All About Engines

220 All About Engines And if, in this confined space, something goes wrong, so that this energy is not exerted through its proper channels, serious damage will be done. The Motor-cycle Engine The motor-cycle engine differs in no important respect from those which have been described save that water cooling is unnecessary. The cylinder is provided with fins, and is exposed freely to the air. The rapid motion of the machine has the same effect as a strong current of air blowing over the surface and carrying away heat as fast as it is produced. Not only is the cylinder lighter than one provided with water jackets, but tank, radiator, and a not in- considerable amount of piping are rendered un- necessary, reducing both weight and cost of the machine. The more powerful machines are provided with double-cylinder engines, and these are arranged either opposite to one another or in the form of a V. The latter form is more economical of space and is the most frequently adopted. Two-stroke engines are very popular because of their simplicity, and the reduction of weight which results from the absence of admission and exhaust valves, tappets, and cam shaft. All single-cylinder engines have a crank con- sisting of a crankpin fixed between two solid fly- wheels, this, again, economising weight and space. The tank for fuel and lubricating oil is carried under the top bar, so that both can flow to the engine by