GB149887A - An improved propeller for air and water craft - Google Patents

Abstract

149,887. Urithzen, O. Feb. 12, 1920. Screw propellers. -To design the blade of a screw propeller, two concentric semicircles b, d are drawn with radii equal to the hub and propeller radii respectively, and the elevations of the half cylinders thus shown in plan are also drawn, the height being equal to the pitch of the blades. The semicircles b, d are divided into sectors corresponding to the number of blades, which, in the case shown, is six. Helices a, c with the same pitch are drawn in elevation and the points i, k are projected on to the helix a. The portion of the helix thus cut off then represents the shape of the root of the blade. The length of the arc g, h is marked off along the helix c from e to f, the points e, f are joined by a straight line and a similar curve e, o, f drawn symmetrically on the opposite side, the point o bisecting the curve. In Fig. 2, the dotted rectangle is a plan of the hub, and the line A is the plan of the root of the blade. The line F, M, E is similar to the line f, o, e, Fig. 1, and represents a plan of the tip of the blade. The sides are shown by the lines E, E', F, F<1>. Other contour lines intermediate between the hub and tip may be similarly drawn.