shown that the large-scale hull presents approximately as perfect a sphere as 

 the models, any data generated by testing of small-scale models should be 

 considered as applicable to the prediction of large-scale capsule performance. 

 Also, it can be hypothesized that scaling up acrylic plastic spherical capsule 

 models results in large spheres with approximately the same relative dimen- 

 sional deviations, providing the same fabrication method is used for model 

 and large-scale capsules. 



Before the discussion of relative dimensional tolerances is concluded, 

 a point brought up in the discussion of the dimensional relationship between 

 model and large-scale capsules should be reemphasized: Since in the fabrica- 

 tion of models it was found that the actual thickness of the hull consistently 

 was less than specified, it was decided to order oversize material for the 

 large-scale capsule so that even with the large tolerances on thickness of 

 stock materials the hull thickness would not be below specified dimensions. 

 Thus, 2.500-inch stock material was used in large-scale capsule, although 

 2.250-inch nominal thickness is actually required on the basis of geometrical 

 scaling. Because of this, even though the hull thickness varied from 2.290 

 to 2.585 inches, it was always above the nominal thickness. This supports 

 the author's assurance that all the experimental data recorded on models is 

 not only applicable, but even probably conservative since the models were 

 actually 10 to 20% thinner than their nominal thickness arrived at by scaling 

 down the actual large-scale capsule thickness. 



Polar Inserts 



The steel structural components required for the assembly of top and 

 bottom polar inserts for the model scale capsules were fabricated by turning 

 316 stainless steel bar stock in a lathe. Particular emphasis was placed on 

 adherence to the tight angular and dimensional tolerances on the beveled 

 bearing and sealing surfaces on the hatch ring, hatch and bottom plate. 

 Since turning these components for the capsule was a typical metal machining 

 operation, no research or development was necessary during their fabrication. 



No problems were encountered in the fabrication of metallic inserts 

 for the 66-inch capsule. The only basic difference between fabrication of the 

 inserts for models and of the 66-inch capsule was the use of type 31 6L stain- 

 less steel and the welding of lifting lugs and bosses on the top hatch assembly 

 instead of milling them out of a solid forging. To make the fabrication 

 economical, the hatch ring, hatch plate, and bottom plate were ordered from 

 suppliers as slightly oversized forgings for machining. 



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