[TowerTalk] Mast Wall Thickness

[Chris Pinholster]

I plan on putting a 2element Cubex quad and a Force 12 ef140S rotatable dipole on a 2"OD 1.5 ID, 6061 T6, 10 ft long.

The calculations  of 60% stronger tubing, using the MARC program looks good to me for this wind load.

Sent from my iPad

Chris k4win

> On Feb 25, 2014, at 8:47 AM, Jim Lux <jimlux at earthlink.net> wrote:
> 
>> 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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