Popular Science Monthly 



937 



methods. Fourth, divide the circle into 

 sixteen equal parts. Project lines from 

 these points direct to the base line, then 

 direct to the apex; these are the radial 

 lines. Fifth, from where these radial 

 lines cross the joint line of the cone and 

 cylinder, project lines straight across to 



3 ng.5 



Developing a pattern for an egg tester 

 which is a truncated cone and round pipe 



the line apex-1 to get the true lengths. 

 Do the same with the V-shaped opening 

 at the bottom. Sixth, draw the top and 

 bottom pattern arcs, N-M and 1-9, getting 

 the correct length by transferring the 

 spaces from the bottom view circle. 

 Seventh, from the numbered spaces on the 

 pattern arc, draw lines to the apex. 

 Eighth, take the true length points on line 

 apex-1 and swing them over the pattern 

 until they cross the same numbered line 

 coming up from the pattern arc, making 

 crosses. Connect these crosses with a free- 

 hand curve. Ninth, to get the pattern for 

 the V-shaped opening, get the true 

 height by projecting straight across to 

 the line apex-1, then swing the line over 

 to radial pattern line, 5. To get the true 

 width we must make use of "auxiliary 

 points," as we have done once or twice 

 before. On the front view project lines 

 straight to the bottom view circle (points 

 marked X). With your dividers take the 

 distance on the circle from point 4-X and 

 lay ofif on the pattern arc as shown in the 

 drawing. Do the same for the other 

 distance, 6-X, connect the three points 

 and the one-half pattern will be complete. 



The illustration (Fig. 4) shows the de- 

 velopmentof patternsfor a "Dust collector 

 Intake." The technical description of 

 this problem is "Rectangular four-sided 

 Prism Intersecting a Truncated Cone off 

 Center." 



The steps in the development of the 

 pattern are as follows: First, draw 

 front view. A; the joint line cannot be 

 drawn until the points are projected 

 across from the side view, B. In this 

 problem the joint line is absolutely 

 necessary and is obtained by drawing the 

 bottom circle on both front A and side B 

 views (as only one-quarter pattern is 

 needed, only one-quarter circle is drawn). 

 Second, space and number each bottom 

 view quarter circle as in the preceding 

 problems. Be very careful to number 

 these correctly. Notice that 1 is at the 

 right on front view A, but in the side 

 view B it is in the exact center. Third, 

 from these numbered points draw lines 

 straight up to the base line, then straight 

 to the apex. Fourth, on side view B 

 where the lines to the apex cross the end 

 view of the rectangular pipe make marks 

 as in the drawing and draw lines across to 

 the front view, A. Where they intersect 

 the same numbered lines coming up from 

 the bottom make a cross. It will be 

 noticed that if we use only the regular 

 numbered lines coming up from the bot- 



A dust intake collector or rectangular four- 

 sided prism intersecting a truncated cone 



tom view quarter circle we shall not have 

 enough points to definitely locate the 

 joint line on front view A, so we must 

 again make use of the "auxiliary lines." 



