Fig. 108. Application of Bevels in Fitting Wreath to Rail.
In [Fig. 102] is presented an example of a few steps at the bottom of a stairway in which the tangents of the plan form an obtuse angle with each other. The curve of the central line of the rail in this case will be less than a quadrant, and, as shown, is struck from the center o, the curve covering the three first steps from the newel to the springing.
In [Fig. 103] is shown how to develop the tangents of the face-mould. Reproduce the tangents and curve of the plan in full size. Fix point 3 at a height equal to 3 risers from the floor line; at this point place the pitch-board of the flight to determine the pitch over the curve as shown from 3 through b″ to the floor line. From the newel, draw a line to w, square to the floor line; and from w, square to the pitch-line b″, draw the line w m; connect m to n. This last line is the development of the bottom plan tangent a; and the line b″ is the development of the plan tangent b; and the angle between the two lines a″ and b″ will give each line its true direction as required on the face-mould for squaring the joints of the wreath, as shown at m to connect square with the newel, and at 3 to connect square to the rail of the connecting flight.
Fig. 109. Face-Mould and Bevel for Wreath, Bottom Tangent Level,
Top One Inclined.
The wreath in this example follows the nosing line of the steps without being ramped as it was in the examples shown in [Figs. 100] and [101]. In those figures the bottom tangent a was level, while in [Fig. 103] it inclines equal to the pitch of the upper tangent b″ and of the flight adjoining. In other words, the method shown in [Fig. 101] is applied to a construction in which the wreath is ramped; while in [Fig. 103] the method is applicable to a wreath following the nosing line all along the curve to the newel.
The stair-builder is supposed to know how to construct a wreath under both conditions, as the conditions are usually determined by the Architect.