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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