WINDERS IN THE QUARTER-SPACE, WREATH IN ONE PIECE, TO FORM ITS OWN
EASING INTO STRAIGHT RAIL.
Fig. 1 shows plan with face of risers laid, and centre line of rail
enclosed with tangents A B C.
Fig. 2 shows the development. Make Y Y equal stretch-out of centre of
rail, Fig. 1. Set up treads and risers, placing the risers as they
occur on the centre line of rail, Fig. 1; draw the centre falling line
as shown. To development tangents make 1 2 C equal A B C, Fig. 1.
Continue the tangent C B in a line with straight rail; make H R equal
the distance between the line 1 and springing; join R B extended to cut
the level line in F. Draw the joint line square to the straight rail,
and R P square to the tangent; mark off along R P, R S to equal half
thickness of plank.
Fig. 3 shows the face mould for the top side of the plank. Make R A B F
and B C equal corresponding letters, Fig. 2, and F C equal F C, Fig. 1;
draw C O and A O parallel to A B and B C; draw the major axis O M
square to F C through the centre, with M as centre and M O, Fig. 1, as
radius strike an arc at P; draw V L through the centre and tangent to
the arc. Make M H equal M H, Fig. 1; draw Y J parallel to V L; make Y E
equal H E, Fig. 1. Draw Y J parallel to M P, and J K square to major
axis; join K E for section line; draw the short tangent from E square
to K E.
Fig. 4 shows bevels, width of mould, thickness of plank. Get the levels
by taking O, Fig. 3, as centre, and for radius open out to touch each
tangent; transfer these distances to Fig. 4 for each bevel as shown,
and complete the sections as usual; the section at each joint will
be in the centre, but each of the others will be below. Make C E D,
Fig. 2, equal C E D, Fig. 1. Make E E and D D equal P J and P O,
Fig. 3. Then the difference between K D E and C and the falling line,
is what each section will be out of the centre of plank.
Fig. 5 shows the bevels for the bevelled joint at R. Draw P P to the
same bevel as the bevel for the shank, marked O O, Fig. 4; draw C H
square to P P. Make C N equal 1 1, Fig. 4, make C S and C S equal
S S, Fig. 2, and join S E and S P for bevels T and S. Cut the wreath
out square through the plank as usual, except at this joint, which is
worked across the top and bottom to the bevel T, the bevel S being
for the sides. If the joint is worked true to these bevels, it will
joint correctly to the straight rail. S S, Fig. 2, is what the face
mould will require to be longer for the under side; this is shown by
the shaded part on end of shank, Fig. 6, while R S on the shank of the
top face mould, Fig. 3, shows the same amount shorter. It is presumed
that the method of squaring the wreath is fully understood, and needs
no further explaining here, as it can only be a repetition of what was
described in the first few plates.
[Illustration: PLATE 27.]