Re: [ATM] Help with Strut Flexure in my 3 Truss DOB

[Woodchuck <djv@bedford.net>]

On Fri, 2 Jun 2006, Daniel Fundo wrote:

> <<  As I understand it from the original message, there are only three
> (nearly parallel) tubes supporting the upper cage, instead of three
> PAIRS of poles.  Is this correct?
>
> If it is correct, then the problem is that the current "trusses" are
> not actually trusses, they are simply cantilevered beams.  If they are
> indeed 1.25" in diameter, then it's no wonder they are flexing over
> that length.  >>
>
> As Mel pointed out, with just three poles, the connection points on at
> least one end have to be fixed and rigid.  It would be better if both
> ends had rigid connections.  By rigid, I mean not able to translate in
> any direction about the joint.  The best way to do this is to pass the
> member through two or more holes, as the Highe design does.
>
> *****-----
> Dan F.

Just a random thought, no experience with it: would there be any
rigidity gain if the tubes were pre-stressed somehow, say by a
threaded rod passed down the axis and then that rod tensioned?
This would change the balance of the scope adversely.  It might
require tweeking with a torque wrench from time to annoying time.
But would it increase rigidity significantly?

Dave
-- 
      The law has converted plunder into a right and lawful defense
      into a crime.  -- Frederic Bastiat, 1850

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