[TowerTalk] Mast Analysis

[Dave D'Epagnier]

> -----Original Message-----
> From:	K7LXC@aol.com [SMTP:K7LXC@aol.com]
> Sent:	Wednesday, December 20, 2000 11:06 PM
> To:	DAVED@ctilidar.com; towertalk@contesting.com
> Subject:	Re: [TowerTalk] Mast Analysis
> 
> In a message dated 12/20/00 3:43:45 PM Pacific Standard Time, 
> DAVED@ctilidar.com writes:
> 
> > A while back someone posted a web site where there is an article
> describing
> >  how to calculate mast yield. 
> 
>     Calculate? Isn't that what you look up in the tables or ask your
> material 
> supplier? The yield strength is provided by the manufacturer or dealer. 
> 
>     There is a pretty good chart in Dave Leeson, W6NL's (ex-W6QHS) book on
> 
> "Physical Design of Yagi Antennas". 
> 
> >  I've lost my bookmark for this site. I'm trying
> >  to figure out which would be stiffer: an aluminum mast with 2" diameter
> and
> >  0.375" wall or a 2.5"diameter 0.25" wall mast. Can anyone point me in
> the
> >  right direction?
> 
>     The yield on the material is the same - about 35kpsi. The larger the 
> cylinder (or mast), the more strength it's got. More wall thickness
> doesn't 
> directly equate to a stronger material.
> 
>     Make sure your rotator and antenna mast clamp hardware will work with
> a 
> 2-1/2" diameter - some won't.
> 
> Cheers,   Steve   K7LXC
> Tower Tech
> Champion Radio Products 
> 
[Dave D'Epagnier]  I guess "yield" was the wrong word. I'm looking at
extending my mast so it sticks out of the top of my tower by about 10' or
so. Presently the rotor plate is located about 3' from the top of the tower
and I have a thrust bearing at the top. I want a mast that is fairly stiff
so I can climb up on it if I have to. So I guess a stiffness (modulus?)
calculation is what I'm after.
By the way, is it silly to have that much mast sticking out if only 3' of it
is in the tower? Would a 20' mast be a lot better with 10' of it in the
tower and 10' sticking out the top?

thanks,
Dave



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