The electric spark is a very effective igniter for the explosive mixture, and, by properly setting cam n the explosion can be made to take place just at the position of the piston that may be found the most desirable; but the points at i are liable to get out of order, and the battery that actuates the induction coil M and the coil itself can become a source of more or less trouble, and on that account the igniting is effected in some motors by means of a hot tube. When this is used the cam n, the lever l and the electrical parts of the apparatus are not required. In their stead a tube is placed on the upper side of the chamber Q and this tube is maintained at a red heat by means of a flame impinging against its outer surface. When the explosive mixture is compressed it rises in the interior of the hot tube, and when it reaches the portion that is hot enough to produce combustion an explosion takes place. By many engineers this arrangement is regarded as superior to the electric spark on account of its simplicity.
Gasoline motors are made with one, two or more cylinders, but in each cylinder the action that takes place is that described above. The actual construction of a motor is not so simple as might be assumed from the appearance of [Fig. 1]; many details are required which are not here shown. A more perfect idea of the actual construction of a gasoline motor can be had from [Fig. 2], which is a working drawing of a recent European invention. In this design it will be noticed that the cylinder is cooled by radiation into the surrounding air, the exterior surface being increased by numerous circular ribs and also by extending a hollow trunk from the upper side of the piston, so as not only to increase the radiating surface, but also to allow the hot air to escape from the chamber T in which the crank discs revolve. In this drawing E is the explosion chamber, corresponding to Q in [Fig. 1], and the valve s is the counterpart of f, while s’ corresponds to the valve h. The upper pipe t is the pipe e of [Fig. 1] and the lower pipe t’ is the pipe r of the same figure. Although the crank discs, connecting rods and other details are different in shape, it will readily be seen that their relation to each other is the same.
Fig. 3. Reversing Mechanism.
Since a gasoline motor cannot start of its own accord, it is necessary in vehicles in which they are used so to arrange the driving gear that the motor may be kept in motion all the time and always in the same direction, hence, to reverse the direction of the carriage, reversing mechanism, independent of the motor, must be provided. The most simple mechanism for a gasoline vehicle employing spur gearing exclusively is shown in diagrammatic form in [Fig. 3]. In this figure A represents the cylinder of the motor, B the crank disc chamber and M the vaporizing receptacle, which is generally called the carburator. The pinion C, on the end of the motor shaft, meshes into a gear D which is mounted upon a sleeve E which revolves freely round shaft G. This sleeve has its ends formed so as to engage with the gears mounted upon shaft G, and by means of a lever, which is not shown, but which works in groove a, the clutch either s or ss can be thrown into engagement with its corresponding gear. If s is thrown into gear, as shown in the drawing, the wheel F will turn H and the pinion I will rotate the gear J which is mounted upon the axle of the carriage. If the clutch ss is thrown into engagement, the gear G will turn K and this wheel will turn l; but, as can be clearly seen, the direction in which l will revolve will be opposite to its motion when driven through F and H, therefore, if when F drives the carriage runs forward, when G drives it will run backward, and when E is moved to the central position, so that neither s nor ss engages with their respective gears, the vehicle will stand still, but the motor will continue to revolve.
Fig. 4. Plan and Elevation of Underberg Motor Voiturette.
This diagrammatic arrangement is more simple than the gearing actually used and is not as complete in action as many of the devices, as it only provides means whereby the direction of rotation of the axle may be changed, while in many carriages the gearing also varies the ratio between the speed of the motor and the driving wheels. It is also quite common to combine in the train of gearing spur gears and sprocket wheels, and in some instances even belts. [Fig. 4] illustrates a French gasoline automobile made by Underberg, of Nantes. The first figure is a side view, and the second is a plan of the truck and driving mechanism.
Fig. 5. Cherrier Two-speed Gear.