Spark Plug Cleaning.—To insure a smooth running motor and a good spark, the spark plugs should be cleaned at thirty day intervals. It is not always necessary to disassemble them at this time as the carbon usually collects and bakes on the metal casting shell and can be removed by running a thin knife blade or finger nail file around the inner surface. However, when the insulator becomes pitted or carbon burnt the plug should be disassembled and the insulator wiped clean with a cloth dampened in kerosene. Never immerse the insulator in kerosene, as this will loosen the cement around the center electroid and cause the plug to leak compression. The shell may be immersed. It is then wiped dry and the inside surfaces scraped or rubbed with a piece of sand or emery paper to dislodge the carbon pits. After all parts have been thoroughly dried the plug is reassembled, using new washers.
CHAPTER XXVIII
CLUTCH CONSTRUCTION, TYPE AND CARE
The clutch used in automobile construction of the present day becomes a necessary part of the equipment upon the adoption by manufacturers of the progressive and selective types of sliding gear transmissions.
When the engine is started the clutch is “in,” that is, in contact with the flywheel, and all parts of the clutch revolve with it at the same speed. The shaft on which the clutch is mounted extends into the transmission gear case, but as the transmission gears are in a neutral position, the movement of the car is not affected.
When the car is to be started the clutch foot pedal (usually on the left side of the steering column) is pressed down. This throws the part attached to the drive shaft out of contact with the part attached to the flywheel, and in its backward movement it comes into contact with the clutch brake, as shown in [Fig. 105], which stops it from revolving. The hand gear control lever is shifted into the first speed slot or position. The pressure on the foot pedal is then gradually released and the clutch is carried in by spring tension, and the car moves off at first speed.
Second Speed.—The clutch is thrown “out” after a brief lapse of three to five seconds has been allowed for the brake to slow up rotation in order that the gears to be meshed will be rotating at the same speed. The hand control lever is now shifted into the second speed slot, and the clutch pedals released.
High Speed or Direct Drive.—The clutch is thrown out and a few seconds allowed for it to slow up. The hand control lever is shifted into the high speed slot, which connects the drive or propeller shaft directly to the clutch shaft and the car is driven at crank shaft speed when the clutch is let in.
Reverse.—The clutch is employed in the same manner. However, the motion of the car, the clutch and all gears must be at a stand still before the gear control lever is shifted to the reverse speed slot, as the gears in the transmission operate in the opposite direction.
Fig. 105. Cone Clutch and Brake