The Boy Mechanic Part 47

--Contributed by M. G. Lloyd, Ph.D., Was.h.i.+ngton, D. C.

** Home-Made Lantern [163]

[Ill.u.s.tration: Tin Can Lantern]

The accompanying picture shows a lantern which can be made almost anywhere for immediate use. All that is needed is an empty tomato or coffee can, a piece of wire and a candle. Make a hole a little smaller than the diameter of a candle and about one-third of the way from the closed end of the can, as shown. A wire is tied around the can, forming a handle for carrying. This kind of lantern can be carried against almost any wind and the light will not be blown out.

--Contributed by G. A. Sloan, Duluth, Minn.

** A Study of Splashes [164]

When a rough, or greasy, or dusty sphere falls into a liquid, the liquid is

[Ill.u.s.tration: Splashes from a Sphere In Milk and Water]

forced away from the sphere. If the sphere is quite smooth the liquid rises up around and enclosing it in a sheath says Knowledge and Scientific News.

Reproduced herewith are a series of photographs showing successive stages in the entry of a rough sphere into milk and water, and the resultant "basket splash." The diameter of this sphere was about 3/5 in., and the height of the fall about 6 in. Examination of the photographs shows that the liquid, instead of flowing over and wetting the surface of the sphere, is driven violently away, so far as can be seen from the photographs, the upper portion is, at first, unwetted by the liquid. The gradual thickening of the crater wall and the corresponding reduction in the number of its lobes as the subsidence proceeds is beautifully shown. Thereafter there rises from the depth of the crater an exquisite jet which in obedience to the law of segmentation at once splits up in its upper portion into little drops, while at the same time it gathers volume from below and rises ultimately as a tall, graceful column to a height which may be even greater than that from which the sphere fell.

** How to Make a Stick Pin [164]

A fine stick pin or b.u.t.ton can be made from a new one-cent piece.

Carefully file out all the metal around the Indian head and slightly round the edges. Solder a pin to the back of the head when it is to be used for a stick pin. If a collar b.u.t.ton base is soldered to the back of the head instead of the pin it can be used for a b.u.t.ton. These can be gold plated by a jeweler and then you will have a neat pin or b.u.t.ton, or a good emblem for the Order of Redmen.

[Ill.u.s.tration: Stick Pin]

** How to Make a Miniature Electric Locomotive [165]

A miniature electric railway is a thing that attracts the attention of almost any person. The cost of a toy electric locomotive is beyond the reach of many boys who could just as well make such a toy without much expense and be proud to say they "built it themselves." The electric locomotive described herewith uses for its power a small battery motor costing about $1. The first thing to do is to make the wheels and axles. If one has no

[Ill.u.s.tration: The Different Parts for Making the Electric Locomotive]

lathe, the wheels can be turned at some machine shop. Four wheels are made from a round bar of metal, as shown in Fig. 1. Each wheel is 1/4 in. thick and 1 in. in diameter, with a 1/16-in. f.l.a.n.g.e and a 1/4-in. hole drilled in the center. Each pair of wheels is fitted on a 1/4-in. axle, about 2-5/8 in. long. One of the axles should be fitted with a grooved belt wheel, as shown. Make the frame from three pieces of heavy bra.s.s, as shown in Fig. 2.

The first piece, or main part of the frame, is made from bra.s.s, 3/4 in. wide and 16 in. long, bent into an oblong shape and the ends soldered or bolted together. If the ends are to be soldered, before doing so drill four 1/4-in. holes 1 in. from the ends and insert the ends of the axles. The other two pieces are 1/2-in.

wide and of the dimensions shown in the sketch. These pieces are riveted in the middle of the oblong frame, each in its proper place. The motor is now bolted, bottom side up, to the top of the piece fastened to the frame lengthwise. A trolley, Fig. 3, is made from a piece of clock spring, bent as shown, and a small piece of tin soldered to the top end for a brush connection. A groove is made in the tin to keep the trolley wire in place.

The trolley wire is fastened to supports made of wood and of the dimensions given in Fig. 4. The trolley should be well insulated from the frame. The parts, put together complete, are shown in Fig. 5. Run a belt from the pulley on the motor to the grooved wheel on the axle, as shown in Fig. 6, and the locomotive is ready for running.

In making the connections the travel of the locomotive may be made more complicated by placing a rheostat and controlling switches in the line, so that the engine can be started and stopped at will from a distance and the speed regulated. Automatic switches can be attached at the ends of the line to break the circuit when the locomotive pa.s.ses a certain point.

One connection from the batteries is made to the trolley wire and the other to a rail. The connection for the motor runs from one binding post to the trolley and this connection must be well insulated to avoid a short-circuit. The other binding-post is connected to the frame.

The cost of making the wheels and purchasing the track will not be over $1.50. The track can be made from strips of tin put in a saw cut made in pieces of wood used for ties. This will save buying a track.

--Contributed by Maurice E. Fuller, San Antonio, Texas.

** Demagnetizing a Watch [166]

A test can be made to know if your watch is magnetized by placing a small compa.s.s on the side of the watch nearest the escapement wheel if the compa.s.s pointer moves with the escapement wheel the watch is magnetized. A magnetized watch must be placed in a

[Ill.u.s.tration: Watch Demagnetizer]

coil that has an alternating current of electricity flowing through it to remove the magnetism. A demagnetizer can be made as shown in the ill.u.s.tration. Two end pieces for the coil are made as shown in Fig. 1 from 1/4-in. wood. These ends are fastened together, Fig. 2, with cardboard 3 in. long glued to the inside edges of the holes cut in them. Wind upon the spool thus formed about 2 lb. of No. 16 cotton-covered copper wire. As it will be necessary to place a 16-cp. lamp in series with the coil, both the coil and lamp can be mounted on a suitable base and connected as shown in Fig. 3. The current, which must be 110 volt alternating current, is turned on the lamp and coil and the magnetized watch slowly drawn through the opening in the center of the coil.

--Contributed by Arthur Liebenberg, Cincinnati, O.

** How to Make a Pocket Skate Sharpener [166]

Secure a square file and break off a piece, Fig 1, the length of a paper clip, Fig. 2. Draw the temper in the ends of this piece of file, but do not heat the center. This can be done by wrapping a wet piece of cloth or asbestos around the middle and holding it in the jaws of a pair of tongs which will only leave the end uncovered and projecting from the tongs about 1/2 in. Hold this projecting end in a flame of a plumber's torch until it is a dull red. Allow this to cool slowly while in the tongs. When cold treat the other end in the same way. This will draw the temper in only the ends which are filed, as shown in Fig. 1, and holes drilled in them. Also drill a hole in each end of the spring on the paper clip to match those drilled in the piece of file. Fasten the file in the clip with small bolts, as shown in Fig. 3. When the file gets filled with filings it can be removed and cleaned. Place the runner of the skate in the clip and hold flat on the surface of the runner. If the piece of file is fitted to the same width as the skate runner the sides of the paper clip will hold the file level with the surface of the runner without any trouble. Push the clip back and forth until the skate is sharpened.

[Ill.u.s.tration: Sharpener for Skates]

** Old-Time Magic [167]

** Trick with a Coin in a Wine Gla.s.s [167]

The accompanying sketch shows a. trick of removing a dime from the bottom of an old fas.h.i.+oned wine gla.s.s without touching the coin.

The dime is first placed in the bottom of the gla.s.s and then a silver quarter dropped in on top. The quarter will not go all the way down. Blow hard into the gla.s.s in the position shown and the dime will fly out and strike the blower on the nose.

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

** Untying-a-Knot Trick [167]

Tie a double knot in a silk handkerchief, as shown in the accompanying sketch and tighten the last tie a little by slightly drawing the two upper ends; then continue to tighten much more, pulling vigorously at the first corner of the handkerchief, and as this end belongs to the same corner it cannot be pulled much without loosening the twisted line of the knot to become a straight line. The other corner forms a slip knot on the end, which can be drawn out without disturbing the form, or apparent security of the knot, at the moment when you cover the knot with the unused part of the handkerchief. When the trick is to be performed, tie two or three very hard knots that are tightly drawn and show your audience that they are not easy to untie. The slip knot as described then must be made in apparently the same way

[Ill.u.s.tration: Knot Trick]

and untied with the thumb while the knot is in the folds of the handkerchief.

** Gear-Cutting Attachment for Small Lathes [167]