On Wed, 13 June 2001, n4kg@juno.com wrote:
> How is this 2:1 mechanical advantage achieved?
>
> Scenario 1 - End of rope is attached to the frame
> of the top pulley. Rope runs down to Second pulley
> with hook at load. Rope then runs up and through
> the TOP pulley. Force in each vertical run of the
> rope is 150 lbs. 450 lbs on top hook as proposed.
>
> This is NOT how a gin pole is configured.
>
> In a block and tackle, one end of the pull rope
> is attached to one of the pulleys. The LOAD is
> attached to one of the end hooks. Multiple
> pulleys can be mounted co-axially.
Why is this NOT how a gin pole is configured? Even if one ties the fixed end of
the rope to the tower (say when lifting a beam or rotator that need not rise
above the tower top), one has not materially changed the configuration and
still achieves 2:1 with a movable pulley at the load. BTDT.
A discussion that was, until recently, about the total load on a gin pole seems
to have devolved into a semantical discussion of just what constitutes a "block
and tackle" and the acceptable uses of a gin pole.
I've seen the term "block and tackle" used for various combinations of fixed
and movable pulleys (when achieving some mechanical advantage).
73 Mike N2MG
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