I agree with this scenario which is an example of my
statement that the mechanical advantage equals the
number of segments between the support and the load.
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.
For the standard Rohn Gin pole this is NOT how it works
and the argument proposed by some here that a mechanical
advantage between the puller and a standard single pulley
on the gin pole provides a load readuction for the gin pole is
FALSE.
My arguments ASSUMED a typical Rohn Gin Pole with
a single pulley at the top. Yes, a multi-pulley system
can be configured to provide a mechanical advantage.
We really must keep our apples and oranges separate :-)
Sorry if there was some confusion between these two
different types of pulley arrangements.
Tom N4KG
On Wed, 13 Jun 2001 David Robbins <k1ttt@berkshire.net> writes:
> i have not had a need to do it, but a 2:1 arrangement would also be
> easy to do.
> all you need to do is tie one end of the rope to the top of the
> pole, run
> through a single moving pulley where you attach the load, then go
> through the
> normal gin pole pulley and back to the ground. of course it takes
> 50% more rope
> than just going up and over the gin pole pulley. why not DOUBLE the
> rope you
> may say??? well, think about it... in the normal setup you go up the
> tower and
> back down to the load. with a 2:1 setup like this you go up the
> tower, down to
> the moving pulley, and then back up to the top... so you only have
> one extra
> length going up the tower... each increment in mechanical advantage
> adds one
> more length equal to the max lift height to the length of rope
> needed. so a 3:1
> advantage only needs 2x the rope as the 1:1 normal use of the gin
> pole.
>
> "Guy Olinger, K2AV" wrote:
> >
> > See other post on how advantage achieved.
> >
> > > This is NOT how a gin pole is configured.
> >
> > A gin pole is just a device to give an attachment opportunity high
> enough above already
> >accomplished structure to allow fixing various lifting devices to
> control both vertical and
> >horizontal forces on the next section for easy attachment. It
> doesn't imply any particular lifting
> >arrangement, though some may be manufactured with a particular
> device integral.
> >
> > Other than a single pulley, the top hook of a 4:1 block and tackle
> setup is another device that can
> >be attached to the top of a gin pole. I've seen an electric winch
> fitted to a gin pole.
>
>
> --
> David Robbins K1TTT
> e-mail: mailto://k1ttt@berkshire.net
> web: http://www.k1ttt.net
> AR-Cluster node: 145.69MHz or telnet://k1ttt.net
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