This is interesting discussion. Consider the following
simple setup:
Take a standard gin pole, run the rope through the pulley,
but instead of attaching the rope directly to the load,
run the rope through a second free pulley, which is attached to
the load. Now run the end of the rope up to the top of the
gin pole, and firmly secure it to the top of the gin pole mast
somehow. Now attempt to lift a 100# mast.
The 100# is supported by two ropes, so the tension on the rope
is 50#. Tension on the rope is constant in a pulley system, so
the people on the ground are exerting another 50#
downward tension, and the resultant downward force on the gin
pole is 150#, instead of 200#, which it would have been if the
second pulley had not been used. Additionally, the people on
the ground only have to exert half the force. It sounds like
a pretty slick idea to me, and it only takes one additional
$10 pulley, and a longer rope! The rope has to be longer by
the height of the tower plus the length of the gin pole, but it
needs to be only half as strong as the rope without the second
pulley.
Dave Hachadorian, K6LL
Yuma, AZ
K6LL@juno.com
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