WRONG !!! (see below)
The maximum shear stress Tau (max) for a hollow tube is
Tau (max) = 16 Mt x D / pi (D^4 - d^4) ... (4th power of D and d)
where D is the Outside Diameter
d is the Inside diameter
Mt is the bending moment (I presume)
It is clear that the greater the wall thickness, the greater the
strength,
which is maximum when d = 0 (solid rod).
NOTE: MOST of the strength comes from the outer region of the tube
and it is more 'effective' from a strength vs weight standpoint to go to
a larger diameter thin wall tube than to increase the wall thickness.
When d = 0.5 D,
Tau = (1 - 0.0625 ) Tau (rod) = 93.75% of the strength of a solid rod.
When d = 0.75 D,
Tau = (1 - 0.3164) Tau (rod) = 68.36% of the strength of a solid rod.
Tom N4KG
On Thu, 28 Feb 2002 "Randy Williamson" <ac7nj@yahoo.com> writes:
> Solid is not stronger than hollow as it was explained to me its about
> surface area. What would be interesting is carbon fiber and epoxy
> resin over a round mold.
>
> Randy
> AC7NJ
>
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