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[TowerTalk] Ginpole for 20 foot sections

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Subject: [TowerTalk] Ginpole for 20 foot sections
From: (Kurt Andress)
Date: Thu, 14 Jun 2001 13:00:24 -0700 wrote:
> A gin pole for heavy loads can be configured by using
> a block and tackle BETWEEN the SUPPORT and the LOAD
> where there are MULTIPLE pulleys and one end of the rope
> is connected to one of the blocks.
Hi Tom and all,

Remember, when evaluating the true effect of the "reduced load" on the
ginpole, that if the load is not directly below the pole, but creates a
small angle between the line and the pole, that the pole is not going to
realize any significant reduction in stress from the use of the mechanical

Put a 10 degree angle between the pole and the load line, look at the
bending stress at the base of the pole, and it will become apparent. A 12'
Rohn ginpole lifting 250 lbs realizes a 1.3% reduction in stress when the
mechanical advantage (between load and pole) is changed from 1:1 to 4:1. 

The mechanical advantage should be viewed as an aid to those lifting the
load, but not much help for the pole.

73, Kurt, K7NV

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