Ellsworth M. Longfield

“ The diagram of triangles and sections, Fig. 319, is now constructed by taking the base lines from Fig. 317. The triangles have a common altitude equal to lines 6–A of Fig. 315. One of the perpendiculars in each section also has this altitude, but the altitudes of points O, N, M, K, and H are made to correspond to the altitudes of similar points in the true section, Fig. 316. The pattern, Fig. 321, is started by placing upon any vertical line a distance equal to the true length line 6–A. The development proceeds in the usual manner until completed. ”

“ These lengths are now placed on the proper miter fines in Fig. 306, and the outline of the back of the elbow is completed, by connecting points B, C, D, and E with straight lines.
Each miter line as it passes through the elevation is divided into two equal parts, thus locating center points P, R, S, and T. The center fine of the elevation may then be drawn by connecting these points.
The oval end of the elbow has two flat surfaces while the round end has none. Consequently, these flat surfaces must gradually diminish in width until they disappear upon reaching the round end of the elbow. ”

“ In order to develop the patterns it is necessary to know the exact widths of these flat surfaces at each cutting plane, and in order to gain this information stretchouts must be made as shown by Figs. ”