The Boy Mechanic Part 1

The Boy Mechanic.

Volume 1.

by Popular Mechanics.

** A Model Steam Engine [1]

The accompanying sketch ill.u.s.trates a two-cylinder single-acting, poppet valve steam engine of home construction.

The entire engine, excepting the flywheel, shaft, valve cams, pistons and bracing rods connecting the upper and lower plates of the frame proper, is of bra.s.s, the other parts named being of cast iron and bar steel.

The cylinders, G, are of seamless bra.s.s tubing, 1-1/2 in. outside diameter; the pistons, H, are ordinary 1-1/2 in. pipe caps turned to a plug fit, and ground into the cylinders with oil and emery.

This operation also finishes the inside of the cylinders.

The upright rods binding the top and bottom plates are of steel rod about 1/8-in. in diameter, threaded into the top plate and pa.s.sing through holes in the bottom plate with hexagonal bra.s.s nuts beneath.

The valves, C, and their seats, B, bored with a countersink bit, are plainly shown. The valves were made by threading a copper washer, 3/8 in. in diameter, and s.c.r.e.w.i.n.g it on the end of the valve rod, then wiping on roughly a tapered ma.s.s of solder and grinding it into the seats B with emery and oil.

The valve rods operate in guides, D, made of 1/4-in. bra.s.s tubing, which pa.s.ses through the top plate and into the heavy bra.s.s bar containing the valve seats and steam pa.s.sages at the top, into which they are plug-fitted and soldered.

The location and arrangement of the valve seats and steam pa.s.sages are shown in the sketch, the flat bar containing them being soldered to the top plate.

The steam chest, A, over the valve mechanism is constructed of

[Ill.u.s.tration: Engine Details]

1-in. square bra.s.s tubing, one side being sawed out and the open ends fitted with pieces of 1/16 in. sheet bra.s.s and soldered. in.

The steam inlet is a gasoline pipe connection such as used on automobiles.

The valve-operating cams, F, are made of the metal ends of an old typewriter platen, one being finished to shape and then firmly fastened face to face to the other, and used as a pattern in filing the other to shape. Attachment to the shaft, N, is by means of setscrews which pa.s.s through the sleeves.

The main bearings, M, on the supports, O, and the crank-end bearings of the connecting rods, K, are split and held in position by machine screws with provision for taking them up when worn.

The exhausting of spent steam is accomplished by means of slots, I, sawed into the fronts of the cylinders at about 1/8 in. above the lowest position of the piston's top at the end of the stroke, at which position of the piston the valve rod drops into the cutout portion of the cam and allows the valve to seat.

All the work on this engine, save turning the pistons, which was done in a machine shop for a small sum, and making the flywheel, this being taken from an old dismantled model, was accomplished with a hacksaw, bench drill, carborundum wheel, files, taps and dies. The base, Q, is made of a heavy piece of bra.s.s.

The action is smooth and the speed high. Steam is supplied by a sheet bra.s.s boiler of about 3 pt. capacity, heated with a Bunsen burner.

--Contributed by Harry F. Lowe, Was.h.i.+ngton, D. C.

** Magic Spirit Hand [2]

The magic hand made of wax is given to the audience for examination, also a board which is suspended by four pieces of common picture-frame wire. The hand is placed upon the board and answers, by rapping, any question asked by members of the audience. The hand and the board may be examined at any time and yet the rapping can be continued, though surrounded by the audience.

The Magic Wand, London, gives the secret of this spirit hand as follows: The hand is prepared by concealing in the wrist a few soft iron plates, the wrist being afterwards bound with black velvet as shown in Fig. 1. The board is hollow, the top being made of thin veneer (Fig. 2). A small magnet, A, is connected to a small flat pocket lamp battery, B. The board is suspended by four lengths of picture-frame wire one of which, E, is

[Ill.u.s.tration: Wax Hand on Board and Electrical Connections]

connected to the battery and another, D, to the magnet. The other wires, F and G, are only holding wires. All the wires are fastened to a small ornamental switch, H, which is fitted with a connecting plug at the top. The plug can be taken out or put in as desired.

The top of the board must be made to open or slide off so that when the battery is exhausted a new one can be installed.

Everything must be firmly fixed to the board and the hollow s.p.a.ce filled in with wax, which will make the board sound solid when tapped.

In presenting the trick, the performer gives the hand and board with wires and switch for examination, keeping the plug concealed in his right hand. When receiving the board back, the plug is secretly pushed into the switch, which is held in the right hand.

The hand is then placed on the board over the magnet. When the performer wishes the hand to move he pushes the plug in, which turns on the current and causes the magnet to attract the iron in the wrist, and will, therefore, make the hand rap. The switch can be made similar to an ordinary push b.u.t.ton so the rapping may be easily controlled without detection by the audience.

** Making Skis and Toboggans [3]

During the winter months everyone is thinking of skating, coasting or ski running and jumping. Those too timid to run down a hill standing upright on skis must take their pleasure in coasting or skating.

The ordinary ski can be made into a coasting ski-toboggan by joining two pairs together with bars without injury to their use for running and jumping. The ordinary factory-made skis cost from $2.50 per pair up, but any boy can make an excellent pair far 50 cents.

In making a pair of skis, select two strips of Norway pine free from knots, 1 in. thick, 4 in. wide and 7 or 8 ft. long. Try to procure as fine and straight a grain as possible. The pieces are dressed thin at both ends leaving about 1 ft. in the center the full thickness of 1 in., and gradually thinning to a scant 1/2 in.

at the ends. One end of each piece is tapered to a point beginning 12 in. from the end. A groove is cut on the under side, about 1/4 in. wide and 1/8 in. deep, and running almost the full length of the ski. This will make it track straight and tends to prevent side slipping. The shape of each piece for a ski, as it appears before bending, is shown in Fig. 1.

The pointed end of each piece is placed in boiling water for at least 1 hour, after which the pieces are ready for bending. The bend is made on an ordinary stepladder. The pointed ends are stuck under the back of one step and the other end securely tied to the ladder, as shown in Fig. 2. They should remain tied to the ladder 48 hours in a moderate temperature, after which they will hold their shape permanently.

The two straps, Fig. 3, are nailed an a little forward of the center of gravity so that when the foot is lifted, the front

[Ill.u.s.tration: Fig. 1, Fig. 2, Fig. 3 -- Forming the Skis]

of the ski will be raised. Tack on a piece of sheepskin or deer hide where the foot rests, Fig. 4.

The best finish for skis is boiled linseed oil. After two or three

[Ill.u.s.tration: Fig. 4 -- The Toe Straps]

applications the under side will take a polish like gla.s.s from the contact with the snow.

The ski-toboggan is made by placing two pairs of skis together side by side

[Ill.u.s.tration: Fig. 5 -- Ski-Toboggan]

and fastening them with two bars across the top. The bars are held with V-shaped metal clips as shown in Fig. 5.

--Contributed by Frank Scobie, Sleepy Eye, Minn.

** Homemade Life Preserver [4]

Procure an inner tube of a bicycle tire, the closed-end kind, and fold it in four alternate sections, as shown in Fig. 1. Cut or tear a piece of cloth into strips about 1/2 in. wide, and knot them together. Fasten this long strip of cloth to the folded tube and weave it alternately in and out, having each

[Ill.u.s.tration: Fig. 1, Fig. 2; Inner Tube and Cover]