Re: ATM 2 Piece Poles - and how trusses really work

[Emery Greg <greg.emery@mohawkcollege.ca>]

Hello All:

Maybe I missed the point about the bolts.  I am assuming that the bolts are perpendicular to the tubes, if they are to connect the two.  If so, are the bolts not in double shear?  It has been a long time since Mechanics 1 and Strength of Materials - I never thought I would use that stuff again :)


ttfn
greg
----- Original Message -----
From: Ross Sackett <rsackett00@yahoo.com>
Date: Tuesday, August 19, 2003 9:28 am
Subject: Re: ATM 2 Piece Poles - and how trusses really work

> 
> A bit more off the top of my head, again.  
> 
> Up to loads where buckling is an issue the squashing
> or extension of truss members in tension and
> compression is controlled by the cross-sectional area
> multiplied by the modulus of elasticity.  Since the
> steel in the connector bolt has 3 times the elastic
> modulus that the aluminum in the tube has, the bolt
> need have only 1/3 the cross-sectional area to match
> the stiffness of the tube in tension.  A 1 inch
> diameter/0.049 wall thinkness aluminum tube has an
> area of about 0.15 square inches.  One third of this
> is 0.05 square inches, which is close to the
> cross-sectional area of a 1/4 inch bolt (ignoring the
> threads).  Thus, a 1/4 inch steel connector bolt is
> the minimum for a 1 inch diameter aluminum tube.  Of
> course, the connections between the bolt and the tubes
> will have to be similarly stiff...
> 
> Have I gone wrong somewhere along the way here?
> 
> Ross
> 
> > 
> 
> 
> 
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