At the forward end the sides are pared away to form a tongue, or tenon,
that will pass between the prongs of the upright, and a hole is bored
through it to match those in the prongs. The entire upper surface of the
lever is rounded and the under surface is rounded, beginning 6 in. from
the tenon end. Glue to the under side of the lever a block, D, at the end
of the under, flat surface. The block should be about 1-1/4 in. square by
1-1/2 in. long. If the under side of the base is crowning, either level
it with a plane or nail cleats across the ends for feet. A washer is used
with the stove bolt in connecting the lever and post.
The cuts are made of small blocks of wood, about 3/4 in. thick and of a
size to take the characters desired. These blocks must be level and the
printing side made smooth with very fine sandpaper, or a scraper, before
the characters are laid out. Boxwood is best for cuts, but pearwood,
applewood, birch, or maple will do very well. Mark out the characters
backward, using the pencil very lightly. Then, with the small blade of
a knife, made as sharp as possible, cut around the outlines, holding the
knife slanting, and remove the adjacent wood by cutting in at a reverse
angle to meet the boundary cut. Gradually deepen the cuts around the
characters until they stand in relief about 1/8 in., then score V-shaped
grooves, checkerboard fashion, across the remaining high surface that
is not a part of the design, and chip out the resulting small blocks to
bring the entire secondary surface of the block to a uniform level with
the portions adjoining the characters.
A touch of glue to the back of the cut will set it securely enough to the
bottom of the block D for printing, and allow its removal without injury
when desired. To get a uniform impression in printing, place paper on the
base, as at E, to the thickness required. For controlling the printing
position on the stock paper, pins or tacks can be stuck into the base
and each sheet to be printed laid against these guides.--Contributed by
Chelsea Curtis Frazier, Saginaw, Mich.
An Electrical Testing Instrument for Experimenters
The amateur having an ordinary flash light can make an instrument that
will serve for a variety of purposes. It is only necessary to solder a
piece of lamp cord to the spring of the battery which comes in contact
with the lamp, and pass the end through a hole drilled in the top of the
case. The end can be fitted with a cord tip.
[Illustration: An Instrument Made of an Electrical Pocket Flash Light for
Testing Circuits and Instruments]
To test batteries, take the flash light in the right hand and press the
button, lighting the lamp, then place the bottom of the flash light on one
binding post and the cord on the other. If the light burns brilliantly,
the battery is dead, but if it burns dimly or goes out the battery is
good.
It may happen that the experimenter's telegraph line is out of order
and the trouble cannot be found. The sounder may be tested out by
disconnecting the wires from the instrument and placing the bottom of the
flash light on one binding post and the cord on the other. If the light
goes out, the trouble does not lie in the sounder, but in some other part
of the line. The line may be tested in a similar manner if one end is
short-circuited and the flash light connected to the other.
A tester of this kind cannot be used on long lines, or on instruments of
much resistance, as their resistance will overcome that of the light. Keep
in mind the fact that the lamp will always burn on an open circuit and go
out on a closed circuit.
Softening the Tone of a Talking Machine
[Illustration]
An effective mute, for use on any disk talking machine, can be made by
clamping an ordinary wood clothespin on the head of the setscrew that
holds the needle. Thus the tone will be softened a great deal more than by
the use of a wood needle. The record of a stringed instrument, such as a
violin, will be almost exactly reproduced. It will also eliminate almost
all the scratching sound caused by a steel needle.--Contributed by C. M.
Reeves, Los Angeles, Cal.
* * * * *
An antenna should be made of wire larger than No. 14
gauge.
[Illustration]
A Musical Doorbell By H. Marcelle
In the construction of this doorbell it is best to purchase a small
instrument known as the "tubaphone." It consists of a rack with several
pieces of brass tubing cut to different lengths to give the proper tones
as they are struck. Such an instrument with eight tubes will play almost
any tune, and can be purchased from 50 cents up, depending on the size.
Brass tubes can be purchased, cut, and toned, but the time taken in doing
this is worth more than the price of the instrument, and no changes are
necessary in it to make the doorbell.
[Illustration: Detail of the Parts for the Construction of a Musical
Doorbell That will Play the Music on Brass Tubes with One Touch of a Push
Button]
Several strips of pine, 2 in. wide and 7/8 in. thick, are procured for
the framework. The tubes are placed on a table top, 1 in. apart and with
their lower ends on a line at right angles to their length. Allow a space
of 1 in. outside the first and last tube, and cut a piece of the wood to
this length, allowing sufficient additional material to fasten on the ends
of two uprights, which are cut long enough to admit the longest tube and
allow sufficient room for a large roller and space at the top to swing
the tubes.
A base is cut from a board, 7/8 in. thick and of sufficient size to admit
the roller and tube rack, together with a small battery motor. The tube
rack is fastened to the back of this base by making a tenon on the lower
end of each upright, and a mortise in the baseboard to receive it.
A roller is turned from a piece of soft pine, large enough to provide
room on its surface for a number of horizontal lines equal to the number
of notes in the composition to be played. These lines should not be too
close together. Supposing the music it is desired to play has 15 notes
in its composition, then 15 horizontal lines must be spaced evenly on the
surface of the roller. The length of the roller should be a free-working
fit between the uprights. A 1/4-in. steel rod is run through its center
for a shaft, allowing sufficient ends for the bearings, and, in addition,
at one end sufficient length for a pulley.
The motor is lined up on the base, so that its pulley wheel will run a
belt on the large wheel of the roller. The current is turned on after
making belt and wiring connections, a lead pencil is held directly
centering the place where each tube hangs, and a line is drawn on the
circumference of the roller.
A 1/8-in. hole is drilled through each tube, near one end, and a piece of
catgut string run into it to make a hanger. A piece of board, long enough
to fit between the uprights when placed on the slope formed by the upper
ends of the tubes after their lower ends are set straight on a line at
right angles to their length, and wide enough to swing the tubes clear
of the frame, is fastened in place, as shown. Small screw eyes are turned
into the under side of this board, at even spacings of 1 in., and used to
swing the tubes by the catgut strings. Another piece of board, the same
width as the former, is placed, perfectly horizontal, between the uprights
a short distance above the lower ends of the hanging tubes. Evenly spaced
holes are bored in this crosspiece to admit the ends of the tubes. The
holes should be of such size that when they are lined with a piece of
felt, the tubes will have a little play without touching the sides at any
point.
The hammers are each made of a strip of sheet brass, having a length that
will extend from the base to a short distance above the lower ends of the
tubes. A hole is drilled in each end of the strip, the lower one being of
a size to fasten it to the base crosspiece with a round-head wood screw.
The hole in the upper end is used to fasten a small block of wood with a
screw, for the hammer head. A small strip of felt is glued to the striking
side of the block. Another piece of brass, used for a trip, is fastened
to the center part of each long piece with rivets, so that its upper end
will be near the center of the roller for height, and strike the end of a
small peg driven into the roller. The length of these pieces, in fact, of
all pieces, will depend on the length of the tubes in the tubaphone and
the size roller required for the music.
The setting of the pegs in the roller requires some patience in order to
get the tune correct, but one mistake will be of more value than an hour's
description. The pegs can be procured from a shoemaker. If the roller is
of pine, they can be driven into the wood of the roller with a hammer.
[Illustration: The Appearance of the Doorbell Is That of a Mission Clock
on a Mantel]
With ordinary connections to the push button and motor, the mechanism
will only run while the push button is being pressed. A device that will
cause the piece of music to be played through to the finish after the
push button is pushed for a short time, consists of a turned piece of
wood fastened to the outside surface of the driving wheel on the roller.
This piece of wood should be carefully set, so that its outside surface
will be true as it revolves. Three brushes, made of copper strips, are
fastened to the base. The length of these brushes will depend on the
size of the roller and height of the block of wood. They should be evenly
spaced and fastened, so that they will be insulated from each other. One
strip of brass, or copper, is fastened around the turned piece of wood.
This strip must be as wide as two brushes, except for a short distance to
make a break in the electrical circuit. The notch in the strip, to make
this break, should be on the outside edge where it will disconnect the
center brush, and its location on the turned piece of wood should be on
a line with the end and the beginning of the pegs for the music. Another
short strip is fastened to the turned piece of wood, where it will make
a contact with the first brush when the second or middle brush is in the
notch, or disconnected, and is connected to the other notched strip with
a piece of wire run beneath the wood.
The wiring shown will make it possible to start the motor with the push
button which will turn the roll far enough to connect the center brush;
then the roller will turn until the music is played, at which point
it will stop and remain in rest until the push button again makes the
contact.
The entire mechanism can be made to set on the mantel or shelf, incased
like a mission clock, and the wires running to it may be concealed.
Replacing Buckle Tongues
[Illustration]
Having several buckles without tongues I tried to repair them with pieces
of wire, but could not get them to bend short enough to fasten around
the buckle frame. Some cotters were at hand and seeing them gave me
the idea of using one leg, with the eye part, as a tongue. By using the
proper-sized cotter, a substantial and quickly made repair will be the
result.--Contributed by Everett Hoar, Bowmanville, Ont.
* * * * *
Bread crumbs thoroughly rubbed over a pencil drawing
will remove most of the dirt and without disturbing
the pencil lines.
Drying Towels in Photographer's Dark Room
In doing a large amount of photographic work the towel becomes wet, and
to dry the hands on it is impossible. To obviate this annoyance, I made a
galvanized-iron pipe, about 2 ft. long and 8 in. in diameter, with a disk,
or circular piece, of metal about 10 in. in diameter soldered on each end
to form flanges. One flange was fastened to the wall of the dark room in
a convenient place to support the device. On the inside of the spool, or
towel support, an ordinary incandescent electric globe was placed. The
heat of the lamp would easily dry 12 in. of the towel, and when the dry
part was pulled down for use another wet portion was brought into position
for drying.
[Illustration: An Electric Globe Makes Heat in the Spool for Drying a
Portion of the Towel]
Those who have tried to handle gelatin dry plates with moist hands will
readily appreciate the value of this simple contrivance. The lamp in the
spool is connected on the switch with the ruby light, so that it is not
forgotten, when leaving the room, to turn it out.--Contributed by T. B.
Lambert, Chicago.
An Electric Chime Clock By John E. Mahlmeister
[Illustration: The Alarm Clock in Its Case and the Location of the Contact
Pins and Contact Lever (Fig. 1)]
In the construction of this clock one perfectly good and accurate alarm
clock and the works of an old or discarded one are used. The clock for the
accurate time is set into a frame, or casing, made of thin boards which
have a circular opening cut in them to fit snugly on the outside casing
of the clock. The back of the clock and casing are shown in Fig. 1. A
circular line is drawn on the casing, about 1 in. larger in diameter than
the clock, and brass machine screws with two nuts clamping on the wood
back, as shown at A, are set at intervals so as to be opposite, or just
back of, the hour marks 2, 3, 5, 6, 8, 9, 11, and 12. A contact spring,
B, is shaped as shown and soldered to the knurled knob on the back of the
clock used for setting the hands in a position where it will travel or be
parallel with the minute hand. The end of the contact spring should be
shaped so that it will slide over the points of the screws easily, but
in good contact. The ends of the screws should be filed to a slightly
rounding point. The wiring diagram for this part of the apparatus is
clearly shown, and the terminals are connected to binding posts C and D.
The binding post E is connected to the metal part of the clock.
[Illustration: Location of the Clock Works, Magnets, Binding Posts, Gongs
and Strikers on the Baseboard (Fig. 2)]
The chime part is made entirely separate and can be located at any
reasonable distance from the clock. It is propelled by the works from an
old clock, as shown at F, Fig. 2. The old clock is prepared for use by
removing the hands, balance wheel and escapement so that the wheels will
turn freely. To prevent the works from running too fast, a piece of sheet
brass, G, is soldered to the shaft running at the highest speed. The brass
should be as large as the space will admit. It forms a fan to catch the
air and retard the speed, and also provides a means of stopping the works
by the electric mechanism.
The parts for the gongs and electrical apparatus are supported on a
baseboard, 3/4 in. thick, 6 in. wide, and 18 in. long. The automatic
switch is located at one end of the base, and consists of two sets of
magnets, H and J, with an armature, K, to which is attached a stiff
contact wire, L. This wire is to make contact with the spring M when the
armature is drawn by the magnets J, and with N when drawn by the magnets
H. The springs M and N are made of thin sheet brass, bent as shown, and
mounted on the base.
A piece of wood, O, on which to mount the works of the old clock is
mortised into the base. Another standard, P, of the same height as O,
is also mortised into the base to provide a bearing for the end of the
shaft which carries the wood disk Q, the opposite end of the shaft being
connected by means of a ferrule and soldered to the end of the minute-hand
shaft. The shaft should be well lined up, so that it will turn freely.
The wood disk is 1/4 in. thick and about 6 in. in diameter.
[Illustration: The Pins are Accurately Set in Four Circular Lines and on
Radial Lines (Fig. 3)]
Mark four circles on the face of the disk, near the outside edge and
1/4 in. apart. Step off the outside circle into 150 parts and draw
a radial line from each mark across the four circular lines with the
straight edge on the center of the disk. An arc of the disk is shown in
Fig. 3, where trip pins are driven in for making the electric contacts.
This part of the arc shows the method of locating the pins for the hour
from 3 to 4 o'clock, with the intermediate pins for the quarter, half,
and three-quarter-hour contacts. The intermediate pins are arranged in
the same manner for all hours, but the hour pins, on the second circle,
run from 1 pin to 12 pins consecutively. Ordinary pins, with the heads cut
off, are used and should be driven in accurately on the division lines to
secure proper results.
The arrangement of the springs is shown in Fig. 4. These springs, when
pressed together, will close the circuit for ringing the gongs. They are
made of thin sheet brass, bent as shown at R, and fastened to a piece,
or block, of hard wood with screws, as shown at S. The springs numbered
3, 5, 7, and 9 are the ones made as shown at R for sliding over the pins
in the disk Q, and their ends should clear the face of the disk about
1/8 in. The springs 1, 2, 4, 6, and 8 are about 1/2 in. shorter and have
their ends bent up at right angles so that they will almost touch the long
ones. The spring 1 should be a little shorter than 2. When fastening the
springs to the block of wood, be sure that no two springs touch and that
each one is separated from the other to form no contact until the pins
in the wheel force them together. The block is then fastened to the base
under and parallel with the shaft carrying the disk Q, as shown.
The starting and stopping of the clockwork F is accomplished by means
of a set of bell magnets, arranged, as shown at T, Fig. 2, with the wire
attached to the armature bent to touch the brass wing of the fan G. The
armature must not vibrate, but stay against the magnet cores while the
current is flowing through them, thus allowing the clock wheels to turn,
and as soon as the current is cut off, the armature will spring back and
stop the wheels.
[Illustration: The Parts Constructing the Chime are Placed in the Clock
Frame below the Works]
Arrange four gongs, U, V, W, and X, as shown in Fig. 2, and also three
bell magnets with clappers 1, 2 and 3. These gongs should be selected
for tone as in a chime clock. The connections to the bell magnets 1, 2,
and 3 should be direct to the binding posts so that the armature will not
vibrate, but give one stroke. For instance, bell magnet 1 should produce
one stroke on the gong U when the current is on, and one stroke on the
gong V when the current breaks. The magnets 2 should cause the clapper to
strike once on the gong V when the current is on, and to make one stroke
on the gong W when the current is broken. The magnets 3 produce only one
stroke on the gong X at a time, which is used to sound the hours.
[Illustration: The Contact Springs are Operated by the Pins on the Disk
Wheel (Fig. 4)]
The parts are connected up electrically as shown in Fig. 5. The lines
between the clock, Fig. 1, and the bell-ringing part, Fig. 2, are
connected from C to C, D to D, and E, Fig. 1, to the zinc of a battery
and from the carbon to E, Fig. 2. Two dry cells will be sufficient for
the current.
[Illustration: The Wiring Diagram for the Location of the Wires on the
Under Side of the Base (Fig. 5)]
The working of the mechanism is as follows: Suppose the time is 6 minutes
of 3 o'clock and the contact spring on the back is near the 11 pin. As
soon as it touches the pin, the armature K of the switch will be drawn in
contact with the spring N, then when the contact spring touches the 12
pin, the current will flow into the magnets T and release the wheels of
the clockwork F, which turns the disk Q, and the three pins in the second
row will pass over the spring 5 and press it in contact with the spring
4 three times, causing the gong X to toll out 3 o'clock. As the contact
spring B will be on the contact pin 12 for about 1 minute, the wheels
of the clockwork F would continue to turn and the bells ring, if it were
not for the stop pin located on the outside, or first, circle of the disk
Q, which pin is set in line with the last pin in the set of pins for the
hour, or, in this instance, in line with the third pin. When the stop pin
has passed the spring, the connection through the magnets T is broken and
the clockwork F stops instantly. When the spring B strikes the 2 o'clock
pin, or 10 minutes after 3 o'clock, the armature K is drawn over to N, and
at the 3 pin, or 15 minutes after 3 o'clock, the bells U, V, and W will
ring and then the stop pin will break the current, and so on, at every 15
minutes of the 12 hours.
Hinges Used to Substitute Night Bolt
One of the safest devices for bolting, or locking, a door against
intruders is to use two sets of hinges. The extra set is fastened to the
door and frame in the same way but directly opposite the regular hinges.
It may be necessary to file the extra hinges and pins in order to separate
and bring the parts together easily. The usual door lock need not be used
with this arrangement, as the hinges are exposed only on the inside of
the room and cannot be tampered with from without.
Propellers for a Hand Sled
Desiring to propel my hand sled with power transmitted by cranks and
wheels, I set about to procure the necessary materials. Two medium-sized
buggy wheels were found in the back yard of a blacksmith shop, which were
procured for a nominal price. The fellies of these wheels were removed,
the tenons cut from the spokes and nails substituted, which were driven
in their ends so that about 1/2 in. of the body with the head projected.
The heads were then removed and the nail ends sharpened.
The hubs were plugged with pieces of wood, whittled to tightly fit the
holes. A hole was then bored exactly central through each plug for a
1/2-in. rod. This size rod was procured and bent to form a crank, the
bearing end being threaded for a distance equal to the length of the hub.
[Illustration: Sled Propelled by Revolving Wheels Turned by Cranks, the
Pointed Nails Doing the Pushing]
Two pieces or blocks of wood, 2 in. square and 4 in. long, were used as
bearings. These were bored centrally through the long way, to receive the
1/2-in. rod just loose enough to make a good bearing. These bearings were
supported by a pair of braces made of strap iron, about 1/4 in. thick and
3/4 in. wide. The length of the iron will depend on the size of the wheels
and the height of the sled runner. The braces were shaped as shown. The
center of the bearing hole must be as high from the surface of the ground
as the distance the spoke ends are from the center of the hub hole.
The crank is then run through the bearing hole and a nut run on the
threads and a washer placed against the nut. The wheel is then slipped
on the axle, and another washer and nut run on tightly. Both wheels,
bearings, cranks, and brackets are made alike. The brackets are fastened
with small bolts to the sled top.--Contributed by Justin Stewart,
Wallingford, Conn.
A Self-Feeding Match Box
With the addition of the simple device here illustrated, any match box
can be converted into one of the self-feeding type. A piece of tin, or
cardboard, is cut, as shown at A, the exact size depending on the match
box used. The piece cut out is folded on the dotted lines, the cover on
the match box is removed, and the part B pushed into the end of the box
beneath the matches. The part B is twice as long as the depth of the
box, therefore it enters the box as far as the line C. The flaps D rest
against the outside of the box, and are held in place by the box cover.
The matches feed into the box formed of the tin or cardboard as fast as
used, while the burnt ones can be placed in the upper part E.
[Illustration: The Attachment Consists of a Receptacle Fitting into the
End of a Match Box]
Corks-in-a-Box Trick
Procure a pill box and a clean cork. Cut two disks from the cork to fit
in the box, and fasten one of the pieces centrally to the inside bottom
of the pill box with glue.
To perform the trick, put the loose disk in with the one that is fast,
and then open the box to show both corks. Close the box and in doing so
turn it over, then open and only one cork will be seen. Be careful not
to show the inside of the other part of the box with the cork that is
fastened.--Contributed by Fred B. Spoolstra, Yonkers, N. Y.
A Disk-Armature Motor
One of the simplest motors to make is the disk motor, its construction
requiring a wood base, a brass disk, a 3-in. horseshoe magnet, and some
mercury.
[Illustration]
The base is made of hard wood, in the proportions shown in the sketch.
The leading-in wires are connected to the binding posts A and B, and
from these connections are made, on the bottom of the base, from A to the
groove C cut in the upper surface of the base for the mercury, and from B
to one screw, D, of one bearing. The end of the former wire must be clean
and project into the end of the groove, where it will be surrounded with
mercury.
[Illustration: Parts of the Disk Motor Shown in Detail, Also the Location
of the Horseshoe Magnet on the Base, Ends of the Poles being Directly
under the Center of the Shaft]
The bearings consist of thin sheet brass, cut to the dimensions shown,
the bearing part being made with a well-pointed center punch, as at E. The
disk wheel is made of sheet brass, 2 in. in diameter, and a needle, with
the eye broken off and pointed, is used for the shaft. The needle shaft
can be placed in position by springing the bearings apart at the top.
When the current is applied, the disk will revolve in a direction relative
to the position of the poles on the magnet. The reverse can be made by
turning the magnet over.--Contributed by Joseph H. Redshaw, Homestead, Pa.
Repairing Marble
With a little practice any mechanic can repair holes, cracks or chipped
places on marble slabs, so that the patched place cannot be detected
from the natural marble. Use the following mixture as a base for the
filler: Water glass, 10 parts; calcined magnesite, 2 parts, and powdered
marble, 4 parts. These should be mixed thoroughly to a semifluid paste.
Fill the crack or hole and smooth off level, then with a camel's-hair
brush and colors, made of aniline in alcohol, work out the veins, body
colors, etc., as near to the natural marble as possible. It will depend
on the application of the colors whether the repair can be seen or not.
Artificial-marble slabs can be formed from this mixture.--Contributed by
A. E. Soderlund, New York City.
The Construction of a Simple Wireless Telephone Set By A. E. Andrews In
Two Parts--Part I
Among the various methods for the transmission of speech electrically,
without wire, from one point to another, the so-called "inductivity"
system, which utilizes the principles of electromagnetic induction, is
perhaps the simplest, because it requires no special apparatus. Since
this system is so simple in construction, and its operation can be easily
understood by one whose knowledge of electricity is limited, a description
will be given of how to construct and connect the necessary apparatus
required at a station for both transmitting and receiving a message.
[Illustration: Fig. 1--Wire Connected to Galvanometer]
Before taking up the actual construction and proper connection of the
various pieces of apparatus, it will be well to explain the electrical
operation of the system. If a conductor be moved in a magnetic field
in any direction other than parallel to the field, there will be an
electrical pressure induced in the conductor, and this induced electrical
pressure will produce a current in an electrical circuit of which the
conductor is a part, provided the circuit be complete, or closed, just
as the electrical pressure produced in the battery due to the chemical
action in the battery will produce a current in a circuit connected to
the terminals of the battery. A simple experiment to illustrate the fact
that there is an induced electrical pressure set up in a conductor when
it is moved in a magnetic field may be performed as follows: Take a wire,
AB, as shown in Fig. 1, and connect its terminals to a galvanometer, G,
as shown. If no galvanometer can be obtained, a simple one can be made
by supporting a small compass needle inside a coil composed of about
100 turns of small wire. The terminals of the winding on the coil of the
galvanometer should be connected to the terminals of the conductor AB,
as shown in Fig. 1. If now the conductor AB be moved up and down past
the end of the magnet N, there will be an electrical pressure induced
in the conductor, and this electrical pressure will produce a current in
the winding of the galvanometer G, which will cause the magnetic needle
suspended in the center of the coil to be acted upon by a magnetic force
tending to move it from its initial position, or position of rest. It
will be found that this induced electrical pressure will exist only as
long as the conductor AB is moving with respect to the magnetic field of
the magnet N, as there will be no deflection of the galvanometer needle
when the motion of the conductor ceases, indicating there is no current
in the galvanometer winding, and hence no induced electrical pressure.
It will also be found that the direction in which the magnetic needle of
the galvanometer is deflected changes as the direction of motion of the
conductor changes with respect to the magnet, indicating that there is a
change in the direction of the current in the winding of the galvanometer,
and since the direction of this current is dependent upon the direction
in which the induced electrical pressure acts, there must have been a
change in the direction of this pressure due to a change in the direction
of motion of the conductor. The same results can be obtained by moving
the magnet, allowing the conductor AB to remain stationary, the only
requirement being a relative movement of the conductor and the magnetic
field created by the magnet.
[Illustration: Fig. 2--Compass Needle Test]
It is not necessary that the magnetic field be created by a permanent
magnet. It can be produced by a current in a conductor. The fact that
there is a magnetic field surrounding a conductor in which there is a
current can be shown by a simple experiment, as illustrated in Fig. 2.
If a wire be placed above a compass needle and parallel to the direction
of the compass needle and a current be sent through the wire in the
direction indicated by the arrow I, there will be a force acting on the
compass needle tending to turn the needle at right angles to the wire.
The amount the needle is turned will depend upon the value of the current
in the wire. There is a definite relation between the direction of the
current in the wire and the direction of the magnetic field surrounding
the wire, because a reversal of current in the conductor will result in
a reversal in the direction in which the compass needle is deflected.
Remembering that the direction of a magnetic field can be determined
by placing a magnetic needle in the field and noting the direction in
which the N-pole of the needle points, this being taken as the positive
direction, if one looks along a conductor in which there is a current and
the current be from the observer, the direction of the magnetic field
about the conductor will be clockwise. Imagine a conductor carrying a
current and that you are looking at a cross-section of this conductor (see
Fig. 3), and the direction of the current in the conductor is from you
(this being indicated in the figure by the cross inside the circle), then
the lines of force of the magnetic field will be concentric circles about
the conductor, they being nearer together near the conductor, indicating
the strength of the field is greatest near the conductor. A compass needle
placed above the conductor would place itself in such a position that the
N-pole would point toward the right and the S-pole toward the left. If
the needle be placed below the conductor, the N-pole would point to the
left and the S-pole to the right, indicating that the direction of the
magnetic field above the conductor is just the reverse of what it is below
the conductor.
[Illustration: Fig. 3--Lines of Force]
[Illustration: Fig. 4--Reversed Lines of Force]
The strength of the magnetic field produced by a current in a conductor
can be greatly increased by forming the conductor into a coil. Figure
4 shows the cross-section of a coil composed of a single turn of wire.
The current in the upper cross-section is just the reverse of what it is
in the lower cross-section, as indicated by the cross and dash inside
the two circles. As a result of the direction of current in the two
cross-sections being different, the direction of the magnetic field about
these two cross-sections will be different, one being clockwise, and the
other counter-clockwise. It will be observed, however, that all the lines
of force pass through the center of the coil in the same direction, or
the magnetic field inside the coil is due to the combined action of the
various parts of the conductor forming the complete turn. This magnetic
field can be increased in value, without increasing the current in the
conductor, by adding more turns to the coil.
[Illustration: Fig. 5--Magnetic Lines Passing through Center]
A cross-section through a coil composed of eight turns placed side by
side is shown in Fig. 5. The greater part of the magnetic lines created by
each turn pass through the remaining turns as shown in the figure, instead
of passing around the conductor in which the current exists that creates
them. This results in the total number of lines passing through the coil
per unit of cross-sectional area being greater than it was for a single
turn, although the value of the current in the conductor has remained
constant, the only change being an increase in the number of turns forming
the coil.
If a conductor be moved by the end of a coil similar to that shown in Fig.
5, when there is a current in the winding of the coil, there will be an
electrical pressure induced in the conductor, just the same as though it
were moved by the end of a permanent magnet. The polarity of the coil is
marked in Fig. 5. The magnetic lines pass from the S-pole to the N-pole
through the coil and from the N-pole to the S-pole outside the coil, just
as they do in a permanent magnet.
How to Lock a Tenoned Joint
A tenon placed in a blind mortise can be permanently fastened, when
putting the joints together, by two wedges driven in the end grain of the
wood. In some cases, where the wood to be used is very dry and brittle,
it is advisable to dip the tenon in warm water before applying the glue.
The glue must be applied immediately after the tenon is removed from the
water, and then inserted in the mortise. The sketch shows the application
of the wedges. The bottom of the mortise drives the wedges as the tenon
is forced in place.
[Illustration: Wedges in Tenon]
Fitting a Large Cork in a Small Bottle
When necessary, a large cork may be made to fit a small bottle, if treated
as shown in the sketch. Two wedge-shaped sections are cut from the cork,
at right angles to each other, as shown in Fig. 1. The points are then
squeezed together (Fig. 2) and the end inserted in the bottle (Fig. 3).
Wet the cork slightly and the operation will be easier.--Contributed by
James M. Kane, Doylestown, Pa.
[Illustration: Reducing Size of Cork (Fig. 1, Fig. 2, Fig. 3)]
A Homemade Wet Battery
[Illustration]
Procure a large water bottle and have a glass cutter cut the top off so
that the lower portion will form a jar about 8-1/2 in. high. Next obtain
two pieces of carbon, about 8 in. long, 4 in. wide and 1/4 in. thick. Melt
up some old scrap zinc and mold a piece having the same dimensions as the
pieces of carbon. The mold for casting the zinc may be made by nailing
some 1/4-in. strips of wood on a piece of dry board, forming a shallow
box, 4 in. wide and 8 in. long. Remove all the impurities from the surface
of the zinc when it is melted, with a metal spoon or piece of tin. Before
filling the mold with the metal, place a piece of No. 14 gauge bare copper
wire through a small hole in one of the end pieces forming the mold,
and allow it to project several inches inside, and make sure the mold is
perfectly level. The zinc will run around the end of the wire, which is
to afford a means of connecting the zinc plate to one of the binding posts
forming the terminals of the cell.
Cut from some hard wood four pieces a little longer than the outside
diameter of the glass jar, two of them 1/2 by 1/2 in., and two, 1/2 by
5/8 in. Drill a 1/8-in. hole in each end of all four pieces, the holes
being perpendicular to the 1/2-in. dimension in each case, and about
3/8 in. from the end. Boil all the pieces for several minutes in paraffin
and stand them up on end to drain. Procure two 1/8-in. brass bolts,
3-1/2 in. long, which are to be used in clamping the elements of the cell
together. The two smaller pieces of wood should be placed on each side of
one end of the zinc, then the carbon pieces and the larger pieces of wood
outside the carbon pieces. The carbon plates should be connected together
and then connected to a binding post which forms the positive terminal of
the cell. If unable to obtain pieces of carbon of the required dimensions,
a number of ordinary electric-light carbons may be used. Get about ten
1/2-in. carbons, without the copper coating, if possible; if not, file all
the copper off. Cut these carbons off, forming 8-in. lengths. File the top
ends of the carbons flat and so that they all become equal in thickness,
and clamp them in place by means of the brass bolts. If rods are used,
they should all be connected together by means of a piece of copper wire
and then to a binding post.
The plates may now be hung in the jar, the wooden pieces resting on the
top of the jar and acting as a support. The solution for this cell is made
by dissolving 1/2 lb. of potassium bichromate in 1/2 gal. of water, and
then adding very slowly 1/2 lb. of strong sulphuric acid. More or less
solution may be made by using the proper proportion of each ingredient.
This cell will have a voltage of two volts, a rather low internal
resistance, and will be capable of delivering a large current. If it
should begin to show signs of exhaustion, a little more acid may be added.
A chemical action goes on in this cell regardless of whether it supplies
current to an external circuit or not, and for this reason the elements
should be removed from the solution and hung directly over the jar
when the cell is not in use. A simple device for this purpose may be
constructed as shown. A cord may be passed through the opening in the
crossbar at the top and its lower end attached to the elements. When the
elements are drawn out of the solution, the upper end of the cord may be
fastened in some manner. This frame can, of course, be made longer, so it
will accommodate a number of cells.
The Construction of a Simple Wireless Telephone Set By A. E. Andrews In
Two Parts--Part II
If two coils of wire be placed parallel to each other as shown in Fig. 6,
and a current be passed through the winding of one of them, say A, a part
of the magnetic lines of force created by this current will pass through
the other coil B. These lines of magnetic force must cut across the turns
of wire of the coil in which there is no current as the magnetic field
is being created, and as a result there will be an electrical pressure
produced in the winding of the coil carrying no current. When the current
in coil A is discontinued, the magnetic field created by this current is
destroyed or it contracts to zero, and the magnetic lines again cut the
various turns composing the winding of coil B. The direction in which
the magnetic lines of force and the winding of coil B move with respect
to each other is just the reverse, when the current in the winding of
coil A is increasing, to what it is when the current in the winding of
the coil A is decreasing. Any change in the value of the current in the
winding of coil A will result in a change in the number of magnetic lines
of force linked with the winding of the coil B, and as a result of this
change in the number of lines linked with the winding of coil B there
will be an induced electrical pressure set up in coil B. The direction
of this induced electrical pressure will depend upon whether the current
in the winding of coil A is increasing or decreasing in value. When the
current in the winding of coil A is increasing in value, the electrical
pressure induced in the winding of coil B will be in such a direction
that the current produced by this induced electrical pressure will pass
around the winding of coil B in the opposite direction to that in which
the current passes around the winding of coil A. Or the current produced
by the induced electrical pressure tends to produce a magnetic field
opposite in direction to the one created by the current in the winding
of coil A. When the current in the winding of A is decreasing in value,
the induced pressure in the winding of the coil B is just the reverse of
what it was in the previous case and the current produced by this induced
pressure passes around the winding of the coil B in the same direction as
the current passes around the winding of coil A. The current produced by
the induced electrical pressure aids the current in the winding of coil A
in producing a magnetic field. In general the current resulting from the
induced pressure always passes around the circuit in such a direction as
to produce a magnetic effect which will oppose a change in the value of
the magnetic field causing the induced electrical pressure.
[Illustration: Fig. 6]
There will be an induced pressure in the winding of coil B, due to a
change in the value of the current in the winding of coil A, as long as
the coil B remains in the magnetic field of the coil A and its plane is
not parallel to magnetic lines; or, in other words, coil B must always be
in such a position that some of the magnetic lines created by the current
in coil A will pass through the winding of coil B.
If a telephone transmitter and a battery be connected in series with
the winding of coil A, a fluctuating or varying current can be made to
pass through the winding by causing the diaphragm of the transmitter to
vibrate by speaking into the mouthpiece of the transmitter. This varying
current will set up a varying magnetic field and there will be an induced
electrical pressure set up in coil B, if it be properly placed with
respect to coil A. A receiver connected in series with the winding of
coil B will be subjected to the action of a varying current due to the
induced electrical pressure in the winding of coil B and as a result,
the diaphragm of the receiver will vibrate in unison with that of the
transmitter, and speech can thus be transmitted. The connection just
described should be somewhat modified and a little more equipment used in
order to give the best results.
[Illustration: Fig. 7--Sending and Receiving Equipment]
Figure 7 shows the complete sending and receiving equipment, a complete
outfit of this kind being required for each station. The transmitter T and
the receiver R may be an ordinary local battery transmitter and receiver,
although a high-resistance receiver will give better results. The
induction coil with the windings, marked P and S, may be any commercial
type of induction coil as used in a magneto telephone instrument, but a
coil with a high-wound secondary will give better results. The push button
K is to be used in closing the transmitter circuit when the set is being
used for transmitting, the key being depressed, and for shorting out the
high resistance secondary winding when the set is used in receiving, the
key being in the normal position. Ten dry cells should be connected in
series and used to supply current to the transmitter circuit, as shown
by B in the figure. The receiver R, secondary winding of the induction
coil S, and the winding of coil A used in transmitting and receiving the
magnetic effects, are all connected in series. The winding of the coil A
consists of two parts, D and E, as shown in the figure, with two of their
ends connected together by means of a condenser, C, having a capacity of
about 2 micro-farads. Each of these parts should consist of about 200
turns of No. 22 gauge silk-covered copper wire, wound on an ordinary
bicycle rim. The inside end of one winding should be connected to the
outside of the other by means of the condenser, the two coils being wound
in the same direction. The condenser C can be procured at a small cost
from almost any telephone company.
To talk, two of the instruments are placed 25 or 30 ft. apart, and they
may be placed in different rooms as walls and other ordinary obstructions
that do not interfere with the production of the magnetic field about
the transmitting coil, have no effect upon the operation. Pressing the
button K at the transmitting station, closes the transmitter circuit and
removes the shunt from about the secondary winding of the induction. Any
vibration of the transmitter will cause a varying current to pass through
the primary winding P, which in turn induces an electrical pressure in
the secondary winding S, and this pressure causes a varying current to
pass through the coil A. The varying current in the winding of the coil
A produces a varying magnetic field which acts upon the receiving coil,
inducing an electrical pressure in it and producing a current through the
receiver at the receiving station.
A filing coherer, adapted to close a local relay circuit and ring an
ordinary bell, may be used with the sets just described for signaling
between stations.
[Illustration]
An Electric Incubator
Where electric current is available, it can be used to heat an incubator
much better and cleanlier than the kerosene lamp. The materials are
inexpensive and the cost should be no more than for the ordinary kind of
heater.
First of all the box part must be made of very dry wood, 1/2 in. thick.
The material should be matched, as the cost of the operation depends upon
the construction of the box. The proper size for an 80-egg incubator is
2 ft. square and 1 ft. high. If a larger one is desired, the dimensions
may be varied to suit, but it is not necessary to make it any higher for
a larger one. If it is desired to have a window in the door, care must
be taken to make it a good fit. The top, as shown in the sketch, is made
without hinges so that it can be readily set on and removed. This makes it
handy in case of repairing the heater and cleaning the box. The inside of
the box, with the exception of the bottom, should be covered with asbestos
paper.
[Illustration: Fig. 1--Box Details]
After the box is finished, fit it with a tray, 1-1/2 ft. by 1 ft.
10-3/4 in. A tray having these dimensions will slide easily in the box.
This is an essential feature of the hatching. The frame of the tray D,
Fig. 1, consists of wood, 3/4 by 3/4 in., with a bottom made of wire mesh.
The mesh should be firmly attached, so that it will not give away when
full of eggs. Runners for the tray are placed 4-1/2 in. from the bottom of
the box. When the tray is put in place, it will not touch the back. This
small space is left for the chicks to fall into the nursery below. About
4 in. below the tray four holes are bored, AA, 1/8 in. in diameter, one
on each side of the box. These holes admit fresh air to the eggs.
[Illustration: Fig. 2--Heater Details]
The electric heater is just large enough to allow a space about 1/2 in.
on all edges. This makes it 23 in. square. A piece of 1/4-in. asbestos
of the above size should be secured, on which to place the heating wire.
The amount of wire depends on the size and kind. As it is not necessary
to heat the wire very hot, iron or steel wire may be used. The length of
wire may be determined by the following method:
Wind the wire on a long stick, making sure that no one coil touches its
neighbor. Connect one wire of the current supply at one end of the coil
and run the other end of the current supply along the coils, starting at
the extreme opposite end and drawing toward the center until the iron wire
gets too hot to hold with the bare hand. This will be the right length of
wire to use. The length being known, a number of tacks are placed in the
asbestos board to hold the wire, as shown in Fig. 2. Cover the wire with
a sheet of asbestos and attach binding-posts, E and F, at each end.
The asbestos inclosing the heating wires is covered with a thin piece
of sheet iron, which is made to fit tightly over the bottom and sides.
This will spread the heat evenly. Be careful to have the binding-posts
insulated from the sheet metal. In the cross section of the heater, Fig.
2, A represents the 1/4-in. asbestos board; B, the heater wire; C, the
asbestos paper, and D the sheet-metal covering.
The most important part of the incubator is the thermostat which regulates
the current to maintain a steady heat. It is not advisable to make this
instrument, as a good one can be purchased for less than $1. Place the
thermostat in the end of the box at B, Fig. 1. A small door, E, is made
in the box for easy adjustment of the thumbscrews.
Suspend the heater from the cover of the box with bolts 2-3/4 in. long, as
shown in Fig. 1. A base receptacle, G, and a snap switch, H, are fastened
on top of the cover and connected up to the thermostat B, the condenser
C, the heater F, and lamp I, as shown. Another snap switch, J, is used
on the light only. The condenser C is to prevent sparking, thus saving
the platinum points on the screws. Do not use more than a 2-cp. lamp for
lighting purposes, as a brighter light blinds the young chicks.
The incubator should be run for a day or two so that the current may
be well regulated before placing the eggs in the tray. The incubator is
operated the same as with lamp heat.--Contributed by M. Miller, Lansing,
Mich.
A Cover for Magazines
As soon as Popular Mechanics, or any other magazine of similar size,
arrives and before any member of the family looks through it, strip off
the front cover and carefully remove the narrow strip on the back as shown
in Fig. 1. Strengthen the back with a piece of bookbinding tissue, A,
Fig. 2, and then paste a piece of heavy manila paper, B, over the covers
and back. Over this paste a piece of dark blue cambric, Fig. 3, carefully
turning the edges even with the book. The picture from the cover and the
date added to the left corner of the picture are neatly pasted on, Fig.
4, and the narrow strip is glued to the back.
[Illustration: Removing the Cover, and Binding with Heavy Paper (Fig. 1,
Fig. 2)]
The book is put under a heavy weight for several hours. Thus a neat,
strong cover, which looks well in a bookcase, is secured at very little
expense. The eager handling by every member of the family cannot soil or
deface the cover.--Contributed by Katharine D. Morse, Syracuse, N. Y.
[Illustration: Cloth Cover and Paper Cover Attached (Fig. 3, Fig. 4)]
An Optical Illusion
A very deceiving illusion can be contrived with a bit of wire, a rubber
band and a toothpick. An ordinary straight hairpin will serve instead of
the wire. The hairpin or wire is bent as shown in the illustration, and
the rubber band then placed on the inverted U-shaped part. A toothpick
is inserted through the rubber band and a few turns taken by slipping the
toothpick back and forth so it will pass the wire.
[Illustration: Toothpick in Rubber Band (Fig. 1, Fig. 2)]
Hold the wire straight in front of the eyes, and, using the forefinger
of the right hand, turn the end of the toothpick A, Fig. 1, down until it
almost reaches the opposite point A, Fig. 2, and let the finger slip off.
It will appear as if the toothpick passed through the wire.--Contributed
by H. H. Windsor, Jr.
Temperature Alarm
The falling temperature of a room during the night may result in a very
bad cold for the occupant. This may be prevented by the use of an alarm to
awaken the sleeper and warn him to close the window. An alarm can be made
as follows: Take a glass tube about 4 in. long and 1/4 in. in diameter and
close one end, used for the bottom, with sealing wax, in which the bare
end of a No. 20 gauge magnet wire is inserted. The tube is almost filled
with mercury. On the mercury a float of wax is placed in which a bare
piece of the same magnet wire is inserted and bent as shown in the sketch.
The tube of mercury is fastened to a base with two clips of metal. At the
upper end of this base the adjustable lever A is attached. The electric
connections are made as shown in the sketch.
[Illustration: The Alarm and Wiring Diagram]
Should the temperature fall during the night, the mercury will contract,
the float descend and the circuit close, so that the bell will ring.
The adjustable lever allows setting the alarm for various differences of
temperature.--Contributed by Klyce Fuzzelle, Rogers, Ark.
Paper Smoother and Penwiper
[Illustration]
A convenient paper smoother and penwiper can be easily made as follows:
Procure a common celluloid harness ring, A, about 1-1/2 in. in diameter
and fasten a penwiper, B, to it. The wiper is made of arts-crafts leather,
doubled and filled with pieces of chamois. They are held in place with a
ribbon or cord tied as shown. The roughened paper caused by erasing can
be easily smoothed with the ring.--Contributed by G. H. Holter, Jasper,
Minn.
Stereoscopic Pictures with an Ordinary Camera
Make a small table as wide as the camera is long and 3 in. longer than
the camera is wide. Sink a screw nut in the center of the under side to
engage the regular tripod screw. Fasten a double or two-way spirit level
on the front left-hand corner. Nail strips on both ends and on the rear
side, to form a shallow box with three sides. The illustration shows
the construction quite plainly. This device was used by a correspondent
of Camera Craft as follows: The table was fastened to the tripod and
carefully leveled. The camera is placed at one side, bringing the back
snugly into the corner on that side. Make the exposure, change the film,
slide the camera over to the other side and make another exposure. The
table being 3 in. longer than the camera is wide, the lens will be moved
exactly 3 in. when the camera is moved over to the other side. Three
inches is the separation of the lenses in stereoscopic cameras and the
negatives made as above will be the same.
[Illustration: Table on Tripod for Camera]
As the negatives must be sized, it is necessary to use films. A camera
using films 3-1/2 by 3-1/2 in. will make negatives that can be trimmed
1/4 in. on each side to make prints 3 by 3-1/4 in. Each two negatives
making a pair are fastened together, properly transposed, by folding a
narrow strip of black paper like a long, V-shaped trough, pasting it,
and putting one on the bottom of the two negatives, as they lie side by
side, and one at the top; saddle fashion. This can be done still easier by
using strips of passe-partout binding, or strips used for binding lantern
slides. If so desired, the use of black paper can be carried farther
by cutting the top strip of binding paper in such a way that it gives
the round corners to the top of the prints. A narrow strip through the
center and a binding of black paper along the two end edges make a mask
unnecessary in printing.
How to Make a Paper Drinking Cup
Every person should understand the simple method of making a paper
drinking cup. It may be necessary at times to make quick use of medicine
and with no cup or spoon convenient, the pyramid-shaped cup shown in the
sketch is a useful emergency utensil.
[Illustration: Folds in the Paper (Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5)]
The paper cup is made as follows: Cut the paper into a square and crease
it on the dotted lines, A G, F B, and C D E, as shown in Fig. 1. Fold
the paper in half through the line C D E to form a rectangle, Fig. 2.
Fold points C and E inward until they meet inside the triangle to form
the shape shown in Fig. 3. This makes four distinct corners, F, G, A
and B. Fold the paper over on the dotted line and bring the points A
and B together as in Fig. 4. The extreme edges meet in the central line
indicated. Reverse the paper and fold the points G and F in like manner.
Turn the points A B and F G inward and fold on the dotted line, and you
will have a perfect pyramid-shaped cup as shown in Fig. 5.--Contributed
by Miss Margaret S. Humphreville, Mt. Pleasant, O.
A Hand Corn Sheller
A very handy device for shelling corn, and especially popcorn, can be
made of a 1-in. board on which is fastened a piece of metal lath. The
edges of the metal lath are bound with a strip of wood nailed to the
board.--Contributed by Ulysses Flacy, Long Beach, California.
[Illustration: Metal Lath on a Board]
A Shaft Coupling
In connecting a small 1/8-hp. motor to a small air pump where both shafts
were 3/8 in. in diameter, I quickly made a coupling that would save the
wear on the machines, as follows. The coupling was made of a piece of
3/4-in. brass rod with a 3/8-in. hole drilled through its center. One
end of the hole was enlarged to 7-16 in. for about 7/8 in. The end of the
coupling having the small hole was slipped on the pump shaft and fastened
with two setscrews. The other end was drilled to take a pin loosely, the
pin fitting tightly in a hole drilled in the motor shaft. The pin was bent
at one end so as to keep it from falling out and the other end fitted with
two nuts. The motor shaft being a little loose in the coupling, gave it
a chance to work free without binding.--Contributed by Leo J. Werner, New
York City.
[Illustration: Coupling on the Shafts]
Reading the Date of a Worn Coin
The date and denomination of a coin worn smooth can be determined in the
following manner: Take an ordinary coal shovel, or a piece of sheet metal,
and place it in a hot fire. Allow it to become red hot, then remove, and
place the coin on the hot surface of the metal. Any figures or letters can
be readily seen when heated in this manner. This test seldom fails even
when the inscriptions have been worn so smooth that they are invisible to
the naked eye.
Making a Knife an Easy Opener
The large blade of my knife being so hard to open placed me in constant
risk of breaking my thumbnail. To overcome this difficulty, I ground a
notch in the handle as shown in the sketch. After smoothing it up with a
round file and fine sandpaper, I had just as good a job as if the knife
had been made that way, and it is very easy to open it, as it can be
done with the thumb and forefinger. Anyone can improve his knife in this
way, but be careful not to cut the notch back of the point of the small
blade.--Contributed by C. M. Mahood, Warren, Pa.
[Illustration: Notch in the Handle]
Construction of a Small Bell-Ringing Transformer By A. E. Andrews
Part I--Fundamental Principles
The transformer in its simplest form consists of two separate and
electrically independent coils of wire, usually wound upon an iron core.
[Illustration: Fig. 1--Two Coils on an Iron Ring]
Figure 1 shows two coils, P and S, placed upon an iron ring, R. One
of these coils is connected to some source of energy, such as an
alternating-current generator, or an alternating-current lighting circuit,
receiving its energy therefrom. The other coil is connected to a load to
which it delivers alternating current. The coil of the transformer that
is connected to the source of energy is called the primary coil, and the
one that is connected to the load, the secondary coil.
The electrical pressure (voltage) at which current is supplied by the
secondary bears a definite relation to the electrical pressure at which
current is supplied to the primary. This relation, as will be explained
later, is practically the same as the relation between the number of turns
in the secondary and primary coils. If there are a smaller number of turns
in the secondary coil than there are in the primary, the secondary voltage
is less than the primary, and the transformer is called a step-down
transformer. If, on the other hand, there are a larger number of secondary
turns than of primary, the secondary voltage is greater than the primary
voltage, and the transformer is called a step-up transformer.
The transfer of electrical energy from the primary coil to the secondary
coil of a transformer is based upon the fundamental principles of
electromagnetism and electromagnetic induction, and it will be necessary
to investigate these principles before we can understand the operation of
the transformer.
A magnet is a body, which, when freely suspended, assumes approximately
a north and south position. The end of the magnet that points north is
called the north pole, while the end that points south is called the south
pole. The region surrounding a magnet is called a magnetic field. In this
field the magnetism is supposed to flow along a large number of imaginary
lines, called lines of force, and these lines are all supposed to emanate
from the north pole of the magnet, pass through the medium surrounding
the magnet and enter the south pole. The magnetic field surrounding a bar
magnet is shown in Fig. 2. The strength of any magnetic field depends upon
the number of these lines of force per unit area (square centimeter), the
area being taken perpendicular to the direction of the lines.
[Illustration: Fig. 2--Magnetic Field]
In 1812, Oersted discovered that a compass needle, which is nothing but
a permanent magnet freely suspended or supported, when placed near a
conductor in which there was a direct current, was acted upon by a force
that tended to bring the needle into a position at right angles to the
conductor. This simple experiment proved to Oersted that there was a
magnetic field produced by the current in the conductor. He also found
that there was a definite relation between the direction of the current
in the conductor, and the direction in which the north pole of the
compass needle pointed. If the compass needle is allowed to come to rest
in the earth's magnetic field, and a conductor is placed above it, the
conductor being parallel to the needle, and a current then sent through
the conductor, the needle will be deflected from its position of rest.
Reversing the current in the conductor, reverses the direction in which
the needle is deflected. If the needle be allowed to come to rest while
there is a current in the conductor, and this current is then increased,
it will be found that the deflection of the needle will be increased,
but not in direct proportion to the increase in the current. Hence the
strength of this magnetic field surrounding the conductor depends upon
the value of the current in the conductor, and the direction of the field
depends upon the direction of the current.
[Illustration: Fig. 3--Magnetic Field around Conductor]
If a conductor be passed through a piece of cardboard, as shown in Fig.
3, and a current sent through it in the direction indicated by the arrow
A, a compass needle, moved about the conductor in the path indicated by
the dotted line, will always assume such a position that the north pole
points around the conductor in a clockwise direction as you look down
on the cardboard. If the current be reversed, the direction assumed by
the compass needle will be reversed. Looking along a conductor in the
direction of the current, the magnetic field will consist of magnetic
lines encircling the conductor. These lines will be concentric circles,
as a general rule, except when they are distorted by the presence of other
magnets or magnetic materials, and their direction will be clockwise.
[Illustration: Fig. 4--Magnetic Field Surrounding a Conductor]
[Illustration: Fig. 5--Magnetic Field about a Coil]
[Illustration: Fig. 6--A Coil about a Magnetic Circuit through Iron and
Air]
The strength of the magnetic field at any point near this conductor will
depend upon the value of the current in the conductor, and the distance
the point is from the conductor. The magnetic field surrounding a
conductor is shown in Fig. 4. The plus sign indicates that the direction
of the current is from you. The strength of a magnetic field due to a
current in a conductor can be greatly increased by forming a coil of the
conductor. Each turn of the coil then produces a certain number of lines,
and the greater part of these lines pass through the center of the coil,
as shown in Fig. 5. The field strength inside such a coil is dependent
upon the number of turns in the coil, and the value of the current in
these turns. Increasing the number of turns in the coil increases the
number of magnetic lines passing through the center of the coil, as shown
in Fig. 6. If the current be decreased in value, the field strength is
decreased, and if the current be reversed in direction, the magnetic field
is reversed in direction. The number of magnetic lines passing through the
solenoid depends also upon the kind of material composing the core of the
solenoid, in addition to the number of turns and the value of the current
in these turns. The number of lines per unit area inside a solenoid with
an air core can be multiplied several times by introducing a soft-iron
core. If this core be extended as shown in Fig. 7, the magnetic circuit
(the path through which the magnetic lines pass) may be completed through
it. The larger part of the total number of lines will pass through the
iron, as it is a much better conductor of magnetism than air.
[Illustration: Fig. 7--A Coil about a Magnetic Circuit through Iron]
In 1831, Michael Faraday discovered that there was an electrical pressure
induced in an electrical conductor when it was moved in a magnetic field
so that it cut some of the lines forming the field. If this conductor
be made to form part of a closed electrical circuit, there will be a
current produced in the circuit as a result of the induceds electrical
pressure. The value of this induced electrical pressure depends upon the
number of magnetic lines of force that the conductor cuts in one second.
If 100,000,000 lines are cut in one second, an electrical pressure of one
volt is produced. The direction of the induced pressure depends upon the
direction of the movement of the conductor and the direction of the lines
of force in the magnetic field; reversing either the direction of the
magnetic field or the motion of the conductor, reverses the direction of
the induced pressure. If both the direction of the magnetic field, and the
direction of the motion of the conductor be reversed, there is no change
in the direction of the induced pressure, for there is then no change in
the relative directions of the two. The same results can be obtained by
moving the magnetic field with respect to the conductor in such a way that
the lines of force of the field cut the conductor.
[Illustration: Fig. 8--Two Coils about a Magnetic Circuit through Iron]
If a permanent magnet be thrust into a coil of wire, there will be an
electrical pressure set up in the coil so long as the turns of wire
forming the coil are cutting the lines of force that are produced by the
magnet. When the magnet is withdrawn, the induced electrical pressure will
be reversed in direction, since the direction of cutting is reversed. A
magnetic field may be produced through a coil of wire by winding it on the
magnetic circuit shown in Fig. 8. Now any change of current in the coil P
will cause a change in the number of magnetic lines passing through S and
hence there will be an induced electrical pressure set up in S so long as
the number of lines passing through it is changing. The pressure induced
in each of the turns comprising the coil S depends upon the change in the
number of magnetic lines through it.
Let us now consider a condition of operation when there is no current in
the secondary coil and the primary coil is connected to some source of
electrical energy. When this is the case the current in the primary coil
is not determined by Ohm's law, which states that the current is equal to
the electrical pressure divided by the resistance, but is considerably
less in value, for the following reason. The magnetic lines of force
produced by the current in the primary induces an electrical pressure in
the primary winding itself, the direction of which is always opposite to
the impressed pressure, or the one producing the current. As a result
of this induced pressure being set up in the primary, the effective
pressure acting in the circuit is decreased. At the same time there is an
electrical pressure induced in the secondary winding in the same direction
as that induced in the primary.
If the secondary circuit be connected to a load, there will be a current
in the secondary winding, which will pass around the magnetic circuit
in the opposite direction to the primary current, and as a result will
decrease the number of lines passing through the primary coil. This will
in turn decrease the electrical pressure induced in the primary coil, and
a larger current will exist in the primary winding than there was before
any current was taken from the secondary coil. The decrease in induced
pressure is small, but it is always ample to allow the required increase
in primary current. There is, at the same time, a small decrease in the
secondary pressure.
When the transformer is operating on no load, with no current in the
secondary coil, the induced pressure in the primary coil is practically
equal to the impressed pressure and hence a very small current will be
taken from the source of energy. It is apparent now that if the primary
and secondary coils have the same number of turns, the induced electrical
pressure in each of these coils will be the same, assuming, of course,
that all the magnetic lines that pass through the primary also pass
through the secondary coil, and vice versa, or the secondary pressure
is practically the same as the pressure impressed on the primary. If the
number of turns in the secondary coil is greater or less than the number
of turns in the primary, the magnetic lines will be cut a greater or less
number of times by the secondary coil, and hence the induced pressure will
be greater or less, depending upon the relation of the number of turns in
the two coils.
Spirit Photographs
Print some photographs in the usual way on printing-out paper, then fix
them in a solution of 1 oz. hyposulphite of soda and 8 oz. of water, and
wash them thoroughly. While the prints are still wet, immerse them in a
saturated solution of bichloride of mercury. Be very careful to wash the
hands and trays after using the mercury solution, as it is poisonous.
When the print is placed in the mercury solution, the picture vanishes
completely. Leave the prints in this bath just long enough for the image
to disappear, and then wash and dry them thoroughly. Soak some clean
blotting paper in the hyposulphite-of-soda solution and allow it to dry.
You are now ready to perform the magic-photograph trick.
To cause the spirit photograph to appear, cut a piece of blotting
paper the same size as the prepared print and moisten it, then hold the
apparently blank piece of paper in contact with it. The picture will
come out clear and plain, and if thoroughly washed out it will remain
permanently.
* * * * *
Saturate a small piece of cotton batting in glue
and wrap it around a nail, then place it in a hole
previously made in a plaster wall. When the glue
dries, the nail will remain permanently.
Construction of a Small Bell-Ringing Transformer By A. E. Andrews
Part II--Construction
Transformers may be divided into two main groups, the classification
being made according to the relation between the magnetic circuit of the
transformer and the primary and secondary windings. When the two windings
surround the magnetic circuit of a transformer, as indicated in Fig.
9, the transformer is said to be of core type. If the magnetic circuit
surrounds the windings, as indicated in Fig. 10, the transformer is said
to be of the shell type. The following instructions are for a shell-type
transformer.
[Illustration: Fig. 9--Core-Type Transformer]
Any mass of magnetic material, such as a piece of soft iron, when placed
in a magnetic field that is produced by an alternating current, will be
rapidly magnetized and demagnetized, the rapidity of the change depending
upon the frequency of the current producing the field. When a piece of
iron is magnetized and demagnetized, as just stated, there will be a
certain amount of heat generated in it and this heat represents energy
that must come from the electrical circuit producing the magnetic field
in which the iron is placed.
[Illustration: Fig. 10--Shell-Type Transformer]
The heat that is generated in the iron is due to two causes: First, the
hysteresis loss which is due to a property of the iron that causes the
magnetism in the iron to lag behind the magnetizing influence, or the
changes that are constantly taking place in the field strength due to
the alternating current. This loss cannot be entirely eliminated, but it
may be reduced to a very low value by using a soft grade of iron, or one
having what is called a low hysteretic constant. Second, the eddy-current
loss which is due to the circulation of currents through the mass of
metal. These currents are due to unequal electromotive forces set up in
the different parts of the piece of metal when there is a change in the
strength of the field in which the metal is placed. This loss cannot be
entirely eliminated, but it can be greatly reduced by breaking the mass
of metal up into parts and insulating these parts from each other, which
results in the paths in which the eddy currents originally circulated
being destroyed to a certain extent.
The breaking up of the metal is usually made in such a way that the
joints between the various parts are parallel to the direction of the
magnetic field. When the joints are made in this way, they offer less
opposition to the magnetizing force. This is one of the principal reasons
why induction-coil cores are made up of a bundle of wires instead of a
solid piece. These wires are annealed or softened to reduce the hysteresis
loss that would occur. The combined hysteresis and eddy-current losses,
which are spoken of as the iron losses, will of course be very small in
the transformer you are going to construct, but the above discussion is
given to show why the magnetic circuits of transformers are built up from
sheets of soft iron, called laminations. The core is said to be laminated.
The dimensions of the complete magnetic circuit, of the transformer you
are going to construct, are given in Fig. 11. The primary and secondary
windings are both to be placed about the center portion C, and it is
apparent that the winding of these coils would be very tedious if the
wire had to be passed back and forth through the openings A and B. This
procedure in winding can be prevented by first forming the part of the
magnetic circuit upon which the windings are placed; then wind on the
coils and, after they are completed, finish building up the magnetic
circuit with pieces cut to the proper size and shape.
[Illustration: Fig. 11--Complete Magnetic Circuit]
Procure a small quantity of soft, thin sheet iron and cut out a sufficient
number of rectangular pieces, 3 in. by 4-1/4 in., to make a pile 3/4 in.
in height when firmly pressed together. Now cut a rectangular notch in
each of these pieces, 2 in. wide and 3-5/8 in. long. The sides of this
notch can be cut with a pair of tinner's shears, and the end can be cut
with a sharp cold-chisel. Be careful not to bend either piece any more
than you can help. The outside piece, or the one in which the notch is
cut, should have dimensions corresponding to those given in Fig. 12. When
all of these pieces have been cut, as indicated above, the rectangular
pieces, 2 in. by 3-5/8 in., that were cut out to form the notch in the
larger pieces, should have two of their corners cut away, so as to form
pieces whose dimensions correspond to those given in Fig. 13. These last
pieces are to form the core and part of the end of the transformer. Now
make sure that all the edges of the pieces are perfectly smooth and that
they are all of the same size; then give each one a coat of very thin
shellac.
[Illustration: Fig. 12--Outer Portion of the Magnetic Circuit]
[Illustration: Fig. 13--Inner Portion of the Magnetic Circuit]
Now cut from a piece of insulating fiber, that is about 1/16 in. thick,
two pieces whose dimensions correspond to those given in Fig. 14. When
these pieces are completed, the core of the transformer can be assembled
as follows: Place the T-shaped pieces, whose dimensions correspond to
those given in Fig. 13, through the openings in the pieces of insulation,
alternate pieces being put through the openings from opposite sides. The
distance from outside to outside of the pieces of insulation should be
exactly the same as the length of the vertical portion of the T-shaped
pieces forming the core, or 3 in.
[Illustration: Fig. 14--Insulating Washer]
Cut from some soft wood four pieces having cross sections whose dimensions
correspond to those given in Fig. 15, and of such a length that they
will just slip down between the two pieces of insulation. These pieces
should now be placed on the four sides of the iron core and covered with
several layers of heavy insulating cloth. Each layer of the cloth should
be shellacked as it is put on, which will increase the insulation and
at the same time help in holding the wooden pieces in place. You are now
ready to start winding the transformer.
[Illustration: Fig. 15--Wood Filler]
The secondary, which is the low-voltage side in this case, as you are
using the transformer to reduce or step down the voltage, will have
the smaller number of turns, and larger wire should be used in winding
it than in the primary, as it will carry a larger current. On account
of the secondary being of larger wire, it will be placed on the core
first. For this winding you will need a small quantity of No. 26 B. &
S. gauge, single cotton-covered wire. Drill a small hole through one of
the insulating washers, down close to the cloth covering the core, being
careful at the same time to keep the hole as far from the metal part of
the core as possible. Pass the end of a short piece of No. 18 or 20 B.
& S. gauge, double cotton-covered wire through this opening and solder
it to the end of the No. 26 wire. Insulate the joint with a piece of
paraffin paper or cloth, and bind the piece of heavy wire to the core of
the transformer with a piece of linen thread.
Now wind the No. 26 wire on the core as evenly as possible, to within
about 1/8 in. of the end of the spool. Place over the first layer two
layers of paraffin paper and wind on a second layer of wire. Three layers
should give you the required number of turns in the secondary winding
and a resistance of approximately 3-1/2 ohms. The end of the secondary
winding should be terminated in the same way as the winding was started.
Outside of the completed secondary winding place at least six layers of
paraffin paper, or several layers of insulating cloth. The paraffin paper
used should be approximately five mills in thickness. You can make your
own paraffin paper by taking a good quality of writing paper about two
mills thick and dipping it into some hot paraffin, then hanging it up by
one edge to drain.
The primary winding is to be made from No. 34 B. & S. gauge, single
silk-covered copper wire. The inside end of this winding should be started
in the same way as the secondary, but at the end opposite to the one
where the secondary terminated. Wind about 240 turns on each layer and
place one layer of paraffin paper between each layer of wire. The primary
winding should have at least 12 layers, and the outside end should be
terminated as the inside end. Outside of the completed windings, place
several layers of insulating cloth to serve as an insulation, and at the
same time provide a mechanical protection for the windings.
[Illustration: Fig. 16.--Upper Clamping Pieces]
The outside part of the magnetic circuit can now be put in place. When
the U-shaped pieces are all in place, the magnetic circuit will have
the form and dimensions shown in Fig. 11. A clamp should now be made
for each end of the transformer, to hold the pieces forming the magnetic
circuit together, and at the same time give an easy means of mounting the
transformer. Cut from a piece of sheet iron, about 1/16 in. in thickness,
two pieces whose dimensions correspond to those given in Fig. 16, and two
pieces whose dimensions correspond to those given in Fig. 17. Drill the
holes in these pieces as indicated, and bend the larger ones into the form
shown in Fig. 18. These pieces can now be clamped across the ends of the
transformer with small bolts, as shown in Fig. 19.
[Illustration: Fig. 17--Lower Clamping Pieces and Mounting Supports]
A box should now be made from sheet iron to hold the transformer. The box
should be of such dimensions that it will be at least 1/8 in. from the
transformer at all points. This box should be provided with a cover that
can be easily removed.
[Illustration: Fig. 18--Shape of Support]
Now mount the transformer in the box by means of small bolts, that pass
through the holes in the supports and holes in the bottom of the box.
Two binding-posts can now be mounted on one end of the box, and insulated
from it, to serve as terminals for the secondary winding. Two pieces of
stranded No. 14 B. & S. gauge, rubber-covered copper wire should now be
soldered to the terminals of the primary circuit and passed out through
insulating bushings mounted in holes cut in the end of the box opposite
to the one upon which the binding-posts were mounted. These heavy wires
should be firmly fastened to the iron part of the transformer inside the
box, so that any outside strain placed upon them will not, in time, break
them loose from the smaller wires. Be sure to insulate all joints and
wires well inside the box.
[Illustration: Fig. 19--Method of Clamping Transformer Together]
A circuit can now be run from a 110-volt lighting or power circuit,
observing the same rules as though you were wiring for lights, and
connected to the heavy wires, or primary circuit. The binding-posts,
or secondary winding should be connected to the bell circuit and the
transformer is complete and ready to operate. You may have to change the
adjustment of the bells, but after a little adjustment they will operate
quite satisfactorily.
Mirror Hinged to Window Casing
[Illustration]
A shaving mirror is usually placed on a window sash to avoid shadows as
much as possible. This is very inconvenient and many times the mirror is
broken by a fall. A good way to avoid shadows and have the mirror handy is
to hinge it to the window casing. This can be done with screweyes, A, and
screwhooks, B. The screweyes are turned into the frame of the mirror and
the screwhooks into the window casing. Two screwhooks can also be turned
into the casing on the opposite side of the window, if desired, so that
the mirror can be used on either side.--Contributed by James D. McKenna,
New Britain, Conn.
A Cleaning Bath for Silverware
A good way to clean silverware of all coloring by eggs or other substances
is to place the silver articles in a kettle of boiling water containing
a few pieces of zinc. An electrolytic action is produced by the zinc,
water and silver which decomposes the sulphides on the silver and leaves
it well cleaned. No silver is taken away by this method.--Contributed by
Loren Ward, Des Moines, Iowa.
To Prevent Poultry Water from Freezing
The method shown in the sketch is used by me in cold weather to keep
the drinking water for the poultry from freezing. The device consists
of a part of a barrel inverted and set over the fountain, and a tubular
lantern. A small opening is cut in one side of the barrel through which
the fowl can reach the water.--Contributed by P. C. Fish, Kansas City, Mo.
[Illustration: Lantern and Fountain in Half Barrel]
How to Make a Letter Scale
[Illustration]
A reliable letter scale that can be easily made is shown in the sketch. It
consists of a wide-neck bottle filled with water into which the weighing
device is inserted. This latter part is made of a light piece of wood
weighted on the lower end, to keep it in a stable, upright position, and
a piece of cardboard is tacked to the other. The wood is placed in the
water, and known weights are used on the cardboard while calibrating.
The first line is marked at the water level when there is no weight on
the cardboard, and then a known weight placed on the top and another mark
made at the water level, and so on, until a sufficient number of 1/2-oz.
and ounce-divisions have been marked. The wood should be well coated with
shellac varnish before it is placed in the water.--Contributed by Francis
Chetlain, Chicago.
Summer Dish Washing
A labor-saving method in dish washing for a summer day is as follows:
Construct a substantial wood frame and cover it with galvanized wire mesh.
Attach legs and put it in a convenient place on the back porch. Wash the
dishes on one end, and wipe the silverware dry. At the outer end spread a
towel over the wire and place the dishes turned down upon it to dry, and
cover them with another towel.--Contributed by L. Alberta Norrell, Tifton,
Ga.
Nozzle Angle for Lawn Sprinkling
[Illustration]
Where there is no prop or water sprinkler at hand for tilting the nozzle
of a hose, start to tie a knot in the hose, as shown in the sketch, but
do not draw it up tightly. The hose nozzle can be tilted to any angle in
this manner.--Contributed by S. J. Eddy, Portland, Oregon.
Simple Methods of Connecting Call Bells
[Illustration: Wiring Diagrams for a Single Bell (Fig. 1, Fig. 2, Fig. 3)]
The following diagrams will indicate a few of the various methods that
may be employed in connecting up electric bells for different purposes,
A, B and C representing the push buttons; D, the bells; E, the batteries,
and G, the ground. The simplest possible connection is shown in Fig. 1,
the bell D, battery E, and push button A, are all connected in series.
The operation of the bell is independent of the order in which the bell,
battery, and push button are placed, so long as there is a complete
circuit when the push button is pressed. One of the wires in this circuit
may be done away with by completing the circuit through the ground, as
shown in Fig. 2. Connecting a bell as shown in this diagram often results
in quite a saving of wire. The proper connections for operating one bell
from either of two push buttons, A or B, is shown in Fig. 3. Two bells,
D, operated from a single push button, C, are connected as shown in Fig.
4. The two bells, D, are shown connected in parallel, which requires
more wire than if they were connected in series. If they be connected in
series, one or the other should have its make-and-break contact closed.
The bell whose circuit remains unchanged will intercept the current for
the other bell in series with it. The operating of the bells is more
satisfactory, however, when they are in parallel, and each taking current
from the battery independent of the other.
[Illustration: Wiring Diagram for Two or More Bells (Fig. 4, Fig. 5, Fig.
6)]
The diagram, Fig. 5, shows the proper connections for operating two bells
from two independent push buttons, each push button operating a particular
bell. Any number of bells operated from any number of push buttons, all of
the bells being rung from any one of the push buttons, are connected as
shown in Fig. 6. Such a circuit can be used as a fire alarm or time call
in a factory, the operation of the circuit being controlled from any one
of a number of different points.
[Illustration: Wiring Diagrams for Return-Call Bells (Fig. 7, Fig. 8, Fig.
9)]
The proper connections for what is called a return-call circuit is
shown in Fig. 7. The circuit is so arranged that the bell at one end is
controlled by the push button at the other end. Such a circuit can be
used in transmitting signals in either direction. A ground return-call
circuit is shown in Fig. 8. In the circuits shown in Figs. 7 and 8, only
one battery is needed.
The connections of a two-wire metallic return-call circuit are shown
in Fig. 9. A special push button must be used in this circuit, and in
this case two batteries are used instead of one, as in Figs. 7 and 8.
This circuit may be changed to a ground return-call circuit by using
the earth as a conductor instead of either wire. There are, of course,
numerous other methods that may be used in connecting call bells, but the
connections shown in the diagrams are perhaps the most common.
Refrigerator for Dry and Warm Climates
Set a bowl containing butter, cream or fruit in a saucer and cover the
bowl with a moistened napkin, allowing the edges to hang in a larger
saucer filled with water, and place the whole in the air out of the sun's
rays. The article to be kept cool may also be placed in a pan with an
earthenware crock turned over it and covered with a small towel or cloth,
the edges of which extend into another outer pan partly filled with water.
The method can be applied on a larger scale by using a shallow galvanized
pan which will contain many articles and more water. This manner of
cooling is especially adapted to camping parties and will prevent sloppy
butter, sour milk and spoiling fruit. The articles are also kept free from
ants and flies.--Contributed by C. B. Hosford, Swansea, Ariz.
Pencil-Sharpening Guide
[Illustration]
The sketch shows how a guide for making a true point on a lead pencil
may be made of a block of wood. The hole, which should be large enough
to allow the pencil to be turned easily, is bored at the proper angle to
form the desired point on the pencil. The long side of the block serves as
a guide for the knife blade, while the projection at the bottom acts as
a stop. The guide insures an even point and is easily manipulated. It is
held in the palm of the left hand and the pencil is turned with the thumb
and forefinger, while the knife is held against the face of the block,
cutting edge downward, and worked up and down with the right hand.
Homemade Hinges
[Illustration]
When making a chicken house recently I had forgotten to procure hinges.
When searching the "junk" box I found some little metal brackets such as
used for holding spring roller shades. Attaching these as shown, I made
a good substitute hinge. A pair of the brackets having no slots were
selected. A 2-1/2-in. wire nail with a washer was placed in the hole
and driven into the top of the door, 1 in, from its back edge. The other
bracket was placed on the bottom of the door in a similar manner. The door
was placed in an open position and the prongs of the brackets were nailed
to the door post. The bottom bracket may also be nailed to the floor and
the top one to the lintel.--Contributed by Robert Smith, E. Burnaby, B. C.
Skimmer for Bottled Milk
The cream that rises on the milk in an ordinary milk bottle cannot be
removed easily. Where a small family desires to use the cream for coffee,
the skimmer shown in the sketch is very handy.
[Illustration]
The cone is made of metal--tin, brass or copper--which can be
nickelplated, the seam being soldered. The cone is 2 in. deep with a
diameter at the top of 1-3/8 in. A handle can be made of a discarded sugar
or teaspoon, which is soldered to the cone. Insert the cone in the bottle
far enough for the cream to flow into it and then withdraw. Cream will
gather about 3 in. deep on rich milk. The milk can be used for cooking. A
piece of wire can be used for a handle instead of the spoon.--Contributed
by Victor Labadie, Dallas, Texas.
How to Preserve Putty
Having some putty left over after a job of glazing and wishing to keep it
without its becoming dried up, I tried wrapping it in paraffin paper such
as used to wrap butter. I found this method to be a decided success, the
oil being prevented from drying out.--Contributed by Levi R. Markwood,
Fairview, Pa.
[Illustration]
How to Build a Simple Electric Motor By A. G. McClure
An exceedingly simple and inexpensive motor that may be used in operating
small toys can be constructed as follows: First procure a good permanent
magnet, about 5 in. long and about 1-1/2 in. between the inside edges
at the open end. This magnet should be at least 1/2 in. thick, and if it
cannot be had in one piece, two or more may be placed side by side, like
poles being placed together. The writer was unable to procure ready-made
magnets, so one was formed and magnetized. Obtain a piece of tungsten or
some other good-grade steel, 1/2 in. by 1/2 in., and about 11 in. long.
Bend this piece into the form of a U, with the inner edges 1-3/4 in.
apart. Square off both ends and drill two small holes in the outside
surface of each end, at AA, about 3/8 in. from the end. Tap these holes
for small machine screws. Drill the hole B with a small drill, about
1/16 in., in the center of the lower portion of the U and ream it out. The
piece should now be clamped with a good pair of blacksmith's tongs,--a
block of iron being placed between the ends to keep the pressure of the
tongs from drawing them together--heated to a cherry red and then plunged
into a bath of oil. It can then be magnetized by placing it in contact
with a permanent magnet.
[Illustration: Detail of Armature Laminations, and Completed Parts
Assembled, but without Armature Windings]
Next obtain a piece of 1/8-in. brass, about 1/2 in. wide and 5-1/2 in.
long. Drill two holes in each end of the piece to match those drilled in
the ends of the magnet, also one in the center, and tap it for a 1/8-in.
machine screw. Now bend this piece into the form shown. Provide a machine
screw, S, for the hole C and drill a small tapered hole in the end of the
screw.
Obtain a small quantity of soft sheet iron and cut a sufficient number
of pieces similar to that shown at D to make a pile 1/2 in high. Cut two
pieces of the same size from some thin sheet brass. Now place all of these
pieces in a pile, the brass pieces being on the outside, and clamp them
securely, then drill the two small holes, E and F. Place two small copper
rivets in these holes and rivet the heads down before removing the clamp.
Drill a 1/8-in. hole, G, through this piece, the armature, for the shaft
to pass through. Procure a piece of 1/8-in. steel rod, about 6 in. long.
Sharpen one end so that it will enter the hole B, then cut the other end
off and sharpen it so that it will enter the opening made in the end of
the screw S. The armature may now be soldered to this shaft, its left-hand
surface being flush with the ends of the magnet.
A small commutator, H, should now be made as follows: Obtain a piece of
thin brass tubing about 5/8 in. in diameter. Turn down a piece of hard
rubber so that the tube will fit tightly on it. Drill a hole in this
piece of rubber of such a size that it will have to be forced on the steel
shaft. Saw two longitudinal slots in the brass tube diametrically opposite
each other and then bind these two pieces in place on the piece of rubber
with some heavy linen thread wrapped around each end. The armature is now
ready to wind. Get a small quantity of No. 22 gauge cotton-covered wire,
solder one end to one of the segments of the commutator, then wind one end
of the armature full and cross over and wind the other end full, soldering
the end of the wire to the second commutator segment. Make sure to wind
both ends of the armature in the same direction so the current in both
parts of the winding produces magnetizing effects in the same direction.
Insulate the winding from the core and the different layers from each
other with a good quality of thin writing paper.
Two small brushes should now be made from some thin spring brass and
mounted on the brass piece as shown. These brushes should be insulated
from the piece of brass and two small binding posts should be provided for
making connections to them. The position of the commutator and brushes
should be such that the brushes move from one segment to the other
when the ends of the armature are directly in line with the ends of the
permanent magnet.
A small pulley should be mounted upon the shaft to be used in transmitting
the power. The whole device may be mounted in a horizontal position on a
wooden base as shown, and the motor is complete.
How to Make a Humidity Indicator
A simple weather indicator that may be used in determining the condition
of the atmosphere may be made as follows: Dress a small figure, in the
form of a doll, with a piece of cloth, previously dipped in the following
solution: Chloride of cobalt, 30 parts by weight; sodium chloride, 15
parts; gum arabic, 7-1/2 parts; calcium chloride, 4-1/2 parts, and water,
400 parts. This cloth will change color as the amount of moisture in the
atmosphere changes, the change being due to the cobalt salt, which, in
dry air, is lavender blue. As the moisture in the atmosphere increases,
the color changes first to bluish red, then light red and finally pink,
according to the amount of moisture. With a decrease in moisture, the
colors change in the reverse order to that given above, and the blue color
returns when the air becomes dry.
The "Q" Trick
Lay out the form of the capital letter Q with coins on a table and ask
someone in the audience to select a number and then ask that person to
count up from one until the number is reached, beginning at A and stopping
on the circle, for instance at B, then counting back again beginning
with one, but, instead of counting on the tail, pass it and go around
the circle, say, to C. The performer gives these instructions to the
person doing the counting. The one selecting the number must not tell the
performer what the number is, and the latter is to leave the room while
the counting proceeds. The performer, before leaving the room, is to tell
which coin will be the last one counted.
[Illustration]
Take, for example, the number 7. Counting from A to B there are just 7
coins and counting back the last number or 7 will be at C. Try 9 for the
number and the last one counted will also be C. The number of coins in the
tail represents the number of coins in the circle from the intersection of
the tail and circle to the last number counted. For instance, the sketch
shows 4 coins in the tail, therefore the last coin counted in the circle
will be at C or the fourth coin from the intersection of the tail and
circle.
By slipping another coin in the tail the location of the last coin counted
is changed, thereby eliminating any chance of exposing the trick by
locating the same coin in the circle every time. This can be done secretly
without being noticed.
To Keep Ants Away From Food
Suspend a shelf, breadbox or rack with wire around which is tied a piece
of cotton cloth, saturated with a mineral oil. The ants will not cross
the oil-soaked cloth.
Some strong wire hooks attached to the rack or shelf answer well to
hang small articles on, such as bacon, bags of sugar, syrup cans,
etc.--Contributed by C. B. Hosford, Swansea, Ariz.
Vaulting-Pole Holder
An adjusting device for a vaulting pole that can be easily fixed at
any point on a round pole by using a wedge and ring, is shown in the
sketch. The wedge carries a pin on which to place the cross pole. The
manner of using this device as well as its construction is clearly
indicated.--Contributed by Sterling R. Speirs, St. Louis, Mo.
[Illustration: The Ring on the Upright, Held in Position by the Wedge,
Which in Turn Carries the Pole on the Pin]
Flying Model Aeroplane for a Display
A novelty for a window display is made of a model aeroplane flying by its
own power. To control the direction and make the model fly in a circle it
is fastened to a long stick or beam which is pivoted in the center. The
one shown was pivoted to a roller-skate wheel which in turn was fastened
to a metal standard. The beam was attached to the skate wheel with two
small bolts which were insulated and carried two brushes as commutator
contacts.
[Illustration: Detail of Parts Showing Wire Connections and Model in
Flight around the Central Axis]
The commutator rings were made of heavy brass strips, fastened to a round
piece of wood which was attached to the metal standard. The wires from the
current supply were connected to the commutator rings. From the brushes
connecting wires were carried along the beam to the aeroplane motor which
was a small battery motor with propeller.
The opposite end of the beam was weighted to balance it. The first sketch
shows the parts and the manner of making the connections. The aeroplane
is driven in a circular path by its own power in a realistic manner.
An Electric Time Light
Although the modern alarm clock is a wonderfully effective piece of
mechanism, it is, to say the least, very abrupt in its manner. It
seldom confines its efforts to the chamber of its owner, but spreads its
disturbance all over the building. It is very easy for a person to arise
early in the summer and no greater difficulty should be experienced in
winter, if the bedroom is brightly lighted at the proper hour. To do this
simply and automatically became the problem.
[Illustration]
The first thought was to obtain one of those clock-actuated electric-light
switches, such as the stores use, but this would not do, because it meant
some unsightly wiring around the room. It was then remembered how, in the
course of some experiments, an ordinary incandescent light was operated
through a piece of No. 36 gauge wire without any sign of heating. If,
then, a wire only 1/200 in. in diameter were of ample carrying capacity,
surely a dollar watch would be sufficient to make the connection. Such
being the case, the whole mechanism could readily be attached to the drop
cord of a lamp directly above the socket, thus obviating any additional
wiring. This all proved to be true, and the whole was made and attached
in the course of a couple of hours.
While one might feel enthusiastic about this small and easily contrived
affair, it is scarcely to be presumed that it would operate so effectively
on one who had spent the larger part of the night tripping the "light
fantastic," or in undue conviviality. An ordinary 16-cp. globe has thus
far operated perfectly, and a 40-watt tungsten lamp would, if not too far
away, surely awaken the hardest sleeper of sober habits.
The base of the mechanism is a small piece of 1/4-in. hard wood, upon
which is fastened a small brass bracket, A, bent so as to hold the watch
from slipping down. A small clip, B, was then arranged so as to grip the
neck of the watch after its lower edge had been placed against A, and
a small brad at either side prevented lateral movement. In this way the
watch was held firmly, yet in a manner that would permit its being taken
out instantly when necessary. The glass and minute hand were removed. The
brass bolt from an exhausted dry cell was placed at C, so as to clamp a
small copper washer to which was soldered a narrow strip of copper, D,
about 1/16 in. wide and cut from a leaf of an old dynamo brush. This strip
is arranged so as to wipe the hour hand as it travels past, but being so
thin, it has no appreciable effect on the time keeping. As illustrated,
the device is set for six o'clock, but by loosening the nut C an hour's
adjustment either way may be had. It is a very simple matter, however,
to arrange the device so it will operate at any hour. In connecting up,
one end of the drop cord is removed from the socket and attached to A,
which throws the current through the watch, thence along the hand and
down D to C, from where it is carried by a short piece of wire to the
socket again. As there are so many circuits through the watch, the small
current required for one light does not affect it in any way. Thus far,
no trouble has been experienced in making this delicate connection with
110 volts, but if any should develop, the contacts may be tipped with the
small pieces of platinum taken from a burned-out globe.
* * * * *
The meat of a white English walnut may be easily
removed by heating the nut in an oven or on top of a
stove, then using a knife to pry the shell open.
[Illustration]
A Small Shocking Machine
[Illustration: The Shocking Coil as It is Used for Amusement, or in the
Manner a Current is Given a Patient]
An amusing as well as instructive shocking machine, usually called
a medical coil, can be easily constructed from a discarded buzzer or
electric bell, four binding posts, some pieces of insulated wire, two
carbon rods, and a rheostat.
[Illustration: The Base upon Which the Buzzer and Rheostat are Fastened,
and the Electrical Connections (Fig. 1, Fig. 2)]
[Illustration: The Rheostat That is Used to Regulate the Flow of Current
in the Carbon Hand Pieces (Fig. 3)]
A base for attaching the parts is made of a piece of poplar, 10 in. long,
5 in. wide, and 1/2 in. thick, which can be finished as desired, but
a good method is to shape the edge like molding and give it a mahogany
stain, and when dry apply a coat of white shellac, which should be allowed
to dry a day, whereupon the surface is rubbed with prepared wax. When the
base is ready, mount the buzzer at one end. This can be easily done by
making an L-shaped piece of metal, A, which is fastened to the base with
a screw, and to the yoke of the magnet coil with a small bolt. If the
armature and its connections are also used from the buzzer, the height
of the coils must be taken in consideration. These parts are fastened in
position as shown, using an L-shaped piece of metal, B, for the spring
end. The screw holding the armature spring to the base, as well as the
vibrator screw, should be of such a length that it will enter the base
far enough to permit a connection for a wire in a countersunk hole bored
in the base from the under side. Binding posts are placed in the corners
of the base in holes countersunk from the under side for the screw heads.
The rheostat is of the miniature-battery type, which has a round base
and a coil of resistance wire with a lever passing over the coil. Such
a rheostat can be purchased from an electrical store, but if the person
constructing the shocking machine desires to make one, it is not difficult
if a lathe is at hand.
To make the rheostat, turn up a disk, about 3 in. in diameter, from a
piece of hard wood, such as oak, maple, or walnut, and form a circular
groove in the upper surface, about 3/8 in. inside of the circumference.
The groove is to admit a circular coil of resistance wire, and in making
it, be sure to have it the proper size to take the coil snugly. The coil
can be of any size, and to make it, resistance wire is wound around a
piece of wire used as a mandrel. If the coil is 1/4 in., or a trifle
smaller, in diameter, it will make a good size. Be sure that the depth
of the groove is such that it will allow a part of the coils of the
resistance wire to project above the surface of the wood disk. The coil
of wire should be just long enough to fit in the groove and allow a 1-in.
space between the ends, one of which is anchored to the base, at C, the
other being attached to the binding post D. Drill a hole through the
center of the disk and fasten a lever, taken from a switch, or one made of
a piece of sheet brass, that will extend from the center to the outside of
the disk, or over the resistance-wire coil. A small handle is attached to
the outer end. A connection is made from the center support of the lever
to the binding post E.
The connections for the buzzer and rheostat are made on the under side
of the base, where grooves are cut to run the wires in, so that they
will be below the surface of the wood. In the diagram, the binding post
F is connected to the binding post D of the rheostat, which in turn is
connected to the screw of the make-and-break point G. The other binding
post H is connected to the bracket B supporting the armature spring. The
binding post E of the rheostat is connected to the base binding post J.
The magnet coils are connected, as shown, from K to L, and from M to B.
The two pieces of carbon, which are used for the hand pieces, are
connected with silk-insulated wire. These connections are made to
the binding posts F and H. The other two binding posts, J and L, are
connected to a battery. The carbons used may be purchased, or taken
from an old battery. Two or more dry cells are used for the current.
The rheostat controls the amount of current passing through the hand
pieces.--Contributed by Gilbert Crossley, Erie, Pa.
Secret Compartment in Ordinary Table Drawer
It is frequently desired to have some handy place for storing valuables
where there is but little chance of discovering them. Secret drawers in
tables usually require special and expensive changes, but with only a
few simple changes on a regular drawer of any ordinary table, a secret
compartment can be made which is as secure as can ordinarily be figured
on, outside of a steel safe. Having chosen the desired table, a partition
should be placed across the entire back part of the drawer, allowing for
necessary space in the secret compartment. This partition should resemble
the real back of the drawer as closely as it is possible to make it. The
compartment must not be too wide, for the resulting small width of the
front part of the drawer might then arouse suspicion. On the lower side
of the secret compartment a strip of wood, A, should be attached with
a screw, as shown in Fig. 1, allowing sufficient looseness so the strip
may be turned end for end when necessary. With the strip set as shown, it
will strike the front side B of the table when the drawer is pulled out,
leaving the secret compartment still hidden. In order to expose this, it
will be necessary to turn the strip, as shown in Fig. 2, when the drawer
can be pulled out to its full length.
[Illustration: Two Positions of the Strip for Holding, or Giving Access
to, the Secret Part, and a Hinged Strip (Fig. 1, Fig. 2, Fig. 3)]
It being necessary that the strip A be as long as the secret compartment
is wide, to fully expose this, there may be cases where the drawer is not
wide enough to allow the strip A to turn around. In that case the strip
can be hinged to the back of the drawer as shown in Fig. 3. When it is
hanging down, as shown by the dotted outline, the drawer may be pulled
out to its full extent. When it is desired to lock the secret compartment,
the hinged strip must be swung up in position, and fastened. An ordinary
thumbscrew or eye can be used which, by a turn or two, will either release
it or fasten it in place.--Contributed by Paul Durst, Detroit, Mich.
Inflating Handballs
When handballs become "dead," or no longer bounce freely, they may
frequently be restored by inflating them with air. This can be done
by means of a bulb attached to a hypodermic needle. The needle must be
inserted through the soft plug which every inflated ball has, and which
can be discovered by pressure. After the ball is inflated and the needle
extracted, the soft rubber closes around the fine hole, preventing the
escape of the air. If a leak is found, which allows the air to escape too
rapidly, a repair can be made with a single-tube tire outfit.--Contributed
by A. B. Wegener, Camden. N. J.
A Garden-Bed Scarecrow
A very neat and successful scarecrow for garden beds can be made as
follows: A number of corks are procured, and a feather is stuck in each
end of them, as shown. These are tied to a string, spacing them from
1 to 2 ft. apart, and the string is hung over the beds. The slightest
breeze will keep them fluttering, and no bird will come to rest on the
beds.--Contributed by M. T. Canary, Chicago.
[Illustration: The Fluttering Feathers Attached to the String with Corks
Scare the Birds Away]
Measuring the Length of Wire Wound on a Spool
When winding magnet spools on a lathe, the exact amount of wire used can
be easily determined by means of the device shown in the illustration.
The large reel from which the wire is obtained is conveniently placed
on a loose mandrel, or rod, near the lathe, and in line with the spool
which is to be wound. A grooved idler wheel, the exact diameter of which
is known, is supported between the spool and wire reel so it may freely
revolve; the number of its revolutions should be obtained, automatically,
by a revolution counter. When using the device, the wire from the reel
is placed once around the idler to insure the necessary grip to prevent
it from sliding; then it is led to the spool. The exact diameter of the
idler being known and the number of revolutions indicated, the true length
of the wire wound on the spools can be easily determined by the following
formula: Length of wire on spool in feet equals circumference of idler in
feet times number of revolutions of idler.--Contributed by C. Swayne, St.
Louis, Mo.
[Illustration: Measuring the Length of Wire on a Spool with the Use of an
Idler and Counter]
Homemade Lawn Sprinkler
With a short length of old hose, a serviceable lawn sprinkler can be
quickly and easily made. One end is provided with a regular coupling for
connecting it to the line of good hose. The other end is turned up for
several inches, and securely wired to the main part, thereby shutting off
any flow through it. Several cuts are made into it, about halfway across
and 6 in. apart. If the water is forced in, the only means of escape
will be through the slots, which will produce fine sprays, giving as
good service as a manufactured sprinkler.--Contributed by A. B. Shaw, N.
Dartmouth, Mass.
[Illustration: The Slots Cut in the Hose will Produce a Very Fine Spray
of Water]
Homemade Toy Bank
The little bank illustrated is not exactly burglar-proof, but once put
together it cannot be opened except by the destruction of one of the
units of which it is composed. It requires but little skill to make, and
would be a good problem for manual training, as it offers an excellent
opportunity for teaching certain rudiments of woodworking by the
application method.
[Illustration: Six Pieces of Wood as They are Put Together to Form a Toy
Bank]
In its construction, six pieces of hard wood, of the dimensions shown in
the sketch, are required. White wood will do if there is no hard wood at
hand. The coin slot is 1/8 in. wide by 1-1/4 in. long, and is cut in only
one piece.
No difficulty will be experienced in putting the first five pieces
together, but the sixth, or top, piece, shown in the sketch, will not
go in, because the bottom edge of the raised side will strike the inside
of the piece to the right. By beveling this edge with a chisel from top
to bottom between the dadoes, or grooves, it can be forced down quite a
distance and sprung in place by placing a block of wood on the high side
and striking it a sharp blow with a heavy hammer.--Contributed by J. A.
Shelly, Brooklyn, New York.
An Electric Anemometer By Wm. H. Dettman
The construction of this instrument is so simple that any amateur can
make one and if accurate calibrations are desired, these can be marked by
comparison with a standard anemometer, while both are placed in the wind.
The Indicator
The case of the indicator is built of thin wood--the material of an old
cigar box will do--9 in. long, 6 in. wide and 1-1/2 in. deep. If cigar-box
material is used, it must first be soaked in warm water to remove the
paper. If a cover is to be used on the box, a slot, on an arc of a circle,
must be cut through it to show the scale beneath. The arc is determined by
the length of the needle from a center over the axis on which the needle
swings. When the box is completed, smooth up the outside surface with fine
sandpaper and give it a coat of stain.
The core of the magnet is made by winding several layers of bond paper
around a pencil of sufficient size to make an inside diameter of slightly
over 1/4 in., and a tube 2 in. long. Each layer of the paper is glued to
the preceding layer.
Two flanges or disks are attached to the tube to form a spool for the
wire. The disks are cut from thin wood, 1-1/4 in. square, and a hole bored
through their centers so that each will fit on the tube tightly. One of
them is glued to one end of the tube and the other fastened at a point
1/2 in. from the opposite end. The space between the disks is filled with
seven layers of No. 22 gauge insulated magnet wire, allowing sufficient
ends of the wire to project for connections. The finished coil is located
in the box, as shown at A, Fig. 1.
[Illustration: The Indicator Box with Coil, Needle and Scale, as It is
Used in Connection with the Anemometer (Fig. 1)]
The core for the coil is cut from a piece of 1/4-in. iron rod, 1-1/4 in.
long, and a slot is cut in each end, 1/4 in. deep, into which brass strips
are inserted and soldered, or otherwise fastened. The strips of brass are
3/16 in. wide, one 1-1/2 in. long and the other 3/4 in. Two 1/16 in. holes
are drilled in the end of the long piece, and one 1/16 in. hole in the
end of the short piece. The complete core with the brass ends is shown in
Fig. 2.
[Illustration: The Metal Core for the Coil... (Fig. 2)]
[Illustration: ...and the Bearing Block for the Axis of the Needle (Fig.
3)]
The needle B, Fig. 1, is made of a copper or brass wire, about 6 in. long,
and is mounted on an axis at C. The detail of the bearing for the axis
is shown in Fig. 3. The axis D is a piece of wood fitted in the U-shaped
piece of brass and made to turn on brads as bearings, the center being
pierced to receive the end of the needle. After locating the bearing
for the axis C, Fig. 1, it is fastened in place so that the upper end
or pointer of the needle will travel over the scale. The needle is then
attached to the bearing after having been passed through the inner hole of
the longer brass strip of the core, and the coil is fitted with the core
in the manner shown at D. A light brass coil spring is attached to each
end of the core, as shown at E and F, the latter being held with a string,
G, whose end is tied to a brad on the outside of the box, for adjustment.
A better device could be substituted by attaching the end of the spring F
to a nut and using a knurled-head bolt passed through the box side. One of
the wires from the coil is attached to a push button, H, to be used when
a reading of the instrument is made. The connections for the instrument
consist of one binding post and a push button.
[Illustration: The Anemometer as It is Mounted on a Standard Similar to
a Small Windmill Weather Vane (Fig. 4)]
The Anemometer
The anemometer resembles a miniature windmill and is mounted on top of
a building or support where it is fully exposed to the air currents. It
differs from the windmill in that the revolving wheel is replaced by a
cupped disk, A, Fig. 4, fitted with a sliding metal shaft, B, which is
supported on crosspieces, CC, between the main frame pieces DD. The latter
pieces carry a vane at the opposite end. The frame pieces are 1/2 in.
thick, 2-1/4 in. wide and 36 in. long, and the crosspieces have the same
width and thickness and are 4 in. long.
[Illustration: (Fig. 5)]
A variable-resistance coil, E, is made as follows and fastened in the
main frame. The core of this coil is a piece of wood, 2 in. square and
4 in. long, and wound with No. 18 gauge single-wound cotton-covered
german-silver wire. The winding should begin 1/4 in. from one end of the
core and finish 1/4 in. from the other, making the length of the coil
3-1/2 in. The ends of the wire are secured by winding them around the
heads of brads driven into the core. A small portion of the insulation
is removed from the wire on one side of the coil. This may be done with
a piece of emery cloth or sandpaper. A sliding spring contact, F, is
attached to the sliding shaft B, the end of which is pressed firmly on the
bared portion of the wire coil. One end of a coil spring, which is slipped
on the shaft between the pieces CC, is attached to the end crosspiece, and
the other end is fastened to the sliding shaft so as to keep the shaft and
disk out, and the flange H against the second crosspiece, when there is
no air current applied to the disk A. The insulation of the standard upon
which the anemometer turns is shown in Fig. 5. The standard J is made of
a piece of 1/2-in. pipe, suitably and rigidly attached to the building or
support, and the upper end, around which the anemometer revolves to keep
in the direction of the air currents, is fitted with a plug of wood to
insulate the 1/4-in. brass rod K. A bearing and electric-wire connection
plate, L, is made of brass, 1/8 in. thick, 2 in. wide and 4 in. long. The
bearing and connection plate M are made in a similar manner. The surface
of the holes in these plates, bearing against the pipe J and the brass
rod K, make the two connections for the wires from the variable-resistance
coil E, Fig. 4, located on the main frame, to the wire connections between
the two instruments. These wires should be weather-proof, insulated,
attached as shown, and running to and connecting the indicator with the
anemometer at NN, Fig. 1.
Two or more dry cells must be connected in the line, and when a reading is
desired, the button H, Fig. 1, is pushed, which causes the current to flow
through the lines and draw the magnet core D in the coil, in proportion
to the magnetic force induced by the amount of current passing through
the resistance in the coils on E, Fig. 4, from the contact into which the
spring F is brought by the wind pressure on the disk A.
How to Make Stick Shellac
It is often desired to use shellac in solid or stick form, and to get
it into this shape by melting and molding requires considerable time. A
much quicker method is to place the shellac in a shallow box, spread it
out in a thin layer and play the flame from a Bunsen burner upon it until
the mass is melted and run together. Allow it to stand a few seconds,
then, with moistened fingers, fold it over and over and shape it with the
fingers. It is possible to make a stick 8 or 10 in. long and 5/8 in. in
diameter in about 5 minutes.--Contributed by J. H. Beeber, Rochester, N.
Y.
Substitute for a Hose Reel
Not having the room to spare for the ordinary hose reel, I used as a
substitute a piece of wire bent into the shape of a letter S and with its
aid coiled the hose in a manner to expel the water and leave it in shape
for storing.
[Illustration: A Hook for Coiling a Hose Instead of Turning It on a Reel]
The hook A is sprung around the hose about 5 ft. from the connection joint
and remains there permanently. The end of the hose with the connection C
is then brought around in a circle and forced into the hook B. This forms
the start for the coil and the hose is easily rolled up to the nozzle, the
water being expelled during the operation.--Contributed by F. H. Aldrich,
Toledo, Ohio.
Addressing a Roll of Papers
When addressing rolled-up papers it is difficult to write on the curved
surface. The papers also have a tendency to roll away. By placing the roll
in the hollow on the front edge of a large book, as shown in the sketch,
it will be found easy to write on the wrapper.--Contributed by W. P. Shaw,
Toronto, Canada.
[Illustration: The Roll of Paper is Placed in the Curved Edge of a Book
for Addressing]
Repairing the Bruised Sides of a Motorboat
When the sides of a boat become scored or bruised scrape the parts clean
and fill the depressions with wood cement. The wood cement or stick
cement, as it is called, can be procured from a paint store. Heat the
cement with a blowtorch and apply it to the bruised parts. Use a heated
putty knife to smooth the cement and make the surface level. After
sandpapering the fills and applying a coat of paint the boat sides will
look as good as new. The cement will not chip or fall out.--Contributed
by Henry Beck, Bronx, New York.
How to Make an Electric Lamp Flasher
Procure two pieces of metal, one of brass and the other of sheet iron,
5 in. long, 1/2 in. wide, and 1/32 in., or just a little more, in
thickness. Bend the brass strip into the form shown in Fig. 1, then place
the brass piece on top of the iron and drill the holes A and B indicated
in Fig. 2. After the brass piece has been bent, as shown in Fig. 1, it
will of course be shorter than the iron strip and the iron strip must be
cut off, or a brass strip a little longer than 5 in. can be secured and
cut the same length as the iron strip after it is bent. The holes A and
B should be 3/32 in. in diameter. The next thing to do will be to wind
a heating coil about the brass strip. Wrap a very thin layer of sheet
asbestos about the brass strip, and wind on the strip 18 ft. of No.
34 gauge bare superior resistance wire. Use a thread about .006 in. in
diameter to separate the various turns. This thread can be removed after
the winding is completed and the ends have been fastened. Rivet the iron
and brass pieces together with a small brass rivet in the hole A, Fig. 2.
After the two pieces are riveted together bend them into the form shown
in Fig. 4 and then drill the two 1/8-in. holes C and D, as shown in Fig.
2. Tap the hole B, Fig. 2, to take a small machine screw.
[Illustration: Dimensions of the Brass Strip and Mounting Base, Showing
the Location of the Holes and the Shape of the Brass Strip to Receive the
Coil of Wire (Fig. 1, Fig. 2, Fig. 3)]
The base is constructed as follows: Procure a piece of slate, 5-3/8 in.
long, 1-1/2 in. wide, and 1/2 in. in thickness. Drill the holes indicated
in Fig. 3. The four corner holes are for mounting the flasher in its
containing case, and should be about 1/8 in. in diameter. The holes E,
F, G, and H should be 1/8 in. in diameter and countersunk with a 3/8-in.
square-ended drill, on the under side, to a depth of 3/16 or 1/4 in. Cut
from some 1/16-in. sheet brass a piece 1-3/8 in. long, and 1/2 in. wide.
Drill two 1/8-in. holes in this piece, 7/8 in. apart and equally spaced
from the ends. Procure four 1/8-in. brass bolts, two 1/2 in. in length,
and two 1 in. in length. Secure four small washers and two additional
nuts. Mount the combined iron and brass strip on the slate base, using a
long and short bolt as shown in Fig. 4. One terminal of the winding should
be placed under the head of the bolt J. Place a washer, K, between the
head of the bolt and the wire. The brass strip L can now be mounted in
a similar manner, as shown in Fig. 4. Place the other end of the winding
under the head of the bolt M.
[Illustration: The Assembled Parts Showing the Complete Flasher and
Electric Connections with Adjusting Screw (Fig. 4)]
Obtain a small screw, N, Fig. 4, of such a length that its point will
reach the brass strip L when the screw is placed in the hole B, Fig. 2. A
lock nut, O, should be provided for this screw so that it will remain in
adjustment. The point of the screw and the point on the brass plate where
the screw touches should be of platinum, as the brass will not withstand
the high temperature of the arc formed when the circuit is broken.
A metal box should now be provided to serve as a containing case and the
flasher is complete. This box should be of such design and construction
that it will comply with the requirements of the electrical inspection
department having jurisdiction over the locality where the flasher is to
be used.
The flasher should be connected in series with the lamp, the wires being
fastened under the nuts on the bolts P and R, Fig. 4, and the screw N
adjusted so that it lacks a small fraction of an inch of making contact
with the brass plate when there is no current in the winding. When the
switch is turned on there will be a current through the lamp and winding
in series. The brass strip will be heated more than the iron and it will
expand more, thus forcing the point of the screw N down upon the brass
plate, which will result in the winding about the brass strip being
shorted and the full voltage will be impressed upon the lamp, and it will
burn at normal candlepower. When the coil is shorted there will of course
be no current in its winding and the brass strip will cool down, the screw
N will finally be drawn away from contact with the brass plate, and the
winding again connected in series with the lamp. The lamp will apparently
go out when the winding is in series with it, as the total resistance of
the lamp and winding combined will not permit sufficient current to pass
through the lamp to make its filament glow. The time the lamp is on and
off may be varied to a certain extent by adjusting the screw N.
Timing Photograph Prints
An amateur photographer insists that a timing clock in the darkroom is a
needless luxury. In order to time printing exposures, which he does with
a pendant tungsten light under a reflecting shade, he simply fastens the
electric-light cord so that the lamp and shade will act like a pendulum
bob which beats the seconds. Of course he makes no effort to be exact,
but if the distance between the lamp and the point of suspension of the
cord be about 39 or 40 in., the beats will be very nearly seconds. When
the light is turned on, it is started swinging, and the operator can thus
easily count seconds with sufficient accuracy, and, besides, it readily
furnishes a guide for duplicating printing results.
The same principle can be applied to camera exposures, if so desired,
by the following plan. Select some suitable place on the under side of
the tripod plate, as, for instance, the screw head, and fasten a small
string, having a weight attached to it about 39 in. from the point of
support. Like the swinging lamp, this device too, will beat seconds. For
convenience, one of the tripod legs may be marked to indicate the length
of string needed, so that the operator at any time can quickly fasten a
string, measure off the right length on the tripod leg, attach a bunch
of keys, a knife, or any other convenient weight, even a small stone, and
have a second-beating pendulum for time exposures.--Contributed by F. B.
Lambert, Chicago.
Supports for Camp-Fire Utensils
The sketch shows how to make a standard or support to hold cooking
utensils over a camp fire. The main part or stake is made of a piece of
gas pipe, on one end of which is turned an ordinary coupling, Fig. 1. This
is used to furnish a strong head when the stake is driven into the ground.
The rings and supports for the utensils are made of heavy wire bent into
the shape required to hold the respective vessels. The sketch, Fig. 2,
shows the manner of shaping the wires.
[Illustration: A Piece of Gas Pipe Constitutes the Standard with Wires
Attached for Holding the Utensils (Fig. 1, Fig. 2)]
A Rotary Tuning Coil
The rotary tuner shown in the sketch was designed by a correspondent
of Modern Electrics. The circle is cut from 3/4-in. stock, 1 in. wide
and well covered with insulating material. It is then wound with No. 24
single cotton-covered copper wire so that the coils will lie flat. All
the arms are of 1/4-in. square brass. The supports are smaller in section.
Sliders are mounted on the ends of the long arms and are kept in place by
setscrews.
[Illustration: Tuning Coil... (Fig. 1)]
[Illustration: ...and Wiring Diagram (Fig. 2)]
The insulation on the wire is removed with a small piece of sandpaper
pasted on a block of wood. This should be temporarily fastened to the
revolving lever at the point where the contact is wanted, then the lever
is turned until the insulation is removed. The wiring diagram shows the
location of the tuning coil in the line.
Preparing Sheet Music for Turning
Each page on sheet music having three or more pages should be cut 1/4 in.
shorter than the preceding page, as shown by the dotted lines in the
sketch. This will enable the player to quickly turn the pages one at a
time.--Contributed by Chas. Homewood, Waterloo, Ia.
[Illustration: Leaves Cut for Turning]
Toy Parachute Cut-Away for Kite Lines