This section is from the book "Cyclopedia Of Architecture, Carpentry, And Building", by James C. et al. Also available from Amazon: Cyclopedia Of Architecture, Carpentry And Building.
In Fig. 344 is shown an illustration of a round finial which contains moulds, the principles of which have already been described in the preceding problems. The ball A is made of either horizontal or vertical sections. In Fig. 345 is shown how the moulds in a finial of this kind are averaged. The method of obtaining the true length of each pattern piece will be omitted, as this was thoroughly covered in the preceding problems. First draw the center line A B, on either side of which draw the section of the finial, as shown by C D E. The blanks for the ball a will be obtained as explained in the Instruction Paper on Sheet Metal Work. The mould b is averaged as shown by the line e f, extending same until it intersects the center line at h, e f representing the stretchout of the mould obtained, as explained in the paper on Sheet Metal Work Using h as center, with h f and h e as radii, describe the blank bo.
In the next mould, c c', a seam is located in same as shown by the dotted line Then average C by the line i j, extending same until it meets the center line at k; also average c' by the line l m, extending this also until the center line is intersected at n. Then i j and l m represent respectively the stretchouts of the mould c c', the blank co and cx being struck respectively from the centers k and n. The mould b' b" also has a seam, as shown by the dotted line, the moulds being averaged by the lines p o and s t, which, if extended, intersect the center line at r and u. These points are the centers, respectively, for striking the blanks bo and bx. The flaring pieced is struck from the center x, with radii equal to x w and x v, thus obtaining the blank do.
By referring to the various rules given in previous problems, the true length of the blanks can be obtained.
The principles used for blanks hammered by hand can be applied to almost any form that will arise, as, for example, in the case shown in Fig. 346, in which A and B represent circular leader heads; or in that shown in Fig. 347. in which A and B show two styles of balusters, a and b (in both) representing the square tops and base Another example is that of a round finial, as in Fig. 348, A showing the hood which slips over the apex of the roof. While these forms can be bought, yet in some cases where a special design is brought out by the architect, it is necessary that they be made by hand, especially when but one is required.
The last problem on handwork is shown in Fig. 349 - that of obtaining the blank for the bottom of a circular bay. The curved moulding A will be hammered by hand or by machine, as will be explained later on, while the bottom B is the problem before us. The plan, it will be seen, is the arc of a circle; and, to obtain the various blanks, proceed as shown in Fig. 350, in which A B C is the elevation of the bottom of the bay, I J K being a plan view on A C, showing the curve struck from the center H. In this case the front view of the bottom of the bay is given, and must have the shape indicated by A B C taken on the line I J in plan. It therefore becomes necessary to establish a true section on the center line S K in plan, from which to obtain the radii for the blanks or patterns. To obtain this true section, divide the curve A B into any number of equal parts, as shown from 1 to 6. From the points of division, at right angles to A C, drop lines as shown, intersecting the wall line I J at points 1' to 6'. Then, using H as center, and radii equal to H 6', H 5', H 4', H 3', and H 2', draw arcs crossing the center line D E shown from 1" to 6". At any convenient point opposite the front elevation draw any vertical line,as T U. Extend the lines from the spaces in the profile A B until they intersect the vertical line T U as shown. Now, measuring in every instance&8226; from the point S in plan, take the various distances to the numbered points in plan and place them upon lines of similar numbers, measuring in ever) instance from the line T U in section. Thus take the distance S K in plan, and place it as shown from the line T U to K'; then again, take the distance from S to 2" in plan, and place it as shown from the line T U to 2" on line 2 in section. Proceed in this manner until all the points in the true section have been obtained. Trace a line as shown, when 1" to 6" to Y will be the true section on the line S K in plan.
It should be understood that the usual method for making the bottom of bays round in plan is to divide the profile of the moulding into such parts as can be best raised or stretched. Assuming that this has been done, take the distance from 1" in plan to the center point H, and place it as shown from 1" to L in section. From the point L, draw a vertical line L M, as shown. For the pattern for the mould 1" 2", average a line through the extreme points, as shown, and extend the sane until it meets L M at N. Then, with N as center, and with radii equal to N 2" and N 1", describe the blank shown. The length of this blank is obtained by measuring on the arc 1' \" in plan, and placing this stretchout on the arc 1" of the blank. The other blanks are obtained in precisely the same manner. Thus P is the center for the blank 2" 3"; R, for the blank 3" 4"; O for the blank 4" 5"; and M, for the blank 5" 6".
The moulds 1" 2", 2" 3", and 3" 4" will be raised; while the blanks 4" 5" and 5" 6" will be stretched.