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Page:Popular Science Monthly Volume 57.djvu/614

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POPULAR SCIENCE MONTHLY.

power of the motor, which is located under the seat, is transmitted through friction wheels. In looking at the illustration it will be noticed that the hind wheels have a circular rim attached to the inner side, and of a diameter somewhat smaller than the wheel itself. Two small friction wheels are placed so that either one may be pressed against the inner surface of this rim. The 'shape of the rim, as well as that of the small wheels, is such that they hug each other firmly, so that the rim is carried around in a direction which corresponds with the direction of rotation of the friction wheel. In operating the carriage the motor is set in motion, and then one or the other of the two friction wheels is pressed against the rim on the driving wheel, according to whether it is desired to run forward or backward. While this arrangement might not operate with entire success if applied to a heavy vehicle, it appears to be all that could be desired for a light carriage.

Three-wheel vehicles have been used, but there is a difference of opinion as to their value, as the construction has disadvantages as well as advantages. It is evident that such a vehicle can be steered with greater ease than one running on four wheels, but on country roads, where the wagon wheels roll down a smooth surface, and leave the space between in a rough condition, it is equally evident that the third wheel, in passing over this uneven surface, would jolt the vehicle to a considerable extent. On a smooth pavement the three-wheel vehicle will run fully as well as the four-wheel; but, on the other hand, on such a pavement the latter can be steered with as little effort as the former, so that the question of superiority of design is one that probably depends upon individual taste.

From the descriptions of automobiles given in this and the two preceding articles, it will be seen that although many of them are used, especially in France, they are not entirely free from objectionable features. The electrical vehicles are provided with the most simple and durable machinery, and, being noiseless, odorless and free from smoke, are all that could be desired in so far as their operation is concerned; but they are heavy and can only be used in places where the batteries can be recharged. The steam vehicles are light, have simple mechanism and can run anywhere; but they exhaust steam into the air, which is clearly visible in cold or wet weather, and the heat from the engine and boiler is an objection, at least in summer time. The gasoline vehicles run well, but are noisy, and the odor of the gasoline is disagreeable as well.