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[Towertalk] mast disaster avoidance

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Subject: [Towertalk] mast disaster avoidance
From: (jljarvis)
Date: Thu, 11 Jul 2002 10:07:52 -0400

This thread still seems to persist.  Some comments are 
and a question are in order:

N4KG recommended either placing the mast inside the
tower while at the 20-30' level, or using a crane.
He further suggested a longer than normal ginpole.
Placing a 100lb 20+ ft mast inside a 130' tower was
"The SCARIEST thing" he'd ever done.   I was only at
60', but I'd never do it again.  

K7NI points out that the Rohn 25/45 ginpole rating is for a 70lb
section of 45G, so you're pushing it with a much heavier mast.  

The root problem is balance and leverage, and lifting height, and it's
flat-out dangerous to pursue this with the top section in place.  

If renting a crane isn't in your budget, REMOVE THE TOP SECTION OF
THE TOWER.      

This gives you a full interior of the tower as a target
for dropping the mast inside, and allows maximum extension of the
ginpole above the tower.  If, as KG suggests, you can do this while
the tower is short, even better.

With the tower top off, you can safely lift a mast 2x the ginpole
working length (max), and lower it in-column with the ginpole, 
inside the near leg of the tower.  This is safe, providing that the 
mast doesn't weigh more than the ginpole tube can stand. 

Attempting it with the top in place--regardless whether it's a tube
top or a flat top--will result in you trying to line up a marginally
balanced or top-heavy mast into a hole (tube or tb-3 clearance) which

This is a recipe for injury, not to mention being hard to do.  

Solutions using added pulleys still leave the same load on the ginpole
material itself, and don't affect balance and geometry.  
The lifting is easier; safety is still compromised.  

Does anyone KNOW the specs on a rohn 2545 ginpole?  How much safety 
margin is there in the tube material?  An ME with handbook available
could avoid needless speculation.  

Jim Jarvis, N2EA
Essex Vermont

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