Rotating Cylinder Motors. The first rotating cylinder motor in use was the American Adams-Farwell, a type that was soon followed by the better known French "Gnome." Other motors of this type are the Clerget, LeRhone, Gyro and Obereusel. They are all of the air-cooled type—cooled partly by the revolution of the cylinders about the crank-shaft, and partly by the propeller slipstream. While the pistons slide through the cylinder bore, the rotating cylinder motor is not truly a reciprocating type, as the pistons do not move back and forth in regard to the crank shaft. The cylinders revolve about the crank shaft as a center, while the pistons and connecting rods revolve about the crank pin, the difference in the pivot point causing relative, but not actual, reciprocation.
Hall-Scott 4-Cylinder Vertical Water-cooled Motor. 80-90 Horsepower.
The original Gnome motor drew in the charge through an inlet valve in the piston head. The gas passed from the mixer, through the hollow crank-shaft, and then into the crank-case. The exhaust valve was in the cylinder head. This valve arrangement was not entirely satisfactory, and the company developed the "Monosoupape" or "Single valve" type. The 100 H. P. Monosoupape Gnome has 9 cylinders, 4.3" x 5.9". The total weight is 272 pounds and the unit weight is 2.72 pounds per horsepower. It operates on the four-stroke cycle principle. The gas consumption is 12 gals. per hour, and it uses 2.4 gals. of castor oil. The cylinders and cooling fins are machined from a solid steel forging, weighing 88 pounds. The finished cylinder weighs 5.5 pounds after machining. The walls are very thin, probably about 1/16 inch, but they stand up well under service conditions.
Sturtevant "V" Type 8-Cylinder Water Cooled Aeronautical Motor. This Motor Is Provided With a Reduction Gear Shown at the Rear of the Crankcase.
Assuming the piston to be on the compression stroke, the ignition will occur from 15° to 20° before the top dead center. Moving down on the working stroke, and at 85° from top dead center, the exhaust valve begins to open, and the exhaust continues until the piston returns to the upper dead center. With the valve still open, pure air now begins to enter through the exhaust valve and continues to flow until the valve closes at 65° below the bottom center. Still descending, the piston forms a partial vacuum in the cylinder, until at 2° before the lower center the piston opens the ports and a very rich mixture is drawn in from the crank case. This rich mixture is diluted to the proper density by the air already in the cylinder, and forms a combustible gas. The upward movement of the piston on the compression stroke closes the ports and compression begins. The mixture enters the crank case through a hollow shaft, with the fuel jets near the crank throws. A timed fuel pump injects the fuel at the proper intervals.
Dusenberg 4-Cylinder Vertical Water Cooled Motor With Reduction Gear. Four Valves Are Used Per Cylinder. Note Peculiar Valve Motion.
Curtiss Motors. The Curtiss motors are of the water-cooled "V" type, with 6 to 8 cylinders per row. These are probably the best known motors in America and are the result of years of development, as Curtiss was the first to manufacture aero motors on a practical scale.