A very suitable method of mounting an electric motor is illustrated in [Figs. 44] and [45]. It will be noticed that the motor is inverted. A small pinion or gear is mounted upon the armature-shaft of the motor. A larger gear (about three times the diameter of the small one) is placed upon the propeller-shaft. This gives a speed reduction of three to one. It will be seen that the propeller-tube is strapped within a strip of brass to a small cross-piece nailed to the bottom board of the hull. The hull is of the built-up type, and the other three boards that go to make it up are not shown. When the three boards are glued in place, a brass strip is run across the top board and the base of the motor is screwed to this. This holds the motor rigidly in place so that it will not move when the power is turned on. The brass strip used should have sufficient thickness to hold the motor rigid. It will also be seen that the motor is tipped slightly so that it will come in line with the propeller-shaft.
It is not always possible to obtain small gears. For this reason the model boat builder may find it necessary to use a different method of fastening the propeller-shaft to the motor. A very good method of doing this is shown in [Fig. 46]. Here a coiled wire spring is used. This is wound to shape on a rod, and a drop of solder holds it to the propeller and motor shafts. In the method of propulsion shown in [Fig. 44] the armature-shaft of the motor must be perfectly in line with the propeller-shaft, or the gears will bind and unsatisfactory operation of the motor will result. With the little spring the motor will not have to be mounted exactly in line with the shaft, and it will also be possible to mount the motor standing up. Of course, if the motor is mounted in this way it will be necessary to make the propeller-shaft longer, as is shown in [Fig. 47].
Still another method of driving the propeller is illustrated in [Fig. 48]. This method is so simple that the author feels explanation to be unnecessary.
Clockwork can often be employed for propulsion purposes, but this method is not very satisfactory. It is also very difficult to obtain suitable clockworks to install in a boat. Oftentimes it will be possible to salvage the works of an old alarm-clock, providing the main-spring is intact. It is a very easy matter to mount the clock-spring and connect it to the propeller. Any one of the aforementioned methods can be employed.
Steam propulsion has its advantages; but, on the other hand, the writer is not inclined to recommend it as strongly as the electric method for reliability. Of course, steam is a more powerful agency in the propulsion of small boats and thereby greater speed is attainable by its use.