Fig. 133. Finding Bevel for
Wreath of Plan, Fig. 132.
To draw the curves of the mould according to this method, which is a scientific one, may seem a complicated problem; but once it is understood, it becomes very simple. A simpler way to draw them, however, is shown in [Fig. 120].
The width on the minor and at each end will have to be determined by the method just explained in connection with [Fig. 119]. In [Fig. 120], the points b at the ends, and the points in which the circumference of the circle cuts the minor axis, will be points contained in the curves, as already explained. Now take a flexible lath; bend it to touch b, z, and b for the inside curve, and b, w, and b for the outside curve. This method is handy where the curve is comparatively flat, as in the example here shown; but where the mould has a sharp curvature, as in case of the one shown in [Fig. 101], the method shown in [Fig. 119] must be adhered to.
Fig. 134. Well-Hole with Riser in Center. Tangents
of Face-Mould, and Central Line of Rail, Developed.
With a clear knowledge of the above two methods, the student will be able to put curves on any mould.
The mould shown in these two diagrams, [Figs. 119] and [120], is for the upper wreath, extending from h to n in [Fig. 94]. A practical handrailer would draw only what is shown in [Fig. 120]. He would take the lengths of tangents from [Fig. 94], and place them as shown at h m and m n. By comparing [Fig. 120] with the tangents of the upper wreath in [Fig. 94], it will be easy for the student to understand the remaining lines shown in [Fig. 120]. The bevels are shown applied to the mould in [Fig. 105], to give it the twist. In [Fig. 106], is shown how, after the rail is twisted and placed in position over and above the quadrant c d in [Fig. 94], its sides will be plumb.