I think I recall doing this exact experiment in high-school physics with a
spring scale substituted for the fixed attachment point. It was a long time
ago, but I think we showed that the load on the top pulley of the gin pole
is exactly the same whether the mechanical advantage is 1 or 6, and that it
was equal to G x the mass of the weight. Actually, in a real mechanical
system it'd be a tad higher, because you have to add in the weight of the
pulleys and additional rope, and when the system is moving some small part
of the force pulling on the rope is transferred to the anchor point by
mechanical friction inside the pulley.
Am I remembering correctly? Is there anyone out there who has done this
more recently who *will* share his results (Dave, this means you)?
Kurt's point about the off-axis forces exerted by a practical load is much
more to the point than all this discussion about the static load exactly in
line with the gin pole, anyway. Imagine what kind of force, exactly
on-axis, it would take to collapse a 2-inch aluminum gin pole! Imagine how
spectacular the event would be when a gin pole finally failed in pure
compression!
73, Pete Smith N4ZR
n4zr@contesting.com
Loud is.
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