Ballonets.—There are two ballonets, one at each end, each having a capacity of 10,596 cubic feet. The material in the ballonet weighs about 8¼ ounces per square yard, the cotton layers being lighter than in the material for the gas bag. Air is pumped into the rear ballonet before leaving the ground, so that the air ship operates with the front end inclined upward. The air striking underneath exerts an upward pressure, as on an aëroplane, and thus adds to its lifting capacity. Air is pumped into the ballonets from a fan operated by the motor. A complex valve, just under the middle of the gas bag, enables the engineer to drive air into either, or both ballonets. The valves also act automatically and release air from the ballonets at a pressure of about 0.9 inches of water.
In the middle of the top of the gas bag is a valve for releasing the gas. It can be operated from the car, and open automatically at a pressure of about 2 inches of water. Near the two ends and on opposite sides are two rip strips controlled from the car by the cords.
Suspension.—The suspension is one of the characteristics of the air ships, and is protected by patents. The car has four trolleys, two on each side, which run on two steel cables. The car can run backwards and forwards on these cables, thus changing its position with relation to the gas bag. This is called “loose” suspension. Its object is to allow the car to take up, automatically, variations in thrust due to the motor, and variations in resistance due to the air. Ramifications of hemp rope from these steel cables are sewed onto a canvas strip, which in turn is sewed onto the gas bag. This part of the suspension is the same as in the Drachen balloon. The weight is distributed over the entire length of the gas bag.
The Car.—The car is 16.4 feet long and is built of steel tubes and wire. It is large enough to hold the motor and three men, though four or five may be taken.
Motor.—The motor is a 110-horse-power Daimler-Mercedes. Sufficient gasoline is carried for a run of twelve hours.
Propeller.—The propeller, like the suspension, is peculiar to this air ship and is protected by patents. It has four cloth blades which hang limp when not turning. When the motor is running, these blades, which are carefully weighed with lead at certain points, assume the proper position due to the various forces acting. The diameter is 13¾ feet. The propeller is placed above the rear of the car near the center of resistance. Shaft transmission is used. The propeller makes 500 r. p. m. to 1,000 of the motor. There is a space of 6½ feet from the propeller blades to the gas bag, the bottom of the car being about 30 feet from the gas bag. This propeller has the advantage of being very light. Its position, so far from the engine, necessarily incurs a great loss of power in transmission.
The steering wheel at the front of the car has a spring device for locking it in any position.
The 1908 model No. 1 of this air ship was constructed for the purpose of selling it to the government. Among other requirements is a 12-hour flight without landing, and a sufficient speed to maneuver against a 22-mile wind. A third and larger air ship of this type is now under construction.
United States
Signal Corps Dirigible No. 1