The New Student's Reference Work/Screw-Propeller

Screw-Propel′ler, a wheel with two or more radial blades in the form of a helix or spiral, used to propel a vessel. In modern ocean-steamers, there generally are two propellers, one on each side of the keel. The action of the propeller is similar to that of a screw revolving in a fixed nut, the water being more or less fixed as regards the revolving propeller. The screw-propeller was suggested by Bernouille of France in 1752, and in 1801 John Stevens of Hoboken, N. J., made a successful experimental boat with a screw-propeller. But it was not until between 1835 and 1840 that it began to come into general use. Its practical use was then demonstrated by F. P. Smith in England and by Capt. John Ericsson, first in England and later in the United States. Ericsson is generally given the credit of having made the first successful application of the screw-propeller to steam-navigation. At present it is the only method of propulsion used on large steam-vessels. The design of the shape and size of the propeller depends on conditions more or less peculiar to each vessel, and requires not only calculations but often experiments before the best shape is found for a given boat. Propellers are generally made of gun-metal. The dimensions of the propellers and shafts on the transatlantic steamers are very large. For the Celtic, a White Star steamer of 14,259 tons displacement, the two propellers each have a diameter of 20 feet and are carried on steel shafts of 19½ inches diameter. Consult the U. S. Navy Dept.'s professional papers.