In the Gyro motor, made by the Gyro Motor Company of Washington, D. C., are embodied all of the principles of the typical revolving motor, but with extensive improvements in the design and in the details. It weighs 3¼ pounds per horse-power, complete. This light weight is due to the design of the motor and to the use of alloy steels, and is attained without sacrificing strength or durability. Each cylinder is machined out of a heavy 3½ per cent tubular nickle steel forging that weighs nearly 40 pounds. After the metal is removed and the cylinder worked down to size, the shell weighs but 6½ pounds. The radiating ribs on the outside of the cylinder are machined out of the solid bar, and are arranged in helicoid or screw-like formation around the cylinder barrel. This adds to the strength of the cylinder and also aids in the circulation of the air. The comparative thickness of the cylinder wall may be seen from Fig. 44. The stiffening effect of the radiating ribs will also be noted. The crank case to which the cylinders are fastened is of vanadium steel, and is divided into two parts. In addition to supporting the cylinders, the crank case also serves as a mixing chamber for the gasoline and air. By removing the bolts seen between each cylinder, the entire working mechanism can be laid bare for inspection. The exterior of the case carries the exhaust valve mechanism and the ignition distributer. The crank shaft is a nickel steel forging with an elastic limit of 110,000 pounds. It is bored hollow throughout its length and serves as an intake manifold by conveying the mixture from the carbureter, attached to its outer end, to the crank case. [Illustration: Fig. 45. Section Through Rotary Gyro Motor. ] The intake valves in the heads of the piston are mechanically operated by a specially patented movement which consists of two parts, a counter-balancing member, and an operating member. The counter balance balances the valve against the disturbing influence of the centrifugal force, while the operating member, which is fastened to the connecting rod, controls the opening or closing of the valve by the angular position of the connecting rod. This valve action insures a full opening of the valve and a full charge during practically all of the suction stroke.