The Boy Mechanic Part 113

A 2-in. shaft of wood, Fig. 2, is turned down to 1 in. on the ends and put through holes that must be bored in the front ends of the 2 by 6-in. pieces. A small pin is put through each end of the shaft to keep it in place. The rudder is a 1-1/2-in. hardwood piece which should be tapered to 1/2 in. at the bottom and shod with a thin piece of iron. A 1/2-in. hole is bored through the center of the shaft and a lag screw put through and turned in the rudder piece, making it so the rudder will turn right and left and, also, up and down. Two cleats are nailed to the upper sides of the runners and in the middle lengthways for the person's heels to rest against.

Any child can guide this bob, as all he has to do is to guide the rudder right and left to go in the direction named. If he wants to stop, he pulls up on the handle and the heel of the rudder will dig into the snow, causing too much friction for the sled to go any further.

--Contributed by Wm. Algie, Jr., Little Falls, N. Y.

** How to Make a Small Microscope [408]

Theoretically a simple microscope can be made as powerful as a compound microscope, but in practice the minute size required by the simple lens to give the highest power makes it almost impossible to be used. However, a lens having a reasonable magnifying power can be made in a few minutes for almost nothing.

Take a piece of gla.s.s tubing, heat one place in a hot flame, hold one end and pull on the other and draw the heated place down to a fine string as shown in Fig. 1. Take about 3 in. of this fine tube and heat one end which will form a gla.s.s bead as shown in Fig. 2.

This bead is the lens. When in this form it can be used only in an artificial light coming from one direction, but if you take a piece of

[Ill.u.s.tration: Lens Formed by Heat]

cardboard and bore a hole in it a little smaller than the bead on the gla.s.s tube which is forced into the hole, Fig 3, you can use this mounted lens in ordinary daylight. In this case a mirror must be used to reflect the light up through the lens. It is difficult to see anything at first, as the lens must be held very close to the eye, but in practice you will soon learn to see the object as it appears enlarged.

If you soak a little dried gra.s.s or hay in water for a few days and look at a drop of this water, germs in various life forms can be seen. The water must be put on the lens. One thing to remember is that the smaller the lens, the greater the magnifying power.

--Contributed by Daniel Gray, Decatur, Illinois.

** Freezing Pipes [409]

The water in hot water supply pipes will freeze quicker than water that has not been heated. This is because the air, which is a poor conductor of heat, has been driven out by the heat.

** How to Carry Books [409]

Almost all school children carry their books with a strap put around and b u c k led very tight. This will make dents in the cover where the board overlaps the body of the book. If the strap is left loose, the books are liable to slip out. Place the cover of one book between the cover and fly leaf of its neighbor and the difficulty will be remedied. This will place the books in alternate directions. Books stacked in this manner do not require the strap buckled tight, or, they can be carried without any strap just as well.

--Contributed by Thos. De Loaf, Grand Rapids, Mich.

[Ill.u.s.tration: Stacking Books]

** Bottle Pushers [409]

[Ill.u.s.tration: BOTTLE PUSHERS. --This is a game in which the compet.i.tors push bottles on the ice with hockey sticks. All the bottles must be the same size and make. The persons partic.i.p.ating must keep their bottles upright at all times. The bottles are lined up for the start and at the word "go," each person pushes a bottle across the field for a distance that is agreed upon.]

** How to Make a Hammock [410]

Anyone can make a hammock as good as can be bought and that at a cost so small that every member of the family can possess one providing there are places enough for hanging them.

The materials required are a needle about 7 in. long, and with a big eye, an iron ring for each end of the hammock, two long smooth sticks on which to knit the hammock and two pounds of strong hemp cord or twine. The twine may be colored in any color or combination of colors desired. A Roman stripe at each end of the hammock makes a pretty effect.

A hammock 45 in. wide will not be too large for solid comfort. To knit it first thread the big needle and holding it in the left hand, hold the cord in place with the thumb until you have looped the cord over the tongue, then pa.s.s the cord under the needle to the opposite side and catch it over the tongue. Repeat this operation until the needle is full. Cut a 2-yd. length of cord and make a loop and fasten to the door k.n.o.b or to some other convenient place. Tie the cord on the needle to this loop 3 in.

from the end of the loop. Place the small mesh stick under the cord with the beveled edge close to the loop, and, with a thumb on the cord to hold it in place, pa.s.s the needle around the stick and then, point downward, pa.s.s it through the loop from the top, and then bring it over the stick so forming the first half of the knot.

Pull this tight and hold in place with a thumb while throwing the cord over your hand, which forms the loop. Pa.s.s the needle from under through the loops and draw fast to fasten the knot. Hold this in place and repeat the operation.

Make 30 of these knots and then push them off the stick and proceed in the same way with the next row, pa.s.sing the needle first through each of the 30 knots made for the first row. Make 30 rows and then tie the last loops to the other iron ring.

Stretchers may be made and put in place and the hammock, strong and durable, is finished. The work must be carefully and evenly done. One is apt to have a little trouble getting the first row right, but after that the work proceeds quite rapidly.

How to Obtain Cheap Dry Batteries [410]

Not very many people realize that good, serviceable dry cells can be obtained from an automobile garage very cheap. These cells having been "run out" beyond the required number of amperes for automobile use, will give excellent service, considering their cost. Many of them will give two-thirds of their original amperage. Six of such cells have been in use on my door-bell circuit for nearly a year. They can be used for other purposes just as well.

--Contributed by H. H. Cutter.

** How to Make a Water Telescope [410]

[Ill.u.s.tration: The Water Telescope]

Before you decide on a place to cast your hook it is best to look into the water to see whether any fish are there. Yes, certainly, you can look into the water and see the fish that are there swimming about, if you have the proper equipment. What you need is a water telescope. This is a device made of wood or metal with one end of gla.s.s. When the gla.s.s end is submerged, by looking in at the open end, objects in the water are made plainly visible to a considerable depth. In Norway, the fishermen use the water telescope regularly in searching for herring shoals or cod.

All that is necessary to make a wooden water telescope is a long wooden box, a piece of gla.s.s for one

[Ill.u.s.tration: Wooden Water Telescope]

end and some paint and putty for making the seams watertight. Fix the gla.s.s in one end of the box, and leave the other open to look through.

A tin water telescope is more convenient than the wooden one, but more difficult to make, The princ.i.p.al essential for this is a circular piece of gla.s.s for the large end. A funnel shaped tin horn will do for the rest. Solder in the gla.s.s at the large end and the telescope is made. Sinkers consisting of strips of lead should be soldered on near the bottom to counteract the buoyancy of the air contained in the watertight funnel and also helps to submerge the big end. The inside of the funnel should be painted black to prevent the light from being reflected on the bright surface of the tin. If difficulty is found in obtaining a circular piece of gla.s.s, the bottom may be made square and square gla.s.s used. Use plain, clear gla.s.s; not magnifying gla.s.s. To picnic parties the water telescope is of great amus.e.m.e.nt, revealing numerous odd sights in the water which many have never seen before.

** How to Rid Your Yard of Cats [411]

The following is a description of a device I built at my home in Brooklyn, which not only gave us relief from the

[Ill.u.s.tration: Electric Apparatus for Driving Away Cats]

nightly feline concerts, but also furnished much amus.e.m.e.nt to my friends.

I first ran two bare copper wires along the top of the fence about 1 in. apart, fastening them down with small staples, care being taken that they did not touch. To the ends of these wires I fastened ordinary insulated bell wire, running them to the house and connecting them to the upper binding-posts of an induction coil; I then ran a wire from the lower binding-post of my coil through the batteries back to the other lower binding-post of coil, breaking the circuit by putting in an ordinary switch. The more batteries used, the stronger the current. The switch should always be left open, as it uses up the current very rapidly.

When "tabby" is well on the wires I close the switch and she goes the length of the fence in bounds, often coming back to see what the trouble is, thus receiving another shock.

--Contributed by Charles L. Pultz.

** Subst.i.tute for a Drill Bit [411]

A gouge may be used as a subst.i.tute bit if a proper sized bit is not at hand. The gouge can be placed in the brace the same as a bit.