Things To Make by Archibald Williams (which ebook reader TXT) 📕

better type is shown in Figs. 123 and 124. Select a canister at least 6 inches in diameter, and not more than 6 inches long, with an overlapping lid. Get a turner to make for you a couple of wooden discs, 3/8 inch thick, and having a diameter 2 inches greater than that of the tin. Holes at least 3/8 inch across should be bored in the centre of each. Cut holes 1 inch across in the centre of the lid and the bottom of the canister, and nail the lid concentrically to one disc, the canister itself to the other. Then push the lid on the tin and solder them together. This gives you a large reel. For the spindle you will require a piece of brass tubing or steel bar 1 foot long and large enough to make a hard driving fit with the holes in the wood. Before driving it in, make a framework of 3/4-inch strip iron (Fig. 123), 3/32 or 1/8 inch thick, for the reel to turn in. The width of this framework is 1 inch greater than the length of the reel; its length is twice the diameter of the canister. Rivet or solder the ends together. Halfway along the sides bore holes to fit the spindle.

Make a mark 1 inch from one end of the spindle, a second l/8 inch farther away from the first than the length of the reel. Drill 3/16-inch holes at the marks. Select two wire nails which fit the holes, and remove their heads. Next cut two 1/4-inch pieces off a tube which fits the spindle. The reel, spindle, and framework are now assembled as follows:

[Illustration: FIG. 124.—End view of string winder, showing brake and lever.]

Push the end of the spindle which has a hole nearest to it through one of the framework holes, slip on one of the pieces of tubing, drive the spindle through the reel until half an inch projects; put on the second piece of tubing, and continue driving the spindle till the hole bored in it shows. Then push the nails half-way through the holes in the spindle, and fix them to the ends of the reel by small staples. A crank is made out of 1/2-inch wood (oak by preference) bored to fit the spindle, to which it must be pinned. A small wooden handle is attached at a suitable distance away. If there is any fear of the wood splitting near the spindle, it should be bound with fine wire. An alternative method is to file the end of the spindle square, and to solder to it a piece of iron strip in which a square hole has been made to fit the spindle. The crank should be as light as is consistent with sufficient strength, and be balanced so that there shall not be unpleasant vibration when the string runs out fast, and of course it must be attached very securely to the spindle.

What will be the front of the framework must be rounded off on the top edge, which has a wire guide running parallel to it (Fig. 123) to direct the string on to the reel; and into the back are riveted a couple of eyes, to which are attached the ends of a cord passing round the body, or some stationary object.

[Illustration: FIG. 125.—String winder in operation.]

A pin should be provided to push into a hole at one end of the reel and lock the reel by striking the framework, and it will be found a great convenience to have a brake for controlling the reel when the kite is rising. Such a brake is easily fitted to the side of the frame, to act on the left end of the reel when a lever is depressed by the fingers. There should be a spring to keep it off the reel when it is not required. The diagrams show where the brake and brake lever are situated.

Note.—To obtain great elevations a fine wire (piano wire 1/32 inch in diameter) is generally used, but to protect the user against electric shocks the wire must be connected with an "earthed" terminal, on the principle of the lightning conductor.

XXIV. PAPER GLIDERS.

In this chapter are brought to your notice some patterns of paper gliders which, if made and handled carefully, prove very satisfactory. Gliders are sensitive and "moody" things, so that first experiments may be attended by failure; but a little persistence will bring its reward, and at the end of a few hours you will, unless very unlucky, be the possessor of a good specimen or two.

The three distinguishing features of a good glider are stability, straightness of flight, and a small gliding angle. If the last is as low as 1 in 10, so that the model falls but 1 foot vertically while progressing 10 feet horizontally, the glider is one to be proud of.

Materials.—The materials needed for the gliders to be described are moderately stout paper—cream-laid notepaper is somewhat heavy for the purpose—and a little sealing wax or thin sheet metal for weighting.

[Illustration: FIG. 126.—Paper glider: Model "A."]

[Illustration: FIG. 127.—How to launch Model "A."]

Model "A."—Double a piece of paper 8 inches long and 2-1/2 inches wide, and cut out, through both folds, the shape shown in Fig. 126. Flatten the piece and fold the "head" inwards four times on the side away from the direction in which the paper was folded before being cut out. Flatten the folds and fix to the centre a little clip formed by doubling a piece of thin metal 3/16 by 1/2 inch. Make certain that the wings are quite flat, and then, holding the glider between thumb and first finger, as shown in Fig. 127, push it off gently. If the balance is right, it will fly quite a long way with an undulating motion. If too heavy in front, it will dive; if too light, it will rise suddenly and slip backwards to the ground. The clip or the amount of paper in the head must be modified accordingly. This type is extraordinarily efficient if the dimensions, weighting, and shape are correct, and one of the easiest possible to make.

Model "B."—The next model (Fig. 128), suggesting by its shape the Langley steam-driven aeroplane, has two sets of wings tandem. Double a piece of paper and cut out of both folds simultaneously a figure of the shape indicated by the solid lines in the diagram. The portion A is square, and forms the head weight; B indicates the front planes, C the rear planes. Bend the upper fold of each pair into the positions B1, C1, marked by dotted lines. Their front edges make less than a right angle with the keel, to ensure the wings slanting slightly upwards towards the front when expanded.

The model is now turned over, and the other wings are folded exactly on top of their respective fellows. Then the halves of the head are folded twice inwards, to bring the paper into as compact a form as possible. It remains to open out the wings at right angles to the keel, and then raise their tips slightly so that the two planes of a pair shall make what is called a "dihedral" angle with one another.

[Illustration: FIG. 128.—Details of paper gliders: Model "B" above,
Model "C" below.]

Before launching, look at your model endways and make sure that the rear planes are exactly in line with those in front. It is essential that they should be so for straight flight. Then grip the keel at its centre between finger and thumb and launch gently. Mark how your glider behaves. If it plunges persistently, trim off a very little of the head. If, on the contrary, it settles almost vertically, weight must be added in front. The position of the weight is soon found by sliding a metal clip along the keel until a good result is obtained.

Note that if the leading edges of the front wings are bent slightly downwards the glider may fly much better than before.

A good specimen of this type is so stable that if launched upside down it will right itself immediately and make a normal flight.

Model "C."—This is cut out of doubled paper according to the solid lines of Fig. 128. The three sets of planes are bent back in the manner already described, but the front planes are given a somewhat steeper angle than the others. This type is very stable and very fairly efficient.

General Remarks.—Always pick up a glider by the keel or middle, not by one of the wings, as a very little distortion will give trouble.

The merits of a glider depend on length, and on straightness of flight; so in competition the launching height should be limited by a string stretched across the room, say 6 feet above the floor. If the room be too short for a glider to finish its flight, the elevation at which it strikes the wall is the measure of its efficiency.

Out-of-door flights are impracticable with these very frail models when there is the slightest breeze blowing. On a perfectly calm day, however, much better fun can be got out of doors than in, owing to the greater space available. A good glider launched from a second-floor window facing a large lawn should travel many yards before coming to grass.

Large gliders of the types detailed above can be made of very stout paper stiffened with slips of cane or bamboo; but the time they demand in construction might perhaps be more profitably spent on a power-driven aeroplane such as forms the subject of the next chapter.

XXV. A SELF-LAUNCHING MODEL AEROPLANE.
By V. E. Johnson, M.A.

This article deals not with a scale model—a small copy of some full-sized machine—but with one designed for actual flight; with one not specially intended to create records either of length or duration, but which, although small details must perforce be omitted, does along its main lines approximate to the "real thing."

Partly for this reason, and partly because it proves a far more interesting machine, we choose a model able to rise from the ground under its own power and make a good flight after rising, assuming the instructions which we give to have been carefully carried out. It is perhaps hardly necessary to add that such a machine can always be launched by hand when desired.

Before entering into special details we may note some broad principles which must be taken into account if success is to attend our efforts.

Important Points.—It is absolutely essential that the weight be kept down as much as possible. It is quite a mistake to suppose that weight necessarily means strength. On the contrary, it may actually be a cause of weakness if employed in the wrong place and in the wrong way. The heavier the machine, the more serious the damage done in the event of a bad landing. One of the best and easiest ways of ensuring lightness is to let the model be of very simple construction. Such a model is easier to build and more efficient when constructed than one of more complicated design. Weigh every part of your model as you construct it, and do not be content until all symmetrically arranged parts which should weigh the same not only look alike but do actually balance one another. (Note.—The writer always works out the various parts of his models in grammes, not ounces.) If a sufficiently strong propeller bearing weighing only half a gramme can be employed, so much the better, as you have more margin left for some other part of the model in which it would be inadvisable to cut down the weight to a very fine limit.

Details.—To pass now to details, we have four distinct parts to deal with:—

1. The framework, or fuselage.

2. The supporting surfaces, consisting of the main plane, or aerofoil, behind, and the elevator in front.

3. The propellers.

4. The motor, in this case two long skeins of rubber; long, because we wish to be able to give our motor many turns, from 700 to, say, 1,000 as a limit, so that the duration of flight may be considerable.

[Illustration: FIG. 129.-Sections of backbone for model aeroplane.]

The Backbone.—For the backbone or central rod take a piece of pitch pine or satin walnut 52 inches long, 5/8 inch deep, and 1/2 inch broad, and plane it down carefully until it has a T-shaped section, as shown in Fig. 129, and the thickness is not anywhere more than 1/8 inch. It is quite possible to reduce the thickness