Engineering Wonders of the World
Volume III

DIRIGIBLE BALLOONS. 49 SEVERO’S DIRIGIBLE BALLOON (1902)'. The propeller shaft was mounted at the axis of the balloon to give a direct thrust. Two small propellers at the ends of the car were used for lateral steering; a single propeller at the stern for vertical steering. envelope a number of aero- planes, upon which, devolves part of the duty of raising the airship from the ground and keeping it aloft. This par- ticular airship is, in fact, not a true “ ship,” as it does not float by its own buoyancy. For lateral steering ono or more vertical rudders placed near the stern are used. in de of soon as it attained a certain speed. To ob- viate this tendency he attached horizontal, fin- like planes to the tail, a prac- Stability. tice which has been followed more recent designs. The French Ville Paris and Clément-Bayard have, instead planes, small ballonets, cylindrical in the first case, pear-shaped in the second. (See the illustrations on pages 58 and 57 respectively.) Pitching arises from irregularities in pressure and the presence of ascending or descending air currents, from the leakage of gas, and th© shifting of the dead or the live load. The lower the centre of gravity is kept the less will the pitching be. Movable weights for correct- ing the trim are used. On the Gross airship two ballonets—one forward and the other aft —are connected by a pipe through which air is transferred from one to the other to alter the buoyancy of either end. As Moedebeck remarks in his Handbook of Aeronautics, the maintenance of stability in long airships is one of the most difficult problems for the constructor. Vertical steering is effected by the aid of planes attached to the balloon or the body, and by altering the longitudinal trim. The Zeppelin airships carry sets of Steering. . planes tore and aft, which, it set at an angle of 15° to the horizontal, will at 31 miles an hour give a lifting force of nearly a ton, and enable a rapid ascent to be made without throwing away ballast. The French Malecot (see page 47) has under the (1,408) DEVELOPMENT OF THE AIRSHIP. The first airship to attain an independent velocity was that built by Henry Giffard, the inventor of the famous water injector now commonly used for steam boilers, in 1852. (Fig. 1.) It Guard’s was about 136 teet long and 37 feet in diameter, and had a capacity of 2,000 cubic metres. Its weight was 2,794 lbs., its lifting capacity 1| tons. The 3 horse-power steam-engine used to drive it weighed 462 lbs. —a striking contrast to the light but extremely powerful petrol engine of to-day. The car, containing the engine, was suspended from a horizontal rod to which the cordage of the envelope was attached. On September 24, Giffard made an ascent at Paris, and succeeded in obtaining a speed estimated variously at 4J and 6| miles an hour. Fig. 1.—giffard’s dirigible (1852). It was propelled by a three horse-power steam-engine, and attained a speed of about six miles an hour. 4 VOL. III.