the vaporization of a liquid extracts heat from the gas or air in which the vaporization takes place, so that if we start with cold air it becomes still colder by the time it has taken up the gasoline spray. If the original air temperature is low enough the result of the chilling action of the gasoline may easily result in the latter being thrown down in the manifold and cylinder in liquid form, and in such a case it is only the lighter fractions in the gasoline that mix with the air and give an ignitable gas. Often in actual fact it is the heat generated by the compression of air in the engine that causes the deposited gasoline to vaporize and this sometimes explains why a motor will start after repeated spinning following injection of raw fuel. Since the modern car has always plenty of electricity available it is a natural enough idea to utilize some of it for heating up the air to be used for starting purposes, and one of the neatest devices having this end in view is the Paul preheater, illustrated at A, Fig. 285. This is a section through the apparatus which is intended to be inserted in the middle of the hot-air pipe of the carburetor; the split ends of the preheater in conjunction with the cap nuts enable it to be gripped on flexible pipe if desired, so attachment is easy. Inside the chamber there is a coil of flat metal strip having a fairly high resistance, and the ends of this strip are fixed to the two terminals shown. A wire is run from the cranking battery to one of these terminals, and the return wire passes through a switch which can conveniently be located in the cowl. To use the heater it should be switched on about half a minute before cranking and the carburetor primed in the usual way. As soon as the motor starts, the exhaust pipe heats up and there is no more need for the preheater, so it can then be switched off. Automatic Safety Switch. Fuses in an automobile lighting circuit are always a possible source of trouble, though they happen very seldom. Their purpose is to prevent the wires in the circuit from being overloaded and they are a great safeguard. The trouble comes when some accident causes a short circuit, a rush of current and a "blow." It is then necessary to replace the fuse by a new one, after locating and curing the fault. Thus spare fuses have to be carried, as it is extremely dangerous to cut out a fuse by wiring it up with a bit of copper as is often done in emergency when no spare fuse is available. The Hartman automatic switch at Fig. 385, B, is a simple mechanical device which automatically switches off any circuit if the current in it exceeds the safe amount. It is operated by a small electro-magnet that pulls the contacts apart directly the current becomes too strong. Thus it is as effective as the fuse, while no part of it burns out to give the break in the circuit. All sorts of units are made from a single switch to gang switches that can control every circuit on a car. Lighting Gas by Electric Spark. Many automobiles are in use that are not equipped with electric lighting systems, and in which stored acetylene gas is employed for the headlights. An electric lighter which may be used to light the burners without the driver leaving the seat is clearly shown at Fig. 286. This is a type which robs the engine of a spark for an instant while the gas is being lighted, a push button on the dash diverting the high tension current from a secondary wire to the sparking points in the headlights. The gas regulation is very simple, no automatic reduction valve being necessary. A small, high pressure tube leads om the gas tank to a control valve and a regulating valve on the dash, the former being beside the push button to open or close as desired, while the regulating valve is on the engine side of the dash, and is set as desired for securing the proper pressure at the burners. Low Voltage Electric Vulcanizers.-The Premier is an electric vulcanizer weighing but two pounds and is shown at Fig. 287. This device operates from the 6-volt storage battery usually carried in the car and is provided with a thermostat which automatically cuts off the current as soon as the vulcanizer attains the correct heat for vulcanizing the repair on shoe or inner tube. It will take any size tire Burners Gas Line Gas Tank. Fig. 286.-How Acetylene Gas May Be Ignited by Electric Spark. in quickly healing up small cuts in casings as soon as discovered, thereby preventing moisture from working in and rotting the fabric. The thing which keeps most motorists from doing their own repairs to punctured air tubes, is the trouble of the process, but the electric type of vulcanizer certainly helps to minimize this. One of the simplest, lightest and smallest machines is the Corbett & De Coursey shown at the right in Fig. 287, which also works off any six volt storage battery and so allows repairs to be made on the road. It should be quite easy to vulcanize a tube while running the car, as the vulcanizer is so light that it could be held by any passenger without fatigue. With the machine is a thermometer which allows the temperature to be controlled, and also a length Fig. 287.-Simple Electric Vulcanizers Operating on Storage Battery Current. of flexible wire furnished with a socket to fit the usual inspection lamp holder on the dashboard. Simple Rectifier.-The Westinghouse vibrating rectifier shown at Fig. 288 is a compact and simple device invented for charging Fig. 288.-The Westinghouse Rectifier for Charging Storage Batteries From Alternating Current. 6-volt batteries from al- |