The Boy Mechanic Part 42

the clothes closet. Figure 1 shows the construction of the bottom to permit the dirt to fall through. Two boards, 9 in. wide and about 3 ft. long, with six part.i.tions between, as shown, will make pockets about 6 in. long. The width of the pockets at the bottom is 2 in. and at the top 5 in.

--Contributed by Guy H. Harvey, Mill Valley, Cal.

** How to Waterproof Canvas [146]

The method used by the British navy yards for waterproofing and painting canvas so it will not become stiff and cracked is as follows: One ounce of yellow soap and 1/2 pt. of hot water are mixed with every 7 lb. of paint to be used. The mixture is applied to the canvas with a brush. This is allowed to dry for two days and then a coat of the same paint, without the soap, is laid on.

When this last coat is dry the canvas may be painted any color desired. After three days of drying the canvas may be folded up without sticking together, and is, of course, waterproof. Canvas waterproofed in this manner makes an excellent covering for portable canoes and canvas boats. The color mixture for the soap and second application is made from 1 lb. of lampblack and 6 lb.

of yellow ocher, both in oil; the finish coat may be any color desired. When no paint is to be used on the canvas it may be waterproofed with a mixture made from soft soap dissolved in hot water, and a solution of iron sulphate added. Iron sulphate, or ferrous sulphate, is the green vitriol. The vitriol combines with the potash of the soap, and the iron oxide is precipitated with the fatty acid as insoluble iron soap. This precipitate is then washed, dried and mixed with linseed oil.

** Building a House in a Tree Top [146]

The accompanying photograph shows a small house built in a tree top 20 ft. from the ground. The house is

[Ill.u.s.tration: Lofty Sentry Box for Guarding Watermelon Patch]

5 ft. wide, 5 ft. 1 in. long, and 6 ft. 6 in. high. A small platform, 2 ft. wide, is built on the front. Three windows are provided, one for each side, and a door in front. The entrance is made through a trap door in the floor of the house. This house was constructed by a boy 14 years old and made for the purpose of watching over a melon patch.

--Contributed by Mack Wilson, Columbus, O.

** How to Make a Lamp Stand and Shade [147]

A library light stand of pleasing design and easy construction is made as follows: Square up a piece of white oak so that it shall have a width and thickness of 1-3/4 in. with a length of 13 in.

Square up two pieces of the same kind of material to the same width and thickness, but with a length of 12 in. each. Square up two pieces to a width and length of 3 in. each with a thickness of 1-1/8 in.

If a planing mill is near, time and patience will be saved by ordering one piece 1-3/4 in. square and 40 in. long, two pieces 1-1/8 in. thick and 3 in. square, all planed and sandpapered on all surfaces. The long piece can then be cut at home to the lengths specified above.

The 13-in. piece is for the upright and should have a 1/2-in. hole bored the full length through the center. If the bit is not long enough to reach entirely through, bore from each end, then use a red-hot iron to finish. This hole is for the electric wire or gas pipe if gas is used.

The two pieces for the base are alike except the groove of one is cut from the top and of the other from the under side, as shown.

Shape the under sides first. This can best be done by placing the two pieces in a vise, under sides together, and boring two holes with a 1-in. bit. The center of each hole will be 2-1/2 in. from either end and in the crack between the pieces. The pieces can then be taken out, lines gauged on each side of each, and the wood between the holes removed with turning saw and sc.r.a.per steel.

The width of the grooves must be determined by laying one piece upon the other; a trysquare should be used to square the lines across the pieces, however, gauge for depth, gauging both pieces from their top surfaces. Chisel out the grooves and round off the corners as shown in the sketch, using a 3/4-in. radius.

These parts may be put together and fastened to the upright by means of two long screws from the under side, placed to either side of the 1/2-in. hole. This hole must be continued through the pieces forming the base.

The braces are easiest made by taking the two pieces which were planed to 1-1/8 in. thick and 3 in. square and drawing a diagonal on each. Find the middle of this diagonal by drawing the central portion of the other diagonal; at this point place the spur of the bit and bore a 1-in. hole in each block.

Saw the two blocks apart, sawing

[Ill.u.s.tration: Details of Construction of Library Lamp Stand]

along a diagonal of each. Plane the surfaces on the saw cut smooth and sandpaper the curve made by the bit. Fasten the braces in place by means of roundhead blued screws.

To make a shade such as is shown in the ill.u.s.tration is rather difficult. The shade is made of wood glued up and has art gla.s.s fitted in rabbets cut on the inner edges. Such shades can be purchased ready to attach. The sketch shows one method of attaching. Four small pieces of strap iron are bent to the shape shown and fastened to the four sides of the upright. Electric globes--two, three or four may be attached as shown.

The kind of wood finish for the stand will depend upon the finish on the wooden shade, if shade is purchased. Brown Flemish is obtained by first staining the wood with Flemish water stain diluted by the addition of two parts water to one part stain. When this is dry, sandpaper the "whiskers" which were raised by the water and fill with a medium dark filler. Directions will be found on the filler cans. When the filler has hardened, apply two coats of wax.

The metal shade as shown in the sketch is a "layout" for a copper or bra.s.s shade of a size suitable for this particular lamp. Such shades are frequently made from one piece of sheet metal and designs are pierced in them as suggested in the "layout." This piercing is done by driving the point of a nail through the metal from the under side before the parts are soldered or riveted together. If the parts are to be riveted, enough additional metal must be left on the last panel to allow for a lap. No lap is needed when joints are soldered.

A better way, and one which will permit the use of heavier metal, is to cut each side of the shade separately and fasten them together by riveting a piece of metal over each joint. The shape of this piece can be made so as to accentuate the rivet heads and thus give a pleasing effect.

For art-gla.s.s the metal panels are

[Ill.u.s.tration: The Completed Lamp]

cut out, the gla.s.s is inserted from the under side and held in place by small clips soldered to the frame of the shade. Pleasing effects are obtained by using one kind of metal, as bra.s.s, and reinforcing and riveting with another metal, such as copper.

[Ill.u.s.tration: METAL SHADE--Construction of Shade]

** Illuminating a Watch Dial at Night [149]

This picture shows a watch holder, with a device to receive an ordinary electric pocket lamp and battery. The battery is set in a bracket under which a reflector extends downward to throw the light on the dial of the watch and to protect the eyes from the direct light. The entire stand and bracket are made from sheet metal. The base is formed to make a tray to hold pins and collar b.u.t.tons. It is not necessary to seek in the darkness for a push b.u.t.ton or switch, as in ordinary devices, but a light pressure with the palm of the hand will make the lamp glow.

[Ill.u.s.tration: Lamp]

** Home-Made Photographic Copying Stand [149]

The difficulties of bad lighting on small articles can be entirely avoided by the use of a suitable support for the camera, the object and the background.

[Ill.u.s.tration: Secures Good Light on Small Objects]

For ill.u.s.trations it is often an advantage to show an object with a perfectly plain background and no deep shadows. When using the stand as ill.u.s.trated this is a very simple matter. Figure 1 shows the side, and Fig. 2 the front view of this stand. The stand is very easily constructed from pipe and pipe fittings. The main pipe of the stand will need to be of proper length to suit the focus of your camera. This can be determined by finding the length from the lens to the object after the bellows are extended to their full length. The arms holding the gla.s.s, as shown in the sketch, should be set at a point about the middle of the main tube. The cross that holds the middle arms should be 3/4 in. one way and 1/2 in.

the other. This will allow for adjustment of the gla.s.s table. A small set screw provided in the back of this cross will hold the table in any position desired. The pipes and other connections are all 1/2-in. and the lengths of the pipes are made suitable for the size of the camera. When a small object is to be photographed it is placed upon the gla.s.s table and the background fastened to the board. In this manner small objects can be photographed without any deep shadow on one side. The bottom cross and ells should be corked so as to prevent any slipping and damage to the floor.

** Home-Made Pocket Lamp [149]

A simple and safe pocket lamp that will last for about 6 months without extra expense can be made at home for a few cents.

Have your druggist take a strong vial of clear gla.s.s, or a pill bottle with screw or cork top and put into it a piece of phosphorus about the size of a pea and fill the bottle one-third full of pure olive oil that has been heated for 15 minutes--but not boiled. Cork tightly and the result will be a luminous light in the upper portion of the bottle. If the light becomes dim, uncork and recork again. The lamp will retain its brilliancy for about 6 months. This makes a perfectly safe lamp to carry. These lamps are used by watchmen of powder magazines. Care should be exercised in handling the phosphorus, as it is very poisonous.

** How to Make a Tangent Galvanometer [150]

Secure a piece of wood 1/2 in. thick and cut out a ring with an outside diameter of 10-1/2 in. and an inside diameter of 9 in. and glue to each side two other rings 1/4 in. thick with the same inside diameter as the first ring and 11 in. outside diameter, thus forming a 1/4-in. channel in the circ.u.mference of the ring.

If a lathe is at hand this ring can be made from a solid piece and the channel turned out. Cut another circular piece 11 in. in diameter for a base. Make a hole in the center of this piece 1 in.

wide and 6-5/16 in. long, into which the ring first made should fit so that its inner surface is just even with the upper surface of the baseboard. The ring is held upright in the hole by a small strip screwed to the base as shown. All screws and brads that are used must be of bra.s.s. The cutting of these circular pieces is not so difficult if a band saw driven by power is used. They can be cut by means of a key-hole saw if a band saw is not accessible.