. Cyclopedia of architecture, carpentry, and building : a general reference work .... Fig. to know how the side of the tapering elbow would look,take a tracing of N O K J, reverse it and place it as shown byJ W M K. For the pattern i^roceed as follows: With L as a center andL H as a radius describe the arc 1 1. Starting from 1 set off on 112 SHEET-METAL WORK 53 this arc twice the stretchout of 1 4 7 in plan, as shown by similarfigures on 1 1, from which draw radial lines to the apex L. Againusing L as center with radii equal to L N, L1, L 2 to L-7, draw arcsas shown intersecting rad
. Cyclopedia of architecture, carpentry, and building : a general reference work .... Fig. to know how the side of the tapering elbow would look,take a tracing of N O K J, reverse it and place it as shown byJ W M K. For the pattern i^roceed as follows: With L as a center andL H as a radius describe the arc 1 1. Starting from 1 set off on 112 SHEET-METAL WORK 53 this arc twice the stretchout of 1 4 7 in plan, as shown by similarfigures on 1 1, from which draw radial lines to the apex L. Againusing L as center with radii equal to L N, L1, L 2 to L-7, draw arcsas shown intersecting radial lines having similar numbers. Throughthese intersections draw the line J L. Then O N J K Lor A will be the pattern for the upper arm (A) in elevation, andP R T X Y or B the pattern for the lower arm (B) in elevation. «l*\\^ N.^^^^^^- III I i**\ ^ ^ \ \ ^ V ^ ;;. ii\\\\ \ ^s ^. Fig. 55. The pattern should be developed full size in practice and thenpricked from the xDaper on to the sheet metal, drawing the twopatterns as far ajjart as to admit allowing an edge to A at a; alsoan edge at h to B for seaming. When a pattern is to contain more than two pieces the methodof constructing the miter lines in the elevation of the cone is 113 54 SHEET-METAL WORK slightly different as shown in Fig. 55. Assume the bottom to be3 inches in diameter and the top 1| inches. Let the vertical heightbe 4 inches. In this problem, as in the preceding, the variouspieces necessary to form the elbow are cut from one cone whosedimensions must be determined from the dimensions of the requiredelbow. The first step is to determine the miter lines, which canbe done the same as if regular i^ieced elbows were being the elbow is to consist of four pieces in 90°, follow the rule given in connection with elbow drafting. The top and bottom 90piece equal 2; the two middle pieces equa
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