Gasoline-electric Trucks.—Of late some progress has been made in constructing a type of electrics in which a gasoline engine is used, that is connected up with an electric generator. The latter is used to charge a storage battery also mounted on the truck, and the storage battery supplies the motor.
The gasoline engine being connected with the electric generator is constantly in condition to charge the storage battery and may be set in motion, whenever the charge in the storage battery falls below a certain electro motive force. At other times the motor is at rest.
In this type the electric motor is connected with the axle of the vehicle, so that it is always ready for service whether the gasoline motor is running or not.
In the ordinary gasoline automobile it is essential that the motor must be maintained in service at all times, so that any derangement in that part of the system, which includes the mechanism intermediate the motor and axle, or the electrical devices, or the carbureter, means a dead car.
It is urged that by combining the two systems a much wider range of usefulness will be obtained, and practice shows such to be the case. It has, however, some defects, one of which is the great weight necessary to maintain the entire train of mechanism thus described.
The other disadvantage is the great first cost, although it is maintained that the decreased cost of maintaining the cars, while in use, is sufficient to warrant an increased cost in the selling price of the machines.
It is undeniably true that such mechanism means additional care, and is liable to add to the complications necessary to operate the system, and it is obvious that these considerations will prevent the use of this type in all small vehicles, whereas it may be most serviceable and available in heavy trucks for transporting merchandise.
The Current Used.—Storage batteries are charged with and use a direct current. The difference between a direct and an alternating current is, that in the first the current flows continuously over a wire in one direction, whereas in the latter it changes its direction, going, for an instant, from the north pole to the south pole, and the next instant from the south pole to the north pole, and for this reason it is said to alternate.
Mechanically-produced electricity.—The alternating method is the natural form of flow in a current derived from mechanism, as, for instance, by means of a rotating armature.
The electricity, in this case, is produced by a metallic body moving through a magnetic field, and as it passes through it takes up a certain electric impulse in one direction when the body approaches the field, and instantly reverses and flows in the opposite direction as the body recedes from the magnet, or field.