Article with Round Top and Semicircular=ended
This is an article (Fig. 148) which belongs to the family of the oblique cone, for its rounded surface at the ends is formed of two half-frustums and its flat sides of two triangles.
Its pattern is shown struck out in Fig. 149. A quarter-plan and a half-elevation are marked out as seen, and the point B obtained by joining 3 to c, and producing to meet the base line. The points 1, 2, and 3 are swung around and joined up to T. The line T 0 on the pattern is made the same length as T 0 on the elevation. Arcs of circles are then drawn with radii T l', T 2', and T 3', the points 1, 2, and 3, and the corresponding points for the inner curve up to C being obtained as in Fig. 143. Now take C on the pattern as centre and C 3 as radius, and mark the arc as shown, cutting off a point upon it by making line 3 3 equal in length to twice the line 3 4 from the plan. Thus we now have the two flat triangles added on to the first portion of the pattern. The two centres for the remaining lines can, of course, easily be fixed when it is remembered that their lengths are exactly the same as the lines used in marking out the first part of the pattern.
Without the object is very small the body of the article will be made up in two pieces, the seams being at the ends and coming along the lines through 0 on the pattern. The sheet and metal plate worker, however, should find no difficulty in making up an article in any number of pieces if he can strike out the pattern for the complete body.
Article with Circular Top and Oblong Bottom with