. Transactions. d 10,440 lb. Four single blades cast from the samepattern, after the blade seats were machined, weighed 3675, 3675, 3675,and 3670 lb. Fig. 8 shows an 18 ft. 6 in, four-blade, 18-ft. pitch, built-up wheelbeing installed on the steamer Mystic. The weights of the four bladeson this wheel were 3475, 3475, 3475, and 3470 lb. In operation the slipwas reduced from 16 to 9 per cent, and the time saved in the round tripvoyage was approximately 10 per cent. 542 THACHER MOLDING PROCESS FOR PROPELLER WHEELS AND BLADES The steamer Patrick Henry, a standard U. S. Shipping Boardvessel, of 12,
. Transactions. d 10,440 lb. Four single blades cast from the samepattern, after the blade seats were machined, weighed 3675, 3675, 3675,and 3670 lb. Fig. 8 shows an 18 ft. 6 in, four-blade, 18-ft. pitch, built-up wheelbeing installed on the steamer Mystic. The weights of the four bladeson this wheel were 3475, 3475, 3475, and 3470 lb. In operation the slipwas reduced from 16 to 9 per cent, and the time saved in the round tripvoyage was approximately 10 per cent. 542 THACHER MOLDING PROCESS FOR PROPELLER WHEELS AND BLADES The steamer Patrick Henry, a standard U. S. Shipping Boardvessel, of 12,500 deadweight tons, which was equipped with a Thacherprocess propeller, made on a light load trial trip a speed of 12 knots, whichmeans a substantial gain over identical type ships having other makes ofpropellers. The weights of the four blades were 4345, 4345, 4348, and4350 lb. In Fig. 9 is shown a three-blade built-up manganese-bronze propellermade by the Thacher process. This wheel when tested on a balancing. Fig. 8.—Four-blade, 18-ft. pitch, bthlt-up wheel of steamer Mystic. stand developed no variation in balance. It is one wheel of a twin-screwinstallation on the steamer Herman Frasche. Metal Used in Propellers In propellers used in the Navy, manganese bronze, having an ultimatestrength of 70,000 to 80,000 lb. per sq. in. and an elongation of 20 to 35per cent, is specified. For commercial use many wheels have been made of semi steel. In thecase of thirty such wheels, the lowest ultimate strength was 32,555 lb. ENRIQUE TOUCEDA 543 per sq. in., the highest 42,175 lb. per sq. in.; while the average was 36,658lb. The breaking of propeller blades has not been uncommon; in mostcases this has been attributed to lack of perfect balance. It is notunusual for an 18-ft. wheel to have a tip speed of over 5500 ft. per the use of this method, the following features can be guaranteed:The diameter will be a true circle; blade angle wall be accurately estab-
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Keywords: ., bo, bookcentury1800, bookdecade1870, booksubjectmineralindustries
