Ron,
Your point is valid ONLY if the block and tackle is between the
support and the load.
If the block and tackle is between the puller and the gin pole rope,
the tension in the puller's rope is reduced by the mechanical advantage
but the load on the GIN pole remains at 2X the weight of the Load
plus friction losses.
Broad statements without clarification can be VERY misleading
and incorrect if applied universally. This is were accidents happen
and people get hurt.
de Tom N4KG
On Thu, 14 Jun 2001 "Ron D. Rossi" <rrossi@btv.ibm.com> writes:
>
> Regardless of any of the tensions on the ropes used in lifting a
> weight the only NET forces acting on the system (ignoring friction)
> are the weight of the object being lifted PLUS the downward force
>exerted to lift it.
>
> Reduce the force required to lift the load and that contribution to
> the NET is reduced.
>
> --
> 73 es God Bless de KK1L...ron (kk1l@arrl.net) <><
> QTH: Jericho, Vermont
> My page: http://www.qsl.net/kk1l
>
> >>>n4kg@juno.com said:
> > 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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>
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