The boy mechanic, book 3

by Unknown

Steel Wool as Aluminum-Ware Cleaner

It takes little trouble to keep aluminium pots and pans shining if they are cleaned frequently with steel wool, water, and a nonalkaline soap. Use a very fine grade of the wool, and give the utensils a few rubs frequently rather than attempt to clean them only occasionally, when much soiled.—L. P. Langan, Denver, Colo.

How to Make a Model Old-Four Monoplane
By RALPH M. BROWN

The old-four monoplane model, made famous by its wonderful flights, is one of the most graceful that has been built. Its large size and slow, even glide make it a much more desirable flier than the ordinary dartlike model. It gives one a true insight into the phenomena of heavier-than-air flight. This machine, when complete, should weigh 9 oz. and fly 1,200 ft., rising from the ground under its own power and landing lightly. Its construction is simple, and with careful reference to the sketches, an exact reproduction may be made.

For the motor bases, A, [Fig. 1], secure two spruce sticks, each 48 in. long, ³⁄₈ in. wide, and ¹⁄₄ in. thick, and fasten a wire hook on one end of each stick with thread wound around after giving it a coat of glue. These hooks are to hold one end of the rubber bands that act as the motive power, and are designated by the letter B. At the opposite ends of the sticks, at C, bearings are provided, which consist of blocks of wood, each 1 in. long, 1 in. wide, and ³⁄₈ in. thick. These are also bound in place with thread after gluing them. Holes are drilled through the blocks lengthwise and then lined with bushings made of brass tubing, ¹⁄₁₆ in. in inside diameter. The two motor bases A are connected with four cross sticks, D, each 9 in. long and ³⁄₁₆ in. square. These are bound and glued on the under side, one near each end and the others equidistant each from the other and from the nearest end stick. The front bumper E is made of round rattan, ¹⁄₈ in. in diameter.

The Mechanical Bird will Run About Five Feet on the Ground and Then Rise and Fly

The alighting gear is next in order of construction. This is made as shown entirely of bamboo, ³⁄₁₆ in. square. The pieces marked F are 11 in. long; G, 9¹⁄₂ in. long, and the cross bar H, 11 in. long. At the rear, the pieces J are 13 in. long; K, 4¹⁄₂ in. long, and the cross piece L, 11 in. long. The distance between the points M and N, [Fig. 2], is 6 in., and between O and P, 9 in. The bamboo is easily curved by wetting and holding it for an instant in the flame of a candle. It will hold its shape just as soon as it becomes cold. The wheels are made of tin, 1¹⁄₂ in. in diameter, borrowed from a toy automobile. The axles are made from wire, ¹⁄₁₆ in. in diameter.

The wing spars Q are made of spruce, ³⁄₁₆ in. wide and ¹⁄₄ in. thick. Those for the front are 30 in. long, and for the rear, 36 in. long. The ribs R are made of bamboo pieces, ¹⁄₁₆ in. square, 5 in. long for the front plane, and 6 in. for the rear. These are bound and glued on top of the spars, 3 in. apart. They are given a slight upward curve. The round ends are made of ¹⁄₁₆-in. rattan.

Fig. 1
The Motor Base is Made of Two Spruce Sticks Joined Together with Four Cross Sticks, Bound and Glued to the Under Side

It is rather difficult to make good propellers, but with a little time and patience they can be shaped and formed into good proportions. Procure two clear, straight-grained blocks of white pine, 8 in. long, 1¹⁄₂ in. wide, and ³⁄₄ in. thick. Draw a diagonal line on one block from opposite corners, as shown at S, [Fig. 3], then on the other block T, draw the line in an opposite direction. Turn the blocks over and draw opposite diagonals, as shown by the dotted lines. Draw a circle on each side exactly in the center, ¹⁄₂ in. in diameter. Drill ¹⁄₁₆-in. holes through the centers of the circles for the propeller shafts. The wood is then cut down to the lines drawn, leaving only enough material so that they will not break easily. The face of the blades should be flat and the back rounded. Leave plenty of stock near the hub. After the faces have been finished, the blades are shaped as shown at U. The propellers should be finished with sandpaper to make them perfectly smooth, as much of the success of the model will depend upon them. It will be a good plan to shellac them, and also the frame and the alighting gear. Aluminum paint costs but little, and it makes a fine finish for a model aeroplane.

The propeller shafts V, [Fig. 1], [2], and [4], are cut from bicycle spokes. An eye for the rubber band is bent in the spoke, about 2 in. from the threaded end. The end having the threads is run through the bearing block C, [Fig. 4], and the propeller fastened on with a small washer on each side of it by means of two nuts, W, cut from a bicycle nipple. These nuts may be turned up tightly with pliers.

The planes are covered with tissue paper put on tightly over the tops of the ribs, using a flour paste. The planes are movably fixed on the motor bases A by tying at the four points of contact with rubber bands. This makes it possible to adjust the fore-and-aft balance of the machine by changing the position of the planes.

The motive power, which is the most important part of the entire machine, consists of rubber bands. There are three ways of obtaining these bands. It is best, if possible, to purchase them from an aeroplane supply house. In this case, procure about 100 ft. of ¹⁄₁₆-in. square rubber, 50 ft. for each side. These are wound closely between the hooks X. This rubber can be taken from a golf ball. It will require about 40 strands of this rubber, which is removed by cutting into the ball, on each propeller. Another way of obtaining the bands is to purchase No. 19 rubber bands and loop them together, chain-fashion, to make them long enough to reach between the hooks without stretching. About 30 strands on each propeller will be sufficient. The hooks X are made in the shape of the letter “S,” to provide a way for taking out the rubber bands quickly. To prevent the hooks from cutting the rubber, slip some ¹⁄₁₆-in. rubber tubing over them. The rubber bands, or motor, when not in use, should be kept in a cool, dark place and powdered with French chalk to prevent the parts from sticking together.

Fig. 2
The Alighting Gear is Made Entirely of Bamboo and Attached to the Under Side of the Motor Frame

With the model complete, flying is the next thing in order. With a machine as large as this one, quite a field will be necessary to give it a good flight. Test the plane by gliding it, that is, holding it up by the propellers and bearing blocks on a level with your head and throwing it forward on an even keel. Shift the planes forward or back until it balances and comes to the ground lightly.

Winding up the propellers is accomplished by means of an eye inserted in the chuck of an ordinary hand drill. While an assistant grasps the propellers and motor bearings the rubber is unhooked from the front of the machine and hooked into the eye in the drill. Stretch the rubber out for about 10 ft., and as it is wound up, let it draw back gradually. Wind up the propellers in opposite directions, turning them from 400 to 800 revolutions. Be sure to wind both propellers the same number of turns, as this will assure a straight flight.

Fig. 3
The Most Difficult Part of Making the Propellers can be Overcome with a Little Patience

Set the machine on the ground and release both propellers at once, and at the same time push it forward. If everything is properly constructed and well balanced, the mechanical bird will run about 5 ft. on the ground and then rise to 15 or 20 ft. and fly from 800 to 1,200 ft., descending in a long glide and alighting gracefully.

Fig. 4
The Motive Power, Which Is the Most Important Part of the Machine, Consists of Rubber Bands

If the machine fails to rise, move the forward plane toward the front. If it climbs up suddenly and hangs in the air and falls back on its tail, move it toward the back.

After the novelty of overland flights has worn off, try flights over the water. To do this the wheels must be removed and four pontoons put in their place, as shown by the dotted lines in [Fig. 2]. The pontoons are made over a light frame, constructed as shown in [Fig. 5]. The frame pieces are bamboo, ¹⁄₈ in. square. Each one is 8 in. long, 4 in. wide, and 2 in. deep. The covering consists of writing paper glued in place, after which the whole surface is covered with melted paraffin to make it water-tight.

Fig. 5
Framework for Constructing Pontoons by Covering Them with Writing Paper Soaked in Paraffin

No doubt various methods will be suggested by the time such flights are made, such as smaller planes for racing, larger ones for altitude and duration, etc. To make the machine carry weights, build a duplicate set of planes and fasten them 6 in. above the others by means of struts, ³⁄₁₆ in. square, forming a tandem biplane, as shown by the dotted lines in [Fig. 2].

Patience is the one thing necessary in model budding. Sometimes a machine carefully made will not fly, and no one can make it do so until some seemingly unimportant alteration is made.