The Boy Mechanic Part 80

The rubbing of the hot iron over this cloth absorbs just enough of the wax to make the iron work smoothly. When the supply of wax is exhausted, it can be easily renewed.

--Contributed by A. A. Houghton, Northville, Mich.

** Making Coins Stick to Wood by Vacuum [287]

Take a quarter and place it flat against a vertical surface of wood such

[Ill.u.s.tration: Floating Coin]

as the side of a bookcase, door facing or door panel, and strike it hard with a downward sliding motion, pressing it against the wood. Take the hand away and the coin will remain on the woodwork.

The striking and pressure expel the air between the quarter and the wood, thus forming a vacuum sufficient to hold the coin.

** Simple and Safe Method for Sending Coins by Mail [287]

Sending coins by mail is not as a rule advisable, but sometimes it

[Ill.u.s.tration: How the Paper is Folded]

becomes necessary, and usually a regular coin mailer is not available. A very simple and secure way to wrap a coin or coins for mailing is as follows: Procure a piece of heavy paper, nearly as wide as the envelope is long, and about 12 in. long. Fold on the dotted lines shown by A and B in the sketch, and slip the coin in the pocket thus formed. Fold together on lines C, D, E and F, making the last two folds wide enough to fit snugly in the envelope. This method holds the coin in the center of the envelope where it cannot work around and cut through the edges.

--Contributed by O. J. Thompson, Petersburg, Ill.

** Mounting Photographs in Plaster Plaques [287]

Purchase a few pounds of plaster of paris from your local druggist and select a dish of the desired shape in which to make your cast.

The size of the dish will depend on the size of the print to be mounted. Select the print you wish to mount, those on matte paper will work best, and after wetting, place it face down in the dish, press into place and remove all drops of water with a soft cloth.

Be sure and have the print in the center of the dish. Earthen dishes will be found more convenient, although tin ones can be used with good success, says Photographic Times.

Mix same of the plaster in clear water so it will be a little thick. Enough plaster should. be mixed to cover the bottom of the dish about 1/2 in. thick. Pour the plaster into the dish over the print and allow to stand until it becomes quite hard. The cast can then be removed and the print should be fast to it. If the print or plaster is inclined to stick, take a knife and gently pry around the edges and it can be removed without breaking.

Prints of any size may be used by having the mold or dish large enough to leave a good margin. This is a very important point as it is the margin that adds richness to all prints. Platinum or blueprint papers work well, but any kind that will not stick may be used. After the plaster has thoroughly dried, any tint may be worked on the margin by the use of water colors; if blueprints are used, it is best to leave a plain white margin.

** Iron Rest for an Ironing Board [288]

A flatiron rest can be made on an ironing-board by driving a number of large tacks into one end of the board. The tacks should be about 1 in. apart and driven in only part way, leaving about 1/4 in. remaining above the surface of the board. The hot iron will not burn the wood and it cannot slip off the tacks. This iron rest is always with the board and ready when wanted. --Contributed by Beatrice Oliver, New York, N. Y.

[Ill.u.s.tration: Iron Rest]

** Instantaneous Crystallization [288]

Dissolve 150 parts of hyposulphite of soda in 15 parts of water and pour the solution slowly into a test tube which has been warmed in boiling water, filling the same about onehalf full.

Dissolve in another gla.s.s 100 parts of acetate of soda in 15 parts of boiling water. Pour this solution slowly on top of the first in such a way that it forms an upper layer, without mixing the solutions. The two solutions are then covered over with a thin layer of boiling water and allowed to cool.

[Ill.u.s.tration: Crystallization]

Lower into the test tube a wire, at the extremity of which is fixed a small crystal of hyposulphite of soda. The crystal traverses the solution of acetate without causing trouble, but crystallization will immediately set in as soon as it touches the lower hyposulphite of soda solution, as shown at the left in the sketch.

When the hyposulphite of soda solution becomes crystallized, lower in the upper solution a crystal of acetate of soda suspended by another wire, as shown in the right of the sketch, and this will crystallize the same as the other solution.

** Decoloration of Flowers by Fumes of Sulphur [288]

Dissolve some sulphur in a small dish which will inflame by contact with air thus forming sulphuric acid fumes. Cover the dish with a conical chimney made of tin and expose to the upper opening the flowers that are to be decolored. The action is very rapid and in a short time myrtle, violets, bell flowers, roses, etc., will be rendered perfectly white.

[Ill.u.s.tration: Flowers]

** How to Preserve Egg Sh.e.l.ls [288]

Many naturalists experience difficulty in preserving valuable egg sh.e.l.ls. One of the most effective ways of preserving them is as follows: After the egg is blown, melt common beeswax and force it into the sh.e.l.l with a discarded fountain pen filler. Set in a cool place until the wax hardens. The most delicate sh.e.l.ls treated in this manner can be handled without fear of breaking, and the transparency of the wax will not alter the color, shading, or delicate tints of the egg.

--Contributed by L. L. Shabino, Millstown, South Dakota.

** Homemade Phonograph [289]

Make a box large enough to hold four dry cells and use it as a base to mount the motor on and to support the revolving cylinder.

Anyone of the various battery motors may be used to supply the power. The support for the cylinder is first made and located on the cover of the box in such a position that it will give ample room for the motor. The motor base and the support are fastened by screws turned up through the cover or top of the box. The location of these parts is shown in Fig. 1.

The core for holding the cylindrical wax records is 4-1/2 in. long and made of wood, turned a little tapering, the diameter at the small or outer end being 1-5/8 in., and at the larger end, 1-7/8 in. A wood wheel with a V-shaped groove on its edge is nailed to the larger end of the cylinder. The hole in the core is fitted with a bra.s.s tube, driven in tightly to serve as a bearing. A rod that will fit the bra.s.s tube, not too tightly, but which will not wobble loose, is threaded and turned into the upper end of the support. The core with its attached driving wheel is shown in Fig.

3. The dotted lines show the bra.s.s bearing and rod axle. The end of the axle should be provided with a thread over which a washer and nut are placed, to keep the core from coming off in turning.

The sound box, Fig. 2, is about 2-1/2 in. in diameter and 1 in.

thick, made of heavy tin. The diaphragm, which should be of thin ferrotype tin, should be soldered to the box. The needle is made of a piece of sewing needle, about 1/8s in. long, and soldered to the center of the diaphragm. The first point should be ground blunt, as shown in the sketch. When soldering these parts together, take care to have the diaphragm lie perfectly flat and not made warping by any pressure applied while the solder is cooling.

The tin horn can be easily made, attached to the sound box with a piece of rubber hose and held so it will swing the length of the record by a rod attached to the top of the box, as shown.

The motor can be controlled by a small three or four-point battery rheostat.

[Ill.u.s.tration: Phonograph and Construction of Parts]

--Contributed by Herbert Hahn, Chicago, Ill.

** A Subst.i.tute for a Compa.s.s [289]

An easy way to make a pencil compa.s.s when one is not at hand, is to take a knife with two blades at one end, open one to the full extent and the other only halfway. Stick the point end of the fully open blade into the side of a lead pencil and use the half-open blade as the center leg of the compa.s.s. Turn with the knife handle to make the circle.

--Contributed by E. E. Gold. Jr. Victor, Colo.