The Boy Mechanic Part 69

opening, which may then be cut out easily with a knife and straight edge.

The black paper from plate boxes and film rolls is excellent for making masks. It should be cut up in pieces 3-1/4 by 4 in. and kept ready for use at any time.

** Relieving the Weight of a Talking Machine Reproducer [245]

Too loud reproduction from a record, the scratching noise sometimes heard and the forcing of the needle into a soft record, because the extension arm and reproducer are too heavy, can be remedied in the following manner: Attach a small ring to the under side of the horn and use a rubber band to lift the extending arm slightly.

--Contributed by W. A. Jaquythe, Richmond, Cal.

** How to Make a Thermometer Back in Etched Copper [246]

Etching copper is not a very difficult process. Secure a sheet of No. 16 gauge copper of the width and length

[Ill.u.s.tration: Copper Thermometer Holder]

wanted for the back of the thermometer. In the design shown the extreme width is 3-1/2 in. and the extreme length 7 in.

Draw a design. The one shown is merely suggestive. The worker may change the outline or proportions as desired. The decoration, too, may be changed. The essential thing is to keep a s.p.a.ce upon which to place the thermometer. This design is in what is known as two-part symmetry. A line is drawn down the paper and one-half of the outline and decoration worked out. This done, the paper is folded along the center line, a piece of carbon paper is inserted between the folds and the design transferred on the inner surfaces by tracing with a pencil over the half of the outline previously drawn. Trace the design and outline upon the metal, using the carbon paper.

Cut out the outline with metal shears and file the edges smooth.

With a small brush and ordinary asphaltum or black varnish, paint the design, the margin and the entire back of the metal. When this coat has dried put on a second and then a third. The asphaltum is to keep the acid into which the metal is to be immersed later from eating any part of the metal but the background. Two coats or more are needed to withstand the action of the acid.

The acid bath is composed of nitric acid and water, about half and half, or, possibly, a little less acid than water, the mixture being made by pouring the acid into the water, not the water into the acid, which is dangerous. Keep this solution off the hands and clothes, and do not inhale the fumes.

Put the asphalt-coated metal in the bath and allow it to remain for four or five hours, depending upon the thickness of the metal and the strength of the acid. With a stick, or a pair of old tongs, take the metal out of the acid occasionally and examine it to see how deep the acid has eaten it--1/32 in. is about right for the No. 16 gauge.

When etched to the desired depth, remove the piece and with an old knife' sc.r.a.pe off the asphaltum. Finish the cleaning by scrubbing with turpentine and a brush having stiff bristles.

If the metal is first covered with turpentine and then heated over a flame, all the colors of the rainbow will appear on its surface.

These colors fade away in the course of a long time, but they can be easily revived. Another way to get these colors is to heat the metal and then plunge it into the acid bath quickly.

A green finish is obtained by painting the background with an acid stain composed as follows: 1 part ammonia muriate; 3 parts ammonia carbonate; 24 parts water. If one coat does not give the depth of color desired, repeat as many times as is necessary, allowing each coat time to dry before applying the next.

To "fix" this color so that it will not rub off, and to keep the metal from tarnishing, apply a coat of banana oil or lacquer.

Thermometers of suitable size can be bought in either bra.s.s or nickel. They have holes through their top and bottom ends through which metal paper fasteners can be inserted, and these in turn put through holes punched in the copper back.

** To Make an Electric Piano [247]

Make or buy a table, about 3 ft. long and 1 ft. or more wide, and about 2-1/2 ft. high. Nail a board, A, Fig. 1, about 8 in. wide and of the same length as the table, to the table, as shown in the ill.u.s.tration. Paint the table any color desired.

Purchase a dozen or so battery electric bells (they are cheaper if bought by the dozen) and screw them to the board, as in Fig. 2.

Arrange the bells in the scale shown at B, Fig. 2. Bore two holes near the posts of each bell for the wires to pa.s.s through.

b.u.t.tons for the bells may be purchased, but it is cheaper to make them in the following way: Take a piece of

[Ill.u.s.tration: How the Electric Piano is Constructed]

wood and cut it round, about 2-1/2 in. in diameter and 1/4 in.

thick, Fig. 3, and bore two holes, C and D, through it. Then get two posts, about 1 in. long, (battery posts will do) and put them through the holes as in Fig. 4. Cut out a piece of tin, 3/8 in.

wide, punch a hole through it and put in under post E, so that when it is pressed down, it will touch post F. It may be either nailed or screwed down.

Make two holes in the table for each b.u.t.ton and its wires, as at H, Fig. 2. Nail or screw the b.u.t.tons to the table, as shown in Fig. 5, with the wires underneath. The connections are simple: I, Fig. 5, is a wire running from one end of the table to the other end, attached to a post at each end; J is another wire attached in the same way; L is the carbon wire running from the batteries to I; M is the zinc wire running from the batteries to wire J; 0 indicates the batteries; P is a wire running from J to one post of a b.u.t.ton; Q is another wire running from the other post of the b.u.t.ton to one of the posts of the bell; R is a wire running from I to one post of the bell. When the b.u.t.ton S is pressed, the bell will ring. Each b.u.t.ton should be connected with its bell in the same way.

--Contributed by Vincent de Ybarrondo.

** Imitation Arms and Armor - PART III [248]

Maces and battle-axes patterned after and made in imitation of the ancient weapons which were used from the

[Ill.u.s.tration: Ancient Weapons]

fourteenth to the sixteenth century produce fine ornaments for the hall or den, says the English Mechanic. The imitation articles are made of wood, the steel parts represented by tinfoil stuck on with glue and the ornaments carved out with a carving tool.

An English mace used about the middle of the fifteenth century is shown in Fig. 1. The entire length of this weapon is about 24 in.; the handle is round with a four-sided sharp spike extending out from the points of six triangular shaped wings. Cut the handle and spike from one piece of wood and glue the wings on at equal distances apart around the base of the spike. The two bands or wings can be made by gluing two pieces of rope around the handle and fastening it with tacks. These rings can be carved out, but they are somewhat difficult to make. After the glue is dry, remove all the surplus that has been pressed out from the joints with the point of a sharp knife blade and then sandpaper the surface of the wood to make it smooth. Secure some tinfoil to cover the parts in imitation of steel. A thin coat of glue is quickly applied to the surface of the wood and the tinfoil laid on evenly so there will be no wrinkles and without making any more seams than is necessary. The entire weapon, handle and all, is to appear as steel.

An engraved iron mace of the fifteenth century is shown in Fig. 2.

This weapon is about 22 in. long, mounted with an eight-sided or octagonal head. It will be easier to make this mace in three pieces, the octagonal head in one piece and the handle in two parts, so that the circular shield shown at the lower end of the handle can be easily placed between the parts. The circular piece or shield can be cut from a piece of wood about 1/4 in. thick. The circle is marked out with a compa.s.s. A hole is made through the center for the dowel of the two handle parts when they are put together. A wood peg about 2 in. long serves as the dowel. A hole is bored in the end of both handle pieces and these holes well coated with glue, the wood peg inserted in one of them, the shield put on in place and handle parts put together and left for the glue to set. The head is fastened on the end of the handle with a dowel in the same manner as putting the handle parts together.

The head must have a pattern sketched upon each side in pencil marks, such as ornamental scrolls, leaves, flowers, etc. These ornaments must be carved out to a depth of about 1/4 in. with a sharp carving tool. If such a tool is not at hand, or the amateur cannot use it well, an excellent subst.i.tute will be found in using a sharp-pointed and red-hot poker, or pieces of heavy wire heated to burn out the pattern to the desired depth. The handle also has a scroll to be engraved. When the whole is finished and cleaned

[Ill.u.s.tration: Battle Axes of the Fourteenth, Fifteenth and Sixteenth Centuries]

Up, it is covered with tinfoil in imitation of steel. The tinfoil should be applied carefully, as before mentioned, and firmly pressed into the engraved parts with the finger tips or thumb.

A French mace used in the sixteenth century is shown in Fig. 3.

This weapon is about 22 in. long and has a wood handle covered with dark red cloth or velvet, the lower part to have a gold or red silk cord wound around it, as shown, the whole handle finished off with small bra.s.s-headed nails. The top has six ornamental carved wings which are cut out, fastened on the handle and covered with tinfoil, as described in Fig. 2.

Figure 4 shows a Morning Star which is about 26 in. long. The spiked ball and the four-sided and sharp-pointed spike are of steel. The ball may be made of clay or wood and covered with tinfoil. The spikes are cut out of wood, sharp-pointed and cone-shaped, the base having a brad to stick into the ball. The wood spikes are also covered with tinfoil. The handle is of steel imitation, covered in the middle with red cloth or velvet and studded with large-headed steel nails.

A war hammer of the fifteenth century is shown in Fig. 5. Its length is about 3 ft. The lower half of the handle is wood.

covered with red velvet, with a golden or yellow cord wound spirally over the cloth. The upper half of the handle is steel, also, the hammer and spike. The entire handle should be made of one piece, then the hammer put on the base of the spike. The spike made with a peg in its lower end and well glued, can be firmly placed in position by the peg fitting in a hole made for its reception in the top of the handle. Finish up the steel parts with tinfoil.

The following described weapons can be constructed of the same materials and built up in the same way as described in the foregoing articles: A horseman's short-handled battle-axe, used at the end of the fifteenth century, is shown in Fig. 6. The handle is of wood and the axe in imitation steel. Figure 7 shows an English horseman's battle-axe used at the beginning of the reign of Queen Elizabeth. The handle and axe both are to be shown in steel. A German foot soldier's poleaxe used, at the end of the fourteenth century is shown in Fig. 8. The handle is made of dark wood and the axe covered with tinfoil. Figure 9 shows an English foot soldier's jedburgh axe of the sixteenth century. The handle is of wood, studded with large bra.s.s or steel nails. The axe is shown in steel. All of these axes are about the same length.

** Playing Baseball with a Pocket Knife [250]

An interesting game of baseball can be played by two persons with a common pocket knife on a rainy day or in

[Ill.u.s.tration: Positions of the Knife Indicate the Plays]