[TowerTalk] Response to R for math

[K7LXC@aol.com]

In a message dated 98-10-11 16:25:09 EDT, d.dimitry@mci2000.com writes:

> You wrote:
>  
>  >     Please enlighten me how a 118K psi yield strength chromoly mast will
>  fail
>  >before a 35K psi 6061-T6 aluminum mast? When did they change the laws of
>  >physics? Wall thickness has little to do with it.
>  >
>  My reply:   Wall thickness has as much to do with the strength of a mast as
>  does the material's yield strength.  Both are important factors.  I will
>  give you the formula for it, but first a sort of analogy.  Could you drive
>  your car at 35 mph through an 1/2" thick aluminum plate spanned across the
>  road and firmly secured to anchored poles on both sides?  Kind of chancy,
>  isn't?  I definately would not want to try.  What if we changed the
>  thickness to that of common kitchen type aluminum foil?  Would you take a
>  shot at it?  Why not, your car would probably sail right through it with
>  little or no damage.

     First of all, we're talking about suitable antenna masts - not aluminum
foil. Secondly, my point was that material yield strength is more important
than wall thickness (which in amateur construction project discussions is
commonly understood to be 1/8", 1/4", etc.). My apologies - I didn't mean to
imply that wall thickness was not important. 

>  (BTW, alum. weighs about 38% of steel and stainless of the same Volume of
>  material, for those concerned about weight.)

     Weight, smeight. We're concerned about proper engineering and
reliability. 
>  >
>  >      What specifically are you talking about? Feel free to post the
alloy,
>  >certification and other specifications of the aforementioned masts along
>  with
>  >the price. Broad allusions to the "best value in masts" doesn't give us
any
>  >information.

      Still waiting for this information. 

Cheers,  Steve  K7LXC

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