Simple Designs for Sheet Metal Working 



IX. — Development of patterns for approximate spheres 

 By Arthur F. Payne 



Former Director of Vocational Education, Columbia University 



THE name "Approximate Sphere," 

 given to the problem illustrated, 

 will very likely need explanation to 

 some of the readers of this series. The 

 common names for this problem are 

 "Gored Ball" and "Slab-sided Ball." A 

 sphere is an object that presents a perfect 

 circle from all points of view. The 

 sphere, shown in Fig. 1, presents a 



A "slab sided" ball is an appropriate ornament 

 as a finial on top of a flag pole, steeple or turret 



perfect circle from the front view only, the 

 top view is an "approximate circle," that 

 is, it is almost a circle, being divided into 

 sixteen parts, which are variously called 

 gores, slabs, panels or sections. In this 

 article, these parts will be called "sections," 

 as this is considered the correct name. 



The practical application of the prob- 

 lem would be as a finial on top of a flag 

 pole, steeple or turret, or as an orna- 

 ment on buildings. 



The interesting feature about this prob- 

 lem is that the methods used are the same 

 as those used in the elbows and tee joints, 

 illustrated in pre\'ious numbers. In fact, 

 to develop the pattern for one of the sec- 

 tions, we must first of all recognize the 

 fact that each section is merely part of a 

 cylinder or pipe. This may seem some- 

 what difficult to see at first, but as the 

 directions are followed and the pattern 



is developed, it will become clear. This 

 particular point is illustrated by G and H 

 of Fig. 2. 



There are several different methods of 

 developing the pattern for this problem. 

 For the sake of better understanding and 

 practice, three methods are illustrated. 

 However, as they are worked out, it will 

 be seen that they are all based on the 

 same principle. 



The method of obtain- 

 ing the correct front view 

 of the sphere is shown in 

 Fig. 1. This is not abso- 

 lutely necessary to the 

 development of the pat- 

 tern, but is given because 

 it is often useful in mak- 

 ing a sketch for the cus- 

 tomer. To get the cor- 

 rect front view; first, draw the top 

 view A, which is done by dramng a 

 circle of the size wanted and then dividing 

 the circle into the number of sections de- 

 sired. In this case there are sixteen sec- 

 tions. Second, draw the front view B, 

 This presents the problem of drawing the 

 true picture of the section C. We can 

 very easily get the width at the widest 

 part by dropping down the dotted lines as 

 shown in the drawing, but we have to 

 find some way of drawing in the curved 



A short cut method in which no bottom 

 view is required for obtaining pattern 



line to complete the section from the 

 front view. This is done by drawing the 

 arcs D and E on the top view. This is 

 for the purpose of locating points on the 



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