For a 2" OD tube mast with 1/8" wall thickness, increasing wall thickness
will decrease stress for any given bending load as follows:
1/4" wall: 61% of 1/8" wall stress
3/8" wall: 49% of 1/8" wall stress
1/2" wall: 44% of 1/8" wall stress
2" solid rod: 41% of 1/8" watt stress
Another way to express this is the increase in strength = 1 / the
percentage stress reduction.
Hope this helps.
Matt
KM5VI
-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of Jim
Lux
Sent: Tuesday, February 25, 2014 7:47 AM
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Mast Wall Thickness
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@mac.com
>
>
>
> _______________________________________________
>
>
>
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