[TowerTalk] Mosley PRO 57 B40 HD on Versatower M60

[Jim Lux]

At 02:11 PM 8/1/2006, Tom Osborne wrote:
> > Perhaps you might like to  consider some form of 'positive pull->down'
> > and/or some guying. From memory, I believe that the >Versatower is fitted
> > with guying points.
>
>Hi All
>
>Maybe I'm mistaken, but I thought guying a crankup tower was a no-no.  Too
>much downward forces.  Did I seee that somewhere?  73

You did..

however, if the mfr has designed it for guying, then it would (obviously) 
be ok.  You might also have a tower which is "safety guyed" in that the 
guys aren't there to hold it up (as in a standard guyed tower) but more to 
control where the debris will land if it fails, or to limit some 
catastrophic failure mode.

Here's a parallel example.  In theatrical lighting, there's the clamp that 
holds the instrument to the pipe frame, but there's also a loop of steel 
cable that will keep the thing from crashing down on the stage (or 
audience) if the clamp fails.

Similar schemes are used as seismic restraints on overhead lighting and 
ductwork. The upside down "guy wire" isn't designed to carry the normal 
loads, but to limit the range of motion in an earthquake event.

I could also see guying the bottom segment of a crankup in a specialized 
design where you wanted to limit the bending moment loads transmitted to 
the base. It would turn the bending moment loads into a compression load on 
the tower and a tension load on the guy (making the bottom section 
essentially a huge triangular base).  This isn't something you'd do 
casually...there's a fair amount of analysis required to make sure that the 
telescoping still works, and that you haven't transferred the loads from 
one place to somewhere else.

>Tom W7WHY
>
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