. Scientific American Volume 05 Number 01 (July 1861). ing ex-periment. « m » i Calculating the Speed of Screws. If the pitch of a screw, in feet, be multipliedby the number of turns per minute, and two placesof decimals be pointed off from the right handof the product, the latter will almost expressthe speed in knots per hour, including a screw of 30 feet pitch, making 45 turns perminute, will make (30 X 45 = 1,350) 13-5 knotsnearly per hour including slip. 1,350 in this case isthe number of feet of horizontal motion, includingslip, developed per minute, and as a nautical rule isver
. Scientific American Volume 05 Number 01 (July 1861). ing ex-periment. « m » i Calculating the Speed of Screws. If the pitch of a screw, in feet, be multipliedby the number of turns per minute, and two placesof decimals be pointed off from the right handof the product, the latter will almost expressthe speed in knots per hour, including a screw of 30 feet pitch, making 45 turns perminute, will make (30 X 45 = 1,350) 13-5 knotsnearly per hour including slip. 1,350 in this case isthe number of feet of horizontal motion, includingslip, developed per minute, and as a nautical rule isvery nearly 6,000 feet, and as there are 60 minutes inan hour, the effect of multiplying 1,300 by 60 anddividing the product by 6,000, is, of course, the sameas pointing off two places of decimals at once. By multiplying the pitch of a screw by its revolu-tions per, minute and dividing by 88, we obtain thespeed of the vessel without allowing for slip, which isgenerally about 11 per cent. The above rule is suffi-ciently correct for all common SCIENTIFIC AMERICAN. THE BEST MECHANICAL PAPER IN THE WORLD SEVENTEENTH YEAR. VOLUME V.—NEW SERIES. A new volume of this widely circulated paper commenced on the6th of July. Every number contains sixteen pages of useful informa-tion, and from five to ten original engravings of new inventions anddiscoveries, all of which are prepared expressly for its columns. The SCIENTIFIC AMERICAN is devoted to the interests ot PopularScience, the Mechanic Arts, Manufactures, Inventions, Agriculture,Commerce and the Industrial Pursuits generally, and is valuable andinstructive not only in the Workshop and Manufactory, but also in theHousehold, the Library and ths Reading Eoom. The SCIENTIFIC AMERICAN has the reputation, at home andabroad, of being the best weekly publication devoted to mechanical andindustrial pursuits now published, and the publishers are determinedto keep up the reputation they have earned during the sixteen yearsthey have b
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