Engineering Wonders of the World
Volume III

AERONAUTICAL ENGINES. 33 auxiliary ports in the cylinder walls, uncov- ered by the piston at the end of the stroke. The engine develops 25 horse-power, and has Fig. 5.—“ GNOME ” REVOLVING SEVEN-CYLINDER ENGINE ATTACHED TO PROPELLER, WHICH IT CARRIES ROUND WITH IT. This engine develops 50 h.p., and weighs only 160 lbs. Mr. Henry Farman used a “ Gnome ” for his record flight of 112 miles at Rheims. {Photo, Topical.) the merit of being extremely compact. Motors of this type are fitted to several Blériot machines. (Fig. 4.) We now come to a very interesting class, the five and seven cylinder star-shaped en- gines, with cylinders radiating at equal dis- tances from the circumference of a central crank-case. The advantage of an odd number of cylinders thus arranged is that it gives explosions at equal distances in continuous sequence. Thus, the firing order of the cylin- (1,408) ders of a seven-cylinder engine is 1, 3, 5, 1, 2, 4, 6, 1, 3, 5, etc. In the case of six cylin- ders, arranged in star fashion, there must either be a 1, 2, 3, 4, 5, 6 sequence of ex- plosions during one revolution, and no explo- sions during the next, or the explosions must occur at irregular intervals : 1; 3, 5, 2, 4, 6, 1, 3, 5, etc. SEVEN-CYLINDER ENGINES. A seven-cylinder engine which has proved very successful, and, was used on two of the Farman and one of the Voisin machines at the Rheims meeting, is the “ Gnome ” (Fig. 5). A peculiarity of this engine is that the cylin- ders and crank-case revolve round a fixed crank-shaft, from which the pistons get a push- off. Their rapid motion through the air cools the cylinders sufficiently without the aid of water circulation—which would be difficult to arrange on a rotary engine—and renders a fly-wheel unnecessary. This last feature means a considerable saving of weight. In this engine Fig. 6.—THE SEVEN PISTON RODS AND COMMON “ BIG-END ” OF A “ GNOME ” ENGINE. Quo of the seven rods is integral with the big-end. The other six work on pins passing through it. VOL. III.