[TowerTalk] Ginpole for 20 foot sections

Kurt Andress K7NV@contesting.com
Thu, 14 Jun 2001 13:00:24 -0700


n4kg@juno.com 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
advantage.

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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