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.
[Illustration: PLATE 18.]