CHAPTER X
COOLING SYSTEMS
Proper cooling is a necessary feature of all gasoline motors, otherwise the intense heat of the burning fuel would expand the pistons to such an extent as to prevent their free motion in the cylinders, as well as destroy the spark plugs, injure the springs, and make lubrication a difficult matter, if not impossible, by burning up the oil.
Air Cooling.—Cooling was originally obtained by using air, which was blown against the cylinders; but this was not generally developed to a satisfactory degree except for small motors.
Air does not take up heat readily, whereas water is the greatest absorbent known, and in the primary stages of the art water was objected to on account of its weight, and for the further reason that the jacketing of the engine was considered a needless expense.
One of the best known devices to increase the cooling capacity with air cooling, and now largely used in motorcycles, is to provide the cylinders with a plurality of thin broad ribs, annularly-disposed, as shown in Fig. 72a.
Fig. 72a. Increasing Cooling Area.
Air-Cooling Devices.—A highly-heated metallic surface actually repels such a subtile fluid as air, hence it is necessary to supply the cylinders with a blast of air, and also provide a greater cooling area, so that if the ribs themselves can be cooled, the temperature will be decreased in proportion to the enlarged surface thus provided.
In using water this artifice is not necessary, because it will absorb heat instantly along the surface in contact with the metal, and quickly change the heated particles in favor of the cooler portions.
Water Cooling.—While heat will cause a circulation of water in a definite direction, for the foregoing reason, it has been found that, in practice, it is more practical to keep up the movement by mechanical means.