The wheels on some of this year's models are formed of wire disks covered with silk. The weight of these wheels is practically nothing, and they add much to the appearance of a well-finished model. Wire disks which may be covered in this way may be bought from the supply houses. It requires rather a skilful hand to shape the wire into perfect circles which will run easily. The covering again is a very nice operation. The silk wheel is not recommended for the beginner; but for one who is anxious to finish his model to the last detail as attractively as possible, they form an interesting feature.
Ping-pong balls make serviceable skids. Since they are carefully rounded, they will turn easily. To mount them, drill a hole for the wire shaft or axle, taking great care to have it pass through opposite points of the sphere. The wire may then be bent above it and attached to the skid. The celluloid turning on the wire axle produces practically no friction, and the ball offers very little resistance to the air. The balls are, of course, extremely light and add little to the weight of the model.
By combining the skid and wheel form of support, your model will gain the advantage of both these devices. The general form of the Farman skid may be followed. The skid in this case should be fairly heavy, strong enough to hold its shape, although elastic enough to take up a considerable shock. The simplest plan is to connect the two skids by a cross piece, and use this as the axle for two small wheels, mounted on the outside of the skid. This plan enables the aeroplane to rise with the minimum amount of resistance and land at the end of a flight with protection.
In the collapsible skid we find one of the most interesting novelties of the year. This ingenious mechanism, which is very easy to adjust, and which is placed under the front of the model on rising from the ground, is drawn into a horizontal position extending out before the machine and acts as a buffer, an aerial cow-catcher. Any simple form of skid may be adjusted in this way. The upper end or ends are merely fastened to the motor base so that they will swing easily back and forth. From a point half way down the skid, a rubber band is run to the front end of the motor base. When the model is set on the ground, after winding up, the skid is pulled back to form the forward support. It will be found necessary to adjust it to stand at a trifle less than the vertical. The rubber bands must be just strong enough to permit the skid to stand in this position when held down by the weight of the machine. As the machine rises, the skid is, of course, released and instantly snaps up to a horizontal position.
A new interest is lent to model aeroplane building by mounting them on pontoons contrived to float them on the water. Several large men carrying machines have risen from the water, notably the Curtiss model. It is believed by some aviators that since the water offers less friction than the earth or than a wooden runway, it is easier to rise in this way.
The builders of modern aeroplanes have been quick to adopt this idea. The models are mounted on miniature pontoons, and after winding up the motors are released in the usual way. An actual photograph of a model thus mounted in the very act of rising clear on the surface of the water is reproduced as a frontispiece of this volume. The pontoons, it will be noticed, consist of two small pieces of board, placed almost directly beneath the planes. The model is mounted on these pontoons by ordinary skids of reed. The angle of the planes with the surface of the water is the same as in the ordinary mounting. The pontoons are kept as small and light as possible.
To start the machine, the propellers are wound up in the usual way. It has been found that a model would rise rather more quickly from the water than from the land or within a few feet. As our photograph shows, the pontoons leave a slight wake behind them in the water. Once started to rise, however, the machine rapidly gains its elevation. One advantage of the pontoon skid flying over the water is the safety it insures on landing. At the end of such a flight the model drops into the water, but with little danger of breaking any of its parts. It will be found interesting to experiment in mounting the model loosely on pontoons, so that when it rises it will leave them behind, thus doing away with the increased load.
CHAPTER XI GEARED MOTORS
A MORE accurate control may be gained over a strand motor by using gear wheels. Both their speed and duration may be increased indefinitely. The gear will restrain a powerful motor from "racing," acting much the same as the governor of an ordinary engine. Still another advantage is the steadiness they insure to a machine in flight by cutting down the vibration.
The geared wheels and the frames for mounting them will be found to add very little weight, and they make possible a saving of rubber in the motor which renders such equipment no heavier than the ordinary direct-drive motor. Gears may be installed upon any ordinary motor base. Here is a fascinating field for experiment.