NO, NO, NO . . . DON'T THINK ABOUT IT. MEASURE IT YOURSELF AND YOU WILL SEE
THAT JIM IS
EXACTLY RIGHT.
If you think I am shouting, you're right. Being polite and subtle doesn't seem
to work . .
.
Obviously, you are a non-believer who has NOT made the measuremnts . . .
Stan
w7ni@easystreet.com
Jim wrote:
> Dave,
>
> I'm not buying that. It sounds logical at first but think about it. To pull
> 300 lbs
> up, it takes 300 lbs of pull, and since the upper pulley arrangement is
> actually going
> to be located on the gin pole, guess what? The 300 lbs of pull is going
> right into the
> gin pole. Sorry if I'm not real clear but I know what I mean! HiHi.
>
> 73
> Jim WB6YAW
>
> David Robbins wrote:
>
> > of course the lifting rope load remains the same, but the force required on
> > the
> > pulling end decreases so the total load on the gin pole does get reduced.
> >
> > for example, with a standard gin pole lifting 300lbs at the top of the pole
> > you
> > have a 300lb load plus 300lb of pull from the other side giving you a worst
> > case
> > 600lb force on the gin pole (static load, some more is required to get
> > things
> > moving, overcome friction, etc).
> >
> > with a 3:1 advantage pulley system you still have the 300lb load on one
> > side,
> > but the rope pulling down on the other side is only adding 100lbs of force
> > to
> > the pole, so the total is now 400lb. which of course is a 1/3 reduction
> > from
> > the 600lb you started with.... note the 3:1 and the 1/3 reduction is just
> > how it
> > works out. with a 2:1 advantage you only reduce the total load from 600 to
> > 450lbs of a reduction of only 1/4 of the load... and taken to extreme, with
> > an
> > infinite mechanical advantage you still have 300lbs of load so you only
> > reduce
> > the total load on the pole by 1/2, the lowest you can get.
> >
> > another advantage of a pulley system like that is you can use a lighter
> > weight
> > rope since each pass of it between the pulleys divides the load up. so for
> > a
> > 3:1 system with a 300lb load you only need a rope that can handle 100lb of
> > tension instead of 300lb... but of course you have to pull 3x more of it to
> > lift
> > the same distance.
> >
> > K7LXC@aol.com wrote:
> > >
> > > In a message dated 6/12/01 11:45:50 PM Pacific Daylight Time,
> > > w7ni@easystreet.com writes:
> > >
> > > > A 3:1 mechanical advantage block and tackle system does, indeed,
> > > > relieve
> > > > about 1/3 of the load on the gin pole, in addition to reducing the
> > > > number
> > > of
> > > > bodies required on the pull rope.
> > >
> > > You sure? Isn't a hundred-pound load going to weigh 100 pounds no
> > > matter
> > > how the block and tackle are set up? The load effort on the end of the
> > > rope
> > > will be reduced but the dead weight of the load stays the same. You still
> > > need a suitable ginpole.
> > >
> >
> > --
> > David Robbins K1TTT
> > e-mail: mailto://k1ttt@berkshire.net
> > web: http://www.k1ttt.net
> > AR-Cluster node: 145.69MHz or telnet://k1ttt.net
> >
> > List Sponsor: Are you thinking about installing a tower this summer? Call us
> > for information on our fabulous Trylon Titan self-supporting towers - up to
> > 96-feet for less than $2000! at 888-833-3104 <A
> > HREF="http://www.ChampionRadio.com";>
> > www.ChampionRadio.com</A>
> >
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