. Cyclopedia of architecture, carpentry, and building : a general reference work .... in Fig. 37 as center, describe the arc 8, which isintersected by an arc struck from 3 as center and with 3-8 in Fig. 8 .x^ t Fig. 35. 35 as radius. Now use alternately as radii, first the divisions inB 8 C in Fig. 33, then the length of the slant lines in Fig. 35,the divisions in E 3 A in Fig. 33, and again the distances inFig. 35, until the line B A in Fig. 37 has been obtained, which isobtained from B A in Fig. 33. Trace a line through points thusobtained in Fig. 37 as shown by A B 8 9 F G A. Trace thishalf
. Cyclopedia of architecture, carpentry, and building : a general reference work .... in Fig. 37 as center, describe the arc 8, which isintersected by an arc struck from 3 as center and with 3-8 in Fig. 8 .x^ t Fig. 35. 35 as radius. Now use alternately as radii, first the divisions inB 8 C in Fig. 33, then the length of the slant lines in Fig. 35,the divisions in E 3 A in Fig. 33, and again the distances inFig. 35, until the line B A in Fig. 37 has been obtained, which isobtained from B A in Fig. 33. Trace a line through points thusobtained in Fig. 37 as shown by A B 8 9 F G A. Trace thishalf pattern opposite the line G F. Then will B A G A^ B^ 8^ 2 p-— E2 10 OH Fig. 3& 9 F 9 8 be the pattern for the front half of the pail. If f^rany reason the pattern is desired in one piece, then trace one-half of D^ D2 E^ E^ in Fig. 32 on either side of the pattern inFig. 37 as shown by the dotted lines 8 D^ E^ 9^ and 9 E D edges for wiring and seaming. Fig 88 shows the method for obtaining the pattern for anEmerson ventilator shown in Fig. 39. 101 42 SHEET-METAL WORK. While the reguUir Emerson ventilator has a flat disc for ahood it is improved by placing a cone and deflector on the topas shown. To make the iDatterns, proceed as shown in Fig. draw the center line a 5, on either side of which lay off 102 SHEET-METAL WORK 43 1| inches, making the pipe A, 3 inches in diameter. The ruleusually employed is to make the diameter of the lower flaTe andupper hood twice the diameter of the pipe. Therefore make thediameter oi s d 6 inches. From s and(7, draw a liiie at an angle of 45° to inter-sect the line of the j)ipe at t and ^/ thiscompletes B. Measure 2 inches abovethe line t i and make u di the samediameter as s d. Draw the bevel of thedeflector so that the apex will be ^ inchabove the line t i and make the apexof the hood the same distance above u mas the lower apex is below it. Then drawlines as shown which complete C and D. Fig. 39. Now with c as a center and
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