The Holmes rotative engine, 7-cylinder 35 horse-power, weighing 160 pounds.
An American engine built in Chicago, Ill.
Other peculiarities of the gasoline motor affect considerably its use for aeroplanes. The continual and oft-repeated explosions of the gaseous mixture inside of the cylinder generate great heat, and this not only interferes with its regularity of movement, but within a very brief time checks it altogether. To keep the cylinder cool enough to be serviceable, two methods are in use: the air-cooling system and the water-cooling system. In the first, flanges of very thin metal are cast on the outside of the cylinder wall. These flanges take up the intense heat, and being spread out over a large surface in this way, the rushing of the air through them as the machine flies (or sometimes blown through them with a rotary fan) cools them to some degree. With the water-cooling system, the cylinder has an external jacket, the space between being filled with water which is made to circulate constantly by a small pump. In its course the water which has just taken up the heat from the cylinder travels through a radiator in which it is spread out very thin, and this radiator is so placed in the machine that it receives the full draught from the air rushing through the machine as it flies. The amount of water required for cooling a motor is about 1⅕ lbs. per horse-power. With an 8-cylinder 50 horse-power motor, this water would add the very considerable item of 60 lbs. to the weight the machine has to carry. As noted in a previous chapter, the McCurdy biplane has its radiator formed into a sustaining plane, and supports its own weight when travelling in the air.
The 180 horse-power engine of Sir Hiram Maxim; of the “opposed” type, compound, and driven by steam.
The Anzani motor and propeller which carried M. Bleriot across the English Channel. The curved edge of the propeller blades is the entering edge, the propeller turning from the right of the picture over to the left. The Anzani is of the “radiant” type and is of French build.
It is an unsettled point with manufacturers whether the greater efficiency (generally acknowledged) of the water-cooled engine more than compensates for the extra weight of the water.
Another feature peculiar to the gasoline motor is the necessity for such continual oiling that it is styled “lubrication,” and various devices have been invented to do the work automatically, without attention from the pilot further than the watching of his oil-gauge to see that a full flow of oil is being pumped through the oiling system.
The electric current which produces the spark inside of the cylinder is supplied by a magneto, a machine formed of permanent magnets of horseshoe form, between the poles of which a magnetized armature is made to revolve rapidly by the machinery which turns the propeller. This magneto is often connected with a small storage battery, or accumulator, which stores up a certain amount of current for use when starting, or in case the magneto gives out.
