Fig. 121. Tangents, Bevels, Mould-Curves, etc., from Bottom Wreath
of [Fig. 95], In which Upper Tangent Inclines Less than Lower One.
Seventh Case. In this case, illustrated in [Fig. 117], the upper tangent b″ is shown to incline, and the bottom tangent a″ to be level, over an acute-angle plan. The plan here is the same as that in [Fig. 100], where a curve is shown to stretch out from the line of the straight stringer at the bottom of a flight to a newel, and is large enough to contain five treads, which are gracefully rounded to cut the curve of the central line of rail in 1, 2, 3, 4. This curve also may be used to connect a landing rail to a flight, either at top or bottom, when the plan is acute-angled, as will be shown further on.
Fig. 122. Developed Section of Plane Inclining Unequally
in Two Directions.
Fig. 123. Arranging Risers around Well-Hole on Level Landing Stair,
with Radius of Central Line of Rail One-Half Width of Tread.
To find the bevels—for there will be two bevels necessary for this wreath, owing to one tangent b″ being inclined and the other tangent a″ being level—make a c, [Fig. 118], equal to a c in [Fig. 117], which is a line drawn square to the ground line from the newel and shown in all preceding figures to have been used for the base of a triangle containing the bevel. Make a w in [Fig. 118] equal to w o in [Fig. 117], which is a line drawn square to the inclined tangent b″ from w; connect w and c in [Fig. 118]. The bevel shown at w will be the one to be applied to the joint 5 on tangent b″, [Fig. 117]. Again, make a m in [Fig. 118] equal to the distance shown in [Fig. 117] between the line representing the level tangent and the line m′ 5, which is the height that tangent b″ is shown to rise; connect m to c in [Fig. 118]; the bevel shown at m is to be applied to the end that intersects with the newel as shown at m in [Fig. 117].