Short Circuiting Faults.—A short circuit is one where the path of the current is from the lead to the return wire at some point between the battery, or source of electrical energy, and the coil or other mechanism which is to be operated by the electricity.
When this occurs the first thing is to examine the conductors and ascertain whether the insulation is intact. Sometimes the insulation becomes worn or frayed, and it is not infrequent for the ends of the wire, where attached to the binding post to spread out, where the conductor is made up of a lot of small wires, and some of them touch the metal alongside of the binding post.
Short Circuiting of Secondary Wires.—The secondary wires often cause short circuiting by lying too close to the metal of the engine or case. Great care should be observed to use the best insulated wire, and to see that they are free from dangerous contact.
Stranded cables are better for all wiring purposes, as vibration will not affect the screws which hold them at the contacts. A solid wire will cause a constant jar, and affect all connections.
CHAPTER XIII
AUTOMOBILE ACCESSORIES
Self-starting devices are the latest permanent addition to a perfect car equipment. Two general types are being made, one purely mechanical in its character, and the other operated by the engine itself.
The mechanical devices usually have some connection with the forwardly-projecting end of the crank shaft, where the present cranking shaft is located, and some of the inventions in this respect have an arrangement whereby the driver is able manually to operate the starter from his seat.
The actual work of turning the shaft is now performed by compressed air which actuates mechanism that gives from one to two turns to the shaft, sufficient to ignite the fuel in several of the cylinders.
Simple Type of Starter.—The simplest type of starter is that which utilizes the cylinders themselves to give the initial turns. To illustrate the matter we have given some sketches of the engine cycle, in Fig. 95. The four positions of the piston in a four-cylinder engine are so placed that the spark cannot ignite the charge in either cylinder.
Cylinders 1 and 2 are descending, and 3 and 4 are ascending. The charge in 4 is partially compressed, but it must reach the position indicated by the dotted lines A before it can be ignited.