[TowerTalk] Mast Wall Thickness

[Jim Lux]

On 2/24/14 9:39 AM, Chris Pinholster wrote:
> I have been researching tower mast material. Both aluminum and
> steel.
>
> If aluminum 60601 tubing with 2"OD and .125 wall fails at 35000 ps,
> what happens when you increase wall thickness?

Not much it might seem, as it happens.  The outer part of the wall 
carries the peak stress and fails first (think about holding a bunch of 
spaghetti in your hand and bending it.. which strands break first?)

This kind of thing goes as the 4th power of the radius.

To the first order, you could estimate it as

1^4 - 0.875^4  =0.414 -> 1/8" wall

1^4 - 0.75^4   =0.684 -> 1/4" wall

about 60% more strength for about twice as much metal.

>
> If you increase the thickness of the mast wall, wouldn't that
> increase make a difference in the bend or failure rating? The charts
> at the metal company I visited seemed to indicate that would be true.
> (I was looking at aluminum 2"OD and 1.5"ID)
>
> Also I ran across a chart that showed that using a 14 ft mast, with 4
> ft inside the tower and 10 ft above was stronger than an 11 ft mast
> with only 1ft inside the tower and 10 ft above.
>
> Any opinion or science from this learned group?
>
>
>
> CHRIS PINHOLSTER k4win at mac.com
>
>
>
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