Engineering Wonders of the World
Volume I

THE PROPELLING MACHINERY OF A SHIP. 43 chief difficulties to be overcome before the use of this prime mover will become general, however, is the production of large cylin- ders which will stand the high impulses and great and rapid variations of temperature that occur with internal combustion. A large number of pleasure yachts and small vessels for conveying merchandise have been fitted with this propulsive agency, while its use as an auxiliary to sail power in large sailing vessels has been strongly advocated. Turning to warships, most of the submarines now in existence are fitted with internal-combustion engines, as are also a number of vedette boats ; while much useful data has recently been derived from the series of experiments with H.M. gunboat Rattler, propelled by a 500 horse- power gas engine. The first vedette boat constructed in Eng- land to demonstrate the great possibilities of the internal- combustion engine for driving small craft of this description was the motor torpedo launch Dragonfly, built Motor Tor- pedo Launch “ Dragonfly.” by the celebrated Thorny croft firm. She is 40 feet long, with a beam of 6 feet 2 inches, and has a draught of water of only 2 feet 7 inches, the displacement being 4| tons. The four-cylinder motor develops about 120 b.h.p. at 900 revolutions, and the designed speed was 18 knots. The boat, as will be seen from Fig. 18, carries a 14-inch Whitehead torpedo in dropping gear. Other similar vessels with the same prime mover, but of larger dimensions and greater speed, have followed the Dragonfly, and there can be little doubt that the next few years will witness a widely-extended use of internal-combustion machinery for the “ mosquito ” craft of the world’s fighting fleets. Mr. James M;Kechnie (of Messrs. Vickers, Sons, and Maxim) lias already made a proposal to equip a battleship with this type of propelling machinery ; but it may safely be prophesied that the steam turbine, combined with oil fuel for the furnaces, will not be displaced in the larger class of war and merchant vessels for some years to come. Fig. 18.—THORNYCROFT MOTOR-DRIVEN TORPEDO LAUNCH “ DRAGONFLY.”