suspended in the water. The wire should be about 25 ft. long, and,
in transporting the outfit, or when only partly used, is coiled. The
chamber should be completed for picture-taking operations by giving it
a coat of dull, black waterproof paint, both inside and outside. This
will prevent rusting and also serves to make the object inconspicuous
when in the water. It is important that the interior be painted in
this manner, because reflections of light within the chamber may
cause difficulty in obtaining satisfactory results. When the paint is
thoroughly dry, the device may be tested for leakage and assembled
ready for a test before making an actual trial in the water. The camera
is fitted into the chamber so that it centers on the center of the
plate-glass window, and is clamped into place. If the electrical device
operates satisfactorily the plate may be inserted, the plate-holder
slide withdrawn, the back cap replaced securely, and the outfit lowered
into the water. It should be watched carefully until it reaches
the proper depth, for, if it is permitted to touch the bottom, the
sediment stirred up must be given time to settle before an exposure
is made. The forward end of the chamber should be marked on its
upper edge with a streak of white paint, to aid in identifying it at
considerable depth in the water. This is important, since the operator
must shift the chamber carefully until the window faces the objects to
be photographed. When the chamber is in position, the contact key is
pressed and the exposure is made.
The time of exposure for under-water photography depends on the
clearness of the water, the depth at which the pictures are to be
taken, and the light conditions on the surface. A bright day is, of
course, desirable for this class of photography. A safe approximation
on a sunny day, in clear water, and with the chamber lowered to a depth
of 20 ft., is ¹⁄₂₅ sec. at the F 8 stop. The fastest plates or films
obtainable should be used for this work, making possible a fairly rapid
shutter speed. This tends to overcome the movement of the subject and
possible movement of the camera.
The camera should be focused while in the chamber in order that the
plate glass may not disturb the focus. The glass usually changes the
focal length of the lens slightly, hence this precaution must be taken.
The camera should be focused in the chamber for a distance of 10 ft.,
as this is the average at which under-water photographs will be taken
ordinarily.
When attempting under-water photography in cloudy waters, or at a
considerable depth, the necessary illumination may be provided by
a charge of flash-light powder. For this purpose another submarine
chamber, similar to that used for the camera, should be provided,
with a plate glass, ¹⁄₂ in. thick, and a valve fitted into the top of
the chamber, and opening outward, so that the gas may escape. Fifteen
grains of powder will suffice, and this should be set off by a small
electrical fuse connected to the current supply.
[Illustration: FIG. 1
FIG. 2
Photographing Subjects under Water Is a Fascinating Diversion, and Each
Exposure Has an Element of Mystery in the Uncertainty of the Result.
The Photograph Reproduced in the Oval was Taken with the Outfit Shown.
The Construction of the Chamber is Shown at the Middle. Fig. 1 Shows a
Sectional Interior View, and Fig. 2, a Detail of the Electrical Shutter
Release]
Every pond, lake, and river abounds in interesting and instructive
subjects for submarine photography. Along the coast of Florida, and
at many points along the Pacific coast, are waters of such clearness
that pictures may be taken at a depth of nearly a hundred feet, without
the use of artificial illumination. These localities abound in objects
under water of great interest, such as shipwrecks. The fascinating
art of taking pictures under water does not make it necessary for one
to go to these places, for subjects are easily available. Whenever
the submarine chamber is raised from the water there is an element of
mystery involved, regarding what may be recorded on the plate or film,
and this is an attractive feature of the diversion.
The Magic of Numbers
BY JAMES L. LANYON
That there are a great many magic squares; that the numbers in these
squares are arranged according to a definite system; that squares
with very remarkable properties are easily constructed, are facts not
generally known.
Consider the magic square A of 16 numbers. Add up any four numbers
straight across, up and down, or diagonally--10 ways in all--and the
sum in each case will be 34. But that is not all: Take the four numbers
in any one quarter of the square, as for example, 15, 10, 4, and 5,
and the sum will be 34; or take the four central numbers, or the four
corner numbers, and the result will be the same. But even this does
not exhaust the magic of the square. Add any four numbers arranged
symmetrically around the center, as 3, 10, 8, and 13, or 10, 4, 7, and
13, and the result will also be 34. In fact, it is really not necessary
to have them arranged symmetrically, because it will be found that four
numbers arranged as are 6, 10, 11, and 7, or 1, 4, 16, and 13 will
produce the same magic number of 34.
There are two other combinations of the 16 numbers that will give the
same result. They are shown at B and C. In fact the second one, B, not
only exhibits some of the former combinations, but also includes such
sets of four as 14, 5, 3, and 12, or 15, 8, 2, and 9, which places to
the credit of this square numerous combinations. Such special features
as this simply add another element of mystery and interest. Thus, while
the square B has these two combinations exclusively to its credit, the
first, A, and the third, C, have such special arrangements as 5, 16, 1,
and 12, or 15, 6, 11, and 2. Also 10, 3, 5, and 16, or 4, 5, 14, and
11, making the total number of such combinations for the first square
34.
Magic squares of 25 numbers also have remarkable properties. Examine
the square D and note the many possible combinations graphically set
forth in the small diagrams. Not only do any five numbers in a row
or along a diagonal make 65, but almost any four arranged around the
center, with the center number 13 added, will give the same result.
This square is a good example by which to illustrate one of the
methods of construction of these interesting devices. Thus, place
1 in the middle square of the top row, and then write the numbers
down consecutively, always working in the direction of the arrows as
indicated. When any number falls outside, as number 2 does at the
start, drop down to the extreme square in the next row and insert the
number there, as was done in this case. It will be observed that 4
falls outside, and so it is moved to the proper square as suggested,
which will be at the extreme left of the next row above. Continuing,
it is found that at 6 it is necessary to drop down one square and
continue in the direction of the arrows. At 9 it is necessary to drop
down to the proper extreme square as shown. The next number, 10, must
again be provided for at the square on the left of the next higher row.
The square ahead being already filled, 11 is placed below; after this
there is “clear sailing” for a time. In this manner magic squares with
seven or nine numbers to the side may be made easily. When puzzles and
catch problems are under discussion, it is always mystifying to take
one’s pencil and quickly make out a magic square according to this
easily remembered method. The small diagrams at D suggest some of the
combinations.
Another method of constructing a square of 25 numbers diagonally
is shown at E. Place the outside numbers in the open spaces at the
opposite side of the square, maintaining the same triangular relation,
which results in the arrangement shown at F. While this combination
is entirely different from the previous one, it exhibits the same
mysterious properties.
[Illustration:
+---+---+---+---+
| 15| 10| 3 | 6 |
+---+---+---+---+
| 4 | 5 | 16| 9 |
+---+---+---+---+
| 14| 11| 2 | 7 |
+---+---+---+---+
| 1 | 8 | 13| 12|
+---+---+---+---+
A
+---+---+---+---+
| 1 | 15| 14| 4 |
+---+---+---+---+
| 12| 6 | 7 | 9 |
+---+---+---+---+
| 8 | 10| 11| 5 |
+---+---+---+---+
| 13| 3 | 2 | 16|
+---+---+---+---+
B
+---+---+---+---+
| 9 | 7 | 14| 4 |
+---+---+---+---+
| 6 | 12| 1 | 15|
+---+---+---+---+
| 3 | 13| 8 | 10|
+---+---+---+---+
| 16| 2 | 11| 5 |
+---+---+---+---+
C
+---+---+---+---+---+
| 17| 24| 1 | 8 | 15|
+---+---+---+---+---+
| 23| 5 | 7 | 14| 16|
+---+---+---+---+---+
| 4 | 6 | 13| 20| 22|
+---+---+---+---+---+
| 10| 12| 19| 21| 3 |
+---+---+---+---+---+
| 11| 18| 25| 2 | 9 |
+---+---+---+---+---+
4 COMBINATIONS
6 COMBINATIONS
D
+---+
| 1 |
+---+---+---+
| 6 | | 2 |
+===+===+===+===+===+
‖ 11| | 7 | | 3 ‖
+---+---+---+---+---+---+---+
| 16‖ | 12| | 8 | ‖ 4 |
+---+---+---+---+---+---+---+---+---+
| 21| ‖ 17| | 13| | 9 ‖ | 5 |
+---+---+---+---+---+---+---+---+---+
| 22‖ | 18| | 14| ‖ 10|
+---+---+---+---+---+---+---+
‖ 23| | 19| | 15‖
+===+===+===+===+===+
| 24| | 20|
+---+---+---+
| 25|
+---+
E
+---+---+---+---+---+
| 11| 24| 7 | 20| 3 |
+---+---+---+---+---+
| 4 | 12| 25| 8 | 16|
+---+---+---+---+---+
| 17| 5 | 13| 21| 9 |
+---+---+---+---+---+
| 10| 18| 1 | 14| 22|
+---+---+---+---+---+
| 23| 6 | 19| 2 | 15|
+---+---+---+---+---+
F
+===+===+===+===+===+===+===+===+===+===+===+===+===+===+===+
‖ 4 | 25| 18| 11| 7 ‖ 11| 24| 2 | 20| 8 ‖ 17| 6 | 5 | 23| 14‖
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
‖ 14| 20| 2 | 17| 12‖ 9 | 12| 25| 3 | 16‖ 3 | 24| 12| 16| 10‖
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
‖ 5 | 10| 13| 16| 21‖ 17| 10| 13| 21| 4 ‖ 11| 20| 8 | 4 | 22‖
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
‖ 23| 9 | 24| 6 | 3 ‖ 5 | 18| 6 | 14| 22‖ 9 | 2 | 21| 15| 18‖
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
‖ 19| 1 | 8 | 15| 22‖ 23| 1 | 19| 7 | 15‖ 25| 13| 19| 7 | 1 ‖
+===+===+===+===+===+===+===+===+===+===+===+===+===+===+===+
G
+---+---+---+---+---+---+---+
| 30| 39| 48| 1 | 10| 19| 28|
+---+---+---+---+---+---+---+
| 38| 47| 7 | 9 | 18| 27| 29|
+---+---+---+---+---+---+---+
| 46| 6 | 8 | 17| 26| 35| 37|
+---+---+---+---+---+---+---+
| 5 | 14| 16| 25| 34| 36| 45|
+---+---+---+---+---+---+---+
| 13| 15| 24| 33| 42| 44| 4 |
+---+---+---+---+---+---+---+
| 21| 23| 32| 41| 43| 3 | 12|
+---+---+---+---+---+---+---+
| 22| 31| 40| 49| 2 | 11| 20|
+---+---+---+---+---+---+---+
H
The Magic Squares Shown Afford Much Interest to the Experimenter in
Such Devices: The Mastery of the Principle Underlying Some of Them will
Enable One to Mystify and Interest Onlookers, with Little Chance of the
Simple Method being Discovered]
Although they do not contain quite so many combinations, the three
magic squares shown at G all add up to this same magic number of
65, straight across, diagonally, and many other ways. A square with
seven numbers to the side, worked out according to the first method
described, is illustrated at H. The magic number here is 175. Since the
general principle is similar to that involved in the squares described
in detail, the working out of the numerous combinations of the squares
shown at G and H will be left to the interested experimenter.
Muffling the Ticking of a Watch or Clock
When a watch is used on a table in the sick room, the ticking may be
eliminated by placing an ordinary tumbler over the watch. The face may
be seen readily. A large glass vessel, or transparent jar, may be used
in the same way to cover a small clock.--L. E. Turner, Jamaica, N. Y.
* * * * *
¶To letter on prepared cloth, use colors ground in japan and thin the
mixture with gasoline to the consistency of cream.
A Simple Cipher Code
Adapted for Use in Private Correspondence
BY CAPT. W. H. WALDRON, U. S. ARMY
Have you ever needed a secret code in which to couch the contents of
a message intended for the eyes of one person alone? If you have, you
will remember the difficulties that were experienced in making up the
code and enciphering your letter. Here is a cipher code that may be
mastered in a few minutes; one that is most difficult to decipher by
any person other than those having the key words, and that is very
simple when once understood.
[Illustration:
+---+---+---+---+---+
| G | R | A | N | T |
+---+---+---+---+---+
| | | | | |
+---+---+---+---+---+
| F | IJ| E | L | D |
+---+---+---+---+---+
| | | | | |
+---+---+---+---+---+
| | | | | |
+---+---+---+---+---+
FIG. 1
+---+---+---+---+---+
| G | R | A | N | T |
+---+---+---+---+---+
| B | C | H | K | M |
+---+---+---+---+---+
| F | IJ| E | L | D |
+---+---+---+---+---+
| O | P | Q | S | U |
+---+---+---+---+---+
| V | W | X | Y | Z |
+---+---+---+---+---+
FIG. 2
+---+---+---+---+---+
| C | H | A | IJ| R |
+---+---+---+---+---+
| B | D | E | F | G |
+---+---+---+---+---+
| K | L | M | Q | S |
+---+---+---+---+---+
| O | P | T | U | N |
+---+---+---+---+---+
| V | W | X | Y | Z |
+---+---+---+---+---+
FIG. 3
The Cipher Code Illustrated in These Diagrams may be Adapted for Wide
Uses by the Substitution of Appropriate Key Words for Those Shown]
It is commonly known as the “Play Fair” code and is in use in some
of the foreign military services. It is a substitutive cipher which
operates with one or more key words, two letters in the code being
substituted for each two letters in the text of the message. In
preparing the cipher code by this method the key words are selected by
the correspondents and their location in the cipher square mutually
agreed upon. A large square divided into 25 smaller squares is drawn,
as shown in Fig. 1, and the letters of the key words entered into their
proper spaces, the remaining spaces being filled by other letters of
the alphabet. The key words must not contain duplicate letters. The
letters I and J are considered as one and entered in the same space,
the letter I being invariably used in enciphering.
Suppose that the two words “grant” and “field” have been selected for
the key, the same to be entered respectively in the spaces on the
first and third horizontal lines of the square. Then the basis of the
construction would be as indicated in Fig. 1. Now fill in the remaining
fifteen spaces of the square with other letters of the alphabet,
beginning at the blank space at the left of the second line, entering
the letters in rotation and not using any letter of the key words. The
completed cipher would then appear as shown in Fig. 2.
The text of the message to be sent is then divided into groups of two
letters each and the equivalent substituted for each pair. Where two
like letters fall in the same pair the letter X is inserted between
them and when the message is deciphered this additional letter is
disregarded. If one letter is left over after the last pair, simply add
an X to it and make a pair.
Suppose it is desired to send this message in the cipher: “Will you
meet me as agreed.” Having three pairs of the same letter, it will be
necessary to break them up by placing the letter X between them. The
message will then be paired off as follows:
WI LX LY OU ME XE TM EA SA GR EX ED
The message may now be enciphered, after considering three simple rules
for guidance: Every pair of letters in the square must be either in the
same vertical line; in the same horizontal line; or at the diagonally
opposite corners of a rectangle formed by the smaller squares within
the large square.
In the first case, R and P are in the same vertical line (the second),
and the next letter below, in each case, is substituted for R and P,
which are C and W. If the pair consists of K and Y (fourth vertical),
substitute L for K and go to the first horizontal line (fourth
vertical) for Y, substituting N for Y. In the second case B and H are
in the same horizontal line (the second), and thus substitute the next
letters to the right, which are C and K. If the pair consists of P
and U (fourth horizontal), substitute Q for P and then go back to the
first vertical line (fourth horizontal) and substitute O for U. In the
third case, R and S are at the opposite corners of a rectangle. Each
letter of the pair is substituted by the letter in the other corner
of the rectangle on the same horizontal line with it. Then R would
be represented by N, and S would be represented by P. To illustrate
further, NE would be represented by AL; BZ would be represented by MV;
TP by RU.
The message may now be enciphered, applying the rules:
WI LX LY OU ME XE TM EA SA GR EX ED
RP EY SN PO HD AQ MD QH QN RA QA LF
In sending this message, to make it more difficult for the inquisitive
cipher expert, divide the substituted letters into words of five each
and give him the added task of determining whether the cipher used is
the transposition or the substitution method. The message ready to hand
to the telegrapher would read:
RPEYS NPOHD AQMDQ HQNRA QALFX
In deciphering a message the method is reversed. Take the message
as received, divide the letters into pairs, and disregard the final
X, which was put in to make a five-letter word. Then apply the key
reversed. Practice it on the above message to get the system with
respect to letters occurring at the end of the lines. Where the letters
of a pair are in the same vertical line, substitute for each the
letter above; where they are in the same horizontal line, substitute
the letter to the left; where they are in the corners of a rectangle,
substitute the letters at the opposite corners on the same horizontal
line. To test the understanding of the system, the message given in
Fig. 3, with the key words “chair” in the first horizontal line and
“optun” in the fourth line, may be deciphered. The message to be
deciphered is as follows:
FQVUO IRTEF HRWDG APARQ TMMZM RBFVU
PICXM TRMXM AGEPA DONFC BAXAX.
Cheese Grater and Ash Tray Made from a Tin Can
[Illustration: Necessity Resulted in the Making of a Cheese Grater and
Ash Tray from a Tin Can]
Being in need of a cheese grater and finding it inconvenient to go many
miles to town, I constructed a satisfactory makeshift. I took a heavily
tinned can and cut it in two, as shown in the sketch. By punching
holes through it from the inside a practical grater resulted. From the
remaining half of the can I made an ash tray, as shown at the right of
the sketch. The semicircular ends were bent over to form a rest, and by
cutting portions at the sides and bending them in, a convenient rest
for a pipe or cigar was afforded.--Gus Hansen, Peachland, B. C., Canada.
An Improvised Typewriter Desk
[Illustration: Remove the Drawer and Replace It Inverted, to Provide a
Convenient Rest for the Typewriter]
Travelers and others who carry typewriters on their journeys
frequently find it inconvenient to use the tables provided because
they are usually too high for typewriters. A method of overcoming this
difficulty is to withdraw the drawer from the table and invert it in
the slide as shown. The typewriter may then be placed upon the bottom
of the drawer and will be considerably lower than if placed upon the
table top.
An Inexpensive Imitation Fire
[Illustration]
Window decorations may frequently be made attractive by the use of
an imitation fire in a stove or a fireplace, when an indoor setting
is on display. To produce such an effect, put an electric fan below
the place at which the imitation fire is to be arranged and run an
electric-light cord, with a red globe attached to it, to the center of
the “flame.” Cut a number of strips of Indian red tissue paper and fix
the lower ends of these to form a circular mass above the globe. When
the light is turned on permit the fan to direct a stream of air against
the tissue-paper ribbons, forcing them upward to appear like tongues
of flame. The sketch shows this method applied to a heater. The fan is
placed in the ash box and the electric light is conducted through the
grate.
Jardinière Made of Metal-Lamp Body
[Illustration]
Some of the metal bodies of old lamps, and they are usually brass, are
of such ample size and so neatly embossed that they can be readily used
as jardinières instead of being handed to the junk man. It is only
necessary to remove the lamp part, and set the plant pot into the bowl
of the stand, as shown in the sketch.--H. N. Wolfe, Chicago, Ill.
Replacing a Broken Coffeepot Knob
A knob was broken from the lid of a coffeepot, which was valued by
reason of its associations. Attempts to fasten the broken portions
together were unsatisfactory, and the rough surface, where the
earthenware was broken, was ground smooth and fitted with a carefully
shaped wooden knob. A hole was drilled through the center of the lid
with an old file and the wooden knob bolted into place. When stained
appropriately, the repair was quite satisfactory.
Homemade Magnesium Printer
[Illustration: Length of Magnesium Ribbon Burned Determines the Time of
Exposure]
A convenient homemade printing device consists of a smooth board, A,
2 ft. long and 1 ft. wide, and an upright, B, which is 1 ft. square.
Bore a hole in the center of the upright for the small tin holder E,
to carry the magnesium ribbon, made by folding a piece of tin to fit
it. Small pieces of wood, CC, are nailed across the board to hold the
ground glass D and the printing frame G. The ground glass is 10 in.
from the upright, and the printing frame is 10 in. from the ground
glass. The latter is 1 ft. square and is used to diffuse the light
from the magnesium ribbon F, which may be purchased from any dealer in
photographic supplies. The length of exposure varies according to the
length of ribbon which is permitted to burn. This should be tested out
carefully before making exposures.--Gustave Straub, Albany, N. Y.
* * * * *
¶In sandpapering a varnished surface between coats, especial care
should be taken to avoid rubbing through at sharp edges.
[Illustration]
Garden Plow Made of Pick-Up Material
BY T. T. STURGEON
The labor of spading a garden of even moderate size is sufficient to
warrant the person who undertakes the job in making a hand plow like
that shown in the illustration, for it will serve many years, with
reasonable care. I made one worth about $5 at an outlay of 25 cents,
gathering the necessary wood and metal from among old machine parts and
pick-up material.
An old wheelbarrow provided the 16-in. wheel. The handles were made
from a ⁷⁄₈ by 4-in. strip of spruce, 5 ft. long. They were marked on
the strip so that one of the curved grips was at each end, on opposite
edges. The curved parts of the grips were cut with a keyhole saw, and
when a kerf long enough to admit a large ripsaw was cut, the board was
ripped into the two handles. They were smoothed and the grips trimmed
with a sharp knife. A section of broomstick was cut for the upper
brace. The lower one is made of a strip of iron, ¹⁄₄ by 1¹⁄₄ by 12 in.,
drilled for ¹⁄₄-in. bolts, and bent at right angles, 1¹⁄₂ in. from each
end. Drill a ¹⁄₄-in. hole at the middle, to engage a bolt on which the
vertical strip is supported, and adjusted to the operator, as shown in
Fig. 1.
[Illustration: FIG. 1
FIG. 4
FIG. 2
FIG. 5
FIG. 3
This Hand Garden Plow was Made of Old Material, a Shovel being Used for
the Making of the Moldboard]
Cut a strip, ¹⁄₄ by 1¹⁄₄ by 18 in., for the vertical support, shown in
Fig. 5. Drill four ¹⁄₄-in. adjusting holes, 1 in. apart, at the upper
end, and three ¹⁄₄-in. holes at the lower end for fastening the strip
to the moldboard, as shown in Fig. 3. Drill a ⁵⁄₁₆-in. hole at the
7¹⁄₂-in. mark, for bolting the strip to the braces, the other ends of
which are fitted on the ³⁄₈ by 10-in. bolt used as an axle. Cut the two
braces 14 in. long, of ¹⁄₄ by 1¹⁄₄-in. strips, and drill a ³⁄₈-in. hole
in the forward end of each, to fit the axle, and a ⁵⁄₁₆-in. hole in
the opposite ends, 1 in. from the ends in each case. Cut a strip, ¹⁄₈
by ³⁄₄ by 12 in., for the landside, as shown in Fig. 2, bent under the
moldboard, and bolted to it. The proper angle can best be bent after
the moldboard is made and fitted.
The method of marking the shape of the moldboard on the blade of an
old shovel is shown in Fig. 4. Make a pattern of cardboard, marking
it into 1-in. squares. Draw the shape of the moldboard by tracing the
outline through the corresponding squares, using the diagram as a
guide. Mark the position of the bolt holes, for fastening it to the
vertical support, indicated by the dash lines at the right. Cut out
the pattern and trace around it on the shovel, using the thickest part
for the point of the share. Cut out the outline, smooth the edges, and
point up the cutting edge. Drill holes for fastening the moldboard to
the vertical strap with ¹⁄₄-in. bolts, and for the fastenings to the
landside, with ³⁄₁₆-in. bolts.
Curve the moldboard into shape and fit it to the various supports so
that it sits properly, as shown in Fig. 1, seen from the furrow side,
in Fig. 2, from the rear, and in Fig. 3, from the land side. Bend the
12-in. strip into shape, as shown in Fig. 3, and bolt it into place, to
form the landside. Assemble the parts, being careful that the wheel and
landside are set in line, as shown in Fig. 2, and that the rear edge of
the latter is raised slightly, as in Fig. 3. The plow should be given a
coat of paint, and the cutting parts made smooth, and oiled.
An Interesting Water Telescope
[Illustration]
A water telescope is easy to make and will afford much pleasure in
exploring plant or animal life in comparatively shallow water. The
device is made by fitting a heavy glass disk into the end of a round
metal tube, about 2 in. in diameter. The glass is fitted between two
rings of metal, preferably with a small flange set against the glass.
A waterproof cement is used to fix the glass between the rings. To use
the “telescope,” rest it on the side of a boat or other convenient
place at the water, and set the lower end, containing the glass, under
the water. Remarkably clear views may be had in this way.--S. Leonard
Bastin, Bournemouth, England.
Writing on a Moving Train
Writing legibly on a fast-moving train is difficult to a person
unaccustomed to it. The railroad conductor knows the trick of it
and manages to get along quite satisfactorily. He prefers to write
in a standing position and holds his right elbow firmly against his
side. The reason for this is that in a sitting posture there is too
much lateral movement in the trunk of the body, while in a standing
position this is more easily controlled. When the arm swings freely,
as in ordinary writing, several joints of the body are affected in the
process, each of which is capable of its own motion. Holding the elbow
against one’s ribs “breaks” these motion tendencies, except that of the
wrist, which movement is necessary in writing, and thus the pencil, or
pen, is more easily controlled.
The same principles modified apply in using a typewriter on a moving
train. Many traveling men, news correspondents, and others, carry
portable typewriters and do much of their writing while traveling on
trains, not to mention the various railroad and government men who
travel in office cars and necessarily must get out their correspondence
en route. It is extremely difficult to execute neat typewriting
on a moving train with free-arm movement, even though the central
portion of the car where the vibration and swing is less severe, is
selected. As I am employed in such capacity, I had to evolve some
plan to expedite the work. I am able to do typewriting quite rapidly
by resting the palm of the hands, near the wrists, against the front
edge of the typewriter frame surrounding the keyboard, and using the
swing of the fingers instead of that of the whole arm, as in ordinary
typewriting.--Victor Labadie. Dallas, Tex.
A Revolving Window Display
[Illustration]
A jeweler attracted passers-by and not a few customers by placing a
revolving display in his window which was kept in motion by means
of the arrangement shown in the sketch. A 10-in. cut-glass bowl was
placed, upside down, near the front of the show window. An inverted
tumbler was set upon it and a small tin box was pivoted on the
tumbler by means of a needle soldered inside of it. Six arms of wire
were soldered to the box, and watches were suspended from them. The
carefully balanced frame revolved easily on the point of the needle. It
was kept in motion by the draft from a fan hidden behind a mirror.--H.
S. Hart, Shreveport, La.
A Horse-Drawn Sod Cutter
The cutting of a considerable area of sod is tedious work when done by
hand, and it is difficult to make the sections of uniform thickness
and size. These important features are provided for by the use of the
homemade sod cutter shown in the sketch. To start a cut across a meadow
or lot, a notch is cut in the turf for the blade, and the device is set
into place, stamping it down to give a good start. The operator stands
on the plank in front of the blade, and a little practice will soon
determine the best position for ease in operation. When a cut has been
completed, the cutter is dragged to a fresh starting place, the driver
turning it over on the upper side. The strips are cut into suitable
lengths and piled conveniently for removal with a stone boat or wagon.
[Illustration: With This Device Sod may be Cut Quickly and of Uniform
Width and Thickness]
The device may be made of any suitable width; 15 in. between the inner
edges of the blade, and the latter set to cut a depth of about 2¹⁄₂
in., being desirable. The board is a 2-in. plank, about 4 ft. long. The
blade should be set with the cutting edge slanting slightly downward
so as to make the device “bite” into the ground. A smaller cutter may
be made for use by boys, several of whom may draw it.--F. H. Sweet,
Waynesboro, Va.
A Match-Box Trick
[Illustration]
All that is required to perform this trick is a box of safety matches.
Four matches are removed and three of them arranged as shown in the
sketch. The performer then tells his friends that he will light the
fourth match and set the cross match on fire in the center, then asks
which match of the standing ones will light first. Most persons will
not stop to think and guess either one or the other. As a matter of
fact, after the cross match is set on fire it soon burns the wood away,
and the pressure of the two side matches will cause it to spring out
so that neither catches fire.--Contributed by Abner B. Shaw, North
Dartmouth, Massachusetts.
Cutting Glass Bottle with Electricity
[Illustration]
Performing an experiment in a laboratory, it became necessary to have
some apparatus which we did not possess at the time. A bell jar could
have been used, but this we did not have, and as a substitute we used
a large glass bottle, 8 in. in diameter, with the bottom removed.
In order to do this, we first made a mark around the outside of the
bottle near the bottom with a glass cutter. A piece of copper wire,
¹⁄₃₂ in. in diameter, was then wound around the outside on the mark and
connected to the circuit.
As the wire would expand enough to make it slip off the bottle when
heated red-hot, pliers were used to keep it taut about the bottle when
the current was turned on. A current of 110 volts and 5 amperes was
run through the wire, heating it red-hot, and this cracked the glass
exactly on the line marked by the glass cutter.--Contributed by R. E.
Hollis, Chicago, Ill.
Nail Cabinet with Muffin-Pan Trays
Muffin-pan trays used by the housewife in baking make serviceable
containers for nails, screws, and other small articles used in a shop.
The illustration shows the pans fitted into a box, and sliding in
grooves cut into the sides with a saw.
[Illustration: The Metal Trays Are Substantial and may be Removed
Readily for Use Elsewhere]
The box is made with the end pieces lapping over the top and the bottom
this being a better construction to carry the weight of the trays. The
wood used in the sides is ⁷⁄₈ in. thick, in order that a saw cut may
be made to a depth of ¹⁄₄ in. without weakening the support. Thinner
wood may be used if instead of saw cuts small strips of wood are nailed
against the side on which the trays may slide.--Contributed by Harry J.
Blacklidge, San Rafael, Cal.
Waterproofing Matches
Dipping ordinary parlor matches into melted paraffin and permitting
them to dry thoroughly will enable them to withstand water. The
paraffin acts like a wax candle and is unaffected by the moisture. This
should be of aid to campers and others who find it hard to keep matches
dry.--Contributed by T. W. Lambert, Jr., New York, N. Y.
[Illustration: Homemade Electric Locomotive Model and Track System
BY A. E. ANDREW
PART I--The Motor]
The electric locomotive described may be constructed by boys having
average mechanical ability and the necessary tools. However, in any
piece of mechanical construction care must be taken to follow the
instructions. The material required is inexpensive, and the pleasure
derived from such a toy is well worth the time used in its construction.
The making of the outfit may be divided into three parts, the first of
which is the motor; second, the truck which is to carry the motor and
the body of the car, and third, the track system upon which the engine
is to operate. A side view of the locomotive is shown in Fig. 1.
The motor is of the series type, having its field and armature
terminals connected to the source of electrical energy through a
special reversing switch. By this means the rotation of the armature
may be reversed to make the locomotive travel forward or backward. The
armature and field are constructed of sheet-iron stampings, riveted
together.
The detailed construction of the armature and its dimensions are shown
in Fig. 2. The shaft upon which the armature core and commutator are
to be rigidly mounted is made of a piece of steel rod, ⁷⁄₃₂ in. in
diameter. A portion of this rod, 2¹⁄₄ in. long, is threaded with a fine
thread, and two small brass, or iron, nuts are provided to fit it. The
ends of the rod are turned down to a diameter of ¹⁄₈ in. for a distance
of ¹⁄₈ in. These are to fit in the bearings that are to be made later.
Cut from thin sheet iron a sufficient number of disks, 1¹⁄₈ in. in
diameter, to make a pile exactly ⁵⁄₈ in. thick when they are securely
clamped together. Drill a hole in the center of each of these disks, of
such a size that they will slip on the shaft snugly. Remove the rough
edges from the disks and see that they are flat. Cut two disks of the
same size, from a piece of ¹⁄₁₆-in spring brass, and drill a hole in
the center of each, so that they will slip on the shaft. Place all
these disks on the shaft, with the brass ones on the outside, and draw
them up tightly with the nuts provided. Be sure to get the laminated
core in the proper position on the shaft by observing the dimensions
given in the illustration, Fig. 2.
[Illustration: FIG. 1
Side View of a Locomotive Designed to be Operated with Either End
Forward]
After the disks have been fastened, clamp the shaft in the chuck of
a lathe and turn down the edges of all the disks so that they form a
smooth cylinder, 1¹⁄₁₆ in. in diameter. Draw a circle on the side of
one of the brass disks, ³⁄₃₂ in. from the edge, while the shaft is held
in the chuck. Divide this circle into eight equal parts and make a
center-punch mark at each division. Drill eight holes through the core
lengthwise with a ³⁄₁₆-in. drill. If the centers of the holes have been
properly located, all the metal on the outside will be cut away, as
shown in the end view, at the right in Fig. 2. The width of the gaps,
F, G, H, etc., thus formed, should be about ¹⁄₁₆ in. Smooth off all the
edges with a fine file after the holes are drilled.
A cross-sectional view of the commutator is shown at the extreme left,
Fig. 2. It is constructed as follows: Take a rod of copper or brass,
⁷⁄₈ in. diameter, and 1¹⁄₄ in. long; clamp one end in the chuck of a
lathe. Turn the other end down to a diameter of ³⁄₄ in., and drill a
¹⁄₂-in. hole through it at the center. Cut away the metal from the end
to form a disklike recess.
Cut off a disk, ⁵⁄₁₆ in. thick, measuring from the finished end, from
the piece of stock. Place this disk in a chuck, with the unfinished
end exposed, and cut away the metal in a dish form, as shown at B. Cut
small slots, into which the ends of the wires used in winding are to be
soldered, as shown at 1, 2, 3, etc., in the right-hand view of Fig. 2.
Obtain two brass nuts, about ¹⁄₄ in. in thickness, and turn their edges
down so that they correspond in form to those shown at C and D. Divide
the disk ring, just made, into eight equal parts, by lines drawn across
it through the center. Cut eight slots at these points, in the rim of
the disk. These cuts should be through the rim. Fill each of the slots
with a piece of mica insulation.
[Illustration: FIG. 2
FIG. 3
How the Armature Core is Made of Soft-Iron Disks for the Lamination,
at the Left. Diagram for the Winding of the Armature Coils and Their
Connection to the Commutator, at the Right]
Place one of the nuts on the shaft and then a washer of mica insulation
shown by the heavy lines, near A and B; then the ring, a second piece
of mica, and last the nut, C. The latter should be drawn up tightly, so
that the insulation in the slots in the disk are opposite the drilled
slots in the armature core, as shown in the right-hand view of Fig. 2.
After the disk has been fastened securely, test it to learn whether it
is insulated from the shaft. This is done by means of a battery and
bell, connected in series, one terminal of the circuit being connected
to the disk, and the other to the shaft. If the bell rings when these
connections are made, the ring and shaft are not insulated. The disk
must then be remounted, using new washers of mica insulation. Mica is
used because of its ability to withstand a higher degree of heat than
most other forms of insulation.
Each of the eight segments of the dished disk should be insulated from
the others. Make a test to see if the adjacent commutator segments
are insulated from each other, and also from the shaft. If the test
indicates that any segment is electrically connected to another, or to
the shaft, the commutator must be dismantled, and the trouble corrected.
The armature is now ready to be wound. Procure ¹⁄₈ lb. of No. 26
gauge insulated copper wire. Insulate the shaft, at E, with several
turns of thin cloth insulation, and also insulate similarly the nuts
holding the armature core and the inside nut holding the commutator.
Cut several pieces from the cloth insulation, wide enough to cover the
walls of the slots in the core, and long enough to extend at least ¹⁄₁₆
in. beyond the core at the ends. Insulate slots F and G thus, and wind
15 turns of the wire around the core lengthwise, passing the wire back
through the slot F, across the back end of the core, then toward the
front end through slot G, and back through F, and so on. About 2 in. of
free wire should be provided at each end of the coils.
In passing across the ends of the armature, all the turns are placed on
one side of the shaft, and so as to pass on the left side, the armature
being viewed from the commutator end. The second coil, which is wound
in the same grooves, is then passed on the right side, the third on the
left, and so on. After this coil is completed test it to see if it is
connected to the armature core. If such a condition is found, the coil
must be rewound. If the insulation is good, wind the second coil, which
is wound in the same slots, F and G, and composed of the same number of
turns. Insulate the slots H and J, and wind two coils of 15 turns each
in them, observing the same precautions as with the first two coils.
The fifth and sixth coils are placed in slots K and L, and the seventh
and eighth, in slots M and N.
The arrangement of the half coils, slots, and commutator segments is
given in detail in Fig. 3. Each coil is reduced to one turn in the
illustration, in order to simplify it. From an inspection of this
diagram it may be seen that the outside end of the second coil in the
upper row of figures, at the left end, is connected to the inside
end of the fourth coil at segment 1, in the lower row of figures,
representing the segments of the commutator. The outside end of the
fourth coil is connected with the inside end of the sixth coil, at
segment 2; the outside end of the sixth coil is connected with the
inside end of the eighth coil at segment 3; the outside end of the
eighth coil is connected to the inside end of the coil 1 at segment 4;
the outside end of the coil 1 is connected to the inside end of the
coil 3 at segment 5; the outside end of the third coil is connected
to the inside end of the fifth coil at segment 6; the outside end of
the fifth coil is connected to the inside end of the seventh coil at
segment 7; the outside end of the seventh coil is connected to the
inside end of the second coil at segment 8, and the outside end of the
second coil is connected to segment 1. completing the circuit.
[Illustration: FIG. 4
Pattern for the Field Stampings, Several Pieces being Used to make the
Desired Thickness]
In winding the coils on the core, their ends should be terminated close
to the commutator segments to which they are to be connected, in order
to simplify the end connections. After all the coils are wound and
properly tested, their ends may be connected as indicated. They are
then soldered into the slots in the ends of the commutator segments.
The completed winding is given a coating of shellac.
The dimensions and form of the field stampings are given in Fig. 4. A
number of these cut from thin sheet iron to make a pile ⁵⁄₈ in. thick
when clamped together is needed. The dimensions of the opening to carry
the armature should be a little less than that indicated in the sketch,
as it will be necessary to true it up after the stampings are fastened
together. Use one of the stampings as a pattern, and drill seven small
holes in each, as indicated by the letters O, P, Q, R, S, T, and U.
Fasten them together with small rivets, and true up the opening for
the armature to a diameter of 1¹⁄₈ in. Drill five ¹⁄₈-in. holes, as
indicated by the letters V, W, X, Y, and Z, to be used in mounting the
pieces, which are to form the armature bearings, brush supports, and
base of the motor.
[Illustration: FIG. 5
FIG. 6
Detail of the Field-Structure Supports, One Being for the Left Side and
the Other for the Right. The Supports are Shown in the Place at the
Right]
Cut two rectangular washers from a piece of thin fiber insulation, with
outside dimensions of 1¹⁄₈ in. and 1¹⁄₄ in., and an inside opening, ¹⁄₂
in. by ⁵⁄₈ in. Cut open these washers and slip them in position on the
portion of the field marked ZZ. Wrap two turns of the cloth insulation
about this part, which is to form the field core, and wind the space
full of No. 18 gauge enamel-insulated copper wire. Give the completed
winding a coat of shellac. The terminals of this winding should be
brought out through two holes drilled in one of the fiber washers, one
near the core and the other near the outer edge. It is better to have
the field terminals at the lower end of the part ZZ than at the upper
end.
[Illustration: FIG. 7
Detail of the Brush Holders, One Inch Long, with Holes as Shown]
Now cut two pieces from ¹⁄₁₆-in. sheet brass, similar to those shown in
Fig. 5. Place them on opposite sides of the laminated field structure,
shown in Fig. 4, and carefully mark the position of the holes, V, W,
X, Y, and Z, as indicated in Fig. 4, and drill ¹⁄₈-in. holes, where
the marks were made. Lay out and drill ¹⁄₈-in. holes, A, B, C, and
D, Fig. 5. Bend the upper portion of the pieces at right angles to
the lower portion, along the dotted lines E, and then bend the end of
the horizontal portions down along the dotted lines F, until they are
parallel with the main vertical parts of the pieces. The latter should
be bent so that one forms the left support and the other the right, as
shown in Fig. 6.
Bend the projections G and H at right angles to the vertical main
parts. The parts at the bottom are bent, one back along the dotted line
J and forward on the line K; the other forward on the line L and back
on the line M. The pieces are then mounted, on the side of the field
structure, as shown in Fig. 6. The supports are fastened in place with
five small bolts. The grooves N and O, in Fig. 5, are used in mounting
the motor on the axles of the truck. They will not be cut until after
the truck is constructed.
The brush holders are made of two pieces of hexagonal brass, each 1 in.
in length, having a ¹⁄₈-in. hole drilled in the end to a depth of ⁷⁄₈
in., and a threaded hole in the other end, for a small machine screw,
as shown in Fig. 7. Two holes are drilled and threaded in one side of
each of these pieces. These holders are to be mounted, by means of
screws, through the holes A, B, C, and D, Fig. 5. Each holder must be
insulated from its support. The distance of the holder from its support
should be such that the opening in its end is in the center of the
commutator. The brushes are made of very fine copper gauze, rolled to
form a rod. They are made long enough to extend about ¹⁄₂ in. into the
holder, when they are resting on the commutator. A small spiral spring
is placed in the holder, back of the end of the brush, and which will
serve to keep the latter in contact with the commutator.
Temporary connections are made and the motor is tested with a six-volt
battery. The construction of the motor may be modified as to the length
of shaft, and other minor details, and may be used for other purposes
by fitting it with pulleys, a countershaft, or other transmission
devices.
Making String Solder
String solder of a size convenient for electrical work, or other
soldering, where only a small quantity is desired, may be made by
adapting a ladle for the purpose. Drill a small hole through the ladle
near its upper edge. Melt the solder and pour it through the small
hole, permitting it to fall on a slab of marble, slate, or stone. The
ladle must be moved in zigzag lines in order to prevent the string from
crossing and to make it possible to roll up the solder into rings of a
convenient size.--Contributed by L. E. Fetter, Portsmouth, N. H.
To Prevent Wire Coat Hook from Turning
[Illustration]
A good way to keep a common wire coat hook in an upright position is to
drive a small wire staple over the smaller hook. In public places, such
as halls, this will often prevent their removal and save considerable
annoyance.--Contributed by Harry L. Dixson, Chicago, Ill.
* * * * *
¶The second coat of varnish should never be put on until the first
has been “mossed” (rubbed) off; as, otherwise, it will not stick well.
Cement Grotto for an Aquarium
To build a small cement grotto for an aquarium, make a clay mold by
roughly excavating two right-angled gutters in a lump of clay. Grease,
or shellac, the mold after it is dry. Apply cement of about the
consistency of putty, or dough, filling the gutters roughly so as to
give a rocklike finish. Small shells can be stuck into the cement while
it is yet moist. Before entirely shaping the cement, a piece of heavy
wire is bent to conform to the shape of the grotto and set in for a
reinforcement.
[Illustration: Cement Grotto Roughly Molded over Clay, Shaped to Make
the Right Form]
Holes can be made by twisting paper, so that it will extend out at each
side, and laying cement over it. After the cement is thoroughly dry,
the paper can be removed in sections.
Lamp Wicks Cheaply Made
[Illustration: Cut the Hat into Halves and Then Cut It into Strips,
from Which the Wicks are Made]
Lamp wicks may be made cheaply at home from an old soft-felt hat. The
hat should first be brushed clean and the brim flattened by ironing
it. The greatest number of wicks may be obtained if the hat is cut
into halves with a pair of scissors, and then cut into strips of the
required size, as shown in the sketch. Soak the strips in vinegar for
two hours, dry them out of doors, if convenient, and they are ready for
use.--Contributed by George H. Holden.
Concrete Water Basin for Poultry
[Illustration: An Ordinary Washbasin was Used to Shape the Depression
in the Concrete]
A concrete worker was asked by a farmer to build a concrete basin for
watering the poultry. Having no forms at hand, the mechanic used an
ordinary washbasin and a wood box as shown in the illustration. The
basin was greased before it was placed in the concrete. The completed
concrete basin was buried with its upper surface level with the
ground.--Contributed by James M. Kane, Doylestown, Pa.
Substitute for Ground Glass in Camera
The ground glass in my camera was broken while arranging to take a
picture of a party one evening, and being unable to obtain another, I
substituted a piece of white tissue paper drawn over a piece of plain
glass. It did the work so well on that occasion that I have used it
continuously since, and have found it better than the ground glass. It
produces superior definition in the views on the glass, especially when
working in a poor light, and in a good focusing screen.--Contributed by
C. W. Smalley, Des Moines, Ia.
Pencil Holder for Workbench
[Illustration]
Mechanics, and others who have occasion to use a pencil on a workbench
will appreciate the pencil holder shown in the sketch. It was made by
soldering the small brass ferrule into the bottom of a portion of a
brass knob, and weighting the knob with lead. The pencil will be held
in an upright position where it may be easily seen.--Contributed by R.
F. Hoffman, Chicago.
Repairing Burned-Out Incandescent Globes
Incandescent electric bulbs that have been burned out may be repaired
by shaking them, in order to cause the broken ends of the metal
filament to strike together. By examining the broken filament one can
determine in what direction to shake the globe. The sudden passage
of the current upon contact causes an arc at the broken ends of the
filament, welding them. A globe thus repaired should be placed in a
socket where it will not be given undue disturbance and will then last
for a considerable period.
[Illustration: Homemade Electric Locomotive Model and Track System
BY A. E. ANDREW
PART II--Construction of the Locomotive Truck and Cab]
Successful operation and construction that is feasible, yet of
a reasonable standard of workmanship, are the essentials of the
locomotive truck and cab described as the second feature of the
locomotive and track system under consideration. The materials
suggested are those found to be satisfactory, but substitutes may be
used if caution is observed. The completed locomotive is shown in Figs.
1 and 2. The outward aspect only is presented, and, for the sake of
clearness, the portions of the motor and driving rigging attached to
it, that project below the cab, are omitted, These parts are shown
assembled in Fig. 12, and in detail in the succeeding sketches.
The locomotive, apart from the motor, consists of two main portions,
the truck and the cab. Consideration will be given first to the
building of the truck and the fitting of the motor into it. The
mechanical and operative features are to be completed before beginning
work on the cab, which is merely a hood fixed into place with screws,
set into the wooden cab base.
Begin the construction with the wheels, shown in Fig. 3. Make the axles
of ¹⁄₈-in. round steel rod, cut 3³⁄₁₆ in. long.
Turn four wheels of ³⁄₈-in. brass. Drill a ¹⁄₈-in. hole in two of them
so that they may be forced on the slightly tapered ends of the axle.
Drill a ¹⁄₄-in. hole in each of the other wheels, and solder a collar,
A, Fig. 3, on the inside surfaces of them. Two fiber bushings, B,
should be provided to fit in the ¹⁄₄-in. openings in the wheels and to
fit tightly on the ends of the axles. This insulates the wheels on one
side of the truck from those on the other. If the rails forming the
track are insulated from each other, the current supplied to the motor
may pass in on one rail to the two insulated wheels, then to a brush,
which bears on the brass collar A, through the windings of the motor,
through the reversing switch to the other set of wheels, and back to
the source of energy over the other rail, as shown in Fig. 15.
The wheels of the truck should fit on the axles tightly, since no means
other than the friction will be employed in holding them in position.
If the ends of the axles are tapered slightly, the wheels may be forced
into place and will stay firmly. Do not force them on until the truck
is finally assembled.
The truck frame should be constructed next, and its details are shown
in Figs. 4 and 5. Make two sidepieces of ¹⁄₁₆-in. brass, 9³⁄₄ in. long
and 1⁵⁄₈ in. wide, cutting out portions, as shown, in order to reduce
the weight. This also gives the appearance of leaf springs.
The two rectangular openings are to accommodate the axle bearings. They
should be cut to precise dimensions, and their edges should be squared
off. Extensions, ¹⁄₁₆ in. wide, are provided at the middle of the upper
edges of each of these openings. They are to hold the upper end of the
coil springs, which are to rest in the holes cut into the bearings, as
shown at G, Fig. 7, and also in assembled form, Fig. 6.
Next drill four ¹⁄₈-in. holes in each of the sidepieces, as indicated
at the letters H₁ to H₄, Fig. 5. For the cross supports use four pieces
of brass rod, ¹⁄₄ in. square, and square off the ends to a length of
2³⁄₄ in. Drill holes in the center of the ends and tap them for ¹⁄₈-in.
machine screws. Join the side and crosspieces as shown in Fig. 4. Two
fiber washers about ¹⁄₁₆ in. thick should be placed on each axle at E
and F, to hold the wheels from contact with the sidepieces.
Details of a bearing for the axles are shown in Fig. 7. The hole G
carries the lower end of the coil spring, and the hole J is the bearing
socket for the axle. Four spiral springs, having an outside diameter of
¹⁄₈ in. and a length of ¹⁄₂ in. when extended, should be provided. The
extensions on the sides of the bearings fit against the inner faces of
the sides of the truck. They hold the bearings in position and prevent
them from falling out.
The base of the cab is made of wood, dimensioned as in Fig. 10. The
center of the piece is cut away so as to provide a space for the
motor, which extends above the upper edge of the truck, as shown in
Fig. 12. This block is fastened in place by four screws through the
upper crosspieces at the ends of the truck. The base should be made
and fitted into place temporarily so as to be available in observing
how the motor and its fittings are placed in relation to it. For
convenience in assembling the parts of the truck and setting the motor,
it may be removed readily.
Assembling the truck, including the motor, probably requires the most
painstaking effort of any part of the construction of the locomotive.
Too great care cannot be taken with it, as the dimensions are carefully
worked out and failure to observe them may cause errors sufficient to
make the locomotive unserviceable. Before undertaking this work it
would be well to examine carefully the arrangement of the parts as
shown in Fig. 12. The upper view shows the relation of the driving
gears in mesh, and the lower view shows the machinery of the truck as
seen from above.
The power from the motor is transmitted to one set of wheels by means
of a small gear on the armature shaft engaging an intermediate gear,
which in turn engages a large gear attached to the inside of one of the
truck wheels. The center of the armature shaft is 1⁵⁄₁₆ in. from the
center of the power axle, when both axles are in the slots provided in
the motor frame, Fig. 12. The gears for the transmission may now be
selected. The gear on the armature shaft should be as small, and that
on the axle as large, as practicable. The intermediate gear should be
of such a size that it will close the space between the small gear on
the armature shaft and the large one on the axle. Gears suitable for
the transmission may be purchased at a clock store for a small sum.
If gears of exactly the proper size cannot be obtained readily, the
position of the intermediate gear may be adjusted to produce a proper
meshing of the gears.
Mount the small gear on the end of the armature shaft away from the
commutator, so that there will be about ¹⁄₁₆-in. clearance between the
outside surface and the shoulder at the end of the shaft. Fit it on
tightly so that no other means of fastening will be necessary. Mount
the large gear on the inside surface of one of the truck wheels, as
shown in Figs. 3 and 12. Place the axle of the truck into the proper
grooves in the motor frame, and mark the position of the center of the
intermediate gear, when it engages the other gear. Drill a hole in the
extension on the motor frame, provided as a support, to fit a small
bolt with which the intermediate gear is fastened.
Place a washer between the gear and the piece upon which it is mounted,
and a locknut on the threaded end of the bolt, drawing it up so that
the gear has only sufficient play.
[Illustration: SIDE AND FRONT VIEW OF COMPLETED LOCOMOTIVE
FIG. 1
FIG. 2
CONSTRUCTION OF WHEELS
FIG. 3
SIDE OF TRUCK
FIG. 5
FIG. 4
FIG. 6
TOP AND SIDE VIEW OF BEARING
FIG. 7
FIG. 8
FIG. 9
FIG. 11
FIG. 10
BOTTOM OF LOCOMOTIVE CAB
Successful Operation Based on Feasible Construction and a Reasonable
Standard of Workmanship, Is the First Consideration in the Locomotive.
The Dimensions should be Observed Closely in Order That the Parts may
be Assembled Satisfactorily. The Construction of the Cab is Suggestive
Only, and the Inventive Builder may Design One in Conformity with the
Material Available or the Individual Taste]
The slots in the motor frame to fit the free axle may now be cut, as
shown in Fig. 12. Place the motor in position on the axle so that the
gears all mesh properly. Fit tubes of insulating material with an
outside diameter of ³⁄₈ in. at C and D, Fig. 3, and as also shown in
Fig. 12. Insulation tubes should be provided for the second axle so
as to hold the motor in position, and to keep the wheels in line. In
mounting the various parts sufficient play should be allowed to prevent
excessive friction.
[Illustration: Fig. 12, Installation of the Motor, Showing Gears and
Switch Contact Spring]
The reversing switch, which is to be mounted on the under side of the
motor frame, is shown in Figs. 13 and 14. It is provided with a control
lever which projects out from under the truck frame. A small movement
of the lever will produce the necessary changes in the connections.
The operation of the switch may be understood readily from the diagram
shown in Fig. 15. The moving element of the switch carries two pieces
of copper, E and F, which connect the four stationary pieces of copper,
A, B, C, and D, when the lever attached to E and F is moved to either
side of its central position. The pieces of copper which are moved--E
and F--are shown outside of the stationary pieces in Fig. 15 for
purposes of a diagram only, and are actually directly over the ring
formed by the stationary pieces.
[Illustration: Fig. 13, Details of the Switch, Shaded Portions Being of
Fiber Insulation]
The operation of the switch is as follows: Assuming that the current
enters at the terminal marked 1 and leaves at the terminal marked 2,
then the direction of the current in the armature and series field will
be as indicated in the diagrams. The direction of the current in the
series-field winding is different in the two cases, which will result
in opposite rotation of the armature.
The base of the switch is made of ¹⁄₁₆-in. fiber insulation; its
dimensions are shown in Fig. 13. It is to be mounted on the two pieces
projecting outward on the under side of the motor frame, as shown in
Fig. 14. Drill a small hole in each of these projections, as indicated
by the letters H₁ and H₂, and tap them to take a small machine screw.
Next drill two holes, H₁ and H₂, Fig. 13, in the piece of insulation,
with centers the same distance apart as those drilled in the
projections. One end of this piece of insulation is extended to form a
mounting for a thin brass spring, the ends of which bear on the brass
collars insulated from the axles, as shown in Figs. 12 and 13. The form
of this spring and the method of mounting it are also shown in Fig. 13.
The sections which come into contact in the switch are made as follows:
Mount four pieces of thin copper or brass on the fiber base with rivets
having their heads countersunk. Cut a disk, 1 in. in diameter, from a
piece of sheet insulation and drill a hole H, in the center of it. Also
drill a similar hole H₃ in the center of the switch base. Mount two
pieces of copper or brass, E and F, on the under side of this disk.
The edges and ends of all six pieces of metal should be rounded off so
that the pieces E and F will move freely over those on the base. The
disk, or upper part of the switch, may be attached to the base by means
of a small bolt placed through the holes at the center. A small spiral
spring should be placed between the disk and the lower end of this bolt
so as to keep the pieces of metal on the disk in contact with those on
the base. Attach a small handle to the disk so that it will extend out
on one side of the truck. Fix the switch into place by bolts through
the holes H₁ and H₂, Fig. 14, on the bottom of the motor frame. The
electrical connections should be made as shown in Fig. 15.
The detail of the couplers is shown in Fig. 11. They are made of brass,
fitted to the upper crosspieces and fixed to them by machine screws.
“Cowcatchers” may be made for the ends of the locomotive. Sheet metal,
corrugated appropriately and bent to the proper shape, will afford the
easiest method of making them. Those shown in Figs. 1 and 2 are made of
strips soldered together, and also to the upper crosspieces; they are
strengthened by a cross strip at the bottom, opposite the point.
[Illustration: Fig. 14, View of the Under Side of the Motor, Showing
How Switch is Fixed into Place]
The cab is to be made apart from the truck and is to fit upon the base,
as shown in Figs. 1 and 2. It is fixed into place by four screws and
can be removed easily for examination of the locomotive mechanism. The
dimensions for the cab are shown in Figs. 8 and 9, and may be varied by
the builder.
[Illustration: Fig. 15, Diagrams of the Reversing of Motor by Shifting
Switch to Form Contact Between Pairs of Brass Sectors Set in the Fiber
Switch Base]
Sheet metal or wood may be used in the construction, and the joints
soldered on the inside or riveted, as shown in the illustration. The
window and door openings may be cut out or painted on. Small bells
may be mounted on the ends of the cab, adding to its appearance. The
headlights shown in Figs. 1 and 2 may be cut from wood or made of
sheet metal. Light bulbs may be installed, and their voltage should
correspond to that of the motive energy. The terminals for the sockets
of the headlight lamps should be connected to the frame of the truck
and to the spring, which bears upon the brass collars on the wheels,
which are insulated from the axles, as shown at A, Fig. 3.
This completes the locomotive in all essential details and it is ready
to be placed upon the track to be tested. The track system will be
considered in a subsequent article.
Mixing Paste
When flour paste becomes watery upon cooling, it is evidence that
the mixture has been boiled too long. Only the best flour should be
used for making paste. Many paper hangers do not boil paste. They
make a stiff batter with lukewarm water, stirring out all lumps, and
then briskly stir in boiling water. When the mass thickens continue
stirring, but add no more hot water. Pour a little cold water on top
and set the paste away to cool.--Contributed by A. A. Kelly, Malvern,
Pa.
A Hammock Sleeping Tent
[Illustration: A Comfortable Sleeping Tent is Provided by the
Arrangement Shown in the Sketch]
Compactness in transportation and general serviceableness are features
of the hammock tent shown in the illustration. It is made by sewing a
piece of canvas to the sides of an ordinary “dog” or shelter tent and
may be made of a piece of canvas or tarpaulin. The tent is suspended
by the ridge from a heavy rope supported on trees or posts. It is
kept taut on the sides by tent ropes attached to stakes driven in the
ground. This form of tent is particularly convenient in providing a
good sleeping place in very small space. It is free from dampness,
and the camper is provided with a comfortable rest free from prowling
animals, without the use of a cot.--Daniel C. Duvall, Washington, D. C.
Broken Spade Handle Repaired with Water Pipe
A garden spade, or fork, broken at the handle may be repaired by
joining the broken ends with a piece of old iron water pipe. The broken
ends should be trimmed carefully and driven into the piece of pipe. In
order to make a more secure joint, holes may be bored and countersunk
at each end of the pipe and screws fixed into them. If the break is so
close to the handle that the latter is useless, a new one may be made
by fixing a pipe tee, with a wooden rod as a handle, to the end of the
fork or spade.--George H. Holden, Chesterfield, England.
Tilting Top for Camera Tripod
[Illustration: The Homemade Tilting Top Is Convenient in Making
Photographs at a Variety of Angles]
Pointing a camera up, or down, as in photographing tall buildings with
the ordinary camera tripod, is awkward and requires much time to make a
satisfactory adjustment. To overcome this, a tilting top was made for
the tripod, as shown in the illustration. The extra top consists of two
boards hinged at one end. The lower board has a tripod socket to fit
the tripod, while the upper one has a tripod screw for fastening the
camera. Two metal brackets are provided, having slots through which
binding screws are fitted, and clamped with wing nuts. This permits
the camera to be tilted at various angles, or reversed for vertical
pictures, without removing it from the tripod. Several positions
are suggested and a little experimentation will give numerous other
possible uses. Devices of this character may be purchased, but the
one shown is easily made and serves its purpose well.--R. C. Miller,
Pittsburgh, Pa.
[Illustration: Homemade Electric Locomotive Model and Track System
BY A. E. ANDREW
PART III--Construction of the Track System]
Operation of the electric-locomotive model described in the previous
articles is feasible only with a properly constructed track system.
This equipment, including curves and switches, is to be described in
this, the final, article. Two functions are to be performed by the
track system: It must serve as a support and guide for the locomotive
and provide a path over which the current from the source of energy
is supplied to the motor within the locomotive and returned to the
source. On this basis, then, the construction may be divided into two
parts: the mechanical and the electrical features. If the mechanical
construction is not practical and accurate, the locomotive will not
operate satisfactorily. The electrical connections must be given due
care also.
[Illustration: SECTION OF RAIL
FIG. 1
RAIL CONNECTION
FIG. 2
Shape the Rails from Sheet-Metal Strips, 1¹⁄₂ Inches Wide and 16 inches
Long, to the Form Shown in Fig. 1. The Rail Connections are Formed as
Shown in Fig. 2]
The track should be of uniform gauge; the joints should be solid
and free from irregularities, which cause “bumping” in passing over
them. The material used should be stiff, so that it will retain its
form, and preferably non-rusting. The rails must be insulated from
each other, and proper means must be provided for making suitable
electrical connections between the various sections. The construction
of a straight and a curved section of track, together with a switch and
signal, adaptable to various places on the system, will be considered
in detail.
The straight sections may be made any suitable length; sections 16 in.
long will be found convenient, as the metal pieces forming the rails
may be bent into shape easily when they are short rather than long. The
possibility of various combinations of straight and curved sections in
a given area is increased by having the sections shorter. The rails
may be made from tinned sheet-metal strips, by taking pieces, 16 in.
long and 1¹⁄₂ in. wide, and bending them into the form shown in Fig. 1.
The rails should be mounted on small wooden sleepers, ¹⁄₂ by ¹⁄₂ by 4
in., by means of small nails, or preferably small screws. The distance
between the centers of the rails should be 2 in. The sections of track
may be fastened together at the ends by means of a special connector,
shown in Fig. 2, made from thin metal, preferably spring brass. The
type of connector shown in Fig. 2 will not prevent the sections from
pulling apart, and to prevent this, a second connector, similar to
that shown in Fig. 3, should be made. The sleepers at the ends of each
section should have one side beveled, as shown, and these edges should
be exactly one inch from the end of the rails. A spring clip should be
made, similar to that shown, which will slip down on the inside of the
end sleepers and hold the sections together.
[Illustration: METHOD OF CONNECTING TRACK SECTIONS
FIG. 3
SECTION OF RAIL
FIG. 4
END CONNECTION OF RAILS
FIG. 5
A Spring Clamp for the Joints in the Sections is Shown in Fig. 3. An
Improved Form of Rail is Shown in Fig. 4, and in Fig. 5 is Indicated
the Method of Joining Its Sections]
A better form of rail is shown in Figs. 3 and 4, but it is somewhat
more difficult to construct. In this case, instead of bending the
piece of metal forming the rail over on itself and closing the space
entirely, the metal is bent over a round form, such as a piece of wire,
which may be removed, leaving an opening through the upper part of the
rail from end to end. This gives a better form to the tread of the rail
and at the same time provides an easy means of connecting the ends of
the rails, as shown in Fig. 5. Small metal pins, about 1 in. long, and
of such a diameter that they will just fit the circular opening in the
top of the rail, are provided. One of these pins should be fastened
in one rail at each end of a section, making sure that no rail has
more than one pin in it, and that the arrangement of pins and rails
corresponds in all sections. With proper care the various sections
should fit together equally well, and they may be held together as
shown in Fig. 3.
[Illustration: METHOD OF LAYING OUT CURVED SECTION
FIG. 6
LEFT SWITCH
FIG. 7
RIGHT SWITCH
FIG. 8
Lay Out the Switches and Curves, Full Size, and Fit the Rails to the
Curves Accurately]
The curved sections may be made from rails similar to those described
above, but some difficulty will be experienced in bending them into a
curve because of the necessity of bending the lower flange on edge.
The difficulty may be overcome by crimping in the inner edge of the
lower flange and expanding the outer edge by hammering it on a smooth
surface. The radius of the curve to which the inner rail should be bent
in order to give a section of convenient length, and not too abrupt a
curve, is 21 in. The circumference of such a circle is approximately
132 in., which, divided into eight sections, gives 16¹⁄₂ in. as the
length of the inner rail of each section. Since the tread of the track
is 2 in., the radius of the curve of the outer rail will be 23 in. The
circumference of the circle formed by the outer rail is 145 in., which
divided into eight sections gives 18¹⁄₈ in. as the length of the outer
rail of each section. These curved rails may be mounted on sleepers,
their ends being held in place, and the various sections fastened
together, just as in the case of the straight sections.
Some trouble may be experienced in getting the curved rails properly
shaped, and it would be a good plan to lay them out full size by
drawing two circles on a smooth surface having diameters of 42 and
46 in., respectively, and divide each of the latter into eight equal
parts. The form of the curve between these division lines and the
lengths of the curves will correspond to the shape and lengths of the
rails forming the curved sections of the track. The pieces should be
cut slightly longer than required, and after they are bent into shape
their length can be determined precisely and extra portions cut off.
Each curved section will correspond to ¹⁄₈ of the complete circle, or
45°, as shown in Fig. 6.
The switches for the track may be of two kinds: left and right. They
are named according to whether the car is carried to the left or right
of the main track with reference to the direction in which the car
moves in entering the switch. A left switch is shown in Fig. 7, and a
right switch in Fig. 8, the direction of movement being indicated by
the arrows.
[Illustration: DETAILS OF SWITCH
FIG. 9
The Crossings of the Rails must be Fitted Carefully, and the Movable
Sections G and H Arranged to Make the Proper Contacts]
A detailed drawing of a right switch is shown in Fig. 9. Rail A
corresponds in form and length to the outer rail of one of the curved
sections previously described; rail B corresponds to the inner rail of
one of the curved sections except that 2¹⁄₂ in. of straight rail is
added at the left end. Rail C is a straight portion of rail, 18 in.
in length, with a part of the base cut away at the switch, and rail D
is a section of straight rail, 15¹⁄₂ in. in length, with the base cut
away where it crosses rail A. The ends of rails D and A are hinged at
the points E and F, 3³⁄₄ in. from the left end, with pins driven into
the ties. The outside edges of the pieces G and H are filed off so they
will fit up against the rails C and B respectively. Both the pieces G
and H are attached to a strip of fiber insulating material, I, at their
left-hand ends, in such a way that when the piece H is against the rail
B, the piece G is away from the rail C about ³⁄₁₆ in.; when the end of
the piece G is drawn over against the rail C, the end of the piece H is
drawn away from the rail B about ³⁄₁₆ in. With these two combinations
the car may be made to move along the main track or to the right on the
curved track. The two long sleepers J and K are to provide a mounting
for the switch-control lever and signal.
The rail A is not continuous where the rail D crosses it, but is broken
as shown in the figure. A small notch should be cut in the surface
of the rail D where it crosses the rail A, for the flange of the car
wheels to roll through when the car is moving onto or off the switch.
The sections of the rails A and D must be connected electrically. Rail
A must be connected to rail C, and rail B to rail D.
It is obvious from an inspection of Fig. 9, at L, that rail D will
be connected to rail A when the car is on the switch, the car wheels
passing over the point L, and a short circuit will result. This may be
prevented by insulating the short section of the rail D at this point
from the remainder of the rail, but the length of the insulated section
must not be greater than the distance between the wheels on one side
of the car; otherwise the circuit through the motor would be broken.
If this is the case, and the car stops on the main track with both
wheels on the insulated section, it would be impossible to start the
locomotive until one wheel was moved to a live part of the rail.
The switch control is shown in Fig. 10, and the letters C, G, and
I correspond to those given in Fig. 9. A ¹⁄₈-in. rod, about 4 in.
in length, is bent into the form shown at M. It is mounted in a
frame, the details of which are shown in Fig. 11. A small arm, N,
with a hinged handle, O, is soldered to the rod, after it is placed
in position in the switch frame. The arm N and the lever P should be
parallel with each other. If properly constructed, the handle O will
drop into the notches in the top of the switch frame, and prevent the
rod M from turning. A connection should be made from the lever P to
the end of the piece I, which will result in the switch being operated
when the rod M is rotated one-fourth of a turn. After this connection
is made, the frame of the switch should be fastened to the ends of the
long sleepers, which were provided when the track part of the switch
was constructed. Two small disks, mounted at right angles to each
other, will serve as signals when properly painted, or as an indication
of the open or closed position of the switch.
[Illustration: SWITCH CONTROL
FIG. 10
TOP VIEW SWITCH FRAME
FIG. 11
The Signals Indicate the Open or Closed Condition of the Switch by the
Small Disk, Which is Regulated by the Lever Switch Control]
The speed of the car on the track may be controlled by inserting
resistance in series with the battery or source of electrical energy,
or by altering the value of the voltage between the rails, by changing
the connections of the cells forming the battery. The direction of
movement of the locomotive cannot be changed unless the car is turned
end for end, or the connections of the armature or field winding--not
both--are reversed. The switch on the bottom of the locomotive reverses
these connections.
[Illustration: FIG. 12]
A small rheostat, which will give the desired resistance, may be
constructed as follows: Obtain a piece of hard wood, 4 by 5 in., and
³⁄₈ in. in thickness. Lay out a curve on this piece, as shown in Fig.
12 by the row of small circles. Procure eight round-headed brass
machine screws, about ¹⁄₈ in. in diameter and ³⁄₄ in. in length, and 16
nuts to fit them. Drill eight ¹⁄₈-in. holes along the curve, spacing
them ³⁄₈ in. apart. File the heads of the screws off flat and mount the
screws in these holes. Make a metal arm, S, and mount it on a small
bolt passing through a hole drilled at the center from which the curve
was drawn, along which the screws were mounted. This arm should be
of such a length that its outer end will move over the heads of the
screws. Mount two binding posts, Q and R, in the upper corners of the
board and connect R to screw No. 8, and Q to the bolt holding the arm S
in place. Connect small resistance coils between the screws, starting
with screw No. 2; screw No. 1 corresponds to an open circuit and is
shown in contact with the arm S. Two stops, indicated by the black
spots, should be provided, to prevent the arm from moving back of screw
No. 1 or beyond screw No. 8. The board may now be mounted on a suitable
hollow base, and the rheostat is complete.
Two binding posts should be mounted on the ties of one section of
the track, and one of them electrically connected to each of the two
rails, which will give an easy means of making the necessary electrical
connections to the source of energy. After careful examination, to
make certain that the locomotive is in running order, a test run
may be made. If the locomotive operates properly and difficulty is
experienced when it is placed upon the track, check up thoroughly on
all rail connections, insulations, and other elements in the electrical
equipment. Cars of a proper gauge may be coupled to the locomotive,
and “runs” made as extensively as the track system will permit.
Sleeve Aids in Distinguishing Gas-Fixture Chains
[Illustration]
Annoyance through inability to locate quickly the proper chain for
lighting a gas lamp in the dark was overcome by fitting a small brass
tube to one of the chains as shown in the illustration. The tube was
soldered to the chain by which the light is turned on and the other
chain passes through the tube and is grasped below it. To turn on the
light, it is only necessary to slide the hand along both chains and to
grip the tube, drawing on the chain attached to it. To turn the light
off, the exposed end of the other chain is drawn.--Thomas W. Benson,
Hastings upon Hudson, N. Y.
An Ornamental Horn Match Holder
[Illustration]
A match holder made of the horn shell of cattle hoofs mounted on a
wooden shield, as shown in the sketch is both ornamental and useful.
One of the pockets holds the unused matches and the other the burnt
ones. The hoofs were cleaned thoroughly and polished and the edge of
the shield was beveled off and varnished in the natural color of the
wood. The front was lacquered black and also varnished.
* * * * *
¶A small flat piece of wood is convenient for pointing up an eraser.
Driving Thin Metal into Wood
[Illustration]
A slender piece of flat, or round, metal may be driven into a wood
handle without breaking the wood or bending the metal, if it is placed
in a vise and the wood part driven onto the small portion projecting
from the jaws of the vise. Repeat the operation until the metal is
driven far enough into the wood.
Slicing Board for Camp or Kitchen
[Illustration]
The board illustrated was suggested by a device used by a “sandwich
man,” and proved practical for use in the home and especially in the
camp. Potatoes, or other articles of food to be sliced, are placed
in the hollow portion of the board and moved against the edge at the
right, under the knife. The guide, which may be adjusted by means of
the wing nut, permits slices of varying thickness to be cut.--Robert C.
Knox, St. Petersburg, Fla.
Cleanly Pencil Sharpener
[Illustration]
Pencils may be pointed without spreading the dust from them by the use
of the device shown in the illustration. A piece of emery paper is
fixed to one side of the cover of the box. By turning over the cover
with a handle, after a pencil has been pointed, the dust may be dropped
into the box and removed from time to time.--Sidney Block, Detroit,
Mich.
A Weeding Tool
[Illustration: A
B
A Case-Knife Blade Bent and Fastened in a Broom Handle Makes an
Excellent Weeding Tool]
A handy weeding tool may be made of an old case knife--one of the kind
having a wood handle is the best. Remove the handle sides and heat the
blade about 1 in. from the end, then bend it at right angles as shown
at A. Ream out the rivet holes in the handle large enough to allow
screws, about 1 in. in size, to enter. Procure an old broom handle
and saw a slot in one end deep enough to receive the knife shank, and
fasten it with screws, as shown at B. This makes an excellent tool for
removing weeds from beds of young radish, lettuce and other plants,
as it is possible to get close to the plant stem without injuring
it.--Contributed by L. G. Burnand, Lyons, Iowa.
Spray Nozzle Made of Acetylene Burner
[Illustration]
An acetylene burner makes a first-class spray nozzle, even though
the lava tips are broken off level with the metal. The burner may be
secured on a short piece of pipe, as at A, and this inserted in a hose,
or it may be pushed into a hose and wound with wire, as shown at B.
Clamping a Wide Board on a Bench
[Illustration: A Block on the Bench and a Stick in the Vise Served as
Jaws of a Wide Opening]
Having occasion to cut a groove on the surface of a board too wide for
the vise, I rigged up the arrangement shown to hold it. The board was
laid on the bench with the edge slightly projecting, then I nailed a
block firmly to the bench, close to the edge of the board, and placed
a stick in the vise as shown. When the vise screw was turned up, the
board was gripped solidly.--Contributed by S. H. Bosuston, Victoria, B.
C.
Feeding Pan for Poultry
[Illustration: An Ordinary Pan Placed in a Shallow Box Makes the Form
for a Concrete Vessel]
An excellent water or feeding pan for small chicks can be made of
concrete. Take an old pan and place it in an inverted position in a
shallow box, as shown in the sketch, then mix the concrete and pour it
over the pan. When the cement sets, turn it over and a pan will be had
that small chicks can climb out of, should they get into it.
Metal Floor Corners
[Illustration]
The hardest part of a room or stairway to clean is the corners, and
these always collect a good quantity of dirt. Instead of removing
the dirt each time, a better plan is to fix the corner as shown
in the illustration. A triangular piece of brass or copper, 2 in.
on each side, is fastened into the corner with one nail through
the center. These metal pieces are especially desirable in public
buildings.--Contributed by Abner B. Shaw, N. Dartmouth, Mass.
[Illustration]
Measuring Resistance with a Lead Pencil
BY JOHN D. ADAMS
There are very few electrical experimenters who can afford a Wheatstone
bridge for measuring resistances, and yet, if one is to gain any
knowledge from his experiments, it is very necessary to know what
resistance is being used, particularly in handling 110 volts. The
amateur will find the following method very useful.
There are several brands of lead pencils, the leads of which have a
resistance of 200 to 300 ohms, while others have comparatively little
resistance. Soak several pencils--preferably the large kind carpenters
use--in water over night so that the leads may be removed without
breaking. Connect up two 40-watt lamps in series and note how they
burn. Then replace one lamp with a lead and note the relative intensity
with which the remaining lamp burns. If the lead is of a sufficiently
high resistance it will cut down the illumination about as much as the
additional lamp.
Having selected a lead, mount it on a suitable board, holding it in
place by clamping each end under a strip of brass held down with wood
screws. Next screw in place two porcelain receptacles and place three
binding posts in position, all as shown in the sketch. Connect up as
indicated, and attach a short length of flexible cord, with a metal tip
on the free end, to one terminal of the central receptacle. Procure
a cheap 75-ohm receiver and connect it to the two ends of the pencil
lead. Finally glue on a paper scale.
[Illustration: The Lead Taken from a Lead Pencil and Used as a Means of
Measuring Resistance]
To operate, place a high-resistance lamp in the center receptacle--say,
a 15-watt lamp--to prevent heating, and almost any lamp of known
wattage in the other receptacle. From the rating of this lamp the
resistance may at once be determined by Ohm’s law. Thus, at 110 volts,
a 25-watt lamp will have a resistance of 484 ohms; a 40-watt lamp 300
ohms, and a 60-watt lamp, 200 ohms. Connect the unknown resistance, as
shown in the drawing, and move the metal tip on the end of the flexible
cord back and forth along the pencil lead until a point is reached
where no sound is emitted by the receiver. This point will be very
well defined, and as the connection is moved away from it in either
direction the sound will increase rapidly. Note the reading on the
scale, and then if a 40-watt lamp is used in the end receptacle, the
unknown resistance will be
300 A
= -----.
B
The resistance of the center lamp does not enter into the computation,
but by changing the lamp in the end receptacle, another set of figures
may be obtained, and a means had to secure increased accuracy.
A Simple Motor Controller
The controller described is very similar in operation to the types
of controllers used on electric automobiles, and its operation may
be easily followed by reference to the diagrammatic representation
of its circuits, and those of a two-pole series motor to which it is
connected, as shown in Fig. 1. The controller consists of six flat
springs, represented as small circles and lettered A, B, C, D, E, and
F, which make contact with pieces of narrow sheet brass mounted on a
small wood cylinder, so arranged that it may be turned by means of a
small handle located on top of the controller case in either direction
from a point called neutral, which is marked N. When the cylinder of
the controller is in the neutral position, all six contact springs
are free from contact with any metal on the cylinder. The contacts
around the cylinder in the six different horizontal positions are
lettered G, H, J, K, L, and M. There are three different positions
of the controller in either direction from the neutral point. Moving
the cylinder in one direction will cause the armature of the motor to
rotate in a certain direction at three different speeds, while moving
the cylinder in a reverse direction will cause the armature to rotate
in the opposite direction at three different speeds, depending upon the
exact position of the cylinder. These positions are designated by the
letters O, P, and Q, for one way, and R, S, and T, for the other.
[Illustration: FIG. 1
Diagram of the Electrical Connections of a Controller to a Two-Pole
Series Motor]
Supposing the cylinder to be rotated to the position marked O, the
circuit may be traced from the positive terminal of the battery U, as
follows: To contact spring E, to strip of brass L, to strip of brass
M, to contact spring F, through the field windings VV, to contact
spring D, to strip of brass K, to strip of brass J, to contact spring
C, through resistance W and Y, to armature Z, through armature to the
negative terminal of the battery. Moving the cylinder to the position
P merely cuts out the resistance W, and to the position Q, cuts out
the remaining resistance Y. The direction of the current through the
armature and series field, for all positions of the cylinder to the
left, is indicated by the full-line arrows. Moving the controller to
the positions marked R, S, and T, will result in the same changes in
circuit connections, as in the previous case, except the direction of
the current in the series field windings will be reversed.
[Illustration: FIG. 2
Upper-End View of the Controller, Showing the Manner of Attaching the
Springs]
The construction of the controller may be carried out as follows:
Obtain a cylindrical piece of wood, 1³⁄₄ in. in diameter and 3¹⁄₈ in.
long, preferably hard wood. Turn one end of this cylinder down to a
diameter of ¹⁄₂ in., and drill a ¹⁄₄-in. hole through its center from
end to end. Divide the circumference of the small-diameter portion
into eight equal parts and drive a small nail into the cylinder at each
division point, the nail being placed in the center of the surface
lengthwise and perpendicular to the axis of the cylinder. Cut off all
the nail heads so that the outer ends of the nails extend even with
the surface of the outer, or large-size, cylinder. Divide the large
part into eight equal parts so that the division points will be midway
between the ends of the nails, and draw lines the full length of the
cylinder on these points. Divide the cylinder lengthwise into seven
equal parts and draw a line around it at each division point. Cut some
¹⁄₈-in. strips from thin sheet brass and mount them on the cylinder to
correspond to those shown in Fig. 1. Any one of the vertical division
lines drawn on the cylinder may be taken as the neutral point. The
pieces may be mounted by bending the ends over and sharpening them so
that they can be driven into the wood. The various strips of brass
should be connected electrically, as shown by the heavy lines in Fig.
1, but these connections must all be made so that they will not extend
beyond the outer surface of the strips of brass.
A small rectangular frame is made, and the cylinder is mounted in a
vertical position in it by means of a rod passing down through a hole
in the top of the rectangle, through the hole in the cylinder and
partly through the bottom of the rectangle. The upper part of the rod
may be bent so as to form a handle. The rod must be fastened to the
cylinder in some convenient way.
Make six flat springs similar to the one shown at A, Fig. 2, and mount
them on the inside of the rectangle so that they will correspond in
their vertical positions to the strips of brass on the cylinder. Six
small binding posts mounted on the outside of the box and connected to
these springs serve to make the external connections, and they should
be marked so that they may be easily identified.
A flat spring, ¹⁄₄ in. wide, is made similar to the one shown at B,
Fig. 2. Mount this spring on the inside of the rectangle so it will
mesh with the ends of the nails in the small part of the cylinder.
The action of this spring is to make the cylinder stop at definite
positions. The top of the case should be marked so that the position
of the handle will indicate the position of the cylinder. Stops should
also be provided so that the cylinder case cannot be turned all the way
around.
Miniature Push Buttons
[Illustration]
A very neat and workmanlike push button may be made in the following
manner: Procure an unused tan-shoe eyelet with an opening about ³⁄₁₆
in. in diameter, and at the proper point drill a hole into the board
in which the button is to be set. Force the eyelet in flush, using a
little shellac to hold it in tightly. For the button proper, polish off
and round one end of a piece of brass rod of a diameter that will move
freely up and down in the eyelet. Solder a small piece of sheet brass
across the lower end to keep it from coming out, then adjust and fasten
on the two contact pieces, all as indicated in the sketch. The larger
piece should be quite springy so as to bring the button back each time.
The connections may be made by slipping the wires under the heads of
the two wood screws that hold the contact pieces in place.
As every experimenter knows, it is almost impossible to drill a hole
in the varnished base of an instrument without leaving a raw edge.
Under such circumstances, when it is desired to make an opening for
conducting cords, and the like, simply drill a hole with an ordinary
drill and then set in a small shoe eyelet, which immediately presents a
very finished appearance.
* * * * *
¶Vaseline, with a little powdered gum camphor added and heated over a
slow fire, makes an excellent rust preventive for tools.
A Quickly Made Toy Electric Motor
[Illustration: The Motor is Constructed of Pieces of Tin, a Nail, and
Some Wood Blocks]
The illustration shows a small electric motor of such simple
construction that it can be easily made from odds and ends to be found
in any amateur workshop. Cut six strips, ¹⁄₂ in. wide and 3¹⁄₂ in.
long, from an old tin can, and bend them together into a U-shape. This
forms the magnet A. The outside piece should be a trifle longer than
the others so that its ends can be turned over the other ends to keep
them all in place. Screw this down on a small wood base. At one side of
the wood base, fix an upright, B, and on top, a light wood bracket, C,
to take the upper bearing of the motor. The shaft D is simply a wire
nail with the head filed off and filed to a point. Drive it through a
1¹⁄₂-in. length of the same kind of material as used for the magnet.
This forms the rotating armature E.
Make a slight indentation with a center punch, or strong nail, exactly
in the center of the base portion of the magnet to take the lower end
of the shaft. For the upper bearing file the end of a brass screw off
flat and make a similar indentation with a center punch, or by a few
turns of a small drill. This screw should be adjusted in the bracket
until the shaft rotates freely with the armature just clearing the tips
of the magnet. Wind about 40 turns of fairly thin cotton-covered copper
wire--No. 24 or 36 gauge is suitable--around each limb of the magnet,
first covering the latter with paper, to prevent the possibility of
short-circuiting. The windings should be in opposite directions so that
the connecting piece of the wire from one coil to the other passes
across diagonally as shown in the illustration.
The brush F is formed by doubling up one of the free ends of the
windings after removing the cotton covering and fixing it firmly with
two screws to the side of the upright. After attaching, it should be
bent until the outer end bears lightly on the shaft. Remove the shaft
and at the point where the brush touched, file two flat surfaces on
opposite sides of the nail in a direction at right angles to the
longitudinal center line of the armature. On replacing the shaft the
brush should be adjusted so that it makes contact twice in a revolution
and remains clear at the flat portions. Connect up to a battery, one
wire to the screw at the top of the motor and the other end to the open
end of the windings. Give the armature a start and it will run at a
terrific speed.--Contributed by Morris G. Miller, New Rochelle, N. Y.
Gauge for Woodwork
[Illustration]
A convenient gauge can be quickly made by using a block of wood and an
ordinary nail, or several nails for different widths can be placed in
one block. Drive the nails straight into the block until the distance
between the head and block is the required distance to be gauged. The
rim of the nail head makes the mark as the block is drawn over the wood
surface--Contributed by E. P. Haldeman, Balboa, Canal Zone.
[Illustration: A Homemade Ammeter
BY JOHN D. ADAMS]
Where a high degree of accuracy is neither desired nor necessary, a
very satisfactory ammeter may be made at the cost of a few cents, and
without using hairsprings, permanent magnets, or other articles usually
not at hand.
The actuating device consists of a small coil of coarse, insulated
wire, with a bundle of soft-iron wires for a core, which attracts a
curved, soft-iron, wedge-shaped armature. The moving system is so
balanced that the armature will hang as illustrated when no current
is passing. On account of its shape, the higher the armature rises,
the more iron it presents to the influence of the magnet, and, on the
other hand, the greater will be the effect of gravity. The advantage of
this type of control is the elimination of the irregular readings of
the scale, due to the law of inverse squares, that usually follow when
any method depending upon a variable distance is used. Further, the
readings can be had as desired by altering the taper of the armature,
its thickness, or its distance from the magnet, and also by adding a
small weight of nonmagnetic material at the bottom. As most commercial
circuits supply alternating current, the friction of the bearings
does not affect the readings, since the alternations set up a decided
vibration in the entire moving system, thus eliminating static friction.
[Illustration: A Very Satisfactory Ammeter for Use Where Accuracy is
Not Desired or Necessary]
In view of the variations above referred to, it will be evident that
it is not very essential of what dimensions the apparatus is made.
The instrument that I use has a base measuring 2¹⁄₂ in. by 5 in. The
coil is built on a tube of glued paper, and contains about 15 ft. of
No. 16 gauge wire. The terminals consist of the brass bolts taken from
discarded dry cells. A steel sewing needle serves as a shaft, and a
piece of wire for the pointer. The various joints are made with soft
solder, and suitable stops are provided to keep the armature from
shifting laterally. In calibrating, a blank scale should be glued in
position and as many 55-watt lamps as possible arranged so that they
can be placed in the circuit, one at a time. On a 110-volt line, each
lamp added will mark a half-ampere point. If a sufficient number of
lamps to carry the scale high enough cannot be secured temporarily,
a resistance of some 20 or 30 ohms should be placed in the circuit
without any lamps. Note the reading in amperes on the scale thus far
constructed, and then begin adding the lamps again, making a mark on
the scale as each lamp is added. In this manner a scale may be built up
sufficiently accurate for all practical purposes.
If two identical coils are made in place of one, the additional coil
can be placed in parallel with the instrument as a shunt, thus doubling
its capacity and making it necessary, of course, to multiply all
readings by two.
Footstool
[Illustration: Footstool in Mission Finish with a Leather Top]
The material necessary for the footstool shown in the illustration is
as follows:
2 end pieces, 1 by 10 by 15 in.
3 cross braces, 1 by 4 by 12 in.
2 end braces, ⁷⁄₈ by 4 by 8 in.
1 top board, ¹⁄₂ by 10 by 14 in.
1 piece of leather, 11 by 16 in.
Round-head wood screws and nails.
The two end pieces should be marked to a suitable pattern, and may be
cut out with a scroll or coping saw, or, if these are not available,
with a keyhole saw. The center opening should first be bored at one
end and then cut out with the saw. The three long braces should be
accurately squared and finished at the ends; the rigidity of the stool
depending on this work. The seat consists of a box form with the open
side down. The top is a ¹⁄₂-in. board, 8 in. wide by 12 in. long; the
sides are formed by two of the long braces, and the ends are the short
braces. This box is securely put together with nails, and then screwed
in position with round-head wood screws so as to be flush with the
top edge of the end pieces. The lower brace is secured in place with
screws. In putting on the leather top, ¹⁄₂ in. should be turned under
at each end, and 1¹⁄₂ in. brought down on each side. This will provide
sufficient looseness to pad the seat properly. Large round-headed brass
nails can be used, producing a neat appearance. The stool is then ready
for a suitable stain or finish.--Contributed by Stanley B. Furbeck.
Stopper for a Bunghole
While we were filling our barrels at the cider mill it was discovered
that one barrel had no stopper. This did not bother the cider-mill
man, who took up a sound apple of about the dimensions or diameter of
the bunghole and squeezed it in, tight as a cork, then shaved it off
flush with the barrel staves. We started Home and rolled it around a
great deal with the other barrels, yet it held as tightly as any wood
stopper.--Contributed by A. A. Kelly, Frazer, Pa.
* * * * *
¶An open umbrella placed on the floor upside down makes an excellent
receptacle for catching dirt and plastering when installing electric
fixtures.
A Woven-Reed Footstool
BY CHARLES M. MILLER
[The various materials referred to in this article by number or size
were described in detail in an article on “A Reed Basket,” in the Boy
Mechanic, Book 2, page 257.]
Reed furniture has become very popular within the last few years, and
the newer designs and methods have been so attractive as to place this
constructive effort among the handicraft series of modern art. It is
possible so to analyze, simplify, and illustrate this work as to make
it feasible for amateurs, and at the same time there are possibilities
which involve problems that may try the ability of the skilled workman.
In other words, there are possibilities of progress in this kind
of furniture making. There are places where careful weaving is the
principal aim; again particular attention will be given to corners, or,
perhaps, a nicety of modeling will be found necessary to bring out the
proper curves involved.
Each piece of reed furniture has a framework, usually of dowels, but it
may also be made of boards in such models as small tables, dressers,
bedsteads, chests, etc. The board construction is more often covered
with flat reed. In footstools there are both kinds of framework.
The illustrations show the same parts marked with the same letters
throughout the series of sketches.
[Illustration: The Framework of the Stool is Made of Large Dowels, Then
Covered with Windings of Reed and a Woven Reed Top and Apron]
The framework of the stool is shown in Fig. 1, in which the rails
and posts are made of dowels, ³⁄₄ in. in diameter, and the braces of
dowels, ⁵⁄₈ in. in diameter. It will be noticed that the posts extend
to the top of the frame for strength in this manner of construction.
If the rails rested on top of the post S, the nails would have to be
driven into the end grain of the wood, which makes the strength depend
entirely on the holding power of the nail in this position, as there
is no binding of the upper part to the posts in the weaving. With the
post extending to the top, the nail passes through the upper part of
the post and into the end grain of the rails, and the rails are bound
together horizontally by the weaving.
The material for the frame consists of the following dowel stock:
two pieces for rails, ³⁄₄ in. by 14 in. long; two pieces for rails,
³⁄₄ in. by 9 in. long; four posts, ³⁄₄ in. by 7 in. long, and two
braces, ⁵⁄₈ in. by 17 in. long. These pieces are shown in Fig. 2. If
notches are cut with a small saw, a coping saw preferred, in the ends
of each rail and in the braces, as shown in Fig. 3, they will fit to
the posts better and make a stronger joint. While different makers
use a finishing nail; a barbed or corrugated, nail; or a cemented, or
glue-coated, nail, I find the best to be an ordinary 4-penny nail,
which answers the purpose well. Do not drive the nail through the posts
without first drilling a hole with a ¹⁄₁₆-in. drill. A small hand or
breast drill will be needed for this work.
Before nailing the frame together, the holes for the spokes in weaving
should be drilled in the rails. The spokes may be No. 4 and the weavers
No. 3 reed. The No. 4 reed requires a ¹⁄₈-in. hole. The hole for the
top and end side spokes may be combined, as shown in Fig. 4. The dotted
lines show the vertical and horizontal diameters, and E the outside
and F the inside of the rail, one hole being represented as sawed in
two. The spokes for the top extend down and out at the ends, and each
may be of one piece, 32 in. long. As there are no spokes at the top
extending to the side pieces, short spokes must be inserted at the
right time for the side weaving. The location of the holes in the side
rails is shown in Fig. 2. The holes in the side rails may be drilled
straight in the wood.
The pieces may now be nailed together to form the frame, as shown in
Fig. 1. If the top of the side rails A are set about ¹⁄₁₆ in. below the
tops of the posts, the weaving will be almost level, as the winding
reed is thinner than the round reed. The braces D are halved at the
center, on a slant, to bring their upper surfaces on a level when they
are in place. The length of 17 in., as given in the material list, is
not accurate, as sufficient length is given to allow the ends to be
cut, in fitting them in place after the frame is assembled. The posts
should stand vertical and square. Try the braces before nailing them in
place, to see that they do not draw the frame out of shape.
The first operation in weaving is to cover the tops of the four posts,
which is started as shown in Fig. 5. A short piece of winding reed, G,
is first tacked in place. A round reed can be split if one is careful,
in case winding reed cannot be obtained. Tacks used by shoemakers are
just the thing for fastening these weavings in place. After fastening
the weaving G in place, another, H, is put on in an opposite direction,
whereupon J is fastened on the same as G, and so on, until the post is
covered, as shown in Fig. 6. Perhaps a better way to cover the posts
would be to tack all eight pieces on the post part C, and then weave
them down together. It may not be necessary to tack them all on the
rails.
After the corners are all covered, the end rails B are wound with the
winding reed, the start being shown in Fig. 7, where the frame is
shown in an inverted position. The reed is tacked, at K, to the side
rail, and whenever the winding comes to a hole, a pencil mark is made
to locate the hole later. This mark is shown at L. When the two end
rails are wound, push a bodkin, or other steel point, in between the
windings where the marks are located, to make way for the insertion of
the spokes. It may appear to an observer that the spokes could be put
in before the winding, but the winding cannot be properly done after
the spokes have been inserted, as the windings would separate too much
around them. The hole must be opened up through to the opposite side
of the rail. Single spokes go through the rail, and they are only put
through one end rail at first, as the weaving is much easier with one
end of the spokes free, but, of course, they must be inserted in the
other end before the weaving gets within 2 or 3 in. of that end. An
extra spoke is inserted beside each spoke, as the weaving proceeds and
after a strip has been woven ³⁄₄ in. wide. These short spokes are cut
just long enough to fit in between the end rails. The weaving is done
with a single weaver, and it is passed over and under double spokes as
if they were one. When the weaver comes to the side rail, it is wound
twice around the rail, to take up the space for the two strands across.
If the weaver does not go twice around the side rails each time, either
the weaving will take a curve or the side winding will be loose. The
starting of the weaving is shown in Fig. 8, where the extra spokes are
inserted along the side of each spoke that runs through the end rails.
After the spokes have been inserted in the opposite end rail and the
weaving in the top completed, the braces and posts should be wound.
Where the braces D connect to the posts C, three strips of the winding
reed are passed around the post and tacked on both sides of the braces,
as shown at M, Fig. 9. Where the braces cross, the winding passes
around both pieces for a short distance, as shown at N. It is quite
appropriate to use the brass caps O on this model, but on many stools
their use has been discontinued and the winding continues down to
within ¹⁄₈ in. of the bottom of the post. In case the brass cap cannot
be obtained, the winding may be used also on this model.
[Illustration: FIG. 1
FIG. 2
FIG. 3
FIG. 5
FIG. 6
FIG. 4
FIG. 7
FIG. 8
FIG. 9
Details of the Dowel Pieces, Showing Dimensions for Drilling the Holes
to Admit the Spokes of Reed, Manner of Building the Framework, and How
the Top is Woven]
The side weaving is called the apron, and in this case the pairing
weave is used. The short spokes will have to be inserted in the under
side of the side rails, and the extra spokes are added after the
weaving is started and a small strip woven. The pairing weave is shown
in Figs. 10, 11, and 12. The two weavers are represented by the letters
P and Q. The weaver P passes back of spoke T and out between T and U.
The weaver Q is then used in the same manner, and so on, around the
stool. When the post is approached the weaver that comes out between
the last spoke and the post is passed around the post and in behind
the next spoke on the other side. It will be seen in the pairing weave
that the weaver behind is always thrown over the other weaver. This
gives the appearance of a rope twist to the weaving, and also cinches
it to the spokes and prevents slipping. Always pass the one weaver
around the post twice to take up the space for the one that cuts across
the corner. The weaving of the sides or apron is done with the object
turned upside down, where it is in a good position for finishing off,
which is sometimes called breaking down.
If the weaving has been carried far enough, the extra spokes are
cut off even with the weaving, and the breaking down may be done as
follows: The spoke R, Fig. 13, is shown turned down back of the spoke
S, and S back of T and out. The spoke R, as shown in Fig. 14, is back
of S, in front of T, back of U, and out between U and V, but as R is
brought out, the spoke T is brought down back and parallel with R.
Likewise the spoke S passes back of V, and U is brought down with it.
The spoke T is brought back of W and V is brought down back of it. The
short end of R is inserted under the roll, between the roll and the
weaving, and is left extending on the inside. If it is too long, it
can be cut off close to the inside of the weaving. In Fig. 15, all the
short ends are shown brought through to the back as far as the weaving
is illustrated. At the corners, the posts are used as spokes. To finish
the roll, the spokes will have to be inserted through the roll, to
correspond with the rest of it; hence, the beginning of the roll should
be left loose, as in Fig. 13.
[Illustration: FIG. 10
FIG. 11
FIG. 15
FIG. 12
FIG. 13
FIG. 14
The Weaving of the Apron is Done in the Same Manner as in Making a
Basket, with the Break Down to Form the Edge]
In weaving, the weavers should be kept wet, but not the spokes. Do not
put the reed in water and leave it for any length of time, as it will
become discolored. About 15 minutes will be sufficient to make the reed
pliable, then it is best to have a sponge and bucket of water at hand,
to dampen long weavers frequently by drawing the reed across the wet
sponge. Besides being more workable, the wet reed, held in place until
dry, stays curved in the form woven much better. Some workmen leave the
reed in water for a long time and depend on bleaching to whiten it, but
so much of the bleached work looks like a poor job of painting that
it is much better to keep it white from the start. In case bleaching
is found necessary, a little chloride of lime in water makes a good
bleacher. Avoid making the solution too strong. It should be put on
with a brush, so as to get it into the interstices of the weaving,
whereupon the work is placed in the sunshine to dry.
Any kind of reed used will have some of the small hairlike fibers
sticking out after the weaving is complete, and this should be singed
off with a gas flame. A blowtorch is good for this purpose. Be careful
not to scorch the weaving.
A Homemade Ellipsograph
BY J. A. SHELLY
The instrument illustrated was designed to take the place of the two
nails and a piece of string for drawing ellipses of different sizes. It
is made of hard wood, preferably maple or beech, and consists of a bar
with one fixed and one sliding head, the latter having a wedge clamp to
hold it at any point desired on the bar.
In the ends of the heads are driven two coarse needles that have been
broken off about ⁵⁄₈ in. from the eye end. These ends should be placed
¹⁄₈ in. from the inside of each head and the same distance from the
bottom, and driven in until the eyes are each ¹⁄₈ in. from the surface.
A piece of linen thread is run through the eye of the needle that is
in the end of the sliding head and knotted to prevent its pulling out,
and the free end is run through the needle eye on the fixed head. The
thumb tack in the fixed head is to secure the free end of the thread.
The tack is driven in at an angle so that one edge sticks up enough to
allow the thread to be pulled under it.
[Illustration: The Sliding Head can be Set so That Any Size Ellipse may
be Drawn within the Scope of the Instrument]
To operate the ellipsograph lay out the length of the major axis on a
center line, then bisect the distance between these points and erect
a perpendicular. On this line lay off half the minor axis, measuring
from the center line; then from this point locate the foci by setting
the dividers to half the major axis and scribing arcs of circles to cut
the center line. Set the heads of the instrument so that the projecting
needle ends will be the same distance apart as the foci, and clamp the
sliding head with the wedge. Set the instrument so that the needle
eyes will be exactly over the points where the foci are on the center
line. A pencil, with a little groove filed ¹⁄₈ in. from the point, for
the thread to run in, is set to half the minor axis and the thread is
pulled taut and secured by the thumb tack. The pencil should be held
perfectly perpendicular while scribing the line. The instrument must be
reversed to draw the other half of the ellipse.