The Boy Mechanic Part 83

A very pretty trick, that can be worked in your own parlor, will produce as much sensation as a fake "medium." In all appearance, a violin, mandolin or guitar, placed on a table, will begin to produce music simply through stamping the foot and a few pa.s.ses of the hand. The music will not sound natural, but weird and distant.

The trick is done by placing the end of a small stick on a music box in the bas.e.m.e.nt of the house and allowing the other end to pa.s.s up through the floor and table top so it will project about 1/16 in. The stick may be placed by the side of, behind or through the center of a table leg. Be careful not to have any obstruction in the way of the stick. The instrument is placed sideways on the protruding end of the stick. The "fake" work of invoking the "spirit" is performed and ended by stamping the foot, which signals the operator in the bas.e.m.e.nt to start the machine, and the violin seemingly produces music without anyone touching it.

So impressive are the results, that many people really think the spirits of the departed are playing the violin with unseen hands.

The music is transmitted through the stick from the music box to the violin.

[Ill.u.s.tration: The Music Produced by the Phonograph is Transmitted to the Viohn on the Second Floor by the Aid of a Long Stick]

** Sizing a Threaded Hole [295]

It sometimes becomes necessary to transfer the size of a threaded hole from some out-of-the-way place to the shop in order to make a piece to fit it. With proper tools this is easy; without them, it might be difficult. One thing is always at hand and that is wood.

Whittle a stick tapering until it starts in the hole. Then turn it into the hole and a fair thread will be made on the wood. The stick can be carried in the pocket without risk of changing the size, as would be the case with ordinary calipers.

** Leaded-Gla.s.s Fire Screen [295]

The main frame of the fire screen shown in Fig. 1 is made from two pieces of 1/2-in. square bar iron. The longest piece, which should be about 5-1/2 ft. long, is bent square so as to form two uprights, each 28 in. long and measuring 26 in. across the top.

The bottom crosspiece can be either riveted or welded to the uprights. Two pairs of feet, each 6 in. long and spread about 8 in. apart, are shaped as shown in Fig. 2. These are welded to the lower end of the uprights.

The ornamental scrollwork on the frame is simple and effective, and is easy to construct, says Work, London. The scrolls are attached to the frame by means of 3/16-in. round-head machine screws. The leaf ornament at the

[Ill.u.s.tration: Completed Fire Screen and Parts]

termination of the scroll is shaped and embossed as shown in Fig.

3. The metal used for the scrolls is 3/16 in. thick by 1/2 in.

wide. The leaf ornament is formed by turning over the end of a piece of metal and working it together at a welding heat, and then shaping out the leaf with' a chisel and files, after which they are embossed with a ballpeen hammer.

The center is made from colored gla.s.s of special make for leaded work. The design is formed in the lead, of which a cross section is shown in Fig. 4. Use care to give the lead a symmetrical outline. The design should be drawn full size on a large sheet of heavy paper and the s.p.a.ces to be occupied by the lead cut out so as to leave the exact size and shape of each piece of paper the same as wanted for each piece of gla.s.s. These are used as patterns in marking the gla.s.s for cutting. The gla.s.s is cut the same as ordinary window gla.s.s. The gla.s.s, lead, border and special flux can be purchased from an art gla.s.s shop.

After the gla.s.s is cut, the work of putting the pieces together with the lead between them is begun. Secure a board as wide as the screen--several narrow boards put together will do and begin by placing one vertical side border, A, Fig. 5, and the base border, B, on it as shown. Place the corner piece of gla.s.s, C, in the grooves of the borders, cut a long piece of lead, D, and hold it in place with two or three brads or glazier's points. The piece of lead E is cut and a small tenon joint made as shown in Fig. 6.

While the piece of lead D, Fig. 5, is held by the brads, the piece E can be fitted and soldered. The soldering is done with a hot soldering iron and wire solder, using rosin as a flux, or, better still, special flux purchased for this purpose. After the joints are soldered, the piece of gla.s.s F is put in place and the lead held with brads as before until the cross leads are fitted and soldered. The brads are then removed, the gla.s.s piece as shown by the dotted lines put in, and the leads around it held with brads until the crosspieces are put in and soldered. This method is pursued until the gla.s.s is complete, then the two remaining vertical and top pieces of border are put on and all corners soldered.

The leaded gla.s.s is held in the iron frame by means of eight U-shaped clips, as shown in Fig. 7. A hole is drilled in the frame for the retaining screw, the latter being tapped to the base of the clip. Special screws may be made with ornamental heads, as shown in Fig. 8, and used for securing the side scrolls and clips together.

** A Revolving Teeter Board [297]

[Ill.u.s.tration: Details of Teeter Board ]

The accompanying sketch shows the details of a revolving teeter board for the children's playground that can be constructed in a few hours. Secure a post, not less than 4 in. square and of the length given in the drawing, and round the corners of one end for a ring. This ring can be made of 1-in. strap iron and it should be shrunk on the post. Bore a 3/4-in. hole in the end of the post for the center pin to rest in. Make three washers 3-in. in diameter and 1/4 in. thick and drill 3/4-in. holes through their centers.

Drill and countersink two smaller holes for 2-in. wood screws in each washer. Fasten one of these washers to the top of the post as shown. The post is now ready to be set in the ground. Coa.r.s.e gravel should be packed tightly about it to make it solid.

Concrete is much better if it can be secured.

To make the swivel you will need two 1/4 by 5 by 8-in. plates, rounded at the top as shown, and two wood blocks, A and B, each 3-1/2 by 5 by 10 in. Drill the lower ends of the plates for four 2-1/2-in. lag screws and the upper ends for a 5/8-in. bolt. Fasten the plates to the block B, then drill a 3/4-in. hole as shown and fasten the two remaining washers to the block, one on each side and central with the hole. Bore a 5/8-in. hole lengthwise through the block A for the 5/8-in. rocker bolt. This bolt should be 11-1/2 in. long.

The teeter board is made of a 2 by 12-in. plank about 12 ft. long.

It should be slightly tapered from the center to the ends. Two styles of hand holds are shown, but the one on the left is the one most generally used. The handles are rounded at the ends and are fastened to the board with lag screws or bolts. The block A is fastened to the board with lag screws and should be a working fit between the wo plates where it is held by means of the 5/8-in.

bolt. The center pin is 3/4-in. in diameter and about 9 in. long.

--Contributed by W. H. Dreier, Jr., Camden, N. J.

** Home-Made Pot Covers [297]

Empty thread spools and the tins used as extra inside covers in lard cans are usually thrown away, but these can be put to good use as kettle covers, if they are made up as follows: Saw the spool in half as shown, make a hole in the center of the tin and run a screw or nail through the spool and the tin; then flatten its end on the under side. This will make an excellent cover for a pot.

--Contributed by Maurice Baudier, New Orleans, La.

[Ill.u.s.tration: Pot Covers]

** An Outdoor Gymnasium Part I-The Horizontal Bar [298]

Gymnastic apparatus costs money and needs to be housed, because it will not stand the weather. Gymnasiums are not always available for the average boy who likes exercise and who would like to learn the tricks on horizontal and parallel bars, horse and rings, which all young athletes are taught in regular gymnastic courses.

Any small crowd of boys--even two--having a few simple tools, a will to use them and the small amount of money required to buy the necessary

[Ill.u.s.tration: Adjustable Horizontal Bar

wood, bolts and rope, can make a first cla.s.s gymnasium. If trees are convenient, and some one can swing an axe, the money outlay will be almost nothing. The following plans are for material purchased from a mill squared and cut to length. To subst.i.tute small, straight trees for the squared timbers requires but little changes in the plans.

The most important piece of apparatus in the gymnasium is the horizontal bar. Most gymnasiums have two: one adjustable bar for various exercises and a high bar for gymnastic work. The outdoor gymnasium combines the two. The material required is as follows: 2 pieces of wood, 4 in. square by 9-1/2 ft. long; 4 pieces, 2 by 4 in. by 2 ft. long; 4 pieces, 1 by 7 in. by 6-1/2 ft. long; 4 filler pieces, 3/4 by 3 in. by 3 ft. 9 in. long and 1 piece, 2-1/2 in. square by 5 ft. 7 in. long. This latter piece is for the bar and should be of well seasoned, straight-grained hickory. It makes no difference what kind of wood is used for the other pieces, but it is best to use cedar for the heavy pieces that are set in the ground as it will take years for this wood to rot. Ordinary yellow pine will do very well. The four 7-in. boards should be of some hard wood if possible such as oak, hickory, maple, chestnut or ash. The other material necessary consists of 2 bolts, 1/2 in. in diameter and 7 in. long; 16 screws, 3 in. long; 4 heavy screw eyes with two 1/2-in. shanks; 50 ft. of heavy galvanized wire: 80 ft.

of 1/4-in. manila rope and 4 pulley blocks. Four cleats are also required but these can be made of wood at home.

Draw a line on the four 7-in. boards along the side of each from end to end, 1-1/4-in. from one edge. Beginning at one end of each board make pencil dots on this line 5 in. apart for a distance of 3 ft. 4 in. Bore holes through the boards on these marks with a 9/15-in. bit. Fasten two of these boards on each post with the 3-in. screws, as shown in the top view of the post Fig. 1, forming a channel of the edges in which the holes were bored. Two of the filler pieces are fastened in each channel as shown, so as to make the s.p.a.ce fit the squared end of the bar snugly. The ends of the boards with the holes should be flush with the top of the post.

This will make each pair of holes in the 7-in. boards coincide, so the 1/2-in. bolt can be put through them and the squared end of the bar.

Select a level place where the apparatus is to be placed and dig two holes 6 ft. apart, each 3 ft. deep and remove all loose dirt.

The ends of the posts not covered with the boards are set in these holes on bricks or small stones. The channels formed by the boards must be set facing each other with the inner surfaces of the posts parallel and 5 ft. 8 in. apart. The holes around the posts are filled with earth and well tamped.

The hickory piece which is to form the bar should be planed, sc.r.a.ped and sandpapered until it is perfectly smooth and round except for 3 in. at each end. Bore a 9/16-in. hole through each square end 1-1/4 in. from the end. The bar may be fastened at any desired height by slipping the 1/2-in. bolts through the holes bored in both the bar and channel.

Each post must be well braced to keep it rigid while a person is swinging on the bar. Four anchors are placed in the ground at the corners of an imaginary rectangle 9 by 16 ft., in the center of which the posts stand as shown in Fig. 2. Each anchor is made of one 2-ft. piece of wood, around the center of which four strands of the heavy galvanized wire are twisted, then buried to a depth of 2 ft., the extending ends of the wires coming up to the surface at an angle.

The heavy screw eyes are turned into the posts at the top and lengths of ropes tied to each. These ropes or guys pa.s.s through the pulley blocks, which are fastened to the projecting ends of the anchor wire, and return to the posts where they are tied to cleats. Do not tighten the guy ropes without the bar in place, as to do so will strain the posts in the ground. Do not change the elevation of the bar without slacking up on the ropes. It takes but little pull on the guy ropes to make them taut, and once tightened the bar will be rigid.

[Ill.u.s.tration: Ground Plan]

Oil the bar when it is finished and remove it during the winter.

It is well to oil the wood occasionally during the summer and reverse the bar at times to prevent its becoming curved. The wood parts should be well painted to protect them from the weather.

** Electrostatic Illumination [299]