Engineering Wonders of the World
Volume III

DIRIGIBLE BALLOONS. 61 German dirigible, Pars eval I., appeared in 1906. It had a hemispherical prow and a conical stern. Two air ballonets The , , . . _ , are used, one at each end; to Pars eval. control the longitudinal trim of the gas chamber. For ascending, the rear ballonet is filled and the front ballonet emptied, throwing the centre of gravity of the gas for- with lead. When at rest the blades hang limp, but are stiffened by centrifugal force when revolving. Weight is reduced considerably by this system of blading. Larger and more efficient Parsevals were built in 1908 and the present year. Parseval II. is 58 metres long, has a volume of 3,800 cubic metres, and carries a 114 horse-power engine. ■- GROSS II.,” THE GERMAN SEMI-RIGID MILITARY AIRSHIP, IN FLIGHT. (Photo, Topical.) in general outline it closely resembles the Parseval, but is distinguished by the girder keel from which the car is suspended. This ship was used during the German army manoeuvres of September. ward, and causing the prow to rise and give the under surface of the bag somewhat of an aeroplane effect. For descending the process is reversed. Two other interesting points are the car suspension and the propeller. The car has two pulley wheels on each side at the floor level, round which pass steel cables to the ropes distributing the weight over the whole length of the gas-bag. This arrangement allows the car to adjust its position in accordance with variations of the screw thrust and air pressure. The propeller has four blades of cloth weighted Th© Gross I., launched in 1907, is a semi- rigid dirigible, with spherical prow and stern. The latest Gross has a volume of 5,000 cubic metres, and includes two air ballonets. The two 3-bladed Gfoss Airsh i os propellers revolve in the same direction. At the rear, horizontal planes are used for stability. We may note that the inventor, Von Gross, has abandoned the hemi- spherical in favour of the conical stern. In America the Baldwin airship has achieved considerable success, and has been adopted