Page:Popular Science Monthly Volume 91.djvu/151

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A Boomerang Flyer

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��A LITTLE gyroscopic flyer which can be adjusted so it will return like a boomerang can be made by any intelligent boy. Excepting the shaft, every part can be made with such simple tools as a jack-knife, a pair of pliers and a hammer. The only outside work required is the boring of two small holes in the shaft. This a watchmaker or jeweler will do.

The flyer may be made any size, but as the power which is available must be con- sidered, the following dimensions are sug- gested: The disk A should be 10 in. in diameter made of a thin tar board, for this material is absolutely flat and does not warp or twist out of shape. Aluminum is also serviceable. Unlike the common glid- ers, lightness is not the first consideration. On the other hand, weight is of con- siderable importance, as the ability of the device to soar depends on the momentum of the disk itself. In using aluminum, No. 28 gage is the best thickness.

Centrally in the disk is a hole to receive a 3/16-in. steel rod B, 4 in. long. Exactly in the center the rod is bent at right angles so that each part, B and C, is 2 in. long. The part C is bent laterally, at a point midway, as shown at D, so that it will lie flat on the disk, and an end E is turned up so it will serve as a crank handle. The object of this arrangement is to provide a means whereby the disk can be rigidly fixed to the stem so the plane of its surface will be maintained perpendicular to the stem B.

After the stem B is placed in the central

��hole of the disk, wire staples F may be used to fasten it firmly, as shown. Through the stem portion B two small holes G are drilled Yi in. apart, to receive a bent pin or wire H, which provides a means for attaching a rubber band.

The body of the flyer is made of a strip of pine /, g}/2 in. long, 1 in. wide and % in. thick. The interior portion of this strip is cut away to form an upper and a lower bar. The forward end is tapered off to form an A-shaped edge, while the rear end has a blade /, made of thin aluminum 2 in. long by i}/2 in. wide, to serve as a rudder. The metal should be thick enough to remain set after bending in either direction.

A hole is bored vertically through the upper and lower bars of the frame to receive the stem B. A short tube K, % in. long, is placed on the stem between the disk A and the upper edge of the strip /, and a thin washer L is placed between the pin H and the lower side of the upper bar. By this means the stem B is held rotatably fixed to the frame.

The rubber band M which serves as the motive power, should be 4 in. long by J/£ in. wide, a size easily obtained. The rear end of this elastic is secured to the side of the strip / by means of a wire staple N.

If the elastic band is wound up and the flyer thrown into space it will sail along with remarkable evenness of flight, due to the gyroscopic action of the rotating disk. The propelling device consists of a pair of triangular-shaped blades, 0, secured to the opposite ends of a light wire rod P. This rod has at each end a projecting right- angled bend Q, to which the blades are attached.

Each blade has at its rear margin a downwardly-projecting and rearwardly- extending finger R, which passes through a slit in the disk A. These fingers have two functions; first, to hold the propelling mechanism in place, and second, to rock the wire rod P back ^id forth. The

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