[TowerTalk] Plumbing a tower

[Jim Lux]

David Gilbert wrote:
> 
> Hi, Pete.
> 
> I'm kind of sorry I even wrote my post now for the confusion it has 
> apparently created, but just to clarify ... I was putting up a 70 foot 
> AN Wireless self-supporting tower (model HD-70).  It's basically a 
> heavier version of the popular Trylon towers, and both have the same 
> issue.  You encase the base in concrete before you ever add the rest of 
> the tower, and the eventual "plumbness" of the finished tower is a 
> function almost solely of how accurately you plumb the relatively short 
> base (five feet in my case) before the concrete is poured.  My tower 
> tapers from 48 inches on a face at the base to about 22 inches at the 
> top, which calculates out to a leg angle right at 89.0 degrees.  Every 
> 0.1 degree of error therefore gives about two inches of offset at the 
> top, and obviously anything beyond a full degree of error (pretty easy 
> to get with many alternate methods) would put, in my case, a 2,000 pound 
> tower partially leaning out over one of the legs ... with no guy wires 
> to help support it.


Out of curiosity, does the spec sheet or engineering drawings say how 
much deflection of the top one would expect at rated wind load?  It 
might actually be more than a few inches.  I've been at the top of some 
unguyed poles in the 50-100 ft range, and it's seemed to me that they 
swayed a fair amount.