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To: <>
From: "Larry Schimelpfenig" <>
Date: Fri, 21 Sep 2007 07:08:27 -0400
List-post: <>
Cheat et al,

A year ago we were hoisting assembled sections of AB105 into place at NR4M 
using a special gin pole that Paul K4JA had crafted. Working at the 80 foot 
level, a little too much lateral pull was placed on the hoisted tower 
section by the ground crew to keep it from getting hung up on the existing 
tower. The gin pole had been attached to the top foot and a half of the top 
existing vertical member. That vertical member folded over just below the 
bottom of the gin pole. Fortunately no-one was seriously hurt and we've 
since gone to building 105 piece by piece or assembling large sections and 
craning them into place.

Since then we've rather wondered if the gin pole had been attached to the 
next vertical member down (that had diagonals attached) whether the diagonal 
would have proved enough additional support to keep it from folding over. 
The reason for attaching as we did was to get the most use of the 10 feet of 
gin pole.

When you consider using a gin pole, due consideration must be given not only 
to how strong the pole itself is, but to how strong the attachment point on 
the tower is. Obviously the forces at play when using a gin pole increase as 
the length of the pole is increased, especially as the lateral forces on the 
gin pole increase.

For as easy as it is to build 25, 45 and 55 tower using proper gin poles, I 
don't understand why one would want to complicate things by assembling pairs 
of sections and working with the increased weight and need for additional 
vertical lift.

Be careful up there!

73de Larry K7SV


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