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[Fwd: [TowerTalk] Ginpole for 20 foot sections]

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Subject: [Fwd: [TowerTalk] Ginpole for 20 foot sections]
From: (Stan or Patricia Griffiths)
Date: Wed, 13 Jun 2001 17:40:03 -0700
I thought I had sent this message to the reflector but apparently not . . .

Stan or Patricia Griffiths wrote:

> Yes, I am ABSOLUTELY sure.  Like I said, I set up a demonstration to prove it,
> showed it at a Willamette Valley DX Club meeting with the help of W7RR and
> convinced each and everyone present that it works exactly as described.
> What I did was set up a 6 foot vertical mast made of 1 inch diameter aluminum
> tubing.  Next, I rigged it with a small single pully at the top and with a
> spring scales inserted between the pully and the top of the mast showing the
> downward force on the pully which is the same as the load on the mast.  Next, 
> I
> installed a known weight of 15 pounds (measured by the same spring scale 
> earlier
> in the demonstration) on the load rope.  Next, I took up slack on the "pull"
> rope and when the weight lifted off the floor, W7RR read the scale.  It said 
> 30
> pounds.  Why 30 pounds and not 15 pounds?  Because there are TWO ropes pulling
> down on the pully, one attached to the load and the other one attached to the
> hands of the person raising the load.  Both of these ropes (technically, it is
> only one rope but it has the same effect as if it were two separate ropes, 
> each
> attached to the pully, in terms of applying load to the pully and mast) have 
> 15
> pounds of tension each and pulling in the same direction (down) and all of 
> that
> load (15 pounds EACH) is supported by the mast and pully.
> What I did then was make a small block and tackle with a 3:1 advantage and put
> it in place of the single pully.  I again raised the load off the floor and 
> W7RR
> read the scale in series with the pully.  I now read 20 pounds instead of 30
> pounds or 2/3 of the first number.  Now there are 3 strands of rope holding 
> the
> weight (15 pounds) so the tension in the rope is 5 pounds instead of 15 pounds
> and the tension in the pull rope is also 5 pounds, since it is the same
> continuous rope.  So now there is effectively FOUR ropes pulling down on the
> pully (and mast) but each one only has a tension of 5 pounds each (total 20
> pounds) instead of TWO ropes with a tension of 15 pounds each (total 30 
> pounds).
> This REALLY works.  If you STILL don't believe it, you can always rig this at
> home and TRY it yourself.  It is not rocket science.  Also, it is not
> intuitively obvious that it works which is why there are so many 
> non-believers.
> You certainly can't deny that it is a VERY IMPORTANT concept and reducing the
> load on the gin pole by 33% could save your neck when you are lifting that 250
> pound long steel mast . . . isn't it worth checking it out?
> I have actually thought about making my demo kit available as a traveling
> program but there is nothing in it you can't get at the local hardware store 
> for
> a couple of bucks.
> You know, when we hashed this out last time here on towertalk, I went away 
> with
> the ugly feeling there were still a lot of non-believers out there and I had
> failed miserably to get this VERY IMPORTANT point across.  I hope I made it 
> this
> time.  The bottom line is that you can try it yourself . . . so I don't want 
> to
> hear from any nonbelievers who have not actually rigged this up and made the
> measurements themselves . . .  this means I should not get ANY nonbeliever 
> email
> on this since, as soon as you try it, you will become a believer . . . 
> becauses
> it is absolutely TRUE.
> Stan
> wrote:
> > In a message dated 6/12/01 11:45:50 PM Pacific Daylight Time,
> > 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.
> >
> > Cheers,   Steve    K7LXC
> > Tower Tech

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