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

[Mike Lockwood <melockwo@uiuc.edu>]

Hi,

Daniel Fundo wrote:
> <<  ...The current trusses are 1.25 OD with a wall thickness (I THINK)
> of .058. They are aluminum tubes and are a 56.75 inches long...  >> 
> 
> Patrick,  I don't think the tubes are your problem.  These should be
> more than stiff enough for the weight involved.  The problem has to be
> elsewhere.
> 
> Can you post a few pictures somewhere, including some close-ups?

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.

The solution is to use stiffer poles, which implies using larger 
diameter aluminum poles or a stiffer (and probably heavier) metal.

The alternative is to build an actual truss, which involves forming 
triangles with the poles.  No triangles, no truss.

	Mike Lockwood


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