Fig. 1 shows the plan of rail with the risers landing and starting, placed half a tread from C on each side along the centre line of rail. By this arrangement we get two balusters on the landing the same distance apart as on the steps, and the centre falling line straight.
Draw plan of rail and enclose the centre line with tangents A B C D E. Mark off from C along centre line of rail on each side half a tread, and draw face of risers landing and starting.
Fig. 2 shows the elevation. Make A N equal stretch-out of centre line of rail. Set up two steps and landing, taking care to draw the face of risers as they occur on the centre line of rail, Fig. 1. Draw the falling line resting on the corners as shown. For development of tangents make F D S equal E D C, Fig. 1. From D, square up a line to cut the falling line in R, then E R will be the pitch of the tangent over E D, Fig. 1; join R S for pitch of tangent over D C, Fig. 1. Make E D F, Fig. 1, equal F D C, Fig. 2, join F C, which is the horizontal trace.
Fig. 3 shows the face mould. Make E D S equal E R C, Fig. 2, with D for centre, and R S, Fig. 2, as radius; strike an arc at C with S as a centre, and F C, Fig. 1, as radius; strike an arc to intersect the first one at C, join D C. From C draw parallel to D E, and from E draw parallel to D C; these lines will meet at the centre O. Join S C, which is the horizontal trace. Draw the semi-major axis square to it through the centre and the semi-minor axis parallel. With F as centre, and O N, Fig. 1, as radius, strike an arc at H; draw V L through the centre and tangent to the arc. Say we have one section between the minor axis and C marked 1. Make H N equal O N, Fig. 1. Draw N J parallel to V L. Make J I equal N I, Fig. 1. Draw J P square to V L and P R square to F O; join R I for section line. For bevels, width of moulds, &c., take O for centre and for radius open the compasses to touch each tangent; transfer these distances to Fig. 4, always making the distance between the lines N R, Fig. 4, equal the radius of centre line of rail on plan. Draw the section of rail on each bevel and set off half thickness of plank, and complete the sections as shown. For width of mould make C I P and 1 3 4 and E 6 5 on section lines Fig. 3 equal C I P and 1 3 4 and E 6 5 at sections Fig. 4. It will be noticed that, while at sections C and I the face mould has less stuff on the inside, at section E, on the other side of the minor axis, it has more.
Fig. 5 shows the face mould for the other side of the plank. To cut the wreath out, lay either mould on and transfer the tangents on to the stuff, and mark off on each side of face mould on the minor axis. The stuff should be cut full on this line. Mark off on each side of the tangents at the joint C the distance C P as seen at the section, and on each side of E, E Y as seen at Fig. 4. Draw around roughly from P to the minor axis to Y. The stuff is cut square through the plank to this line inside and out. Plane the stuff true and gauge it to its proper thickness and make the joints square to face of stuff and to the tangents. The application of the face moulds is seen at Fig. 6; the tangents on both face moulds must lie on the tangents marked across both joints of the wreath. Now saw the inside and outside off as shown by the shaded parts at Fig. 6, keeping the saw in the direction of the section lines. Clean up the wreath both inside and out, always keeping the straight edge in the direction of the section lines. Before removing the moulds mark from the top side 22, 33, 44, 55, 66 and 77, as shown by the shaded parts of sections at Fig. 4. Cut the superfluous stuff off the top to these lines, after which, gauge to a thickness, set the gauge full so as to allow the wreaths being cleaned up after the pair are bolted together. Before they are bolted and dowelled together at the centre joint them to the straight rails, and clean off any superfluous stuff there may be on the shanks in a line with the straight rails, and mark the section of rail on the ends of shanks before removing the straight rail; now joint the two together.
But before cleaning the pair off it would be well to test the correctness of the centre joint. Make N Y, Fig. 2, equal S Y, Fig. 1, and join E Y; now if the distance from the centre of the thickness of one wreath to the centre of the thickness of the other on the inside at the sections, at the springing, equals E Y, Fig. 2, the joint will be correct. Having proved the joint in this way, clean them off while together, then take them apart before glueing up. Mark the pattern of rail on the joint and mould them; use a handrail screw to bolt the joints together with and keep them as near as possible the centre of section of rail. There should be two dowels in each joint to keep them from twisting, placed according to pattern of rail.
In taking the length of straight rails, take the length of strings from springing to springing and allow for length of shanks of wreaths, as measured from the joint to springing, in a line with straight rails.
PLATE 18.
