[PSUBS-MAILIST] sphere construction,

[Sean T. Stevenson via Personal_Submersibles]

I'm pretty sure that head forming would be cheaper. 

Sean



On July 12, 2017 8:37:10 PM MDT, "Sean T. Stevenson via Personal_Submersibles" <personal_submersibles at psubs.org> wrote:
>Hank, the physics of this doesn't work. Within the shell wall, you have
>tensile or compressive (hoop) stresses, shear stresses, and bending
>stresses.  Anytime you stress a material in tension or compression, you
>also induce stresses in the transverse direction. With thin-walled
>shells, you can make an effective approximation about the stress
>distribution being evenly distributed across the shell cross section.
>With thicker shells, this doesn't hold true. Bending and shear stresses
>are introduced even in a nominal geometry shell. With a sphere cut into
>slices, only compressive load which is perpendicular to the seams will
>carry across the gaps unaffected. At any angle of incidence, shear
>force is introduced which will not be carried through the interface
>unless sufficiently precompressed, just as when tensioning a bolt
>joint. These shear forces will not be borne by glue.
>
>The solution is to make the interface surfaces coincident with the
>center of the sphere, just as when designing a hatch to replace shell
>material in a hole. Each ring in such a sphere would consequently have
>a different conical angle on each side. The difficulty would be in
>maintaining tight machining tolerances for concentricity and mating
>angle. You would also require some sort of external strapping /
>structure in order to both keep it all together, and bear any external
>loading which is not purely compressive. Also, the glue won't work if
>there is an extrusion path. Plan on metal to metal sealing between each
>ring, with an elastomeric backup at the outside of each seam.
>
>Sean
>
>
>
>On July 12, 2017 6:50:44 PM MDT, hank pronk via Personal_Submersibles
><personal_submersibles at psubs.org> wrote:
>>Hi all,Today I had an idea that would not have been possible before I
>>had a big lathe.  I can buy a series of 4 inch thick rings and machine
>>them flat, glue them together to create a sphere.  The rings can be
>>machined individually so when glued together I have a sphere.  The
>>beauty of this is I can have additional thickness where I need it,
>like
>>the hatch land.  The ring that makes up the hatch land can be
>>thicker.Any reason this is a bad idea.Hank
>>
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