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Re: [ATM] 6-pole
This is precisely the point I try to make. You should really calculate how
well the definition of your structure is (call it rigidity) as a function of
the components and design. Tom Krajci had a link to a mechanical calculator
program for truss structures:
http://www.grapesoftware.mb.ca/
What you see very often is overdimensioning of the trusses, in diameter and
hence weight. Just take it a bit further and you can do with a single pole
(I think it is technically not right to call this a truss) like Russ
Porters' garden scope. Of course, your suggestion to use a hollow pole and
put the optical axis in the center has been used on several occasions.
The original statement I responed to, was that 8 trusses would overspecify
the position. This is only true when the mounting points leave rotational
freedom and, like a real truss should do, only define distance between
mounting points.
AtM
> But the idea of a truss is that the members should not have significant
> change in lenght during load (even if they are not very resistant to
> bending) - a much less demanding requirement than stiffness against
> bending or rotation as required with less than 6 members. Thus, the
> primary requirement is sufficient cross-sectional area for the material
> and loads. But whether a 6-member truss or a 8-member one with 3/4 as
> large cross section and weight would be stiffer, I don't know. It should
> be calculable - there might even be ready-made solutions to be found.
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