A history of the growth of the steam-engine . n such a manner thattheir position may be changed slightly if desired. Theblades are shaped like the section of a pear, the wider partbeing nearest the hub, and the blades tapering rapidlytoward their extremities. A usual form is intermediatebetween the last, and is like that shown in Fig. 141, thehub being sufficiently enlarged to permit the blades to beattached as in the Griffith screw, but more nearly cylindri-cal, and the blades having nearly uniform width from endto end. MARINK ENGINES. 401 The pitch of a screw is the distance which would betr
A history of the growth of the steam-engine . n such a manner thattheir position may be changed slightly if desired. Theblades are shaped like the section of a pear, the wider partbeing nearest the hub, and the blades tapering rapidlytoward their extremities. A usual form is intermediatebetween the last, and is like that shown in Fig. 141, thehub being sufficiently enlarged to permit the blades to beattached as in the Griffith screw, but more nearly cylindri-cal, and the blades having nearly uniform width from endto end. MARINK ENGINES. 401 The pitch of a screw is the distance which would betraversed by the screw in one revolution were it to movethrough the water without slip ; i. e., it is double the dis-tance CD, Fig. 140. CD represents the helical path ofthe extremity of the blade B, and O EFH K is that ofthe blade A. The proportion of diameter to the pitch ofthe screw is determined by the speed of the vessel. Forlow speed the pitch may be as small as \\ the vessels of high speed the pitch is frequently double the.
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Keywords: ., bookcentury1800, bookdecade1870, bookidc, booksubjectsteamengines
