnet is strongest at
the ends. These places are called the poles.

If you bring one pole of a small electromagnet, formed by winding a nail
with a few turns of wire, near a compass needle, you will find that it
will attract one end of the compass needle and repel the other. The end
of the compass needle which points North is called a *North* pole. The
ends of the electromagnet which attracts the North pole of the compass
needle is a *South* pole.

One of the most important laws of magnetism is that like poles repel
each other and unlike poles attract each other. A North and a South pole
therefore tend to pull toward each other, whereas two North poles or two
South poles repel one another.

Figure 6 illustrates the principle of an electric motor.

It consists of a bar of iron marked "A" called the *Armature* and wound
with a coil of wire called the armature winding. The armature is the
part of the motor which revolves.

[Illustration: FIG. 6.—The Principle of the Electric Motor.]

Each end of the armature winding is connected to one half of a brass
ring called the commutator and marked "C, C," in the illustration. The
two halves of the commutator are insulated from each other and are
mounted on the armature shaft so that they revolve together with the
armature.

The armature revolves between the ends of a horseshoe shaped piece of
iron called the field. The field is also wound with a coil of wire
called the *field winding* or sometimes the field coil.

The armature and the field are both electromagnets.

Two strips of copper, "B, B," bear against the commutator. These are the
*brushes*, and their purpose is to lead the current to the armature
coil.

One brush is connected to one end of the field coil. The other end of
the field coil and the other brush are connected to a source of electric
current.

As soon as the current is turned on, the armature and the field both
become magnets. The North pole of the field attracts the South pole of
the armature and vice-versa. The armature starts to move so that the
poles will come opposite but as the commutator moves around and is
turned over, the current flows through the armature coil in the opposite
direction. This reverses the magnetism of the armature and that which
was the South pole become the North pole and vice-versa.

[Illustration: FIG. 7.—Diagrams showing the difference between a Shunt
and a Series Motor.]

The armature poles will therefore have to move 180 degrees in order that
the South pole may come opposite the North pole of the field. Before it
gets there, however, the commutator will have turned over again,
reversing the current in the armature and making it necessary to
continue its journey again. This process keeps up and so the armature
revolves always trying to seek a new position which it is prevented from
remaining at by the action of the commutator.

Motors are said to be series or shunt wound depending on whether all the
current flowing through the armature also passes through the field or
whether it divides between the two as shown in Figure 7.




CHAPTER II. THE CONSTRUCTION OF SIMPLE TOY ELECTRIC MOTORS.


The Simplex Motor is an interesting little toy which can be made in a
couple of hours, and when finished it will make an instructive model.

As a motor itself, it is not very efficient, for the amount of iron used
in its construction is necessarily small. The advantage of this
particular type of motor and the method of making it is that it
demonstrates the actual principle and the method of application that is
used in larger machines.

[Illustration: FIG. 8.—Details of the Armature for the Simplex Two-pole
Motor.]

The field of the motor is of the type known as the "simplex" while the
armature is the "Siemen’s H" or two-pole type. The field and the
armature are cut from ordinary tin-plated iron, such as is used in the
manufacture of tin cans and cracker boxes.

The simplest method of securing good flat material is to get some old
scrap from a plumbing shop. An old cocoa tin or baking-powder can may,
however, be cut up and flattened and will then serve the purpose almost
as well.

[Illustration: FIG. 9.—Showing the Armature assembled on the shaft ready
for winding.]

*The Armature*—Two strips of tin, one-half of an inch by one and
one-half inches, are cut to form the armature. They are slightly longer
than will actually be necessary, but are cut to length after the bending
operations are finished. Mark a line carefully across the center of each
strip. Then taking care to keep the shape symmetrical so that both
pieces are exactly alike, bend them into the shape shown in Figure 8.
The small bend in the center is most easily made by bending the strip
over a knitting-needle and then bending it back to the required extent.

[Illustration: FIG. 10.—A front view of the Field Frame.]

A piece of knitting-needle one and seven-eighths inches long is required
for the shaft. Bind the two halves of the armature together in the
position shown in Figure 9. Bind them temporarily with a piece of iron
wire and solder them together. The wire should be removed after they are
soldered.

[Illustration: FIG. 11.—The completed Field Frame, ready for winding.]

*The Field Magnet* is made by first cutting out a strip of tin
five-eighths of an inch wide by five inches long and then bending it
into the shape shown in Figure 11. The easiest way of doing this with
the most accuracy is to cut out a piece of wood as a form, and then bend
the tin over the form. The dimensions shown in Figure 10 should be used
as a guide when making the form.

[Illustration: FIG. 12.—The Bearings.]

Two small holes should be bored in the feet of the field magnet to
receive No. 8 wood screws, the purpose of which is to fasten the field
to the base.

*The Bearings* are shown in detail in Figure 12. They are easily made by
cutting from sheet tin. Care should be taken to make the bearings
accurately so that the armature will be in the proper position when the
motor is assembled. Two small washers, serving as collars, should be
soldered to the shaft as shown in Figure 13.

*The Commutator Core* is formed by cutting a strip of paper
three-eighths of an inch wide and about five inches long. It should be
given a coat of shellac on one side and allowed to dry until it gets
sticky. The strip is then wrapped around the shaft until its diameter is
three-sixteenths of an inch. The sticky shellac should be sufficient to
hold the paper tightly in position when dry.

*The Base* is cut from any ordinary piece of wood and is in the form of
a block about two and one-half by one and seven-eighths by one-half
inches thick.

[Illustration: FIG. 13.—Side view of the Armature and Commutator Core
assembled on the Shaft before winding.]

*Assembling the Motor*—The parts must be carefully prepared for winding
by covering with paper. Cut a strip of paper five-eighths of an inch
wide and one and three-eighths inches long and give it a coat of shellac
on one side. As soon as it becomes sticky, wrap it around one of the two
upper vertical parts of the field magnet as indicated in Figure 11. Both
sides of the field should be insulated with paper in this manner. The
armature is insulated in exactly the same way, taking care that the
paper covers the entire flat portion.

The field and armature are now ready for winding. It is necessary to
take proper precautions to prevent the first turn from slipping out of
place.

The field should be wound first. This is accomplished by looping a small
piece of tape or cord over it at the point indicated by "A" in Figure
15. The next two turns are then taken over the ends of the loop so as to
embed them. Wind on three layers of wire on one side and then run the
wire across to the other side and wind on three layers there. The third
layer of wire in the second coil should end at "B." It should be
fastened into position by a loop of string so that it will not unwind.

[Illustration: FIG. 14.—Showing the Motor assembled on the Base so that
all the parts may be lined up before winding.]

This method divides the field winding into two parts, both of which are
connected together. The outside layer of the first coil is connected to
the inside layer of the second coil. The two coils really form one
continuous winding divided into two parts. After the winding is
finished, give it a coat of shellac.

The winding of the armature is somewhat more difficult. The wire used
for winding both the armature and the field should be No. 25 or No. 26
B. & S. Gauge double cotton-covered.

[Illustration: FIG. 15.—The Field Frame with the Winding in position.]

In order to wind the armature, cut off about seven feet of wire and
double it back to find the center. Then place the wire diagonally across
the center of the armature so that there is an equal length on both
sides. Place a piece of paper under the wire at the crossing point to
insulate it. Then, using one end of the wire, wind four layers on half
of the armature. Tie the end down with a piece of thread and wind on the
other half.

The ends of the wire are cut and scraped to form the commutator
segments. Figure 17 shows how this is done.

[Illustration: FIG. 16.—The Armature Winding before the Commutator is
completed.]

Bend the wires as shown so that they will fit closely to the paper core.
Bind them tightly into position with some silk thread. Use care so that
the two wires do not touch each other. Cut the free ends of the wire off
close to the core.

When finished, the relative positions of the armature and the commutator
should be as shown in Figure 17.

Figure 14 shows how the motor is assembled. The windings are not shown
for the sake of clearness. The armature should be exactly in the center
of the field. The bearing holes should be in the correct position and
should permit the armature to revolve freely.

[Illustration: FIG. 17.—The completed Armature showing how the
Commutator is constructed.]

The armature should not scrape against the field at any point, but
should clear it by about one-sixteenth of an inch.

The brushes are made by flattening a piece of wire by a few light hammer
blows.

The brushes are fastened under a small clamp formed by a strip of tin
held down at each end with a wood screw. They can be adjusted to the
best advantage only under actual working conditions when the current is
passing through the motor. One or two dry cells should be sufficient to
operate the motor.

The completed motor is shown in Figure 19.

One end of the winding is connected to one of the brushes. The other
brush and the other end of the field form the terminals to which the
battery is connected.

The motor, being of the two-pole armature type, must be started when the
current is turned on, by giving it a twist with the fingers.

[Illustration: FIG. 18.—Details of the Commutator.]

Put a drop of oil on the bearings, make sure that the brushes bear
firmly but not tightly against the commutator, connect the battery and
your motor is ready to run. It will spin at a high rate of speed.

[Illustration: FIG. 19.—The completed Motor.]



SIMPLEX MOTOR WITH THREE-POLE ARMATURE.


The form of "Simplex" motor which has just been described has only one
drawback which prevents it from being a first class motor in every
respect, namely, the armature has only two poles and the motor is
therefore not self-starting, but must be given a twist with the fingers
in order to start it rotating. A Two-pole armature is the easiest for
the young experimenter to make and that is the reason that it has been
described first.

All large power motors are provided with armatures having a large number
of poles so as to be self-starting and to give as steady a pull as
possible.

*The Armature*—The method of making a three-pole armature is practically
the same as that of making one having only two poles. Three strips of
tin, one-half an inch by one and one-half inches are necessary. They are
purposely made a little longer than is actually required in order to
form the armature and are cut to length after the finish of the bending
operations.

[Illustration: FIG. 20.—Details of the Three-pole Armature.]

Mark a line carefully across the center of each strip. Then bend them
into the shape shown in Figure 20, taking care to keep the shape
symmetrical so that all three pieces are exactly alike. The bend in the
center which must fit over the shaft is most easily made by bending the
strips over a knitting-needle and then bending them back the required
amount.

*The Shaft* is formed by a piece of knitting-needle, one and
seven-eighths of an inch long. Assemble the three pieces, forming the
armature, on the shaft as shown in Figure 21. Bind them temporarily
together with a piece of iron wire and then solder them along the edges.
The iron wire should be removed after they are soldered.

*The Commutator Core* is formed by cutting a strip of paper,
three-eighths of an inch wide and about five inches long. It should be
given a coat of shellac on one side and allowed to dry until it becomes
sticky.

[Illustration: FIG. 21.—The Three-pole Armature assembled on the shaft.]

The strip is then wrapped around the shaft until its diameter is
three-sixteenths of an inch. The sticky shellac should be sufficient to
hold the paper tightly in position when dry and to form a hard, firm
core.

The illustration in Figure 22 shows the position of the core on the
shaft in relation to the rest of the armature.

*The Winding of the Armature* may seem somewhat more difficult at first
than was the case with the two-pole armature, but it is really very
easy. The wire used for this purpose should be No. 25 or No. 26 B. & S.
Gauge, double cotton-covered. Single cotton-covered wire for this
purpose is liable to give trouble on account of short circuits.

In order to wind the armature, cut three pieces of wire about three and
one-half feet long. Wrap a strip of paper around each section of the
armature so that the sharp edges of the tin will not cut through the
insulation on the wire and then wind four layers of wire on each section
of the armature.

[Illustration: FIG. 22.—Showing the Armature and Shaft with the
Commutator Core in position.]

Each section should be wound in the same direction as the others. The
ends of the wires should be scraped free from insulation and connected
together as follows: Connect the outside end of one section to the
inside end of the next section. We will presume that the three sections
of the armature are lettered "A, B, and C." Connect the outside end of
"A" to the inside of "B"; the outside of "B" to the inside end of "C"
and the outside of "C" to the inside of "A."

Those portions of the wire forming the connections between the three
sections, are used to form the commutator segments, in the same manner
as the ends of the wires in the case of the two-pole armature, only in
this instance there are three sections to the armature.

[Illustration: FIG. 23.—Diagram showing how the coils are connected
together so as to form a continuous winding.]

Bend the wires so that they will fit closely to the paper core and bind
them tightly into position with some silk thread. A section of the
commutator should come opposite the space between each section of the
armature.

*The Field Magnet* is exactly like that used in making the Simplex motor
with the two-pole armature. It is made by first cutting out a strip of
tin five-eighths of an inch wide by five inches long and then bending it
into the shape shown in Figures 10 and 11. The easiest way of doing this
with reasonable accuracy is to cut out a piece of wood for a form and
then bend the tin over the form.

Two small holes should be bored in the feet of the field magnet so as to
enable the field to be fastened to the base.

The field is wound with the same size of wire used on the armature. The
winding is started by looping a small piece of tape or cord over the
frame at the point indicated by "A" in Figure 15. The next two turns are
then wound over the ends of the loop so as to hold them down. Wind on
three layers of wire on one side and then run the wire across to the
other side and wind on three layers there. The third layer of wire in
the second coil should end at B. It should be fastened in position by a
loop of string so that it will not unwind.

This method divides the field winding into two parts, both of which are
connected together. The outside layer of the first coil is connected to
the inside layer of the second coil. The two coils really form one
continuous winding divided into two parts. The illustration in Figure 23
should make this clear. After the winding is finished, give it a coat of
shellac.

*The Bearings* are shown in detail in Figure 12. They are easily made.
Care should be taken to make the bearings very accurate so that the
armature will be in the proper position when the motor is assembled.

Two small washers, serving as collars to bear against the inside of the
bearings and keep the armature in the field should be soldered to the
shaft as shown in Figure 13.

*The Base* is cut from any ordinary piece of wood and should be in the
form of a rectangular block about two and one-half inches by one and
seven-eighths inches wide, and one-half inch thick.

The completed motor is shown in Figure 24. Be sure that the armature
does not scrape against the field at any point but clears it by about
one-sixteenth of an inch all around. The brushes are fastened under a
small clamp made from a strip of tin held down at each end by a small
wood screw. The brushes are made by flattening the end of a piece of
copper wire with a few light hammer blows. The brushes can be best
adjusted under actual working conditions when the current is passing
through the motor.

One end of the field winding is connected to the brush marked "C," in
Figure 24. The other brush, "A" and the other end of the field winding,
"B," form the terminals to which the battery is connected. This forms
what is known as a series connected motor, because the armature and the
field are in series and the current must pass from one to the other.

[Illustration: FIG. 24.—The completed Three-pole Motor.]

After you have finished assembling the motor, put a drop of oil on the
bearings, make certain that the brushes are properly adjusted, connect
the battery, and your motor is ready to run. One or two dry cells should
furnish sufficient current to run the motor at high speed.



HOW TO MAKE THE SIMPLEX OVERTYPE MOTOR.


The method of construction which has been outlined in making the two
Simplex motors, just described, also lends itself to the construction of
many other simple and interesting forms of motors.

Figure 25 shows a form of motor which is essentially the same as that
shown in Figure 24 except that the field has been turned upside down and
the armature is at the top of the motor instead of the bottom.

[Illustration: FIG. 25.—The Simplex "Overtype" Motor.]

The detailed dimensions of the field are shown in Figure 26. It is made
by cutting out a. strip of tin five-eighths of an inch wide and five
inches long. This strip is then bent into the shape shown in Figures 26
and 27. This form of field is really very similar to that shown in
Figure 15 except that the two feet are omitted and it has been turned
upside down. The method of making ft is the same.

[Illustration: FIG. 26.—Details of the Field Frame for the "Overtype"
Motor.]

The field should be wound with either No. 25 or No. 26 B. & S. Gauge
double cotton-covered wire. It should be carefully prepared for winding
by a strip of shellaced paper around each of the two straight parts of
the field magnet where the winding is to be placed. Then proceed with
the winding in exactly the same manner as in the case of the field shown
in Figure 15.

The armature used is of the the three-pole type and is exactly the same
as that shown in Figures 20, 21 and 22.

[Illustration: FIG. 27.—Showing how the Field is Wound.]

The bearings will have to be made much higher on account of the armature
being higher than the base. The details of the bearings are shown in
Figure 28. They are cut out of sheet tin. Care should be taken to make
them accurately so that the armature will be in the proper position when
the motor is assembled.

The base is a block of wood two and one-half inches long, one and
seven-eighths of an inch wide and one-half inch thick.

The field is fastened to the base by four small wood screws. The exact
method of assembling the motor is probably best understood by studying
the illustration in Figure 25.

[Illustration: FIG. 28.—The Bearings.]



THE MANCHESTER MOTOR.


Those readers who have made the motors already described, are no doubt
anxious to proceed with the construction of some models which bear a
greater resemblance to the large motors commonly employed to furnish
power.

Figure 29 shows a motor of the "Manchester" type.

*The Field* of this machine is made from a strip of heavy sheet tin,
one-half inch wide and about six inches long, bent to shape and joined
in the center of the bottom pole piece, just above the pedestal. It is
best to cut the strip a little long and then reduce it to the exact
length required after the bending operations have been finished. The
illustration in Figure 30 shows the details and dimensions of the field.

The field should be bent into shape with the aid of a pair of pliers and
a wooden form, in the same manner employed in making the motors already
described.

[Illustration: FIG. 28.—The Manchester Motor.]

The field frame is supported by a "pedestal." The pedestal is formed by
another strip, one-half inch wide, soldered to the field at right
angles, underneath the joint in the lower pole piece.

The pedestal should be firmly soldered to the field, care being taken to
see that the solder runs well into the joints. Then bend the ends of the
pedestal down to form two "feet" as shown in the illustration. The feet
should be bent so as to bring the center of the armature tunnel
five-eighths of an inch above the base.

Two small holes should be bored in the pedestal, at each side, so that
the motor can be screwed fast to a wooden base.

[Illustration: FIG. 30.—Details of the Field Frame.]

*Winding the Field*—It will be necessary to proceed with the winding of
this motor in a slightly different manner from that followed in making
the other motors. The wire cannot be wound on as easily as before and it
will be necessary to wind the required length of wire onto a small spool
or bobbin, which can be passed through the field. Double cotton-covered
wire is the best for the purpose. Either No. 25 or No. 26 B. & S. Gauge
may be used. A strip of paper should be wrapped around the field frame
at all points where the wire is liable to touch, so as to guard the
insulation against possible abrasion.

Figure 32 shows the method which should be followed in winding the
coils. Both parts of the winding should be started at the bottom of the
field and wound in the direction indicated. "B" and "D" are the starting
ends Wind on three layers of wire in each coil. The terminals, "B" and
"C," should be connected together after the winding is finished.

*The Armature*—The method of making the armature is exactly the same as
that which has already been described. Three strips of tin, one-half
inch wide and one and one-half inches long are required. They are
purposely made slightly longer than is actually necessary and are cut to
length after the finish of the bending operations.

[Illustration: FIG. 31.—Details of the Field Pedestal.]

Mark a line carefully across the center of each of the three strips and
then bend them into the shape shown in Figure 20, making certain to keep
the shape symmetrical so that all three, pieces are exactly alike. The
bend in the center of each strip should fit nicely over the shaft. This
result is most easily reached by bending the strips over a
knitting-needle and then bending them back the required amount.

[Illustration: FIG. 32.—Showing how the Field Coils are Wound.]

*The Shaft* is a piece of knitting-needle one and seven-eighths of an
inch long. Assemble the three strips on the shaft as shown in Figure 21
and bind them temporarily together with a piece of iron wire. Then
solder the edges together and remove the wire.

*The Commutator Core* is formed of a strip of paper, three-eighths of an
inch wide and about five inches long, wrapped around the shaft until the
diameter of the small cylinder thus formed is three-sixteenths of an
inch. The paper strip should be given a coat of shellac on one side and
allowed to dry until it becomes sticky before it is wrapped around the
shaft. The sticky shellac should be sufficient to hold the paper tightly
in position when dry and to form a hard, firm core when dry.

*The Winding of the Armature* is not difficult. The size of the wire
used should be No. 25 or No. 26 B. & S. Gauge, double cotton-covered.

Wrap a strip of paper around each section of the armature so that the
wire will be protected from any sharp edges on the tin which might cut
through the insulation.

Wind four layers of wire on each section of the armature. Each section
should be wound in the same direction as the others. The terminals of
the wires should be scraped clean and connected together in the
following manner: Connect the outside end of one section to the inside
end of the next section. We will presume that the three sections of the
armature are lettered "A", "B" and "C." Connect the outside end of "A"
to the inside of "B"; the outside of "B" to the inside end of "C" and
the outside end of "G" to the inside of "A."

The portion of the wires forming the connections between the three
armature coils are used to form the three sections of the commutator.

Bend the wires so that they will fit closely to the paper core and bind
them tightly into position with silk thread.

*Two Bearings* are required to support the armature. They are cut out of
sheet iron or brass and are shown in detail in Figure 12. Extra care
should be exercised in making the bearings to insure their accuracy so
that the armature will be in the proper position when the motor is
assembled and run freely.

Two small washers or wire rings, to serve as collars and keep the
armature in the center of the field, should be soldered to the shaft as
shown in Figure 22.

*The Base* is a square block of wood, two and one-half inches wide, two
and one-half inches long and three-eighths of an inch thick.

The completed Manchester motor is shown in Figure 29. The brushes are
made by flattening the ends of two pieces of copper wire. Each brush is
fastened under a small clamp made from a strip of tin held down at each
end by a small round-headed wood screw.

Be sure that the armature is exactly in the center of the field, does
not scrape at any point and turns perfectly freely.

The armature and the field windings should be connected in series. The
terminals of the field marked "B" in Figure 32 should be connected to
the brush clamp marked "C" in Figure 29. The terminal of the field
marked "C" in Figure 32 forms one terminal of the motor. The other is
the brush clamp "A."

Oil the bearings of the motor, adjust the brushes and it will be ready
to run.




CHAPTER III. A Magnetic Attraction Motor. A Motor Having a Laminated
Field and Armature Frame. How to Make an Experimental Induction Motor.
How to Make an Electric Engine.



A MAGNETIC ATTRACTION MOTOR.


This motor differs from those which have already been described, in that
no wire is wound on the armature.

*The Field Coils* consist of two electro-magnets wound upon iron cores
one and one-eighth inches long and five-sixteenths inches in diameter.
Each core is fitted with two fibre heads, one-sixteenth of an inch thick
and seven-eighths of an inch in diameter so as to form a bobbin as shown
in Figure 33. The bobbins are wound with No. 22 B. & S. Gauge single
cotton-covered magnet wire. The magnets are connected in series so that
the current flows through them in opposite directions.

[Illustration: FIG. 33.—Details of the Magnet Bobbins.]

*The Armature* is a strip of soft iron one and three-quarters inches
long, three-eighths of an inch wide and three thirty-seconds thick. A
one-eighth inch hole bored through the center of the armature and the
latter forced upon a shaft one and seven-eighths inches long.

The lower end of the shaft is pointed and rests in a small hole in the
magnet yoke, half way between the two coils.

The magnet-yoke is a strip of soft Iron or steel two and one-half inches
long, seven-eighths inches wide and one-eighth of an inch thick.

[Illustration: FIG. 34.—The completed Electromagnets mounted on the
Yoke.]

The magnets are mounted on a wooden base, five inches long, three inches
wide and three-eighths of an inch thick, by means of two 8-32 machine
screws which pass upward from the bottom of the base into the bottom of
the magnets. The yoke is placed under the’ magnets, between them and the
base. The screws pass through two holes, one and one-eighth inches
apart.

The armature is supported in position over the electromagnets by means
of a standard bent out of a strip of sheet brass. The details of the
standard are shown in Figure 36. The standard is fastened to the base by
means of two small wood screws.

[Illustration: FIG. 35.—Details of the Armature Shaft.]

The armature should just clear the top of the electromagnets when the
lower end of the shaft is resting in the socket in the yoke. The shaft
should be perfectly vertical and revolve freely without friction.

The lower end of the shaft carries a small brass contact which is forced
into position. The exact shape and dimensions of this contact are shown
in Figure 37. The holes through the center should be slightly smaller
than the diameter of the shaft, so that when the contact is forced into
position it will remain secure and not move.

*The Brush* which bears against the contact is illustrated in Figure 38.
This is cut out of spring copper or brass and made according to the
shape and dimensions shown in the illustration. The brush is fastened to
the base by means of a round-headed brass wood screw.

The proper method of assembling the motor and its appearance when
finished are best understood from the illustration in Figure 39.

[Illustration: FIG. 36.—Details of the Standard which forms the upper
bearings.]

*The Binding Posts* consist of machine screws provided with hexagonal
nuts and thumb screws, such as that supplied on dry batteries. One
binding post passes through the end of the brush and connects with it.
The other binding post is mounted at the left hand forward corner of the
base. One terminal of the electromagnets leads to this binding post. The
other terminal is placed under the head of one of the screws which hold
the standard to the base.

[Illustration: FIG. 37.—The Brass Contact.]

The contact and the brush will have to be most carefully adjusted before
the motor will run. The tip of the contact should make contact with the
brush just before the armature starts to swing over the electromagnets
and break the circuit just as the armature is actually over. The exact
position will have to be found by a little experimenting. It is very
necessary that the brush should be so adjusted that it only touches the
ends of the contact as it swings around.

[Illustration: FIG. 38.—The Brush which bears against the Contact.]

[Illustration: FIG. 39.—The completed Magnetic Attraction Motor.]

The operation of the motor is very simple. When a battery is connected
to the binding posts the circuit is not complete so that the coils are
magnetized and can attract the armature until the contact touches the
brush. When the contact and the brush touch, however, the circuit is
completed and the armature will be drawn toward the electromagnets. As
soon as it reaches a position over the ends of the cores, the circuit
should be broken so that the momentum will carry the armature past and
around into such position that the opposite end of the contact touches
the brush and the operation is repeated.

A magnetic attraction motor of this type will usually have to be started
by giving the shaft a twist with the fingers.



HOW TO CONSTRUCT A MOTOR HAVING A LAMINATED ARMATURE AND FIELD FRAME


It is an easy matter to make a strong electric motor suitable to operate
on batteries by the exercise of a little careful workmanship.

[Illustration: FIG. 40.—The completed Electric Motor.]

The field frame and armature of the motor shown in Figure 40 are
laminated, that is, built up of separate sheets of iron. They may be
made out of sheet tin or ordinary stove pipe iron. The cheapest and
simplest method of securing good flat material is to get some old scrap
from a tinner’s or plumbing shop.

*The Details of the Field* are shown in Figure 41. The exact shape and
dimensions can be understood by reference to the illustration. Lay out
one lamination very carefully as a pattern. Cut it out and smooth up the
edges, making certain that it is perfectly true to size and shape. Then
use it as a template to lay out the other laminations by placing it on
the metal and scribing a line around the edges with a sharp pointed
needle. Enough laminations should be cut out to make a pile five-eighths
of an inch high when tightly pressed together.

[Illustration: FIG. 41.—Details of the Field Frame.]

*The Armature* is made in exactly the same manner as the field frame,
that is, by cutting out a pattern according to the shape and dimensions
shown in Figure 43 and using it as a template to lay out the other
laminations. Enough should be cut to make a pile five-eighths of an inch
high when tightly squeezed together.

The armature is one and three-sixteenths inches in diameter. The hole in
the field frame which accommodates the armature is one inch and
one-quarter in diameter so that there is a space in between for the
armature to revolve in.

The hole through the center for the shaft should be of such diameter
that the laminations will force very tightly on a shaft one-eighth of an
inch in diameter. The laminations should be very carefully flattened and
then forced over the steel shaft which is two and one-eighth inches
long. Clean up all the rough edges with a file and smooth the outside so
that it will revolve properly in the field without scraping.

Figure 44 illustrates the armature assembled on the shaft and ready to
be wound.

*The Armature Windings* consist of four layers of No. 22 B. & S. Gauge
double cotton covered magnet wire wound around each leg. The iron should
be very carefully insulated with shellaced paper before the wire is put
in position so that there will not be any danger of short circuit due to
the sharp edges of the metal cutting through the insulation. Each leg
should contain the same number of turns of wire and all should be wound
in the same direction.

[Illustration: FIG. 42.—The Assembled Field ready for Winding.]

*The Commutator* is illustrated in Figure 45. It consists of a piece of
brass tubing seven-sixteenths of an inch long, five-sixteenths inside
and three-eighths of an inch outside. It should be forced onto a piece
of fibre five-sixteenths of an inch in diameter and seven-sixteenths of
an inch long. Split the tube, into three equal parts by dividing it
longitudinally with a hacksaw. Make a fibre ring which will force onto
the tube very tightly when it is in position on the fibre core and so
hold the three commutator sections firmly in position. The sections
should be arranged so that there is a small space between each two and
they are perfectly insulated from each other. The fibre core should have
a one-eighth inch hole through the center so that it may be forced
tightly onto the shaft and up against the armature after the windings
are in position. The commutator should be in such a position that the
split between each two sections comes directly opposite the centre of
each winding. Suppose that the windings are lettered "A", "B", and "C",
the commutator section between "A" and "B" is numbered 1, that between
"A" and "C" is No. 2, and the one between "C" and "B" is No. 3. Then the
inside terminal of "B" is connected to the outside terminal of "A" and
soldered to the end of commutator section No. 1 close to the winding.
The inside end of "B" is connected to the outside terminal of "C" and to
commutator section No. 2. The inside end of winding "C" is connected to
the outside of "B" and to commutator section No. 3. The connection of
the armature windings to the commutator are represented by the diagram
in Figure 45.

[Illustration: FIG. 43.—Details of the Armature Laminations.]

*The Field Winding* consists of five layers of No. 18 B. & S. double
cotton covered wire. A much neater job may be made of this part of the
work if two fibre heads are cut to slip over the field and support the
ends of the winding as shown in the illustration in Figure 40.

[Illustration: FIG. 44.—The Armature assembled on the Shaft ready to
Wind.]

*The Bearings* are illustrated in Figure 46. They are made out of
three-eighths inch brass strip one-sixteenth of an inch thick by bending
and drilling as shown in the illustration. The location of the holes is
best understood from the drawing. The larger bearing is assembled on the
field at the side towards the commutator.

Assembling the motor is a comparatively easy matter if it is done
properly and carefully. The bearings are mounted on the field frame by
screws passing through the holes "B" and "B" into a nut on the outside
of the bearing at the opposite side of the field.

The armature should revolve freely without binding and without any
danger of scraping against the field. Slip some small fibre washers over
the ends of the shaft between the armature and the bearings so as to
take up all end play.

*The Brushes* are made of spring copper according to the shape and
dimensions shown in Figure 47. They can be cut out with a pair of snips.

Each brush is mounted on a small fibre block supported on the large
motor bearing. The holes marked "A" and "C" in the illustration should
be threaded with a 4-36 tap. The hole "B" should be made one-eighth of
an inch in diameter and drilled all the way through the block.

The holes, "A" and "C" are used to fasten the blocks to the bearing. The
brushes are fastened to the blocks by means of a 6-32 screw with a nut
on the lower end.

*The Base* is a rectangular block, three inches wide, three and one-half
inches long and three-eighths of an inch thick. The motor is fastened to
the base by four small right angled brackets bent out of strip brass and
secured to the field frame by two machine screws passing through the
holes, "H" and "H", into a nut at the opposite end.

[Illustration: FIG. 45—The Commutator and Method of connecting the
Armature Coils.]

One terminal of the field winding is connected to a binding post mounted
on the base. The other terminal of the field is connected to the right
hand brush. The end of the wire should be placed under the head of the
screw which holds the brush to the fibre block. The brush should be on
the under side of the block so that it bears against the under side of
the commutator.

[Illustration: FIG. 46.—The Bearings.]

The left hand brush bears against the upper side of the commutator and
is connected to a second binding post on the base of the motor. This
makes it a "series" motor, that is, the armature and the field are
connected in series.

[Illustration: FIG. 47.—Brush and Supporting Block.]

The motor is now ready to run. Put a drop of oil on each bearing and
make certain that the curved portion of the brushes bear firmly against
the centre of the commutator on opposite sides. The armature having
three poles, should start without assistance and run at high speed as
soon as the current-is applied. Two cells of dry or other battery should
be sufficient. The motor may be fitted with a small pulley so that its
power may be utilized for driving small models.



HOW TO MAKE AN EXPERIMENTAL INDUCTION MOTOR.


A motor having a three-pole armature will run on alternating current as
well as on direct current and can be operated on the 110 volt A. C.
current in series with a suitable resistance. The average experimenter
is probably aware of this but did you know that it can also be operated
on alternating current as an *induction motor* and that it will then run
*without brushes* and without current being led into the armature?

In order to make an induction motor out of an ordinary three-pole
battery motor such as that shown in Figure 48 it is merely necessary to
remove the brushes and bind a piece of bare copper wire around the
commutator so that it short circuits the segments.

The alternating current should be led into the field coil. A step down
transformer will prove very useful for producing a low voltage
alternating current which may be connected directly to the field coil.
If a transformer is not available, the 110 v. alternating current can be
used, provided that a proper resistance such as a lamp bank, be placed
in series with the motor.

If the current is turned on and the armature is then speeded up by
giving it a couple of sharp twists, or winding a string around the shaft
and then pulling it as one would spin a top, the motor will continue to
revolve at a good rate of speed.

[Illustration: FIG. 48.—A well known Three-pole Battery Motor.]

It may prove easier to start the motor if the armature is speeded up
before the current is turned on. As soon as a good speed is reached,
turn on the current and the armature should continue to run.

Commercial induction motors are self starting, and are provided with a
hollow armature, which contains a centrifugal governor. When the motor
is at rest or starting, four brushes press against the commutator and
divide the armature coils into four groups. After the motor has attained
the proper speed the governor is thrown out by centrifugal force and
pushes the brushes away from the commutator. At the same time a metal
ring is pressed against the interior of the commutator, short circuiting
all the sections and making each coil a complete circuit of itself.

It would be very difficult to provide a small three-pole toy motor with
such a governor and short-circuiting device in order to make it
self-starting.

It is however possible to accomplish this in another way, by a very
simple device.

This consists in providing the armature with another set of coils for
use in starting only. The brushes are allowed to remain on the motor but
are only used for starting. The leads of the armature winding are
removed from the commutator and are all connected together. Then two or
three layers of wire are wound over the coils to form new coils which
are similar to the old ones but smaller.

[Illustration: FIG. 49.—Showing how a Three-pole Motor may be provided
with "Starting Coils" and connected to form an Experimental Induction
Motor.]

These new coils are connected to the commutator in the same way as the
old ones were before being removed, just as if the motor was to be used
in the ordinary manner.

A two-point switch will be necessary in order to complete the
arrangements. The connections should be made as in Figure 49. The switch
should be thrown to the right, on contact A, for starting so that the
current flows through the field and through the extra coils on the
armature in the ordinary way. As soon as the motor has reached its
speed, throw the switch to the left so that the current flows through
the field only and the motor will continue to run by induction.



HOW TO BUILD AN ELECTRIC ENGINE


An electric engine is really a form of electric motor but differs from
the most common form of the latter in that the armature, instead of
revolving, oscillates back and forth, like the piston of a steam or
gasoline engine. Electric engines are not as efficient as electric
motors from the standpoint of the amount of power delivered in
proportion to the current used, but they make very interesting models
and the young experimenter will derive fully as much pleasure in
constructing one as from the construction of an electric motor.

[Illustration: FIG. 50.—The completed Engine.]

Various forms of electric engines were made before the first practical
electric motor was invented. They amounted to little more than
curiosities however, and could only be used where the expense of
electric current was not to be regarded.

The engine illustrated in Figure 50 is of the double action type. It is
provided with two electromagnets arranged so that one pulls the armature
forward and the other pulls it back. The motion of the armature is
transmitted to the shaft by means of a connecting rod and crank. It is
very simple to build and the design is such that it will operate equally
well whether it is made large or small. If you do not happen to have all
the necessary materials to build an engine according to the dimensions
shown in the drawings, you can make it just one-half that size, and it
will work equally well although it will, of course, not give as much
power.

[Illustration: FIG. 51.—The Base.]

The complete engine is shown in Figure 50. All the various parts have
been marked so that you can easily identify them in the other drawings.
It is well to study this illustration carefully so that you will
understand just how all the parts are arranged.

*The Base* is illustrated in Figure 51. It is made of a piece of
hardwood, seven inches long, three and one-half inches wide, and
one-half an inch thick.

*The Electromagnets* will largely determine the dimensions of the rest
of the engine. The magnets shown in Figure 52 are made of three-eighths
inch round iron two and one-half inches long, provided with two fibre
washers one and one-eighths inches in diameter. On end of each of the
steel cores is drilled and tapped to received an 8-32 screw. The
experimenter may possibly be able to secure some old magnet cores fitted
with fibre heads from an old telephone bell or "ringer" as they are
sometimes called. A suitable bolt may be made to serve the purpose by
cutting it off to the right dimensions with a hack saw. If a drill and
tap are not available for drilling and tapping the end so that the core
can be properly mounted in the frame of the engine, it is possible, to
use the threaded portion of a bolt to good advantage, by the exercise of
a little ingenuity. The hole in the frame should then be made larger so
that the end of the bolt will slip through, instead of an 8-32 screw and
the core clamped in position by a nut on each side.

The fibre washers are spaced two and one-sixteenth inches apart. The
space in between should be wound full of No. 18 B. & S. Gauge cotton
covered magnet wire. Before winding in the wire, cover the core with a
layer of paper so that the wire does not touch the metal. The ends of
the wire should be led out through small holes in the fibre heads.

[Illustration: FIG. 52.—Details showing the size of the Magnet Bobbin.]

It is not absolutely necessary to use No. 18 B. &.S. Gauge wire in
winding the magnets, but it is the size which will give the best results
on the average battery. If you use larger wire, the engine will require
more current from the battery. If you use finer wire, a battery of
higher voltage will be necessary. The current consumption will, however
be less.

The electromagnets are mounted in the frame of the engine by means of
two screws passing through the holes E and D. The details of the frame
are illustrated in figure 53. It is made of a strip of wrought iron or
cold rolled steel, five and five-eighths inches long, an inch and
one-eighth wide and one-eighth inch thick.

The material for making this part of the engine and also the bearings
can best be obtained at some blacksmith shop or hardware store. Heavy
galvanized iron can be used but it is not usually thick enough, and it
may be necessary to use two thicknesses. The ends of the strip are
rounded and bent at right angles so as to form a U-shaped piece with
sides one and three-quarters inches high.

The holes, "D" and "E", should be large enough to pass an 8-32 screw.
The holes, "A", "B" and "C" should be about one-eighth of an inch in
diameter. They are used to pass the screws which hold the frame of the
engine to the wooden base.

[Illustration: FIG. 53.—The Frame which supports the Electromagnets.]

*The Bearings* are shown in Figure 54. They are made U-shaped and are
out of a strip of iron or steel in the same manner as the frame of the
engine, but are three-quarters of an inch wide instead of an inch and
one-eighth. The dimensions will be understood best by referring to the
drawing. The 3/32 inch holes near the top of each side are the bearing
holes for the end of the shaft.

The one-eighth inch holes just below are used to fasten the brush holder
in position. The holes in the bottom serve to fasten the bearings to the
base.

[Illustration: FIG. 54.—The Main Bearings.]

*The Shaft* will probably prove the most difficult part of the engine to
make properly. The details are given in Figure 55. It is made of a piece
of one-eighth inch steel rod bent so that a crank is formed in the
middle. The crank should be bent so that it has a "throw" of one-half an
inch, that is, offset one-quarter of an inch so that the connecting rod
moves back and forth a distance of one-half an inch. The finished shaft
should be three inches long. The piece of steel used should be longer
than this and so that it can be cut off to exact dimensions after the
shaft is finished. A second crank should be bent in one end of this so
as to form an offset contact for the brushes. This second crank will
have to be at right angles to the first one and should be much smaller.
The ends of the shaft are turned or filed down to a diameter of
three-thirty-seconds of an inch for a distance of about the same amount
so that they will fit in the bearing holes and turn freely, but not
allow the shaft to slip through. The work of making the shaft will
require a small vise, a light hammer, files and a couple of pliers. One
pair of pliers should be of the round nosed type and the other a pair of
ordinary square jawed side cutters. It may require two or three attempts
before a perfect shaft is secured. When finished, it should be perfectly
true and turn freely in the bearings. The bearings can be adjusted
slightly by bending, so that the shaft will fit in the holes and be
free, but yet not loose enough to slip out.

*The Armature* is a strip of soft iron, two and one-eighth inches long,
seven-sixteenths of an inch wide and three-sixteenths of an inch thick.
A one-sixteenth inch slot, three-eighths of an inch long is cut in one
end. A one-sixteenth inch hole is drilled through from one side to the
other, one-eighth of an inch from each end. The hole which passes
through the slot is used tu pass the pin which pivots the armature to
the connecting rod. The other hole is used to mount the armature in its
bearing. The armature bearing is a small edition of the one which is
used to support the engine shaft. The details and the dimensions are
given in the lower left hand side of Figure 56. The armature is shown in
the center of the same illustration. The connecting rod is illustrated
at the right. This is made from a strip of three-sixty-fourths inch
brass, three sixteenths of an inch wide and one and five-eighths inches
long. The one-eighth inch hole should be drilled close to one end and a
one-sixteenth inch hole close to the other.

[Illustration: FIG. 55.—The Shaft.]

*The Brushes* are two strips of thin phosphor bronze sheet, two and
three-sixteenths inches long and nine thirty-seconds of an inch wide.
They are illustrated in Figure 57. The block upon which they are mounted
is hard fibre. It is one and five-eighths inches long and three-eighths
of an inch square.

It may be possible to secure a flywheel for the engine from some old
toy. It should be about three and one-half inches in diameter. A
flywheel can be made out of sheet iron or steel by following the
suggestion in Figure 58, which shows a wheel cut out of one-eighth inch
sheet steel. It is given the appearance of having spokes by boring six
three-quarter inch holes through the face as shown. The hole in the
center of the wheel should be one-eighth of an inch in diameter. The
wheel is slipped over the shaft and fastened in position by soldering.

The parts are now all ready to assemble into the complete engine. Mount
the electromagnets in the frame and fasten the frame down to the wooden
base so that one end of the frame comes practically flush with the left
hand edge of the base. Fasten the bearing across the frame at right
angles by a screw passing through the center hole in the bottom of the
bearing through the hole A and into the base. The bottom of the bearing
should be bent slightly so as to straddle the frame. The bearing should
be secured and prevented from turning or twisting by two screws passed
through the other two holes in the bottom Use round headed wood screws
in mounting the bearing and the frame.

[Illustration: FIG. 56.—Showing the Armature, Armature Bearing and the
Connection Rod.]

The armature bearing should be mounted on the frame directly between the
two electromagnets. Then place the armature in position by slipping a
piece of one-sixteenth inch brass rod through the bearing holes and the
hole in the lower part of the armature.

Solder the flywheel in position on the shaft and snap the latter into
the bearings. Adjust the bearings so that the shaft will turn freely.
The connecting rod should be slipped over the shaft before it is placed
in the bearings. Fasten the other end of the connecting rod to the
armature by means of a piece of one-sixteenth inch brass rod which
passed through the small holes bored for that purpose. When the flywheel
is spun with the fingers, the armature should move back and forth
between the two electromagnets and almost, but not quite, touch the two
magnet poles.

[Illustration: FIG. 57.—Details of the Brushes and Brush Holder.]

All the moving parts should be fitted firmly together but be free enough
so there is no unnecessary friction and so that the engine will continue
to run for a few seconds when the flywheel is spun with the fingers.

The brushes, supported on their fibre blocks, should be mounted on the
bearing by means of two screws passing through the holes in the bearing
into the block. The position of the brushes should be such that the
shaft passes between the two upper ends but does not touch them unless
the small "contact" crank mentioned above is in proper position to do
so. The proper adjustment of the brushes so that they will make contact
with the shaft at the proper moment will largely determine the speed and
power which the finished engine will develop.

[Illustration: FIG. 58.—Showing how a Flywheel may be made out of sheet
iron.]

Two binding posts should be mounted on the right hand end of the base so
that the engine can be easily connected to a battery. Connect one
terminal of the right hand electromagnet to one of the binding posts.
Run the other terminal of the electromagnet to the brush on the opposite
side of the shaft. Connect one terminal of the left hand electromagnet
to the other binding post and run the other terminal to the brush on the
opposite side of the shaft. Save for a few minor adjustments, the engine
is now ready to run. Connect two or three cells of dry battery to the
two binding posts and turn the flywheel so that it moves from right to
left across the top. Just as the crank passes "dead center" and the
armature starts to move back away from the left hand magnet, the small
contact crank on the shaft should touch the left hand brush and send the
current through the right hand magnet. This will draw the armature over
to the right. Just before the armature gets all the way over to the
right, the contact should break connection with the left hand brush and
interrupt the current so that the inertia of the flywheel will cause it
to keep moving and the armature to start to move over toward the left
hand magnet at which point the contact on the shaft should commence to
bear against the right hand brush, thus throwing the left hand magnet
into circuit and drawing the armature over to that side. If the brushes
and the cranks are in proper relation to each other the engine will
continue to repeat this operation and gradually gain speed until it is
running at a good rate.

The appearance of the engine can be improved by painting the metal parts
black and the flywheel red. The magnets can be wrapped with a piece of
bright red cloth to protect the wire against injury and also lend
attraction to its appearance in this way.




CHAPTER IV SMALL POWER MOTORS


In order for a motor to develop any appreciable amount of power it must
be much larger than any of those which have been described in these
pages so far, and must be constructed in a most painstaking manner. It
will be necessary to use a great deal more iron in the field and
armature and also to make the space between them as small as possible. A
motor having a small separation between the field poles and the armature
will develop more power than one having a greater separation.

[Illustration: FIG. 59.—A Vertical Battery Power Motor.]

The most efficient types of small power motors have laminated field and
armature frames, that is, they are built up of a large number of thin
metal punchings. The amateur experimenter who has limited facilities for
carrying out his work would find it difficult to make parts of this sort
to good advantage and so the motors described here have been designed
with cast iron armatures and field frames.

Those who wish to secure a set of castings from their own patterns can
possibly save part of the expense if they do not consider the extra
labor of first making the patterns.

Two types of motors are described, one vertical and the other
horizontal. Both are intended to operate on a battery current of 3-6
volts and if carefully built will deliver a surprising amount of power.

[Illustration: FIG. 60.—Details of the Field Frame of the Vertical
Motor.]



A VERTICAL POWER MOTOR


*The Field Frame* is shown in detail in Figure 60. The exact shape and
dimensions are best understood by a careful examination of the drawing.

The pattern for the field may be made of the same shape and practically
the same size as indicated for the finished casting because the
"rapping" or jarring which the pattern will receive in the foundry in
order to free it from the sand mould will enlarge the mould sufficiently
in a casting of small size to make up for any shrinkage which takes
place upon the cooling of the iron.

The only exception to this is in the tunnel where the armature rotates.
This should measure one and three-quarter inches in diameter when
finished and should be slightly smaller in the rough casting so that
there is enough material to allow for truing and bringing to equal size.

*The Armature* may be of two types, three pole or six pole. The
three-pole armature is the simpler, but the six-pole type is the
smoother running and gives the steadier power. The details and
dimensions are shown in Figures 61 and 62. One of the armatures should
be selected and a pattern built.

[Illustration: FIG. 61.—Three-pole Armature.]

After the patterns are finished they should be given a coat of shellac
and carefully rubbed with fine sandpaper so that they are perfectly
smooth. Otherwise the sand is liable to stick in moulding and produce an
imperfect casting.

Castings may be obtained from any foundry which is equipped to make grey
iron castings. They should be as soft as possible. The cost will depend
upon the quantity which are ordered. If only one set is required, the
charge will probably be based upon the time required for making the
moulds but if several sets are ordered the price may be based upon the
weight.

After the castings have been received from the foundry, the first
operation is to carefully remove all rough spots and burrs with a file.

Those who have a lathe or large drill press can easily finish the tunnel
by turning or reaming. In the absence of these facilities, hand filing
can be made to suffice, if carefully done.

The holes marked "BBBB" should be drilled with a No. 29 drill and tapped
8-32. These holes must be very carefully located because they serve to
fasten the bearings. Each hole should be exactly opposite the other, two
and five-sixteenth inches apart and on a line passing exactly through
the centre of the tunnel.

The holes, "PP" and "SS", are three-sixteenths of an inch in diameter.
The former support the Binding Posts and the latter pass the screws
which fasten the motor to the wooden base.

[Illustration: FIG. 62.—Six-pole Armature.]

The armature, in the case of either the six or three pole type, has a
three-sixteenth inch hole drilled along the axis to accommodate a steel
shaft of the same diameter.

The armature casting should be accurately turned to a diameter of one
and twenty-three thirty-seconds of an inch so that it will revolve in
the tunnel without touching the field but still be very close to it.

Two holes bored through one of the pole pieces at right angles to the
shaft with a No. 37 drill and threaded with a 6-32 tap will allow the
armature to be clamped tightly to the shaft with two headless set
screws.

*The Field Winding* consists of No. 16 double cotton insulated wire.
Before the winding is put on, the core should be insulated with one or
two layers of shellaced paper. Two circular pieces of shellaced paper
should be placed against the flanges at the end of the core, so that the
winding space is thoroughly insulated and there is no liability of the
wire touching the iron at any point. The wire should be wound in smooth
even layers. The winding space is completely filled. The outside layer
may be finished by a coat of shellac.

The three-pole armature is much easier to wind than the six pole type.
The wire used should be No. 24 B. & S. Gauge, double cotton covered.
Before the wire is wound on, cover the winding space with shellaced
paper so that the wire will not touch the iron at any point. Each coil
should be wound in the same direction as the others starting at the same
end and as close as possible to the inside.

[Illustration: FIG. 63.—Showing how the Coils on a Three-pole Armature
are connected to the Commutator.]

The outside end of each coil should be connected to the inside of the
next coil as shown in Figure 63. The diagram indicates only one layer of
wire in each coil for the sake of clearness.

The winding upon the armature shown in Figure 64 is divided into six
coils. Each coil consists of as many turns as possible of No. 24 B. & S.
Gauge, cotton covered wire to fill the space completely and all coils
are wound in the same direction. The illustrations show the various
stages of the bindings with the two, four and six coils in place. The
winding spaces on the armature should be carefully insulated with
shellaced paper before the coils are placed in position.

After the winding has been finished the next step is to make the shaft
and commutator. The shaft is a piece of three-sixteenths steel, three
and one-quarter inches long. The shaft passes through the centre of the
armature and is locked-in position by the two set screws.

*The Commutator* is probably one of the most difficult parts of the
motor to make. It consists of three circular brass sections insulated
from one another on a fibre bushing.

The fibre bushing is a hollow cylinder, five-sixteenths of an inch in
diameter and seventeen thirty-seconds of an inch long. The bushing
should force tightly on the shaft. The segments are make by turning a
piece of three-quarter inch brass rod in a lathe until it is one-half an
inch in diameter for a distance of about seven-sixteenths of an inch. A
five-sixteenths inch hole should be bored through the center so that it
will fit tightly upon the fibre bushing.

[Illustration: FIG. 64.—Showing how the Coils on a Six-pole Armature are
arranged and connected.]

Then cut the brass off one-half inch from the end so that it leaves a
flange at one end, three-quarters of an inch in diameter. Saw it
lengthwise into three equal parts and mount it upon the fibre bushing
with a small strip of mica between each two sections to fill in the
space made by the saw cuts. The sections are held together by a fibre
ring, three quarters of an inch in diameter outside and one-half an inch
in diameter inside. The ring should fit very tightly over the commutator
and be forced down flush against the shoulder. After the ring is in
position, file any mica which may project out of the slots down even
with the surface of the segments and force the commutator onto the shaft
with the shoulder against the armature. The commutator must fit very
tightly so that there is not any possibility of moving it after it is in
position.

[Illustration: FIG. 65.—Details of the Commutator.]

The sections should bear a certain relative position to the armature
windings. The diagrams in Figures 63 and 64 show the proper position for
the three and six pole armature respectively.

The coils are connected to the commutator by soldering the terminals to
the shoulder on each segment. This work should be very carefully done so
as to insure a neat job and connection of the proper terminal to the
proper section.

[Illustration: FIG. 66.—Details of the Bearings, Shaft, and Pulley.]



CONNECTIONS FOR THE THREE POLE ARMATURE


The inside terminal of coil A and the outside terminal of coil B should
be connected to Section 1, the inside terminal of coil B and the outside
terminal of coil C should be connected to Section 3, the inside terminal
of coil C, and the outside terminal of coil A should be connected to
Section 2.



CONNECTIONS FOR THE SIX-POLE ARMATURE


The inside terminal of coil A and the inside terminal of coil B should
be connected to section 2, the outside terminal of coil C and the
outside terminal of coil D should be connected to Section 3, the outside
terminal of coil E and the outside terminal of coil F should be
connected to Section 1, the outside terminal of coil A and the inside
terminal of coil C should be connected to Section 1, the inside terminal
of coil D and the inside terminal of coil E should be connected to
Section 2, the inside terminal of coil F and the outside terminal of
coil D should be connected to Section 3.

[Illustration: FIG. 67.—The Brushes and Brush Holder.]

The wires leading from the coils to the commutator should be just as
short as it is possible to make them and after being soldered should be
bound down tightly with linen thread or string.

The bearings are both cast from brass. The details are shown in Figure
66 It will be necessary to make up wooden patterns and send them to a
foundry. The location of the holes can be ascertained from the
illustration.

[Illustration: FIG. 68.—Details of the Field Frame for the Horizontal
Power Motor.]

Each of the brushes consists of a piece of strip copper, one-quarter of
an inch wide and one and three-eighths inches long mounted in a brush
holder made of one-quarter inch brass rod. The brush holder is one inch
long and is turned down to a diameter of one-eighth of an inch at one
end for a distance of nine-sixteenths of an inch and then threaded with
a 6-32 die. The opposite end is slotted to receive the brush. The
threaded portion of the holder is slipped through the holes, "B and B",
in the bearing and prevented from making contact with the latter by a
fibre bushing.

[Illustration: FIG. 69.—Front view of the Field Frame.]

[Illustration: FIG. 70.—The Field Magnet Bobbin.]

A fibre washer should also be slipped over the holder on each side of
the bearing. Two hexagonal nuts are placed on the threaded stem. One
serves to clamp the holder in position and the other to hold the wire
used to make connection with the brush. The right hand brush should bear
against the under side of the commutator and the left hand brush against
the upper side.

After the armature has been assembled in the bearings and mounted on the
field frame it should revolve freely without friction and without any
possibility of its striking against the field poles.

The binding posts are mounted in the holes, "PP" in the lower parts of
the field frame. They are insulated by two fibre or paper busings. The
left hand binding post is connected to the inside terminal of the field
winding. The outside terminal of the field winding is connected to the
left hand binding post. The right hand binding post is connected to the
right hand brush.

The base of the motor is a wooden block of suitable size.

[Illustration: FIG. 71.—Details of the Shaft, Rocker Arm, Bearing and
Pulley.]

The motor is of the series type because all the current flows through
both the field and armature. A current of 2 to 6 volts will operate the
motor. The pulley or gear required in order that the motor may be used
as a source of power will depend upon the work for which the motor is to
be employed. A small grooved pulley such as as that shown in Figure 63
may be fastened to the shaft with a set screw and will prove most useful
for general purposes.



A HORIZONTAL POWER MOTOR.


The horizontal motor does not differ very materially from the vertical
one just described.

The field frame is, however, made in two pieces, and the bearings are
cast directly on the frame. The details and dimensions are given in
Figures 68, 69 and 70.

[Illustration: FIG. 72.—Rear view of the completed Horizontal Motor.]

The field winding consists of six layers of No. 18 B. & S. Gauge double
cotton-covered wire wound on a spool or bobbin.

The core of the bobbin consists of a piece of five-eighths round steel
or iron rod, two and seven-sixteenths inches long. Two circular fibre
heads, one-eighth of an inch thick and one and one-half inches in
diameter are mounted on the core one-half an inch from one end and
fifteen-sixteenths of an inch apart. The ends of the core are set in the
holes, "C, C," in the two parts of the field frame and held in position
by two set screws threading into the holes "S" and "S."

Either the three-pole or the six-pole armature may be used. The
commutator and brushes are identical with those used in the vertical
type of motor.

The shaft is three-sixteenths of an inch in diameter and four inches
long. The brushes are mounted upon a brush arm which is shown in detail
in Figure 63. This is made of three-sixteenths inch sheet brass. The
brushes must be insulated from the arm by fibre washers and bushings in
the same manner as they were from the bearings on the vertical motor.

[Illustration: FIG. 73.—Side view of the Horizontal Motor.]

The holes in the bearings on the field frame are drilled out
three-eighths of an inch in diameter and then brushed with a piece of
three-eighths inch brass rod five-sixteenths of an inch in diameter
having a three-sixteenths inch hole through the center.




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to prove of great value to the experienced student but treats the
subject in such a manner that even the beginner will have no trouble to
clearly grasp the matter.

Among the lists of contents may be mentioned a careful discussion and
explanation of such subjects as the "why and the wherefore" of
Magnetism, Magnetic Induction, Primary Cells, Storage Batteries, the
Dynamo, the Alternator, the Motor Generator, the Induction Coil, the
Transformer, the Condenser, Volts, Amperes, Watts, Coulombs, Ohm’s Law,
Electric Waves, the Ether, Oscillations, the Aerial, Spark Gaps,
Quenched Gaps, Rotary Gaps, Helixes, Coupling, Tuning, Detectors, Tuning
Coils, Loose Couplers, Variometers, Condensers, Hot Wire Ammeters,
Circuits and Diagrams, etc., etc., etc.

Each subject is discussed in detail and in all its branches. For
instance, the lesson dealing with aerials describes vertical aerials,
pyramid aerials, flat top aerials, umbrella aerials, loop aerials, etc.,
and peculiarities or advantages. The lesson on detectors deals with
Electrolytic, Perikon, Silicon, Pyron, Carborundum, Magnetic and Audion
Detectors, etc. The lesson on the theory and arrangement of circuits
will be found invaluable.

           *THIS IS THE BOOK THAT YOU HAVE BEEN LOOKING FOR.*




                     Home Made Electrical Apparatus

Three of the most popular books ever published, filled with just the
sort of information you have been looking for. Each volume is printed on
heavy paper and contains 72 pages and over 60 illustrations and working
drawings for making every sort of electrical apparatus, all of which has
actually been built by the author.

Written so that you can completely understand them.

               VOLUME I, No. 7—80 Pages—66 Illustrations

Chapter I—STATIC ELECTRICAL APPARATUS—Static Electricity. How to Build a
Wimshurst Machine. Experiments with Static Electrical Apparatus.

Chapter II—CELLS AND BATTERIES.

Chapter III—HOW TO REDUCE THE 110 VOLT D. C. OR A. C. TO A LOWER VOLTAGE
FOR EXPERIMENTAL PURPOSES.

Chapter IV—HOW AN ALTERNATING CURRENT MAY BE CHANGED INTO DIRECT CURRENT
BY MEANS OF AN ELECTROLYTIC RECTIFIER.

Chapter V—HOW TO BUILD A STEP-DOWN TRANSFORMER FOR REDUCING THE 110 VOLT
A. C. FOR EXPERIMENTAL PURPOSES.

               VOLUME II, No. 8—72 Pages—55 Illustrations

Chapter VI—ELECTRICAL MEASURING INSTRUMENTS. Galvanometers, Ammeters,
Voltmeters, etc.

Chapter VII—CURRENT CONTROL DEVICES. How to Make a Pole Changing Switch
or Current Reverser. How to Reverse Small Motors. Battery Rheostats.

Chapter VIII—HOW TO MAKE A TELEGRAPH KEY AND SOUNDER. How to Install a
Telegraph Line and Learn to Operate. Learning the Morse Code.

Chapter IX—HOW TO MAKE AND INSTALL A TELEPHONE.

Chapter X—MEDICAL COILS AND SHOCKING COILS.

Chapter XI—THE CONSTRUCTION OF SPARK COILS. A one-quarter inch Coil, a
one-half inch Coil, a one inch Coil. Experiments with Spark Coils.

              VOLUME III, No. 9—80 Pages—73 Illustrations

Chapter XII—HOW TO MAKE A DYNAMO-MOTOR.

Chapter XIII—HOW TO MAKE A TOY BATTERY MOTOR.

Chapter XIV—HOW TO BUILD AN ELECTRIC ENGINE.

Chapter XV—MINIATURE BATTERY LAMP LIGHTING.

Chapter XVI—COHERER OUTFITS FOR WIRELESS TELEGRAPHY.

Chapter XVII—HOW TO BUILD A TESLA HIGH FREQUENCY COIL. Experiments with
High Frequency Currents.

Chapter XVIII—AN EXPERIMENTAL WIRELESS TELEPHONE.

Chapter XIX—MISCELLANEOUS APPARATUS. Electrolysis of Water.
Electro-Plating. Electricity from Heat. A Handy Light. An Experimental
Arc Lamp. A Magnetic Diver. Magnetic Fish. A Magnetic Clown. An Electric
Breeze. A Static Motor.

                 *Price Postpaid, 30 cents per volume*

All three volumes can be supplied bound together with handsome cloth
cover for $1.25 postpaid.




                 Vacuum Tubes in Wireless Communication

                           By ELMER E. BUCHER

*The only Text Book on the market devoted solely to the various
applications of the Oscillation Valve.*

An elementary text book for students, operators, experimenters and
engineers. Naval wireless men find this book especially helpful. Tells
in understandable language the fundamental operating principle of the
vacuum tube. Shows over 100 different circuits for the practical use of
the Vacuum Tube as a Detector, Radio or Audio Frequency Amplifier,
Regenerative Receiver, Beat Receiver, and Generator of Radio Frequency
Currents.

More than 100 diagrams reveal, step by step, in simple and direct form,
the uses of the vacuum tube.

*Cloth. Size 6 x 9 inches. 202 pages. 159 diagrams and illustrations.
Price, $1.75. Postage, 10 cents.*




                     Practical Wireless Telegraphy

                           By ELMER E. BUCHER

More than 65,000 copies of this book have been sold to date. It is used
in practically every school, college, library and training camp in this
country.

*Practical Wireless Telegraphy* is the recognized standard wireless text
book. It furnishes much information of utmost value in regard to the
very latest styles of wireless sets now in use.

It is the first wireless text book to treat each topic separately and
completely, furnishing a progressive study from first principles to
expert practice. Starting with elementary data, it progresses, chapter
by chapter, over the entire field of wireless—fundamentals, construction
and practical operation.

*Size 6 x 9 inches. 352 pages. 340 illustrations. Handsomely bound in
full cloth. Price, $1.75. Postage, 10 cents.*




                            Radio Telephony

                     By ALFRED N. GOLDSMITH, Ph D.

*It is the only book treating the subject of Radio Telephony in all its
aspects.*

This complete text on radio telephony is intended for radio engineers,
operators and experimenters, also radio electricians in the Navy, men in
the Signal Corps and especially men in the Aviation Service who handle
radio equipment. Students and others who desire to be clearly informed
concerning this newest and most interesting branch of electric
communication need this book.

It is written in clear style, and pre-supposes very little knowledge of
radio. Fully illustrated with wiring diagrams and previously unpublished
photographs of "wireless telephone" apparatus.

There are over 400 separate topics listed in a carefully prepared index.

*Size 6 x 9 inches. 256 pages. 226 illustrations. Full cloth, stamped in
gold. Price, $2.00. Postage, 10 cents.*




             The Operation of Wireless Telegraph Apparatus

Do your Wireless friends come to you for advice on constructing and
operating their apparatus or do you go to them for information?

Here is a chance for YOU to become the _authority_.

*This book is a necessity to every Progressive Experimenter.*

*It shows how to obtain the very highest efficiency from any station,
and how to comply with the law. How to tune, adjust your detector, spark
gap, phones, etc.*

                      *Price, 30 Cents, Postpaid.*

This book was written for the wireless experimenter who has passed the
amateur stage, but explains how the beginner also can obtain the very
best results from his station. It contains much useful information to
this end and many "kinks".

*IT SHOWS HOW* to receive or send on long or short wave lengths with
highest efficiency, to tune for longest distance reception of messages,
to use the buzzer test, how to test and connect condensers, receivers,
etc., how to use receiving transformers, variometers, etc., all with
_highest efficiency_ in view.

*IT ALSO DESCRIBES* the construction and use of a simple, inexpensive
wave meter to tune the station to any desired wave length, and tells how
to obtain a _sharp_ wave and a _pure_ wave.




                        *Model Flying Machines*

                      *HOW TO BUILD AND FLY THEM*

                  Will prove interesting and valuable.


              Have you ever built and flown a Model Racer?


                   If not, you have missed something.


                       Price, 25 Cents, Postpaid.

Model Aeroplaning is one of the most fascinating and instructive of
sports.

Thousands of young men and boys have formed Model Aero Clubs and
organized Flying Contests throughout the country.

"MODEL FLYING MACHINES" of the _Arts and Sciences_ series is the only
book giving reliable data and instructions for the construction of
practical Model Aeroplanes.

IF YOU ARE A BEGINNER, this is the book that you ought to have. It will
start you right. It tells how to build seven different types of
machines, starting with the simplest Monoplane and finishing with
several Long Distance Racing Models.

IF YOU ARE INTERESTED IN MODEL AEROPLANING, this book will prove the one
you have been looking for. Gives valuable "Kinks". Tells how to carve
propellers, make winders, adjust and fly machines, etc. Fully
illustrated with large size, detailed working drawings, showing the
exact size of each part. Twelve full-page plates.

Printed on first-class paper. Heavy cover in three colors.

         Sent postpaid by return mail upon receipt of 25 cents.


               *EVERY MODEL AVIATOR OUGHT TO HAVE A COPY*