The Boy Mechanic Part 84

Anyone having the use of a static machine can perform the following experiment which gives a striking result. A common tumbler is mounted on a revolving

[Ill.u.s.tration: Illuminated Tumbler]

platform and a narrow strip of tinfoil is fastened with sh.e.l.lac varnish to the surface of the gla.s.s as follows: Starting beneath the foot of the gla.s.s from a point immediately below the stem, it is taken to the edge of the foot; it follows the edge for about 1 in. and then pa.s.ses in a curve across the base, and ascends the stem; then it pa.s.ses around the bowl in a sinuous course to the rim, which it follows for about one-third of its circ.u.mference; after which it descends on the inside and terminates at the bottom. The tinfoil on the outside of the gla.s.s is divided by cutting with a knife every 1/8 in., the parts inside and beneath the gla.s.s being left undivided. Current is then led from a static machine to two terminals, one terminal being connected to one end of the tinfoil strip, and similarly the second terminal makes contact with the other end. As soon as the current is led into the apparatus, a spark is seen at each place where the knife has cut through the tinfoil. If the tumbler is rotated, the effect will be as shown in the ill.u.s.tration. A variety of small and peculiar effects can be obtained by making some of the gaps in the tinfoil larger than others, in which case larger sparks would be produced at these points. The experiment should be carried out in a darkened room, and under these circ.u.mstances when nothing is visible, not even the tumbler, the effect is very striking.

** Balloon Ascension Illusion [300]

By C. W. Nieman

In these days of startling revelations in air-craft flight we are prepared to see any day some marvelous machine driven bird cutting figure-eights all over the sky above our heads. One boy recently took advantage of this state of expectancy to have an evening's harmless amus.e.m.e.nt, through an illusion which deceived even the most incredulous. He caused a whole hotel-full of people to gaze open mouthed at a sort of "Zeppelin XXIII," which skimmed along the distant horizon, just visible against the dark evening sky, disappearing only to reappear again, and working the whole crowd up to a frenzy of excitement. And all he used was a black thread, a big piece of cardboard and a pair of field gla.s.ses.

He stretched the thread between two buildings, about 100 ft.

apart, in an endless belt, pa.s.sing through a screweye at either end. On this thread he fastened a cardboard "cut-out" of a dirigible, not much to look at in daytime, but most deceptive at dusk. By pulling one or the other string he moved the "airs.h.i.+p" in either direction. He took the precaution of stretching his thread just beyond a blackberry hedge and thus kept over-inquisitive persons at a safe distance. He also saw to it that there was a black background at either end so that the reversing of the direction of the craft would not be noticed.

In attracting the crowd he had a confederate stand looking at the moving s.h.i.+p through a field gla.s.s, which at once gave the suggestion of distance, and materially heightened the illusion.

When the interest of the crowd, which at once gathered, was at its height, the "aeronaut" pulled his craft out of sight and let the disillusion come when the light of day laid bare his fraud.

** A Cork Extractor [300]

The device shown in the sketch is for removing a cork or stopper from a bottle whether full or empty where the cork has been pushed inside. A wire about No. 14 gauge is bent as shown at B, Fig. 1, to fit the index finger and the other end filed to a point C, and turned in a spiral D, so the point will be on top. Insert this tool in the bottle as shown in Fig. 2 and place the end D under the cork and pull up. The cork will come out easily. --Contributed by Maurice Baudier. New Orleans. La.

[Ill.u.s.tration: Cork Extractor]

** An Outdoor Gymnasium Part II-Parallel Bars [301]

Parallel bars hold a high place in the affection of those who frequent gymnasiums as the best apparatus for development of the back and shoulder muscles, as well as a promoter of ease and grace of movement. The outdoor "gym" can have a set of these bars with very little more labor than was required for the horizontal bar.

The material required is as follows:

[Ill.u.s.tration: Detail of the Parallel Bars]

4 posts, preferably cedar, 4 in. square and 6 ft. long; 2 base pieces, 4 in. square and 5-1/2 ft. long; 2 cross braces, 2 by 4 in. by 2 ft. 2 in. long; 2 side braces, 2 by 4 in. by 7 ft. 8 in. long; 4 knee braces, 2 by 4 in. by 3 ft. 8 in. long; 2 bars of straight grained hickory, 2 by 3 in. by 10 ft. long; 4 wood screws, 6 in. long; 4 bolts, 8 in. long; 8 bolts, 7 in. long and 1 doz. large spikes.

To make the apparatus, lay off the bases as shown in the end view and bevel the ends at an angle of 60 deg. Chisel out two notches 4 in. wide and 1 in. deep, beginning at a point 9 in. from either side of the center. These are to receive the lower ends of the posts. Bevel two sides of one end of each post down to the width of the finished bar--a little less than 2 in. Cut notches in these ends to receive the oval bars. Bevel the ends of the knee braces, as shown in the diagram, and fasten the lower ends to the beveled ends of the bases with the spikes. Fasten the upper ends of the knee braces to the uprights with the 8-in. bolts put through the holes bored for that purpose, and countersinking the heads. Lay the whole end flat on the ground and make a mark 2-1/2 ft. from the bottom of the base up along the posts, and fasten the end braces with their top edges flush with the marks, using four of the 7-in bolts. Finally toe-nail the base into the ends of the posts merely to hold them in position while the whole structure is being handled.

Two endpieces must be made. These sets or ends of the apparatus are to be buried in trenches dug to the depth of 2-1/2 ft., with the distance between the two inner surfaces of the posts, which face each other, of 7 ft. After the trenches are dug, additional long, shallow trenches must be made connecting the posts to receive the side braces. The function of these side braces is to hold both ends together solidly. It is necessary to bury these braces so they will be out of the way of the performer. The side braces are bolted to the posts just below the cross braces, so the bolts in both will not meet. The bars are dressed down so that a cross section is oval as shown in the end view. They are to be screwed to the notched ends of the uprights with the 6-in. screws.

The holes should be countersunk so they can be filled with putty after the screws are in place. The bars should be well oiled with linseed oil to protect them from the weather, and in the winter they should be removed and stored.

Every piece of wood in this apparatus can be round and cut from trees, except the bars. If using mill-cut lumber, leave it undressed, and if using round timber leave the bark upon it as a protection from the weather. It is well to paint the entire apparatus, save the bars, before burying the lower part of the end pieces. The wood so treated will last for years, but even unpainted they are very durable. Be sure to tamp down the earth well about the posts. A smooth piece of ground should be selected on which to erect the apparatus. (To be Continued.)

** Combined Ladle and Strainer [302]

When using a strainer in connection with a ladle the operation requires both

[Ill.u.s.tration: Ladle and Strainer]

hands. A convenient article where a ladle and strainer are needed is to swing a cup-shaped strainer under the bowl of a ladle as shown in the ill.u.s.tration. The strainer can be held in place with small bands that fit loosely over the handle and a small tip soldered to the ladle. These will allow the ladle to be turned, leaving the strainer always in position. A large sized ladle, equipped with a strainer, is just the thing for painters to dip and strain paint, while a small one is of great a.s.sistance to the housewife for dipping and straining soups, jellies, etc.

--Contributed by W. A. Jaquythe, Richmond, Cal.

** Cleaning Gloves [302]

A solution consisting of 1 dr. of sodium carbonate and 1 qt. of milk makes an excellent cleaner for motorists' gloves.

** Turpentine in Cutting Oil [302]

When cutting steel or wrought iron in a lathe, milling machine, drill press or planer, it is sometimes necessary to leave a smooth surface. Oil, or various cutting compounds of oil, is used for this purpose and to keep the surface cool. If a little turpentine is added to the oil, it will greatly a.s.sist in leaving a smooth surface. A proportion of one-quarter turpentine is good.

** Center of Gravity Experiment [302]

This experiment consists of suspending a pail of water from a stick placed upon a table as shown in the accompanying sketch. In order to accomplish this experiment, which seems impossible, it is necessary to place a stick, A, of sufficient length,

[Ill.u.s.tration: Experiment]

between the end of the stick on the table and the bottom of the pail. This makes the center of gravity somewhere near the middle of the stick on the table, thus holding the pail as shown.

** Lathe Accuracy [302]

A heavy lathe cut will not do accurate work.

** An Outdoor Gymnasium PART III-The Horse [303]

The German horse is that peculiar piece of apparatus which is partly a horizontal obstruction to leap over, partly a barrier for jumps, partly a smooth surface of long and narrow dimensions over and about which the body may slide and swing, and partly an artificial back for the purpose of a peculiar style of leap frog.

[Ill.u.s.tration: The German Horse]

To make a horse for the outdoor "gym" requires no difficult work save the preparation of the top or body of the horse. The making of the regular gymnasium horse requires a very elaborate wood-working and leather upholstering plant, but the one used for outdoor work can be made of a log of wood. Procure from a saw mill, wood yard or from the woods, one-half of a tree trunk from a tree 9 to 15 in. in diameter--the larger the better. The length may be anywhere from 4 to 7 ft., but 5 ft. is a good length.

The round part of this log must be planed, sc.r.a.ped and sandpapered until it is perfectly smooth, and free from knots, projections and splinters. Hand holds must be provided next. These are placed 18 in. apart in a central position on the horse. Make two parallel saw cuts 2 in. apart, straight down in the round surface of the horse until each cut is 9 in. long. Chisel out the wood between the cuts and in the mortises thus made insert the hand holds. Each hand hold is made of a 9-in. piece of 2 by 4-in. stud cut rounding on one edge. These are well nailed in place.

The body of the horse is to be fastened on top of posts so that it may be adjusted for height. It is not as difficult to make as the horizontal and parallel bars. The material required is as follows: Two posts, 4 in. square by 5 ft. long; 2 adjusting pieces, 2 by 4 in. by 3 ft. 3 in. long; 1 cross brace, 2 by 4 in. by 3 ft. long; 2 bases, 4 in. square by 5-1/2 ft. long; 4 knee braces, 2 by 4 in.

by 3 ft. long; two 1/2-in. bolts, 1 in. long, to fasten the knee braces at the top; ten 1/2-in. bolts, 7 in. long, 4 to fasten the knee braces at the bottom, 2 to fasten the cross brace and 4 to be used in fastening the adjusting pieces to the posts.