parachutes to the lines and have some device to drop them when they are
at a great height. In Fig. 1 is shown how the parachute is dropped by the
burning of a piece of punk.
Another method is shown in Fig. 2. It is only necessary to send a piece
of paper or cardboard along the line and when it strikes the wire coil A
(Fig. 2) the part B slides out of the loops C, the end D will then fall
and disengage the loop G on the end of the parachute string. The wires E
and F are twisted around the kite string.--Contributed by Thos. De Loof,
Grand Rapids, Michigan.
[Illustration: Two Parachute Drops (Fig. 1, Fig. 2)]
How to Make an Electric Furnace
[Illustration: The Furnace Consists of a Flowerpot in Which a Crucible is
Set, and on Either Side the Carbon Holders are Fastened to the Base (Fig.
5)]
A small electric furnace that will be very serviceable in a laboratory
may be made as follows:
First procure a small clay flowerpot, about 4 in. in diameter at the
bottom, and also a small clay crucible, about 2 in. in diameter at the
bottom and at least 1 in. less in height than the flowerpot, and having
as nearly as possible the same slope to its sides as the pot. Now obtain a
small quantity of asbestos compound and pack it around the small crucible
inside the flowerpot. Make sure the crucible is in the exact center of
the flowerpot and that their tops are even with each other. Assuming that
ordinary electric-light carbons are to be used, which are about 1/2 in. in
diameter, drill two 5/8-in. holes, exactly opposite each other, through
the walls of the flowerpot and asbestos compound so that they enter the
crucible about 3/4 in. above its bottom on the inside. A suitable lid for
the furnace may be made from 1/4-in. sheet asbestos and should be large
enough to cover the top of the flowerpot.
[Illustration: Details of the Base, Rod and Handle for Each Carbon Feed,
Which is Attached to the Large Base on One Side of the Furnace (Fig. 1,
Fig. 2)]
[Illustration: (Fig. 3)]
The feeds and supports for the carbon electrodes are constructed as
follows: Procure two pieces of 1/8-in. brass, 1 in. wide and 9 in. long.
Cut a 1/8-in. groove lengthwise in the center of these pieces to within
1-1/2 in. of each end, as shown in Fig. 1. Drill four 1/8-in. holes, AA,
in each piece, a 3/8-in. hole, B, in one end and a 3/16-in. hole, C, in
the other end. Now bend the ends up at right angles to the remainder of
the piece along the dotted lines shown at D and E. Next obtain two 3/8-in.
rods, 10-3/16 in. long. Turn one end of each down to a 3/16-in. diameter
for a distance of 3/8 in. From that point thread the same end of the rods
for a distance of 6 in. Drill a 1/16-in. hole in each end of the rods a
little less than 1/4 in. from the ends. The dimensions of the rods are
given in Fig. 2. Two small rubber or wooden handles, similar to the one
shown in Fig. 3, should now be made and fastened to the large ends of
the rods by means of 1/16-in. steel pins. Obtain two pieces of brass of
approximately the following dimensions: 1 in. by 1 in. by 3 in. Drill
four holes in each of these pieces as shown in Fig. 4. The hole H should
be just large enough to allow the carbon to enter, or about 1/2 in. in
diameter. The hole G should be tapped to take a 1/4-in. machine screw,
the hole F should be threaded so that the threaded rods will enter, and
a small binding post should be mounted on a lug fastened in the hole J.
Cut away one end of this piece as shown in Fig. 4 until it is a little
less than 1/8 in. in thickness, or so it will enter the grooves cut in
the brass strips.
[Illustration: (Fig. 4)]
The parts of the furnace are now ready to assemble, which may be done as
follows: Procure a piece of well seasoned board, hard wood if possible,
about 1 in. thick, 8 in. wide and perhaps 20 in. long. Cover one side of
this board and the edges with some 1/8-in. sheet asbestos. Now place the
flowerpot in the exact center and then mount the grooved brass strips one
on either side of it with the longest dimension parallel to the longest
dimension of the board and the inside end about 1 in. from the side of the
pot. The end with the 3/16-in. holes should be next to the pot. Assemble
the parts of the carbon feeds and then cut out some circular disks of
asbestos to place under the flowerpot so as to raise it to such a position
that the holes in its sides will be on a line with the carbon rods. Three
long screws should now be placed in the board, forming the base, in such
a position as to hold the flowerpot always in place. This completes the
furnace proper, which is shown in Fig. 5.
The furnace can now be put into operation provided there is a suitable
current rheostat to connect in series with the carbon arc to prevent an
excessive current being taken from the line. If such a rheostat is not
available, a serviceable one may be made as follows:
Obtain two pieces of 1/16-in. sheet iron, 6 by 6 in., that are to form
the end plates. Cut off the corners of one piece so as to form an octagon
and drill a number of 1/8-in. and 1/4-in. holes in it, as shown in Fig.
6. Bend the corners of the other piece down along the dotted lines marked
L, Fig. 7, and then make a second bend in each corner along the dotted
lines K, so that the outermost portion of the corner is parallel to the
main portion of the piece. Drill a number of 1/8-in. holes in this piece
as indicated. A 3-in. opening should be cut in the center of this piece to
give access to the interior of the completed rheostat. Now obtain eight
3/8-in. iron rods, 10 in. long. Drill and tap each end of these rods to
accommodate a 1/8-in. machine screw. Wrap several layers of thin sheet
asbestos around each rod and tie it in place with some thread. These rods
should now be fastened between the end plates by means of a number of
iron machine screws. Mount four back-connected binding posts on the plate
shown in Fig. 6, making sure they are insulated from the plate by means
of suitable bushings and washers.
[Illustration: Detail of the Upper and Lower End Plates That are Used in
Making a Rheostat (Fig. 6, Fig. 7)]
Procure a small quantity of No. 14 gauge iron wire. Fasten one end of
the wire under the head of the screw holding one of the binding posts in
place and then wind it around the rods about 20 times, making the distance
between the turns equal to the diameter of the wire. After winding on the
20 turns, attach a short piece of wire to the main wire and fasten the
free end of the short piece to one of the other binding posts. Wind on 20
more turns, and make another connection to the third binding post, then
complete the winding and attach the end to the remaining binding post.
Different amounts of this resistance can now be connected in series with
the arc by changing the connections from one binding post to another. The
rheostat may be located on a bracket fastened to the wall, but care must
be taken not to place it in such a position that it will come into contact
with inflammable material. As an extra precaution, the circuit should be
properly fused.
Cleaning Brass Articles
Embossed or undercut brass work may be easily cleaned by boiling the
pieces in a strong solution of caustic soda or lye, and then immersing
them in a mixture of hydrochloric acid, 6 parts; water, 2 parts, and
nitric acid, 1 part, until they become covered with a dark deposit. Take
them from the solution and remove the black substance with a fine scratch
brush. After cleaned in this manner, rinse in hot water and dry in hot
sawdust.
A fine orange-yellow tinge may be given to the brass by substituting
an equivalent weight of powdered alum for the nitric acid in the
solution.--Contributed by Mrs. Richard F. Pohle, E. Lynn, Mass.
A Whetting Block
A handy tool gauge for sharpening the various tools about the household is
made of a block of wood with the sides of one end cut sloping in different
degrees so that each will serve to secure the proper slant of the cutting
edge on a certain tool.
The block of wood with the corners cut is shown in Fig. 1, and the manner
of whetting a chisel is shown in Fig. 2.--Contributed by Will Parker,
Wibaux, Mont.
[Illustration: The Sloping Edges on the Block of Wood and the Manner of
Whetting a Chisel (Fig. 1, Fig. 2)]
* * * * *
A cardboard cut the same size as a page and fastened
with paper clips in the center of a magazine will
prevent the pages from folding over when the magazine
is placed in a bookcase.
Submarine Photographs
A photographer at a seashore resort, wishing to increase his sales of
souvenir postal cards, rigged up a device for producing negatives to make
"submarine" pictures. The device consisted of an aquarium, about 40 in.
long, 18 in. high and 6 in. wide. The aquarium was designed to stand on
edge or the narrow way, and was equipped with rocks, living sea moss,
kelp, and some fish, and the bottom was covered with sand and shells.
[Illustration: The Camera Set in Front of the Aquarium Ready to Make a
Submarine Picture]
A canvas was hung back of the aquarium and the camera set in front at such
a distance as to make a negative of only the water and the prepared sea
bottom. Very fine views that will give the appearance of being made at
the bottom of the sea can be produced.
Mending Paper-Pulp Utensils
Pails, washtubs, and other receptacles made of paper pulp, when cut and
worn, may be easily mended with adhesive tape. After this is applied to
the place to be mended, give the mended part a coating of paint, and when
the paint has dried, the surface is given another coat to match the color
of the article mended. Leaks may be entirely stopped in this way at a very
reasonable cost.--Contributed by Katharine D. Morse, Syracuse, N. Y.
A Homemade Mailing Tube
A photograph or manuscript may be sent through the mail unmounted without
the danger of being broken by placing it in a tube made as follows: For
an 8 by 10-in. photograph procure a piece of cardboard 6 by 10 in., plain
mounting board preferred, and cut halfway through the card in three places
as shown by the dotted lines in Fig. 1. Then fold it in a triangular shape
as shown in Fig. 2. It is easy to make such a tube to fit any photograph
or manuscript to be mailed.--Contributed by A. H. Schaefer, Buffalo, N. Y.
[Illustration: The Bends in the Cardboard are Made on Lines Equal
Distances Apart to Form a Triangle (Fig. 1, Fig. 2)]
Cutter for Lace Leather
[Illustration]
Lace leather may be easily cut with an ordinary pocket knife having a
U-shaped block fitted on the edge of the blade. The width of the opening
should be exactly the same as the thickness of the leather and the width
of the lace is determined by the distance between the blade and the
depth of the notch. Several places can be provided for the blade to cut
different widths of lacing.--Contributed by A. K. Runkle, Kinsman, O.
Refinishing Chairs
When refinishing chairs, a good way to get at the bottom part is to turn
the chair upside down and place its seat on the seat of another chair. The
legs and rungs can thus be easily cleaned and varnished.--Contributed by
A. Mandeville, Ware, Mass.
An Electric Gas Lighter
A very simple and inexpensive electric gas-lighting device is shown in
the accompanying illustration. The gas is ignited by means of an electric
spark which is produced between the two parts A and B of an electric
circuit. This circuit is composed of a source of electrical energy, such
as a number of dry cells, a kick coil, the connecting leads, and a special
operating switch for opening and closing the circuit to produce the spark.
The circuit is normally open, but as the lever controlling the gas valve
is moved from one position to the other, by pulling the chains, the lever
C is caused to move through a certain arc. Now, as this lever C moves,
its upper end passes the projecting point B, which is attached to the
upper portion of the burner, and the electric circuit will be completed
and broken. Just as the point A leaves contact with the point B an arc
will be produced. This arc is greatly intensified by the kick coil, which
acts as a sort of reservoir in which energy is stored while the circuit
is closed, and upon opening the circuit this stored energy is given out
by the kick coil and increases the size of the arc.
[Illustration: The Igniting Points as They are Attached to a Gas Burner
to Work Automatically]
The points A and B should both be made of platinum, as other metals
will not withstand the extremely high temperature of the arc. Pieces of
platinum that will serve very nicely for the purpose may be obtained from
an old incandescent lamp. The piece B is mounted on a brass collar, D,
by means of a small screw, E. The brass collar D is held in place by the
screw F, which draws the two ends together. This collar must be insulated
from the stem or fixture by some thin sheets of mica. The upper end of the
piece of platinum B should be just high enough to come within the lower
edge of the gas flame.
Now mount an arm, C, on the valve stem so that it stands in a vertical
position when the lever to which the chains are attached is in a
horizontal position. Bend this arm into the form shown in the figure and
cut its upper end off so that it is about 1/2 in. below the outwardly
projecting end of the piece of platinum B. Drill a small hole in the upper
end of C, and insert a piece of platinum and run some solder around it.
Then the complete burner and valve are mounted on the gas fixture, and
from the collar D an insulated wire is run to the point where the battery
and kick coil are to be located. The gas fixture itself is to form one
side of the electric circuit, and one terminal of the battery should be
connected to the gas pipe as shown in the figure.
A kick coil may be made as follows: Procure a small quantity of rather
small soft-iron wire and cut a sufficient number of 8-in. lengths to make
a bundle about 7/8 in. in diameter. From some good writing paper make a
tube, 8 in. long and 7/8 in. in outside diameter. Use at least six layers
of paper and glue the various layers together in forming this paper tube.
After the tube has dried thoroughly, fill it with the pieces of iron
wire until it is perfectly hard. Cut from some 1/2-in. hard wood, two
pieces, 3 in. square, and drill a 7/8-in. hole in the center of each of
these to a depth of 3/8 in. Now glue these pieces to the completed core
and the winding can begin as soon as the glue is dry. Wind on this spool
six layers of double cotton-covered No. 18 gauge wire, insulating the
various layers from each other with several thicknesses of good writing
paper. This coil is then mounted on a wooden base and suitable terminals
provided.
At least four dry cells will be required to give satisfactory results.
Bear in mind that the gas must be escaping from the burner when the arc
is formed. The adjustment of the arm A, as given above, may result in the
gas valve being closed when the arc is formed, and the device will then
fail to operate. If this is the case, the arm C should be loosened and
moved back so that the circuit is broken at a later time while the valve
is being moved from the "off" to "on" position. The circuit should be
closed for some little time before it is opened so that some energy may
be stored in the kick coil. If the wire A is made long enough to project
a short distance above B, it will result in the circuit being closed for
a longer time than it would if they just touched.
Stretching Tight-Fitting Shoes
A tight-fitting shoe can be stretched by filling it tightly with oats
dampened in water and packing some old paper in the top. The grain will
quickly swell and, as the leather will get softened by the dampness, the
shoe will be rapidly stretched. Allow time for the oats to dry out before
removing them.--Contributed by Fred L. King, Islip, New York.
Pad for a Percolator
[Illustration]
To prevent heating the bowl of a percolator and burning the handle, as
often happens when it is placed on a stove, use an ordinary asbestos pad
with a hole cut in the center as shown, just large enough to admit the
foot of the percolator.--Contributed by Mrs. G. W. Coplin, Bay City, Mich.
* * * * *
If a motorcycle engine is raced while on the stand,
the cylinder will heat, often with the result that it
is ruined.
Compass Time Chart
A very instructive little instrument can be easily made for telling the
time of any location on the globe. Its construction is extremely simple.
Draw a circle, about 1-1/2 in. in diameter, on a piece of paper and then
draw a larger circle, about 4 in. in diameter, around the first one.
Divide the circles into 36 equal parts and draw lines from one circle to
the other like the spokes in a wheel. These divisions will be 10 deg., or
40 minutes of time, apart. They should be numbered around the outside,
commencing at a point marked 0 and marking the numbers by tens each way
until they meet at 180 deg.
[Illustration: A Time Chart for Telling the Hour of the Day at Any Place
on the Globe]
Using a map of the eastern and western hemispheres, write the names of the
different cities on the globe in their respective degrees of longitude.
The center, or inside, of the smaller circle is divided into 24 divisions
representing the hours of the day and night, and these are marked from
1 to 12, the left side being forenoon, and the right, afternoon. The
noon mark must be set on the line nearest to the location in which the
instrument is to be used. For instance, if the instrument is to be used
in Chicago, it is set as shown in the sketch.
The disk is mounted on a thin piece of board and a pin is driven through
the center from the back side so as to make a projecting point on the
upper side on which to place the magnetized needle of a compass. The
needle may be taken from any cheap compass.
All that is necessary to do, to tell what time it is in any other city or
country, is to turn the instrument so that the name of that place points
toward the sun, when the north end of the compass needle will point on the
disk to the time it is in that city or locality.--Contributed by Henry J.
Marion, Pontiac, Mich.
Reversing Switch for Small Motors
A reversing switch made as follows will be found very serviceable in
reversing the direction of the rotation of small motors, changing the
polarity of electromagnets, etc.
[Illustration: Diagram of the Wiring to a Small Motor and the Details of
the Switch]
A diagram of the connections to the switch and on the switch base is given
in the sketch, and in this particular case the switch is shown connected
to a small toy motor. The field of the motor is represented by A, the
armature by B; and C, D, E, and F are four binding posts mounted on the
base of the switch; G, H, and I are three contacts; J and K are terminals
of the switch blades, and L a single-pole switch. The two blades of the
reversing switch have their lower ends fastened to the terminals J and K,
and their upper ends, which are indicated by arrow heads, may be moved
over the contacts G, H, and I. For the position of the reversing switch
shown by the full lines, J is connected to G and K to H. When the switch
is thrown to the right-hand position, as shown by the dotted lines, J is
connected to H and K to I. It is obvious that the direction of the current
through the armature B will be reversed when the reversing switch is
thrown from one position to the other. The direction in which the armature
rotates will change, due to the reversal in direction of the current
through it. The same results could be obtained by reversing the current
in the field winding A. But it must always be borne in mind that in order
to reverse the direction of rotation, the current must be reversed in the
armature only or in the field only, not in both.
The above switch may be constructed as follows: First, procure a piece
of well-seasoned hard wood, say maple, 1/2 in. thick, 2-1/2 in. wide and
4 in. long. Round off the corners and the edges of this piece on one side
and drill the holes indicated in the sketch. The four corner holes should
be of such a size as to accommodate the screws used in mounting four small
back-connected binding posts. The remaining holes should be 1/8 in. All
these holes should be countersunk with a 3/8-in. bit to a depth of 1/4 in.
on the under side.
Cut from some 1/16-in. sheet brass two pieces, 2-3/4 in. long, 1/2 in.
wide at one end and 1/4 in. at the other, and round their ends. Drill a
1/8-in. hole through the larger end of each of these pieces, 1/4 in. from
the end, and also a hole through each, 1-1/4 in. from the narrow end.
The last two holes should be threaded for 1/8-in. machine screws. Obtain
five 1/8-in. brass bolts, 1/2 in. long. File the heads of three of these
bolts down to a thickness of approximately 1/16 in. and mount them in
the holes G, H and I. Before mounting anything on the base the grooves
indicated by the heavy dotted lines should be cut in the under side so
that the various points may be properly connected by conductors placed
in the grooves. Now mount the two pieces of sheet brass upon the base by
means of the remaining two bolts, which should pass through the holes J
and K. A 1/16-in. washer should be placed between the pieces of brass and
the wooden base.
Procure a piece of 1/8-in. fiber, 1-1/4 in. long and 3/8 in. broad. Drill
two 1/8-in. holes in this piece, one in each end, so that they are 1 in.
apart. Drill a third 1/8-in. hole in the center and fasten a small handle
to the piece of fiber. Now mount this piece upon the two pieces of brass
that form the blades of the switch by means of two small 1/8-in. brass
machine screws.
Two small brads should be driven into the wooden base so as to prevent
the possibility of the switch blades moving beyond their proper position.
Two pieces of 1/16-in. fiber should be placed between the heads of the
screws G and H, and H and I, to prevent the ends of the switch blades from
dropping down on the wooden base.
Adjustable Rod for Potted Plants
Procure a brass sash-curtain rod of the telescoping kind and stick the
solid part into the soil close to the plant and tie it to the rod. As the
plant grows move the tubular part of the rod upward to correspond with the
height of the plant. This makes a good support and is not so unsightly as
a stick.--Contributed by Gertrude M. Bender, Utica, N. Y.
Wrench for Different-Size Nuts
A very handy wrench can be made from a piece of square bar, shaped as
shown and fitted with a handle. The joint at A may be halved and riveted
or a weld made as desired. The size of the bar and the space between the
parts will depend on the size of nuts to be turned.
[Illustration: The Sloping Notch in the Wrench Permits Its Use on Nuts of
Various Size]
A Simple Sextant
A sextant for measuring the latitude of any place can be easily
constructed as follows: While a board, 1 in. thick, 6 in. wide, and
12 in. long is about right for the instrument, any dimensions can be
used, providing the line AB is at perfect right angles to the level of the
sights C and D. The sights are better to use, although the upper edge of
the board, if it is perfectly straight, will do as well. If it is desired
to use sights, a slight groove is cut in the upper edge; a V-shaped piece,
cut from tin, is fastened at one end, and a small pointed nail is driven
in at the other. In doing this, be sure to level the bottom of the V-notch
and nail point so that in drawing the line AB it will be at perfect right
angles to a line between the sights. A tack is driven into the side of
the board at the upper edge, a line fastened to it and a weight tied to
the lower end which should swing below the lower edge of the board.
[Illustration: The Main Part of the Instrument Consists of a Board with
a Plumb Attached]
The instrument is placed in such a manner that the North Star is sighted,
as shown, and the point on the lower edge of the board is marked where the
line E comes to rest. A line is then drawn from A to the point marked and
the angle F is measured with a protractor. The number of degrees in this
angle will be approximately equal to the number of degrees in the latitude
of that place.
[Illustration: The Two Stars at the End of the Great Dipper are Pointers
to the North Star]
The North Star is easily located by reason of its position relative to the
Great Dipper, as shown by the diagram.--Contributed by Carlos Harrison,
Anderson, Ind.
How to Make a Taper Ferrule
Having occasion to make a taper ferrule of irregular form, a pattern from
which to cut the material was made as follows: A mandrel of the desired
shape was made, a piece of writing paper, soaked in water, wrapped around
the mandrel, and a piece of twine wound over it, coil after coil like
the thread on a spool. This was allowed to dry thoroughly, using a little
heat. The string was then removed and a longitudinal cut made in the paper
while on the mandrel. When opened this paper formed the pattern.
A piece of metal was cut from the pattern and the edges were brought
together and brazed with spelter. The point of the mandrel was driven
through a piece of block tin, about 1/2 in. thick. The mandrel was then
removed, the ferrule was placed on it, and both then started in the hole
made in the tin and driven through it. As the mandrel with the ferrule
passed through the tin, the metal was shaped exactly to the mandrel. It
is best to oil the hole in the tin slightly. Tin is preferable as it is
harder.--Contributed by James H. Beebee, Rochester, N. Y.
How to Make a Continuously Ringing Bell
The bell shown in the accompanying diagram is known as the continuously
ringing type, and has quite a field of usefulness in connection with
burglar alarms, door-bell signals, telephone signals, etc. The operation
of the bell proper is identical with that of the ordinary vibrating bell
and, in addition, there is a circuit controlled by the armature of the
bell, which is normally open, but becomes closed as soon as the armature
is drawn over. The closing of this circuit by the operation of the
armature amounts to keeping the push button in the bell circuit depressed,
and the bell will continue to ring until the latch A is restored by
pulling the cord B.
[Illustration: An Ordinary Vibrating Bell Used as a Continuously Ringing
Bell, and the Wiring Diagram]
Any ordinary vibrating bell may be converted into a continuously ringing
bell as follows: In the armature, C, mount a short metal pin, D, and
round off its under side slightly. A latch, A, should now be constructed
similar to the one shown in the sketch and mounted in such a position that
its left end will rest on the outer end of the pin D when the armature,
C, of the bell is in its extreme outer position. The length of the latch
should be such that its left end will drop off the end of the pin D, due
to the action of the spring E, when the armature C is drawn over by the
electromagnets F, thus allowing it to come into contact with a spring
G, which is electrically connected to the terminal of the bell marked H.
The latch A is connected to one side of the line, as shown in the sketch,
so as to include the bell winding and battery in a local circuit that is
formed by the latch coming in contact with the spring G. The end of the
latch should not interfere with the free operation of the armature when it
is resting on the spring G. A cord, B, attached to the outer end of the
latch, is used in restoring it, and at the same time stopping the bell
from ringing. The tension in the spring E should be so adjusted that the
operation of the latch is sure and firm, yet not too stiff.
A Mission-Style Inkstand
Having a couple of good-sized ink bottles of the ordinary type lying
around, I fashioned a mission-style stand for them out of a piece of
yellow pine, 2 in. wide and 3 in. long, set on another piece of pine large
enough to project all around on all four sides of the block, for a base.
The wells were cut out with a wood chisel, and the parts fastened together
with screws. The supports were four brass-head or upholsterer's tacks.
The finish was flat black.--Contributed by James M. Kane, Doylestown, Pa.
[Illustration: Two Pieces of Pine Shaped to Receive the Inkwells and
Finished in Mission Style]
Raising Dents in Wood
The imprint of a hammer on finely finished wood caused by a glancing blow,
or otherwise, may be removed in the following manner: Pour enough wood
alcohol on the dented spot to cover it, then light the alcohol and allow
it to burn out. The heat will expand the wood and raise it enough so that
the spot can be planed and smoothed in the usual manner.--Contributed by
W. F. Elwell, Waltham, Massachusetts.
Carrying Two Pails in One Hand
When it is necessary to carry two small filled pails in one hand and
a package in the other it will be found a very difficult job, if the
contents are liquid. Procure a stick of sufficient size to carry the
weight of the pails and cut a small notch in each end to admit the bail.
Place a pail on each end of the stick and take hold in the center, or, if
the pails are not equally filled, a little to one side of the center.
[Illustration: Two Filled Pails can be Readily Carried by Placing the
Bails on the Ends of a Stick]
Preserving Paint in Open Cans
To keep paint from drying out in an open can it is necessary to exclude
the air from the oil. This can be done by procuring an air-tight paper
sack, which is tested by blowing into it. Set the can into the sack and
tie it tightly with a cord. Mixed paint will be kept in a working state
in this manner.
Jelly-Straining Stand
[Illustration]
Procure a board, 7/8 in. thick and 18 in. square, and cut a hole, about
1 ft. diameter, in the center. Fasten posts, 4 ft. long, to each corner.
Screw hooks are located around the edge of the hole to catch into
the cloth used for holding the fruit. The stand is high enough to be
convenient and admit a vessel beneath to catch the juice.
Renewing Dry Batteries
It is a well-known fact that dry cells commence to deteriorate from the
time they are manufactured, and it is a matter of considerable uncertainty
in purchasing cells to know whether they will continue to be efficient
for their supposed natural life under the existing conditions of service,
or for only a small part of this period. When the voltage of a dry cell
falls below a certain value it is usually discarded and replaced by a new
one, which often means quite an expense. The following simple suggestion
will enable one to renew the prematurely exhausted cell with very little
trouble and slight expense, so that its period of usefulness will be
extended for a length of time, at least equal to that for which it could
be used if put into service immediately after its manufacture.
[Illustration]
The procedure in renewing the cell is as follows: A casing is placed
outside of the zinc-containing case, having inside dimensions a little
greater than the zinc cup. The space between the zinc cup and case is
filled with a dry electrolyte, which, upon the addition of moisture, sets
up a chemical action with the exterior surface of the zinc, and the latter
having been perforated, causes electrical action to be again produced.
The casing, or cup, to be used outside the zinc cup should be made of a
waterproof material. The electrolyte instead of being placed between this
cup and the zinc in a powdered form, as might be expected, should be held
by several layers of blotting paper, formed into a cylinder of the proper
diameter to fit snugly on the outside of the zinc cup. This porous cup
should be impregnated with a solution containing the following materials
in the approximate amounts given: Muriate of ammonia, 10 parts; bichromate
of potash, 4 parts, and chloride of sodium, 4 parts. After the porous
cup has thoroughly soaked in the above solution it should be dried by
passing a roller over its external surface when it is mounted on a wooden
cylinder of proper diameter. The moisture-proof cup may be formed outside
the porous cup by covering the latter with several coats of waterproofing
paste and winding on several thicknesses of common manila paper, each
layer of paper being treated with the paste. A disk of cardboard, properly
treated, should be placed in the end of the cylinder to form the bottom,
and the edge of the manila paper folded in over it and pasted in place.
The pasteboard covering surrounding the zinc cup of the cell should be
removed and the surface of the zinc thoroughly cleaned. The coal tar in
the top of the zinc cup should be removed by tapping around the edge with
a hammer, and a large number of small holes should be made in the walls
of the cup with a sharp instrument. Then put the cell within the porous
cup and fill the top with clear water, preferably rain water. A chemical
reaction will immediately take place between the outer surface of the
zinc and the chemicals contained in the material forming the porous cup,
and the terminal voltage of the cell will be practically the same as it
was when the cell was new. The water, of course, must be replenished from
time to time on account of evaporation, and the useful life of the cell
can be prolonged for a considerable time. A part cross section of a cell
treated as described above is shown in the accompanying sketch.
Workbench Equipment for a Table Top
The average home mechanic with a few tools seldom has a place to work and
is usually without a workbench. As this was my case, I constructed a bench
equipment that I could easily clamp to the kitchen or other table and thus
have the necessary tools at hand for work. A plank, 2 in. thick, 10 in.
wide and 18 in. long, was planed and smoothed up on all sides, and a vise
and a bench pin were fastened on one edge.
[Illustration: The Bench Top can be Quickly Attached to Any Table Top
without Harming It]
To the under side of the same edge two blocks were securely fastened,
as shown, and to these blocks two other pieces were fastened with
hinges. With a bolt, running through from the top, and a thumb nut used
underneath, these pieces are used as clamps for holding the bench to the
table top. The top can be removed and set away in a closet when not in
use.--Contributed by Wm. H. Hathaway, Nutley, N. J.
A Nonsticking Drawer Guide
[Illustration]
The guide shown is nonbinding and has been found thoroughly practical
after several years' use on furniture. The guide A consists of a piece
of wood, about 1-1/8 in. square, with a concave cut in its upper edge,
the width being about 3/4 in. and the depth such as not to cut through
the extending end projecting over the crossbar B. The drawer sides have a
half-round edge on the bottom edge to run in the groove in the guide. The
difference in width between the groove in the guide and the rounding edge
on the drawer side causes the drawer always to ride snugly without binding
as the wood expands or contracts with changes in the weather.--Contributed
by Herman Hermann, Portland, Ind.
A Milk Stool
The stool is made of three pieces of board and a piece of round, or stake,
iron. The appearance and manner of construction are clearly shown in the
illustration. The seat board is sawed out to fit the circumference of the
bucket to be used, and the iron is also bent to this curve and fastened
to the board as shown. The little shelf on the front support holds the
bucket at the right height, and keeps it clean and out of the way of the
cow's foot while milking.
[Illustration: A Milk Stool Having a Place to Keep the Bucket Clean and
at the Right Height]
Sounder for Wireless-Telegraph Messages
The owner of an amateur wireless outfit often has reason to regret that
he cannot let some of his friends listen to a message at the same time as
he himself. The magnifier described in the following permits all those
present in the room to hear the message, provided, of course, they are
able to interpret the Morse alphabet by sound.
[Illustration: The Phonograph Horn as It is Connected to a Detector for
Transmitting the Messages]
A very simple means, making the message audible at a distance of about
10 ft., is to attach a phonograph horn, or a horn of cardboard or metal,
to the telephone receiver, but a much better arrangement can be made as
shown in the diagram, in which A represents the antenna or aerial; B, the
detector, and C, the receiver. Procure a small microphone, D, placing its
mouthpiece closely against the receiver--for the sake of clearness the two
are separated in the diagram--and connect the former with a battery, F,
of two or three dry cells, in series with the microphone of an ordinary
telephone transmitter provided with a large horn. The effect obtained by
this simple means will be surprising.
Joint for Mission Furniture
The mortise for this joint is made in the usual manner, the only
requirements being that the mortise is run through the piece, and the
tenon is cut 1/8 in. shorter than the depth of the mortise or the width
of the piece it is entering. The end of the tenon and the mortise is then
covered with a piece of metal, fastened with screws as shown. The metal
can be of any desired material and beveled on the edges. This makes a very
good knock-down joint for mission furniture.--Contributed by H. R. Allen,
Cheyenne, Wyoming.
[Illustration: Metal Covering and Holder for a Tenon and Mortise Joint on
Mission Furniture]
A Towel Roller
A substantial, convenient and nonrusting towel roller can be made from
8 or 9 of the familiar wood handles on bundle carriers and a length of
brass curtain rod. The bracket ends can be shaped from any piece of
wood of suitable dimensions. The rollers and ends can be finished as
desired.--Contributed by F. E. S., E. Lynn, Mass.
An Electric Shaving Mug
The general use of electricity in the home has opened up a new field in
the way of heating and cooking utensils. While these utensils are sold by
electric-supply houses, some of them can be easily made at home and answer
the purpose just as nicely. One of these is the electric shaving mug.
[Illustration: Detail of the Parts for the Construction of an Electric
Shaving Mug. The Heating of Sufficient Water for a Shave can be
Accomplished at a Nominal Cost (Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5)]
A mug that will stand heat is the first thing required, and an aluminum
cup of standard shape and design, which can be bought in almost every
town, will do perfectly well. These cups are spun from a flat sheet and
have no seams to open and leak, and it is necessary that no holes be
drilled in the cup as it is impossible to make such a hole watertight. The
heating element must be fastened to the mug with a clamp. The clamp will
also allow the heating coil to be removed for repairs without injury to
the mug. The bottoms of these mugs have a flange which makes a recessed
part and in this the heating element is placed.
The legs of the mug are made of sheet brass as shown in Fig. 1, one of the
three having an enlargement near its center with a hole for an insulating
button (Fig. 2), of "transite" or some other material, to hold the supply
cord in place.
The clamp for holding the heating coil in place is shown in Fig. 3. This
clamp has a screw in the center to tighten it in place. The legs and clamp
may be nickelplated if desired.
The heating coil is shown in Fig. 4 which is a coil of flat "Nichrome"
wire, or ribbon as it is called, 12 ft. long, 1/16 in. wide and 3/1000 in.
thick. This is equal in cross section to a No. 26 gauge wire. To wind
this coil, procure a block of wood, 7/8 in. thick and about 4 in. square,
with a 1/2-in. hole in the center for an axis or pivot. Clamp a 1/2-in.
rod in a vise so that the block can be rotated about it. Begin at the
center and fasten one end of the ribbon to the block, leaving about
2 in. projecting for a connection, then proceed to wind the ribbon in a
spiral coil, separating each turn from the preceding one with a strand of
asbestos cord. A small section of the coil is shown in Fig. 5, in which A,
or the light part, represents the asbestos insulation, and B, or the black
lines, the heating element. The insulation may be obtained by untwisting
some 1/8-in. round asbestos packing and using one of the strands. This
cord insulates each turn of the ribbon from the other and the current must
travel through the whole coil without jumping across from one turn to the
other. The whole coil must be closely wound to get it into the limited
space at the bottom of the mug.
Before taking the coil from the block, rub into its surface a little
asbestos retort cement, or a cement composed of a mixture of silicate of
soda and silica, or glass sand. This mixture, when dry, will tend to hold
the coil together and the current may be passed through the coil to test
it as well as to bake it in its coiled shape.
[Illustration: (Fig. 6, Fig. 7)]
The support for the heating coil is made of a piece of 5/16-in. asbestos
wood or transite. Cut it to fit into the recessed bottom of the mug, then
with a chisel remove the material in the top to form a depression 1/16 in.
deep to receive the coil with its top flush. The leads of the coil are
run through the disk. The surface of the coil is then plastered evenly
with retort cement. The legs are fastened to a second piece of insulating
material with round-head brass machine screws, 1/2 in. long, with nuts.
The heads of these screws are shown in Fig. 6, the nuts being above the
brass and between the two insulating pieces.
The ends of the heating ribbon are brought through the lower insulating
disk and attached to binding posts as shown. The leads may be covered with
tape to prevent any short circuit.
The mug uses 3-1/2 amperes at 110 volts, either direct or alternating
current, and it will cost about 3 cents an hour to operate it. Care should
be taken to use a separable attachment for connecting, as an ordinary lamp
socket may be burned out by turning off the current, it being adapted only
to a small capacity.
In assembling the parts, several pieces of mica should be placed between
the coil and the metal of the mug to insulate the coil from the mug.
A Handbag Lock
[Illustration]
The pickpocket finds it easy to unsnap a handbag and remove some of the
contents, especially in crowded places. To make it less easy for the
pickpocket, I fixed my mother's handbag as shown in the sketch. I used a
chain which had served its day holding a small coin purse--any small chain
will do--by passing it through the links that hold the handle and winding
it once or twice around the snap fasteners to hold them securely closed.
The chain may be either shortened enough to make it convenient to hold
with the handle of the handbag, or may be left long and used over the
shoulder under the coat, thus making it possible to have both hands free
for shopping while the handbag hangs by the side. This leaves a person
free from the worry of taking care that the bag is not laid down somewhere
and lost. The bag may be easily opened by unwinding the chain after
loosening it by raising the bag slightly.--Contributed by Wm. Waterhouse,
Aurora, Ill.
An Emery-Cloth Holder
Emery cloth in sheets is very easily spoiled around a workbench. Oil or
other fluids used on work are apt to drop on it and when wet for a short
time the abrasive is useless. The illustration shows a tin holder, A, that
can be placed on the under side of the bench where space is not required
for drawer room.
[Illustration: A Receptacle for Emery Cloth Made of Sheet Metal or Tin
and Fastened to a Bench]
The portion cut out of the bottom of the holder B is to enable the workman
to easily grasp the sheets of emery cloth. As the holder is on the under
side of the bench, there is little danger of any liquid or other substance
spoiling the sheets. The sheets are also within easy reach.--Contributed
by F. W. Bently, Huron, S. D.
The Operation of the Compass
After trying to tell a few small boys what a compass is, they wanted a
practical illustration--something they could see. Not having a compass or
knowing where to locate one handily, I used a piece of cork with needles
and a needle for a pivot and found it very satisfactory. The method used
is shown in the sketch.
It is best not to magnetize both needles unless care is exercised in
maintaining pole relationship, or they will oppose each other and not
point to the north. The extreme ends or the heads of the needles must be
opposites, the head of one negative and the head of the other positive.
[Illustration: Two Large Needles in a Cork Balanced on a Central Needle
to Make Them Revolve Easily]
If a good compass is brought carelessly in contact with a magnet,
the poles may become reversed and the north end will no longer point
to the north but to the south until the current has been reversed
again by bringing the opposite pole of the magnet in contact with the
compass.--Contributed by W. H. Albright, Bellevue, O.
Thawing Out Frozen Pipes
When the water pipes connecting a range boiler become frozen, get a
plumber and avoid an explosion of the water back. If, however, the frozen
pipe is a cold-water pipe in no way connected with the hot-water boiler,
it can be thawed out as follows:
[Illustration: The Faucet is Turned Upwards and Opened and Alcohol Poured
In on the Ice]
Procure some grain alcohol--not denatured or wood alcohol--and after
turning the spigot upward or upside down, as shown, open it and pour
in the alcohol. When the water begins to flow turn it to its proper
position.--Contributed by James M. Kane, Doylestown, Pa.
A Wire Clothespin
[Illustration]
The pin is made of galvanized wire, A, 8 or 10 in. long, wound spirally,
B, on a round surface, such as a broom handle, to make the holding part.
The ends are fastened together as shown. The space between the spiral
turns makes the cloth-holding part.--Contributed by Wesley H. Freeman,
Palestine, Tex.
Vent for Pouring Heavy Liquids
A tube placed in a jug or bottle as shown in the sketch will assist
greatly in removing molasses or heavy liquids. The tube can be placed in
the receptacle without getting the liquid inside by holding a finger over
the outer end. The air can easily enter without disturbing the flow of
the liquid.--Contributed by Homer Payear, Owensboro, Ky.
[Illustration: The Vacuum Caused by the Flow of Heavy Liquids is Easily
Overcome by the Air Tube]
A Hat Hanger
[Illustration]
Procure a piece of 1/8-in. wire, about 3 ft. long, bend it into the shape
shown in the sketch, and sharpen the projecting end. Drive this into
the wall above a coat hanger. This provides a better hat hanger than the
ordinary hook.--Contributed by John D. Watt, Roxbury, Mass.
Repairing a Broken Tenon on a Chair Post
[Illustration]
Instead of cutting off the four posts to make new tenons where one tenon
was broken I used a metal piece made from a short length of bicycle
tubing, as shown. The tube was slotted two ways to make four parts which
were turned out and flattened. The remaining end of the tube was slipped
over the broken post and the four parts were fastened with screws to the
under side of the chair seat.--Contributed by Chas. H. Roberts, Calumet,
Mich.
Substitute for an Iron-Holder Knob
[Illustration]
The wood knob on the holder for my irons became charred from the heat and
finally broke away from the pin. The pin would get so hot in continued
use that it could not be moved without burning my fingers. I remedied the
difficulty by attaching a short string to the handle and the pin. A pull
on the string with the forefinger readily released the iron. I have found
this better than the knob, as it is handier to use.--Contributed by Mrs.
H. C. Dixon, Johnstown, Pa.
An Egg-Frying Pan
The frying of eggs in an ordinary frying pan is accompanied with some
difficulty in removing them when they are cooked without breaking the
yolk. Then, sometimes, the pan is too hot and the egg sticks to the pan
and the top remains uncooked. A much better way is to shape a piece of
sheet metal or tin as shown in the sketch to place the egg in and use
it in the ordinary pan. It will not burn the egg, and the egg can be
lifted out of the pan and easily slipped on a plate or toast when it is
cooked.--Contributed by W. A. Jaquythe, San Diego, Cal.
[Illustration: A Metal Plate for Use in an Ordinary Frying Pan to Cook
Eggs without Scorching Them]
A Sander Mandrel for the Lathe
A cylindrical sander for use in the lathe can be easily made of two pieces
of wood, turned to a diameter that will take the stock size of sandpaper,
and clamped together with pinch dogs at the ends. One edge of the
sandpaper is clamped between the pieces and then it is wrapped around the
wood, the opposite edge being glued to the starting edge, as shown at A.
The dimensions given are for a 9 by 12-in. sheet of sandpaper. The sander
is easily placed in the lathe centers when needed, and the sandpaper may
be replaced at any time.--Contributed by James T. Gaffney, Chicago.
[Illustration: A Wood Mandrel for Attaching Regular Sheets of Sandpaper
to Make a Lathe Sander]
How to Construct a Simple Galvanometer
A galvanometer is an instrument used to detect the presence of an
electrical current in a circuit or to measure the value of the current in
amperes. The operation of practically all galvanometers is based upon the
same principle, and they differ chiefly in mechanical construction and
the relative arrangement of their different parts.
A very simple galvanometer, that will give quite satisfactory results,
under favorable conditions, may be constructed as follows: Turn from a
piece of hard wood a ring having dimensions corresponding to those given
in the cross section, Fig. 1. Fill the groove in this ring to within
1/8 in. of the top with No. 18 gauge double-cotton-covered copper wire,
insulating the different layers from each other by means of a layer of
good bond paper. The winding may be started by drilling a small hole
through the side of the groove, as close to the bottom as possible, and
allowing about 6 in. of the wire to protrude through it. The outside
end may be terminated in a similar manner, and the two ends should
be on the same side of the ring, or as near each other as possible. A
protecting covering of bookbinder's paper is placed over the winding
and the completed ring given a coat of shellac. The electric current to
be detected or measured is to pass around the winding of this coil and
produce an effect upon a compass needle mounted in its center. In order
that the current may produce a maximum effect upon the needle, the coil
should be mounted in a vertical position.
[Illustration: The Wood Ring for the Coil and Its Holding Stirrup (Fig.
1, Fig. 2)]
The base upon which the ring is to be mounted may be cut from some 1/2-in.
hard wood. It should be circular in form and about 5 in. in diameter, and
have its upper edge rounded off and shellacked to improve its appearance.
The ring is mounted in a vertical position on this base, which may be done
as follows: Cut a flat surface on each of the flanges of the ring so that
it will stand in a vertical position and the terminals of the winding will
be as near as possible to the surface upon which the ring rests. Then form
a stirrup from some thin sheet brass, similar to that shown in Fig. 2, so
that it will fit tightly over the ring and its outwardly projecting ends
will rest upon the base of the instrument. Small wood screws are used in
fastening the stirrup to the base. The fastening may be made more secure
by cutting a groove across the inside of the ring for the stirrup to fit
in, Fig. 3, thus preventing the possibility of the ring moving through
the stirrup. Two holes should be drilled in the base for the terminals of
the winding to pass through, and it would be best to cut two grooves in
the side of the ring for these wires so as to prevent their coming into
contact with the metal stirrup. Two back-connected binding posts, A and
B, Fig. 3, are mounted on the base and the ends of the winding attached
to them. The wires should be placed in grooves cut in the under side of
the base, and the screws used in fastening the binding posts should be
countersunk.
[Illustration: Galvanometer as It is Used to Detect the Presence of an
Electrical Current (Fig. 3)]
A short compass needle is then mounted on a suitable supporting pivot
in the center of the coil. This compass needle will always come to rest
in an approximate north and south position when it is acted upon by the
earth's magnetic field alone. If now the plane of the coil be placed in
such a position that it is parallel to the direction of the compass needle
(no current in the coil), the magnetic field that will be produced when a
current is sent through the winding will be perpendicular to the magnetic
field of the earth and there will be a force, due to this particular
current, tending to turn the compass needle around perpendicularly to
its original position. There will be a deflection of the needle for all
values of current in the coil, and this deflection will vary in value as
the current in the coil varies. The mere fact that the compass needle
is deflected due to a current in the coil gives a means of detecting a
current in any circuit of which the coil is a part, and the degree of
this deflection affords a means of measuring the current, the value of
the different deflections in terms of the current in the coil having been
experimentally determined by sending a known current through the coil and
noting the positions of the compass needle for each value of current used.
In order to determine the deflection of the needle, a scale, C, Fig.
3, must be mounted directly under the compass needle and a pointer, D,
attached to the compass needle so that any movement of the needle results
in an equal angular displacement of the pointer. The compass needle,
E, should be short and quite heavy, say, 5/8 in. in length, 1/16 in. in
thickness and 1/4 in. in width at its center, and tapering to a point at
its ends. It should be made of a good grade of steel, tempered and then
magnetized by means of a powerful electromagnet. The reason for making
the compass needle short is that it will then operate in practically a
uniform magnetic field, which exists only at the center of the coil.
On account of the needle being so short and in view of the fact that
it comes to rest parallel to the coil for its zero position, it is best
to use a pointer attached to the needle to determine its deflection, as
this pointer can be made much longer than the needle, and any movement of
the needle may be more easily detected, as the end of the pointer moves
through a much larger distance than the end of the needle, and since it
may be attached to the needle, at right angles to the needle's axis, the
end of the pointer will be off to one side of the coil and its movement
may be easily observed. The pointer should be made of some nonmagnetic
material, such as aluminum or brass, and it should be as long as it may
be conveniently made. A suitable box with a glass cover may be provided
in which the needle, pointer and scale may be housed. The construction
of this box will be left entirely to the ingenuity of the one making the
instrument.
[Illustration: The Electric Circuit, Showing Connections for Finding the
Value of a Current in Calibrating (Fig. 4)]
In order to use this instrument as an ammeter, it will be necessary to
calibrate it, which consists in determining the position of the pointer
for various values of current through the coil. It will be necessary to
obtain the use of a direct-current ammeter for this purpose. The winding
of the galvanometer, ammeter, battery and a variable resistance of some
kind should all be connected in series as shown in the diagram, Fig.
4. Allow the compass needle to come to rest under the influence of the
earth's magnetic field and then turn the coil into such a position that
it is as nearly parallel with the needle as possible. This corresponds
to the zero position, and the instrument must always be in this position
when it is used. The position of the ends of the pointer is now marked on
the scale for different values of current, first with the current in one
direction and then in the opposite direction. The deflection of the needle
will, of course, reverse when the current is reversed.
The effect produced by any current upon the compass needle can be changed
by changing the number of turns in the coil. In measuring a large current,
a few turns of large wire would be required, and in measuring a small
current, a large number of turns of small wire could be used. In other
words, the size of the wire will depend upon the current it is to carry
and the number of turns in the coil will depend upon the magnetic effect
the current is to produce, which is proportional to the product of the
number of turns and the current, called the ampere-turns.
Experiments with Camphor
Place a few scrapings from gum camphor in a tumbler of water and watch
the phenomenon. The scrapings will go through all kinds of rapid motions
as if they were alive. A drop of turpentine, or any oil, will stop their
maneuvers. This experiment will show how quickly oil spreads over the
surface of water.
Boiling Cracked Eggs
Eggs with the shells cracked can be boiled in the ordinary manner without
danger of the white boiling out, if they are first wrapped in tissue
paper. As soon as the paper becomes wet it will cling so tightly to the
shell that the cracks are effectively closed.
A Trousers Hanger
A very serviceable hanger can be easily made of two clothespins of the
clip type and about 2 ft. of large wire.
[Illustration: Clothesline Clips Joined Together with a Wire and Used as
a Trousers Hanger]
The wire should be bent into the shape shown at A with a loop about 1 in.
in diameter as a hanger. The ends of the wire are slipped under the hooks
on the sides of the clothespins, which are fastened to the trousers as
shown in B.--Contributed by Olaf Tronnes, Evanston, Ill.
Removing Tight-Fitting Can Covers
[Illustration]
Tight-fitting covers on lard and similar pails can be readily removed by
tying a stout cord loosely below the cover, then placing an ordinary nail
under the cord and twisting it. This will tighten the cord around the can
evenly, which will loosen the cover.
A Skimming Spoon
A handy skimming spoon can be made very quickly of an ordinary spoon of
any size desired. Slits are sawn across the bowl in the manner shown,
using a hacksaw. The illustration is self-explanatory.--Contributed by G.
H. Holter, Jasper, Minn.
[Illustration: The Straight Cuts Sawn Across the Bottom of the Bowl
Provide Openings to Drain Out the Liquid]
How to Make Falling Blocks
Procure a thin board large enough to cut six blocks, 2 in. wide and 3 in.
long; also 2 yd. of cotton tape, 1/4 in. wide, and some very small tacks.
Cut the board into pieces of the size mentioned, and number two of them
on both surfaces, 1, 2, 3, and 4. Cut off three pieces of tape, 4-3/4 in.
long, and on the side of block 1 tack one piece of tape in the center at
one end, and the other two pieces at each edge on the opposite end, all
being on one side of the block as shown. Take the other block and lay the
side numbered 4 up, then draw the two strips of tape on the edges of block
1 under it and back to the end of the surface on block 4, and tack them on
this surface at the edges as shown. The center tape is passed under block
4 and turned over the opposite end and tacked. This is clearly shown in
the sketch. Thus the second block will hang from either end of block 1 by
simply folding them together and separating the ends.
[Illustration: Set of Blocks Joined with Tape So That They Appear to Fall
from the Top]
Mark the sides of the third block 5 and 6, and place it with the two
others so that the sides numbered 2, 3, and 5 will be up. Cut off three
more pieces of tape, 4-3/4 in. long, and tack them on as shown, being
careful not to tack through any of the first three pieces. Put on the
fourth block in the same manner as the third block was attached to the
second, and so on, until all the blocks are attached.
Take hold of the first block on the edges and tip it as shown by the
arrow. The second block will then fall as shown by the second arrow, and
the third block falls away in the same manner, and so on, down to the
end.--Contributed by Wayne Nutting, Minneapolis, Minn.
Writing Name Reversed on Paper Placed on Forehead
The following is an entertaining experiment in a party of young people.
One of those present is asked if he can write his name, and will, of
course, answer "yes." He is then subjected to the following test: He is
asked to sit down in a chair, a paper, folded several times, is placed on
his forehead, a lead pencil is handed him and he is asked to write his
name on the paper. As little time as possible to reflect should be left
him; if he hesitates, he should be told to just go ahead, and in most
cases it will be found that he starts writing his name at the left temple
and, to the amusement of the others present, writes it in the way of many
left-handed persons, that is, so that it is legible only when held in
front of a mirror, unless one is practiced in reading reversed writing.
Use for an Old Table
An old table of the extension type, that may have a post broken, can be
used against the wall in a kitchen as a work table. If there is a damaged
part, that side is removed by sawing the crosspieces of the table in two
and attaching it to the wall against the leaf which is turned in a reverse
position.--Contributed by A. S. Thomas, Gordon, Can.
[Illustration: One Half of the Table is Removed and the Remaining Part
Fastened to the Wall]
How to Make a Small Rheostat
In operating small motors there is as a rule no means provided for
regulating their speed, and this often is quite a disadvantage, especially
in the case of toy motors such as used on miniature electric locomotives.
The speed, of course, can be regulated by changing the number of cells
of battery by means of a special switch, but then all the cells are not
used the same amount and some of them may be completely exhausted before
the others show any appreciable depreciation. If a small transformer is
used with a number of taps taken off the secondary winding, the voltage
impressed upon the motor, and consequently the speed, can be changed by
varying the amount of the secondary winding across which the motor is
connected.
[Illustration: Diagram Showing the Connections for a Small Motor Where a
Rheostat Is in the Line (Fig. 1)]
But in both these cases there is no means of varying the speed gradually.
This can, however, be accomplished by means of a small rheostat placed
in series with the motor. The rheostat acts in an electrical circuit in
just the same way a valve does in a hydraulic circuit. It consists of a
resistance, which can be easily varied in value, placed in the circuit
connecting the motor with the source of electrical energy. A diagram of
the rheostat is shown in Fig. 1, in which A represents the armature of
the motor; B, the field; C, the rheostat, and D, the source of electrical
energy. When the handle E is in such a position that the maximum amount
of resistance is in circuit there will be a minimum current through
the field and armature of the motor, and its speed will be a minimum.
As the resistance of the rheostat is decreased, the current increases
and the motor speeds up, reaching a maximum value when the resistance
of the rheostat has been reduced to zero value. Such a rheostat may be
used in combination with a special switch F., as shown in. Fig. 2. The
switch gives a means of varying the voltage and the rheostat takes care
of the desired changes in speed occurring between those produced by the
variations in voltage.
[Illustration: Diagram of a Small Motor Where a Rheostat and Switch Are
in the Line (Fig. 2)]
A very simple and inexpensive rheostat may be constructed as follows:
Procure a piece of thin fiber, about 1/16 in. thick, 1/2 in. wide and
approximately 10 in. long. Wind on this piece of fiber, after the edges
have all been smoothed down, a piece of No. 22 gauge cotton-covered
resistance wire, starting about 1/4 in. from one end and winding the
various turns fairly close together to within 1/4 in. of the other end.
The ends of the wire may be secured by passing them through several small
holes drilled in the piece of fiber, and should protrude 3 or 4 in. for
connecting to binding posts that will be mounted upon the base of the
rheostat.
Now form this piece of fiber into a complete ring by bending it around
some round object, the flat side being toward the object. Determine as
accurately as possible the diameter of the ring thus formed and also its
thickness. Obtain a piece of well seasoned hard wood, 1/2 in. thick and
4-1/2 in. square. Round off the corners and upper edges of this block and
mark out on it two circles whose diameters correspond to the inside and
outside diameters of the fiber ring. The centers of these circles should
be in the center of the block. Carefully saw out the two circles so that
the space between the inside and outside portions will just accommodate
the fiber ring. Obtain a second piece of hard wood, 1/4 in. thick and
4-3/4 in. square, round off its corners and upper edges and mount the
other pieces upon it by means of several small wood screws, which should
pass up from the under side and be well countersunk. Place the fiber ring
in the groove, but, before doing so, drill a hole in the base proper for
one end of the wire to pass through. Two small back-connected binding
posts should be mounted in the corners. One of these should be connected
to the end of the winding and the other to a small bolt in the center of
the base that serves to hold the handle or movable arm of the rheostat in
place. These connecting leads should all be placed in grooves cut in the
under side of the base.
[Illustration: A Cross Section of the Rheostat, Showing the Connections
through the Resistance (Fig. 3)]
The movable arm of the rheostat may be made from a piece of 1/16-in. sheet
brass, and should have the following approximate dimensions: length,
2 in.; breadth 1/2 in. at one end, and 1/4 in. at the other. Obtain a
1/8-in. brass bolt, about 1 in. long, also several washers. Drill a hole
in the larger end of the piece of brass to accommodate the bolt and also
in the center of the wooden base. Countersink the hole in the base on the
under side with a 1/2-in. bit to a depth of 1/4 in. On the under side of
the piece of brass, and near its narrow end, solder a piece of thin spring
brass so that its free end will rest upon the upper edge of the fiber
ring. A small handle may be mounted upon the upper side of the movable
arm. Now mount the arm on the base by means of the bolt, placing several
washers between it and the upper surface of the base, so that its outer
end will be raised above the edge of the fiber ring. Solder a short piece
of thin brass to the nut that is to be placed on the lower end of the
bolt, and cut a recess in the countersunk portion of the hole in the base
to accommodate it. When the bolt has been screwed down sufficiently tight
a locknut may be put on, or the first nut soldered to the end of the bolt.
If possible, it would be best to use a spring washer, or two, between the
arm and base.
The insulation should now be removed from the wire on the upper edge
of the fiber ring with a piece of fine sandpaper, so that the spring
on the under side of the movable arm may make contact with the winding.
The rheostat is now complete with the exception of a coat of shellac. A
cross-sectional view of the completed rheostat is shown in Fig. 3.
Folding Arms for Clothesline Posts
The inconvenience of using a number of clothesline posts and the limited
space available resulted in the making of a clothesline post as shown in
the sketch. The entire line is supported on two posts, which should be
about 6 in. square and are set in concrete. The upper ends of the posts
are equipped with two arms, hinged to the sides of the posts in such a
manner that the inside ends of the arms will meet on top of the post when
they are in a horizontal position. Each arm is provided with three wood
pins, equally spaced for the line. The arms are supported in a horizontal
position by two bars of metal at the center, as shown. Holes are bored
into the sides of the posts to receive the pins when the arms are at rest.
[Illustration: A Post That Provides a Way to Hold Six Lines Taut without
the Use of Props]
A small box is fastened to one post, to provide a place for the
clothesline and the clothespins. The line, when put up, gives space for
an entire washing without the use of a prop, as the line can be drawn taut
enough to hold the garments.--Contributed by Olaf Tronnes, Evanston, Ill.
A Folding Bookrack
Having need of a bookrack which I could pack away in my trunk and still
have room for my clothes, I made one as follows: I procured a piece of
pine, 5/8 in. thick, 6 in. wide and 18 in. long, and laid out the plan
on one side. Holes were drilled in the edges, 3/4 in. from the ends, to
receive 1-1/2-in. round-head brass screws. The design for the ends was
sawn out with a scroll saw and the edges smoothed up with fine sandpaper,
whereupon the surfaces were stained and given a coat of wax. The screws
were put in place to make the ends turn on them as on a bearing. In
use the ends were turned up.--Contributed by Spencer Hall, Baltimore,
Maryland.
[Illustration: The Ends of the Rack Turn Down, Making a Straight Board]
A Simple Balance
Having use for a balance in a laboratory and being unable to procure any
scales at the time, I hastily rigged up a device that served the purpose
as well, as the work did not require very great precision. An elastic band
and a short piece of string was procured and the band cut open. The string
was then fastened around the beaker as shown, and the whole suspended from
a shelf.
[Illustration: A Graduate Scale Used in Connection with an Elastic Band
to Make a Simple Balance]
Into the beaker was then poured 100 cubic centimeters of water and the
stretch of the elastic band noted by the displacement of a knot in the
string in respect to the scale on a graduate, placed beside the beaker.
The length of the elastic was then changed until the knot was exactly
opposite the 100-division mark on the graduate scale. Then, since the
elongation of the elastic band follows Hook's law, the extension of the
band to the amount of one scale division means an added weight of one gram
in the beaker.--Contributed by L. Horle, Newark, New Jersey.
An Ink Eraser
A good knife eraser for ink can be made from a discarded or broken ruling
pen. One of the parts, or nibs, is cut off close to the handle and the
remaining one sharpened on both edges at the point. This instrument is
better than a knife or the regular scratcher, because the cutting edge
will shave the surface of the paper or tracing cloth and not roughen or
cut it. Erasing done with this knife will readily take ink without further
preparation of the surface.--Contributed by Warren E. Crane, Cleveland, O.
[Illustration: One of the Nibs on the Ruling Pen Sharpened and Used as an
Eraser]
Gate Fasteners
[Illustration]
Buttons on gates or small doors are apt to become loose and then drop
down, thereby allowing the gate or door to become unfastened. The ordinary
button is shown at A where it is loose and turned by its own weight. If
the button is cut as shown at B, it will remain fastened, even if it is
loose on the screw or nail.--Contributed by A. S. Thomas, Amherstburg,
Ont.
A Compensating Siphon
The homemade siphon shown in the sketch consists of two rubber corks and
a glass tube with a rubber hose connected to it. The cork A is used as a
bearing and support on the edge of the tank. The position of the cork B on
the tube determines the distance that the mouth of the tube will be under
the surface of the liquid, also to some extent the sensitiveness of the
apparatus. However, the principle of the device is the buoyant effect of
the water and the lever action of the rubber tube which is attached.
[Illustration: The End of the Pipe is Kept Just under the Surface of the
Liquid at all Times]
The one that I made had a tube 14 in. long, and the cork B was 1-3/4 in.
in diameter, 1 in. thick, and weighed about 1/10 of a pound. The practical
application of this siphon will be found in sieve tests where it is
necessary to collect the residue on the bottom of the tank while drawing
off the liquid at the surface, also in oil-storage tanks where it is not
wished to disturb the dirt or other residue which collects on the bottom
of the tank.--Contributed by James Hemphill, Jr., Duquesne, Pennsylvania.
A Polarity Indicator
Lines in a cable or the ends of connections at a distance from the
battery must be tested to determine the polarity. Where a large amount
of this work is to be done, as in automobile and motorboat repairing,
it is necessary to have an indicator to save time. A cheap indicator for
this purpose can be made of a 6-in. test tube having its ends sealed and
inclosing a saturated solution of ammonium chloride (sal ammoniac) and
water. The sealed ends are made by inserting a piece of wire through
a cork and, after forcing this tightly into the end of the test tube,
covering it with sealing wax.
[Illustration: A Simple Pocket Indicator for Finding the Negative Wire in
Battery Cable Lines]
To use, connect the terminals to the battery lines, and the end of the
wire in the solution giving off bubbles is the negative wire.--Contributed
by H. S. Parker, Brooklyn, N. Y.
Small Steam-Engine Cylinders Made from Seamless Brass Tubing
In making a small steam engine it was desired to use seamless brass tubing
for the cylinders. To have them exactly alike a piece of tubing of the
right size and of sufficient length for both cylinders was fitted on a
wood mandrel, A, and the ends trued up in a lathe. As these cylinders were
to fit into holes bored in a steel bedplate, it was necessary to have a
flange at one end. A groove was turned in the tubing B in the center, and
as a final operation a parting tool was used on the line CD. This resulted
in a pair of cylinders flanged to fit the bedplate.--Contributed by Harry
F. Lowe, Washington, D. C.
[Illustration: A Wood Mandrel Used to Face the Ends and Turn Flanges on
Tubing for Cylinders]
A Pocket Direct-Current Voltmeter
The assembled drawings of a very simple voltmeter are shown in Fig. 1, and
its operation is as follows: The moving portion consists of a pointer, or
needle, A; a small permanent magnet, or armature, B, and a counterweight,
C, mounted upon a small steel shaft, D. The ends of this steel shaft are
pointed and rest in bearings provided in the U-shaped piece of brass E,
which is rigidly fastened to the fiber base F, by means of two screws.
The permanent magnet B, carried on the shaft D, is at all times under
the magnetic influence of the permanent horseshoe magnet, G, which is
fastened, by means of thin brass straps, H H, and small screws, to the
base F, so that the ends of the armature B are directly above the poles
of the horseshoe magnet. The armature B will assume the position shown
in the sketch when it is acted upon by the permanent magnet G alone and
the moving system is perfectly balanced. A solenoid, J, is mounted in the
position shown. When there is a current in its winding its soft-iron core
will become magnetized and the magnetic pole produced at the lower end
will produce a magnetic force upon the armature B, with the result that
the armature will be rotated either in a clockwise or counter-clockwise
direction, depending upon its polarity and the polarity of the end of
the core adjacent to it. Thus, if the left end of the armature has north
polarity, the right end south polarity, and the lower end of the core is
magnetized to a south polarity the armature will be rotated clockwise,
for the left end, or north pole, will be attracted by the lower end of
the iron core, which is a south pole, and the right end will be repelled.
This is in accordance with one of the fundamental laws of magnetism which
states that magnetic poles of unlike polarity attract each other and those
of like polarity repel each other. The amount the armature B is rotated
will depend upon the relative effects of the pole of the solenoid and the
permanent magnet G. The strength of the pole of the solenoid will depend
upon the current in its winding and the number of times the current passes
around the core, or the number of turns in the winding. In other words,
the strength of the pole of the solenoid varies as the product of the
current and the number of turns, which is called the ampere-turns. The
same magnetic effect can be produced by a large current passing through
a few turns or a small current passing through a relatively large number
of turns. This simple relation of current and turns gives a means of
adjusting the current capacity of the instrument so that a full-scale
deflection of the needle will correspond to any desired maximum current.
The instrument may be used as either a voltmeter or as an ammeter, and
its operation will be identical in each case. The resistance of the
voltmeter, however, will be many times the resistance of the ammeter,
as it will be connected directly across the line, while the ammeter will
always be in series in the circuit in which it is desired to measure the
current. The following description and suggestion as to how to proceed in
the construction of this instrument may be useful to those who undertake
to build one. All the minor details and some of the dimensions will be
omitted in the description, but these can be easily supplied.
[Illustration: The Parts as They are Assembled to Make a Pocket Voltmeter
for Direct Currents (Fig. 1)]
Procure a piece of hard rubber or fiber, about 1/4 in. in thickness and
of sufficient size to cut from it a disk, 2-1/2 in. in diameter. Make a
small horseshoe magnet from a piece of the very best steel obtainable,
and magnetize it to as high a strength as possible. This magnet is made
of a piece of steel, 1/8 in. thick, about 3/8 in. in breadth, and of such
length that the overall lengthwise dimension of the completed magnet will
be about 1-7/8 in. and the distance between the inside edges of the ends
a little greater than 1/2 in. Fasten the completed magnet to the base F by
means of two or three straps, made from some thin brass, and small machine
or wood screws.
Then cut from some 1/16-in. sheet brass a piece having the general
appearance and dimensions shown at A, Fig. 2. Bend the ends of this piece
over at right angles to the center portion along the dotted lines. Drill
the hole at the upper end and thread it for a 1/16-in. machine screw. By
means of a pointed drill, make a small recess at the lower end directly
opposite the first hole. This small recess is to form the lower bearing
for the shaft supporting the moving system, while a small recess cut
centrally in the end of a screw, mounted in the upper hole, will form
the upper bearing. The screw placed in the upper hole need be only about
3/16 in. long. The holes in the two wings are for mounting this piece upon
the fiber base, as shown in Fig. 1.
The shaft for supporting the moving system is made of a piece of a hatpin.
It is about 13/16 in. long and its ends are pointed so that they will turn
freely in the bearings provided for them.
The armature is cut from a piece of 1/16-in. sheet steel. It is made about
3/4 in. long, 5/16 in. wide at the center, tapering to 1/8 in. at the
ends. A hole is drilled in its center so that it may be forced onto the
shaft. It is mounted so that its lower surface comes about 1/4 in. from
the lower end of the shaft.
Then cut from some very thin brass a piece, that is to form the needle,
1/4 in. wide at one end and tapered to a point at the other, the total
length being about 3 in. Drill a hole in the large end of this piece,
the same size as the shaft and 1/2 in. from the end. This piece is not
fastened to the shaft until some of the other parts are completed.
[Illustration: Details of the Supports for the Coil and for the Needle,
or Pointer, Shaft (Fig. 2)]
The spool upon which the winding is to be placed is made as follows:
Procure a piece of very soft wrought iron, 1-1/4 in. long and 1/4 in.
in diameter, to form the core. The ends of the spool are made of thin
brass and are dimensioned as shown in Fig. 2, at B and C. The piece shown
at B is to form the lower end of the spool, and is bent at right angles
along the dotted line. The two holes at the lower edge are for attaching
the end of the spool to the fiber base. The piece shown at C forms the
upper end of the spool and at the same time a back upon which the scale
of the instrument is mounted. The holes in the lower edge are threaded
for small machine screws, as it will be necessary to fasten this piece
to the base by means of screws that pass through the base from the under
side, as shown in Fig. 1. Bend the upper and lower portion of the piece
over at right angles to the center portion along the dotted lines. Make
sure that the large hole in the center of each end piece is of such size
that it will fit very tight on the end of the wrought-iron core. Force
the end pieces onto the ends of the core a short distance, say, 1/16 in.,
and hammer down the edges of the core so that the end pieces cannot be
easily removed. In fastening the ends to the core be sure that the parts
that are to rest upon the base are parallel with each other and extend
in opposite directions; also that the ends are at right angles to the
core. Then insulate the inner portions of the completed spool with several
thicknesses of onion-skin paper, or any good-quality, thin writing paper,
and shellac. The winding will be described later.
Mount the spool and support for the bearings upon the base so that they
occupy the positions, relative to each other, indicated in Fig. 1. A
paper scale is then mounted upon the brass base provided for it by means
of some thin shellac. The upper and lower lines for the scale can now be
drawn upon the paper, using the center of the screw at the lower end of
the needle as a center. These lines are best placed about 1/8 in. apart
and not nearer the edge of the base than 1/4 inches.
The needle is bent over at right angles 5/16 in. from the center of the
shaft. Another right-angle bend in the needle is then made so that the
pointed end will be about 1/16 in. above the surface of the scale when the
large end of the needle is fastened to the shaft 3/8 in. from the upper
end of the latter. Turn the needle on the shaft so that the pointer is
at the left end of the scale when the moving system is at rest. The shaft
must be exactly vertical when this adjustment is made. Cut the end of the
needle down until its end is midway between the two scale lines. Solder
the needle to the shaft, and then place a sufficient quantity of solder
on the broad end to balance the system perfectly and allow it to come to
rest in any position when the armature B is not influenced by any magnetic
field.
A containing case for the instrument may be made as follows: Make a
cylinder from some thin sheet brass, having exactly the same inside
diameter as the base, and a height a little greater than the vertical
distance from the lower surface of the base to the upper surface of the
needle. Also a disk from some thin sheet brass, having a diameter 1/8 in.
greater than the outside diameter of the cylinder. Round off the edges
of this disk and cut a curved slot in it directly over the scale, about
3/8 in. wide and of the same length and form as the scale. Solder the
disk to one end of the cylinder, placing the solder all on the inside.
To prevent moisture from entering the case, fasten a piece of thin glass
on the under side of the slot in the disk by means of some shellac and
several pieces of brass soldered to the disk and bent down onto the glass.
The case can now be fastened to the base by means of several screws,
passing through its lower end into the edge of the base. Two small binding
posts are mounted on the outside of the case, about 90 deg. apart and well
insulated from each other and from the case, to serve as terminals for
the instrument.
The instrument is now complete with the exception of the winding. Since
this is to be a voltmeter and it is always desirable that a voltmeter take
as small a current as possible, the winding must consist of a relatively
large number of turns of small wire, each turn carrying a small current.
The difference in the construction of different instruments necessitates
that their winding contain a different number of turns in order that a
given voltage may produce a full-scale deflection. A little experimenting
with different windings is the easiest means of determining the proper
size of wire and number of turns to meet individual requirements. After
adjusting the winding so that the maximum voltage it is desired to measure
produces a full-scale deflection, the scale is calibrated by marking
the positions of the needle in accordance with those of the needle of a
standard instrument connected in parallel with it. In marking the scale
of an ammeter, connect the instruments in series. Remember that if the
instrument is to be used as an ammeter, it must have as low a resistance
as possible and that to prevent undue heating, the wire must have ample
cross section.
If difficulty is experienced due to the continuous vibration of the
needle, although the current be practically constant, this trouble can be
greatly reduced by mounting a paper wind vane on the moving system, which
will tend to dampen its movement.
Falling Leaves in a Nature Scene
Use an ordinary pasteboard box, a shoe box or larger, and cut out one end.
Fasten the box to the ceiling by means of pasteboard strips. One end of
these strips is pasted on the bottom of the box and the other ends tacked
to the ceiling. Fit a piece of board, 1/2 in. thick, into the open end of
the box so that it will slide easily back and forth on the inside. Place
this slide in the back of the box, attach a string to it and run this
through double tacks placed in the ceiling and to the side wings.
[Illustration: The Box as It is Prepared to Fasten on the Ceiling for
Dropping the Leaves]
Have the box almost full of autumn leaves, and when the slide is pulled
slowly by the operator, they will be pushed, one or two at a time, out of
the open end, and will drift down to the stage as naturally as if falling
from trees, making quite a realistic scene.--Contributed by Miss S. E.
Jocelyn, New Haven, Conn.
Home or Traveling Utility Bed Pocket
The pocket is made of cretonne with wire hooks attached on the upper edge.
The compartments are arranged as needs may require. It can be hooked on
the head, foot or side rail of the bed or used, as shown, in a sleeping
car. It provides a place to keep the slippers, gown and other necessities,
and can be rolled up and put in a bag.--Contributed by Harriette I.
Lockwood, Philadelphia, Pa.
[Illustration: Various Pockets for the Change Garments for Use at Home or
in Traveling]
A Paper Perforator
In an emergency an ordinary hacksaw blade may be made to serve very
acceptably as a paper perforator. The toothed edge is applied to the
paper and the reverse edge tapped with a mallet or hammer. A considerable
number of sheets may be perforated at one time, depending of course on
the thickness and softness of the paper.
Turning Brass Rings
[Illustration]
Occasionally an amateur has need of brass rings of round cross section,
and if their construction is not understood, the task is a difficult
one. If a piece of brass tubing, an old bushing or a cored piece is at
hand, a part of the work is already done. If not, a piece of stock with
large enough outside diameter should be chucked in the lathe and drilled
out with the right size of drill. A tin or pasteboard template should
be prepared the size of the ring section--a half circle is best, and it
is easiest made by drilling a hole in the tin and cutting it in two. An
inside boring tool and a turning tool are necessary. It is preferable to
shape the inside first, cutting it out roughly and checking up with the
template. The amount of inside cutting is shown in the drawing. A hard
scraper and emery cloth may be used for smoothing and polishing.
Turn and polish the outside and finally turn as far down on the inner
quarter as can be done without cutting off the finish, then polish and
cut it off. It only requires a little filing to smooth up the rim of rough
metal left.
[Illustration: The Electric Globes, as They Light beneath the Spray,
Illuminate the Top, and the Light Follows the Streams of Water So That
They Appear Like Streams of Light]
An Electric Fountain By Walter P. Butler
To make the grounds as attractive as possible for a lawn party given one
night, I constructed an electric fountain which at first appeared to be an
expensive proposition, but when completed the desired effect was produced
without any expense whatever, as I had the things used in its construction
on hand.
[Illustration: Details of the Different Parts to Construct the Electric
Fountain (Fig. 1)]
A light frame, 9 in. square, was made, of 3/4-in. material, as shown in
Fig. 1, and a grooved pulley was attached exactly in the center on the
under side of the crosspiece. A turned stick, A, 2 in. in diameter and
2-1/2 in. long, was fastened to the face of the pulley so that it turned
true as the pulley and frame revolved. A hole was then bored centrally
through the three parts, the frame crosspiece, the pulley, and the turned
stick, of a size to fit a spindle about 3/8 in. in diameter.
A box was procured, large enough for the frame to turn in freely, and a
block of wood was fastened centrally in its bottom, which had a 3/8-in.
pin set in a hole bored in the center. The pin may be of hard wood, but it
is better to use metal. A bolt, or piece of rod, will answer the purpose
of a pin very well.
A small battery motor--I had one on hand and did not need to purchase
one--was fastened to one side of the box so that its pulley was in line
with the pulley on the lower surface of the frame. The batteries to
run the motor were placed in the corner of the box, where the revolving
frame would not touch them. The motor may be of larger current capacity,
however, and run direct on the current used for the lamps.
[Illustration: (Fig. 2)]
About 1/2 in. from the lower end of the turned piece A, a brass strip
was fastened around it. This work should be neatly done, and the joint
soldered and smoothed, so that the outer surface will not catch on the
brush used to make the contact. This ring can be better made by cutting
the width from a piece of brass tubing of a size to fit on the turned
stick A. About 1-1/2 in. from the lower end four segments of a circle
were fastened so as to make a space of about 1/4 in. between their ends.
This construction is clearly shown in Fig. 2. A cross section, showing the
wire connections from the brass ring and segments to the lamps and where
they lead out on top, is shown at B. The contact brushes consist of brass
strips fastened with bolts to an upright, C, made of wood and attached to
one edge of the block in the bottom of the box. Two nuts are used on each
bolt, between which are fastened the lead wires from a source of current.
[Illustration: (Fig. 3)]
The wiring diagram is shown in Fig. 3. The wire D from the ring is run
to the brass base of each lamp, of which there are four. The wires E,
from each segment, are connected with solder to each screw ferrule of the
lamps, and the ends are left bare and open, as shown, between the lamps.
[Illustration: (Fig. 4)]
A lamp is fastened to each corner of the frame on top, as shown in
Fig. 4, with a piece of wire wrapped once around the screw ferrule and
the extending ends held with staples. The wire used should be heavily
insulated or, if it is of iron, a rubber tube slipped over it. A piece of
tin, or bright metal, is placed beneath each globe for a reflector.
[Illustration: (Fig. 5)]
A glass plate was used to cover the box, and a lawn spray of the fountain
type was placed on the glass. The globes, as they light beneath the spray,
illuminate the top and the light follows the streams of water so that they
appear like streams of light. Each light is turned on in succession as the
frame revolves within the box, and by using globes of different colors, an
exceedingly beautiful effect is obtained. If the bared ends of the wires
are twisted together between the globes, these will all glow at once.
A Mystery Coin Box
The effect of this trick is as follows: A small metal box, just large
enough to hold a half dollar and about 1/2 in. high, with a cover that
fits snugly over the top, is passed out to be examined, and when handed
back to the performer he places it on the finger ends of his left hand,
and a half dollar is dropped into it and the cover put on. The box is then
shaken to prove that the coin is still there. The performer then taps the
box with his fingers and picks it up with the other hand and the coin will
appear to have fallen through the bottom. Both the coin and box are then
handed out for examination.
This seemingly impossible effect is made when the performer places the
cover on the box. The box is resting on the fingers of the left hand and
the cover is held between the thumb and forefinger of the right hand, but
just before placing the cover on, the box is turned over with the right
thumb, and the cover is placed on the bottom instead of the top.
The trick can be done within a foot of the spectators without their seeing
the deception. It is a good plan to hide the box with the right hand when
placing the cover, although this is not necessary.
How to Make a Small Series Motor
The motor here described has been constructed and found to give very good
results. It is simple to build and the materials required can be easily
obtained. The armature core and field, or frame, are made of laminated
iron, instead of being cast as is often done by the manufacturers, which
is a decided advantage, as certain losses are thereby reduced, and its
operation will be improved by this type of construction especially if used
on an alternating-current circuit.
The machine will be divided into three main parts, the construction
of each of which will be taken up in turn and the method of procedure
discussed in detail. These parts are the completed armature, the field
and bearings, and the brushes together with suitable terminals and
connections.
The armature core is constructed from a number of pieces, having
dimensions that correspond to those given in A, Fig. 1. These pieces
are cut from thin annealed sheet iron, in sufficient number to make a
pile, 3/4 in. high, when placed on top of each other and firmly clamped.
It would, no doubt, be best to first lay out one of these pieces very
carefully and then cut it out and mark out the other pieces with the first
one as a pattern, being careful to file off all the rough edges on each
piece.
[Illustration: Details of the Armature Laminations and the Commutator
Segments, and the Method of Mounting Armature Core and Commutator (Fig.
1)]
Now obtain a piece of 1/4-in. iron or brass rod, 3-1/4 in. long, that is
to serve as a shaft upon which to mount the armature and commutator. This
rod is threaded for a distance of 7/8 in. on one end and 1-7/8 in. on the
other. Procure five brass nuts, 1/8 in. thickness, to fit the threads on
the rod. If possible have the ends of the rod centered before the threads
are cut, for reasons to be given later. Place one of the nuts on that end
of the shaft that is threaded for 7/8 in., and in such a position that
its inner surface is 3/4 in. from the end of the rod. Solder this nut
to the rod when it is in the proper place and remove all extra solder.
Drill a 1/4-in. hole in each of the armature stampings and place them on
the shaft, clamping them together with three small clamps, one on each
extension or pole. Then place a second nut on the shaft and draw it up
tight against the last stamping placed in position, and solder it to the
shaft. Next wind two or three layers of good strong tape around each of
the rectangular portions of the armature and then remove the clamps. Make
sure that all the edges of the different laminations are perfectly even
before applying the tape.
The shaft is then placed between two centers to determine whether the
core is approximately balanced and runs true. If the armature core is
unbalanced or not true, the trouble should be corrected before proceeding
with the remainder of the armature construction. The armature winding is
not to be put on the core until the commutator has been constructed and
mounted on the shaft.
The commutator consists of three pieces of thin sheet brass similar
to that shown at B, Fig. 1, mounted on the surface of a cylinder of
insulating material, 3/8 in. long and 7/8 in. in diameter. A 1/4-in. hole
is drilled lengthwise through the cylinder of insulating material. Bend
the pieces of brass around the outside of the cylinder, and turn all the
lugs, except the center one, marked C, over at right angles and put a
small nail or screw through the holes in the ends of the lugs into the
cylinder. These pieces of brass are equally spaced around the cylinder so
that all the lugs, not turned down, project in the same direction. Now
place a nut on the end of the shaft that extends the greatest distance
through the armature, so that its outside surface is 1/2 in. from the
surface of the end of the armature core next to it, and solder the nut to
the shaft. Place the commutator on the shaft so that the projections on
the pieces of brass are toward the armature core and the spaces between
the ends of the pieces occupy the position relative to the cores, shown
at A, Fig. 2. Another nut is then placed on the shaft and drawn up tight
against the cylinder. The proper spacing of the various parts on the shaft
of the machine is shown at D, Fig. 1. Another small nut is placed on the
end of the shaft, away from the commutator, so that its outside surface
is 1/2 in. from the surface of the end of the armature core.
[Illustration: Diagram of the Winding on the Armature and Detail of the
Field Laminations (Fig. 2)]
The threads on that part of the shaft extending beyond the last nut on
each end are now filed off, which can be easily done by placing the shaft
between the centers of a lathe and revolving it quite rapidly, the file
being applied to the parts that are to be cut down.
Obtain a small quantity of No. 22 gauge single-cotton-covered copper wire
and wind four layers on each of the three legs, or poles, of the armature
core, insulating the layers from each other and the entire winding from
the core by means of paper and shellac. The three coils are wound in the
same direction about their respective cores and each winding is started
at the center of the armature with 2 or 3 in. of wire extending out toward
the commutator. The outside end of each winding will terminate at the end
of the coil toward the center of the armature, if an even number of layers
is wound on, and is securely fastened by means of two or three turns of
heavy thread. The inside end of one coil is then connected to the outside
end of the next one, and so on. These connections can be easily made, and
at the same time the proper connections made to the commutator, by cutting
the inside end of one coil and the outside end of the next so that they
will reach the lug on the nearest segment of the commutator, with about
1/4 in. to spare, then removing the insulation from each for about 1/8 in.
and soldering them both to the same lug. The arrangement of the winding is
shown at A, Fig. 2. Connect all of the coils and segments in this manner,
and the armature of the motor is complete.
The field or frame of the machine is made from a number of laminations
whose dimensions correspond to those given in B, Fig. 2. As many
laminations are used in the construction of the frame as the number of
pieces in the armature, if iron of the same thickness is used. Four of
the laminations have extensions at their lower corners to correspond
to the parts shown by the dotted lines in B, Fig. 2. Place all of these
laminations in a pile and clamp them rigidly together, then drill the four
holes, indicated by the letters C, D, E and F, with a 3/16-in. drill. Two
of the pieces with the extensions on them are placed in the bottom of the
pile and the other two on top.
Place a 3/16-in. bolt through each of the lower holes and draw up the
nuts on them tight. Procure two pieces of 3/16-in. rod, 1-1/2 in. long,
and thread each end for a distance of 1/2 in. Get 8 nuts for these rods,
about 1/8 in. thick and 5/8 in. across the face, if possible. Both sides
of these nuts are filed down flat. Put the threaded rods through the two
upper holes in the field frame and place a nut on each end and draw them
tight, leaving an equal length of rod protruding from each side.
Obtain two pieces of 1/8-in. brass, 5/8 in. wide, one 4-3/4 in. long and
the other 5-3/4 in. long. Bend these pieces into the forms shown at A,
Fig. 3. Drill a 3/16-in. hole in each end of both pieces so that they may
be mounted upon the ends of the rods protruding from the field frame. The
exact center of the space the armature is to occupy is then marked on each
of these pieces, and a hole is drilled in each, having the same diameter
as the ends of the armature shaft.
[Illustration: Detail of the Armature Supports and the Brushes, and the
Manner of Mounting the Brushes (Fig. 3)]
The extensions on the outside laminations are bent over at right angles
to the main portion of the frame, thus forming a base upon which the motor
may rest. Holes may be drilled in the extensions after they are bent over
to be used in mounting the frame upon a wooden base.
Procure about 1/2 lb. of No. 18 gauge single-cotton-covered copper wire
and wind it on the lower center portion of the frame until the depth of
the winding is about 1/2 in. Be careful to insulate the winding well and,
to insure mechanical protection, place a layer of adhesive tape outside.
About 4 or 5 in. of wire is allowed at each end for making connections. It
is best to have these ends terminate on the commutator side of the frame.
The brushes for the machine are made from some thin sheet copper or brass,
and are shaped and dimensioned approximately as shown at B, Fig. 3. Two
pieces of hard rubber, or fiber, 1/2 in. square and 7/8 in. long, serve
as mountings for the brushes. These pieces of insulation are mounted in
the corners of the armature support, at the commutator end, by means of
two small screws in each. Mount the brushes on these pieces so that their
free ends bear on the commutator exactly opposite each other. One brush
is mounted on the upper end of its support and the other brush on the
lower end of its support. This is shown at C, Fig. 3. Two small binding
posts are mounted at the same time as the brushes, and are electrically
connected to the brushes, thus affording an easy means of making a
connection to the armature. The brushes are so mounted as to bear firmly
upon the commutator.
To operate the motor, connect the armature and field windings in series,
and the combination to a source of electromotive force of several volts.
If it is desired to reverse the direction of rotation, reverse the
connections of either the armature or field windings, but not both. The
motor may be mounted on a neat wooden base and the connections all brought
down to a reversing switch, which may also be mounted on the same base
as the motor. The speed can be varied by changing the impressed voltage,
or by connecting a variable resistance in the armature circuit, such as
a wire rheostat.
A small pulley may be made and attached to the armature shaft so that the
motor may be used in driving various kinds of toys.
Cooler for Milk and Butter
[Illustration]
An earthen jar or crock, with a cover, set in a box containing moist sand
will keep butter and milk in hot weather better than a refrigerator. The
sand must be kept moist at all times.--Edwin J. Bachman, Jr., Fullerton,
Pa.
Rubber Bumper on a Water Faucet
Sometimes a dish is broken by striking it on the faucet. This is easily
remedied by cutting a rubber washer from a rubber-boot heel with a
sharp chisel and a hammer. The washer is pushed into place on the
end of the faucet, and the dishes may strike the rubber without being
broken.--Contributed by Harriette I. Lockwood, Philadelphia, Pa.
Boring a Clean-Edged Hole
[Illustration]
When boring a hole in wood, withdraw the bit as soon as the worm shows,
then start the worm in the hole on the opposite side and finish boring
the hole. It will then have clean edges on both sides of the wood. Often
the bit pushes splinters of wood ahead of it, when passing through, but
by using the method described this is avoided.
Drilling Thin Metal
[Illustration]
In drilling very thin stock the drill, if not properly ground, will tear
the metal and leave a ragged edge. To cut a hole through neatly the drill
should be ground as illustrated. The center A should extend about 1/64 in.
beyond the points B. The point A locates the center and the sharp points
B cut out the disk of metal. Holes have been neatly and quickly made with
this drill grinding in metal measuring .002 in. thickness.--Contributed
by Joseph J. Kolar, Maywood, Ill.
* * * * *
A pencil may be kept from falling out of the pocket
by wrapping a couple of turns of tape around it or by
wrapping it with a small rubber band.
Flexible-Cord Adjuster for an Electrical Flatiron
[Illustration]
When using an electrical flatiron the flexible cord frequently gets under
the iron, causing much trouble for the user, and mussing up the clothing.
The cord can be kept out of the way by fastening a pulley to the ironing
board and attaching a coil spring to the electric cord between the pulley
and the electric-fixture socket. A coil spring that will draw out about
3 ft. should be used.--Contributed by Herbert Blandford, Elmira, N. Y.
A Wood Clothes Peg
[Illustration]
If clothes that are slightly damp are hung on a nail or metal peg, a rust
stain that is almost impossible to remove will be the result. To prevent
this, drive a nail with the head removed into the wall or cleat, and
place a wood peg over it. The peg may be turned up or whittled out with
a pocket knife and the hole bored with a hand drill.--Contributed by Wm.
A. Robinson, Waynesboro, Pa.
To Make Scratch Pads of Old Labels
[Illustration]
Labels and blank paper of uniform size, that would otherwise be cast
aside, can be turned into handy scratch pads by placing them between
blocks of wood, secured by a wood clamp, and applying paste on two edges,
then pressing a strip of paper on the pasted portions. The edges to be
pasted should project a trifle beyond the edges of the blocks.
How to Make an Electric Heater
The electric heater described in this article is very simple to construct,
its operation exceedingly satisfactory, and the necessary material
easily procured at a small cost at most electrical-supply stores. The few
tools needed are usually found about every home, and the heater may be
constructed by any ingenious person.
Procure 6 porcelain tubes, 20 in. long and approximately 13/16 in. in
diameter. On each of these tubes wind 25 ft. of bare No. 26 gauge "Climax"
resistance wire. The various turns should be uniformly distributed along
the tubes and not allowed to come into contact with each other, which
can be prevented by placing a thin, narrow coat of plaster of Paris along
the side of each of the tubes immediately after the winding has been put
on. Several inches of free wire should be allowed at each end, for making
connections, and the first and last turns on each tube should be securely
fastened to the tube by several turns of binding wire. It would be best
not to extend the winding nearer the ends of the tubes than 3/4 in.
Cut from some heavy tin, or other thin sheet metal, two disks, 6 in.
in diameter, and punch six 5/16-in. holes in each of the disks at equal
distances and within 3/4 in. of the outer edge. Punch two 1/8-in. holes
in one of these disks, to be used in mounting a porcelain socket, and
also one 1/2-in. hole through which the wires may be led to the socket,
as shown in Fig. 1. In the other disk punch four 1/8-in. holes, for
mounting two porcelain single-pole snap switches, and two 1/2-in. holes,
for leading the wires through to the switches, as shown in Fig. 2.
[Illustration: Detail of the Two Ends on the Heater Giving Dimensions and
the Location of Parts (Fig. 1, Fig. 2)]
Cut off six lengths of 5/16-in. iron rod, 22 in. long, and thread both
ends of each piece for a length of 1-1/4 in. Fasten the porcelain tubes
between the metal disks, by placing one of the rods through each of the
tubes and allowing the ends to extend through the 5/16-in. holes in the
outer edge of the disks. A nut should be placed on each end of all the
rods and drawn up so that the length of rod protruding at each end is the
same. Obtain two single-pole snap switches and a porcelain socket, and
mount them on the ends by means of some small stove bolts.
The windings on the porcelain tubes should be connected as follows: Let
the windings be designated by the letters A, B, C, D, E, and F, and their
position be that indicated in Figs. 1 and 2. The primes indicate the ends
of the windings at the socket end, and the letters without the primes
indicate the ends of the windings at the switch end of the heater. The
ends A and D should be connected directly together. The ends B and C to
the clips of the right-band snap switch, and E and F, to the clips of
the left-hand snap switch. The ends F, A, and B should be connected to
one terminal of the socket, and C, D, and E to the other terminal of the
socket. Electrical connection is made to the winding by means of a plug
and piece of lamp cord. It is obvious that the windings A and D will be
connected as soon as the plug is screwed into the socket, if the circuit
is closed at all other points, and the windings B and C, and E and F are
controlled by the right and left-hand snap switches, respectively. Make
sure all the connections are properly insulated, and that there is little
chance of a short circuit occurring.
After the socket and snap switches have been connected to the windings,
two more thin disks, the same diameter as the first, may be fitted over
the ends and held in place by two units on the end of each rod, a nut
being placed on each side of the disks. A better way of mounting these
disks would be by small machine screws that enter threaded holes in the
ends of the rods. These last disks are not absolutely necessary, but they
will add some to the appearance of the completed heater. Four small ears,
about 5/8 in. square, should be cut on the outer edge of the outside or
inside disks and bent over at right angles to the main portion, to be used
in mounting the outside case of the heater.
Cut from a sheet of 1/8-in. asbestos a piece just long enough to fit
between the inside disks and wide enough to cover the three lower windings
C, D, and E. The object of this piece of asbestos is to protect the
surface upon which the heater will stand from excessive heat, since it is
to rest in a horizontal position.
Obtain a piece of perforated, thin sheet metal, 19-1/2 in. wide and long
enough to reach from one outside disk to the other. Bend this into a
cylinder and fasten it to the lugs on the disks by means of small screws
or bolts.
[Illustration: (Fig. 3)]
The legs may be made of 1/8-in. strap iron, 5/8 in. wide, bent into the
form shown in Fig. 3. These pieces may be attached to the perforated
cylinder, before it is mounted on the heater proper, by means of several
small bolts. The piece of asbestos should be wired to the cylinder after
the heater is all assembled, so that it will always remain in the lower
part of the cylinder and serve the purpose for which it is intended.
The heater, as described above, is constructed for a 110-volt circuit,
which is the voltage commonly used in electric lighting. The total
consumption of the heater will be approximately 600 watts, each part
consuming about 1/3 of the total, or 200 watts. If it is desired to
wind the heater for a 220-volt circuit, 25 ft. of No. 29 gauge "Climax"
resistance wire should be used on each tube.
A Molding-Sawing Block Used on a Bench
Having occasion to saw some short pieces of molding, I experienced
considerable trouble in holding them without a vise until I made a block,
as shown in the sketch. This answered the purpose as well as a vise. The
block is not fastened in any manner, but is simply pushed against the edge
of the bench or table and held with the hand. It should be about 9 in.
wide and 1 ft. long, with strips 2 in. thick at each edge.--Contributed
by W. F. Brodnax, Jr., Bethlehem, Pa.
[Illustration: A Block for Holding Molding, or Strips of Wood, While
Sawing Small Pieces from Them]
Pipe Caps Used as Castings for Engine Pistons
Desiring to make a small piston for a model engine and not caring to make
a pattern and send it away to have a casting made, I thought of using
ordinary pipe caps, these being both inexpensive and of a quality adapted
to machining.
The cylinder bore was 1-1/2 in. in diameter, so I secured a standard pipe
cap for 1-1/4-in. pipe which gave an outside diameter of about 1-5/8 in.
The cap, not having sufficient depth for holding in a chuck, was screwed
on a short piece of pipe and then trued in the lathe chuck. The outside
surface was turned to a diameter of 1-1/2 in., then removed from the
pipe, reversed and chucked again, and the threads bored out to reduce
the walls to 1/8 in. This made an excellent piston for a single-acting
engine.--Contributed by Harry F. Lowe, Washington, D. C.
An Electric Horn
A simple electric horn for use on a bicycle, automobile, or for other
purposes, can be constructed as shown in Fig. 1. The size will of course
depend somewhat on the use for which it is intended, but one with the
diaphragm 1-3/4 in. in diameter and the horn 5 in. long and 4 in. in
diameter, at the large end, will be sufficient for most purposes. This
will make the instrument 7-1/2 or 8 in. in over-all length.
[Illustration: An Electric Horn Operated in a Manner Similar to an
Electric Bell on a Battery Circuit (Fig. 1)]
The horn proper, A, Fig. 1, is constructed first. This can be formed
from sheet brass. To lay out the metal to the desired size draw a cross
section, as ABCD, Fig. 2, then project the lines AC and BD until they
meet at E. Strike two arcs of circles on the brass sheet, using EC as
radius for the inner one and EA for the outer. Measure off FG and HJ equal
to 3-1/4 times DC and AB, respectively, and cut out FGJH. Roll and lap
1/4 in. at the edges and solder the joint neatly.
[Illustration: (Fig. 2)]
After smoothing the edges on the ends, solder a very thin disk of
ferrotype metal, B, Fig. 1, to the small end of the horn. This is used
for the diaphragm. Cut out a ring, C, from 1/4-in. hard fiber and bevel it
on the inside edge to fit the horn. Also make a disk of fiber, D, having
the same outside diameter as the ring C. These parts form the ends for a
brass cylinder E, which is made in two parts or halves joined on the lines
shown in Fig. 3. Fasten one of the halves, F, Fig. 3, to the fiber ring C
and disk D, Fig. 1, with small screws, the other half to be put in place
after the instrument is completed and adjusted.
[Illustration: (Fig. 3)]
A small support, G, is cut from fiber and fastened in as shown. A pair of
magnets of about 50 ohms are mounted on this support. The parts from an
old bell or buzzer may be used, which consist of a soft-iron armature,
H, Fig. 1, having a strap of spring brass, J, attached by soldering and
pivoted at K, with an adjusting screw, L, to set the tension. Another
U-shaped spring-brass strip, M, constitutes the current breaker, which
has an adjusting screw, N. The points of contact on the current breaker
should be tipped with platinum. A piece of brass wire, O, is soldered
to the diaphragm disk B and the soft-iron armature H, to connect them
solidly. The tone of the horn can be adjusted with the screws L and N. The
faster the armature vibrates, the higher the tone, and vice versa. The
connections are the same as for an electric bell.--Contributed by James
P. Lewis, Golden, Colo.
Combination Meat Saw and Knife
A very handy combination knife and meat saw can be made of an old
discarded saw blade. The blade is cut on a line parallel with the toothed
edge, allowing enough material to make a good-sized blade, then the
straight part is ground to a knife edge and a wood handle attached at one
end. The handle is made in halves, placed one on each side of the blade,
and riveted together, then the projecting metal is ground off to the shape
of the handle.--Contributed by A. C. Westby, Porter, Minn.
[Illustration: The Blade of the Knife is Cut from the Toothed Side of a
Discarded Saw Blade]
Clamp Used as a Vise
A carpenter's wood clamp fastened to the edge of a bench, as shown in the
sketch, makes a good substitute for a vise for many kinds of light work.
If the clamp is located over or in front of the bench post, holes must be
bored in the latter to admit the ends of the clamp screws. A hole is bored
through the shoulder screw and a handle attached as shown.--Contributed
by H. W. J. Langletz, Harrisburg, Pa.
[Illustration: The Clamp Attached to a Bench Top will Serve the Purpose
of a Vise in Many Instances]
Wire Expansion Meter
When there is a current of electricity in an electrical conductor a
certain amount of heat is generated due to the opposition or resistance of
the conductor to the free passage of the electricity through it. The heat
thus generated causes a change in the temperature of the conductor and
as a result there will be a change in its length, it contracting with a
decrease in temperature and expanding with an increase in temperature. The
temperature of the conductor will change when the current in it changes,
and hence its length will change, and it will reach a constant temperature
or a constant length when the current in it is constant in value and the
rate at which it is giving off heat is exactly equal to the rate at which
heat is being generated in it.
The fact that there is an actual change in the length of the conductor due
to a change in current in it constitutes the fundamental principle of the
following simple instrument.
[Illustration: Meter for Measuring the Expansion of Metal Wires Which are
Heated by Electricity]
The parts needed in its construction are as follows: An old safety-razor
blade; one 8-in. hatpin; two medium-size nails; a short piece of
German-silver wire; a small piece of sealing wax; a 1/2-in. board for
the base, approximately 3-1/2 in. by 10 in., and a small piece of thin
sheet brass. Remove the head from the hatpin and fasten the blunt end
in the center of the safety-razor blade A with a piece of sealing wax so
that the pin B is perpendicular to the blade as shown. Now drive the two
nails into the board C, so that they are about 1/4 in. from the edges and
1-1/2 in. from the end. Fasten the piece of German-silver wire D to these
nails as shown. The size of this wire will depend upon the value of the
current to be measured. Make a small hook, E, from a short piece of rather
stiff wire and fasten it to the hatpin about 1 in. from the razor blade.
The length of this hook should be such that the pointed end of the hatpin
will be at the top of the scale F when there is no current in the wire,
D. The scale F is made by bending the piece of sheet brass so as to form
a right angle and fastening it to the base. A piece of thin cardboard can
be mounted upon the surface of the vertical portion of the piece of brass
and a suitable scale inked upon it. The instrument is now complete with
the exception of two binding posts, not shown in the sketch, that may be
mounted at convenient points on the base and connected to the ends of the
German-silver wire, thus serving as terminals for the instrument.
The completed instrument can be calibrated by connecting it in series with
another instrument whose calibration is known and marking the position of
the pointer on the scale for different values of current.
How to Make a Fire and Burglar Alarm
A very serviceable fire and burglar alarm may be installed by anyone who
can work with carpenters' tools and who has an elementary knowledge of
electricity. Fire and burglar alarms are divided into two general types,
called "open circuit" and "closed circuit," respectively.
In the open-circuit type of alarm all the windows, doors, and places to be
protected are equipped with electrical alarm springs which are in circuit
with an ordinary vibrating bell and battery, and these alarm springs are
all normally open. When a window or door is disturbed or moved more than
a predetermined amount, the bell circuit is closed and the alarm sounded.
The arrangement of such an alarm is shown in Fig. 1. A switch, A, is
placed in circuit so that the alarm may be disconnected during the day and
the opening and closing of doors and windows will not operate the bell.
It is best not to place a switch in the fire-alarm circuit as this circuit
should be in an operating condition at all times.
[Illustration: Connections and Wiring Diagram Showing an Open-Circuit Fire
and Burglar Alarm (Fig. 1)]
The alarm switch controlled by the window consists of a narrow metal
plate, B, and a spring, C, mounted in a recess cut in the side of the
window frame. The spring C is bent into such a form that its upper end
is forced into contact with the plate B, when the window is raised past
the outwardly projecting part of the spring C, and the bell circuit is
thus closed. The position of the alarm switch can be adjusted so that
the window may be opened a sufficient distance to permit the necessary
ventilation but not allow a burglar to enter.
The alarm switch controlled by the door is arranged in a different manner.
In this case the free end of the spring D is held away from contact with
the spring E by the edge of the door, which forces the spring D back into
the recess cut in the door jamb. When the door is opened the spring E
is permitted to move out and come into contact with the spring or plate
E, and the alarm circuit is thus closed. The form of the spring D can be
so adjusted that the door may be opened some distance, but not enough to
allow a person to enter, before the alarm is sounded.
An alarm switch, identical with that just described for the door, should
be mounted in the upper part of the window frame to take care of the upper
sash. This alarm switch may be located low enough to permit the window to
be lowered for the purpose of ventilation without sounding the alarm.
The wires for these various alarm switches should be run as near
completely concealed as possible to prevent them being tampered with
by curious parties, who may unintentionally break one of the conductors
and thus make some part of the system inoperative. It might be best to
test the system occasionally, to make sure all switches are in operating
condition.
The fire-alarm switch consists of two springs that are held from contact
with each other by means of a thin cord. This switch is placed in the
location to be protected, or wherever a fire is most likely to break
out, such as over the furnace, in the coal bin, etc. When the cord is
destroyed the springs make contact and the alarm is sounded. A metal
having a very low melting temperature may be used instead of the cord, and
the alarm will be sounded when the temperature exceeds a certain amount
and the actual occurrence of a fire thus prevented. In some cases, the
fire-alarm switch may be completely destroyed and the alarm circuit will
then be opened and the bell will cease ringing. To prevent this trouble
a small electric drop may be placed in the circuit, the arrangement being
similar to that shown in Fig. 2. When the shutter of the drop falls, due
to the closing of the alarm circuit, there is a second circuit closed,
and this second circuit remains closed until the shutter is restored to
its vertical or normal position, or the switch, A, is thrown to the open
point. The addition of the drop in the burglar-alarm circuit may prove
to be an advantage, as a burglar cannot stop the alarm, after he has
once closed any of the alarm switches and operated the drop, by simply
restoring the window or door to its original position.
[Illustration: Circuit Equipped with Drop to Ring the Bell in Case the
Switch is Destroyed (Fig. 2)]
In the closed-circuit type, the alarm switches are all normally closed and
the alarm is sounded by opening the circuit at some point. The arrangement
of such an alarm is shown in Fig. 3. The alarm switches are all connected
in series in this case and in circuit with a closed-circuit battery and
relay or drop. The drop or relay controls a local circuit composed of an
open-circuit battery and an ordinary vibrating bell.
[Illustration: Wiring Diagram Showing Connections for a Closed-Circuit
Burglar and Fire Alarm (Fig. 3)]