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>>Would capping the ends of the cylinder with a hollow hemispherical 
>>shape improve the strength compared to a plate of the same material
>>and thickness? If so, is it just not worth doing because of additional 
>>manufacturing complexity?

You forgot about the most important point - how would you ever stand
your light up if it had hemispherical end caps :^) :^) :^)

>I believe the answer to both questions is yes. First a hemispherical 
>end cap does not transfer bending forces (or at least minimizes) into 
>the end of the tubular body, if the wall thickness of the end cap and 
>body are similar. The walls of the end cap where it joins to the 

No matter what the thickness of the end caps are, they would not
transfer bending forces *IF* the diameter of the sphere used for the
end caps matches the diameter of the cylinder. In that case all the
force would be compression force along the longitudinal access of the
cylinder.

>cylinderical body tend to deflect inward just like the walls of the 
>body. Conversely a flat plate does transfer bending forces as the plate 
>deflects inward in the center which tends to rotate the edges of the 
>plate. If the end cap is bonded, or tightly fit, to the body it will 

It ONLY transfers a bending force IF it is rigidly sealed across the
entire surface.  That "bending force" is in reality a compression of
the cylinder along the inner surface with an accompanying "tension"
force along the outside.  It is quite possible to design a "floating"
end cap that does NOT transfer any such force, but merely transmits a
pur compression force (similar to that of the hemispherical end cap).
Again, THIS would be MUCH easier than dealing with a hemispherical end
cap arrangement from a manufacturing perspective.

>transfer this rotation into the body. A hemisphere would be the 
>preferred end closure, but your second question touches on the reality 
>of the issue. Hemispherical end caps involve more manufacturing 
>complexity. Flat end caps are readily producible, and if sufficiently 
>thick will suffice for deep dive light battery cannisters. End cap 
>thickness of the presently available lights such as the AUL does not 
>appear to be the more limiting factor in the light design. Other 
>factors such as out-of-roundness of the body and a bonded lower end cap 
>may dominate.

Partial bulkheads COULD be imbedded in the light IF it were necessary
in some of these lights to attain greater depths.

Very interesting discussion - it's been years since my mechanical
engineereing classes but, the basics are pretty easy to understand and
remember...

This discussion DOES give me some good ideas for projects of my
own though :^)

-Carl-

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