[TowerTalk] 7075-T6 Aluminum

[Hank Lonberg]

Okie Doke Pete:

Lets get to know the alloys and treatment.

6000: (6061)

A silicon and mangnesium alloy of aluminum. Heat treatable very
versatile with good formabliliy and corrosion resistance, medium
strength. Very common alloy. Tensile yield strength 6061-T6: 40,000 psi.
E=10,000,000 psi.

7000:  (7075)

A zinc alloy of aluminum. Heat treatable, high strength. Used in
air-frame structures and highly stressed parts. Tensile yield strength
7075-T6: 67,000 psi. E=10,000,000 psi.

Temper T6:

Solution heat treated and artifically aged. Not cold worked after
solution heat treatment to improve strength.

Now wasn't that informative.

7075 is not normally stocked and is typically a special order item. 6061
is very common in multitude of shapes and sections.

Aluminum's modulus of elasticty, E , is 10,000,000 psi. A36 mild steel's
, and other steels for that matter, modulus of elasticity, E, is
29,000,000 psi.

The deflection of a mast due to the antenna loading is a function of
the  antenna load times the distance from the support divided by the
moment of inertia,I , divided by the modulus of elasticity, E. As all
can see that since steel's E is 3X that of aluminum it will defect 1/3
as much for an equal load and section I. There ya go....

If you are concerned about your mast and mast strength use a steel alloy
mast. If you want to use aluminum go ahead, but know that it will
deflect more than a steel mast of the same size for the same load...

Ciao and 73

Hank Lonberg P.E. / KR7X




Pete Smith wrote:
> 
> At 11:19 AM 6/21/01 +0100, David Robbins wrote:
> >in aluminum alloy designations the first number is the alloy composition
> number
> >which can be looked up in a table to get the various percentages of
> elements in
> >the alloy.  the 'T' number is the heat treatment designation.  that can be
> >looked up to tell you what type of heat treatment the material has had.  the
> >heat treatment affects how the grains in the material are arranged, this can
> >affect strength and hardness of the final material.  working after heat
> >treatment as in drawing tubing or bending carribeaners or machining can
> further
> >affect the characteristics of the final product.
> >
> >Greg Gobleman wrote:
> >>
> >> I don't know about using 7075-T6 as a mast but you did ask about
> >> other uses.  Something very similar, 7075-T9 is used as a popular
> >> and tough arrow shaft.  What I don't know is, what the T6 or T9
> >> designation means.  In manufacturing arrows they start with a
> >> larger size tube and draw it down over many steps.
> >>
> But aren't all aluminum alloys significantly less stiff than steel?  I
> thought this and cost, more than ultimate yield strength, were what tended
> to limit the usefulness of long aluminum masts.  Maybe this will smoke one
> of the experts out of the undergrowth...
> 
> 73, Pete N4ZR
> No, no ... that's WEST Virginia
> 
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