The power exerted by your motor is meanwhile increased in direct proportion to the amount of rubber added. Still another advantage of this adjustment lies in the fact that such a motor will unwind to the first turn. In preparing a multiple-strand rubber, each strand must, of course, be twisted in the same direction and exactly the same number of times before being installed.
The builders of model aeroplanes may profit from the experience of the automobile tire manufacturers in studying the properties of the rubber used for motors. Rubber is at best comparatively short-lived. It suffers a surface deterioration on being exposed to the air, which in time affects the entire mass.
This process of decay goes on fastest in very warm weather and in very bright sunlight. It is believed that sea air and the rarified air of the mountains are bad for rubber. On the other hand, a very low temperature, as you may perhaps have discovered, robs the rubber of much of its elasticity.
It will pay you to take some trouble to protect the rubber strands as far as possible. Lay them away in a can or jar in some cool, dry and dark place when they are not in use. Some boys cover the rubber with powdered chalk. When the surface of the rubber begins to granulate, its best days are over. Rubber is originally white in color, while the refining process gives it the familiar gray tone.
The Para rubber is generally considered the best of the many kinds now on the market. As a rule, any oil or grease tends to decay the rubber, as any motorist can tell you. This is particularly unfortunate for the aviator, since the efficiency of the rubber motor is increased by slightly lubricating the strands. Many boys prefer to chance injuring their motors in order to gain the advantage of the oiled strands.
The strands thus prepared slide smoothly on one another and do not grip each other even when tightly wound. The simplest preparation for greasing the strands is a solution of ordinary soap and water. A few drops poured over the strands will suffice. When your motor unwinds, be careful to keep your face out of range, since a few drops might be flung into your eyes. Several preparations for lubricating the motors have been placed upon the market.
The direction flights may be controlled very easily by winding the motor. If you care to fly your model in circles or spirals, the simplest plan for influencing its direction is to give different power to your propellers. It often happens that a model must be in a restricted place, perhaps a straight-away flight is out of the question.
The model may be deflected to the right or left by the use of vertical propellers, but they require delicate adjustment, and a gust of wind may destroy their effect. By winding up one double the number of turns of the other, a circular flight is assured. To gauge the diameter of the circle merely alter the relation of the number of turns. You will soon find that you can control the diameter of the circle with remarkable accuracy.
A Motor Anchorage