Chapter I—STATIC ELECTRICAL APPARATUS—Static Electricity. How to Build a

Produced by James Simmons.

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Transcriber’s Note

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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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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.