D. H. (Dennis Hart) Mahan

Industrial Drawing; Comprising the Description and Uses of Drawing Instruments, the Construction of Plane Figures, the Projections and Sections of Geo D. H. (Dennis Hart) Mahan

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1883 edition. Excerpt: ... to O--B) from the axis O--P, they, in revolving round it, will describe the circumferences of circles, the radii of which will also be equal to 0--B.. In like manner, if we draw any other line parallel to A--B, or D--C, as a--b, its point b, or a, will describe a circumference having for its radius o--b, which is also equal to O--B. The surface thus described is termed a right circular cylinder, and, from the mode of its generation, the following properties may be noted:--1st, any line drawn on it parallel to the line O--P, which last is termed the axis, is a right line, and is termed a right line element of the cylinder; 2d, any plane passed through the axis will cut out of the surface two right line elements opposite to each other; 3d, as the planes of the circumferences described by the points B, b, &c., are perpendicular to the axis, any plane so passed will cut out of the surface a circumference equal to those already described. Prob. 85. (PI. X. Fig. 108.) Projections of the cylinder. Let us in the first place suppose the cylinder placed on the horizontal plane with its axis vertical. In this position all of its right line elements, being parallel to the axis, will also be vertical and be projected on the horizontal plane in points, at equal distances from the point o, in which the axis is projected. Describing therefore a circle, from the point o, with the radius equal to the distance between the axis and the elements, this circle will be the horizontal projection of the surface of the cylinder. To construct the vertical projection, let us suppose the generating rectangle placed parallel to the vertical plane; in this position, it will be projected into the diameter a--b of the circle on the horizontal plane, and into the...