In Europe no such prejudice existed, and consequently the type made rapid strides, although, to the writer’s belief, the European model is inferior in many ways to the original American type. The fact that this type of motor holds practically all of the world’s aviation records speaks for its practicability in spite of its unusual construction.
With the rotary motor, the cylinders and crank case revolve about a stationary crank shaft, the latter part not only serving as a point of reaction of the cylinders but as a support and intake pipe as well. Since the crank throw remains stationary, the cylinders and pistons revolve about two different centers, the cylinders revolving about the crank case and the pistons and connecting rods about the crank pin. Since the pistons, cylinders, and connecting rods must necessarily revolve together, as one unit, there is absolutely no reciprocating motion in regard to the crank shaft except for a very slight movement due to the difference in angularity of the connecting rods. The motion of all the parts is strictly rotary in every sense, except for the relation of the pistons to the cylinders, and the motion is as continuous as in a turbine. This insures freedom from vibration. As the cylinders and crank case have considerable inertia there is no need of the added weight of a fly-wheel. The movement of the piston in the cylinder bore is brought about by the difference in the centers about which these parts revolve. This gives cylinder displacement without the reversal of stresses or shock or jar.
Because of the revolving cylinders, the mixture is supplied to the crank case through a hollow shaft, the gas being drawn into the cylinder on the suction stroke through an inlet valve placed in the head of the piston. As a rule, the exhaust is direct to the air through the exhaust valves and without manifolds or mufflers. The motion of the cylinders through the air multiplies the efficiency of the radiating Fins.
(55) The Gyro Rotary Motor.
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.
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.
There are two separate paths provided for the exhaust gases, one being through the auxiliary exhaust ports at the end of the stroke, and the other path through the exhaust valve located in the cylinder head. The auxiliary ports may be seen in the cross-section directly below the piston head in cylinders 4 and 5. The auxiliary ports are uncovered by the piston at the inner end of the working stroke, and it is at this point that the greater percentage of the exhaust leaves the cylinder. These ports or holes are formed on a projecting annular ring in which enough material is provided to make up for the strength lost by boring the ports. As these ports are, in the majority of cases, bored at an acute angle with the center line of the cylinder, it is impossible for the cylinder oil to escape.